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A laboratory study was done on the influence of vitreous calcium aluminosilicate (VCAS), a new pozzolanic mineral admixture, on the properties of fresh and hardened portland cement concrete. A relative comparison was done of the performance of concrete containing VCAS with that of concrete containing silica fume (SF), one of the widely used mineral admixtures. The addition of VCAS pozzolan increased the slump (improved consistency) of the mixtures, while the addition of SF decreased it. The VCAS pozzolan was found not to have significant influence on the plastic shrinkage cracking potential of the mixtures while SF increased it. The compressive strength development of both the VCAS and SF mixtures was found to be higher than that of the control mixture. The experimental results showed that both VCAS and SF increased the free shrinkage of concrete. The rapid chloride permeability (RCP) values for mixtures with VCAS and SF specimens were significantly lower than those of the control concrete. At equal replacements of cement with either VCAS or SF, the reduction in RCP values was higher for the SF modified mixtures. Incorporation of either VCAS or SF also reduced the sorptivity and moisture diffusion coefficient of the concrete mixtures. This study provides insight into the behavior of concretes containing two high-performance mineral admixtures.

Electrical response of cementitious systems can be used to understand the evolving microstructure, and thus to provide indications of the mechanical and durability performance of such systems. This paper deals with the use of a generalized effective medium (GEM) theory to predict the porosity of cement pastes and concretes containing several cement replacement materials. Methodologies to obtain the pore solution conductivities and an equivalent soild phase conductivity in the case of concretes are outlined. The predicted porosities are found to match well with the experimental values obtained from a vacuum saturation method. It is shown in this paper that the critical exponent in the GEM equation influences the predicted porosities and a universal value for this exponent cannot be used in continuum percolating systems such as cement pastes and concretes. The thermal signature of hydrating cementitious systems, represented using the equivalent age maturity index, is related to a microstructural parameter obtained from electrical impedance. A unique relationship is observed between the equivalent age and the microstructural parameter irrespective of the mixture design parameters thereby providing a crucial link between maturity and microstructure development.