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  Subjects -> ENGINEERING (Total: 2515 journals)
    - CHEMICAL ENGINEERING (210 journals)
    - CIVIL ENGINEERING (219 journals)
    - ELECTRICAL ENGINEERING (120 journals)
    - ENGINEERING (1320 journals)
    - ENGINEERING MECHANICS AND MATERIALS (403 journals)
    - HYDRAULIC ENGINEERING (57 journals)
    - INDUSTRIAL ENGINEERING (84 journals)
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CIVIL ENGINEERING (219 journals)                  1 2 | Last

Showing 1 - 200 of 219 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: 43)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 34)
Agregat     Open Access   (Followers: 1)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 36)
Architectural Engineering     Open Access   (Followers: 5)
Architecture and Engineering     Open Access  
Architecture, Civil Engineering, Environment     Open Access   (Followers: 1)
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 3)
Archives of Civil Engineering     Open Access   (Followers: 13)
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: 6)
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: 16)
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: 14)
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: 10)
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: 19)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Architecture     Open Access   (Followers: 24)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 13)
Civil Engineering Dimension     Open Access   (Followers: 12)
Civil Engineering Infrastructures Journal     Open Access   (Followers: 1)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 291)
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  
Construindo     Open Access  
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: 3)
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)
Gaceta Técnica     Open Access  
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: 36)
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   (Followers: 1)
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 16)
Journal of Civil Engineering and Management     Open Access   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 10)
Journal of Civil Engineering Research     Open Access   (Followers: 8)
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: 79)
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: 18)
Journal of Construction Engineering, Technology & Management     Full-text available via subscription   (Followers: 4)
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: 6)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 8)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 9)
Journal of Offshore Structure and Technology     Full-text available via subscription  
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: 4)
Journal of Road and Traffic Engineering     Open Access  
Journal of Solid Waste Technology and Management     Full-text available via subscription   (Followers: 1)
Journal of Structural Engineering     Full-text available via subscription   (Followers: 36)
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: 4)
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   (Followers: 2)
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)
Lithosphere     Open Access  
Materiales de Construcción     Open Access   (Followers: 1)
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 5)
Media Komunikasi Teknik Sipil     Open Access  
Media 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: 4)
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)
REDER : Revista de Estudios Latinoamericanos sobre Reducción del Riesgo de Desastres     Open Access  
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 6)
Resilience     Open Access   (Followers: 1)
Revista de Investigación     Open Access  
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)

        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  [3157 journals]
  • Effect of particle size of nanosilica on microstructure of C-S-H and its
           impact on mechanical strength
    • Abstract: Publication date: Available online 14 January 2019Source: Cement and Concrete CompositesAuthor(s): U. Sharma, L.P. Singh, Baojian Zhan, Chi Sun Poon The present work is focused on the effect of particle size of silica on its early age reactivity and its impact on C-S-H microstructure and mechanical strength at the early and later ages of hydration. Two different types of commercially available silica i.e. Elk-microsilica (Elk-Si) (100–300 nm) and colloidal nanosilica (CNS) (8–15 nm) were used for the study. The lime silica reaction was carried out with a C/S ratio 2.0 and the reaction was monitored in the first 24 h with a range of instrumentation techniques. The results showed that the CNS had ∼60% higher reactivity than the Elk-nSi. Calorimetric results revealed that in the presence of CNS, the hydration rate and the formation of AFm phase were accelerated. Furthermore, FTIR and NMR results revealed that in the presence of the CNS, the structure of C-S-H gel was also affected. This acceleration and modification C-S-H gel led to the formation of a compact microstructure as the capillary porosity of cementitious system measured by MIP was found to reduce significantly. The formation of a compact microstructure at the early age of hydration improved the early age mechanical strength. However, it hindered the later age hydration and thus more unhydrated cement was observed in the semi-quantitative XRD and BSE/IA analysis, especially in the presence of higher dosages of CNS, which was responsible for the lower long term mechanical strength.
       
  • Methodology of obtaining intrinsic creep property of concrete by flexural
           deflection test
    • Abstract: Publication date: Available online 11 January 2019Source: Cement and Concrete CompositesAuthor(s): Siming Liang, Ya Wei The shrinkage of concrete when exposed to external drying influences the accurate quantification of concrete creep. To reduce the effect of shrinkage on the measured creep, particularly for concrete at early ages when the shrinkage is pronounced, a flexural creep test set-up was designed in this study to investigate the creep property of concrete beams with w/c ratios of 0.3 and 0.4 at the age of 7 days. The concrete beams were exposed to both sealed and drying conditions. A sequential coupled hydromechanical finite element analysis was conducted to back-calculate the creep parameters in the original microprestress solidification theory-based creep model from the measured creep-induced deflection. The results show that the flexural creep test is capable of obtaining the intrinsic creep property of concrete without incorporating the shrinkage effect as long as the relative humidity distribution in the concrete beams is symmetric about the neutral plane. The intrinsic creep property depends only on the mixture proportions of concrete, i.e., it is independent of the loading and drying conditions, which can be used to predict the deflection development of concrete beam under other complex drying conditions. The findings in this study provide a new methodology of obtaining concrete creep, which solves the problem of the conventional uniaxial creep testing method that both creep strain and shrinkage strain need to be measured during the creep test.
       
  • Tensile properties of plastic concrete and the influence of temperature
           and cyclic loading
    • Abstract: Publication date: Available online 11 January 2019Source: Cement and Concrete CompositesAuthor(s): Riaan Combrinck, William P. Boshoff The cracking of plastic concrete remains a problem in the construction industry due to its complexity and incomplete understanding. One of the reasons for this is the lack of knowledge regarding the tensile material properties of the plastic concrete. This paper describes and builds the appropriate test setup needed for the challenging tensile testing of plastic concrete as well as discusses the measured tensile properties. The tensile strength and Young's modulus increase exponentially near the final setting time and initial setting time respectively. The strain capacity and initial fracture energy decrease significantly between the initial and final setting times. The tensile properties develop faster and with higher values the greater the ambient temperature. Plastic concrete proved to be resilient and capable of withstanding multiple loading and ceased loading cycles, while a solid but still weak concrete could not. The tests also highlighted the need for further research regarding the influence of hydrostatic pressure and the relaxation of stresses in plastic concrete.
       
  • Radiation shielding properties of mortars with minerals and ores additives
    • Abstract: Publication date: Available online 10 January 2019Source: Cement and Concrete CompositesAuthor(s): H. Baltas, M. Sirin, A. Celik, İ. Ustabas, A.M. El-Khayatt Incorporation of mineral and ores as fine aggregate additives was investigated for its effect on the neutron and gamma-ray shielding properties of cement mortar. Five mortar mixtures have been prepared with different proportions of additives ranging from 0% to 30% of the cement mass by weight. Evaluation of gamma-ray attenuation was both measured experimentally and computed by means of a software. The measurements have been carried out for ores and mortar samples using 59.54, 662 and 1332 keV gamma photons. The theoretical values have been calculated in the energy range from 10 keV to 1 GeV. Many shielding parameters such as mass attenuation coefficient (μ/ρ), effective atomic number (Zeff) and corresponding electron density (Neff) and gamma–ray kerma coefficients (kγ) have been determined. The calculated values are in good agreement with the observed values. Furthermore, the macroscopic fast neutron removal cross-sections (ΣR, cm−1) have also been calculated by means of a software. The results of this study showed that the gamma-ray and neutron attenuation parameters of the studied mortar samples do not display any significant variation due to the addition of ores and minerals at the investigated mixing proportion (30% of the cement mass by weight).
       
  • Air permeability assessment of corrugated fiber-cement roofing sheets
    • Abstract: Publication date: Available online 9 January 2019Source: Cement and Concrete CompositesAuthor(s): Murilo Daniel de Mello Innocentini, Marcelina Aparecida Vieira de Faria, Murilo Rosseto Crespi, Victor Hugo Batista Andrade The air permeability of full-sized commercial corrugated fiber-cement roofing sheets was assessed by two non-destructive experimental methods. Unlike the technical standards that recommend only visual verification of water impermeability or the laboratory tests that rely on the extraction of samples for airflow analysis, the methods described in this work allowed to obtain permeability parameters of crests and troughs everywhere in the sheet without damage. The permeability coefficients, retrieved from Forchheimer's equation, varied two orders of magnitude for k1 (4.65 × 10−17 m2–2.94 × 10−15 m2) and almost 6 orders of magnitude for k2 (7.02 × 10−16 m–1.07 × 10−10 m) along lateral and longitudinal positions in the sheet. Crests were more permeable for downward flow while troughs were more permeable for upward flow. The flow anisotropy was related to the peculiarities of the Hatschek process. The pressure-decay technique allowed a much faster data acquisition compared to the conventional steady-state permeametry.
       
