CHEMICAL ATTACK ON HARDENED PASTES OF BLENDED CEMENTS .2. ATTACK OF SEA-WATER

The presence of chloride and sulphate ions in sea water together with magnesium and sodium ions leads to aggressive behaviour on hardened cement pastes because some constituents of the cement paste can enter into deleterious chemical reactions with chlorides and sulphates. The resistance to aggressive attack can be improved when the tricalcium aluminate in the cement is reduced or by substituting a portion of portland cement with a suitable pozzolanic material, i.e. reduce the C3A in the blended cement and also the liberated Ca(OH)2 during the hydration of the hardened cement paste. The aim of the present work is to study the attack of sea water on hardened blended cement pastes up to one year. The results revealed that the blended cement made with 15\% granulated slag can be used in sea water. On the other side, cement kiln dust is unsuitable for making blended cement as sea water resisting cement.