Influence of high temperature on strength, ultrasonic velocity and mass loss of calcium carbonate whisker reinforced cement paste

Calcium carbonate whisker (CW) can reinforce the flexural strength of cement paste and limit the development of micro-cracks at ambient temperature (25 +/- 2 degrees C), but the effect of CW on mechanical properties of cement paste after exposure to high temperatures is still unknown. Therefore, mechanical properties, i.e. flexural strength, compressive strength and splitting tensile strength were measured using CW reinforced cement specimens before and after they were exposed to high temperatures. In addition, performance of CW reinforced cement paste after exposure to high temperatures was studied by ultrasonic test and mass loss test. At last, microstructural analysis (differential thermogravimetric analysis and scanning electron microscopy) were employed to study the deterioration mechanism of temperature and reinforcement mechanism of CW. These experimental results suggested that CW played a significant role in hindering the development of cracks before 600 degrees C. When temperatures increased up to 200 degrees C, the flexural strength decreased. However, the compressive strength and splitting tensile increased. When temperatures varied from 200 degrees C to 400 degrees C, the three strengths reacted differently to the elevated temperatures. Subsequently, the residual strength rapidly decreased up to 1000 degrees C. After that, the three strengths increased slightly. The residual strength, ultrasonic velocity and mass loss were related to the temperatures and CW content and quantitative measurement of these factors was also discussed.