Chemical strength of HPC cured in a sulphate environment

Abstract

A large variety of sulphates, generally coming from underground water or sea waters, can come into contact with the concrete and react chemically with the hydrates, in particular with aluminates, and cause the cracking and the failure of the concrete. The durability of the concretes in a sulphate environment is normally ensured by a sufficient content of cement and the dense structure of the hydrated paste. The combination of natural pozzolans with portland cement makes possible the development of concretes having mechanical properties and a durability much higher than that of a concrete without addition. In order to better determine the pozzolanic effect of the pozzolan addition in the concrete, the evolution of the crystalline phases have been analyzed using x-ray diffraction analysis examined using scanning electron microscopic techniques including the use of chemical analysis to confirm their chemical composition. In parallel with these tests, the evolution of the mechanical bending and compressive strengths have been observed using an automatic test machine. The present study confirms the pozzolanic reactivity of the natural pozzolans used