Effect of sea water on calcium effective diffusion of ternary cement

The influence of sea-water aggressive environments (sodium chloride, sodium sulfate and a mixture of both) on calcium effective diffusion of ternary Portland cement pastes (TPC) containing thermally activated paper sludge and fly ash has been evaluated from the leaching of calcium during a 90-day period. The degradation of the material over time is estimated from the calcium effective diffusivity. The results showed lower effective diffusion coefficients of calcium in the case of the TPC pastes. This behaviour is related to its microstructure, which is denser than that of ordinary Portland cement (OPC). In the case of sodium chloride, the higher decalcification values were obtained for the two TPC and OPC pastes. Nevertheless, the presence of sodium sulfate induced a strong decrease of decalcification, producing a synergy in the case of the mixture of sodium chloride and sodium sulfate salts.