火灾高温对大理石混凝土宏观性能与微观结构的影响

Effect of Fire High Temperature on Macroscopic Properties and Microstructure of Concrete Containing Marble

为了研究火灾发展过程中高温对混凝土的力学性能和结构损伤的影响,在20~800℃温度范围内开展含大理石废料混凝土的高温燃烧试验,再对自然冷却后的试件进行XRD分析、质量损失测量、单轴压缩以及微观结构探测等试验。结果表明:在火灾发展过程中,混凝土内的水泥凝胶体C-S-H受高温作用逐渐分解,火灾后期大理石骨料的碳酸钙发生化学反应;含大理石废料的混凝土试样的表观形态、单轴抗压强度和质量损失等宏观性能在200℃以下温度环境中没有出现明显变化,燃烧温度超过400℃后混凝土试件的宏观性能开始衰减,在600~800℃的温度范围内的劣化程度大幅增加;采用毛细吸水率和超声波波速表征混凝土的微观结构特性,结果表明微观结构特征与宏观力学性能变化规律保持较好的同步性。

High temperature in order to study the fire on the mechanical properties of concrete and the influence of structural damage in 20-800 ℃ temperature range including marble waste concrete continuous high temperature combustion processes of the specimens, and then took the cooled specimen for XRD experiment, compressive strength and microstructure detection test. The test results show that the cement gel C-S-H is gradually decomposed under the action of high temperature and the calcium carbonate of the marble aggregate in the later stage of fire reacts. Marble waste concrete specimens in apparent morphology,the uniaxial compressive strength and the quality loss such as macro performance under200 ℃ temperature without a significant change in the environment,the environment temperature over 400 ℃ after the structural damage of concrete specimen started to develop,in 600-800 ℃ temperature range of the macro performance degradation increased dramatically. The capillary water absorption and ultrasonic wave velocity of concrete are similar to that of the mechanical properties of concrete,which indicates that the microstructure defect and the mechanical properties of concrete have good synchronicity.