早期受冻温度对负温混凝土微观结构与强度的影响

为降低负温给混凝土结构带来的内部损伤,采用压汞法测孔、扫描电镜微观形貌观察等实验手段,研究在不同温度早期受冻混凝土的孔径分布和微观结构及其抗压强度随龄期发展变化情况,探讨不同冻结温度下负温混凝土微观结构与宏观力学性能的关系。结果表明:早期养护温度越低,水泥石初始结构越疏松,<20 nm的凝胶孔含量明显降低,混凝土抗压强度较低;转入标准养护后,负温混凝土孔径趋于细化,抗压强度得以迅速增长,-5℃受冻的混凝土,转标准养护28 d后>200 nm孔含量几乎与标准养护28 d混凝土相当,抗压强度亦接近。但-10℃和-15℃受冻的两组混凝土中大孔含量仍略高于标准养护混凝土,抗压强度相对略低。

Effect of freezing temperature on microstructure and compressive strength of negative temperature concrete

Aimed at reducing effect of the negative temperature on internal damage to the concrete structure, the pore size distribution and the microstrueture of negative temperature concrete was studied with different temperature, combining with some testing methods, such as MIP and SEM. Moreover, the change of the compressive strength was also studied with different ages. In addition, the relationship between the microstructure and the macro-mechanical properties on negative temperature concrete was explored further with different freezing temperature. It indicated that the lower the early curing temperature, the looser the original structure of cement paste ; the total volume of gel pore whose pore size was less than 20 nm was decreasing apparently, and the compressive strength declined. When changing to standard curing, the pore size trended to be thinner, the compressive strength was increasing sharply. The concrete was cured from - 5 ℃ to standard curing, the volume of pore that was less than 200 nm was equal to that of the concrete with the standard curing in the age of 28 d, so was the compressive strength. However, the volume of the macro pore of the concrete curing under - 10 ℃ and - 15 ℃ was greater than the con- crete curing the standard condition, the compressive strength was less.