Influence of supplementary cementitious material and filler fineness on their reactivity in model systems and cementitious pastes

The influence of supplementary cementitious materials (SCMs) and filler fineness on their reactivity in model systems and in cementitious pastes was evaluated. Two SCMs-pumice (P), and glass powder (GP), and an inert filler-limestone (LS), with three different levels of fineness and median particle size (d(50)) values were tested using the modified R-3 test to obtain direct measures of their reactivity. The reactivity of P and GP, indicated by the heat release and calcium hydroxide consumption, increased linearly as the d(50) decreased (and fineness increased). However, for LS, the change in fineness did not influence the reactivity. These materials were used at a 30% replacement level by mass in cementitious pastes at a water-to-cementitious materials ratio of 0.40 and heat release, calcium hydroxide content, compressive strength, and bulk resistivity were monitored. The increasing fineness impacted property development in very similar ways for the P and the GP but not for the LS. For the SCMs, early- and later-age properties generally, but not always, had a linear correlation with median particle size. Bulk resistivity was a notable exception, with early-age values not depending on median particle size and later-age values showing a non-linear relationship with median particle size. For coarser materials, the impacts were largely driven by dilution and filler effect, but for finer materials, the impact of reactivity on property development was evident. The effects of SCM reactivity were more evident at later ages. The heat release and calcium hydroxide consumption measured in the modified R-3 test were correlated to the 56-day calcium hydroxide content, compressive strength, and bulk resistivity in cementitious pastes.