Modeling the linear elastic properties of Portland cement paste

Abstract

The linear elastic moduli of cement paste are key parameters, along with the cement paste compressive and tensile strengths, for characterizing the mechanical response of mortar and concrete. Predicting these moduli is difficult, as these materials are random, complex, multi-scale composites. This paper describes how finite element procedures combined with knowledge of individual phase moduli are used, in combination with a cement paste microstructure development model, to quantitatively predict elastic moduli as a function of degree of hydration, as measured by loss on ignition. Comparison between model predictions and experimental results are good for degrees of hydration of 50% or greater, for a range of water : cement ratios. At early ages, the resolution of the typical 100 3 digital microstructure is inadequate to give accurate results for the tenuous cement paste microstructure that exists at low degrees of hydration. Elastic computations were made on higher resolution microstructures, up to 400 3, and compared to early age elastic moduli data. Increasing agreement with experiment was seen as the resolution increased, even when ignoring possible viscoelastic effects.