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  Subjects -> ENGINEERING (Total: 2449 journals)
    - CHEMICAL ENGINEERING (208 journals)
    - CIVIL ENGINEERING (208 journals)
    - ELECTRICAL ENGINEERING (116 journals)
    - ENGINEERING (1288 journals)
    - ENGINEERING MECHANICS AND MATERIALS (394 journals)
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CIVIL ENGINEERING (208 journals)                  1 2 | Last

Showing 1 - 200 of 208 Journals sorted alphabetically
ACI Structural Journal     Full-text available via subscription   (Followers: 20)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 3)
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 3)
Advances in Civil Engineering     Open Access   (Followers: 41)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 33)
Agregat     Open Access   (Followers: 1)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 35)
Architectural Engineering     Open Access   (Followers: 5)
Architecture and Engineering     Open Access  
Architecture, Civil Engineering, Environment     Open Access  
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 3)
Archives of Civil Engineering     Open Access   (Followers: 12)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 2)
ATBU Journal of Environmental Technology     Open Access   (Followers: 4)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 7)
Baltic Journal of Road and Bridge Engineering     Open Access   (Followers: 1)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 10)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 2)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 3)
Berkeley Planning Journal     Open Access   (Followers: 5)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 14)
Building & Management     Open Access   (Followers: 2)
Building and Environment     Hybrid Journal   (Followers: 15)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 15)
Bulletin of Pridniprovsk State Academy of Civil Engineering and Architecture     Open Access   (Followers: 6)
Canadian Journal of Civil Engineering     Hybrid Journal   (Followers: 13)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 6)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 11)
Case Studies in Structural Engineering     Open Access   (Followers: 9)
Cement and Concrete Composites     Hybrid Journal   (Followers: 20)
Challenge Journal of Concrete Research Letters     Open Access   (Followers: 3)
Challenge Journal of Structural Mechanics     Open Access   (Followers: 5)
Change Over Time     Full-text available via subscription   (Followers: 2)
Civil and Environmental Engineering     Open Access   (Followers: 8)
Civil and Environmental Engineering Reports     Open Access   (Followers: 8)
Civil and Environmental Research     Open Access   (Followers: 17)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Architecture     Open Access   (Followers: 23)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 12)
Civil Engineering Dimension     Open Access   (Followers: 11)
Civil Engineering Infrastructures Journal     Open Access   (Followers: 1)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 290)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 11)
Computers & Structures     Hybrid Journal   (Followers: 37)
Concrete Research Letters     Open Access   (Followers: 7)
Construction Economics and Building     Open Access   (Followers: 4)
Construction Engineering     Open Access   (Followers: 11)
Construction Management and Economics     Hybrid Journal   (Followers: 21)
Constructive Approximation     Hybrid Journal  
Curved and Layered Structures     Open Access   (Followers: 3)
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal   (Followers: 1)
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 17)
Enfoque UTE     Open Access   (Followers: 4)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 7)
Engineering Structures     Hybrid Journal   (Followers: 13)
Engineering Structures and Technologies     Open Access   (Followers: 2)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 10)
Environmental Geotechnics     Hybrid Journal   (Followers: 5)
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 10)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 19)
Frontiers in Built Environment     Open Access   (Followers: 1)
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Geomaterials     Open Access   (Followers: 3)
Geosystem Engineering     Hybrid Journal   (Followers: 2)
Geotechnik     Hybrid Journal   (Followers: 4)
Géotechnique Letters     Hybrid Journal   (Followers: 8)
GISAP : Technical Sciences, Construction and Architecture     Open Access  
HBRC Journal     Open Access   (Followers: 2)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal  
Indonesian Journal of Urban and Environmental Technology     Open Access  
Indoor and Built Environment     Hybrid Journal   (Followers: 3)
Infrastructure Asset Management     Hybrid Journal   (Followers: 3)
Infrastructures     Open Access  
Ingenio Magno     Open Access   (Followers: 1)
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 30)
International Journal for Service Learning in Engineering     Open Access  
International Journal of 3-D Information Modeling     Full-text available via subscription   (Followers: 3)
International Journal of Advanced Structural Engineering     Open Access   (Followers: 17)
International Journal of Civil, Mechanical and Energy Science     Open Access   (Followers: 2)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 15)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 2)
International Journal of Construction Engineering and Management     Open Access   (Followers: 10)
International Journal of Engineering and Geosciences     Open Access  
International Journal of Geo-Engineering     Open Access   (Followers: 3)
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription   (Followers: 4)
International Journal of Masonry Research and Innovation     Hybrid Journal   (Followers: 1)
International Journal of Pavement Research and Technology     Open Access   (Followers: 6)
International Journal of Protective Structures     Hybrid Journal   (Followers: 6)
International Journal of Steel Structures     Hybrid Journal   (Followers: 2)
International Journal of Structural Engineering     Hybrid Journal   (Followers: 9)
International Journal of Structural Integrity     Hybrid Journal   (Followers: 2)
International Journal of Structural Stability and Dynamics     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Built Environment     Open Access   (Followers: 5)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 8)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 7)
International Journal Sustainable Construction & Design     Open Access   (Followers: 2)
Journal of Applied Research in Water and Wastewater     Open Access   (Followers: 1)
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 13)
Journal of Building Engineering     Hybrid Journal   (Followers: 2)
Journal of Building Materials and Structures     Open Access   (Followers: 2)
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 6)
Journal of Civil Engineering     Open Access  
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 15)
Journal of Civil Engineering and Management     Open Access   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 9)
Journal of Civil Engineering Research     Open Access   (Followers: 7)
Journal of Civil Engineering, Science and Technology     Open Access   (Followers: 1)
Journal of Civil Society     Hybrid Journal   (Followers: 5)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 4)
Journal of Composites     Open Access   (Followers: 78)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 13)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 23)
Journal of Construction Engineering     Open Access   (Followers: 9)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 17)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 6)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 4)
Journal of Fluids and Structures     Hybrid Journal   (Followers: 6)
Journal of Frontiers in Construction Engineering     Open Access   (Followers: 2)
Journal of Green Building     Full-text available via subscription   (Followers: 10)
Journal of Highway and Transportation Research and Development (English Edition)     Full-text available via subscription   (Followers: 14)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 19)
Journal of Legal Affairs and Dispute Resolution in Engineering and Construction     Full-text available via subscription   (Followers: 5)
Journal of Marine Science and Engineering     Open Access   (Followers: 1)
Journal of Materials and Engineering Structures     Open Access   (Followers: 5)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 8)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 9)
Journal of Performance of Constructed Facilities     Full-text available via subscription   (Followers: 3)
Journal of Pipeline Systems Engineering and Practice     Full-text available via subscription   (Followers: 6)
Journal of Rehabilitation in Civil Engineering     Open Access   (Followers: 3)
Journal of Solid Waste Technology and Management     Full-text available via subscription   (Followers: 1)
Journal of Structural Engineering     Full-text available via subscription   (Followers: 35)
Journal of Structural Fire Engineering     Full-text available via subscription   (Followers: 6)
Journal of Structural Mechanics     Open Access   (Followers: 1)
Journal of Structures     Open Access   (Followers: 4)
Journal of Sustainable Architecture and Civil Engineering     Open Access   (Followers: 3)
Journal of Sustainable Design and Applied Research in Innovative Engineering of the Built Environment     Open Access   (Followers: 1)
Journal of the Civil Engineering Forum     Open Access  
Journal of the South African Institution of Civil Engineering     Open Access   (Followers: 2)
Journal of Water and Environmental Nanotechnology     Open Access  
Journal of Water and Wastewater / Ab va Fazilab     Open Access  
Jurnal Spektran     Open Access   (Followers: 1)
Jurnal Teknik Sipil     Open Access  
Jurnal Teknik Sipil dan Perencanaan     Open Access   (Followers: 1)
Konstruksia     Open Access  
KSCE Journal of Civil Engineering     Hybrid Journal   (Followers: 2)
Latin American Journal of Solids and Structures     Open Access   (Followers: 4)
Materiales de Construcción     Open Access   (Followers: 1)
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 4)
Media Komunikasi Teknik Sipil     Open Access  
Mokslas – Lietuvos ateitis / Science – Future of Lithuania     Open Access  
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 15)
npj Materials Degradation     Open Access  
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 9)
Periodica Polytechnica Civil Engineering     Open Access  
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 4)
Practice Periodical on Structural Design and Construction     Full-text available via subscription   (Followers: 3)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Civil Engineers - Civil Engineering     Hybrid Journal   (Followers: 14)
Proceedings of the Institution of Civil Engineers - Management, Procurement and Law     Hybrid Journal   (Followers: 10)
Proceedings of the Institution of Civil Engineers - Municipal Engineer     Hybrid Journal   (Followers: 2)
Proceedings of the Institution of Civil Engineers - Structures and Buildings     Hybrid Journal   (Followers: 3)
Promet : Traffic &Transportation     Open Access  
Random Structures and Algorithms     Hybrid Journal   (Followers: 5)
Recent Trends In Civil Engineering & Technology     Full-text available via subscription   (Followers: 5)
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 6)
Resilience     Open Access   (Followers: 1)
Revista IBRACON de Estruturas e Materiais     Open Access   (Followers: 1)
Revista Sul-Americana de Engenharia Estrutural     Open Access  
Road Materials and Pavement Design     Hybrid Journal   (Followers: 11)
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 5)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 61)
Selected Scientific Papers - Journal of Civil Engineering     Open Access   (Followers: 3)
Slovak Journal of Civil Engineering     Open Access   (Followers: 2)
Soils and foundations     Full-text available via subscription   (Followers: 5)
Steel Construction - Design and Research     Hybrid Journal   (Followers: 3)
Structural and Multidisciplinary Optimization     Hybrid Journal   (Followers: 11)
Structural Concrete     Hybrid Journal   (Followers: 11)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 8)
Structural Engineering International     Full-text available via subscription   (Followers: 11)
Structural Mechanics of Engineering Constructions and Buildings     Open Access   (Followers: 1)
Structural Safety     Hybrid Journal   (Followers: 6)
Structural Survey     Hybrid Journal  
Structure     Full-text available via subscription   (Followers: 24)
Structure and Infrastructure Engineering: Maintenance, Management, Life-Cycle Design and Performance     Hybrid Journal   (Followers: 12)
Structures     Hybrid Journal   (Followers: 1)
Study of Civil Engineering and Architecture     Open Access   (Followers: 10)
Superlattices and Microstructures     Hybrid Journal   (Followers: 2)
Surface Innovations     Hybrid Journal  
Technical Report Civil and Architectural Engineering     Open Access   (Followers: 1)
Teknik     Open Access  
Territorium : Revista Portuguesa de riscos, prevenção e segurança     Open Access  
The IES Journal Part A: Civil & Structural Engineering     Hybrid Journal   (Followers: 6)

        1 2 | Last

Journal Cover
Cement and Concrete Composites
Journal Prestige (SJR): 3.146
Citation Impact (citeScore): 6
Number of Followers: 20  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0958-9465
Published by Elsevier Homepage  [3162 journals]
  • Reactivity and performance of dry granulation blast furnace slag cement
    • Abstract: Publication date: Available online 13 October 2018Source: Cement and Concrete CompositesAuthor(s): Junxiang Liu, Qingbo Yu, Zongliang Zuo, Fan Yang, Zhicheng Han, Qin Qin Dry granulation, as a new process for molten blast furnace slag treatment, is an attractive alternative to water quenching. In this study, the performance of dry granulation slag in slag cement blends was investigated. The results demonstrated that the early strength for dry granulation slag cement mortar was too low, which is less than 50% of the strength for the cement clinker. After 28 days, the compressive strength for dry granulation slag cement mortar containing 35 min-milled slag powder was higher than that for cement clinker. With a decrease in cement/slag ratio, the compressive strength for dry granulation slag cement mortar decreased, and then increased, reaching 96.4% of the compressive strength for dry granulation slag cement mortar made with cement/slag ratio of 2:1. Although the content of cement clinker decreased, there was enough Ca(OH)2 to activate dry granulation slag particles to form compact CSH structure when the cement/slag ratio was 1.5:1.
       
  • Strain rate-dependent compressive behavior and failure mechanism of
           cementitious syntactic foams
    • Abstract: Publication date: Available online 13 October 2018Source: Cement and Concrete CompositesAuthor(s): Halim Kerim Bas, Weihua Jin, Nikhil Gupta, Dung D. Luong The present work was focused on studying the strain rate sensitivity of cementitious syntactic foams (CSF), which are particulate composites reinforced with hollow glass microspheres (HMG). Different density CSFs (1.31–1.74 g/cm3) with different volume fractions (20–40%) of HGMs were tested with a split-Hopkinson pressure bar setup. The true particle densities of the HGMs were in the range of 0.38–0.60 g/cm3. In addition, the macro- and micro-scale failure mechanisms were investigated with high-speed camera imaging, micro-CT scanning, and electron microscopy. The results showed that both the CSFs and the baseline material (control sample), which is the cement paste matrix of the CSFs, showed strain rate sensitivity in mechanical properties in the 102–103 s−1 strain rate range. CSFs had relatively lower strain rate sensitivity in comparison to the matrix material. In the same range of strain rate, both the CSFs and the control sample showed significant changes in their macro and micro failure mechanisms depending on their age, composition and loading rate. The level of damage at the peak load for the high strain rate was higher in comparison to the same materials tested under quasi-static loading conditions for CSFs and the cement matrix.
       
