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This study examines the influence of fine aggregates on early-age mortar pore solution chemistry and electrical resistivity. Specifically, this paper considers the potential adsorption of Na+ and K+ on the aggregate. Ten aggregates from various locations in the United States were used in this study. It was shown that fine aggregates can adsorb Na+ and K+ ions, which can change the ionic concentration of the pore solution and increase the pore solution resistivity. The resistivity is also influenced by the absorbed water in the aggregate, which dilutes the pore solution. A test methodology was proposed to characterize the aggregate adsorption of Na+ and K+ from the pore solution. The alkali adsorption was quantified by developing adsorption isotherms for each aggregate. Using the adsorption isotherms, the concentrations of Na+ and K+ adsorbed on aggregates in mortars were estimated. [ABSTRACT FROM AUTHOR]

This paper describes an approach to predict the mechanical and fracture behavior of cement-based systems by combining thermodynamic and finite element analysis models. First, the reaction products in a hydrated cementitious paste are predicted using a thermodynamic model. Second, a pore partitioning model is used to segment the total porosity into porosity associated with gel pores and capillary pores. A property-porosity relationship is used to predict the elastic modulus, tensile strength, and fracture energy of the hardened cement paste. The paste’s modulus, fracture energy, and tensile strength, along with information on the aggregate properties and interfacial transition zone properties, are used as inputs to a finite element analysis model to predict the flexural strength and fracture response of mortars. [ABSTRACT FROM AUTHOR]

The article presents the discussion on new mixture proportioning method being developed for performance based concrete with supplementary cementitious materials (SCMs). Topics include conventional mixture design process estimating the paste content of concrete needed for a mixture with a given slump based on maximum aggregate size, air content, and water-cement ratio (w/c); and predicting several key performance parameters of concrete such as the calcium hydroxide (CH) content and porosity.