A methodology for assessing the chemical and physical potential of industrially sourced rice husk ash on strength development and early-age hydration of cement paste

Abstract

Among supplementary cementitious materials (SCMs), rice husk ash (RHA) is a by-product of the agriculturalindustry that is recognized by its high reactivity and ability to enhance performance of cementbasedmaterials. The dependence of RHA reactivity on burning conditions and grinding procedures makesit sensitive to uncontrolled combustion/production. This study assesses 5 RHAs from industrial sources tounderstand how uncontrolled combustion impacts the reactivity of RHA. A fundamental model is proposedthat combines physical (specific surface area) and chemical (amorphous silica content) characteristicsof RHA with hydration and strength gain, considering the relative contribution of each one overtime. Isothermal calorimetry was used to continuously assess strength development at early ages. Theresults show that the model is well correlated with strength development at different ages and allowsthe computation of an equivalent water-to-cement ratio considering solely the characteristics of a RHAsample, and prior to producing and testing specimens.