| 蒋敏,方万军.火灾环境下热-冷循环作用对混凝土性能的影响研究[J].火灾科学,2021,30(1):24-29. |
| 火灾环境下热-冷循环作用对混凝土性能的影响研究 |
| Influence of heat-cold cycling on concrete in fire environments |
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| DOI：10.3969/j.issn.1004-5309.2021.01.04 |
| 基金项目:浙江省建设科研项目(2019K174) |
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| 中文关键词: 混凝土 热-冷循环 结构完整性 力学特性 矿物成分 微观结构 |
| 英文关键词:Concrete Heat-cold cycles Structural integrity Mechanical properties Mineral composition Microstructure |
| 摘要点击次数: 118 |
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| 中文摘要: |
| 为了研究混凝土材料的结构与力学特征受火灾热-冷作用的影响规律,通过测量不同热-冷作用次数下的试样质量和密度损失率定量表征了混凝土结构损伤程度;通过开展单轴压缩实验对热-冷作用对其力学行为的变化规律进行了研究;最后进行XRD衍射实验和SEM扫描电子显微镜对混凝土的成分与微观结构进行探测。实验结果表明:在火灾热-冷作用下,混凝土外观的损伤程度不断加深;由于水泥凝胶体逐渐剥落、减少,混凝土的质量和密度损失率呈上升趋势,且上升速率先快后慢;混凝土的强度指标—无侧限抗压强度、弹性模量随循环次数增加逐渐衰减,且衰减速率先快后慢,而变形性能指标—峰值应变与弹性模量-循环次数的曲线呈反对称分布;依据XRD衍射实验结果,推断热-冷循环对混凝土的损伤效应主要是由于水泥水化物中Ca(OH)2的分解;由SEM实验观察到水泥水化物在热-冷作用过程中不断流失,裂隙规模不断扩大,从而使得混凝土的结构完整性和力学特性在热-冷循环过程中出现衰变。 |
| 英文摘要: |
| This work aimed to study the heat-cold cycling effects on the mechanical and damage characteristics of concrete materials. The damage degree of the concrete structure was investigated by measuring the sample mass under different heat-cold cycles. The mechanical behavior of heat-cold cycling effects was studied by an unconfined compression test. The XRD diffraction test and SEM scanning electron microscope were used to detect the mineral composition and microstructure of concrete. The results show that the process of heat-cold cycling deepens the erosion degree of concrete samples continuously. The mass-loss rate and density change rate of concrete increase due to the gradual peeling and reduction of cement gel. The strength indexes of concrete-uniaxial compressive strength and elastic modulus gradually attenuated with the increase of cycles, and the decay rate was first faster and then slower, while the curve of deformation performance indexes-peak strain and elastic modulus-cycles showed an anti-symmetric distribution. According to the results of XRD diffraction experiments, it is inferred that the heat-cold cycling effect on concrete is mainly due to the thermal expansion effects in the cement gel. It was observed by SEM tests that the cement gel of concrete was continuously lost in the process of thermal reactions, and the crack scale was continuously enlarged so that the structural integrity and mechanical properties of concrete were decaying in the heat-cold cycling process. |
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