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  Subjects -> ENGINEERING (Total: 2282 journals)
    - CHEMICAL ENGINEERING (192 journals)
    - CIVIL ENGINEERING (186 journals)
    - ELECTRICAL ENGINEERING (102 journals)
    - ENGINEERING (1204 journals)
    - ENGINEERING MECHANICS AND MATERIALS (385 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (68 journals)
    - MECHANICAL ENGINEERING (90 journals)

CIVIL ENGINEERING (186 journals)                     

Showing 1 - 186 of 186 Journals sorted alphabetically
ACI Structural Journal     Full-text available via subscription   (Followers: 17)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 2)
Advances in Civil Engineering     Open Access   (Followers: 34)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 27)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 30)
Architectural Engineering     Open Access   (Followers: 4)
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 1)
Archives of Civil Engineering     Open Access   (Followers: 10)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 1)
ATBU Journal of Environmental Technology     Open Access   (Followers: 3)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 6)
Baltic Journal of Road and Bridge Engineering     Full-text available via subscription   (Followers: 1)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 9)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 4)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 4)
Berkeley Planning Journal     Open Access   (Followers: 7)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 15)
Building and Environment     Hybrid Journal   (Followers: 15)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 15)
Bulletin of Pridniprovsk State Academy of Civil Engineering and Architecture     Open Access   (Followers: 6)
Canadian Journal of Civil Engineering     Hybrid Journal   (Followers: 11)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 10)
Case Studies in Structural Engineering     Open Access   (Followers: 9)
Cement and Concrete Composites     Hybrid Journal   (Followers: 17)
Challenge Journal of Concrete Research Letters     Open Access   (Followers: 2)
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: 7)
Civil And Environmental Engineering Reports     Open Access   (Followers: 5)
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: 17)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 9)
Civil Engineering Dimension     Open Access   (Followers: 8)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 258)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 10)
Computers & Structures     Hybrid Journal   (Followers: 36)
Concrete Research Letters     Open Access   (Followers: 6)
Construction Economics and Building     Open Access   (Followers: 2)
Construction Engineering     Open Access   (Followers: 8)
Construction Management and Economics     Hybrid Journal   (Followers: 21)
Construction Science     Open Access   (Followers: 4)
Constructive Approximation     Hybrid Journal  
Curved and Layered Structures     Open Access   (Followers: 2)
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal   (Followers: 1)
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 16)
Enfoque UTE     Open Access   (Followers: 4)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 7)
Engineering Structures     Hybrid Journal   (Followers: 13)
Engineering Structures and Technologies     Hybrid Journal   (Followers: 2)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 14)
Environmental Geotechnics     Hybrid Journal   (Followers: 5)
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 8)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 16)
Frattura ed Integrità Strutturale : Fracture and Structural Integrity     Open Access  
Frontiers in Built Environment     Open Access  
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Geomaterials     Open Access   (Followers: 4)
Geosystem Engineering     Hybrid Journal   (Followers: 1)
Geotechnik     Hybrid Journal   (Followers: 3)
Géotechnique Letters     Hybrid Journal   (Followers: 6)
HBRC Journal     Open Access   (Followers: 2)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal  
Indoor and Built Environment     Hybrid Journal   (Followers: 2)
Infrastructure Asset Management     Hybrid Journal   (Followers: 2)
Infrastructures     Open Access  
Ingenio Magno     Open Access   (Followers: 1)
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 22)
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: 16)
International Journal of Civil, Mechanical and Energy Science     Open Access   (Followers: 1)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 13)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 2)
International Journal of Construction Engineering and Management     Open Access   (Followers: 8)
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: 4)
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: 10)
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: 4)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 8)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 6)
International Journal Sustainable Construction & Design     Open Access  
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 15)
Journal of Building Engineering     Hybrid Journal   (Followers: 1)
Journal of Building Materials and Structures     Open Access   (Followers: 2)
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 6)
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 11)
Journal of Civil Engineering and Management     Hybrid Journal   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 7)
Journal of Civil Engineering Research     Open Access   (Followers: 6)
Journal of Civil Society     Hybrid Journal   (Followers: 3)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 4)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 13)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 24)
Journal of Construction Engineering     Open Access   (Followers: 7)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 19)
Journal of Construction Engineering, Technology & Management     Full-text available via subscription   (Followers: 4)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 8)
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: 11)
Journal of Highway and Transportation Research and Development (English Edition)     Full-text available via subscription   (Followers: 12)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 21)
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: 4)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 10)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 11)
Journal of Offshore Structure and Technology     Full-text available via subscription  
Journal of Performance of Constructed Facilities     Full-text available via subscription   (Followers: 4)
Journal of Pipeline Systems Engineering and Practice     Full-text available via subscription   (Followers: 7)
Journal of Rehabilitation in Civil Engineering     Open Access   (Followers: 3)
Journal of Solid Waste Technology and Management     Full-text available via subscription   (Followers: 1)
Journal of Structural Engineering     Full-text available via subscription   (Followers: 39)
Journal of Structural Fire Engineering     Full-text available via subscription   (Followers: 6)
Journal of Sustainable Architecture and Civil Engineering     Open Access   (Followers: 3)
Journal of Sustainable Design and Applied Research in Innovative Engineering of the Built Environment     Open Access   (Followers: 1)
Journal of the South African Institution of Civil Engineering     Open Access   (Followers: 4)
Jurnal Spektran     Open Access   (Followers: 1)
Jurnal Teknik Sipil dan Perencanaan     Open Access  
Konstruksia     Open Access  
KSCE Journal of Civil Engineering     Hybrid Journal   (Followers: 2)
Latin American Journal of Solids and Structures     Open Access   (Followers: 4)
Materiales de Construcción     Open Access  
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 3)
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 17)
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 6)
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 2)
Practice Periodical on Structural Design and Construction     Full-text available via subscription   (Followers: 4)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 7)
Proceedings of the Institution of Civil Engineers - Civil Engineering     Hybrid Journal   (Followers: 11)
Proceedings of the Institution of Civil Engineers - Management, Procurement and Law     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Civil Engineers - Municipal Engineer     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Civil Engineers - Structures and Buildings     Hybrid Journal   (Followers: 4)
Random Structures and Algorithms     Hybrid Journal   (Followers: 5)
Recent Trends In Civil Engineering & Technology     Full-text available via subscription   (Followers: 4)
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 7)
Revista IBRACON de Estruturas e Materiais     Open Access   (Followers: 1)
Road Materials and Pavement Design     Hybrid Journal   (Followers: 9)
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 6)
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: 4)
Steel Construction - Design and Research     Hybrid Journal   (Followers: 3)
Structural and Multidisciplinary Optimization     Hybrid Journal   (Followers: 9)
Structural Concrete     Hybrid Journal   (Followers: 11)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 9)
Structural Engineering International     Full-text available via subscription   (Followers: 11)
Structural Safety     Hybrid Journal   (Followers: 7)
Structural Survey     Hybrid Journal  
Structure     Full-text available via subscription   (Followers: 23)
Structure and Infrastructure Engineering: Maintenance, Management, Life-Cycle Design and Performance     Hybrid Journal   (Followers: 12)
Structures     Hybrid Journal   (Followers: 1)
Study of Civil Engineering and Architecture     Open Access   (Followers: 8)
Superlattices and Microstructures     Hybrid Journal   (Followers: 2)
Surface Innovations     Hybrid Journal  
Technical Report Civil and Architectural Engineering     Open Access  
Teknik     Open Access  
The IES Journal Part A: Civil & Structural Engineering     Hybrid Journal   (Followers: 6)
The Structural Design of Tall and Special Buildings     Hybrid Journal   (Followers: 6)
Thin Films and Nanostructures     Full-text available via subscription   (Followers: 2)
Thin-Walled Structures     Hybrid Journal   (Followers: 4)
Transactions of the VŠB - Technical University of Ostrava. Construction Series     Open Access   (Followers: 1)
Transportation Geotechnics     Full-text available via subscription   (Followers: 1)
Transportation Infrastructure Geotechnology     Hybrid Journal   (Followers: 8)
Underground Space     Open Access  
Water Science & Technology     Partially Free   (Followers: 25)
Water Science and Technology : Water Supply     Partially Free   (Followers: 22)

           

Journal Cover Cement and Concrete Composites
  [SJR: 3.017]   [H-I: 83]   [17 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0958-9465
   Published by Elsevier Homepage  [3044 journals]
  • Incorporating phase change materials in concrete pavement to melt snow and
           ice
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Yaghoob Farnam, Hadi S. Esmaeeli, Pablo D. Zavattieri, John Haddock, Jason Weiss
      This paper discusses the use of phase change materials (PCM) in concrete pavement as a method to store energy which can be used as a heat source during cooling events to melt ice/snow. The experimental program includes: (1) use of low-temperature differential scanning calorimetry to evaluate thermal properties of PCM, and (2) use of large-scale concrete slabs containing PCM to evaluate the ability of the PCM concrete to melt snow on the surface of the concrete pavement. The temperature in the concrete slabs and the snow melting rate were monitored as quantitative measurements of the efficiency of the PCM in the concrete. In addition, time-lapse images were taken. Two approaches were used to incorporate PCM in concrete: placing the PCM in lightweight aggregate (LWA) which was then mixed into the concrete, and placing the PCM in embedded metal pipes embedded in the slab during concrete casting. In this study, paraffin oil was use as a PCM that is effective in releasing heat near the freezing temperature of PCM when the PCM undergoes a phase transformation from liquid to solid. The heat released during the phase transformation can melt ice and snow on the concrete pavement surface. The results indicate that incorporating PCM in concrete pavement is not only feasible, but also practical.

