Studies about a sulphate resistant cement. Influence of admixtures

Abstract

Starting from an industrial cement obtained by milling together a new low energy clinker and gypsum, two blended cements containing 20% wt of fly ashes and 10% wt of limestone respectively, have been prepared. The behaviour of these three cements in Na 2SO 4 dissolution and sea water has been studied. The method used for testing the specimens has been the Koch-Steinneger one. As a consequence of the study it can be said that the three cements keep a good behaviour in all the aggressive media although the strengths are lower (independently of the age of the specimens) in Na 2SO 4 and sea water than in distilled water. Also, the composition of the hydrated pastes conserved in the aggressive liquids of different periods of time has been studied. The evolution of the content of Ca(OH) 2, gypsum and Mg(OH) 2 in the pastes as well as the variations observed in the morphology of C-S-H gel along the time and in function of the aggressive medium, seem to keep a good correlation with the strengths evolution. Finally it has been concluded that those cements prepared with the new low energy cement have such a composition that makes them to be resistant to the sulphate attack.