超低温冻融循环作用下的混凝土强度

混凝土结构已应用于低温、超低温环境领域，而当前对超低温下混凝土性能的研究很少，超低温冻融循环作用下混凝土强度的研究在国内几乎是空白。参照《普通混凝土长期性和耐久性试验方法》，考虑循环次数、循环时的最低温度、水胶比及外界环境湿度等参数的影响，进行了立方体混凝土抗压、抗拉强度试验及砂浆残样的SEM扫描电镜试验，探究超低温冻融循环作用对混凝土强度的影响及损伤的微观机理。强度试验结果表明，较常规冻融循环，超低温冻融循环对混凝土有更不利的影响，且随温度的降低，水胶比的提高，损伤有加大的趋势；相应地，SEM电镜试验下混凝土砂浆孔径增大，材料变得更疏松，从机理上解释了强度试验结果的合理性。

Experimental Research on Concrete Strength under Freeze-thaw Recycle Action with Ultra-low Temperature

The concrete structure has been used in low and ultra-low temperature environment. But few researches are experienced on its properties under freeze-thaw recycles with ultra-low temperature. Based on the standard for test methods of long-term performance and durability of ordinary concrete, considering the influence of the times and minimum temperature of recycles, water-cement ratio and the external environment humidity, compressive and tensile strength of cubic concrete and scanning electron microscopy on the residual sample are experimented to explore the impact of freezing and thawing cycles under ultra-low temperature on its strength and microstructure. The results show that the role of cryogenic temperature for freeze-thaw cycles has a greater effect on concrete performance. With the temperature decreasing and water-cement ratio increasing, the damage tends to grow up. Consistent with the results of the strength tests, electron microscopy tests show that the pore size of mortar increases and the material becomes looser.