Abstract: To study the effect of temperature on the compressive strength of sulphoaluminate cement mortar as a repair material for shallow decay concrete in large temperature difference of northwest China, three different mix proportions, three temperature gradients (-25, 25 and 80 ℃) and three time lengths (6, 12 and 24 h) before and after modification were designed. Compressive strength of samples were tested, and micro properties were tested by scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. The results show that the failure modes of modified samples are better than that of original sample. With the elongation of time, the growth rates of compressive strength of modified samples at -25 ℃ are greater than that of original sample. At 25 ℃, the compressive strength of three groups samples are similar and have slight reductions. At 80 ℃, the compressive strength of modified sample with 0.3% (mass fraction) water glass, 0.1% (mass fraction) PP fiber and 0.4% (mass fraction) expander has the least reduction rate. Meanwhile, the prediction formulas of relative variation rate of compressive strength for this sample with time at different temperatures are established, which can provide some references for sulphoaluminate cement mortar as a repairing material for shallow decay concrete in large temperature difference of northwest China.

Key words: sulphoaluminate cement, water glass, PP fiber, UEA expander, large temperature difference of northwest China, temperature, compressive strength