  • Water absorption and electrical resistivity of concrete with recycled
           concrete aggregates and fly ash
    • Abstract: Publication date: Available online 12 October 2018Source: Cement and Concrete CompositesAuthor(s): Rawaz Kurda, Jorge de Brito, José D. Silvestre This paper presents a literature review and experimental results on the effect of high incorporation levels of fly ash (FA) and recycled concrete aggregates (RCA), individually and jointly, on the pore system of concrete that remarkably influences its durability. For that purpose, apart from an extensive literature review, three tests were performed, including electrical resistivity (ER) test, which indirectly measures the interconnected porosity of concrete, and water absorption (WA) by capillarity and immersion tests that both depend on the pores number and size but in a different way. A comparison between the experimental results and the literature is also presented to show the main findings and the research needs. The results show that WA increases and ER decreases with increasing incorporation level of RCA, and the opposite occurs with the addition of FA for both tests. The reduction percentage of WA was higher in mixes with both RCA and FA when compared to the sum of reductions in mixes with only RCA or FA. Thus, it is advisable to produce concrete with both mentioned non-traditional materials in terms of WA and ER of concrete. In addition, the benefit of incorporating of FA and RCA in concrete increased even more when superplasticizers was used.
       
  • Scale-linking model of self-healing and stiffness recovery in Engineered
           Cementitious Composites (ECC)
    • Abstract: Publication date: Available online 11 October 2018Source: Cement and Concrete CompositesAuthor(s): Hui Ma, Emily Herbert, Motohiro Ohno, Victor C. Li Micro-crack damage in Engineered Cementitious Composites (ECC) has demonstrated self-repairing capacity when exposed to wetting-drying cycles. Previous studies qualitatively relate composite stiffness recovery to crack width. There is a need to develop a more quantitative understanding of the relationship between the magnitude of self-healing and imposed strain in ECC. An analytic model that links the stiffness recovery of a single crack in ECC (meso-scale) to that of an ECC loaded to multiple micro-crack damage (macro-scale) was investigated in this study. The objective of this research is to develop this theoretical scale-linking model and validate it with experimental data. It is found that the proposed scale-linking model successfully predicted the composite stiffness recovery at any strain, based on known macro-scale crack patterns and meso-scale self-healing behavior. It is concluded that the new model captures the essence of self-healing behavior in ECC. The model clarifies the pathway for designing ECC with robust self-healing behavior.
       
  • Characterization of coal bio ash from wood pellets and low-alkali coal fly
           ash and use as partial cement replacement in mortar
    • Abstract: Publication date: Available online 10 October 2018Source: Cement and Concrete CompositesAuthor(s): Nina M. Sigvardsen, Lisbeth M. Ottosen Coal is increasingly replaced by biomass at the power plants. This results in new types of fly ashes, e.g. coal bio ash (CBA), where low-alkali coal fly ash (CFA) is injected to the boiler furnace during incineration of wood pellets to hinder corrosion and maintain the necessary thermal efficiency of the fuel. An assessment of the properties of this new type of ash is important for the utilization of this resource. This study reports an investigation of the filler behaviour and pozzolanic activity of CBA, when used as a partial cement replacement. Traditional CFA was used for comparison and CBA was shown to be a more favourable substitute compared to CFA. This study has shown, that by injecting CFA into the boiler furnace, wood fly ash is transformed from being a waste by-product, into a usable resource in concrete production.
       
  • Void detection of cementitious grout composite with carbon nanotubes
    • Abstract: Publication date: Available online 8 October 2018Source: Cement and Concrete CompositesAuthor(s): Heeyoung Lee, Donghoon Kang, Jongwon Kim, Kyungwho Choi, Wonseok Chung Cement-based materials with carbon nanotubes (CNT) can show enhanced electrical and thermal characteristics. The purpose of this study is to detect voids in prestressed concrete (PC) grout. CNT cement grout specimens were fabricated and tested inside ducts. In this study, thermal imaging analysis and electrical resistance change analysis were performed for void detection. The test parameters were type and concentration of CNTs. The CNT types were multi-walled CNTs (MWCNTs) and single-walled CNTs (SWCNTs). The grout density was examined by measuring resistance changes within the cross-sectional zone. On thermal imaging analysis, the internal grout density was investigated using a thermal imager. In the electrical resistance change analysis, the grout density was studied by measuring the resistance value that can be changed due to the cross-sectional differences caused by voids.
       
  • Influence of the levels of replacement of portland cement by metakaolin
           and silica extracted from rice husk ash in the physical and mechanical
           characteristics of cement pastes
    • Abstract: Publication date: November 2018Source: Cement and Concrete Composites, Volume 94Author(s): Daiana Goes Cavalcante, Maria Gorett dos Santos Marques, João de Almeida Melo Filho, Raimundo Pereira de Vasconcelos The present research aimed to study the replacement of ordinary Portland cement (OPC) by metakaolin (MKL) and silica extracted from rice husk ashes (SRHA) in binary mixtures. To investigate the pozzolanic reactivity, thermal and microstructural analyses were performed in binary mixtures. To understand the physical effect of these blends, the packaging density was calculated according to the model of compressible packaging (MCP) and the compatibility/saturation levels of superplasticizers was studied with cementitious materials. Considering the substitution levels adopted, the results indicated that the paste with 40% of MKL provided a total consumption of calcium hydroxide to 28 days; however, the packaging density of the particles was reduced, while the compressive strength was maintained. The addition of 16% of SRHA in binary mixtures showed partial consumption of calcium hydroxide; nevertheless, this effect, together with the physical effect, led to an increase in the compressive strength for the same age.
       
  • Investigation of the rheology and strength of geopolymer mixtures for
           extrusion-based 3D printing
    • Abstract: Publication date: Available online 5 October 2018Source: Cement and Concrete CompositesAuthor(s): Biranchi Panda, Cise Unluer, Ming Jen Tan This study presents the development of fly ash-based geopolymer mixtures for 3D concrete printing. The influence of up to 10% ground granulated blast-furnace slag (GGBS) and silica fume (SF) inclusion within geopolymer blends cured under ambient conditions was investigated in terms of fresh and hardened properties. Evolution of yield stress and thixotropy of the mixtures at different resting times were evaluated. Mechanical performance of the 3D printed components was assessed via compressive strength measurements and compared with casted samples. SF demonstrated a significant influence on fresh properties (e.g. recovery of viscosity), whereas the use of GGBS led to higher early strength development within geopolymer systems. The feasibility of the 3D printing process, during which rheology was controlled, was evaluated by considering extrusion and shape retention parameters. The outcomes of this study led to the printing of a freeform 3D component, shedding light on the 3D printing of sustainable binder systems for various building components.
       
  • Analysis of correlation between real degradation data and a carbonation
           model for concrete structures
    • Abstract: Publication date: Available online 1 October 2018Source: Cement and Concrete CompositesAuthor(s): Pablo Benítez, Fernanda Rodrigues, Sudip Talukdar, Sergio Gavilán, Humberto Varum, Enrico Spacone Over the past few decades, climate change has become a significant problem, the ramifications of which are of concern around the world. Global warming is a long-term process caused by phenomena such as increased levels of carbon dioxide (CO2) concentration in the atmosphere, increases in rainfall, changes in relative humidity and changes in temperature. Thus, this will aggravate the degradation process of reinforced concrete (RC) structures, leading to the decrease of durability, safety and serviceability. Regarding the durability of concrete structures, carbonation-induced corrosion is definitely a significant and costly source of degradation, directly related to climatic parameters such as CO2, temperature and relative humidity. In Paraguay, the lack of control during the construction of buildings often leads to weak structures highly vulnerable to the attack of harmful external agents. Therefore, this paper seeks to provide an analysis of the correlation between real degradation data and a numerical carbonation model for concrete structures in the country. According to the Intergovernmental Panel on Climate Change (IPCC) reports, climatic parameters will increase in the future. For this reason, an analysis of the decreasing performance of these structures caused by climate change will be addressed in this paper. This research aims to choose the most accurate mathematical model that can be applied in Paraguay for the prediction of the service life of concrete structures subjected to carbonation-induced corrosion. For that purpose, parameters and variables of the selected model have been defined and subsequently validated through carbonation tests results carried out in a set of RC structures built in the country. The results of this paper should be considered as a first stage for the further formulation of maintenance strategies, which is highly necessary for Paraguay.
       
  • Capacitance-based stress self-sensing in cement paste without requiring
           any admixture
    • Abstract: Publication date: Available online 25 September 2018Source: Cement and Concrete CompositesAuthor(s): D.D.L. Chung, Yulin Wang This work reports capacitance-based stress self-sensing in cement paste without requiring any particular admixture (whatever type). The in-plane capacitance is measured between two coplanar electrodes (aluminum foil) adhered to the cement slab by double-sided adhesive tape. The capacitance decreases with increasing normal stress, whether the stress is purely compressive or flexural compressive, due to piezoelectricity. The capacitance decrease is completely reversible in the low-stress regime (normal stress up to 19 kPa), and partially reversible above this stress. The minimum normal stress change detected is 0.2 kPa, which, in case of flexure, corresponds to a flexural stress change of 8.5 kPa. The change in capacitance per unit normal stress change is up to 0.061 and 0.101 pF/kPa for purely compressive and flexural compressive loading, respectively; the value is higher in the low-stress regime, which gives superior linearity and reversibility. Low-stress sensing is relevant to pedestrian monitoring and room occupancy monitoring.
       
  • Research progress in advanced nanomechanical characterization of
           cement-based materials
    • Abstract: Publication date: Available online 25 September 2018Source: Cement and Concrete CompositesAuthor(s): Zhiyu Luo, Wengui Li, Kejin Wang, Surendra P. Shah Advanced characterization techniques have provided powerful tools for characterizations of materials at micro- and nano-scales worldwide. Although some overviews on nanomechanical characterizations of cement-based materials have been published, they have often focused on nanoindentation. Very limited reviews have been reported on the applications of modulus mapping, PeakForce quantitative nanomechanical mapping, and nanoscratch for researches on the micro and nanoscale compositions, structures and mechanical properties of modern cement-based materials. This paper is aimed at filling this blank. Based on an extensive literature review and authors’ own experience, the basic knowledge (e.g., general concepts, developments, and progresses) involved in the state-of-the-art nanomechanical characterization techniques have been systematically summarized in this paper. The critical issues (e.g., sample preparation procedures and requirements, measurements, and data analysis methods) of these techniques have been discussed in details. The applications of these techniques, especially their suitability for critical characterization of different scales of interfaces of cement-based materials are compared. Finally, the future perspectives of these nanomechanical characterization techniques are highlighted. It is expected that the outlook of this paper can help future researchers make scientific justification on selection of nanomechanical characterization methods and steer inquisitive readers into substantial details that may lead them to successful applications of these advanced techniques.
       
  • Size effect on splitting strength of hardened cement paste: Experimental
           and numerical study
    • Abstract: Publication date: Available online 25 September 2018Source: Cement and Concrete CompositesAuthor(s): Hongzhi Zhang, Branko Šavija, Yading Xu, Erik Schlangen Cement paste possesses complex microstructural features including defects/pores over a range of length-scales, from nanometres to millimetres in size. As a consequence, it exhibits different behaviour under loading depending on the size. In this work, cubic specimens in a size range of 1: 400 were produced and tested by a one-sided splitting concept using different testing instruments. The smallest specimen with size of 100 μm showed a high nominal splitting strength (18.81 MPa), an order of magnitude higher than the measured strength of 40 mm specimen (1.8 MPa). The test results were used to fit existing analytical size effect models. Although a good fit can be found for the existing size effect models, special attention should be given to the physical meaning behind these empirical parameters. In addition, a multi-scale modelling strategy that considers microstructural features at different length scales was adopted to model the trend of decreasing strength with specimen size observed in experiments. A good agreement between experimental observations and modelling results indicates that the featured material structure dominates the observed size effect on measured strength in the size range considered.
       
  • Improving the properties of recycled concrete aggregate with
           bio-deposition approach
    • Abstract: Publication date: Available online 25 September 2018Source: Cement and Concrete CompositesAuthor(s): Chun-Ran Wu, Ya-Guang Zhu, Xiao-Tong Zhang, Shi-Cong Kou In this study, a new bio-deposition approach was used to improve the properties of recycled concrete aggregate (RCA). The new bio-deposition approach is based on bacterially induced CaCO3 precipitation through respiration, which differs from the traditional bio-deposition treatment that produces CaCO3 by urea hydrolysis. The experimental investigation was conducted in two parts. First, the physical properties including water absorption, crushing value, and density of the bio-deposition-treated RCA were determined. Then, the workability, compressive strength, and water absorption of mortars prepared with treated RCA were determined. It was found that the bio-deposition-treated RCA had a higher density and lower crushing value and water absorption compared with untreated RCA. In case of mortar, not only the workability, but also the compressive strength improved and the water absorption decreased. Moreover, the effect of bio-deposition treatment on the RCA surface and interfacial transition zone was observed by SEM.Graphical abstractImage 1
       
  • Inline quantification of extrudability of cementitious materials for
           digital construction
    • Abstract: Publication date: Available online 24 September 2018Source: Cement and Concrete CompositesAuthor(s): V.N. Nerella, M. Näther, A. Iqbal, M. Butler, V. Mechtcherine Digital construction (DC) is a new process, and hence, no standard experimental methods for process-specific material characterization are as yet available. This article proposes a methodology for characterizing the extrudability of cement-based materials for DC, both quantitatively and inline. A 3D-printing test device was used for this purpose, which enabled the elimination of most artefacts in the characterization of materials. Unit extrusion energy UEE, defined as the energy consumed per extruded unit volume, was used as the measure of extrudability, lower UEE implying higher extrudability. The results obtained using the proposed approach were compared with results of a simple ram-extruder, slump-flow and viscometer tests. Two fine-grained concrete mixtures under investigation, one with ordinary sand and one with very fine sand, having respective yield stresses of 306.2 Pa and 642.7 Pa, were characterized. They showed a significant difference in their extrudability: the UEE needed in the case of material with finer sand was 1.62 times higher than that of the mixture with coarser sand. Interestingly, average ram extrusion force for the finer mixture was much lower than that of the coarser mix, underlining the challenges in material characterization and the need to consider the possible artefacts of various testing methods. Comparative analyses substantiated the significance of the proposed inline extrudability quantification method for DC.
       