      PubDate: 2017-09-19T16:57:32Z
       
  • Eco-efficient ultra-high performance concrete development by means of
           response surface methodology
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Iman Ferdosian, Aires Camões
      The research described in this paper represents a statistically based model with the help of response surface methodology (RSM) aiming to study the applicability of this method to ultra-high performance concrete (UHPC) mixture design and its optimization. Besides, the effects of silica fume, ultra-fine fly ash (UFFA) and sand as three main variable constituents of UHPC on workability and compressive strength as the main performance criteria and responses of this high-tech material were investigated. The models proposed here demonstrate a perfect correlation among variables and responses. Furthermore, through performing a multi-objective optimization, cement and silica fume, as two main constituents of UHPC affecting its eco-efficiency and cost, were substituted by UFFA and sand as much as possible. Finally, an eco-efficient UHPC with cement and silica fume content of 640 kg/m3 and 56.3 kg/m3 respectively and compressive strength and flow diameter of 160.3 MPa and 19 cm was developed.

      PubDate: 2017-09-19T16:57:32Z
       
  • Comparative performance of alkali activated slag/metakaolin cement pastes
           exposed to high temperatures
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Oswaldo Burciaga-Díaz, José Iván Escalante-García
      This paper presents a study on the effect of temperature exposure of binders of blast furnace slag (BFS) and metakaolin (MK) in BFS-MK weight ratios of 100-0, 50-50, and 0-100 activated with sodium silicate of modulus Ms = SiO2/Na2O = 1 and 5, 10 and 15% Na2O. A blended ordinary CPC-30R Portland cement reference was used. Pastes were subjected to exposure up to 1200 °C and the performance was evaluated in terms of compressive strength, residual strength, volumetric shrinkage, physical appearance and microstructural changes at different temperatures. All the binders retained more than 30 MPa after exposure to 800 °C for 4 h; specimens of MK and CPC-30R experienced the highest strength losses of 42 and 56% respectively, while those of 100-0 and 50-50 showed minor losses of ∼20%. After heating at 1200 °C the samples showed microstructural damage and more than 65% of strength losses. XRD indicated that the 100-0 and 50/50 binders are prone to form crystalline phases as akermanite, nepheline and nosean at temperatures greater than 1000 °C, while 0-100 geopolymeric binders preserved mostly an amorphous structure even at 1200 °C with some traces of mullite. The dehydration of C-A-S-H and N-A-S-H altogether with the crystallization of the binder gel induced the formation of highly porous microstructures.

      PubDate: 2017-09-19T16:57:32Z
       
  • Use of pre-wetted lightweight fine expanded shale aggregates as internal
           nutrient reservoirs for microorganisms in bio-mineralized mortar
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Zeynep Başaran Bundur, Mary Jo Kirisits, Raissa Douglas Ferron
      Interest in developing bio-based self-healing cement-based materials has gained broader attention in the concrete community. One of challenges in developing bio-based self-healing cement-based materials is that cell death or insufficient metabolic activity might occur when the cells are inoculated to the cement paste. This paper investigates the use of internal nutrient reservoirs via pre-wetted lightweight fine expanded shale aggregates to improve cell viability in mortar. Incorporation of internal nutrient reservoirs resulted in an increase in the vegetative cells remaining without any substantial loss in strength. These results pave the way to develop a self-healing and self-curing concrete with an extended service life.

      PubDate: 2017-09-19T16:57:32Z
       
  • Optimization of normal and high strength recycled aggregate concrete
           mixtures by using packing model
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Mayara Amario, Caroline Santana Rangel, Marco Pepe, Romildo Dias Toledo Filho
      This paper analyzes the possibility of applying the Compressible Packing Model (CPM) for the proportion of concrete mixtures produced with Recycled Concrete Aggregates (RCAs). As a matter of fact, the RCAs are composed of natural aggregates and attached mortar and, as a consequence, they generally present a higher porosity in comparison with ordinary natural aggregates. The higher porosity of RCAs can affect the resulting Recycled Aggregate Concretes (RACs) properties and, for this reason, the mix design procedure available in literature for ordinary concrete mixture cannot be applied as such in the case of RACs. In this context, the present work first presents a preliminary study in which the optimal mixing procedure for RACs is investigated and then, a possible extension of the CPM in the case of RACs is analyzed. Several structural RAC mixtures were designed for three strength classes (25, 45 and 65 MPa) by considering the variation of the aggregate replacement from 0 to 100%. Finally, the proposed procedure is experimentally validated by performing mechanical and durability tests on selected mixtures for the three strength classes with a RCAs content up to 60%. The results reported herein demonstrate the applicability of the CPM for recycled concrete mixtures and highlight as the rational use of RCAs lead to produce structural RAC without affecting its mechanical and the durability performance.

      PubDate: 2017-09-13T20:39:58Z
       
  • Greening effect in slag cement materials
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Domitille Le Cornec, Qirong Wang, Laurence Galoisy, Guillaume Renaudin, Laurent Izoret, Georges Calas
      This article presents the first spectroscopic data describing the processes responsible for the temporary blue-green coloration that forms during the hydration of various materials containing Ground Granulated Blast-furnace Slag (GGBS) under anoxic conditions. UV-visible-near infrared Diffuse Reflectance (DR) spectra demonstrate a striking similarity of the coloring center forming during the curing of a broad range of GGBS-bearing materials (pure GGBS with different compositions, mix Portland cement/GGBS (30/70), concrete and mortar). All spectra are similar to those of polysulfide complexes contained in the interlayer spacing of a synthetic green-colored hydrated calcium aluminate phase (AFm). This “greening effect” demonstrates a progressive oxidation of sulfide-based compounds initially contained in these materials during curing of GGBS bearing materials.

      PubDate: 2017-09-13T20:39:58Z
       
  • Material characterisation of macro synthetic fibre reinforced concrete
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Ali Amin, Stephen J. Foster, R. Ian Gilbert, Walter Kaufmann
      In this paper, the post cracking behaviour of macro synthetic polypropylene fibre reinforced concrete is investigated through a series of matched tests that measure tension directly through uniaxial tension tests and indirectly through prism bending and determinate round panel tests. An analytical model previously developed by the authors for the determination of the residual tensile strength provided by steel fibres in prism bending tests is adapted for the round panel tests and is shown to correlate well with the collected experimental data.

      PubDate: 2017-09-13T20:39:58Z
       
  • IFC - Editorial board
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83


      PubDate: 2017-09-13T20:39:58Z
       
  • Synergistic chemical and microbial cementation for stabilization of
           aggregates
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Hannah Porter, Navdeep Kaur Dhami, Abhijit Mukherjee
      The use of Portland cement as a stabilizer of granular materials such as sand, is comparable to that in concrete. Although a relatively small percentage of cement is used for a stabilized soil system, the consumption of cement in Australian road bases and mining backfills is only second to the concrete industry. Conventionally, Portland cement is used as a binder for these applications. This paper explores low embodied energy alternative binders such as geopolymers and microbial cementation. A combination of the chemical and microbial binders has been attempted. The performance of the stabilized systems in terms of compressive strength, elastic modulus and water absorption was determined. It is noted that the chemical and the microbial cementation work synergistically. A microstructural investigation has been performed to reveal the synergistic nature of the two binding systems. The new technology is able to significantly reduce the embodied energy and emission of stabilized granular materials.

