冻融作用下硬化水泥浆体和混凝土结构的变化

用压汞法和扫描电子显微镜研究了冻融循环作用下硬化水泥浆体和混凝土宏观与细观结构的变化.结果表明,冻融以后硬化水泥浆体和混凝土中砂浆的孔隙率,特别是大于50 nm的毛细孔体积和微裂纹增大较多,导致硬化水泥浆体由密实体向松散体发展,最后导致粗骨料与砂浆分离.提出了快速冻融破坏机理与自然条件下缓慢冻融的破坏机理存在差异的观点.

Effect of Freeze-thaw on the Structure of Hardened Cement Paste and Concrete

The effect of freeze-thaw on the structure of hardened cement paste and concrete is studied by mercury intrusion porosimetry and scanning electron microscopy. The results show that the porosities and microcracks, especially those larger than 50nm, of the hardened cement paste and mortar specimens are increased after freeze-thaw test, which makes the hardened cement paste change from a compacted body to a loose one, and finally results in the break of the concrete. It is believed that the damage mechanism of concrete under rapid freeze-thaw test is thus a little different from that under natural freezing. In addition to the hydrostatic and osmotic pressures, the specimens under rapid freezing are subjected to the stress resulted from the temperature change, so that concrete is more likely to be broken under rapid freeze-thaw than under natural freezing.