  • Effect of non-adsorbed superplasticizer molecules on fluidity of cement
           paste at low water-powder ratio
    • Abstract: Publication date: Available online 8 January 2019Source: Cement and Concrete CompositesAuthor(s): Kazuki Matsuzawa, Daiki Shimazaki, Hirokatsu Kawakami, Etsuo Sakai Non-adsorbed superplasticizer molecules increase the fluidity of cement paste with low water-powder ratio, but their function is unclear. The authors used superplasticizers having different molecular structures to investigate the influence of non-adsorbed superplasticizer on the fluidity of cement paste. The paste consisted of low-heat Portland cement, ultra-fine silica particle, and polycarboxylate-based superplasticizer solution. First, a superplasticizer having moderate molecular length was added to the paste, and the adsorption saturated. Subsequently, another superplasticizer was added to the paste. The subsequent additions of shorter superplasticizers decreased the adsorption of the first superplasticizer but the fluidity did not change. The subsequent additions of moderately long superplasticizers did not change the adsorption but increased the fluidity. In contrast, the subsequent additions of longer superplasticizers decreased the fluidity. The authors consider that the fluidity is related to the size of the subsequent superplasticizer, i.e. small superplasticizer molecules intercalate between the particles and aid in dispersion.
       
  • Performance-based design of all-grade strain hardening cementitious
           composites with compressive strengths from 40 MPa to 120 MPa
    • Abstract: Publication date: Available online 7 January 2019Source: Cement and Concrete CompositesAuthor(s): Linzhi Li, Ziwei Cai, Kequan Yu, Y.X. Zhang, Yao Ding A systematic study of the tensile properties of all-grade strain hardening cementitious composite (SHCC) from normal strength to high strength was conducted in the present research. The compressive strengths of the cylinder specimens ranged from 43 MPa to 115 MPa. Different combinations of fiber volume fractions and fiber aspect ratios (fiber length/diameter) were employed to investigate the effects of the fiber reinforcement index (the product of fiber volume fraction and fiber aspect ratio) on the tensile properties of SHCC, including mechanical properties and crack patterns. The relationships between the fiber reinforcement index and tensile properties were established at all compressive strengths and compared with the previous experimental values. Moreover, a performance-based design concept was proposed for designing SHCC based on the required mechanical and crack pattern properties, corresponding to the ultimate limit state and serviceability limit state, respectively.
       
  • Shrinkage and strength development of UHSC incorporating a hybrid system
           of SAP and SRA
    • Abstract: Publication date: Available online 3 January 2019Source: Cement and Concrete CompositesAuthor(s): Jianhui Liu, Nima Farzadnia, Caijun Shi, Xianwei Ma The individual use of super-absorbent polymer (SAP) or shrinkage reducing admixture (SRA) impairs some properties required for ultra-high strength concrete (UHSC). This study used SAP and SRA in hybrid systems in order to enhance their role on autogenous shrinkage, drying shrinkage and compressive strength of UHSC. Accordingly, the water absorption and the surface tension of pore solution containing the hybrid system of SAP and SRA were measured, and the effect on internal relative humidity (RH), porosity and hydration degree were examined. The results showed that the interaction of SAP and SRA reduced the water absorption capacity of SAP and limited the reducing effect of SRA on the surface tension. However, the hybrid system of SAP and SRA compensated the adverse effect of each on the properties of UHSC. It was also found that the surface tension of pore solution was more effective than the internal RH on the autogenous shrinkage of UHSC. Overall, the specimens with 0.3% SAP and 2% SRA had the minimum autogenous and drying shrinkage.
       
  • Fracture response of metallic particulate-reinforced cementitious
           composites: Insights from experiments and multiscale numerical simulations
           
    • Abstract: Publication date: Available online 3 January 2019Source: Cement and Concrete CompositesAuthor(s): Sumeru Nayak, N.M. Anoop Krishnan, Sumanta Das This paper presents an experimental and numerical investigation into the fracture response of mortars containing up to 30% waste iron powder by volume as OPC-replacement. The iron powder-modified mortars demonstrate significantly improved strength and fracture properties as compared to the control mortars due to presence of elongated iron particulates in the powder. With a view to develop a predictive tool towards materials design of such particulate-reinforced systems, fracture responses of iron powder-modified mortars are simulated using a multiscale numerical approach. The approach implements multi-scale numerical homogenization involving cohesive zone-based damage at the matrix-inclusion interface and isotropic damage in the matrix to obtain composite constitutive response and fracture energy. Consequently, these results serve as input to macro-scale XFEM-based three-point-bend simulations of notched mortar beams. The simulated macroscopic fracture behavior exhibit excellent match with the experimental results. Thus, the numerical approach links the material microstructure to macroscopic fracture parameters facilitating microstructure-guided material design.
       
  • The effectiveness of different superplasticizers in ambient cured one-part
           alkali activated pastes
    • Abstract: Publication date: Available online 3 January 2019Source: Cement and Concrete CompositesAuthor(s): Yazan Alrefaei, Yan-Shuai Wang, Jian-Guo Dai This paper investigates the effect of using different admixtures on the one-part ambient-cured alkali activated pastes. Na2SiO3-Anhydrous powder was used as solid activator along with three superplasticizers including naphthalene, melamine and polycarboxylate with different water/precursor ratios. The flowability, setting time and compressive strength development were evaluated for all AAMs mixes. ATR-FTIR test was used to check the admixtures stability in high alkali media.All types of admixtures significantly improved the flowability of the Na2SiO3-anhydrous one-part AAMs and marginally affected the compressive strength. The results showed that polycarboxylate was effective for high water/precursor (≥0.36) while naphthalene performed better in case of low water/precursor (≤0.36) for Na2SiO3-anhydrous one-part AAMs. However, lowering the water/precursor ratio in the Na2SiO3-anhydrous one-part AAMs using superplasticizers showed no improvement or modest improvement in the compressive strength. The ATR-FTIR results revealed the relatively high stability of admixtures in Na2SiO3 alkali medium of one-part AAMs (for w/b = 0.4).
       
  • Mechanical properties of high ductile magnesium oxychloride cement-based
           composites after water soaking
    • Abstract: Publication date: Available online 3 January 2019Source: Cement and Concrete CompositesAuthor(s): Yichao Wang, Linzhuo Wei, Jiangtao Yu, Kequan Yu Applications of magnesium oxychloride cement-based concrete in civil engineering are limited due to material's poor water resistance and inherent brittleness. For improvement, a new kind of material, magnesium oxychloride cement-based engineered cementitious composite (MOC-ECC), was developed. This paper introduces the effects of fly ash and polyethylene fibers incorporations on the fluidity, tensile behavior and compressive properties of MOC-ECC. The test results indicated that MOC-ECC exhibits outstanding strain hardening and multi-cracking characteristics with tensile strain capacity up to 8% and tensile strength over 7 MPa. More importantly, to explore the combined influences of fly ash and polyethylene fiber on the water resistance of MOC-ECC, XRD and SEM were used to analyze the variations of chemical composition and microstructure, and three-point bending test and single crack tension test were conducted to obtain the fracture toughness and fiber bridging capacity, respectively. An explanation to the mechanisms of the enhanced mechanical property and water resistance is presented at microscopic and mesoscopic scales.
       
  • Insights into the physical and chemical properties of a cement-polymer
           composite developed for geothermal wellbore applications
    • Abstract: Publication date: Available online 31 December 2018Source: Cement and Concrete CompositesAuthor(s): Kenton A. Rod, Manh-Thuong Nguyen, Mohamed Elbakhshwan, Simerjeet Gill, Barbara Kutchko, Tamas Varga, Adriana M. Mckinney, Timothy J. Roosendaal, M. Ian Childers, Chonghang Zhao, Yu-chen Karen Chen-Wiegart, Juergen Thieme, Phillip K. Koech, Wooyong Um, Jaehun Chun, Roger Rousseau, Vassiliki-Alexandra Glezakou, Carlos A. Fernandez To isolate injection and production zones from overlying formations and aquifers during geothermal operations, cement is placed in the annulus between well casing and the formation. However, wellbore cement eventually undergoes fractures due to chemical and physical stress with the resulting time and cost intensive production shutdowns and repairs. To address this difficult problem, a polymer-cement (composite) with self-healing properties was recently developed by our group. Short-term thermal stability tests demonstrated the potential of this material for its application in geothermal environments. In this work, the authors unveil some of the physical and chemical properties of the cement composite in an attempt to better understand its performance as compared to standard cement in the absence of the polymer. Among the properties studied include material's elemental distribution, mineral composition, internal microstructure, and tensile elasticity. Polymer-cement composites have relatively larger, though not interconnected, levels of void spaces compared to conventional cement. Most of these void spaces are filled with polymer. The composites also seem to have higher levels of uncured cement grains as the polymer seems to act as a retarder in the curing process. The presence of homogeneously-distributed more flexible polymer in the cement brings about 60–70% higher tensile elasticity to the composite material, as confirmed experimentally and by density-functional calculations. The improved tensile elasticity suggests that the composite materials can outperform conventional cement under mechanical stress. In addition, calculations indicate that the bonding interactions between the cement and polymer remain stable over the range of strain studied. The results suggest that this novel polymer-cement formulation could represent an important alternative to conventional cement for application in high-temperature subsurface settings.
       
