THEORY OF SHRINKAGE OF HARDENED CEMENT PASTE

Abstract

Based on the disjoining pressure concept, volume change of several kinds of hardened cement paste (hcp) is investigated. As the hcp shows a hysteresis regarding adsorption and desorption isotherm, disjoining pressure of water in hcp is evaluated with the proposed equation led from equilibrium between disjoining pressure of water and elastic force of skeleton. In addition, the averaged thickness of adsorbed water is evaluated through water content and specific surface area which was measured by vapor absorption isotherm and B.E.T. theory. As a result, all the relationships of hcp between averaged thickness of adsorbed water and disjoining pressure of water were on the same curve.
The proposed theory for hcp can also explain the volume change after hysteresis, shrinkage without decreasing the equilibrium relative humidity, and the larger shrinkage of concrete containing aggregate with the larger specific surface.