Reaction kinetics of supplementary cementitious materials in reactivity tests

This work characterizes the reaction kinetics of supplementary cementitious materials (SCMs) with calcium hydroxide in the modified R³ test. The heat flow curves of 58 SCMs of varying reactivities were studied. Based on the heat flow curves, the SCMs were classified as more reactive, less reactive, and inert. Most of the heat flow curves in the modified R³ test exhibit, after the peak of heat flow, an initial slow decaying power-law regime that transitions into a longer and faster decaying power-law regime. The pre-exponent of the first regime depends on the initial SCM reactivity and correlates well with the 24-hour heat release in the modified R³ test, thus making it a useful metric for rapid classification of SCMs.