PLASTIC CRACKING OF CONCRETE - THE ROLES OF OSMOTIC AND MATRIC SUCTION

摘要

Plastic cracking of concrete is primarily attributable to desiccation by evaporation from unprotected surfaces. This causes high matric suctions to develop in the pore water in the voids adjacent to these surfaces. Dissolved salts in the pore water generate osmotic suctions. However, the effects of these suctions on the strength of plastic concrete are imperfectly understood. In this paper, equations describing total (matric plus osmotic) and osmotic suctions and the shear strength of desiccated particulate materials are discussed briefly. The development of suctions in desiccating fly ash and their effect on its shear strength are illustrated by experimental data. These show that matric suctions do but osmotic suctions do not affect the shear strength of fly ash and hence of comparable materials, including plastic concrete.