  • The use of limestone to replace physical filler of quartz powder in UHPFRC
    • Abstract: Publication date: Available online 21 September 2018Source: Cement and Concrete CompositesAuthor(s): Sung-Hoon Kang, Yeonung Jeong, Kiang Hwee Tan, Juhyuk Moon One of the key features of ultra-high performance fiber-reinforced concrete (UHPFRC) is the inclusion of quartz powder (QP) as a filler to optimize granular packing. However, QP has not been compared against limestone powder (LP) in terms of the filler effects such as hydration characteristics, strength development, and autogenous shrinkage of the concrete. In this study, the effectiveness of LP as a filler is evaluated against that of QP in order to verify its potential for use as a new functional and human-friendly filler in UHPFRC. For this purpose, five types of fillers consisting of similar-sized QP and LP were designed while maintaining the same water-to-cement (w/c) and superplasticizer-to-cement (sppl/c) ratios. The early age strength increased by up to 12% depending on the LP content, due to the filler effect which accelerates cement hydration by providing a preferential surface for nucleation. However, the LP only acted as an inert filler, like QP; it did not participate in the formation of additional hydration products as confirmed by conducted analytical experiments. Although the 28-day strength was 4%–7% lower than that of the classical UHPFRC containing QP, the 91-day strength was 1%–4% higher. The early age shrinkage was also accelerated by the filler effect of the LP, but its duration was shortened in proportion to the LP content.
       
  • Effect of matrix shrinkage on rate sensitivity of the pullout response of
           smooth steel fibers in ultra-high-performance concrete
    • Abstract: Publication date: Available online 21 September 2018Source: Cement and Concrete CompositesAuthor(s): Jun Kil Park, Seung Hun Park, Dong Joo Kim The present study investigates the effects of matrix shrinkage on the rate-sensitive pullout resistance of smooth steel fibers in ultra-high-performance concrete (UHPC) by adding a shrinkage reducing agent (SRA) to the UHPC and varying the fiber inclination angle from 0° to 30°. The pullout resistance is sensitive to the loading rate, and this sensitivity is attributed to both matrix shrinkage and the fiber inclination angle. The addition of the SRA reduces the enhancements in both peak and equivalent bond strengths at higher loading rates. Moreover, the rate sensitivity of the equivalent bond strength increases as the fiber inclination angle increased.
       
  • Corrigendum to "Use of biochar as carbon sequestering additive in cement
           mortar" [Cement and Concrete composites, 110–129]
    • Abstract: Publication date: Available online 20 September 2018Source: Cement and Concrete CompositesAuthor(s): Souradeep Gupta, Harn Wei Kua, Chin Yang Low
       
  • Feasibility of using cellulose filaments as a viscosity modifying agent in
           self-consolidating concrete
    • Abstract: Publication date: Available online 19 September 2018Source: Cement and Concrete CompositesAuthor(s): Ousmane A. Hisseine, N. Basic, Ahmed F. Omran, Arezki Tagnit-Hamou Nanomodification of concrete represents one of the phenomenal leaps in concrete technology providing innovative tools for engineering cement composites with improved performance. In self-consolidating concrete (SCC), for instance, designing flowable–yet stable and robust–SCC mixtures requires an optimum balance between flowability and stability. This is conventionally achieved by optimizing the dosage of high range water reducing admixtures (HRWRA) indispensable for flowability while increasing the binder content or introducing viscosity modifying agents (VMA) necessary for stability. This study shows how cellulose filaments (CF)–a new type of nanocellulose materials – can be used as a novel tool for rheology modification and strength enhancement in SCC. CF was incorporated at concentrations ranging from 0.05 to 0.30% per binder mass in cement pastes and SCC. Rheological and mechanical properties of CF-systems were compared to those of plain systems and systems incorporating a commercially available VMA of Wealn gum type. Results showed that CF serve as VMA due to the buildup of flexible nanoscale CF-networks. The latter increased mixture viscosity–essential for stability–at low shear rates, and led to lower apparent viscosity at high shear rates owing to the streamlining of the flexible nanocellulose fibrils in the direction of flow, thereby exhibiting a shear thinning behavior. Furthermore, CF imparted improvement in mechanical performance of 12–26% in compression, splitting-tension, and flexure. Research outcomes are expected to contribute towards offering an alternative VMA with strength improvement potential while contributing towards the implementation of sustainable materials for concrete technology.
       
  • Use of nanosilica- or nanolime-additioned TEOS to consolidate cementitious
           materials in heritage structures: Physical and mechanical properties of
           mortars
    • Abstract: Publication date: Available online 18 September 2018Source: Cement and Concrete CompositesAuthor(s): A.M. Barberena-Fernández, M.T. Blanco-Varela, P.M. Carmona-Quiroga Tetra-ethoxysilane or tetraethyl orthosilicate (TEOS), also known as ethyl silicate, traditionally applied to consolidate stone, has recently begun to be used on Portland cement mortars and concrete with promising results. TEOS not only fills the pores in the substrate, but reacts with the cement favouring the precipitation of new C-S-H gels that densify and strengthen the materials. This study explored the effectiveness of new TEOS-based treatments bearing nanosilica (NS) or nanolime (NC) in and their compatibility with cement materials found in the built heritage, given the participation of the various products in the pozzolanic reactions that may induce additional C-S-H gel. The physical and hydric properties (mechanical strength, porosity, surface gloss and colour, water vapour permeability and low pressure water absorption) of a Portland cement mortar were determined before and after applying the consolidants. Ethyl silicate, alone or in conjunction with nanolime (4:1), proved to most effectively raise material strength and improve water repellence while conserving the original colour and gloss.
       
  • Steel fibre content and interconnection induced electrochemical corrosion
           of Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) subjected to
           critical marine environment
    • Abstract: Publication date: Available online 17 September 2018Source: Cement and Concrete CompositesAuthor(s): Qiulei Song, Rui Yu, Zhonghe Shui, Suduan Rao, Xinpeng Wang, Meijuan Sun, Chunyuan Jiang This study addresses the steel fibre content and interconnection induced electrochemical corrosion of Ultra-High Performance Fibre reinforced Concrete (UHPFRC) subjected to critical marine environment. The design basis of UHPFRC matrix is particle close packing principle, and then its fresh and hardened properties are investigated. After that, the AC-impedance spectroscopy is used to measure the electrical resistivity of the developed UHPFRC with different fibre amount. Furthermore, to clarify the distribution and interconnection of fibres in the hardened UHPFRC, an X-ray CT is employed. The obtained results show that with an increase of the added fibres amount, the rapid chloride migration (DRCM) and the electrical resistivity of the designed UHPFRC simultaneously decrease. When the added steel fibres amount reach 2% (vol.), a sharply decrease of the electrical resistivity can be observed, which implies that a steel fibre network formation could be obtained in the hardened UHPFRC.
       
  • Precipitated calcium hydroxide morphology in nanoparticle suspensions: An
           experimental and molecular dynamics study
    • Abstract: Publication date: Available online 15 September 2018Source: Cement and Concrete CompositesAuthor(s): Jinhui Tang, Tiejun Yang, Cheng Yu, Dongshuai Hou, Jiaping Liu The volume and morphology of calcium hydroxide (CH) precipitating from supersaturated solutions is monitored as a function of the concentration of either of two types of nanoparticles dispersed in the solution. The CH precipitated in the presence of sulfonated graphene nanosheets (SGN) had well-developed hexagonal platelet shapes, while that forming in the presence of cationic polyurethane nanospheres (PUC) tended to aggregate around the PUC and developed as spherulitic masses. The terminal CH platelet size in SGN suspensions was 8 μm; with increasing SGN dosage, the mean size increased to 23 μm. Taking into consideration complementary experimental measurements of isothermal adsorption and zeta potential, we speculate that calcium from the solution adsorbs on the surfaces of both SGN and PUC prior to nucleation of CH. Furthermore, molecular-scale mechanism indicated the interaction of Ca-Ocoo from PUC is stronger than Ca-Oso3 from SGN. Simultaneously the number of adsorbed calcium by PUC is roughly 3 times greater than for SGN, which is perfectly matched with the measured adsorption isotherm. Hopefully, this work can provide scientific guidance for hydration mechanism of cementitious materials in the presence of nanoparticles suspensions.
       
  • A study of the factors affecting the chloride maximum concentration in
           submerged concrete surface layers
    • Abstract: Publication date: Available online 13 September 2018Source: Cement and Concrete CompositesAuthor(s): Mahmoud Shakouri, David Trejo The chloride content analysis of the concrete exposed to chlorides often shows an initial increase in the concentration of chlorides to a maximum point within the first layers of the concrete surface followed by a gradual reduction in the chloride concentration at the lower depths. The review of the literature shows that very little attention has been given to the depth (Δx) at which the maximum chloride concentration (Cmax) occurs and its potential impacts on the numerical estimation of the apparent chloride diffusion coefficient (Da) and surface chloride concentration (Cs). This paper studies the influence of water-to-cement ratio, the concentration of chlorides in the environment, the time-to-exposure, and exposure duration on Cmax and Δx. Results show that water-to-cement ratio does not have a significant influence on Cmax. However, a significant increase in Δx is observed with an increase in the water-to-cement ratio. Results also show that while Cmax has time-variant properties and it increases nonlinearly with the exposure duration, exposure duration has minimal impacts on Δx. In addition, the time-to-exposure and the concentration of chlorides in the exposure environment are found to be significant factors influencing both Cmax and Δx. The findings of this study show that Δx has a significant impact on the numerical estimation of Da and Cs. Because Δx is not limited to the first millimeter of the concrete surface, as specified in ASTM C1556, care must be taken to exclude the layers that correspond to Δx.
       
  • Coupling statistical indentation and microscopy to evaluate
           micromechanical properties of materials: Application to viscoelastic
           behavior of irradiated mortars
    • Abstract: Publication date: Available online 13 September 2018Source: Cement and Concrete CompositesAuthor(s): Benoit Hilloulin, Maxime Robira, Ahmed Loukili In this work, an original method coupling statistical indentation and 3D microscope image analysis for heterogenous materials characterization is developed. Statistical microindentation test results performed on γ-irradiated and pristine mortar specimens are presented and analyzed using a clustering data mining technique. The outputs are compared with the phase identification from 3D image analysis to effectively reduce uncertainties in the material properties of one of the phases (cement paste). With respect to the effects of irradiations on cementitious materials, a significant increase of cement paste creep modulus and hardness, and a significant decrease of creep characteristic time, are highlighted after an exposition of 257 kGy at 8.5 Gy/min. Young's modulus of the cement paste is not significantly affected. These results confirm macroscopic concrete creep observations presented in previous studies fitted with dose-dependent logarithmic laws.
       
  • Electromagnetic and microwave absorbing properties of cementitious
           composite for 3D printing containing waste copper solids
    • Abstract: Publication date: Available online 12 September 2018Source: Cement and Concrete CompositesAuthor(s): Guowei Ma, Junbo Sun, Li Wang, Farhad Aslani, Miao Liu The increasing electromagnetic energy and multiple reflections of electromagnetic wave (EMW) produce various negative impact on the human body, equipment, information security and even military defense structures. In this study, a new electromagnetic wave EMW absorbing cementitious composites incorporating copper slag and powder was manufactured to accommodate the rapid development of 3D printing technology. The microscale morphology and chemical compositions of adopted absorbents were examined through scanning electron microscopy (SEM), energy dispersive spectrophotometry (EDS), and X-ray fluorescence (XRF). Electromagnetic parameters for copper slag and powder were measured in the range of 1–18 GHz. Then seven cementitious composites incorporating 0-30 wt% copper slag were firstly manufactured to access and evaluate the printable capability for extrusion-based printing. Five mass ratios (2–10 wt%) of copper powder were thereafter incorporated to the printability-optimized composite for the further enhancement of EMW absorption. Based on printable capacity, reflectivity tests using network analyzer over the 1–18 GHz range showed that the cementitious composite with 25 wt% copper slag and 6 wt% copper powder performs a favorable EMW absorption capacity with a 10.2 dB peak reflection loss value and a 3.48 GHz absorption band. In addition, the influence of macroscale configuration includes surfaces roughness and thickness on the EMW absorption are elaborated. The results provide experimental basis and reference for functionalizing and intelligenting the cementitious composite for application in infrastructures.
       
