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Most concrete deterioration mechanisms are driven by the transport properties, in particular the chloride diffusion coefficient. As such, experimental and analytical tools have been developed to quantify the chloride diffusion coefficient. This study employs the experimental data reported in the literature to critically assess the accuracy and precision of the proposed analytical models for quantifying the concrete chloride diffusion coefficient. The models assessed range in scope from statistical models to hybrid models with the former employing statistical tools to fit the response function and the latter combining material science, physical science and mathematical tools to characterize the property. The test data include two standard test methods, i.e. bulk diffusion and migration test, and consider the following mixture design variables: water to cement ratio, cement type and content, supplementary cementing material, aggregate volume fraction, and air content. The results revealed that hybrid models are more accurate and precise in comparison to the statistical model. The "best" model is found to account for the capillary porosity, pore structure parameters, solid phase diffusivity, cement paste diffusivity, aggregate volume fraction, and interfacial transition zone properties yielding a ±95% confidence predictability of 0.86 and 0.97 of the quantified diffusion coefficients. Cement paste thickness which controls the ratios of the various diffusion coefficients is found missing in all the models. [ABSTRACT FROM AUTHOR]

Abstract: Dry-cast concrete blocks are a popular building material; however, to improve the economic and environmental sustainability of this industry, its dependence on natural aggregate and Portland cement needs to be reduced. To further this goal, blocks with up to 25% of the cement replaced with waste glass powder (WGP) or up to 15% of the sand replaced with high density polyethylene (HDPE) or low density polyethylene (LDPE) polymer pellets were produced in an industrial plant. The physical, mechanical and durability properties of the individual blocks and the mechanical properties of the block assemblages were tested. Based on statistical analyses, the blocks with 10% WGP as cement replacement performed similarly to the control blocks. The block properties were sensitive to the use of either type of polyethylene aggregate, which resulted in a decrease in strength and an increase in water absorption. Acceptable performance was achieved when 3–6% of the sand was substituted with polymer pellets. [Copyright &y& Elsevier]

Abstract: Concrete is the most widely used construction material and, for the most part, is produced using non-renewable natural resources and energy intensive processes which emit greenhouse gasses. There exists an opportunity to improve the sustainability of this industry by further exploring the use of alternative materials. As an aggregate, glass bottle waste has faced specific challenges including bond, ASR gel production, and strength degradation of the concrete. This paper reviews the literature pertaining to incorporating waste glass into concrete as a supplementary cementing material. Pozzolanic properties of waste glass as an SCM and ASR are related to particle size and percent addition. Lithium additives control ASR expansion; however, the mechanism of this control has yet to be defined. [Copyright &y& Elsevier]

Abstract: This paper presents a rational method to characterize the freeze–thaw salt scaling performance of concrete based on capillary suction forces. The testing program included evaluating the concrete’s chemical chloride binding capacity, degree of hydration, total porosity, compressive strength, sorptivity and de-icer salt scaling resistance conducted at both, 28 days and 2 years. Mixtures consisted of paste and concrete containing 0–60% GGBFS as cement replacement, and a water-to-binder ratio of 0.31 or 0.38. The proposed capillary suction model was adapted to include the concrete’s chloride binding capacity, pore characteristics, and age. Results from the capillary suction model are found to correlate with experimentally measured ionic sorption coefficients. Results revealed that the capillary suction depth decreases with increasing percentages of GGBFS due to blocking of capillary pores as a result of the chemical interaction between the saline solution and the binder material. A freeze–thaw salt scaling resistance factor (F/T SSRF) is proposed which accounts for the concrete’s degree of hydration, sorptivity and tensile strength and is shown to correlate with the concrete’s cumulative mass loss tested in accordance with MTO LS-412. Accordingly, the salt scaling performance of concrete containing GGBFS is influenced by the combined effect of the concrete’s pore size distribution of the exposed surface, chloride binding capacity, degree of hydration, and tensile strength. [Copyright &y& Elsevier]

