混凝土高温后抗压强度的影响因素研究

对强度等级分别为C20、C25和C30的硅质骨料和钙质骨料混凝土立方体试块高温后的抗压强度进行了试验，分析了受火温度、冷却方式、骨料类型、静置时间和强度等级等因素对混凝土高温后抗压强度的影响。试验结果表明:随温度的升高混凝土抗压强度总体呈下降趋势，在受热温度较低时，冷却方式对受热后混凝土强度的影响较小，在受热温度较高时，冷却方式对受热后混凝土强度的影响较大；骨料类型对高温后混凝土强度的影响不可忽略，温度低于550℃时，硅质骨料混凝土强度高于钙质骨料，但当超过750 ℃后，硅质骨料混凝土强度迅速降低，温度越高，钙质骨料相对于硅质骨料的耐火优越性表现的越明显；受火灾作用后，混凝土强度值随着时间的推移趋于稳定，在某一静置时间，混凝土强度都会出现最小值；高温后不同强度等级混凝土抗压强度变化趋势相似，高温后抗压强度变化规律受强度等级的影响不能忽略。

Study on the influencing factors of concrete compressive strength after elevated temperature

Compressive strength test of concrete cube specimens made by siliceous and calcareous coarse aggregates after high temperature was carried out，whose strength grades were C20，C25 and C30 respectively.Considering the effects of temperatures，cooling methods，aggregate types，standing time and strength grades，analyzed the influence of these factors on concrete compressive strength respectively.The test results show that the compressive strength decreases with the temperature rising in general.In the mass，the cooling methods have minimal impact on the heated concrete strength at lower temperatures，while they have a great influence on concrete strength at higher temperatures.The effect of aggregate types on concrete strength after elevated temperature can’t be ignored.Below 550 ℃，the siliceous aggregate concrete has higher strength than calcareous aggregate concrete，but the strength of siliceous aggregate concrete decreases rapidly over 750 ℃.So compare to siliceous aggregate concrete，the higher the temperature is，the more significant fire resistance of calcareous aggregate concrete has.Concrete strength values become steady with the lapse of time after the fire，and the minimum of concrete strength appear at some standing time.In addition，after high temperature the trends of changes on concrete compressive strength for different strength grades are similar，whereas the influence of strength grades on concrete compressive strength can’t be neglected.