  • Effect of self-healing on fatigue of engineered cementitious composites
           (ECCs)
    • Abstract: Publication date: Available online 11 September 2018Source: Cement and Concrete CompositesAuthor(s): Jishen Qiu, Wei Li Aw-Yong, En-Hua Yang This paper presents a pioneer study on the effects of self-healing on the flexural fatigue performance of engineered cementitious composites (ECCs), a unique class of high-performance fiber-reinforced cementitious composites (HPFRCC) exhibiting tensile strain-hardening behavior with tensile strain capacity in excess of 3% with only 2% or less fiber content by volume. Results show that self-healing greatly extends the fatigue life of ECC because water/dry conditioning not only heals the matrix cracks but also recovers the fiber/matrix interfacial bonds which leads to increased fiber-bridging strength. ECC fatigue life increases with increasing fatigue pre-damage level because higher fatigue pre-loading cycles together with water/dry conditioning troubleshoots more potential failure planes. Repeated healing at lower pre-damage level is feasible and significantly extends fatigue life of ECC.
       
  • The durability of SHCC with alkali treated curaua fiber exposed to natural
           weathering
    • Abstract: Publication date: Available online 9 September 2018Source: Cement and Concrete CompositesAuthor(s): Bartosz Zukowski, Edson Rodrigo Fernandes dos Santos, Yasmim Gabriela dos Santos Mendonça, Flávio de Andrade Silva, Romildo Dias Toledo Filho This work presents the durability studies carried on strain-hardening cement-based composites reinforced with 4% of 40 mm alkali treated natural curaua fiber. The collected results present the influence of natural weathering periods of 6 and 12 months on the composite tensile properties. The strain-softening behavior of the composites exposed to weathering is motivated by the deterioration of fiber-matrix bond, observed by the reinforcement work indicators, pull-out tests and visual inspection of the interfacial transition zone. Matrix specimens exposed to natural weathering provided information on pH variation along the specimen's cross-section and the chemical analysis related the pH difference to the presence of amorphous carbonates, and free from calcium hydroxide as the matrix was designed. The deterioration of post-crack fiber reinforcement capacity, thus the absence of strain-hardening behavior, was caused by fiber-matrix void observed under microscope, which deteriorated the fiber-matrix connection.
       
  • Sorption isotherm and length change behavior of autoclaved aerated
           concrete
    • Abstract: Publication date: Available online 7 September 2018Source: Cement and Concrete CompositesAuthor(s): Nguyen Trong Lam, Shingo Asamoto, Kunio Matsui We conducted an experimental study on the sorption isotherm and length change behavior of autoclaved aerated concrete (AAC) in both desorption and adsorption processes. Three types of AAC with different bulk densities were used to study the length change mechanism. The experimental results show that the expansion of AAC during the adsorption process is mostly larger than the shrinkage in the first desorption process even though the water content in the adsorption process is lower. Interestingly, a clear expansion in the desorption process in a range of relative humidity (RH) from about 90% to 65% and a significant difference in the length change strain between the desorption and adsorption processes (shrinkage hysteresis) at high RH are observed. Based on these experimental results, we propose a model to represent the mechanism of the hygral length change of AAC, taking into account the changes in surface free energy of the solid surface and capillary tension. The model reasonably explains the significantly different length change behaviors of AACs with different pore structures.
       
  • Cradle-to-gate life cycle assessment of self-healing engineered
           cementitious composite with in-house developed (semi-)synthetic
           superabsorbent polymers
    • Abstract: Publication date: Available online 1 September 2018Source: Cement and Concrete CompositesAuthor(s): Philip Van den Heede, Arn Mignon, Guillaume Habert, Nele De Belie Autogenous crack healing can be stimulated with superabsorbent polymers (SAPs) in microfibre reinforced strain hardening engineered cementitious composite (ECC). Cradle-to-gate life cycle assessment was performed for self-healing ECC with 1 m% of three in-house developed (semi-)synthetic SAPs and 2 v% of polypropylene (PP) or polyvinyl alcohol (PVA) microfibre. Given the high cement content of this ECC (572 kg/m3), CML-IA impacts of 1 m% SAP range between 4 and 52% of the cement impact. The highest impacts were recorded for semi-synthetic SAPs, due to high energy use during drying. Use of PVA microfibre should be avoided since addition of 2 v% (= 26 kg/m3) can easily induce significantly higher CML-IA impacts than 572 kg cement. Nonetheless, if 100% crack healing efficiency could be assumed for slabs made of self-healing ECC, CML-IA impacts remain lower than those of a slab made of traditional concrete with inclusion of the required cover replacements within 100 years.
       
  • Durability of ultra-high performance concrete in tension under cold
           weather conditions
    • Abstract: Publication date: Available online 31 August 2018Source: Cement and Concrete CompositesAuthor(s): Zhidong Zhou, Pizhong Qiao Freezing and thawing resistance is a key characteristic for concrete materials in cold weather conditions. In this study, the tensile properties and elastic modulus of ultra-high performance concrete (UHPC) under accelerated freeze-thaw cycles are characterized. Six series of UHPC specimens are experimentally tested with a well-designed direct tension test (DTT) method to capture complete tensile stress-strain responses. Both the dynamic and wave moduli of elasticity of UHPC are measured at specific cycles using the standard impact test and self-designed “smart aggregate” technology, respectively. Long term freezing and thawing cyclic conditioning of UHPC samples results in reductions of elastic modulus, tensile strength, strain capacity, and energy absorption capacity. The tensile stress-strain curves of UHPC demonstrate distinct descending with increasing freeze-thaw cycles, particularly in the strain softening region. The energy-based approach is found to be more sensitive and effective than the elastic modulus-based approach when evaluating material deterioration over time and capturing accumulative material degradation subjected to rapidly-repeated freezing and thawing actions. As from the test results, UHPC is characterized as a very durable cementitious material, but it is not inherently unconquerable. Extended freezing and thawing actions can still lead to deterioration of the material, with respect to its elastic modulus, tensile strength, energy absorption capacity, etc. As demonstrated, the DTT method can be used to effectively characterize the long-term performance of UHPC in tension under cold weather conditions.
       
  • A layered-wise, composite modelling approach for fibre textile reinforced
           cementitious composites
    • Abstract: Publication date: Available online 30 August 2018Source: Cement and Concrete CompositesAuthor(s): M. El Kadi, T. Tysmans, S. Verbruggen, J. Vervloet, M. De Munck, J. Wastiels, D. Van Hemelrijck Textile Reinforced Cements (TRCs) offer an adequate alternative to more conventional building systems in construction due to their tunable and lightweight geometries. TRCs are currently either modelled by means of a discrete approach, where the textiles and the matrix are modelled separately, or by means of a smeared approach that averages the material's mechanical response over the cross-section.The research presented in this paper proposes a new, layered-wise approach of modelling where the through-thickness response of the composite is subdivided in different layers with individual mechanical properties. A tensile experimental campaign on different combinations of TRC layups, combining both glass and carbon fibre textiles, is performed and used as an input for the layered-wise numerical model. The model is then validated by comparison with flexural experiments performed on four different TRC layup combinations. The good agreement witnessed between the numerical predictions and the experimental results validates the layered-wise modelling approach proposed in this paper.
       
  • Effectiveness of preconditioning regimes for assessing water permeability
           of high performance concrete
    • Abstract: Publication date: Available online 29 August 2018Source: Cement and Concrete CompositesAuthor(s): Yaocheng Wang, Kai Yang, Adrian Long, Yun Bai, Sreejith Nanukuttan, Bryan Magee, Xiaohong Zhu, Zhilu Zhang, Changhui Yang, Muhammed Basheer Saturating high performance concrete (HPC) on site for assessing water permeability is a challenge. This paper reports a testing programme established to assess the reliability and efficiency of two field saturation approaches, viz. vacuum saturation and ponding. The water permeability test results after applying the vacuum saturation and ponding were compared with that after incremental immersion. It is found that ponding was unable to remove the influence of moisture, while vacuum saturation can achieve this for wet concretes. Although the influence of moisture can be removed for different HPCs with high initial moisture contents by using the vacuum saturation method, it is not effective when the initial moisture content is low. The results obtained from numerical simulation model and the electrical resistance measurements after incremental immersion suggested that the water permeability of HPCs can be accurately determined if the surface region (140 mm width and 25 mm depth) is fully saturated.
       
  • Preparing hyperbranched polycarboxylate superplasticizers possessing
           excellent viscosity-reducing performance through in situ redox initialized
           polymerization method
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): Zhen Huang, Yong Yang, Qianping Ran, Jiaping Liu Significant improvements to modern concrete have emerged in recent years, primarily due to application of various polycarboxylate dispersant with designed structure. However, self-compacting or high strength concrete characterized by a low water-to-cement ratio (w/c) pose challenges for their viscosity and pumpability. Here we propose a strategy so called in situ redox polymerization method to synthesis hyperbranched polycarboxylate superplasticizers. By adopting a unique monomer Dimethylaminoethyl Methacrylate, acting as monomer as well as initiator, hyper-branched structure are obtained through this one-pot synthesis procedure. In contrast to their conventional counterparts, that is, comb-like polycarboxylate, hyperbranched structure is shown to cut down the viscosity of pore solution and alleviate the shear thickening behavior of cement paste, leading to a 30% reduction in viscosity of paste. Moreover, owing to the ease of industrial manufacture, our approach, in situ redox polymerization method, show broad prospects and great potential for development.Graphical abstractImage 1
       
  • Microstructure development and mechanism of hardened cement paste
           incorporating graphene oxide during carbonation
    • Abstract: Publication date: Available online 29 August 2018Source: Cement and Concrete CompositesAuthor(s): Wu-Jian Long, Yu-cun Gu, Feng Xing, Kamal, H. Khayat In this work, the carbonation mechanism of cement paste containing graphene oxide (GO) was examined by evaluating its electrochemical, kinetic, and microstructural characteristics under accelerated carbonation, corresponding to a 20% concentration of CO2, a temperature of (30 ± 1)°C, and a relative humidity of 65%–70%. Transport properties of the composites were studied using a non-destructive electrochemical impedance spectroscopy (EIS) technique, while their carbonation kinetics was investigated via thermogravimetric analysis (TGA). The obtained EIS results indicated that the ion diffusion and transport resistance increased after the incorporation of GO, while TGA results revealed that the carbonation of portlandite (CH) and calcium-silicate-hydrate (C-S-H) was significantly inhibited during early ages of carbonation due to the increased degree of hydration. In addition, the hybrid GO/hydration products from the carbonation process were characterized, and the formation of a hydrated phase coated with a carbonated layer was observed via scanning electron microscopy and energy dispersive spectroscopy. Porosity variations of the studied materials during carbonation were also evaluated using a mercury intrusion porosimetry method. The porosity of the OPC decreased more significantly during the initial carbonation period as compared to the effect observed for the GO cement-based material.
       
  • Inhibiting efflorescence formation on fly ash–based geopolymer via
           silane surface modification
    • Abstract: Publication date: November 2018Source: Cement and Concrete Composites, Volume 94Author(s): Xiao Xue, Yun-Lin Liu, Jian-Guo Dai, Chi-Sun Poon, Wei-Dong Zhang, Peng Zhang Efflorescence can be a critical issue for the application of alkali-activated fly ash–based geopolymer products, especially when the products are in a moist environment. In this study, a new method was explored to inhibit efflorescence of fly ash–based geopolymer via silane surface modifications. After the modification, the surface of the geopolymer was transformed from hydrophilic to hydrophobic, with a water contact angle of 144.1°, and the capillary absorption and diffusion of water were significantly suppressed; and as a consequence, the soluble alkali ion leaching was reduced. Analysis by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and size-exclusion chromatography demonstrated that the selected silane is attached successfully onto the surface of the fly ash–based geopolymer via chemical bonding instead of via physical absorption. A possible reaction mechanism for the silane surface modification of the fly ash–based geopolymer is proposed.
       
  • Rheology of CAC-Based cement pastes and the relationship to penetrability
           through nonwoven fabric reinforcements
    • Abstract: Publication date: Available online 25 August 2018Source: Cement and Concrete CompositesAuthor(s): J. Claramunt, H. Ventura, M. Ardanuy In this study, we present an analysis of the rheological behaviour of calcium aluminate cement (CAC) based pastes with variable metakaolin (MK) contents (0–50%), with and without superplasticizer (SP) and at different water/cement ratios. Viscosity tests were performed under variable shear rate to analyze the macroscopic flow behaviour of the pastes. Furthermore, the penetrability of the pastes into natural fiber nonwoven fabric was examined using optical microscopy. The penetrability results were assessed to determine the suitability of the pastes for production of textile-reinforced composites. It was found that increased metakaolin content and decreased water/cement ratio both led to reduced viscosity. The addition of SP led to a reduction in viscosity, although this effect was lessened at high MK contents. Penetrability tests indicated that the paste viscosity significantly influenced the ability of the pastes to flow through the nonwoven structure, with more viscous pastes showing reduced penetrability.
       