      PubDate: 2017-09-13T20:39:58Z
       
  • Influence of recycled coarse aggregates on permeability of fresh concrete
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Jean-Claude Souche, Philippe Devillers, Marie Salgues, Eric Garcia Diaz
      The following work is an experimental study of the behaviour of very early-age concrete. Six different concretes, four of them containing recycled coarse aggregates were studied for the first 2.5 h. The studies were carried out in a ventilated tunnel in order to imitate severe desiccation conditions. In order to indirectly obtain the permeability coefficient, settlement, capillary depression and evaporation were measured for all six concretes. The initial permeability coefficient of each concrete is determined starting from initial bleeding rate. The use of recycled coarse aggregates leads to a high bleeding rate for high water to cement ratios. Permeability coefficients at air entry are then determined starting from capillary depression gradients. Recycled coarse aggregates do not seem to influence the air entry value which is highly dependent on the paste quality. At air entry, the permeability coefficient of recycled coarse aggregates concrete mixes is higher than that of natural aggregates concrete mixes. At high evaporation rates, in severe desiccation conditions, recycled coarse aggregates seem to reduce bleeding for mixture with low water cement ratios. Permeability coefficient is a key physical parameter to understand drying of fresh concrete.

      PubDate: 2017-09-13T20:39:58Z
       
  • Assessment of pore structure evolution in the limestone calcined clay
           cementitious system and its implications for performance
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Yuvaraj Dhandapani, Manu Santhanam
      Use of limestone and calcined clay together for clinker substitution makes an effective low clinker cement blend, which shows promising mechanical properties at early ages. The performance of these cementitious systems strongly depends on the pore structure, which is a dominant factor governing the durability characteristics because of its direct influence on the transport properties. The experimental study described in this paper on three different binder systems including Ordinary Portland Cement, Portland Pozzolana Cement - with 30% Type F Fly Ash (designated FA30) - and Limestone Calcined Clay Cement (LC3) pastes shows that the LC3 system attains greater refinement of the pore structure as early as 3 days, as seen from mercury intrusion porosimetry. Electrical measurements also reveal lower conductivity in the system, which suggests better resistance to ionic transport in the binder phase. The results of hydrate phase assemblage studied by X-ray diffraction also indicate that greater amount of hydrates contribute in a major way to the reduction in the (water-filled) porosity in all the systems. This change occurs at varying rates for the different systems due to the difference in hydration characteristics. The estimated permeability suggests that the LC3 binder system attains much lower permeability compared to the ordinary Portland cement and FA30. A comparison of the formation factor shows distinct differences in the microstructural development and suggests a more durable binder with LC3 cementitious system.

      PubDate: 2017-09-07T20:37:36Z
       
  • Acoustic characterization of damage and healing of
           microencapsulation-based self-healing cement matrices
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Wenting Li, Zhengwu Jiang, Zhenghong Yang
      Self-healing of cracks in cementitious composites is of great significance to improve the serviceability of concrete structures. In this study, poly urea–formaldehyde (PUF) microcapsules enclosing epoxy resins were synthesized. The damage- and healing process of cement paste incorporating microcapsules was in situ detected by acoustic emission (AE) technique, in which passive AE and active AE were combined to provide complementary information about the damage and crack formation. The two representative AE signals, i.e., matrix cracking and debonding of the interface, were used as calibration for further AE post-processing analysis. The effects of the concentration of microcapsules and the level of pre-damage were investigated. The results revealed the distinguished cracking mechanisms according to the differentiated feature of the signals in terms of the temporal and spectral AE descriptors. The plot of average frequency (AF) versus RA index (rise time/amplitude) confirms that the cracking modes contribute to the characteristic spectrum.

      PubDate: 2017-09-07T20:37:36Z
       
  • Damage model for simulating chloride concentration in reinforced concrete
           with internal cracks
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Mao Kurumatani, Hisashi Anzo, Kenji Kobayashi, Shinichiro Okazaki, Sohichi Hirose
      We present a method to simulate, in three dimensions, the concentration of chloride ions that penetrate into concrete with internal cracks. The method comprises the crack-propagation analysis of concrete and the diffusion analysis of chloride ions. A finite-element model with a damage model that is based on fracture mechanics for concrete was applied in the crack-propagation analysis, and we were able to reproduce the three-dimensional geometry of the internal cracks. Chloride-ion transfer through internal cracks was simulated by diffusion analysis with the simultaneous consideration of damage, and a diffusion coefficient that was expressed as a function of the damage variable obtained from crack-propagation analysis. We present a formulation of crack-propagation analysis by using the damage model and unsteady-diffusion analysis in consideration of damage. We also present a verification analysis of internal cracking in concrete to demonstrate that the crack width and the chloride concentration can be evaluated without mesh dependency. This is followed by a validation analysis. A comparison between the numerical and experimental results shows that the proposed method enables the high-accuracy simulation of chloride penetration into concrete with internal cracks.

      PubDate: 2017-09-07T20:37:36Z
       
  • Pressure-sensitive properties of emulsion modified graphene
           nanoplatelets/cement composites
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Jiaming Xu, Dong Zhang
      Graphene nanoplatelets(GNP)/cement composites were prepared using three types of GNP with different structures. In order to investigate the effects of GNP and styrene-acrylate emulsion on properties of GNP/cement composites, GNP with different addition (0-2.0 wt%) and styrene-acrylate emulsion (10 wt%) were mixed into cement through the method of mechanical stirring. Electrical performance and the pressure-sensitive property of GNP/cement composites were studied. The results showed that the addition of GNP to cement would lead to a significant drop of resistivity and make composites manifest pressure sensitivity. In addition, the structure (C/O atomic ratio) of GNP greatly affected the properties of the GNP/cement composites. A distinct enhancement in pressure sensitivity was found when emulsion was added to GNP/cement composites. The gauge factor of emulsion modified GNP/cement composites reached a peak value of 7.783, which was 1 order of magnitude higher than composites without emulsion. This work offered a new opportunity to make use of traditional cement materials combining with GNP.

      PubDate: 2017-09-07T20:37:36Z
       
  • Effects of CaCl2 on hydration and properties of lime(CaO)-activated
           slag/fly ash binder
    • Abstract: Publication date: Available online 5 September 2017
      Source:Cement and Concrete Composites
      Author(s): Woo Sung Yum, Yeonung Jeong, Seyoon Yoon, Dongho Jeon, Yubin Jun, Jae Eun Oh
      This study presented CaCl2 as a potential additive activator to develop a new strong, price-competitive CaO-activated GGBFS binder blended with fly ash (CAS 4:4:2) to commercially replace ternary blended cements, which generally consist of 40% Portland cement, 40% GGBFS, and 20% fly ash (wt.%) (PC 4:4:2), widely used for concrete production. Despite CAS 4:4:2 having no clinker cement compound, the addition of CaCl2 not only significantly accelerated reactions of CAS 4:4:2 binders but also largely increased strengths at all curing days. Up to 72 h, the cumulative reaction heat of CAS 4:4:2 with CaCl2 was also reasonably low. Reaction products and microstructures of hardened CAS 4:4:2 pastes were considerably changed after CaCl2 addition. The CaCl2 presence markedly promoted dissolution of the glass phase of GGBFS and fly ash in early days, resulting in more production of reaction products (e.g., C-S-H, hydrocalumite) and pore-size refinement.

      PubDate: 2017-09-07T20:37:36Z
       
  • Chloride binding capacity of pastes influenced by carbonation under three
           conditions
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Honglei Chang
      This research investigates the influence of carbonation on chloride binding capacity under three conditions varying in the sequence and way of carbonation-chloride contact: I, hardened pastes first carbonated then contacted with chloride; II, hardened pastes first contacted with chloride then carbonated; III, pastes inner-introduced with chloride during casting, hardened and then carbonated. The results indicate that, before carbonation, the bound chloride content of pastes inner-introduced with chloride is slightly higher than that of pastes first hardened then contacted with chloride because more Friedel's salt is formed through the former way. And during the carbonation process, the remaining bound chloride content mainly depends on the content of un-carbonated C-S-H gel. And based on the content of it before total carbonation, the content of residual bound chloride in samples under condition I is higher than that under the other two conditions after the same carbonation time. After complete carbonation, the bound chloride content under the three conditions all approximates to zero, which indicates that carbonation makes paste lose chloride binding capacity completely.

