火灾中混凝土力学及微观结构性能损伤规律

Damage law of mechanics and microstructure of concrete in fire

为了研究火灾发展过程中高温对大理石混凝土综合性能的损伤效应,先对含大理石废料的混凝土试件进行20~800℃温度范围的煅烧试验,冷却后再对试样进行矿物成分、质量损失、抗压强度和微观结构等性能指标的测试。结果表明:在火灾环境中,水泥凝胶体C-S-H因高温而发生崩解作用,大理石骨料的CaCO3在600℃以上分解;当环境温度低于200℃时,大理石混凝土的表面形貌、抗压强度及质量损失等宏观特征无明显变化;当温度大于400℃时,试件的宏观性能指标开始下降,且在600~800℃温度范围内迅速衰减;随温度上升,毛细吸水率逐渐增加,波速逐渐减小,材料的结构损伤效应与力学性能衰变规律具有同步性。

In order to study the influence of high temperatures in fires on the mechanical properties and structural damages of concretes, the temperature of 20~800 ℃ was brought to burn the marble concrete specimens. Then, the mineral composition test, mass loss test, compressive strength tests and microstructure detection tests were conducted to the cooled specimens. The test results show that the cement gel C-S-H is gradually decomposed under the effects of high temperatures and the calcium carbonate of the marble aggregate decompose in the temperature higher than 600 ℃.Under 200 ℃, the macro performance such as apparent morphology, compressive strength and the mass loss hasn’t significant changed. When the temperature is over 400 ℃, the macro performance decreases, and decays rapidly at 600~800 ℃. The capillary water absorption increase with the temperature, while the wave velocity decrease, which indicates that the microstructure defects and the mechanical properties have good synchronicity.