  • Comparative pullout behaviors of half-hooked and commercial steel fibers
           embedded in UHPC under static and impact loads
    • Abstract: Publication date: Available online 30 December 2018Source: Cement and Concrete CompositesAuthor(s): Doo-Yeol Yoo, Soonho Kim This study investigates the pullout behaviors of various steel fibers embedded in ultra-high-performance concrete (UHPC) under static and impact loading conditions. For this purpose, four types of steel fibers, i.e., straight, hooked, twisted, and half-hooked, and three different loading rates applied by static and impact pullout test machines were adopted. To examine the effects of the inclination angle on the pullout behavior, four different inclination angles of 0°, 30°, 45°, and 60° were considered. Test results indicate that the highest average bond strengths were found for the hooked and twisted fibers for static and impact loads, respectively, whereas the straight fibers exhibited the lowest bond strength at all inclination angles. The effectiveness of using half-hooked fibers increased when they were inclined, and maximized at an inclination angle of 45° compared to straight and highly deformed fibers. The use of the twisted and half-hooked fibers was also more effective in static pullout energies than the hooked and straight fibers. The pullout resistance of all the steel fibers in UHPC was improved under impact loading conditions, and the order of the loading rate effectiveness regarding both the average bond strength and pullout energy was as follows: straight fibers > half-hooked fibers > twisted fibers > hooked fibers. The change in the failure mode from pullout to rupture, due to the increase in the loading rate, adversely affected the rate sensitivity of the bond strength and energy absorption capacity. Since the deformed steel fibers were easily ruptured under impact loads, their failure by rupture needs to be prevented to achieve an excellent bond strength and energy absorption capacity.
       
  • Sustainable and efficient cork - inorganic polymer composites: An
           innovative and eco-friendly approach to produce ultra-lightweight and low
           thermal conductivity materials
    • Abstract: Publication date: Available online 30 December 2018Source: Cement and Concrete CompositesAuthor(s): Rui M. Novais, Luciano Senff, João Carvalheiras, Maria P. Seabra, Robert C. Pullar, João A. Labrincha In this investigation cork was used as a low density aggregate in the production of ultra-lightweight and low thermal conductivity inorganic polymer (geopolymer) composites. This novel and highly sustainable material, synthesised at room temperature (23 °C), may decrease the energy losses inside buildings, thus contributing to the United Nations development goals regarding energy and climate change. The ultra-low density (260 kg/m3) and low thermal conductivity (72 mW/m K) shown by the cork-composites are the second lowest ever reported for inorganic polymer composites, only being surpassed by that of polystyrene-inorganic polymer composites. However, cork is a fully renewable and sustainable resource, while polystyrene is manufactured from non-renewable fossil fuels, and for that reason our strategy has an additional sustainability advantage. Moreover, the cork-inorganic polymer composites do not release any toxic fume when under fire conditions, which is a major advantage over polymeric-based foams.
       
  • Mechanism for rapid hardening of cement pastes under coupled
           CO2-water curing regime
    • Abstract: Publication date: Available online 28 December 2018Source: Cement and Concrete CompositesAuthor(s): Zhan Bao Jian, Xuan Dong Xing, Poon Chi Sun, Shi Cai Jun A coupled CO2-water curing regime was employed on Ordinary Portland cement (OPC) paste samples immediately after casting, which allowed carbonation and hydration of OPC to proceed simultaneously. The strength development and microstructural evolution was evaluated by using multiple-techniques. The results indicated that, compared to the normal hydrated counterpart, a lower porosity, higher amorphous phase content and overall reaction degree can be achieved in the coupled CO2-water cured OPC sample. By combining with the morphological observations, a new mechanism was proposed for the rapid hardening of OPC. It is shown that the carbonation reactions led to the formation of calcite particles, which provided more nucleating sites for CSH gel growth; and thus, an increase in the overall reaction degree of the cement paste can be achieved within the first 24 h compared to the conventional water curing process.Graphical abstractImage 1
       
  • Cr-modified low alloy steel reinforcement embedded in mortar for two
           years: Corrosion result of marine field test
    • Abstract: Publication date: Available online 26 December 2018Source: Cement and Concrete CompositesAuthor(s): Yuwan Tian, Ming Liu, Xuequn Cheng, Chaofang Dong, Gui Wang, Xiaogang Li This paper describes a study of the corrosion behavior of Cr-modified steel reinforcement exposed at marine splash zone for a period of two years. The corrosion behavior was analyzed by the weight loss method, optical and electron microscopy, and X-ray photoelectron spectroscopy. The Cr-modified reinforcement exhibited high corrosion resistance in the actual marine environment. The protection mechanism of the Cr-modified reinforcement at the corrosion propagation stage was that Cr improved the protective quality and buffering ability of the rust layer against aggressive species, by increasing the Fe2+ and OH− content within the iron oxides and improving the compact degree of the rust layer.
       
  • Three-dimensional shape characterization of fine sands and the influence
           of particle shape on the packing and workability of mortars
    • Abstract: Publication date: Available online 25 December 2018Source: Cement and Concrete CompositesAuthor(s): Pierre Estephane, Edward J. Garboczi, Jeffrey W. Bullard, Olafur H. Wallevik This paper studies a selection of fine sands, their particle shape and its effect on the plastic properties of mortars via the influence on the workability and packing of cementitious mixtures. Five sands from different sources were sampled, wet sieved, and classified into six size classes: 20 μm–75 μm, 75 μm–150 μm, 150 μm–300 μm, 300 μm–600 μm, 600 μm to 1.18 mm and 1.18 mm–2.36 mm. Particle shape was measured and various geometrical quantities were determined for particles of each class using a combination of X-ray microcomputed tomography (μCT) and spherical harmonic analysis. Specimen preparation, scanning method, minimum required number of particles in a representative sample, and shape histograms are all discussed, and used to classify and compare the shape of the particles of each material type and size class. This information is then used to establish a connection between sand particle shape and the wet packing density, the workability in the form of slump-flow, and the water demand in mortar mixtures.
       
  • Pore structure of affected zone around saturated and large superabsorbent
           polymers in cement paste
    • Abstract: Publication date: Available online 25 December 2018Source: Cement and Concrete CompositesAuthor(s): Jin Yang, Fazhou Wang, Xingyang He, Ying Su Superabsorbent polymer (SAP) has been widely used as internal curing agent for cement-based materials, duo to its high internal curing efficiency. Pore structure of affected zone around SAP is important for understanding the internal curing mechanism. This paper presents a study of the pore structure evolution of affected zone around SAP in cement paste with water/cement ratio 0.24 and 0.30 from 3 up to 28 days. Pore structure of affected zone and matrix was tested by mercury intrusion porosimetry and nitrogen adsorption and desorption. Surface fractal dimensions were determined using two different fractal models. Results indicated that SAP had no effect on the pore shape of affected zone, excluding the pore volume and pore diameter at early and late ages. Higher critical pore diameter but lower pore volume were found in affected zone at late ages. All the samples showed a multi-fractal property at micro- and macro-fractal scale, and the surface fractal dimension of affected zone was always larger than the matrix, showing a higher pore complexity. Some new findings on internal curing were achieved from an affected zone perspective. The calculated mechanical strength and permeability of affected zone from the pore structure parameters were found higher than the matrix. These new findings may give insight into the effect of internal curing with SAP from the perspective of affected zone.
       
  • Capillary absorption of cracked strain-hardening cement-based composites
    • Abstract: Publication date: Available online 23 December 2018Source: Cement and Concrete CompositesAuthor(s): Christian Wagner, Beate Villmann, Volker Slowik, Viktor Mechtcherine Cracks in strain-hardening cement-based composites (SHCC) will significantly influence the capillary absorption of the material when its surface is exposed to water. An analysis model is presented which is based on the decomposition of the absorbed water volume into three portions: water absorbed by the outer surface, water filling the cracks, and water absorbed by the crack surfaces. The crack pattern in SHCC, normally consisting of numerous fine cracks, affects these three water absorption portions in different ways. In order to quantify the contributions of the cracks, appropriate crack pattern parameters have been defined and used for developing the analysis model. For parameter identification and model verification, water absorption tests of uncracked, cracked, and fractured SHCC surfaces were conducted. In addition, the water absorption of thin slices made of SHCC was measured to adequately consider the influence of the crack spacing distribution in the model. The prediction of the capillary absorption by means of the model is based on the actual crack pattern observable at the respective SHCC surface. Since these surface cracks do not necessarily continue throughout the entire cross-section of the specimen, the model tends to overestimate the capillary absorption. Accordingly, the deviation from the measured values becomes smaller with decreasing specimen depth.
       
  • The role of porosity in external sulphate attack
    • Abstract: Publication date: Available online 22 December 2018Source: Cement and Concrete CompositesAuthor(s): Tai Ikumi, Sergio H.P. Cavalaro, Ignacio Segura Design codes promote a limitation of permeability (indirectly of porosity) to reduce the sulphate ingress and improve the resistance of concrete and mortar to external sulphate attack (ESA). However, porosity could also have a positive effect on durability by generating additional space to accommodate the expansive phases. The aim of this study is to evaluate the role of porosity in ESA. For that, changes at the macro-scale, phase composition and pore network are monitored for mortar compositions with different pore-size distribution. Results indicate the existence of two mechanisms: the capacity to accommodate expansive phases controls the durability during the initial stages of the attack, while at later stages durability is defined by the permeability. Results from specimens with air-entrainer suggest that the intentional increase of porosity towards maximising the capacity to accommodate expansive products might be a valid approach in order to reduce the expansive forces generated during ESA.
       