  • Deterioration of residential concrete foundations: The role of
           pyrrhotite-bearing aggregate
    • Abstract: Publication date: Available online 22 August 2018Source: Cement and Concrete CompositesAuthor(s): Rui Zhong, Kay Wille Premature deterioration of concrete foundations has been reported for a large number of homes in Eastern Connecticut of the United States. The characteristic symptoms are map cracking, whitish deposits at the vicinity of the cracking surface and wide crack opening. It is hypothesized that the volume expansion associated with the oxidation of pyrrhotite-bearing aggregate and the following internal sulfate attack (ISA) due to the delayed secondary mineral formation are the primary causes of premature deterioration. Extensive tests were carried out to validate the hypothesis using a combination of tools such as scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) and energy dispersive X-ray (EDX).The results showed that pyrrhotite and its oxidation products, such as ferrihydrite, goethite and sulfur, were present in or at the surface of the aggregates of the deteriorated concrete, suggesting the occurrence of pyrrhotite oxidation. Expansive secondary mineral formations (SMF) such as ettringite and thaumasite were also identified. The abundance of these SMFs, their spatial distribution in the open spaces together with their close association with matrix cracking suggest the cause of premature deterioration.
       
  • Comparative evaluation on the dispersion and stability of graphene oxide
           in water and cement pore solution by incorporating silica fume
    • Abstract: Publication date: Available online 18 August 2018Source: Cement and Concrete CompositesAuthor(s): Zeyu Lu, Dongshuai Hou, Asad Hanif, Wenbin Hao, Guoxing Sun, Zongjin Li Many literature have reported that the dispersion of carbon nanomaterials (CNs) in cement matrix can be improved by incorporating silica fume (SF) due to its ultra-fine size. Most of works characterized the dispersion of CNs and SF in hardened cement matrix by scanning electron microscopy (SEM) and investigated their dispersion by measuring the mechanical properties of cement composites modified by both. However, SEM is not a good tool to investigate the dispersion of nano-scaled materials in macro-scaled cement matrix due to the extreme high magnification, and the interaction between the SF and CNs in cement matrix is still not clear and hardly to be revealed due to the small dosage of both in cement. The present work aims to give a comparative study on the effect of SF on the dispersion and stability of graphene oxide (GO), one of the most popular CNs, in the solutions of neutral water and alkaline cement pore solutions (CPS), instead of hardened cement matrix. The UV–vis spectroscopy and zeta potential results indicate that the addition of SF can improve the dispersion and stability of GO in water. GO can cover the surface of SF by H-bonding and make the surface charge of SF more negative, and therefore enhance the dispersion of GO covered SF in water via stronger electrostatic repulsion. In addition, the particle size distribution results indicate that the addition of SF also reduces the size of GO from 1.8 μm to 0.8 μm, indicating that SF contributes to disaggregation of GO and improves the dispersion of GO in water. However, the addition of SF has a negative effect on the dispersion of GO in CPS, and the interaction between the SF and GO is totally different in CPS due to the rich of divalent cations (Ca2+), which can interlock the SF and GO and lead to the re-agglomeration and worse dispersion of SF-GO in CPS.
       
  • Damping property of prepacked concrete incorporating coarse aggregates
           coated with polyurethane
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): Kang Seok Lee, Jeong-Il Choi, Se Eon Park, Jae-Seung Hwang, Bang Yeon Lee This study proposes a new prepacked concrete incorporating coarse aggregates coated with polyurethane with high damping and investigates the mechanical properties and damping ratio of the proposed concrete. Two types of prepacked concretes, in this case new prepacked concrete produced with the materials and manufacturing process as proposed here and normal prepacked concrete were prepared. A series of experiments focusing on the density, strength, and impact test results of small-scale specimens and beam specimens as well as a modal analysis of a simply-supported beam were conducted in an effort to characterize the mechanical and damping properties of the new prepacked concrete. The test results showed that the damping ratio of the new prepacked concrete was as high as 10% in the range of 10 Hz to 200 Hz, which is approximately 10 times higher than that of normal prepacked concrete, with a decrease in the mechanical properties.
       
  • Elucidating the influences of compliant microscale inclusions on the
           fracture behavior of cementitious composites
    • Abstract: Publication date: Available online 17 August 2018Source: Cement and Concrete CompositesAuthor(s): Sumanta Das, Matthew Aguayo, Nihat Kabay, Barzin Mobasher, Gaurav Sant, Narayanan Neithalath The fracture response of cementitious composites containing compliant microencapsulated inclusions and its influence on the fracture process zone (FPZ) are reported. The incorporation of small amounts of phase change material (PCM) microcapsules (replacing up to 10% by volume of sand) is found to slightly improve the strength, fracture toughness, critical crack tip opening displacement (CTODc), and the strain energy release rates. Digital image correlation is used to examine the FPZ at the tip of the advancing crack, to better explain the influences of compliant microscale inclusions on energy dissipation. The FPZ widths are found to slightly increase with PCM dosage but its lengths remain unchanged. The increase in FPZ width is linearly related to the CTODc, showing that inelastic deformations of the crack-tip in the direction of crack opening are indeed influenced by microscale inclusions. It is shown that cementitious systems containing microencapsulated PCMs can be designed to demonstrate mechanical performance (including fracture) equivalent to or even better than their PCM-free counterparts, in addition to the well-described thermal performance.
       
  • Influence of the alkaline solution and temperature on the rheology and
           reactivity of alkali-activated fly ash pastes
    • Abstract: Publication date: Available online 17 August 2018Source: Cement and Concrete CompositesAuthor(s): M. Palacios, M.M. Alonso, C. Varga, F. Puertas The aim of the present research is to ascertain the effect of the nature and concentration of the alkaline activator and temperature on the rheological behaviour of alkali-activated fly ash (AAFA) pastes. Furthermore, the reaction process of fly ash has been investigated from rheological measurements.Resultshave shown that the increase of the activator concentration and the temperature leads to an increase of yield stress and apparent viscosity, mainly at temperatures above 65 °C when dissolution of fly ash and precipitation of hydration products is raised. In general, similar activation energies were determined for alkaline-activated fly ash pastes, regardless of the concentration and silica modulus of the activator, concluding that the underlying reaction mechanism is the same independently on the nature of the activating solution.
       
  • Unified modelling of the temperature effect on the autogenous deformations
           of cement-based materials
    • Abstract: Publication date: Available online 15 August 2018Source: Cement and Concrete CompositesAuthor(s): Jérôme Carette, Stéphanie Staquet Temperature effects are of primary importance for designing concrete structures. Some of the early age temperature effects on the concrete behaviour can be accurately taken into consideration by well-known maturity functions. However, the effect of temperature on the autogenous deformations development is more complex, and results in contradictory evidence. This paper studies the influence of various isothermal curing temperatures from 10 °C to 30 °C on the autogenous deformations of concrete. Binary and ternary binders containing up to 30% of limestone filler and 70% of blast-furnace slag are studied. The amplitude of both the self-desiccation deformation and the early age swelling deformation are observed to decrease with increasing temperature, whatever the binder nature. Mechanisms for this observation are suggested, and a corresponding model is developed. The effect of the binder nature, age and temperature on the autogenous deformations is assessed with this model. Based on this new model, it is shown that the effect of temperature on the autogenous deformation development can be either beneficial or detrimental, depending on the nature of the binder.
       
  • Rubber aggregate-cement matrix bond enhancement: Microstructural analysis,
           effect on transfer properties and on mechanical behaviours of the
           composite
    • Abstract: Publication date: Available online 14 August 2018Source: Cement and Concrete CompositesAuthor(s): N.-P. Pham, A. Toumi, A. Turatsinze Limited strain capacity and low tensile strength of cement-based materials make them brittle and sensitive to cracking, behavior that limits durability of cement-based applications. Rubber aggregates (RA) incorporation appeared to be a suitable solution to improve the strain capacity and to limit the propensity of such materials for cracking. However, bond defect between RA and cementitious matrix is well-known and detrimental to mechanical and transfer properties of rubberized cement-based composites. This paper is dedicated to the enhancement of rubber-cement matrix interface and then investigates effect of this bond on transfer properties and mechanical behaviors of rubberized mortars. To achieve this goal, RA were coated with styrene-butadiene copolymer and after densification of this copolymer resin on their surface, they were mixed with the premixed-cementitious mixture. Another approach implemented was the use of an air-detraining admixture to produce rubberized mixture with the similar air content as the control mortar. Microstructural studies firstly clarified that cement paste bonded firmly on copolymer-coated RA. Air-permeability of the rubberized mortar incorporating copolymer-coated RA was lower than that of the control mortar. Moreover, rubber coating approach was beneficial to reduce water capillary absorption and to limit reduction in direct tensile strength. It also results in a better residual post-peak behavior and higher fracture energy, contributing to improve the resistance of the composite to shrinkage cracking even under high restrained condition.
       
  • A chitosan based pH-responsive hydrogel for encapsulation of bacteria for
           self-sealing concrete
    • Abstract: Publication date: Available online 11 August 2018Source: Cement and Concrete CompositesAuthor(s): Jianyun Wang, Arn Mignon, Gilles Trenson, Sandra Van Vlierberghe, Nico Boon, Nele De Belie Cracks in concrete remain one of the major issues in constructions. Self-healing concrete by bacteria has already proven to be a promising way to solve this problem. In order to protect bacteria from the harsh condition in concrete, encapsulation of bacteria is preferable. In this study, a pH responsive hydrogel was synthesized to encapsulate bacterial spores for self-sealing concrete cracks. The pH responsiveness and the influence of the hydrogel on the mechanical properties were investigated. The viability of the encapsulated spores and the cell-entrapping capacity of the hydrogel were then examined. The self-sealing efficiency was evaluated by the reduction of water flow and crack sealing ratio. The results indicated that the chitosan based hydrogel had a suitable pH responsiveness. Within the pH range between 7 and 11, the swelling capacity remained stable, with no significant differences as the swelling varied between 38.5 ± 0.5 and 42.9 ± 1.5 g water/g hydrogel. The swelling greatly decreased to around 12.8 ± 0.9 g water/g hydrogel in cement filtrate. The compressive strength only decreased around 5% with the addition of 1 m% of hydrogel. The specimens with hydrogel encapsulated spores showed the highest reduction in water flow (81–90%) and highest crack sealing efficiency. More than 30% of the crack locations was completely bridged. While in other specimens, only 2–12% of the crack locations was completely sealed.
       
  • The impacts of policies to reduce CO2 emissions within the
           concrete supply chain
    • Abstract: Publication date: Available online 10 August 2018Source: Cement and Concrete CompositesAuthor(s): James Di Filippo, Jason Karpman, J.R. DeShazo The production of concrete is a significant source of global carbon dioxide (CO2) emissions that contribute to climate change. Many technical solutions exist for reducing emissions along the concrete supply chain. However, wide scale adoption of these technologies is hindered by a market failure – the cost of greenhouse gas emissions is not adequately reflected in cement and concrete transactions. Here, we compare three instruments meant to correct this critical market failure, including: 1) carbon-pricing policies, such as carbon taxes and cap-and-trade programs; 2) command and control policies; and 3) voluntary incentives. We evaluate each policy instrument for its capacity to reduce emissions cost effectively, guarantee emission reductions, spur technological innovation, and generate revenue. Our analysis shows that these criteria favor carbon pricing policies. However, cement and concrete markets are often concentrated and trade exposed. Therefore, regulators should design pricing policies that both combat leakage and do not limit production below socially optimal levels.
       
  • Mitigating steel corrosion in reinforced concrete using functional
           coatings, corrosion inhibitors, and atomistic simulations
    • Abstract: Publication date: Available online 10 August 2018Source: Cement and Concrete CompositesAuthor(s): Magdalena Balonis, Gaurav Sant, O. Burkan Isgor We describe new approaches based on compositional manipulation of the cementitious binder, and its geometrical arrangement, to mitigate steel corrosion in concrete, and a new ability to study corrosion processes from a fundamental point of view. First, we present a new approach to mitigate/delay corrosion initiation using calcium aluminate cement (CAC) and Ca(NO3)2 based functional coatings by replacing a fractional thickness of the ordinary portland cement (OPC) concrete cover. Second, within a related framework, we demonstrate how tailoring the binder chemistry to produce enhanced quantities of AFm phases is a significant means to immobilize Cl− ions while actively generating corrosion inhibiting species; thereby delaying corrosion initiation. Finally, we offer new insights from reactive force field molecular dynamics (ReaxFF-MD) simulations as a means to interrogate and explain electrochemical processes at the atomistic scale. We present examples of how atomistic simulations can uncover the origins of passivity and Cl− induced corrosion at a molecular level and how such understanding can accelerate the development of new corrosion resistant materials and mitigation strategies.
       
  • Suitability of natural calcined clays as supplementary cementitious
           material
    • Abstract: Publication date: Available online 10 August 2018Source: Cement and Concrete CompositesAuthor(s): Simone Elisabeth Schulze, Jörg Rickert The use of natural calcined clays as supplementary cementitious material (SCM) is becoming increasingly interesting for the cement industry. Most of investigations on calcined clays in literature work on pure kaolinitic and illitic clays. The presented research deals with 15 clays of different levels of quality, representing a wide range of natural clay deposits, were examined in terms of their suitability as a cement constituent. Therefore the clays were calcined under different burning conditions and different analyses to determine the reactivity of the calcined products were carried out and discussed. Furthermore, a sensitive method for determination of reactive silica which correlates clearly with clay's strength contribution was used. Cements with 20 and 40 mass % of calcined clay respectively were produced and examined in terms of their cement-relevant properties.The production of calcined clays in compliance with the requirements of EN 197-1 was possible with all examined varieties of clay. In addition, it was also possible to produce cements in strength class 42,5 R with the calcined clays. Clay mineralogy and burning conditions had a considerable influence on the calcined clays' contribution to strength within the cement. The overall results let expect the suitability of a broad range of calcined natural clays as SCM. The results of this study suggest that a broad range of natural calcined clays are suitable as SCM's.
       
