Abstract: In view of the actual situation in northwest China, we examined the sulfate corrosion resistance of cement mortar under the combined action of low temperature and dry wet cycles. We determined 0.50 and 0.36 as the water cement ratio of test cement mortar specimens; at each water cement ratio, we prepared four groups of mortar specimens with different binding materials: ordinary Portland cement, medium anti sulfate Portland cement, ordinary Portland cement dosed with 15% slag and 1% silica fume, and ordinary Portland cement dosed with 15% slag and 3% silica fume. The results are concluded as follows: under the combined action of low temperature and dry wet cycles, the degradation of cement mortar is mainly induced by the crystallization of sodium sulfate, with very slow chemical corrosion. Cutting the water cement ratio could remarkably improve the performance of cement mortar against sulfate attack. Anti sulfate Portland cement could enhance the corrosion resistance to a certain extent. Moreover, adding slag and silica fume would ameliorate the corrosion resistance of mortar with low water cement ratio, and vise versa. The results offer reference for constructions in the regions under combined action of low temperature and dry wet cycles.

Key words: cement mortar, low temperature, drywet cycle, sulfate attack, watercement ratio