Temperature effect on the pore solution chemistry in contaminated cements

The combined effect of chloride and sulphate contamination and temperature on the pore solution chemistry, particularly the OH^- , Cl^- and SO₄^2- concentration, in plain and blended cements was evaluated. The cement mortar specimens were contaminated with sodium chloride and sodium chloride plus sodium sulphate and exposed to temperatures in the range 25 to 70°C. Results indicate that the chloride binding capacity of cement is affected by both the temperature and the sulphate contamination. In the chloride contaminated specimens, the chloride binding was influenced by the exposure temperature, while in those contaminated with sodium chloride plus sodium sulphate, it was affected by the presence of sulphate ions. The sulphate concentration in the plain and blended cements was also influenced by the exposure temperature and chloride contamination. The Cl^- / OH^- values increased with temperature in both plain and blended cements, indicating the vulnerability to accelerated steel depassivation in concrete exposed to elevated temperature and contaminated with chloride and sulphate ions.