混凝土的高温变形与微结构演化

Deformation and microstructure evolution of concrete subjected to elevated temperature

研究了普通混凝土及纤维混凝土在高温作用下的热变形、力学性能及微结构演化.试验结果表明:普通混凝土和纤维混凝土在200℃高温作用下抗压强度下降了18%和8%;800℃时下降了70%和33%.混凝土与骨料随环境温度增加线性膨胀,当温度达到900℃时,其线膨胀率分别达到1%和3.4%.水泥净浆在160℃前先膨胀,后线性收缩;环境温度为800℃时,其线性收缩率为1.5%,质量损失率为19.1%.骨料与净浆在高温作用下的变形差异导致了混凝土浆集界面区裂纹的产生与扩展.聚丙烯纤维掺加并不能显著改变混凝土及浆体的热变形性能,但环境温度由400℃升至800℃,熔融纤维空洞直径仍能保持原有直径的74%,有助于水蒸气的排出.

The evaluations of the deformation behavior,compressive strength and microstructure for the ordinarily concrete（OPC） and fiber-reinforced concrete（FRC） at high temperature are investigated.Results show that the compressive strengths of the ordinarily concrete and the fiber-reinforced concrete decrease by 18% and 8% at 200℃,respectively.At 800℃,70% and 33% of strength losses for the OPC and the FPC occur,respectively.The concrete and the coarse aggregates linearly expand with the increase in the environment temperature,and their linear expansion percentages are about 1% and 3.4% at 900℃.The paste expands at a temperature below 160℃,and then linearly shrinks with the increase in the temperature.When the temperature is 800℃,the values of the linear shrinkage percentage and the mass loss percentage are 1.5% and 19.1%,respectively.Therefore,the differences in deformation of pastes and aggregates result in the formation and expansion of microcracks in the interface of pastes and aggregates,leading to the failure of the concrete.The addition of the fiber in the concrete and pastes cannot result in a change of heat deformation.But when the temperature changes from 400 to 800℃,the diameter of the melted fiber viod only decreases by 26%,which contributes to water discharge.