Simple chemical clock reactions: application to cement hydration

Abstract

In the first part of this paper, we review some recent mathematical work which shows how the duration of induction periods for simple non-linear chemical kinetic models can be related directly to initial reactant concentrations and reaction rate constants in these schemes. These results should be of interest to both theorists and experimentalists.

Chemical clock behaviour has obvious parallels with the induction period observed during the hydration and setting of cements: a slurry remains liquid for a characteristic time before rapidly hardening into a porous solid. Cement chemistry is not completely understood, but our approach concentrates on what we believe to be the dominant kinetic steps which control the overall setting process. Specifically, the rate-determining process is taken to be an inhibited autocatalytic nucleation mechanism for which we propose a connection with one of our model clock reaction schemes. The model is in at least qualitative agreement with experimental observations.