  • Mechanical, thermal and acoustic properties of cellular alkali activated
           fly ash concrete
    • Abstract: Publication date: Available online 8 August 2018Source: Cement and Concrete CompositesAuthor(s): Jonathan Stolz, Yaman Boluk, Vivek Bindiganavile This article characterizes a cellular system prepared from alkali activated Class C fly ash mixed with a preformed foam. The resulting mixture was cast at three densities between 1000 and 1400 kg/m3 and all tests were conducted under ambient drying conditions resulting in densities between 940 and 1310 kg/m3. A phase analysis of the components in the cell wall was performed using X-ray diffraction. The compressive strength ranged from 3 to 9 MPa, while the corresponding modulus of elasticity was between 850 and 1700 MPa. The thermal constants were measured using the Transient Plane Heat Source (TPS) technique per ISO 22007-2. Sound absorption and noise reduction coefficients were evaluated using the impedance tube method per ASTM C384-04. The results show that at an oven dry density near 1000 kg/m3, this alkali activated system is a viable alternative for thermal and sound insulation with properties comparable to those of current commercially available options.
       
  • Topological optimization of cementitious binders: Advances and challenges
    • Abstract: Publication date: Available online 4 August 2018Source: Cement and Concrete CompositesAuthor(s): Han Liu, Tao Du, N.M. Anoop Krishnan, Hui Li, Mathieu Bauchy The properties of cementitious binders are controlled by their structure at different scales. However, the complexity of their disordered structure makes it challenging to elucidate the linkages between atomic and mesoscale structure and macroscopic properties. Recently, topological approaches—which capture the connectivity of the atoms or grains while filtering out less relevant structural details—have been shown to offer a powerful framework to guide the optimization of cementitious binders' properties by tuning their internal topology at different scales. Here, we review recent advances in the topological optimization of cementitious binders at the atomic and mesoscopic scales and attempt to identify the present challenges that need to be overcome. Elucidating the topological genome of cementitious binders (i.e., how their macroscopic properties are encoded in their topology) could accelerate the optimization of existing binders or discovery of novel formations with unusual properties.
       
  • Determining chloride content profiles in concrete using an electrical
           resistivity tomography device
    • Abstract: Publication date: Available online 3 August 2018Source: Cement and Concrete CompositesAuthor(s): Milia Fares, Géraldine Villain, Stéphanie Bonnet, Sérgio Palma Lopes, Benoit Thauvin, Mickaël Thiery Chloride penetration in concrete can lead to steel corrosion which is one of the major pathologies affecting reinforced concrete's durability. The development of methods to investigate chloride penetration is essential to predict and update the service life of the structure. A non-destructive (ND) DC-electrical technique is used in this study: this Electrical Resistivity Tomography (ERT) device is arranged in a Wenner configuration and measures apparent resistivities. Apparent resistivities are then inverted in order to obtain a resistivity profile versus depth. In parallel, a calibration method relating the resistivity to the chloride content for each type of concrete is used to obtain the chloride profile versus depth. This methodology was applied to a chloride diffusion experimental program on two concrete formulations and one mortar. The profiles evaluated by NDT are then compared to those obtained by a destructive method (potentiometric titration). Both types of profile fit relatively well, thus, the presented methodology is validated for determining chloride content profiles by means of a non-destructive ERT device. The evaluation of the uncertainty range of successive processes (measurement, inversion and calibration) underlines the importance on including the uncertainties in the interpretation of the ND profiles in future research.
       
  • Impact characterization and modelling of basalt‒polypropylene
           fibre-reinforced concrete containing mineral admixtures
    • Abstract: Publication date: Available online 1 August 2018Source: Cement and Concrete CompositesAuthor(s): Qiang Fu, Ditao Niu, Dan Li, Yan Wang, Jian Zhang, Daguan Huang The impact-resistance behaviour of basalt‒polypropylene fibre-reinforced concrete containing the mineral admixture (BPFRC) was experimentally investigated under impact loading using a ϕ75 mm split-Hopkinson pressure bar. The results showed that the dynamic compressive strength, dynamic elastic modulus and critical strain of BPFRC increased with increasing strain rate. The addition of basalt fibre (BF) and polypropylene fibre (PF) yielded significant increases in the strain rate effect of the dynamic compressive strength and dynamic elastic modulus of concrete and improved the deformation capacity of concrete. The influence of PF on the strain rate effect of dynamic compressive strength of concrete was greater than that of BF. However, there was no clear difference between the influences of BF and PF on the strain rate effect of the dynamic elastic modulus of concrete. There was a significant positive correlation between the hybrid volume of fibre and the strain rate effect of the dynamic compressive mechanical behaviour of BPFRC. The proposed viscoelastic damage constitutive model in this study can be used to accurately describe the dynamic mechanical behaviour of BPFRC.
       
  • Deterioration and recovery of FRC after high temperature exposure
    • Abstract: Publication date: Available online 31 July 2018Source: Cement and Concrete CompositesAuthor(s): Abdullah Huzeyfe Akca, Nilüfer Özyurt In general, physical properties of concrete deteriorate after high temperature exposure and this is a result of some morphological changes occur in microstructure of concrete. After heating some new phases occur in concrete and these have a tendency to react with water and carbon dioxide at the post heating stage. The most common one is expansive rehydration of CaO by turning into Ca(OH)2 and this reaction should be avoided for concrete of which mechanical properties deteriorated after heating. Since, Ca(OH)2 is a soluble product in water, water re-curing after high temperature exposure can be beneficial. Also using steel fibers in concrete may be useful to restrain the stresses occurred due to this expansion and polypropylene fibers can be used to reduce the pore pressure in concrete during heating. Therefore, 8 groups of 0.45 w/c ratio of concrete were produced by using different fibers and air entraining admixture. Cubic concrete specimens (15 cm on a side) were cast and only one face of the specimens was subjected to 1000 °C. K-Type thermocouples were placed in concrete specimens to monitor temperature change during heating. Two re-curing methods, air and water, were applied to specimens following the cooling period. SEM, EDX, XRD and TGA investigations were conducted to evaluate the morphological changes in concrete. Then effects of these changes on the residual mechanical properties of concretes were evaluated.
       
  • Impact of Temperature Rising Inhibitor on hydration kinetics of cement
           paste and its mechanism
    • Abstract: Publication date: Available online 25 July 2018Source: Cement and Concrete CompositesAuthor(s): Zhang Hao, Li Lei, Feng Pan, Wang Wenbin, Qian Tian, Jiaping Liu Present study examines the effect of Temperature Rising Inhibitor (TRI) on Portland cement hydration process and analyzes the mechanism hereof. The investigation of the impact of TRI on cement dissolution, C-S-H nucleation and growth process shows that TRI has little influence on the dissolution kinetics of cement and crystal-solution interfacial energy of C-S-H. In contrast, the modification of C-S-H grain size in solution and the C-S-H growth rate in cement suspensions are observed. Experiments involving TRI and synthesized C-S-H confirm that TRI will preferentially adsorb on the C-S-H surface and inhibit growth of C-S-H.
       
  • Bond performance of steel rebar embedded in 80–180 MPa
           ultra-high-strength concrete
    • Abstract: Publication date: Available online 25 July 2018Source: Cement and Concrete CompositesAuthor(s): Doo-Yeol Yoo, Hyun-Oh Shin Ultra-high-strength concrete (UHSC) has attracted attention from engineers because of its great capability on reducing the size of reinforced concrete columns. However, the bond performance of steel rebar embedded in UHSC has not been examined enough yet, although it is a fundamental information for structural design. So, this study comprehensively investigates the bond performance of deformed steel rebar embedded in high-strength concrete (HSC), very-high-strength concrete (VHSC), and UHSC with compressive strengths ranging from 80 to 180 MPa. Different bar diameters (12.7, 15.9, and 19.1 mm), embedment lengths (0.5, 1.0, and 1.5 × bar diameter), cover depths (1, 2, and 3 × bar diameter and center), steel fiber volume fractions (0, 0.5, 1.0, and 1.5%), and yield strengths of steel rebar (normal-strength vs. high-strength) were all considered. Test results indicate that the average bond strength increased significantly with an increase in the compressive strength of the concrete and decreased slightly with an increase in the bar diameter. Average bond strengths of steel rebars in HSC, VHSC, and UHSC were all increased by increasing the embedment length. The cover depth marginally influenced the bond strength when pullout failure was generated, and it significantly increased the bond strength when splitting failure occurred. The incorporation of steel fibers most effectively increased the bond strength in the UHSC mixture, compared with the HSC and VHSC mixtures. Lastly, the widely used prediction models for average bond strength were not accurate for concrete with a compressive strength greater than 80 MPa; thus, a new, appropriate model needs to be proposed in the near future.
       
  • Rate-dependent tensile properties of ultra-high performance engineered
           cementitious composites (UHP-ECC)
    • Abstract: Publication date: Available online 25 July 2018Source: Cement and Concrete CompositesAuthor(s): Ke-Quan Yu, Jian-Guo Dai, Zhou-Dao Lu, Chi-Soon Poon The direct tensile properties of ultra-high performance engineered cementitious composites (UHP-ECC) were investigated under a range of strain rates from 0.0001 to 0.05 s−1 in this study. Three kinds of polyethylene fibers with different fiber aspect ratios were used as the reinforced fiber in the UHP-ECC. The rate sensitivity of the UHP-ECC in tension was evaluated in terms of initial cracking stress, peak stress, strain capacity, energy absorption capacity and elastic modulus at different strain rates. The cracking patterns, including crack number, crack width and crack spacing, of the UHP-ECC specimens were also monitored. The test results showed a significant rate effect on the initial cracking stress and a moderate effect on the peak stress and strain capacity. The fiber aspect ratio significantly influenced the tensile properties and failure modes of the UHP-ECC. The matrix strength, single fiber tensile and pull-out tests were conducted at corresponding strain rates to further explain the test results. Finally, the micro-structure of the tensile specimens was observed using a scanning electron microscope.
       
  • Mechanism of PVA fibers in mitigating explosive spalling of engineered
           cementitious composite at elevated temperature
    • Abstract: Publication date: Available online 25 July 2018Source: Cement and Concrete CompositesAuthor(s): Jin-Cheng Liu, Kang Hai Tan Polyvinyl alcohol (PVA) fibers have been found effective in preventing explosive spalling of engineered cementitious composite (ECC) under fire loading. However, the fundamental mechanism of minimizing the spalling risk by adding PVA fibers remains unclear. Thus, this paper addresses the mode of action of PVA fibers in combating explosive spalling of ECC at high temperature. In this regard, hot permeability of ECC and mortar was measured. PVA fibers were found to increase hot permeability of ECC significantly before their melting. Microstructure and EDX analysis were conducted to achieve a better understanding of how PVA fibers actually function to increase hot permeability before melting. The enlarged empty zones around the PVA fibers were the reason for the significant increase in permeability. Residue from melted PVA fibers was observed on the channel walls and did not diffuse into the matrix. For the first time laser distance meter was used to record progressive spalling history in heated samples. An in-depth discussion on the relationship between temperature, pore pressure, and spalling was also provided.
       
  • Roles of water film thickness and fibre factor in workability of
           polypropylene fibre reinforced mortar
    • Abstract: Publication date: Available online 24 July 2018Source: Cement and Concrete CompositesAuthor(s): L.G. Li, S.H. Chu, K.L. Zeng, J. Zhu, A.K.H. Kwan For plain mortar without fibres, it has been found that its fresh properties are governed mainly by the water film thickness (WFT). For fibre reinforced mortar with fibres added, it has been suggested that the effects of the fibres may be evaluated in terms of a fibre factor (FF) combining the fibre volume and aspect ratio together. In two previous studies on the workability of polypropylene (PP) fibre reinforced mortar, the combined effects of WFT and fibre volume and the combined effects of WFT and fibre length have been separately studied. Herein, additional tests with both the fibre volume and fibre length varying simultaneously have been carried out to generate more data for evaluating the combined effects of WFT, fibre volume and fibre length. Based on the test results, a new model is developed whereby the workability attributes are each expressed as a single-variable function of the product of a linear function of WFT and an exponential function of FF. By this model, the roles of WFT and FF are revealed and the workability may be estimated for preliminary design of PP fibre reinforced mortar.
       
  • A mixture proportioning method for the development of performance-based
           alkali-activated slag-based concrete
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): Ning Li, Caijun Shi, Zuhua Zhang, Deju Zhu, Hyeon-Jong Hwang, Yuhan Zhu, Tengjiao Sun This paper reports a general mixture design procedure for alkali-activated slag concrete, which is an essential step towards industrial application. The procedure involves three steps: 1) the determination of coarse and fine aggregate ratio according to close packing model; 2) the determination of liquid phase (water content and activator) based on compressive strength; and 3) the determination of excess paste content by workability requirement and measurement. Effects of mixture proportional factors, including activator composition, water content, fly ash content, and binder/aggregate ratio are examined on consistency, setting time and compressive strength. The relationship between performance and precursor composition is established using simplex centroid design method. Using the mixture proportioning method, alkali-activated concretes with compressive strength grades of C40, C60, and C80 are successfully prepared with initial setting time of 1–3 h and slump of more than 200 mm.
       
