STUDIES ABOUT A SULFATE RESISTANT CEMENT - INFLUENCE OF ADMIXTURES

Starting from an industrial cement obtained by milling together a new low energy clinker and gypsum, two blended cements containing 20% wt o f fly ashes and 10% wt of limestone respectively, have been prepared. The behaviour of these three cements in Na2SO4 dissolution and sea wat er has been studied. The method used for testing the specimens has bee n the Koch-Steinneger one. As a consequence of the study it can be sai d that the three cements keep a good behaviour in all the aggressive m edia although the strengths are lower (independently of the age of the specimens) in Na2SO4 and sea water than in distilled water. Also, the composition of the hydrated pastes conserved in the aggressive liquid s for 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 v ariations observed in the morphology of C-S-H gel along the time and i n function of the aggressive medium, seem to keep a good correlation w ith the strengths evolution. Finally it has been concluded that those cements prepared with the new low energy cement have such a compositio n that makes them to be resistant to the sulphate attack.