Abstract: High temperature resistance performance of portland cement in 20 ℃, 200 ℃, 400 ℃, 600 ℃, 800 ℃ and 1000 ℃ was studied by the appearance change, mass loss and compressive strength in different high temperature.And the mechanism of stability change in different temperature of portland cement was studied by the scanning electron microscope (SEM), X-ray diffraction analysis (XRD) and differential thermal analysis (DTA).The results indicate that the Portland cement still keep the unbroken appearance and compressive strength under 400 ℃.Conversely, it is a sharp drop in stability,and there are abound of alveolate viods within cement.Then C-S-H del is decomposed and compressive strength is loss when the temperature exceed 600 ℃ that there are abound of alveolate voids within cement result in the destruction of C-S-H gel and loss of compress strength.

Key words: portland cement;high temperature resistance;microanalysis