TEMPERATURE EFFECT ON THE PORE SOLUTION CHEMISTRY IN CONTAMINATED CEMENTS

The combined effect of chloride and sulphate contamination and tempera ture on the pore solution chemistry, particularly the OH-, Cl- and SO4 2- concentration, in plain and blended cements was evaluated. The ceme nt mortar specimens were contaminated with sodium chloride and sodium chloride plus sodium sulphate and exposed to temperatures in the range 25 to 70 degrees C. Results indicate that the chloride binding capaci ty of cement is affected by both the temperature and the sulphate cont amination. In the chloride contaminated specimens, the chloride bindin g was influenced by the exposure temperature, while in those contamina ted 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 c hloride contamination. The Cl-/OH- values increased with temperature i n both plain and blended cements, indicating the vulnerability to acce lerated steel depassivation in concrete exposed to elevated temperatur e and contaminated with chloride and sulphate ions.