      PubDate: 2017-09-01T20:35:21Z
       
  • Using ultrasonic wave reflection to monitor false set of cement paste
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Chul-Woo Chung, Prannoy Suraneni, John S. Popovics, Leslie J. Struble
      The standard mechanical penetration approach for monitoring cement paste stiffening (Vicat needle method, ASTM C191) does not distinguish responses associated with false set of cement paste caused by secondary gypsum formation. The objective of this research is to determine whether ultrasonic wave reflection, using a testing set up with high measurement sensitivity, could be used to monitor false set of cement paste. Penetration resistance, P-wave, and S-wave reflection coefficients were measured on cement pastes with water-to-cement ratio 0.5. The S-wave reflection coefficient showed a sharp and abrupt linear drop associated with secondary gypsum formation, thereby indicating that S-wave ultrasonic wave reflection can be used to monitor false set of cement pastes. False set could not be distinguished in penetration resistance or P-wave UWR test data.

      PubDate: 2017-09-01T20:35:21Z
       
  • Alkali resistant glass fiber reinforced concrete: Pull-out investigation
           of interphase behavior under quasi-static and high rate loading
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Christina Scheffler, Serge Zhandarov, Edith Mäder
      Single fiber model composites of alkali resistant (AR-) glass fibers and a cementitious matrix were used to investigate the pull-out behavior under quasi-static and high speed loading. For fundamental understanding of the effect of the fiber/matrix interphase on the pull-out behavior under impact, differently sized AR-glass fibers were spun. As a first approach, the fiber surface was modified in oppositional ways using the following sizings: one based on a polypropylene (PP, weak) film former and another one based on a styrene-butadiene (strong) film former. Additionally, some of the fibers were kept unsized for comparison. A new ‘alternative’ approach was employed to determine the local interfacial shear strength, τ d , and the critical energy release rate, G ic , from the reliable force values of the force–displacement curves. For all fiber surface states, the τ d and G ic values for high loading rates appeared to be considerably greater than the corresponding parameters for a quasi-static pull-out test. This can be explained using a model based on Zhurkov's kinetic (thermal fluctuation) theory of the strength of solids, which also enabled to estimate the apparent activation energy for interfacial debonding. Both quasi-static and high-rate pull-out tests on this fiber/matrix pair can be considered as ‘normal’ (slip-dependent interfacial friction was not observed) and their results can be evaluated using the described approaches. The interfacial frictional stress reduced at high-rate pull-out tests for all systems. One of the possible mechanisms responsible for this behavior may be the smoothing of surface asperities upon debonding. As revealed by AFM of fracture surfaces, in the case of unsized fibers or those with the ‘strong’ styrene–butadiene sizing, the interfacial crack occurs through surface layers of the matrix material adjacent to the fiber, but it may propagate through the weak interface when the fiber is sized with ‘weak’ PP film former.

      PubDate: 2017-09-01T20:35:21Z
       
  • Effects of coarser fine aggregate on tensile properties of ultra high
           performance concrete
    • Abstract: Publication date: November 2017
      Source:Cement and Concrete Composites, Volume 84
      Author(s): Sukhoon Pyo, Hyeong-Ki Kim, Bang Yeon Lee
      This experimental research investigates the mechanical properties and shrinkage of ultra high performance concrete (UHPC) incorporating coarser fine aggregates with maximum particle size of 5 mm. To adequately design UHPC mixtures using various sizes of solid constituents, particle packing theory was adopted. UHPC mixtures containing either dolomite or basalt, and four fiber volume fractions up to two volume percent were investigated. Uniaxial tension test was performed to evaluate the first cracking tensile strength, ultimate tensile strength, tensile strain capacity and cracking pattern. The UHPC mixtures with dolomite and steel fibers with more than one volume percent achieved more than 150 MPa of compressive strength at the age of 56 days, and showed strain hardening behavior and limited decrease in tensile strength compared to typical UHPC without coarser fine aggregates. The experimental results highlight the potential of dolomite used as coarser fine aggregate in UHPC.

      PubDate: 2017-09-01T20:35:21Z
       
  • Evaluation of water content gradient using a new configuration of linear
           array four-point probe for electrical resistivity measurement
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): A.Q. Nguyen, G. Klysz, F. Deby, J.-P. Balayssac
      Electrical resistivity is used in this study to assess the moisture content of concrete, because of their good correlation. A new process using four point probes to measure the electrical resistivity of concrete is described in this paper. It is based on the exploitation of the short circuit induced by the reinforcement in the concrete structure. A numerical model is also made to simulate the resistivity measurements on concrete by taking into account the electrochemical parameters of the reinforcement. The obtained results have shown the ability of the new measurement process to assess the gradient of the moisture content of the concrete cover.

      PubDate: 2017-09-01T20:35:21Z
       
  • Early age electrical resistivity behaviour of various concrete mixtures
           subject to low temperature cycling
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Douglas Tomlinson, Farid Moradi, Hamzeh Hajiloo, Pouria Ghods, Aali Alizadeh, Mark Green
      The effect of thermal cycling between −24 and + 24 °C on the electrical resistivity of five concrete mixtures was investigated at early-ages. Each mixture was subjected to two thermal cycles (initiated either 1 or 14 days after casting) wherein temperatures were changed by 1 °C/h. Electrical resistivity increased as temperature decreased. This relationship followed the Arrhenius equation until the phase transition temperature (i.e. initial freezing of the pore solution), at which point electrical resistivity increased greatly. A method of determining the phase transition temperature is presented that could be used in place of existing methods using mortar cubes. The phase transition temperature was higher during thawing cycles compared to freezing cycles for all mixtures. Mixtures with ground slag replacing cement had higher resistivity and lower phase transition temperatures than mixtures using only cement due to the change in the ionic combination of the concrete pore solution. The phase transition temperature decreases as concrete ages.

      PubDate: 2017-09-01T20:35:21Z
       
  • Manufacturing of lightweight aggregates with carbon fiber and mineral
           wastes
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): José Manuel Moreno-Maroto, Beatriz González-Corrochano, Jacinto Alonso-Azcárate, Luis Rodríguez, Anselmo Acosta
      The use of carbon fiber wastes (FC) as a component to manufacture lightweight aggregates (LWAs) for concrete has been studied. Amounts of 0, 2.5, 5 and 10% (w/w) of powdered FC were added into a mineral matrix composed by 90% of granite-marble sludge (COR) plus 10% of sepiolite rejection (SEP). The mixtures were milled, kneaded with water, extruded, shaped into pellets, oven-dried and finally fired at 1100, 1125 and 1150 °C for 4, 8 and 16 min in a rotary kiln. The main technological properties of the sintered aggregates were measured. The addition of FC promoted bloating and the formation of an internal structure in which both pores and unburnt carbon fibers were present. Improvements in lightness and mechanical properties were also observed. This is the first time that carbon fibers have been embedded within aggregates, opening the way to the development of a new type of LWAs for concrete.

      PubDate: 2017-09-01T20:35:21Z
       
  • Effects of loading rate and notch-to-depth ratio of notched beams on
           flexural performance of ultra-high-performance concrete
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Weina Meng, Yiming Yao, Barzin Mobasher, Kamal Henri Khayat
      This paper addresses the effects of loading rate and notch-to-depth ratio on flexural properties of ultra-high-performance concrete (UHPC) notched beam specimens, in order to enable use of standardized laboratory test data to predict flexural properties of UHPC structures that have different dimensions and are subjected to a range of loading rates. UHPC notched beams were tested in three-point bending to study the effects of three notch-to-depth ratios of 1/6, 1/3, and 1/2 at five loading rates of 0.05, 0.50, 1.25, 2.50, and 5.00 mm/min on flexural performance. Test results indicate that loading rate and notch-to-depth ratio have significant effects on flexural properties of the UHPC notched beams. The flexural strength is shown to increase with the loading rate and the notch-to-depth ratio. The fracture energy increases with the loading rate but decreases with the notch-to-depth ratio. The changes of flexural properties with the loading rate are also dependent on the notch-to-depth ratio. Regression analyses to correlate flexural properties associated with the loading rate and notch-to-depth ratio were conducted to obtain parameters for UHPC structures.

      PubDate: 2017-09-01T20:35:21Z
       
  • Quantitative mineralogical mapping of hydrated low pH concrete
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Stéphane Gaboreau, Dimitri Prêt, Valérie Montouillout, Pierre Henocq, Jean-Charles Robinet, Christophe Tournassat
      Concrete materials are made of various minerals and phases, whose spatial heterogeneous distributions impact the overall physical and chemical properties of the materials. We have investigated the heterogeneous distribution of minerals and phases in two types of concrete using quantitative X-ray intensity maps coupled with an innovative data treatment method based on image segmentation. This method provided quantitative data on spatial distribution, modal content and associated calculated formulas for each identified mineral and phase in the binder with micrometer resolution. We also obtained quantitative information on the porosity associated with the phases, making it possible to differentiate poorly hydrated cement phases (initial clinker hydration reaction) from highly hydrated phases (final cement product) despite their similar chemical composition, when expressed in terms of cationic formulas. We quantified the mineralogical and phase contents, independent of crystal size or crystallinity considerations. We report spatial resolution in the pozzolan hydration process over different observation scales for the two investigated concretes.