  • The effect of concrete alkalinity on behavior of reinforcing polyester and
           polypropylene fibers with similar properties
    • Abstract: Publication date: Available online 21 December 2018Source: Cement and Concrete CompositesAuthor(s): Rohallah Rostami, Mohammad Zarrebini, Mansoor Mandegari, Khaled Sanginabadi, Davood Mostofinejad, Sayyed Mahdi Abtahi The use of fiber reinforced concrete (FRC) has received wide attention in recent years. Alkalinity affects polyethylene terephthalate (PET) fibers. Therefore, the use of PET fibers in an alkaline environment such as concrete is faced with uncertainties. In this work, three types of PET and polypropylene (PP) fibers with similar physical and mechanical properties were used as concrete reinforcement. In order to simulate the alkaline environment of concrete, hydrolysis of PET and PP fibers was carried out in 60 °C solution of NaOH 10% at pH = 14 for 1, 2, and 4 h duration. Fiber properties such as diameter, mechanical properties and moisture regain both before and after being subjected to alkaline hydrolysis were measured. Probable degradation of the fibers due to alkaline hydrolysis was evaluated using SEM and FTIR. The fibers were used in concrete at the same fiber volume fraction of 0.55%. FRCs were cured for 28 days and compressive, tensile and flexural strength were measured. Results showed that in initial stages of alkaline treatment severe weight loss of PET fibers occurred but beyond a certain time the rate of weight loss increased, slows down. Although mechanical properties of PET fibers in alkaline environment deteriorated due to weight reduction phenomenon, but results in generation of advantages such as hydrophilicity and creation of dimples on the surface of the treated fibers that enhanced adhesion properties of the fiber-matrix.
       
  • 3D printable concrete: Mixture design and test methods
    • Abstract: Publication date: Available online 21 December 2018Source: Cement and Concrete CompositesAuthor(s): A.V. Rahul, Manu Santhanam, Hitesh Meena, Zimam Ghani The current study deals with a yield stress based mixture design approach for 3D printable concretes. The mixtures were evaluated based on buildability, extrudability, robustness and tests for structural build-up. For the print parameters (such as pump type, nozzle size and extrusion velocity) used in the study, it was found that both extrudability and buildability could be achieved only when the material yield stress was within a range of 1.5–2.5 kPa. Below this range, the material lacked enough strength to achieve shape stability, while above this range, the extrudabilty of the material was difficult. The robustness of the mixtures was quantified in terms of a variability factor defined in terms of the variation in yield stress with small changes in the superplasticizer dosage. Inclusion of 10% of silica fume, 0.1% of viscosity modifying agent (VMA) and 0.1–0.3% addition of nanoclay resulted in decreasing the variability factor, hence improving the robustness. The structural changes due to thixotropy and cement hydration increased the yield stress with time. This structural build-up was assessed by measuring the yield stress with increasing rest duration. The mixture with silica fume showed the maximum structural build-up while the mixture with VMA showed the least. Heat curves from semi-adiabatic calorimetry and penetration curves were also used to assess the structural build-up. They showed a similar trend to that of the yield stress vs time plots.
       
  • Chloride binding of cement pastes with fly ash exposed to CaCl2 solutions
           at 5 and 23 °C
    • Abstract: Publication date: Available online 19 December 2018Source: Cement and Concrete CompositesAuthor(s): Chunyu Qiao, Prannoy Suraneni, Nathalene Wei Ying Then, Antara Choudhary, Jason Weiss In cementitious materials exposed to solutions containing chloride, chloride binding typically results from the chemical reactions between chloride ions and aluminate phases to form Friedel's salt, and the interaction between chloride ions and calcium silicate hydrates (CSH). Calcium oxychloride can also form when Ca(OH)2 in cementitious materials reacts with CaCl2 solutions. This paper examines the chloride binding of hydrated cement pastes containing fly ash exposed to CaCl2 solutions of varying concentrations at 5 and 23 °C. Thermogravimetric analysis was used to quantify the chloride binding associated with Friedel's salt and calcium oxychloride. The amount of bound chloride by Friedel's salt is relatively independent of the exposure temperature, and as the chloride concentration [Cl−] increases, it increases until a plateau is reached at [Cl−] greater than 2 M. The addition of fly ash results in an increase in the chloride binding due to Friedel's salt. A lower exposure temperature leads to a greater amount of bound chloride associated with calcium oxychloride. In this study, no chloride binding associated with calcium oxychloride was observed in the cement pastes with 40% and 60% fly ash. The temperature-dependent chloride binding associated with CSH is a significant portion of the total chloride binding (19.8 %–70.8%) when cement pastes are exposed to CaCl2 solutions. As the replacement level of fly ash increases, the chloride binding by CSH increases first and then decreases. The amount of bound chloride by CSH increases linearly as the pH of the exposure solution decreases.
       
  • Modifications of basic-oxygen-furnace slag microstructure and their effect
           on the rheology and the strength of alkali-activated binders
    • Abstract: Publication date: Available online 18 December 2018Source: Cement and Concrete CompositesAuthor(s): Pavel Leonardo Lopez Gonzalez, Rui M. Novais, Joao Labrincha, Bart Blanpain, Yiannis Pontikes Microstructure tailoring of metallurgical slags allows the production of alternative construction binders with customized properties. In this study, the variations of rheology and strength of alkali-activated basic-oxygen-furnace (BOF) slags are quantified. Two modifications of BOF slag were created adding amounts of alumina and silica at high temperature (>1250 °C). The additions, defined by thermodynamic modeling, lowered the liquidus temperature facilitating the generation of amorphous when the slag was fast cooled. The first modification (SAT1) incorporated 5 wt% silica and 11 wt% alumina, while the second (SAT2) included around 13 wt% alumina. Both modifications generated a hybrid microstructure composed of cementitious and non-cementitious crystalline phases and an amorphous fraction. During alkali activation using NaOH solutions of 0.25 M, rheological measurements on fresh paste using SAT2 registered plastic viscosity values 2.3 times higher than those of SAT1. The compressive strength after 28 days for the binder developed from SAT2 slag was 10–30% stronger than the one from SAT1. These binders showed similar crystalline reaction products but compositional differences in the amorphous gel correlated to the initial slag modification. The detected differences in the binder properties are significant enough to justify BOF-slag engineering as a way to deliver customized precursors for alkali activation.
       
  • Performance of oxygen/argon plasma-treated steel fibres in cement mortar
    • Abstract: Publication date: Available online 18 December 2018Source: Cement and Concrete CompositesAuthor(s): Hugh D. Miller, Ali Akbarnezhad, Sara Mesgari, Stephen J. Foster Steel fibres are used widely to control initiation and growth of cracks in concrete. However, the bond between steel fibres and the cement matrix in steel fibre-reinforced concrete (SFRC) is almost always purely physical. A viable approach to reduce cracking in fibre-reinforced concrete is to supplement the physical bond between fibres and cement matrix with a relatively uniform chemical bond along the fibres' surface. However, despite the promising results reported for other types of fibres, little attention has been paid to chemical surface treatment of steel fibres to improve their ability to bond with concrete. In this study, an oxygen/argon plasma treatment process is investigated as a potential technique to improve the bond between steel fibres and a cementitious matrix. Several variations in treatment parameters are made in order to identify the optimal treatment conditions. The results of X-ray Photoelectron Spectroscopy and surface energy measurements confirm that plasma treatment can significantly increase the fibres’ surface energy and consequently the strength of the fibre-cement bond. The improved bond between steel fibres and concrete is confirmed by the results of fibre pull-out tests, as well as the reduced average crack size observed in restrained drying shrinkage tests. Moreover, the results indicate considerable decrease in the volume of permeable voids in SFRC due to plasma treatment of steel fibres.
       
  • Bioinspired design of architected cement-polymer composites
    • Abstract: Publication date: Available online 17 December 2018Source: Cement and Concrete CompositesAuthor(s): Jessica A. Rosewitz, Habibeh Ashouri Choshali, Nima Rahbar Recent advances in the design of structural composites often mimic natural microstructures. Specifically, the structure of abalone nacre with its high stiffness, tensile strength, and toughness is a source of inspiration from the process of evolution. The inspiration from nacre can lead to design of a new class of architected structural materials with superb mechanical properties. This work presents a combined experimental and computational study on a set of bioinspired architected composites created using a cement mortar cast with brick-and-mortar and auxetic polymer phases. The impact of this unit-cell polymer phase on the flexural and compressive strengths, resilience, and toughness is thoroughly studied as a function of architected geometry. All mechanical properties of the architected composite specimens are found to be greater than those of control samples due to prevention of localized deformation and failure, resulting in higher strength. The architected composites showed more layer shear sliding during fracture, whereas the control samples showed more diagonal shear failure. After initial cracking, the architected composites gradually deformed plastically due to interlocking elements and achieved high stresses and strains before failure. Results also show that composites with the architected polymer phase outperform control samples with equal volume fraction of a randomly oriented polymer fiber phase. Extensive computational studies of the proposed unit cells are also performed and the results suggest that the orientation of cells during loading is critical to achieve maximum performance of a cementitious composite. The implications of these results are immense for future development of high performing construction materials.
       
