Modified cement-based mortars: crack initiation and volume changes

The aim of this paper was to quantify the crack initiation and volume changes of three types of fine-grain cement-based composites: the reference one including Portland cement only and the other two with the mass fraction 20 % of Portland cement replaced by granulated blast-furnace slag or pulverized-coal fly ash. Half of the specimens from each mixture were cured according to ASTM C1260-94 and ASTM C1567-07, other specimens were cured in water. The length changes were measured during the curing (a test for the risk of the alkali-silica reactivity). Furthermore, a three-point-bending test was performed on these specimens to obtain the fracture parameters, which were determined using a double-K fracture model. It was found that the type of specimen curing has a significant effect on the volume changes and a moderate influence on the elasticity modulus, the crack initiation and fracture-toughness values. Keywords: cement-based