Critical observations for the evaluation of cement hydration models

Abstract

The development of computer models for cement hydration and microstructure development, with an explicit consideration of microstructure, has accelerated in the past 25 years, creating a need for a set of critical experimental observations that can be used in evaluating the model predictions. During this same time period, there have been rapid advances in experimental techniques for quantifying both the hydration rates and the produced microstructures. This paper utilizes several of these techniques to elaborate a preliminary set of experimental observations concerning the influence of water-to-cement ratio, cement particle size distribution, and curing conditions on hydration and microstructure development. Isothermal calorimetry provides a convenient measure of the ongoing hydration rates during the first 7 days of hydration, while low temperature calorimetry can be used to directly assess the percolation state of the capillary porosity and the quantity of freezable water in a hydrated cement paste. Conventional measurements of setting times, such as Vicat needle penetration, are related to the ongoing percolation transitions of the solids within the three-dimensional microstructure. Finally, since concretes in the field rarely experience saturated curing conditions, the influence of sealed curing on resultant degree of hydration and microstructure is examined. The presented data sets should provide a first step in performing a critical evaluation of existing and future computer models.