  • Modelling the transport of chloride and other ions in cement-based
           materials
    • Abstract: Publication date: Available online 17 December 2018Source: Cement and Concrete CompositesAuthor(s): M. Fenaux, E. Reyes, J.C. Gálvez, A. Moragues Research on mechanisms of chloride ion transport in cement-based materials is relevant to improve the durability of reinforced concrete structures. Conventional chloride-transport models consider a linear diffusion equation, only valid for fully saturated and non-reactive concrete. This work proposes a model of chloride and other ions penetration in saturated concrete considering diffusion, chloride binding, chemical activity and migration. The model uses intrinsic diffusion coefficients. The influence of the ionic pore solution on chloride penetration into concrete is also studied. Chemical activity is introduced by coupling the transport equations to the Pitzer model. The migration is accounted for by imposing the electro-neutrality condition of the pore solution. It is shown that fitting the well known error function to experimentally obtained chloride profiles present results which are difficult to interpret. Moreover, it is shown that, by accounting for solely diffusion and chloride binding, good results are obtained. Contemplating chemical activity and migration slightly improves such results and allows concentration profiles of the present ionic species in the pore solution to be determined. Such profiles are involved in the degradation processes of cement-based materials exposed to aggressive environments.
       
  • A new physical model for empirical fiber snubbing effect in cementitious
           composites based on large deflection beam theory
    • Abstract: Publication date: Available online 15 December 2018Source: Cement and Concrete CompositesAuthor(s): Jie Yao, Christopher K.Y. Leung A single fiber crosses a crack in Strain-Hardening Cementitious Composites (SHCC) can be either perpendicular or inclined to the crack surface. When the single fiber pullout test is performed on inclined polymeric fibers, the peak pull-out load is commonly observed to increase with the inclination angle. Usually the fiber is modeled as a flexible string passing over a frictional pulley, and the observed phenomenon is explained by the high local friction (or snubbing effect) near the fiber exiting point. However, such an explanation is not perfectly satisfactory because the bending stiffness of the fiber is not necessarily negligible and the pulley does not physically exist. In this study, a new model which treats the fiber as a beam and emphasize on the large deflection effect of the fiber is developed. The entire fiber bridging stress vs crack opening relationship can be derived and the empirical snubbing effect is also revealed, even without assuming the presence of a frictional pulley. Moreover, at small crack opening, the predicted trend of bridging force with inclination angle from the new model is in better agreement with test results than the snubbing friction model.
       
  • Mineral-impregnated carbon fibre reinforcement for high temperature
           resistance of thin-walled concrete structures
    • Abstract: Publication date: Available online 13 December 2018Source: Cement and Concrete CompositesAuthor(s): Kai Schneider, Albert Michel, Marco Liebscher, Lucas Terreri, Simone Hempel, Viktor Mechtcherine For a wide application of carbon-reinforced concrete, the sufficiency of the bond between concrete matrix and reinforcing elements must be ensured, even at high temperatures such as in the case of fire. Mineral-impregnated carbon fibre reinforcement offers a promising alternative to conventional polymer-impregnated carbon yarns or bars, whose performance deteriorates markedly with increasing temperature. One of the challenges in the production of mineral-impregnated carbon-fibre reinforcement is the selection of a processing technology and adequate raw materials. The work at hand addresses this challenge while focusing on the influence of the particle-size distribution of mineral fines on the impregnating behaviour of suspensions. Subsequently, the concentration shifts to the mechanical performance of thin reinforcement bars made of mineral-impregnated carbon fibre, as observed in three-point bending and pull-out tests. In comparison to polymer-impregnated reference materials, the new reinforcement demonstrates significantly enhanced mechanical properties at elevated temperatures of 100 °C and 200 °C.
       
  • Effect of sodium carbonate/sodium silicate activator on the rheology,
           geopolymerization and strength of fly ash/slag geopolymer pastes
    • Abstract: Publication date: Available online 13 December 2018Source: Cement and Concrete CompositesAuthor(s): Ishwarya G, B. Singh, S. Deshwal, S.K. Bhattacharyya Reactions between the fly ash/slag composite mix and the Na2CO3/Na2SiO3 activator were monitored through Isothermal conduction calorimetry. The resulting products were analyzed with the help of XRF, XRD and FT-IR techniques. In calorimetric response, the composite pastes had more total heat release than the fly ash paste requiring ∼50% less activation energy to yield reaction products. These products were largely amorphous as observed in the XRD patterns. Rheological studies indicated that composite pastes were very stiff above 25 wt% slag addition as its yield stress was almost doubled to fly ash paste. The compressive strength of hardened pastes increased with increasing slag content and activator dosage and decreased with increasing water-binder ratio. The deposition of reaction products onto the fly ash/slag particle surfaces and also the dense microstructures as observed in FESEM supported higher strength of geopolymer pastes at higher activator and slag contents. The developed paste with standard sand at 1:2 ratio produced mortar with a compressive strength of ∼72 MPa.
       
  • Effect of animal glue on mineralogy, strength and weathering resistance of
           calcium sulfate-based composite materials
    • Abstract: Publication date: Available online 12 December 2018Source: Cement and Concrete CompositesAuthor(s): Kerstin Elert, Cristina Benavides-Reyes, Carolina Cardell Calcium sulfate (gypsum, bassanite, and anhydrite) has been widely used since ancient times as decorative plaster and painting grounds, often mixed with organic additives (e.g., animal glue). In order to evaluate the effect of organic additives on gypsum setting and on the product's final properties, calcium sulfate-based plaster samples, with and without the addition of animal glue, were subjected to accelerated weathering and mechanical testing. Test results were related to the samples' mineralogical composition. Animal glue improved mechanical properties and weathering resistance, but retarded gypsum setting and resulted in long-term stabilization of metastable bassanite and anhydrite. Accelerated weathering (wetting/drying cycles) resulted in changes in mineral phases and micro-texture, affecting mechanical properties and facilitating deterioration due to phase transition-related volume changes. Findings are discussed with respect to applications of calcium sulfate-based materials in conservation and rehabilitation interventions.
       
  • Effects of abraded fine particle content on strength of quick-hardening
           concrete
    • Abstract: Publication date: Available online 11 December 2018Source: Cement and Concrete CompositesAuthor(s): Il-Wha Lee, Junkil Park, Dong Joo Kim, Sukhoon Pyo The strength of quick-converting railway tracks is expected to be lower due to abraded fine particles attached to the surface of ballast aggregates caused by gravel friction under repetitive train loading. The effects of abraded fine particle content on the failure process of quick-hardening concrete were investigated using digital image correlation (DIC) analysis during the testing of modeled cored aggregate concretes (MCACs). It was revealed that the failure strength of the MCACs was significantly affected by the amount of abraded fine particles attached to the surface of aggregates because the interfacial properties between aggregates and injected quick-hardening mortar were clearly affected by the particles. As the amount of particles increased from 0.0 to 0.6 wt%, the compressive strength of the MCACs decreased from 46.2 to 38.12 MPa owing to the deteriorated interfacial properties; however, the reduction was negligible until the abraded fine particle content reached 0.02 wt%. A micromechanical analysis was also carried out to highlight the effects of the interfacial strength on the mechanical response of quick-hardening mortar.
       
  • Effect of drying procedures on pore structure and phase evolution of
           alkali-activated cements
    • Abstract: Publication date: Available online 5 December 2018Source: Cement and Concrete CompositesAuthor(s): Zuhua Zhang, Yingcan Zhu, Huajun Zhu, Yu Zhang, John L. Provis, Hao Wang This study reports the effects of different drying procedures on the pore determination and phase evolution of alkali-activated cements based on metakaolin (AAMK), fly ash (AAFA) and slag (AAS), as characterized by N2 adsorption and XRD and FTIR analysis, in comparison with ordinary Portland cement (OPC) paste. The selected drying methods are: (1) 65 °C/24 h vacuum drying, (2) 105 °C/24 h oven drying, (3) solvent-exchange with ethanol for 3 days then 50 °C/24 h oven drying, and (4) freeze-drying with liquid nitrogen. The pore structures of AAMK and AAFA, with zeolite-like sodium aluminosilicate gel phases and little bound water, are less sensitive to drying conditions than are AAS and OPC, which consist of calcium (alumino)silicate hydrates. The drying procedures have less impact on the phase compositions of alkali-activated cements than OPC in general. Nonetheless, caution must be applied in selection of appropriate drying procedures to obtain reproducible and meaningful information regarding the pore and phase structure of alkali-activated cements.
       
  • Sulfate resistance of steam cured ferronickel slag blended cement mortar
    • Abstract: Publication date: Available online 5 December 2018Source: Cement and Concrete CompositesAuthor(s): Baoliang Li, Binbin Huo, Ruilin Cao, Shen Wang, Yamei Zhang The performance of steam cured (80 °C for 7 h) and standard cured ferronickel slag (FNS) cement mortar (0%, 20% replacement of cement with FNS) subjected to sodium sulfate attack were investigated. The results show that the incorporation of FNS improves the sulfate resistance of cement mortar on both early age standard curing condition and early age steam curing condition, however, the impact of early age steam curing on the sulfate resistance of FNS blended cement mortar under dry-wet cycles and partial immersion is the opposite. It is noted that early age steam curing promotes the formation of hemicarbonate and C-A-S-H, which accounts for the enhanced sulfate resistance of steam cured FNS blended cement mortar. The influence of (Mg, Fe)2SiO4 and MgSiO3 in FNS on the hydration products is found to be very limited regardless of early age curing condition.
       