      PubDate: 2017-09-01T20:35:21Z
       
  • Lime-based plasters with combined expanded clay-silica aggregate:
           Microstructure, texture and engineering properties
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Dana Koňáková, Monika Čáchová, Eva Vejmelková, Martin Keppert, Miloš Jerman, Patrik Bayer, Pavla Rovnaníková, Robert Černý
      Plasters containing lightweight aggregates are mostly characteristic by low bulk density and low thermal conductivity but these favorable properties are often achieved at the expense of mechanical strength. In this paper, lightweight lime-based plasters are designed which have good thermal and mechanical properties at the same time. As their supposed applications include the renovation of surface layers of historical buildings, burnt clay shale is used as pozzolanic admixture to lime. The volumetric ratio of silica sand and expanded clay aggregate (ECA) is varied over a wide range to analyze the effect of ECA on microstructure, texture, and mechanical, thermal and hygric parameters of investigated plasters. The microstructural studies show a more compact interfacial transition zone between the basic lime-pozzolan matrix and ECA, as compared with silica sand, which is the most important factor affecting the properties of studied plasters. Apparently, the surface roughness of ECA grains at first makes possible easier formation of hydration products and later it can support the growth of calcite crystals and CSH amorphous phases. The textural analysis together with the measurement of basic physical properties reveals, as the second principal factor, a substantial increase of open porosity with the increasing ECA dosage; the added pores are mostly within the range of 10 nm to 1 μm. The assessment of the wide range of engineering properties of designed plasters leads to the identification of the lime-pozzolan plaster with the volumetric ratio of 1: 1 between silica sand and ECA as the most appropriate solution. The thermal conductivity of this plaster is two times lower than of the lime-pozzolan plaster with silica aggregates, while the changes in compressive and bending strengths are only marginal. The favorable hygric properties can be considered as another asset. Faster water vapor transport, together with the higher water vapor adsorption capability, can decrease a risk of water condensation and moderate the effects of both exterior and interior climate, the relatively slow liquid water transport is a limiting factor for rainwater penetration. The economical parameters of the plaster with the best functional properties are also very good. According to the current situation on the Czech market, the price increase is only 3%, as compared with the reference mix.

      PubDate: 2017-09-01T20:35:21Z
       
  • Influence of phosphorus from phosphogypsum on the initial hydration of
           Portland cement in the presence of superplasticizers
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Fernando do Carmo Holanda, Holger Schmidt, Valdecir Angelo Quarcioni
      Phosphogypsum is widely used for the total or partial substitution of natural gypsum in the production of Portland cement. However, contaminants from the phosphogypsum, such as chemicals that contain phosphorus, may affect the performance of the binder, especially when it is applied to concrete that uses chemical admixture. The goal of this study is to evaluate the impact of successive increments of Na2HPO4 on the hydration of cements that are produced with low or high phosphorus concentrations in the presence of ether–polycarboxylate–based (PCE) and sulfonated–naphthalene–formaldehyde–based (SNF) superplasticizers. Two binders with the same clinker size were produced in the laboratory with natural (phosphorus–free) gypsum and phosphogypsum (contaminated). The isothermal calorimetry and thermogravimetry (TG/DTG) techniques were used to evaluate the heat flow behavior and the formation of portlandite at the end of the induction period (Pi), at the maximum heat flow (Pmax), and at the final 72-h stage (P72). The results indicate that the greatest impact on hydration occurs at phosphorus concentrations between 0.83% and 1.64% in the form of P2O5 in the phosphogypsum and especially at a concentration of 1.13%. Nonetheless, in all cases, the formation of portlandite after 72 h is very similar.

      PubDate: 2017-09-01T20:35:21Z
       
  • Effect of constituents on rheological properties of fresh concrete-A
           review
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Dengwu Jiao, Caijun Shi, Qiang Yuan, Xiaopeng An, Yu Liu, Huang Li
      The rheology is an effective tool to characterize workability, consistency, flowability, and predict stability, pumpability, shootability, pressure of formwork, multi-layer casting. This paper presents a critical review on the rheological properties of fresh concrete in recent publications. The applicable rheological models for the flow of concrete are revealed. The effects of constituents of fresh concrete, including cement, supplementary cementitious materials (fly ash, ground blast furnace slag, and silica fume), limestone powder, coarse and fine aggregates, and chemical admixtures (superplasticizer, viscosity modifying agent and air-entraining agent) on the rheological properties are discussed in detail. The applications of rheograph and workability box in mixture proportioning and quality control are also illustrated.

      PubDate: 2017-08-03T09:23:12Z
       
  • Use of biochar-coated polypropylene fibers for carbon sequestration and
           physical improvement of mortar
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Souradeep Gupta, Harn Wei Kua, Sin Yee Tan Cynthia
      Biochar is widely recognized as an effective material for sequestration of carbon dioxide. The possibility of using it as a coating material on polypropylene fibers to improve mechanical properties and permeability mortar is explored in this study. Effectiveness of two types of biochar – fresh biochar and biochar saturated with carbon dioxide prior to application as coating – on compressive and flexural strength, post-cracking behavior and permeability of mortar is studied. The biochar used was derived from mixed wood saw dust by pyrolysis at 300 °C. Experimental results show that application of fresh biochar coating offer significant improvement in compressive strength and flexural strength of mortar. Residual strength and post-cracking ductility of mortar with biochar coated fibers is found to be higher than control samples, although fresh biochar coating offers the best performance. Mortar with polypropylene fibers coated with fresh biochar shows higher impermeability, compared to reference samples and mortar with saturated biochar coated fibers. The findings suggest that biochar coating could be a potential solution to improve properties of fiber reinforced cementitious composites that also promotes waste recycling and carbon sequestration.

      PubDate: 2017-08-03T09:23:12Z
       
  • Performance of rice husk ash blended cementitious systems with added
           superplasticizers
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Nsesheye Susan Msinjili, Wolfram Schmidt, Andreas Rogge, Hans-Casrten Kühne


      PubDate: 2017-08-03T09:23:12Z
       
  • Mortar crack repair using microbial induced calcite precipitation method
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Sun-Gyu Choi, Kejin Wang, Zhiyou Wen, Jian Chu
      An experimental investigation has been carried out to repair pre-existing cracks in mortar using the microbiologically induced calcium carbonate precipitation (MICP) technology. In the study, 20 cylinder mortar samples (50 mm in diameter and 40 mm in height) were split to have cracks with various sizes. Sixteen of the cracked samples, an average width ranging from 0.15 to 1.64 mm, were repaired using the MICP method, while four cracked samples, with an average width ranging from 0.17 to 1.72 mm, were soaked under distilled water. The water permeability and splitting tensile strength (TS) of these repaired mortars were tested. The amounts of calcium carbonate (CaCO3) precipitated on the cracked mortar surfaces were evaluated. The morphology of the CaCO3 was observed under a scanning electron microscope (SEM). The results indicated that the MICP repair technique clearly reduced water permeability of the cracked samples. While water-treated samples were too weak to test, the MICP-repaired samples had TS ranging from 32 to 386 kPa after 21 cycles of MICP solution treatment. A relationship between the TS and amount of CaCO3 precipitated was observed for samples with an average crack width between 0.52 and 1.1 mm, which indicated that TS increased with the amount of CaCO3 precipitated on the crack surfaces. The SEM revealed that the precipitated CaCO3 had possibly two forms: vaterite and calcite.

      PubDate: 2017-08-03T09:23:12Z
       
  • Estimation of the tensile strength of UHPFRC layers based on
           non-destructive assessment of the fibre content and orientation
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): S. Nunes, M. Pimentel, F. Ribeiro, P. Milheiro-Oliveira, Adriano Carvalho
      In the present study we propose a procedure for estimating the tensile strength of thin ultra-high performance fibre-reinforced cement-based composite (UHPFRC) layers, which eliminates the need of extracting cores or samples from the structure. This procedure relies on a non-destructive testing (NDT) method based on the ferromagnetic properties of the steel fibres for estimating the parameters of the underlying physical model, namely, the fibre content and the fibre orientation factor, and on laboratory tensile tests for estimating the equivalent rigid-plastic fibre-to-matrix bond strength. An experimental program was developed for establishing the relation between the NDT measurements and the orientation parameters determined from image analysis. Following the proposed procedure, the tensile strength of 36 specimens with varying fibre content and fibre orientation distributions is estimated based on the magnetic measurements and compared to experimental results. The good correlation that is found demonstrates the significance of the proposed NDT method in the implementation of quality control procedures of thin UHPFRC elements/layers.

