Effect of Inorganic Salts on Pore Structure of Cement Paste

Inorganic salts are important admixtures usually used in cold weather concrete. As research basic of influence of salts on concrete durability, effects of inorganic salts on pore structure of cement paste were studied in this paper, and possible implications of concrete property with pore structure was also analyzed. Pore structure of paste added CaCl2, NaCl, Na2SO4, NaNO2, Ca(NO3)2 and Ca(NO2)2 curing for 3 days and 28 days were tested through mercury intrusion porosimetry (MIP). The results showed that no matter 0.3 or 0.5 water-cement ratio, the pores whose diameter <50nm in paste with salts increased at 3 days, which was harmful for the control of concrete shrinkage and cracking at early age. Adding Ca (NO3)2 increased coarse pores (>200nm) of paste at 3 days, but these coarse pores turned into fine pores and reduced significantly at 28 days. Adding NaCl and Na2SO4 into cement paste raised coarse pores with size>1000nm at 3 days and 28days, which were harmful for the pore structure.