Abstract: Rheological properties of fresh concrete, namely plastic viscosity and yield stress, are critical for the concrete industry because they affect placement and workability. Moreover, these rheological properties influence the productivity and quality of concrete, including mechanical properties and durability. Therefore proper characterization of these properties is needed to control the quality of fresh concrete and ensure sustainability of concrete structures. Fundamental and phenomenological rheological models have been proposed in the literature for characterizing the behaviour of fresh concrete. Establishing a model for predicting the plastic viscosity of concrete based on its composition will be extremely valuable for the concrete industry. This paper provides a critical review of the most prevailing models in concrete technology as well as models proposed in the literature for predicting the plastic viscosity of dense suspensions to a total of eight models. Review has revealed that Mahmoodzadeh and Chidiac models based on the cell method provides a higher degree of correlation to the experimental data as well as a more consistent and reliable predictions in comparison to the models currently proposed in the literature for concrete and/or dense suspensions. [Copyright &y& Elsevier]

Abstract: Compressive strength, ultrasonic pulse velocity (UPV), non-evaporable water content and the interplay between them were investigated at 1, 3, 7 and 28days to determine the effects of using ground granulated blast furnace slag (GGBFS) as cement replacement. The variables considered include percentage of GGBFS as cement replacement (0–60%), total binder content (270–450kg/m3), water-to-binder ratio (0.31, 0.38) and curing period. The dilution effect was observed at day 3, at which point, increasing the amount of GGBFS as cement replacement yielded lower compressive strengths. The results show that the evolution of mechanical properties is affected by the amount of water, percent of GGBFS added and curing regime. By 28days, the benefit of using GGBFS as cement replacement owing to its effect on the concrete’s packing density and hydration processes was reflected in the compressive strength and UPV measurements when used up to 50% cement replacement. Compressive strength of concrete containing GGBFS is found to increase on average by 10% from 28days to 120days. Measurements of non-evaporable water content and mass loss due to scaling revealed that the scaling resistance test for concrete at 28days is more favorable towards OPC concrete and discriminates against concrete containing high percentages of GGBFS as cement replacement. [Copyright &y& Elsevier]

Abstract: This study examines the laboratory de-icing salt scaling performance of concrete containing varying amounts of GGBFS as cement replacement. Using experimental results of concrete tested in accordance with ASTM C 672 and MTO LS-412 reported in the literature, a statistical analysis was carried out to evaluate the significance of several mix design variables, surface finishing, type of de-icing salt and duration of curing. Specifically, two multi-variable statistical models were developed to estimate the salt scaling resistance of the finished surface and the formed surface of concrete containing GGBFS as cement replacement. The models’ results show that (i) w/b ratio and ratio of OPC/binder are statistically significant, (ii) mass loss is not singularly dependant on the amount of OPC, GGBFS and total binder content, however their effect is captured by the ratio of OPC/binder, (iii) entraining air is not a controlling variable for the scaling resistance of the formed surface, (iv) type of de-icing salt affects the surface scaling, (v) both finishing procedure and curing regime are statistically significant for the finished surface, and (vi) resistance of concrete containing GGBFS to salt scaling improves with age. Results also revealed that the previously reported inconsistencies in the scaling resistance of concrete containing GGBFS are due to the differences in the performance of the finished and formed surface and to the uncovered fact that mass loss does not depend on the binder content as typically reported but rather on the ratio of OPC/binder. [Copyright &y& Elsevier]

The effects of chloride salts on concrete durability have been financially and logistically overwhelming. Current test methods for quantifying diffusivity of chlorides in concrete are time consuming and demanding. A comprehensive electrical resistivity model has been developed to quantify the chloride diffusion coefficient of concrete. The model employs the modified Nernst-Einstein equation along with an ionic concentration sub-model, a pore solution conductivity sub-model, and a binder hydration sub-model. The sub-models, which account for the concentrations of Na+, K+, Ca2+, and OH− ions in the pore solution derived from the binder degree of hydration, binder chemical composition, and alkalis binding to the cement hydration products, are included to accurately quantify the conductivity of the pore solution. Moreover, an experimental program was developed to verify and validate the accuracy and completeness of the electrical resistivity model. The experimental variables are volume fraction of coarse aggregate, water to binder ratio, total binder content, and silica fume (SF) and ground granulated blast furnace slag (GGBFS) as supplementary cementing materials (SCMs). The model results are found statistically equal to experimentally quantified chloride diffusion coefficient values and possess high accuracy and precision for a wide range of concrete mixture, binder composition and age. [ABSTRACT FROM AUTHOR]