  • Calcium-aluminate mortars at high temperatures: Overcoming adverse
           conversion effects using clinker aggregates
    • Abstract: Publication date: Available online 5 December 2018Source: Cement and Concrete CompositesAuthor(s): Dimas Alan Strauss Rambo, Neven Ukrainczyk, Flávio de Andrade Silva, Eddie Koenders, Romildo Dias Toledo Filho, Otávio da Fonseca Martins Gomes The effect of elevated temperatures on a calcium aluminate mortar with clinker aggregates is the subject of this paper. After an exposure period of 3 h at temperatures ranging from 25 to 1000 °C, specimens were tested in residual conditions in order to evaluate changes on the mechanical and microstructural properties. A simplified hydration model based on the chemical reactions of the principal minerals is proposed to predict the evolution of matrix composition from the early-age hydration. The improvement of the mechanical properties occurring due to the conversion reactions between 25 °C and 200 °C, is attributed to an increased hydration reaction of both cement and clinker aggregate. Furthermore, when compared to the metastable reactions, an improved interlocking effect at the reactive aggregate interface, and a more dense nature of the stable hydration products, were observed. These phenomena balance the adverse effects promoted by conversion reactions on porosity and mechanical properties.
       
  • Hydration accelerator and photocatalyst of nanotitanium dioxide
           synthesized via surfactant-assisted method in cement mortar
    • Abstract: Publication date: Available online 3 December 2018Source: Cement and Concrete CompositesAuthor(s): Jirayu Yuenyongsuwan, Sakprayuth Sinthupinyo, Edgar A. O'Rear, Thirawudh Pongprayoon To develop TiO2-based cement materials, the effect of TiO2 on the cement hydration and photocatalytic reaction should be investigated. The phase, size and shape of TiO2 are important factors for better understanding its application in cement. TiO2 nanoparticles were synthesized by a surfactant-assisted, reverse micelle method to control phase, size and shape by three selected surfactants namely: sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB) and TritonX-100. The synthesized TiO2 nanoparticles were characterized by XRD, SEM and TEM for observation of phase, size and shape. The modified micro structures of admixed cements with the different synthesized TiO2 nanoparticles incorporated were also examined by SEM. Particularly, the hydration process and photocatalytic reaction of the cement mixture were evaluated by heat flow calorimetry and methylene blue (MB) degradation, respectively. Results showed that anatase-rich and smaller size TiO2 nanoparticles provided accelerated cement hydration and the ability to degrade MB photocatalytically at the surface of admixed-TiO2 cement.
       
  • Self-healing cement composite: Amine- and ammonium-based pH-sensitive
           superabsorbent polymers
    • Abstract: Publication date: Available online 2 December 2018Source: Cement and Concrete CompositesAuthor(s): Chunyu Wang, Yuhuan Bu, Shenglai Guo, Yao Lu, Baojiang Sun, Zhonghou Shen Poor zonal isolation due to microcracks in cement sheath is a common problem that affects oil and gas exploration and also impacts the environment. In this study, pH-sensitive superabsorbent polymers (SAPs) have been successfully synthesized through copolymerization of 2-(Dimethylamino)ethyl methacrylate (DMAEMA) and acryloyloxyethyltrimethyl ammonium chloride (DAC) to achieve self-healing of microcracks in cement sheath. The chemical structure of p(DMAEMA-co-DAC) SAP was characterized using Fourier transform infrared (FTIR) spectroscopy. Water absorption tests determined the effect of cross-linker dosage and DMAEMA/DAC molar ratio on their water absorption rate (WAR). pH-sensitive tests showed they absorbed considerable water in neutral and weak alkaline solutions but little water in strong alkaline solutions. In addition, the WARs were quite small in high concentration calcium chloride solutions. The WARs in distilled water reduced after they were processed in cement slurry filtrate (CSF) due to hydrolysis of ester groups and the crosslinking effect of Ca2+ ions. Additionally, the SAP showed good compatibility with the cement slurry. It had little impact on the thickening time, rheological property, fluid loss, and early compressive strength of cement slurry/stone. Eventually, sealing pressure test results indicated the self-healing properties of p(DMAEMA-co-DAC) SAP-modified oil well cement. Using a 2 wt.% SAP addition, microcracks up to 166 μm can be sealed.
       
  • Meso-scale mechanical deterioration of mortar due to sodium chloride
           attack
    • Abstract: Publication date: Available online 30 November 2018Source: Cement and Concrete CompositesAuthor(s): Yi Wang, Tamon Ueda, Fuyuan Gong, Dawei Zhang Salt frost deterioration of concrete is an important durability problem to concern. Prior to clarifying the salt frost damage mechanisms, the salt effect on mechanical behavior of concrete needs to be clarified. To quantitatively understand the damage effects, this paper experimentally investigated meso-scale mortar samples suffered from sodium chloride (NaCl) attack, including mechanical degradation in meso scale and chemical analysis of calcium hydroxide and Friedel's salt in micro scale. The test results showed that calcium (Ca2+) leaching and salt crystallization occur along with the solution absorption process, and the kinetics is depending on water to cement ratio (W/C) and solution concentrations. Higher W/C has more severe Ca2+ leaching and strength loss, while the leaching amount and strength loss are changed in fluctuating manner with the solution concentrations. The amount of crystallized salt is increasing with the solution concentration. The mechanical degradation degree agrees with the Ca2+ leaching amount. The results indicated that the deterioration of mortar is mainly resulting from increasing porosity due to Ca2+ leaching.
       
  • Experimental approach to investigate creep-damage bilateral effects in
           concrete at early age
    • Abstract: Publication date: Available online 29 November 2018Source: Cement and Concrete CompositesAuthor(s): M. Farah, F. Grondin, S.Y. Alam, A. Loukili The concrete structures are under heavy loads once they are set up. The effect of this early loading particularly in terms of creep deformations could be very significant. In order to evaluate the effect of these deformations on the cracking risk of concrete, many studies on early-age creep have been conducted in the last decades. These studies concern mainly tension and compression loadings. However, few studies have been conducted under bending, even though this loading is the most representative for structures. This paper is focused to improve the understanding of the historical loading effect on the concrete residual behaviour. A series of flexural creep tests were performed at early ages on non-damaged beams with a constant and a stepwise increasing creep loads. In order to better understand the interaction between creep and damage, series of flexural creep tests were also performed at early ages on partially damaged beams. The test results have shown a drop of Young's modulus and residual strength after creep loadings in partially damaged beams. It implies the development of a state of weakness in beams subjected to an increasing creep load.
       
  • Mechanical properties of textile reinforced concrete under chloride
           wet-dry and freeze-thaw cycle environments
    • Abstract: Publication date: Available online 28 November 2018Source: Cement and Concrete CompositesAuthor(s): Shiping Yin, Lei Jing, Mengti Yin, Bo Wang This paper studied the mechanical properties of textile reinforced concrete (TRC) under chloride wet-dry and freeze-thaw cycles, considering the number of cycles, the coupling effect of bending sustained load and corrosion environment, and adding short-cut fibers into fine grained concrete. The results showed that as the number of chloride wet-dry cycles increased, the average interfacial bonding strength between the fiber yarn and fine grained concrete decreased; while the bending bearing capability of the TRC thin plates showed no coincident trend. However, with the increase of the number of chloride freeze-thaw cycles, strengths were both reduced. Adding short-cut fibers improved the average interfacial bonding strength between the fiber yarn and fine grained concrete, as well as the bending bearing capability of the TRC thin plates under chloride wet-dry cycles. Moreover, the mechanical performance of the TRC thin plates has not been significantly improved under chloride freeze-thaw cycles.
       
  • Insights and issues on the correlation between diffusion and
           microstructure of saturated cement pastes
    • Abstract: Publication date: Available online 27 November 2018Source: Cement and Concrete CompositesAuthor(s): Quoc Tri Phung, Norbert Maes, Elke Jacops, Diederik Jacques, Geert De Schutter, Guang Ye The objective of this study is to quantify the contributions of microstructure and molecular size of diffusing species to tortuosity, constrictivity and effective diffusivity. The microstructural effect is simulated with different sound, leached or carbonated cement pastes with varying water to cement ratios and limestone replacement filler replacements. Leached and carbonated samples were obtained by accelerated experiments: leaching by immersing samples in ammonium nitrate solution and carbonation by subjecting the samples to pure CO2 at elevated pressure. To characterise the microstructural properties, Mercury Intrusion Porosimetry (MIP), and N2-adsorption were used. The effect of molecular size is quantified with a recent developed diffusion setup allowing for simultaneous measurement of the diffusion of species with different molecular sizes. Previously developed models were also used to verify and give insights into the evolution of diffusion of degraded materials. In addition, a larger dataset from literature is used to evaluate a model which accounts for molecular size as well to predict diffusivity.Resultsshow that because of the significant contribution of the molecular size of the diffusing species to the diffusion process, the constrictivity and thereby geometric factor may not be considered as intrinsic properties of the cement pastes. The geometric factor and/or constrictivity of cement pastes depends on the interrelationship of the molecular size of the diffusing species with the microstructure of the cementitious materials. A smaller diffusing species or/and a higher porosity of the sample results in a lower value of geometric factor. Interestingly, constrictivity is significantly influenced by the molecular size, but not the porosity.
       
