Experimental Study On The Microstructure Deterioration And Damage Process Of Cement-based Materials Exposed To High Temperatures

Microstructure and damage process of cement-based materials exposed to high temperatures are investigated with test measurement and theoretical analysis. Based on the evolution of microstructure on the surface of cement-based materials and the degradation of mechanical properties under the continuous temperature rising, the microstructure deterioration of cement-based materials is derived. And a detailed research is carried out about the deterioration of cement-based materials under high temperatures from the three aspects of the micro-morphology, pore structure and pore fractal characteristics. The deterioration mechanisms of cement-based materials and the mechanism of fly ash resistance to high temperatures are revealed. The performance resisting high temperatures of different ratio materials are discussing. Studies have shown that deterioration of microstructure on the surface of the cement-based materials starts at 50℃around, and 100℃is the starting temperature of mortar increased deterioration, and the threshold temperature of deterioration of microstructure of cement paste is 300℃. Effects of high temperatures on the deterioration of microstructure of mortar were more serious than that of cement paste. A series of physical and chemical changes which happened because of high temperatures in the cement-based materials leads to the deterioration of microstructure. And C-S-H gel is the key factor of the deterioration. The effective temperature range of fly ash resistance to high temperatures is 100-400℃, which works best at 300℃.