  • Enhancing the mechanical features of clay surfaces by the absorption of
           nano-SiO2 particles in aqueous media. Case of study on Bronze Age clay
           objects
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): E. Rayón, M.P. Arrieta, T. Pasíes, J. López, J.L. Jordá Nanoparticles are known to be able to enhance the performance of low dense materials, achieving the small intergranular spaces to further interact with the matrix. In this work, a consolidation treatment of an ancient clay material is reported. It is based on the use of silica nanoparticles dispersed in an aqueous medium as a more sustainable approach than those currently used in the conservation field. The effective consolidation has been determined by ensuring an appropriate mechanical surface resistance using the nanoindentation technique as non-destructive measurements. Moreover, the ability of SiO2 nanoparticles to fill the microstructure is studied by scanning electron microscopy. As a case report, several low-strength clay fragments dated from the Bronze Age were surface treated with a commercial aqueous suspension of SiO2 nanoparticles that were analyzed by transmission electron microscopy (TEM) displaying dimensions of about 20 nm in diameter. Field Emission Electron Microscopy (FESEM) revealed that nanoparticles filled the inter-granular spaces of the clay, leading to a nanostructured material. The nanoindentation results showed an increase in surface resistance against scratching. Meanwhile, the nanohardness and elastic modulus increased 10 times (from 15 to 150 MPa) and 8 times (from 1 to 8 GPa), respectively due to the nanoSiO2 treatment, confirming the consolidation effect of the nanoparticles.Graphical abstractImage 1
       
  • Use of uncontaminated marine sediments in mortar and concrete by partial
           substitution of cement
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): Zengfeng Zhao, Mahfoud Benzerzour, Nor-Edine Abriak, Denis Damidot, Luc Courard, Dongxing Wang The disposal of dredged marine sediments has become a major economic and environmental issue in the world. In this study, uncontaminated marine sediments dredged in the harbor of Dunkirk (France) were dried and ground and then used in partial substitution of cement in the manufacture of mortars and concretes. A given volume of cement has been replaced by the same volume of sediment for three substitution contents (10%, 20%, 30%) of a Portland cement CEM I 52.5. The flexural and compressive strengths of mortars decreased when the sediment replacement content increased. However, the mechanical properties of the mortar with 20% replacement of cement with sediments were better than those of a mortar made from cement CEM II/A-LL 32.5 containing a proportion of limestone similar to the sediment substitution. The total porosity measured by mercury intrusion porosimetry of different types of mortars showed that the porosity increased as the sediment substitution content increased but the pore size distribution was shifted toward smaller pores. Finally, it was demonstrated that concrete C30/37 could be designed with 20% cement replaced by sediment without the use of admixture. Additionally, this concrete fulfilled the standards with respect to the total chloride content required for unreinforced concrete. As a conclusion, dried and finely ground uncontaminated sediments appeared to be a very interesting constituent for partially substituting up to 20% of cement as its efficiency overpass limestone filler.
       
  • Editorial: Sustainability and “CCC”
    • Abstract: Publication date: Available online 21 July 2018Source: Cement and Concrete CompositesAuthor(s): Koji Sakai
       
  • The effect of fiber orientation on the post-cracking behavior of steel
           fiber reinforced concrete under bending and uniaxial tensile tests
    • Abstract: Publication date: Available online 21 July 2018Source: Cement and Concrete CompositesAuthor(s): Antonio Mudadu, Giuseppe Tiberti, Federica Germano, Giovanni Plizzari, Alessandro Morbi The present paper deals with an experimental study on the post-cracking tensile behavior of Steel Fiber Reinforced Concrete (SFRC). In this regard, a broad experimental campaign based on Uniaxial Tensile Tests (UTTs) on notched cylinders as well as three point bending tests (3 PBTs) on notched beams was carried out.Based on the experimental results, the benefits offered by the addition of fiber in the post-cracking behavior was deeply studied: fibers increase the toughness of concrete and the ultimate crack width.The uniaxial post-cracking tensile laws of SFRCs were directly obtained by UTTs and indirectly retrieved by 3 PBTs by performing an inverse analysis procedure. In the latter case the fracture energy was generally higher. It was proven that there is a strongly dependency of the SFRC post-cracking performance with the fiber distribution and orientation that was measured by means of image-analysis technique.
       
  • Role of soluble aluminum species in the activating solution for synthesis
           of silico-aluminophosphate geopolymers
    • Abstract: Publication date: Available online 20 July 2018Source: Cement and Concrete CompositesAuthor(s): Yan-Shuai Wang, John L. Provis, Jian-Guo Dai An aluminosilicate precursor, such as metakaolin, can be transformed into a cement-like geopolymer binder via a phosphate activation approach. This paper identifies the effect of the addition of aluminum species into the phosphate activating solution on the formation of such geopolymers, from the fresh to the hardened state. Activating solutions with Al/P molar ratios of 0, 0.1, and 0.3 were prepared by blending monoaluminum phosphate (MAP) and orthophosphoric acid (OPA). The rheological properties, fluidity, and setting times of the fresh geopolymer pastes and the compressive strength of the hardened geopolymer matrices were studied. Liquid-state 27Al and 31P nuclear magnetic resonance (NMR) measurements for the chemical environments of Al and P, and spectroscopic, thermal, and microscopic analyses revealed that the soluble aluminum in the phosphate activating solution played an important role during the geopolymerization process. Seeding of aluminum species through inclusion in the activating solution allowed a rapid sol/gel transition that improved the rheological properties and setting time of the fresh geopolymer pastes at ambient temperature. However, although the increased concentration of aluminum phosphate oligomers promoted by the soluble aluminum addition contributed to the formation of a compact matrix with high early strength, it hinders the ongoing reaction of metakaolin in the later period, which has a detrimental influence on ongoing strength development beyond 7 days of curing.
       
  • Reaction kinetics of red mud-fly ash based geopolymers: Effects of curing
           temperature on chemical bonding, porosity, and mechanical strength
    • Abstract: Publication date: Available online 18 July 2018Source: Cement and Concrete CompositesAuthor(s): Mo Zhang, Mengxuan Zhao, Guoping Zhang, Jennifer M. Sietins, Sergio Granados-Focil, Marc S. Pepi, Yan Xu, Mingjiang Tao The reaction kinetics of red mud-class F fly ash based geopolymer (RFFG) was investigated through understanding the influence of curing temperature on the formation of geopolymer gel, porosity, and the development of mechanical properties. Chemical bonding, mineralogy, mechanical properties and porosity of RFFG during a curing period of up to 120 days were assessed with Fourier transform infrared spectroscopy, X-ray diffractometer, unconfined compression tests, and micro-CT and N2-BJH techniques, respectively. The geopolymer gels were found to develop via a three-stage process: dissolution–Al-rich gels (I), Al-rich gels–Si-rich gels (II) and Si-rich gels–tectosilicate networks (III). The mechanical strength is largely governed by the development of geopolymer gels and affected by porosity, both of which are influenced by curing temperature. The early mechanical strength of RFFG is enhanced by elevated curing temperatures, but the long-term strength can be compromised by higher porosity resulted from an excessively high curing temperature.
       
  • Carbonation depth predictions in concrete bridges under changing climate
           conditions and increasing traffic loads
    • Abstract: Publication date: Available online 17 July 2018Source: Cement and Concrete CompositesAuthor(s): Chao Jiang, Xianglin Gu, Qinghua Huang, Weiping Zhang This paper first introduced a numerical carbonation model (NCM) for fatigue-damaged concrete. Then, based on the NCM, a simplified carbonation model (SCM) for fatigue-damaged concrete was established, comprised of a non-damaged concrete contribution term and a fatigue damage contribution term, through Monte Carlo simulations. Both the NCM and SCM were verified by experimental results reported in the literature. Subsequently, an incremental method was proposed to consider the time-variant fatigue damage and exposure conditions. Finally, a case study was conducted, which determined that cumulating fatigue damage could have a big influence on carbonation depth evolution. Meanwhile, differences in the cumulating fatigue damage could lead to noticeable differences in carbonation depth evolution among different points in the same concrete bridge. Moreover, drastic increases of CO2 concentration and temperature could induce relationships of carbonation depths with square roots of service times to remarkably deviate from the proportional laws widely accepted under a time-invariant environment.
       
  • Durability performance of high-performance concrete made with recycled
           aggregates, fly ash and densified silica fume
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): D. Pedro, J. de Brito, L. Evangelista This study intends to analyse the effects of the incorporation of recycled aggregates (RA) and densified silica fume (SF) on the durability of high performance concrete (HPC). Considering that the mortar adhered to the RA strongly influences the behaviour of the concrete made with it, the source of these aggregates was restricted to precast mixes with target compressive strengths of 75 MPa and subjected to a primary plus a secondary crushing process. With regard to SF, a certified commercial product was used, which was incorporated in the concrete as an additional material to cement. The experimental campaign included the production of 12 types of concrete, which were evaluated by means of water absorption by immersion, water absorption by capillarity, resistance to carbonation, resistance to chloride penetration and permeability to oxygen tests. The results show that it is possible to produce HPC with significant quantities of fine and coarse recycled aggregates (FRA and CRA) as replacement of traditional fine and coarse natural aggregates (FNA and CNA). Ultimately, considering the properties analysed, it seems possible to produce HPC without incorporating natural aggregates (NA). The incorporation of densified silica fume contributed to an increase of concrete's performance through the use of a mixing process developed by the authors that minimized the previously endured dispersion difficulties associated with this product.
       
  • Flexural behaviors of fiber-reinforced polymer fabric reinforced
           ultra-high-performance concrete panels
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): Weina Meng, Kamal Henri Khayat, Yi Bao The use of fiber-reinforced polymer (FRP) fabrics as reinforcement in concrete offers several advantages, such as high tensile strength, corrosion resistance, and light weight. This paper presents experimental and mechanical studies on the flexural behaviors of FRP fabric reinforced ultra-high-performance concrete (UHPC) panels. Glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) fabrics were investigated. Mechanical properties of GFRP and CFRP fabrics, high-strength mortar, and UHPC containing micro steel fibers were experimentally evaluated. The interfacial properties between the FRP fabric and cementitious matrix were characterized using push-pull tests. The flexural performance of panels with different reinforcement configurations was experimentally evaluated. The use of GFRP or CFRP fabric enhanced the flexural properties of UHPC panels, but did not lead to any increase in the flexural strength for the panels made with high-strength mortar. A mechanical analysis is performed to understand and predict the flexural behavior of the FRP fabric reinforced UHPC panels. The proposed fabric reinforced UHPC panel is demonstrated to be promising for the development of lightweight, high-performance permanent formwork system. Such formwork can be potentially used in accelerated construction of critical infrastructure with enhanced crack resistance and extended service life.
       
  • Improved mesoscale segmentation of concrete from 3D X-ray images using
           contrast enhancers
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): P. Carrara, R. Kruse, D.P. Bentz, M. Lunardelli, T. Leusmann, P.A. Varady, L. De Lorenzis Obtaining the mesostructure of concrete from X-ray computed tomography (CT) requires segmentation of the data into distinct phases, a process complicated by the limited contrast between aggregates and mortar matrix. This paper explores the possibility to add baryte or hematite into the concrete mixture to enhance the contrast between cement paste and aggregates in CT, thus allowing for a semi-automatic segmentation. Raw and segmented CT images of plain and modified concrete mixtures are obtained and compared to assess the validity of the proposed approach. Characterization tests are also performed in order to ensure that the concrete characteristics are not appreciably affected by the presence of the enhancers.
       
  • Properties of recycled aggregate concrete prepared with scattering-filling
           coarse aggregate process
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): Gelong Xu, Weiguo Shen, Bingliu Zhang, Yongxin Li, Xiaoli Ji, Yongxin Ye RAC produced with crushed recycled aggregate (RA) is regarded as an environmental friendly material, while its high water demand, high mortar content and low modulus have restricted its application. Scattering-filling coarse aggregate (SFCA) process was applied to prepare the recycled aggregate concrete with promoted performance. With the reference of conventional concrete and the scattering-filling natural aggregate (SFNA) concrete, the influences of ratio, type, size and moisture state of RA on mechanical and durable properties of scattering-filling recycled aggregate (SFRA) concrete were investigated. The results indicate that SFCA process could improve the compressive strength, elastic modulus, and reduce the drying shrinkage and chloride penetration. The frost resistance of SFRA is comparable with the conventional concrete. With 10–20 mm scattering-filling aggregate of RA, SFCA concretes get more significant improvement on elastic modulus and anti-permeability; Higher water content of RA worsen the performance of recycled aggregate concrete (RAC) for water in the RA weakening ITZ; Furthermore, image processing analysis and microhardness indicated that SFCA process improve the properties by increasing the homogeneity of aggregate distribution and improving ITZ between the aggregate and cement paste in RAC. SFCA process provides an economic method to produce high-quality recycled aggregate concrete and an efficiently approach to the utilization of recycled concrete aggregate from Construction and Demolition waste.
       