      PubDate: 2017-08-03T09:23:12Z
       
  • Modeling basic creep of concrete since setting time
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): B. Delsaute, J.-M. Torrenti, S. Staquet
      Modeling the early age evolution of concrete properties is necessary to predict the early age behavior of structures. In case of restrained shrinkage or application of prestress load [1], creep plays an important role in the determination of the effective stress. The difficulty lies in the fact that the modeling of creep must be based on experimental data at early age and this data must be obtained automatically because the hardening process of the concrete takes place rapidly during the first hours and also the first days. This paper presents a new methodology to model basic creep in compression since setting. Two kinds of tests are used: classical loadings and repeated minute-scale-duration loadings. The classical test is used to characterize the creep function for one age at loading and the repeated minute-scale-duration loadings test is used to define two ageing factors for the creep function. A new model based on the physical mechanisms and the two ageing factors is presented. A comparison with the Model Code 2010 is done and an advanced way to consider ageing with the Model Code 2010 is presented.

      PubDate: 2017-08-03T09:23:12Z
       
  • Valorisation of alumino-silicate stone muds: From wastes to source
           materials for innovative alkali-activated materials
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Paola Palmero, Alessandra Formia, Jean-Marc Tulliani, Paola Antonaci
      Impressive amounts of wastes are produced yearly by extraction and transformation of natural stones. This work addresses the finest fraction of these wastes, named stone muds, and particularly those with a siliceous composition. The disposal in dump of these muds implies high costs, whereas their surface landing poses serious challenges, since they can damage the environment, create necrotic conditions for flora and fauna, and endanger human health. Therefore, the reemployment of these wastes is today an urgent need. In this work, a mud (QM) composed by quartz, feldspars, biotite and dolomite, is used for producing dense and foamed alkali-activated materials through an innovative and simple process, in which a mixture of mud and alkaline solution (plus foaming agent, when needed) is produced, cast in moulds and cured at 80 °C for 48 h. Another mineral powder (SRM), having a similar composition but carbonates-free, was also used, to prove the key role of alumino-silicates in producing dense alkali-activated materials, with excellent mechanical properties. Also, the foamed samples showed good mechanical properties, plus low thermal conductivity. These results demonstrate that alumino-silicate wastes could serve as source materials for producing materials suitable to be used for dense and cellular building elements, providing an effective alternative to mud disposal and related issues.

      PubDate: 2017-08-03T09:23:12Z
       
  • External sulfate attack of cementitious materials: New insights gained
           through numerical modeling including dissolution/precipitation kinetics
           and surface complexation
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Anthony Soive, Van Quan Tran
      In this study, a new physically and chemically coupled model taking into account multiionic diffusion, precipitation/dissolution kinetics and surface complexation is proposed to predict the ingress of sulfate ions into saturated cementitious materials. The results are compared to experimental data and numerical profiles that were previously obtained on the total sulfate concentration profile in the material. The results show good agreement between experimental and numerical results. They also show that surface complexation has to be taken into account in order to reproduce the sulfate quantity peak experimentally observed. In addition, dissolution and precipitation kinetics are indispensable to retrieve the sulfate quantity amplitude and still more the slow decay of the sulfate quantity after the peak. Finally, the model may explain the supersaturation of the sulfate concentration with respect to ettringite because of the dissolution of monosulfoaluminate and ettringite precipitation kinetics. Moreover, it shows that the supersaturation increases with the concentration of the aggressive sulfate solution without significant increase in the total quantity of sulfate in the material. These results are coherent with the crystallization pressure theory.

      PubDate: 2017-08-03T09:23:12Z
       
  • Examining the pozzolanicity of supplementary cementitious materials using
           isothermal calorimetry and thermogravimetric analysis
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Prannoy Suraneni, Jason Weiss
      It has recently been proposed that the pozzolanicity of supplementary cementitious materials can be determined by monitoring the heat released when supplementary cementitious materials are mixed with calcium hydroxide at high temperature and high pH. In this study, the heat release is measured using this procedure for a variety of different supplementary cementitious materials. In addition, thermogravimetric analysis is performed on the reacted material to determine the amount of calcium hydroxide consumed. The heat release and calcium hydroxide consumption can be used in conjunction to compare supplementary cementitious materials. Calcium hydroxide consumption can be used to determine the extent of reaction of supplementary cementitious materials in pastes where supplementary cementitious materials are used to replace a portion of cement.

      PubDate: 2017-08-03T09:23:12Z
       
  • Photocatalytic NOx degradation of concrete surface layers intermixed and
           spray-coated with nano-TiO2: Influence of experimental factors
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Ming-Zhi Guo, Tung-Chai Ling, Chi Sun Poon
      TiO2 incorporated Eco-blocks have been successfully developed and widely used worldwide. However, under real-life service, various environmental factors will significantly influence their photocatalytic performance. In this study, the photocatalytic NOx conversion of two sets of concrete surface layers (intermixed and spray-coated with nano-TiO2) was investigated and compared under different NO flow rates, initial NO concentrations, ultraviolet (UV) light intensities, light sources and relative humidity (RH) conditions. In addition, the abrasion resistance of all the samples was examined. The results showed that the TiO2 spray-coated samples (SP) outperformed the 5% TiO2-intermixed samples with respect to NOx removal efficiency under all the investigated conditions. Both the NO flow rate and initial NO concentration had a positive impact on the NOx removal rate but a negative influence on the NOx removal ratio. An increase in photocatalytic NOx removal rate and NOx removal ratio was attained by an increase in UV light intensity. Whereas, the NOx removal efficiency first increased, reached a peak, and then decreased with increasing RH. It was found that the most effective light source for photocatalytic NOx removal was UV-A, but Solar light (SL) irradiation resulted in a comparable NOx removal. Moreover, the SP samples harboured robust resistance to abrading. The findings from this study would provide the basis for effectively evaluating the NOx removal performance of concrete surface layers under atmospheric conditions.

      PubDate: 2017-08-03T09:23:12Z
       
  • Numerical simulation of self-consolidating concrete flow as a
           heterogeneous material in L-Box set-up: Effect of rheological parameters
           on flow performance
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Masoud Hosseinpoor, Kamal H. Khayat, Ammar Yahia
      A computational fluid dynamics (CFD) software was used to simulate the effect of rheological parameters on the heterogeneous performance properties of self-consolidating concrete (SCC) in the horizontal and vertical directions of the L-Box set-up. These properties consist of flowability, blocking resistance, and dynamic segregation. Different suspending fluids having five plastic viscosity values (10–50 Pa.s), three yield stress values (14–75 Pa), two fluid densities (2000 and 2500 kg/m3), and two shear elasticity modulus values (100 and 1000 Pa) were considered. The suspensions consisted of a number of 135 in total spherical particles with 20-mm in diameter and 2500 kg/m3 density. The results of 25 simulations in total are found to correlate well with the rheological parameters of the suspending fluid. Plastic viscosity of the suspending fluid was shown to be the most dominant parameter affecting flow performance of SCC in the L-Box test. A new approach was also proposed to classify SCC mixtures based on the filling ability properties.

      PubDate: 2017-08-03T09:23:12Z
       
  • Effect of substrate moisture on the weatherability of surface treatment
           for High-Performance Concrete (HPC)
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Tobias Bader, Seraphin Hubert Unterberger, Roman Lackner
      Surface treatments are applied to protect concrete from the penetration of water with the purpose of retarding degradation and/or aesthetic deterioration. Several studies have shown that the penetration behaviour of surface treatments for ordinary concrete depends on the substrate moisture content which in turn influences its service life. The role of moisture content in case of surface treatments applied to High-Performance Concrete (HPC) seems to be questionable due to the reduced near-surface permeability and diminished capillary water uptake of HPC. In this paper, the effect of different moisture contents (4, 6, 8 wt.-%) representing dry, medium and wet conditions on the penetration behaviour and the subsequent weatherability of acrylic resin coating are evaluated by means of artificial weathering over a period of 2160 h. Based on the obtained results, the penetration of the used acrylic resin is considered to be hindered by a filter effect due to the reduced pore size in the near-surface area of HPC. Thus, the aqueous dispersion of acrylic resin is separated into solvent (penetrating into the HPC) and active agent (remaining on its surface). With ongoing artificial weathering incremental colour change (brightening) and delamination of the surface treatment are observed, with the extent being more pronounced for specimens with moisture contents of 6 and 8 wt.-%. The observed differences in weathering are considered to be the result of differences in the moisture absorption of the acrylic film. This in turn is mostly related to the saponification of the acrylic resin resulting in the formation of hygroscopic carboxylic acid salts due to the alkaline environment of HPC. Thus, moisture contents of 6 and 8 wt.-% are suspected to facilitate the degradation of the coating by the alkaline pore solution, which increases the extent of saponification making the film more prone to the absorption of moisture. For 4 wt.-% moisture content, on the other hand, the extent of saponification is marginal resulting in only slight changes in colour and a minor degree of delamination.