  • Physical and permeability properties of cementitious mortars having fly
           ash with optimized particle size distribution
    • Abstract: Publication date: Available online 27 November 2018Source: Cement and Concrete CompositesAuthor(s): İlhami Demir, Özer Sevim Gradation of powder materials is often avoided in pozzolanic materials, such as fly ash. Without good gradation, powder materials result in high void ratios similar to the case of aggregates. The products obtained after hydration would still have voids.This study calculated the particle size distributions (PSDs) of fly ash using a vacuum sieve in accordance with the Dinger–Funk PSD modulus. The optimal PSD was defined, and the compressive strength of fly-ash-blended cement mortars at 7, 28 and 90 days was explored. Properties such as water absorption capacity, dry density and rapid chloride permeability of the optimised fly ash were analysed by varying the replacement levels. The water absorption capacity of the optimised fly-ash-blended cement mortar was lower than that of the blended cement mortar having non-optimised fly ash. Moreover, at 90 days, the chloride permeability of the optimised fly-ash-blended cement mortar was improved by up to 39.1% when compared to that of the blended cement mortar having non-optimised fly ash.
       
  • Investigation into the effect of calcium on the existence form of
           geopolymerized gel product of fly ash based geopolymers
    • Abstract: Publication date: Available online 27 November 2018Source: Cement and Concrete CompositesAuthor(s): Xianhui Zhao, Chunyuan Liu, Liming Zuo, Li Wang, Qin Zhu, Mengke Wang Fly ash-based geopolymer, regarded as a eco-friendly cementitious material instead of ordinary Portland cement, has been rapidly developed and applied in practical engineering practice. Previous researches demonstrated that calcium component produces distinct effect on the formation of polymer gel products, and therefore influencing the macroscopic mechanical behaviors and microstructure of geopolymers. However, the influence mechanism of calcium component on the formation of gels product is still not clear. In this study, different content of Ca(OH)2 are adopted to prepare calcium containing geopolymers. The compressive strength and hydrochloric acid-attack tests were conducted to evaluate the effect of calcium content on the macro-performances. Then, scanning electron microscopy-energy spectrum test (SEM-EDS) was carried out to accesses the morphology and elemental components of the prepared composites. Thereafter, the microstructure of gels product is probed through Fourier transform infrared (FTIR) spectroscopy and 29Si nuclear magnetic resonance (NMR) spectroscopy. The critical value of elemental ratio (Na + K + Ca)/Al to characterize the gel product is specified. Two kinds of fly ash and two alkali-activated solutions were adopted to verify the results. The geopolymerization products will be calcium-containing geopolymer gels (C,N-A-SH) when (Na + K + Ca)/Al≤0.95, while be coexist form of CSH and N-A-SH gels when (Na + K + Ca)/Al>0.95. The results provide experimental basis and references for the application of calcium-containing solid wastes in geopolymer materials.
       
  • Effects of short fiber and pre-tension on the tensile behavior of basalt
           textile reinforced concrete
    • Abstract: Publication date: Available online 23 November 2018Source: Cement and Concrete CompositesAuthor(s): Deju Zhu, Sai Liu, Yiming Yao, Gaosheng Li, Yunxing Du, Caijun Shi Tensile behaviors of basalt textile-reinforced concrete (BTRC) with five layers of textile and different volume contents of short carbon, glass, and steel fibers (0.5 vol%, 1.0 vol%, and 1.5 vol% for carbon and steel fibers and 0.5 vol% for glass fiber) are investigated under uniaxial tensile loading by using an MTS load frame. Pre-tensioned BTRC with 0.5 vol% of short carbon and steel fibers is also tested. The reinforcing mechanisms of different short fibers and pre-tension conditions are illustrated, and digital image correlation analysis is performed to obtain full-field strain and crack distribution. First crack stress, ultimate load, and toughness are significantly improved by short fibers and pre-tension. The improving trend differs with the increase in volume fractions of various short fibers. Short glass, steel fibers, and pre-tension can increase crack numbers with reduced crack spacing and width, whereas short carbon fiber exerts no obvious effect. In addition, the shape of cracks changes from linear pattern to curved form due to the addition of short fibers. The critical crack widens quickly, whereas other non-critical cracks diminish when the strain level goes beyond the ultimate strain. On the basis of the Aveton–Cooper–Kelly model, the relationship of the normalized effective factor and interfacial frictional shear stress is derived.
       
  • Effects of two oppositely charged colloidal polymers on cement hydration
    • Abstract: Publication date: Available online 23 November 2018Source: Cement and Concrete CompositesAuthor(s): Zichen Lu, Xiangming Kong, Chaoyang Zhang, D. Jansen, J. Neubauer, F. Goetz-Neunhoeffer Effects of two styrene acrylate copolymer latexes with opposite charge properties on cement hydration were investigated by calorimetry, in-situ XRD and pore solution analysis. It is found that the anionic latex (AL) shows much stronger retardation effect than the cationic latex (CL) on OPC hydration, which should be caused by higher adsorption affinity of AL. Specifically, for aluminate reaction during OPC hydration, the strong adsorption of AL on positively charged C3A surface inhibits C3A dissolution and AFt formation, which invalidates the dependency of the secondary C3A dissolution on the sulfate depletion in normal OPC hydration. For the silicate reactions, mainly C3S hydration, AL again exhibits much higher adsorption on C3S and consequently stronger retardation than CL, which is caused by the reversal of charging property of C3S grains from negative in pure water to positive in Ca2+ rich solution. The adsorbed polymer may severely block nucleation sites for CSH precipitation.
       
  • Development of lightweight engineered cementitious composite for
           durability enhancement of tall concrete wind towers
    • Abstract: Publication date: Available online 23 November 2018Source: Cement and Concrete CompositesAuthor(s): Qingxu Jin, Victor C. Li Recently, concrete (especially high strength concrete) is considered the most suitable material for building tall wind turbine towers. However, concrete is prone to cracking and the durability of tall concrete towers can be compromised when large cracks (>300 μm) occur on their exterior surfaces. In this study, a lightweight engineered cementitious composite (ECC), reinforced by high tenacity polypropylene fiber, was developed based on performance driven design approach to serve as protective coatings on the tall concrete towers. By using fly ash cenospheres as lightweight filler material, a lightweight ECC with a density of 1810 kg/m3 can be achieved. Guided by micromechanics-based design theory, this newly developed ECC can achieve a tensile strength above 2 MPa, tensile ductility above 2%, and maximum crack width of 100 μm in both direct tension and flexural fatigue tests. The high ductility and excellent crack control of ECC coating can improve the cracking resistance of the hybrid tall ECC/concrete towers, therefore enhancing their durability and extending their service life.
       
  • The effects of polyaluminum chloride on the mechanical properties of
           alkali-activated slag cement paste
    • Abstract: Publication date: Available online 22 November 2018Source: Cement and Concrete CompositesAuthor(s): Taewan Kim Herein, an experimental investigation of the mechanical properties of alkali-activated slag cement (AASC) mixed with polyaluminium chloride (PAC) was conducted. The alkali activators were 5% sodium hydroxide and 5% sodium silicate of binder weight. The PAC substitution rate was varied by adjusting the mixing water weight from 0% to 10%, and the obtained samples were characterized by compression testing, X-ray diffractometry, scanning electron microscopy (SEM), mercury intrusion porosimetry, thermogravimetric analysis, differential thermal analysis, and energy-dispersive X-ray spectroscopy. PAC substitution formed a dense C-A-S-H gel and Friedel's salt. SEM observations revealed that a dense matrix of hydration products and Friedel's salt existed in the pores. Moreover, greater amounts of PAC result in better mechanical performance. Thus, these hydration products enhance the strength of AASC by compacting the matrix and filling the voids.
       
  • Effects of weathering on the performances of self-cleaning photocatalytic
           paints
    • Abstract: Publication date: Available online 22 November 2018Source: Cement and Concrete CompositesAuthor(s): D. Enea, M. Bellardita, P. Scalisi, G. Alaimo, L. Palmisano The use of photocatalytic products for the surface coating of buildings is spreading more and more, because of the reduction of atmospheric pollutants and the colour maintenance of the paints over time with reduction of the maintenance costs and the improvement of the aesthetic appearance. The study reports the evaluation of the effects of the atmospheric conditions on three commercial photocatalytic paints containing TiO2. In particular tests were carried out by using samples subjected to accelerated aging inside a climate chamber and naturally aged by exposure for two years to the external environment of the city of Palermo (representative of a coastal environment of the Mediterranean basin). The samples were characterized by Scanning Electron Microscopy (SEM) and Optical Microscopy to evaluate the surface morphology, and by UV-Vis Spectrophotometry to appreciate the colours changes as a result of aging. X-ray diffraction (XRD), moreover, was used to identify the TiO2 phase and static contact angles were determined to evaluate the surface hydrophilicity. The photocatalytic activity was evaluated under UV and solar light irradiation by degrading 2-propanol, used as a probe molecule and analysed by gas chromatography (GC), which is representative of volatile organic compounds (VOC's). The results indicated colour conservation, increase of the surface hydrophilicity and maintenance of the photocatalytic performances.
       
