AGGRESSIVE ATTACK OF SULFATE BEARING WATERS ON BLENDED CEMENT PASTES

Aggressive attack of sulphate ions is one of the factors responsible for damage to portland cement concrete. Sulphate ions can react with some constituents of cement paste producing sulphoaluminate hydrates and gypsum which cause expansion and cracking of concrete. The production of blended cements has been of considerable interest because such cements increase the chemical resistance to sulphate attack. We found that cement dust could not be used as an ingredient for producing some blended cements. The substitution of portland cement clinker as well as granulated slag with cement dust decreases the properties of cement pastes in sulphate solution. Also, (NH4)2SO4 is more aggressive than MgSO4 on the hardened cement paste.