Hydration mechanisms of hybrid cements as a function of the way of addition of chemicals

In this study fly ash contents of up to 50% were used to produce binders with mechanical strength greater than or equal to type CEM I 42.5R cement (reference). The specific aim pursued in this research was to determine whether the procedure used to add the chemical activator (in solid or liquid form) can affect strength development in the cement or the nature of the reaction products formed. Two experimental procedures were deployed: (a) the chemical activator was dissolved in the mixing water; (b) the chemical activator was ground, as a solid, into the fly ash. The solid-state method induced slightly higher mechanical strength than when the activator was dissolved in hydration water. The way the chemical activator was added affected not only early age reaction kinetics, but also the nature and composition of the reaction products, the liquid state favoring the formation of phases AFt and AFm.