  • The influence of expansive cement on the mechanical, physical, and
           microstructural properties of hybrid-fiber-reinforced concrete
    • Abstract: Publication date: Available online 22 November 2018Source: Cement and Concrete CompositesAuthor(s): Vahid Afroughsabet, Guoqing Geng, Alexander Lin, Luigi Biolzi, Claudia P. Ostertag, Paulo J.M. Monteiro This work reports the properties of hybrid-fiber-reinforced concrete (HyFRC) made with expansive (Type K) cement. Combinations of metallic and non-metallic fibers at total fiber volume fraction of 1% were studied. The effectiveness of double hooked-end (DHE) steel fibers in concrete containing expansive cement is investigated for the first time in this study. The mechanical, physical, and microstructural properties of concretes have been assessed. Additionally, the fiber pull-out test was also performed to investigate the effectiveness of Type K cement in improving the fiber-matrix interfacial bond. The results indicate that Type K cement has small influence on the mechanical properties of concrete fabricated at the same water-cement ratio of 0.35 with a similar consistency. However, as expected, it enhances the volume stability of concrete subjected to drying condition. The pull-out resistance of steel fibers increased by 26% as a result of full replacement of ordinary Portland cement (OPC) with Type K cement. A deflection-hardening performance is achieved by introducing of DHE steel fibers in HyFRC. The partially replacement of DHE steel fibers with other type of fibers results in a reduction in the strengths of HyFRC. The results obtained in this study proves that the bond between fiber and cement matrix is enhanced by fully replacement of OPC with expansive cement, which subsequently improves the mechanical properties of HyFRC.
       
  • An experimental study on the corrosion susceptibility of Recycled Steel
           Fiber Reinforced Concrete
    • Abstract: Publication date: Available online 22 November 2018Source: Cement and Concrete CompositesAuthor(s): Cristina Frazão, Belén Díaz, Joaquim Barros, J. Alexandre Bogas, Fatih Toptan Under chloride attack, an important aspect of Recycled Steel Fiber Reinforced Concrete (RSFRC) durability is its corrosion resistance. However, the insufficient knowledge on this domain contributes for a conservative design philosophy, which can compromise the cost competitiveness of RSFRC.In the present work, an experimental program was performed with the aim of assessing the corrosion susceptibility of RSFRC including the characterization of the corrosion resistance of recycled steel fibers (RSF) and the evaluation of the corrosion effects on the post-cracking response of RSFRC. The influence of the small rubber debris attached to the RSF surface was also analyzed by using two distinct pre-treatment methods.The RSF were slightly more susceptible to corrosion than industrialized steel fibers, not sufficient to alter significantly the post-cracking resistance of RSFRC. The low amount of small rubber debris attached to RSF surface had a negligible influence in their corrosion resistance.
       
  • Synergistic effects of hybrid polypropylene and steel fibers on explosive
           spalling prevention of ultra-high performance concrete at elevated
           temperature
    • Abstract: Publication date: Available online 20 November 2018Source: Cement and Concrete CompositesAuthor(s): Ye Li, Kang Hai Tan, En-Hua Yang This study investigated synergetic effects of hybrid polypropylene (PP) and steel fibers on explosive spalling prevention of ultra-high performance concrete (UHPC) at elevated temperature. Permeability of UHPC was measured and correlated to the extent of spalling quantitatively. Microstructures of UHPC before and after elevated temperature exposure were examined to reveal potential mechanisms responsible for changes in permeability. Results showed that the use of hybrid PP and steel fibers completely prevented explosive spalling even at low fiber dosage of both fibers due to significant increase of permeability. Microstructural analysis revealed that such synergistic effect on increased permeability of hybrid PP and steel fiber-reinforced UHPC was attributed to enhanced connectivity of empty PP fiber tunnels by multiple microcracks generated from the thermal expansion of both fibers.
       
  • Multiscale modeling of ion diffusion in cement paste: Electrical double
           layer effects
    • Abstract: Publication date: Available online 16 November 2018Source: Cement and Concrete CompositesAuthor(s): Yuankai Yang, Ravi A. Patel, Sergey V. Churakov, Nikolaos I. Prasianakis, Georg Kosakowski, Moran Wang Understanding the mechanism of ion diffusion in hardened cement paste is of great importance for predicting long-term durability of concrete structures. Gel pores in calcium silicate hydrate (CSH) phase forms dominant pathway for transport in cement paste with low w/c ratios where the electrical double layer effects play an important role. Experimental results suggest that the effective diffusivity of chloride ions is similar as that of tritiated water (HTO) and higher than the sodium ions. This difference can be attributed to the electrical double layer near the charged CSH surfaces. In order to understand species transport processes in CSH and to quantify its effective diffusivity, a multiscale modeling technique has been proposed to combine atomic-scale and pore-scale modeling. At the pore-scale, the lattice Boltzmann method is used to solve a modified Nernst Planck equation to model transport of ions in gel pores. The modified Nernst Planck equation accounts for steric and ion-ion correlation effects by using correction term for excess chemical potential computed using the results from the grand canonical Monte Carlo scheme at atomic scale and in turn bridges atomic scale model with pore scale model. Quantitative analysis of pore size influence on effective diffusivity carried out by this multiscale model shows that the contribution of the Stern layer to ion transport is not negligible for pores with diameter less than 10 nm. The developed model is able to reproduce qualitatively the trends of the diffusivity of different ions reported in literature.
       
  • Estimating the optimal mix design of silica fume concrete using
           biogeography-based programming
    • Abstract: Publication date: Available online 12 November 2018Source: Cement and Concrete CompositesAuthor(s): Emadaldin Mohammadi Golafshani, Ali Behnood The use of silica fume in concrete mixtures has been dramatically increased in concrete industry, especially for achieving high strength concrete. An accurate model of estimating the compressive strength and optimal mix design of silica fume concrete can save in time and cost. In this study, the biogeography-based programming (BBP) was served as a symbolic regression method to predict the compressive strength of silica fume concrete, while the constrained biogeography-based optimization (CBBO) was used to estimate its optimal mix design. For this purpose, a comprehensive database was gathered from various published documents. From the collected data, about 75% of all data was employed to train the model, while the rest was used to verify the developed model. The amounts of cement, water, silica fume, coarse aggregate, fine aggregate, superplasticizer, as well as the maximum size of aggregate and concrete age were selected as the effective input variables of the model. The compressive strength of silica fume concrete was considered as the only output variable. The results show that the BBP model can be successfully used for the prediction of the compressive strength of silica fume concrete with acceptable accuracy. In addition, a graphical user interface was designed which allows the users to estimate the optimal mix design of silica fume concrete.
       
  • Quantitative analysis on porosity of reactive powder concrete based on
           automated analysis of back-scattered-electron images
    • Abstract: Publication date: Available online 2 November 2018Source: Cement and Concrete CompositesAuthor(s): Romy Suryaningrat Edwin, Mushthofa Mushthofa, Elke Gruyaert, Nele De Belie In this study an automated analysis of back-scattered-electron images (SEM-BSE) for segmentation of the porosity of reactive powder concrete is presented, making use of Matlab. The development of the proposed threshold method is based on a classification of the images according to two different brightness levels, which correspond to low and high grey value thresholds. The intersection point of the tangent lines in the area segmented versus grey value curve is used as the upper threshold to determine threshold 1 and threshold 2 and the resulting pore volume is validated with mercury intrusion porosimetry. Nevertheless, a difference between porosities obtained by SEM-BSE and MIP can be expected, because the first method can measure all pore types, while the second will only measure open pores. The result shows that the use of the proposed threshold method achieves a good correlation with MIP for pore segmentation in the RPC microstructure.
       
  • Statistical modelling of compressive strength controlled by porosity and
           pore size distribution for cementitious materials
    • Abstract: Publication date: Available online 16 October 2018Source: Cement and Concrete CompositesAuthor(s): Dongwei Hou, Dongyao Li, Peicheng Hua, Junda Jiang, Guoping Zhang The compressive strength of cementitious materials is significantly affected by its pore system inherent in the matrix of cement paste, not only porosity but also pore size distribution. In present work, by deconvolution analysis, the total pore size distribution of cement paste is represented by a multiple distribution consisting of two single distributions for the capillary pores and the macro pores respectively. In this way, the widely accepted Raleigh-Ritz (R-R) function is challenged and the lognormal distribution is found to be best to approximate the pore size distribution for cementitious materials. With pore size distributions, a statistical model based on probability principle and fracture criterion is proposed to reveal the physical mechanism of reduction in compressive strength induced by porous structures. Parameters in the model, e.g. fracture toughness of cement paste matrix, fracture mode, volume of specimen, porosity and pore size distributions, are further discussed and examined quantitatively.
       
  • 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.
       
  • 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.
       
  • 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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