Effect of freezing on the dynamic mechanical response of hardened cement paste down to −60°C

Abstract

The dynamic mechanical response (the internal friction, tanδ, and the E-modulus) in the temperature range from −60°C to 0°C reveals a sharp modulus change and a shallow tanδ peak. This “capillary transition” occurs only in specimens suspected of having capillary water; its strength is both a function of moisture content and the pore structure. The E-T curve in the transition region for a number of saturated specimens is fitted by an empirical equation; the parameters of this equation are correlated with the capillary porosity, defined in the conventional manner. One of these parameters is interpreted in terms of a maximum pore size. A theory is outlined for interpreting the E-T curve in terms of thermodynamic, composite mechanics, and pore structure parameters. The discovery of the “capillary transition” has made available a new technique for investigating the various, rather complicated aspects of the process of freezing within a porous solid.