      PubDate: 2017-07-23T09:14:25Z
       
  • Effects of autogenous healing on the recovery of mechanical performance of
           High Performance Fibre Reinforced Cementitious Composites (HPFRCCs): Part
           1
    • Abstract: Publication date: October 2017
      Source:Cement and Concrete Composites, Volume 83
      Author(s): Liberato Ferrara, Visar Krelani, Fabio Moretti, Marta Roig Flores, Pedro Serna Ros
      This paper presents the results are shown of a thorough characterization of the self-healing capacity of High Performance Fibre Reinforced Cementitious Composites (HPFRCCs). The capacity of the material will be investigated to completely or partially re-seal the cracks, as a function of its composition, maximum crack width and exposure conditions. The analysis will also consider different flow-induced alignments of fibres, which can result into either strain-hardening or softening behaviour, whether the material is stressed parallel or perpendicularly to the fibres, respectively. Beam specimens, initially pre-cracked in 4-point bending up to different values of crack opening, were submitted to different exposure conditions, including water immersion, exposure to humid or dry air, and wet-and-dry cycles. After scheduled exposure times, ranging from one month to two years, specimens were tested up to failure according to the same test set-up employed for pre-cracking. Outcomes of the self-healing phenomenon, if any, were analysed in terms of recovery of stiffness, strength and ductility. In a durability-based design framework, self-healing indices quantifying the recovery of mechanical properties were also defined and their significance cross-checked.

      PubDate: 2017-07-23T09:14:25Z
       
  • Accelerated carbonation and performance of concrete made with steel slag
           as binding materials and aggregates
    • Abstract: Publication date: Available online 23 July 2017
      Source:Cement and Concrete Composites
      Author(s): Liwu Mo, Feng Zhang, Min Deng, Fei Jin, Abir Al-Tabbaa, Aiguo Wang
      Steel slag has been used as supplementary cementitious materials or aggregates in concrete. However, the substitution levels of steel slag for Portland cement or natural aggregates were limited due to its low hydraulic property or latent volume instability. In this study, 60% of steel slag powders containing high free-CaO content, 20% of Portland cement and up to 20% of reactive magnesia and lime were mixed to prepare the binding blends. The binding blends were then used to cast concrete, in which up to 100% of natural aggregates (limestone and river sands) were replaced with steel slag aggregates. The concrete was exposed to carbonation curing with a concentration of 99.9% CO2 and a pressure of 0.10 MPa for different durations (1d, 3d, and 14d). The carbonation front, carbonate products, compressive strength, microstructure, and volume stability of the concrete were investigated. Results show that the compressive strength of the steel slag concrete after CO2 curing was significantly increased. The compressive strengths of concrete subjected to CO2 curing for 14d were up to five-fold greater than that of the corresponding concrete under conventional moist curing for 28d. This is attributed to the formation of calcium carbonates, leading to a microstructure densification of the concrete. Replacement of limestone and sand aggregates with steel slag aggregates also increased the compressive strengths of the concrete subjected to CO2 curing. In addition, the concrete pre-exposed to CO2 curing produced less expansion than the concrete pre-exposed to moist curing during the subsequent accelerated curing in 60 °C water. This study provides a potential approach to prepare concrete with low-carbon emissions via the accelerated carbonation of steel slag.

      PubDate: 2017-07-23T09:14:25Z
       
  • Bond behavior and interface modeling of reinforced high-performance
           fiber-reinforced cementitious composites
    • Abstract: Publication date: Available online 22 July 2017
      Source:Cement and Concrete Composites
      Author(s): Matthew J. Bandelt, Timothy E. Frank, Michael D. Lepech, Sarah L. Billington
      High-performance fiber-reinforced cementitious-composites (HPFRCCs) reinforced with mild steel reinforcing bars have bond strengths that are higher than ordinary concrete under monotonic loading conditions. High bond strengths in HPFRCCs have been attributed to the material toughness of HPFRCCs, which effectively restrains splitting cracks under monotonic loads. Characterization of the interface between HPFRCCs and mild reinforcement under cyclic loads remains largely unknown. The bond-slip behavior of two HPFRCC mixtures are examined under monotonic and cyclic loads in beam-end flexural specimens. Bond strength is shown to deteriorate due to cyclic load reversals after the maximum bond stress is reached, resulting in lower bond-slip toughness. Three dimensional computational simulations are conducted to investigate observed crack patterns and internal deformations at the interface of the HPFRCC and steel reinforcement. Numerical simulation results predicted splitting crack patterns observed in physical experiments, and also suggest that interface crushing occurs at the intersection of the reinforcement lugs and HPFRCC material. Further, simulated performance shows that damage to the bond interface is altered by the deformation history applied to the interface.

      PubDate: 2017-07-23T09:14:25Z
       
  • The role of fly ash microsphere in the microstructure and macroscopic
           properties of high-strength concrete
    • Abstract: Publication date: Available online 21 July 2017
      Source:Cement and Concrete Composites
      Author(s): Wang Qiang, Wang Dengquan, Chen Honghui
      This study applied a type of fly ash microsphere (FAM) collected directly from a high-temperature furnace using ceramic dust tubes to high-strength concrete, and with silica fume as a control admixture, investigated the effects of FAM on the hydration and hardening processes of the cementitious materials and the macroscopic properties of the high-strength concrete. Two cement replacement levels (8% and 15%) and two water-to-binder (W/B) ratios (0.35 and 0.25) were utilized. The results show that FAM has a relatively high level of early activity; SEM images indicate that a significant portion of the FAM reacted at early ages in the cement-FAM hardened paste. Though the early activity of FAM is lower than that of silica fume, the cement-FAM complex binder has similar hydration properties with the cement-silica fume complex binder. At 90 d, FAM consumed less Ca(OH)2 than silica fume and a significant amount of unreacted FAM remained in the hardened pastes. The contributions of FAM to the pore structure of the hardened pastes are lower than those of silica fume at early ages; however, FAM can significantly improve pore structure at late ages, similar to silica fume. In addition, FAM can improve the flowability, late-age strength, and permeability to chloride ions of concrete, while decreasing early-age autogenous shrinkage.

      PubDate: 2017-07-23T09:14:25Z
       
  • Synthesis of low-temperature calcium sulfoaluminate-belite cements from
           industrial wastes and their hydration: Comparative studies between lignite
           fly ash and bottom ash
    • Abstract: Publication date: Available online 8 July 2017
      Source:Cement and Concrete Composites
      Author(s): A. Rungchet, C.S. Poon, P. Chindaprasirt, K. Pimraksa
      The aim of this research was to study the production of calcium sulfoaluminate-belite (CŜAB) cement from industrial waste materials via hydrothermal-calcination process. Lignite fly ash and bottom ash were used as starting materials for comparison. Other waste materials viz., Al-rich sludge and flue gas desulfurization gypsum were also key players in raw mixes for the synthesis of CŜAB cement. For lignite fly ash as a starting material, mixed phases between ye’elimite and larnite were obtained, whereas for lignite bottom ash as starting material, only ye’elimite was obtained The hydration reaction was studied in terms of heat evolution, setting time, compressive strength and hydration product formation with various gypsum contents. The results showed a rapid formation of ettringite as a main hydration product mixed with calcium silicate hydrate, monosulfate and strätlingite phases as minority, with a fast final setting time of 24-26 min and high early compressive strength of 16.0 and 18.0 MPa in 1 day for CŜAB cements made of fly ash and bottom ash, respectively.

