Influence of microstucture on the physical properties of concentrate prepared by substituting mineral powder for part of fine aggregate

Abstract

The hydration reaction of cement, hardened structure and pore structure in concrete prepared by substituting a large quantity of mineral powder including fly ash, slag, limestone and silicious stone for part of fine aggregate in concrete have been studied and the relationships between the substitution of those mineral powders and the physical properties of concrete have been investigated. Increase in viscosity and decrease in fluidity of concrete by the substitution of the mineral powder for part of fine aggregate are mainly caused by the increase of fine particles non-existent in fine aggregate. Higher strength than that of concrete without substitution in the case with the same slump is brought by the densification of hardened concrete structure by filling effect of mineral powder itself and, in some cases, of C-S-H produced by pozzolanic reaction. The slight increase of creep of the concrete prepared by substituting fly ash for part of fine aggregate may be caused by offsetting the increase of the practical quantity of cement paste in concrete by the improvement of strength of the hardened concrete. The reduction of dynamic Young's modulus may be caused by the increase of practical quantity of cement paste with the dynamic Young's modulus almost half that of aggregate.