  • Experimental investigation of compressive strength and compressive
           fracture energy of longitudinally cracked concrete
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): Hikaru Nakamura, Takahiro Nanri, Taito Miura, Sushanta Roy In this study, compression tests of longitudinally cracked concrete were conducted to clarify the effect of existing crack on reduction of compressive strength and compressive fracture energy. In the specimens, one or two longitudinal cracks were introduced mechanically before compression loading. The experimental parameters were set to specimen shape, size, height to diameter ratio, coarse aggregate size, number of existing crack and the width. Based on experimental evidences, it was clarified that the reduction of both compressive strength and compressive fracture energy due to existing crack was dependent on crack width and those reduction tendencies are clearly influenced by coarse aggregate size without the effect of other parameters. Moreover, in order to discuss the reduction mechanism, compression tests focused on the effect of crack shape such as wave height and length were also conducted. In the specimens, imitation of existing cracks were embedded for neglecting the effect of damage near crack. As a result, it was found that the crack shape was significant for the reduction of concrete strength and compressive fracture energy. Finally, compressive strength reduction model in association with maximum crack width and maximum coarse aggregate size was proposed.
       
  • Superabsorbent polymers to mitigate plastic drying shrinkage in a cement
           paste as studied by NMR
    • Abstract: Publication date: October 2018Source: Cement and Concrete Composites, Volume 93Author(s): D. Snoeck, L. Pel, N. De Belie At early ages, a problem of plastic shrinkage can arise when a cement paste is subjected to harsh drying conditions during hardening. SuperAbsorbent Polymers (SAPs) are a promising admixture to mitigate shrinkage in cement pastes. By introducing internal curing by means of the stored mixing water in the SAPs, the plastic shrinkage can be partially mitigated, next to the mitigation of autogenous shrinkage during setting of the cement paste. The kinetics of water release by the SAPs towards the cementitious matrix have been studied in detail to understand the mechanism. Nuclear Magnetic Resonance (NMR) is an effective technique to non-destructively monitor the effects induced by the SAPs during this plastic period and hardening as a function of time. The SAPs are able to protect the cement paste internally from the harsh ambient drying conditions and are able to sustain the internal relative humidity. The plastic settlement was reduced and there was less plastic shrinkage measured. Below 5 mm of the surface in SAP specimens, the specimens were hardening as if put in sealed conditions.
       
  • On the size effect of interfacial fracture between concrete and fiber
           reinforced polymer
    • Abstract: Publication date: Available online 10 July 2018Source: Cement and Concrete CompositesAuthor(s): Kyungsu Ha, Habeun Choi, Moochul Shin, Kyoungsoo Park In this study, the size effect of the nominal interfacial strength between concrete and fiber reinforced polymer (FRP) is investigated by integrating fracture tests and computational simulations. Three-point bending fracture tests are performed with geometrically similar specimens to demonstrate the size effect, and to measure fracture parameters for mode-I. Based on the measured fracture parameters, the crack-growth behavior is predicted using the finite-element-based cohesive zone model. Computational results predict accurately the experimental results of the load versus crack mouth opening displacement (CMOD) curves. Furthermore, both the computational and experimental results illustrate that the nominal interfacial strength decreases with increases in the specimen size, i.e., the size effect of the interfacial fracture. Because of the size effect, fracture parameters, such as the fracture energy, should be measured and evaluated to predict the interfacial fracture between concrete and FRP.
       
  • Carbonation activated binders from pure calcium silicates: Reaction
           kinetics and performance controlling factors
    • Abstract: Publication date: Available online 10 July 2018Source: Cement and Concrete CompositesAuthor(s): Warda Ashraf, Jan Olek This paper presents a study on the carbonation activated binders prepared from pure calcium silicate phases, which included tricalcium silicate (3CaO.SiO2, [C3S]), β-dicalcium silicate (β-2CaO.SiO2, [β-C2S]), γ-dicalcium silicate (γ-2CaO.SiO2, [γ-C2S]), tricalcium disilicate (rankinite, 3CaO.2SiO2, [C3S2]), and monocalcium silicate (wollastonite, CaO.SiO2, [CS]). The overall study consisted of three experimental parts, with individual focus on the following issues: (i) reaction kinetics, (ii) mechanical performance at the microscale, and (iii) mechanical performance at the macroscale. Carbonation of calcium silicate phases was found to occur in two distinct stages, namely: phase boundary controlled stage and product layer diffusion controlled stage. Theoretical solid-state reaction approach, including contracting volume model and Jander's equations were used to determine the carbonation rate constants for the calcium silicate phases. Phase boundary controlled stage was found to be dominantly dependent on the type of the starting calcium silicate phases. On the other hand, during the diffusion controlled stage the reaction rate constants were found to depend on the type of carbonation products (in this case Ca-modified silica gel and calcium carbonate). The mechanical properties of the individual microscopic phases were evaluated using nanoindentation test whereas the overall strength of the carbonated paste was evaluated using macroscale three-point bending test. Correlations between the mechanical performances and microstructural characteristics revealed the performance controlling factors of the carbonation activated binders. The higher bound water contents of the carbonated matrix tend to increase the short-term (up to 3 h) creep deformation of the matrix when subjected to constant stress. The presence of a higher proportion of poorly-crystalline forms of calcium carbonates (i.e., aragonite, vaterite and amorphous calcium carbonate) were observed to increase the flexural strength but decrease the elastic modulus of the carbonated matrix.
       
  • Enhanced dynamic mechanical properties of cement paste modified with
           graphene oxide nanosheets and its reinforcing mechanism
    • Abstract: Publication date: Available online 6 July 2018Source: Cement and Concrete CompositesAuthor(s): Wu-Jian Long, Jing-Jie Wei, Feng Xing, Kamal H. Khayat The effect of graphene oxide (GO) nanosheets on the static and dynamic mechanical properties and microstructure of cement paste has been investigated. The results of dynamic mechanical testing revealed that loss factors of the pastes containing 0.05, 0.10, and 0.20 wt.% of GO were improved by 31%, 58%, and 77%, respectively. The maximum storage modulus of 52% was observed at a GO content of 0.1 wt.%, while the 28-d flexural and compressive strengths of the cement pastes with GO contents of 0.05 and 0.2 wt.% exceeded those of the control pastes by 12%–26% and 2%–21%, respectively. TGA analysis and microstructural analysis of the hardened cement pastes showed that the added GO could promote cement hydration, refine the capillary pore structure, reduce the air voids content, and improve the density of pastes. Dynamic mechanical properties reinforced mechanisms of paste incorporated with GO were also revealed based on the internal contact surfaces, porosity, and non-uniform stress distribution analysis.
       
  • Hydraulic clinkerless binder on the fluid sulfocalcic fly ash basis
    • Abstract: Publication date: Available online 5 July 2018Source: Cement and Concrete CompositesAuthor(s): František Škvára, Rostislav Šulc, Roman Snop, Adéla Peterová, Martina Šídlová Sulfocalcic fly ash (mostly called FBC fly ash) is formed when a dry process of limestone injection is applied to the desulfurization of flue gases. The hydration of sulfocalcic fly ash results in the formation of an expanding low-strength body. Its volume instability prevents its use as an admixture to the concrete. The mixing of sulfocalcic fly ash, PCC fly ash and Ca(OH)2 in a presence of a plasticizer gives the possibility to obtain a ternary binder possessing strength values comparable to those of Portland cement (PC). The ternary binder is characterized by a long-term volume stability thanks to the presence of the plasticizer based on polycarboxylates that modifies the habitus of ettringite crystals; the expansion stresses due to the ettringite modification are thus eliminated. The SEM/EDX analyses have revealed that the composition of the amorphous parts does not correspond to that of the C-S-H phase because even Al is present in this phase. It was found, the hydrated ternary binder contains an amorphous C-A-S-H phase, a crystalline ettringite phase as well as residues of crystalline phases (as mullite, quartz, hematite) from the fly ashes. The C-A-S-H phase in the hydrated ternary binder can also be characterized by 21Al MAS NMR as a geopolymer formed by alkaline activation of amorphous parts of ashes under the action of Ca(OH)2. The hydrated ternary binder is obviously similar to the Roman concrete because it contains an amorphous C-A-S-H phase. The ternary hydraulic binder would be a promising perspective for the use of the sulfocalcic fly ash that is nowadays predominantly deposit in the ash landfills.
       
  • Effect of concrete rheological properties on quality of formed surfaces
           cast with self-consolidating concrete and superworkable concrete
    • Abstract: Publication date: Available online 26 June 2018Source: Cement and Concrete CompositesAuthor(s): Wael A. Megid, Kamal H. Khayat An experimental program was undertaken to evaluate the effect of rheology of self-consolidating concrete and superworkable concrete on formed surface quality. In total, 31 mixtures with different workability and rheological properties were cast in a specially designed Z-shaped column without any mechanical consolidation. Surface defects, including surface air voids, signs of bleeding, segregation, and low filling ability were evaluated using a proposed image analysis methodology. The proposed method was successfully compared to other approaches that mainly target the detection of surface voids. Statistical models were developed between surface defect characteristics of formed surfaces cast with self-consolidating concrete and superworkable concrete and the rheological properties of the concrete. Concrete mixtures with yield stress lower than 25 Pa were found to develop superior surface finish. It was also observed that a prolonged delay in cement hydration of mixtures with yield stress lower than 50 Pa could lead to surface defects associated with bleeding. Mixtures with yield stress greater than 100 Pa exhibited considerable surface defects caused by insufficient filling ability of the concrete in the absence of mechanical consolidation. Finally, surface defects resulting from segregation were found with flowable concrete with plastic viscosity lower than 10 Pa s and yield stress lower than 100 Pa.
       
  • Multi-scale strategy for modeling macrocracks propagation in reinforced
           concrete structures
    • Abstract: Publication date: Available online 27 April 2018Source: Cement and Concrete CompositesAuthor(s): Christian Nader, Pierre Rossi, Jean-Louis Tailhan This paper introduces a new approach to model cracking processes in large reinforced concrete structures, like dams or nuclear power plants. For these types of structures it is unreasonable, due to calculation time, to explicitly model rebars and steel-concrete bonds. To solve this problem, we developed, in the framework of the finite element method, a probabilistic macroscopic cracking model based on a ulti-scale simulation strategy: the Probabilistic Model for (finite) Elements of Reinforced Concrete (PMERC).The PMERC's identification strategy is case-specific because it holds information about the local behaviour, obtained in advance via numerical experimentations.The Numerical experimentations are performed using a validated cracking model allowing a fine description of the cracking processes.The method used in the inverse analysis is inspired from regression algorithms: data on the local scale would shape the macroscopic model.Although the identification phase can be relatively time-consuming, the structural simulation is as a result, very fast, leading to a sensitive reduction of the overall computational time.A validation of this multi-scale modelling strategy is proposed. This validation concerns the analysis of the propagation of a macrocrack in a very large Double Cantilever Beam specimen (DCB specimen usually used in the framework of Fracture Mechanics studies) containing rebars. Promising results in terms of global behaviour, macrocracking information and important reduction in simulation time are obtained.
       
  • A printability index for linking slurry rheology to the geometrical
           attributes of 3D-printed components
    • Abstract: Publication date: Available online 1 April 2018Source: Cement and Concrete CompositesAuthor(s): Sabrina Ketel, Gabriel Falzone, Bu Wang, Newell Washburn, Gaurav Sant While the field of 3D-printing (3DP; formally known as additive manufacturing) has increasingly matured, its use in large-scale applications, e.g., building and infrastructure construction, remains limited. Although layer-wise slurry deposition/extrusion (LSD/E) methods are amenable to scale-up and offer versatility in terms of the materials that can be printed (i.e., “inks” that can be used), there is a lack of quantitative metrics to assess the geometrical attributes of printed components vis-à-vis their 3D-CAD (computer-aided design) inputs. To address this limitation, we present an original method to assess the external geometrical attributes of 3D-printed components using laser triangulation-based 3D-scanning. Significantly, a printability index (0 ≤ Ip ≤ 1, unitless) is presented which compares the overall geometric fidelity of the printed specimen to its CAD input. By adjusting the rheology of a model silicate-based slurry, we examine the relationships between slurry rheology, shrinkage and printability. The printability index offers a quantitative basis for assessment and quality control of 3D-printed components, while helping to develop an improved understanding of how slurry behavior, and optimizations therein can maximize printability.
       
  • Robust production of sustainable concrete through the use of admixtures
           and in-transit concrete management systems
    • Abstract: Publication date: Available online 11 January 2018Source: Cement and Concrete CompositesAuthor(s): Elise Berodier, Larry R. Gibson, Elizabeth Burns, Lawrence Roberts, Josephine Cheung The production of sustainable building materials, such as concrete, has drawn more and more attention in the last decade. Breakthroughs in the development of new admixtures, new mix designs, new concrete management systems, together with deeper understanding on the best-mode usage of admixtures with different cementitious materials have resulted in production of sustainable concrete with better performance at a lower cost. This paper reviews the latest mechanistic understanding on how admixtures interact with cement and cementitious materials, real-world examples on current practical challenges faced by concrete producers, and an example on the advances allowed by the use of transformational technologies for improved concrete management systems. We also highlight new technical challenges and conditions to investigate these gaps in hope to better coordinate research efforts critical to the industry.
       
 
 
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