Question

Explain the reason why is sulphate-resisting cement not used in marine concrete?

Answer

Major components of Portland cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. In sulphate-resisting cement, it contains a low quantity of tricalcium aluminate in order to keep away from sulphate attack.Or else, tricalcium aluminate would react with sulphates to form calcium sulphoaluminate and gypsum that source expansion and crack concrete structure.

Still, for marine concrete sulphate-resisting cement must not be used since tricalcium aluminate has high affinity for chloride ions. This is base on possible reaction of chloride ions and tricalcium aluminate to form calcium chloroaluminate hydrate and reduction of that may increase rate of chloride attack to the concrete marine structure and result in earlier corrosion of steel reinforcement in marine arrangements.