Porosity and its Relationship to the Strength of Hydraulic Cement Pastes

Abstract

AbstractThe concept of ‘intrinsic strength’ of cement was addressed by testing the bending strength propertes of MDF cement pastes[1–5], containing no organic material, over a range of pore volumes and flaw lengths. The MDF pastes, made only of cement and water, exhibited interesting behaviour, particularly the well packed compositions which gave remarkably low porosity, about 1%, and high modulus, 75 GPa. It was demonstrated that the bending strength of these materials depended on flaw size in a brittle fashion, and that the toughness increased as the volume porosity fell. Fracture mechanics described the results satisfactorily. Therefore, theories based on intrinsic strength, or on the need for polymers to provide high strength [7, 10] are unnecessary.