高强混凝土火灾后力学性能退化及高温爆裂机理研究

发布时间：2018-01-06 09:14

  本文关键词：高强混凝土火灾后力学性能退化及高温爆裂机理研究　出处：《中国矿业大学》2014年硕士论文　论文类型：学位论文

  更多相关文章： 高强混凝土 高温 孔隙水饱和度 力学性能 无损检测 爆裂模型

【摘要】：本文运用正交设计方法研究了受火温度、强度等级、孔隙水饱和度等因素对高强混凝土高温后劣化特征、力学性能、断裂性能和爆裂特征的影响规律，，对比分析了不同无损检测方法对高温后混凝土强度检测的可行性和适用性，在综合高温试验结果和已有高温爆裂机理的基础上提出了混凝土高温“蒸汽爆炸”模型，主要取得如下的研究成果： 利用“双掺”技术成功试配C80高强混凝土，并对试配经验进行了总结。对高强混凝土立方体试块高温后力学性能进行了试验研究，分析了受火温度、混凝土强度等级、孔隙水饱和度对高温后相对抗压强度以及高温后水中养护强度恢复效果的影响，得到了混凝土相对残余抗压强度随受火温度、强度等级、孔隙水饱和度的变化规律。通过方差分析表明，对混凝土高温后相对残余抗压强度的影响因素中，受火温度影响高度显著，受火温度越高，混凝土力学性能劣化越严重；孔隙水饱和度有影响，强度等级影响不显著。 运用回弹法、超声法、综合法和红外热像法等无损检测方法对不同受火温度、强度等级、孔隙水饱和度的高强混凝土高温后抗压强度进行了检测，建立了试验指标与抗压强度和受火温度的回归曲线。通过误差分析结果表明，本文所用无损检测方法满足相关技术规程精度要求，适用于混凝土高温后的质量检测。其中，超声回弹综合法对混凝土强度检测的精度最高，红外热像法对混凝土受火温度的测定精度最高。当受火温度达到600℃以上时，红外热像法的综合适用性更好。 通过三点弯曲切口梁试验对混凝土高温后断裂性能进行了研究，分析了受火温度、强度等级、孔隙水饱和度对混凝土高温后相对残余断裂韧度和断裂能的影响，通过有限元软件对三点弯曲切口梁的应力强度因子进行了验证计算。方差分析结果表明，对高温后混凝土断裂性能劣化影响因素中，受火温度高度显著，孔隙水饱和度有影响，强度等级影响不显著。混凝土高温后残余断裂韧度与抗压强度呈线性正相关，断裂能随抗压强度的变化规律不明显。 研究了不同受火温度、强度等级、孔隙水饱和度对混凝土试块高温后的表面裂缝宽度、烧失量、孔隙率等劣化特征和爆裂特征的影响规律，并对高温时混凝土试块内部的温度场进行了试验检测和有限元数值模拟。最后在综合试验结果和已有爆裂机理的基础上提出了混凝土高温爆裂的“蒸汽爆炸”模型，并利用该模型对混凝土高温爆裂典型现象和部分高温爆裂代表性研究成果进行了较为合理的解释分析。
[Abstract]:In this paper, the effects of fire temperature, strength grade and pore water saturation on the deterioration, mechanical properties, fracture properties and burst characteristics of high strength concrete after high temperature are studied by orthogonal design method. The feasibility and applicability of different nondestructive testing methods for testing the strength of concrete after high temperature are compared and analyzed. On the basis of synthesizing the results of high temperature test and the existing mechanism of high temperature explosion, a high temperature "steam explosion" model of concrete is proposed. The main research results are as follows: The C80 high strength concrete was successfully tested by "double admixture" technique, and the experience of the test was summarized. The mechanical properties of high strength concrete cube after high temperature were studied and the fire temperature was analyzed. The influence of concrete strength grade, pore water saturation on the relative compressive strength after high temperature and the recovery effect of curing strength in water after high temperature, the relative residual compressive strength of concrete is obtained with the fire temperature and strength grade. Analysis of variance shows that, among the factors affecting the relative residual compressive strength of concrete after high temperature, the influence of fire temperature is significant, and the higher the fire temperature is. The worse the mechanical properties of concrete are; Pore water saturation has influence, but strength grade has no significant effect. The compressive strength of high strength concrete with different fire temperature, strength grade and pore water saturation was tested by non-destructive testing methods such as rebound method, ultrasonic method, comprehensive method and infrared thermal image method. The regression curves of test index, compressive strength and fire temperature are established. The results of error analysis show that the nondestructive testing method used in this paper can meet the precision requirements of relevant technical specifications. It is suitable for the quality detection of concrete after high temperature. Among them, the ultrasonic rebound comprehensive method has the highest precision to the concrete strength detection. The infrared thermal image method has the highest accuracy in measuring the temperature of concrete under fire, and the comprehensive applicability of the infrared thermal image method is better when the temperature of fire is above 600 鈩

本文编号：1387226