      PubDate: 2017-07-09T09:06:00Z
       
  • Particle-based characterization of Ottawa sand: Shape, size, mineralogy,
           and elastic moduli
    • Abstract: Publication date: Available online 8 July 2017
      Source:Cement and Concrete Composites
      Author(s): S.T. Erdoğan, A.M. Forster, P.E. Stutzman, E.J. Garboczi
      The success of computational materials science models for cement and concrete, at the micrometer-to-millimeter scale, is based on careful characterization of the two main starting materials – cement and aggregates. Concrete is a complex material, and models based on over-simplified chemical, geometrical, and topological assumptions have limits on the behavior they can realistically simulate. In this paper, a sample of Ottawa sand was carefully characterized, since this material is used in laboratories all around North America as the specified sand for many standard tests, including what is possibly the most highly-used ASTM test of all in the field of cement-based materials, C-109, the mortar cube strength test. Particle shape and size distributions were acquired via a combination of X-ray tomography, spherical harmonic analysis, sieve analysis, microscopy and image analysis, and laser diffraction. Quantitative X-ray diffraction showed that the Ottawa sand used was very pure α−quartz with 1% amorphous content. Elastic moduli information at the particle level was obtained via instrumented nanoindentation. Polarized light microscopy showed that the particles that were indented were single crystals. Results for the Young's modulus, E, of Ottawa sand were E = 110 GPa ± 5 GPa (assumed Poisson's ratio of 0.08), in agreement with other nanoindentation results for Ottawa sand in the literature but more than one standard deviation larger than the results obtained from isotropic averages of the elastic moduli tensor of α−quartz, measured by ultrasonic and Brillouin scattering techniques and averaged in various ways. This kind of disagreement has been seen for other minerals as well as α−quartz, and indicates that nanoindentation measurement of elastic moduli for particulate minerals used in cement and concrete and other applications must be used with some care. This characterization procedure can now be confidently employed for any class of sand or gravel particle that is desired to be used in a three-dimensional mortar or concrete model.

      PubDate: 2017-07-09T09:06:00Z
       
  • Stress prediction in very early-age concrete subject to restraint under
           varying temperature histories
    • Abstract: Publication date: Available online 8 July 2017
      Source:Cement and Concrete Composites
      Author(s): Ya Wei, Siming Liang, Weiqiang Guo, Will Hansen
      Assessing the stress development in concrete requires an appropriate tensile creep model which is capable of incorporating the effect of the field environment conditions. This study quantifies the effect of temperature variation on the very early-age stress developments in restrained concrete by adopting a modified microprestress-solidification (MPS) theory-based creep model. The MPS creep model is first calibrated and verified based on the measured direct tensile creep data under normal and high temperature histories, it is then used to predict the very early-age stress development of the fully restrained concrete specimens under variable temperature history since casting. The predicted results are in good agreement with the experimental results. The tensile stress in restrained specimens can be relaxed by 80 %–87% within the first three days since casting. The predicted stress exhibits an obvious deviation from the measured one if temperature effect is not considered. Therefore, it is of importance to consider the temperature effect on concrete creep when the temperature variation in concrete is significant, and MPS creep model is valid for tensile stress prediction in concrete at very early ages.

      PubDate: 2017-07-09T09:06:00Z
       
  • Characterization of steel-concrete interface bonding conditions using
           attenuation characteristics of guided waves
    • Abstract: Publication date: Available online 8 July 2017
      Source:Cement and Concrete Composites
      Author(s): Homin Song, John S. Popovics
      This paper presents an air-coupled ultrasonic nondestructive evaluation approach based on the attenuation characteristics of guided waves to characterize interface bonding conditions of steel-clad concrete structures. Analytical guided wave modal solutions for various interface bonding conditions are obtained using the global matrix technique. The analytical results indicate that attenuation behavior of the fundamental symmetric (S0) guided wave mode is sensitive to interface bonding condition. A signal processing scheme is proposed to extract a dimensionless damage index, the normalized S0 mode magnitude, which reflects the attenuation behavior of the S0 mode. A series of numerical simulations are performed to verify the utility of the parameter to characterize interface bond condition. The feasibility of the testing approach is then established by experiments on steel-clad concrete specimens with different interface bonding conditions. The numerical simulation and experimental results demonstrate that interface bonding conditions of steel-clad concrete structures can be quantitatively evaluated using the proposed approach.

      PubDate: 2017-07-09T09:06:00Z
       
  • Relationship between fiber orientation/distribution and post-cracking
           flexural strength in ultra-high-performance fiber-reinforced concrete
           (UHPFRC)
    • Abstract: Publication date: Available online 8 July 2017
      Source:Cement and Concrete Composites
      Author(s): Bo Zhou, Yuichi Uchida
      The relationship between fiber orientation/distribution and post-cracking flexural strength in ultra-high-performance fiber-reinforced concrete (UHPFRC) was quantitatively evaluated. A circular UHPFRC panel was cast from its center and prismatic specimens were cut at angles of 0, 30, 60 and 90° between the specimen axis and the radial direction of the panel. The post-cracking behavior was assessed with three-point bending tests, and fiber orientation/distribution throughout the panel was then evaluated using image analysis and 3D visualization of fiber orientation based on X-ray computed tomography (CT) data. The post-cracking flexural strengths of the specimens cut at angles of 60, 30 and 0° were 80, 40 and 10% of that for the specimens cut at an angle of 90°, indicating perfect linear dependence on the contribution of fibers near the fracture surfaces. Two rectangular UHPFRC panels with a 1:2 width/length ratio were cast, and similar fiber orientation characteristics were found for the circular and rectangular panels.

      PubDate: 2017-07-09T09:06:00Z
       
  • Influence of nucleation seeding on the performance of carbonated MgO
           formulations
    • Abstract: Publication date: Available online 6 July 2017
      Source:Cement and Concrete Composites
      Author(s): N.T. Dung, C. Unluer
      The continuation of the hydration and carbonation reactions within reactive MgO cement formulations is inhibited by the formation of hydrate and carbonate phases around MgO particles, resulting in a low MgO utility and limited mechanical performance. This study introduces carbonate seeds into the pore space of MgO-based concrete mixes to enable the nucleation and growth of carbonates on the seed surfaces. The influence of seeds on the hydration and carbonation capability, mechanical performance and microstructural development was evaluated through isothermal calorimetry, water absorption and compressive strength measurements, along with TGA, XRD and SEM analyses. The introduction of ≤1% seed within the initial mix design increased the carbonate phase content and improved carbonation degree by up to 96% by increasing the availability of Mg(OH)2 for carbonation. The dense formation of carbonates in seeded samples enabled improved microstructures and 28-day strengths of 64 MPa, which were 33% higher than unseeded samples.

      PubDate: 2017-07-09T09:06:00Z
       
  • Influence of cement type on resistance to attack from two carboxylic acids
    • Abstract: Publication date: Available online 6 July 2017
      Source:Cement and Concrete Composites
      Author(s): Thomas Dyer
      In a number of circumstances, concrete may be required to possess resistance to organic acids. These are frequently carboxylic acids. This paper examines the effect of two such acids – acetic and butyric – on hardened cement paste specimens made from three cement types – Portland cement (PC), a combination of PC and fly ash (PC/FA), and a calcium sulfoaluminate cement (CSA). Specimens were exposed to solutions of the acids and deterioration characterized in terms of mass loss and pH measurements, micro-CT scanning, and chemical and mineralogical analysis. Additionally geochemical modelling was used to further examine the mechanisms involved during acid attack. The CSA cement was most resistant to attack, with the PC paste displaying the least resistance. This resistance has been partly attributed to the higher acid neutralization capacity of CSA cement. However, this paper demonstrates that the enhanced performance is most probably the result of a denser microstructure.

      PubDate: 2017-07-09T09:06:00Z
       
  • Effects of superfine zeolite on strength, flowability and cohesiveness of
           cementitious paste
    • Abstract: Publication date: Available online 5 July 2017
      Source:Cement and Concrete Composites
      Author(s): J.J. Chen, L.G. Li, P.L. Ng, A.K.H. Kwan
      Superfine zeolite (SFZ) is a natural zeolite ground to higher fineness than cement. Being a pozzolanic material, it can be used to replace part of the cement to reduce the cement consumption and carbon footprint of concrete production. In this study, in order to evaluate the effects of SFZ on strength and fresh properties, a total of 30 cementitious paste mixes with different SFZ contents and different W/CM ratios were produced for 7-day, 28-day, 70-day strength tests, and flowability and cohesiveness tests. And, to evaluate the effectiveness of SFZ as a superfine filler, the changes in packing density and water film thickness (WFT) due to the addition of SFZ were measured and determined. It was found that the addition of SFZ as cement replacement up to 20% slightly decreased the early strength, but slightly increased the long-term strength. Moreover, it increased the packing density and exerted its influence on the fresh properties of cementitious paste through the corresponding change in WFT. It also significantly increased the cohesiveness at the same flowability.

      PubDate: 2017-07-09T09:06:00Z
       
 
 
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