有约束应力高温全过程后混凝土轴压力学性能试验研究

采用高温抗压试验炉进行了有约束应力作用下混凝土在经历升温、降温及冷却全过程作用后的轴压力学性能试验研究,主要研究约束应力水平和温度等级对升降温及冷却全过程中的混凝土高温变形特性与高温后混凝土强度、弹性模量和应力-应变关系等性能的影响规律。结果表明:约束应力使混凝土产生明显的残余压缩变形,且对高温后混凝土抗压强度和弹性模量有显著影响;无约束应力高温后混凝土的抗压强度随着温度的升高经历低温衰退、强度恢复、高温衰退3个阶段,n≤0.4时有约束应力混凝土也表现出相同的规律;约束应力可提高高温后混凝土的弹性模量,但其值仍明显低于常温弹性模量;有约束应力高温全过程后混凝土破坏突然,明显变脆。

Experimental study on mechanical behaviors of axially-stressed concrete after exposure to high temperatures

A specially-built electrical furnace was used to experimentally study the mechanical behaviors of the concrete prism specimens with sustained restrained stress during the entire high temperature exposure including at ambient conditions and during the heating and cooling phases.The experimental study mainly focused on the effects of high temperature and restrained stress level on concrete deformations during heating and cooling phases and residual compressive strength,modulus of elasticity,stress-strain relations after cooled to ambient conditions.The tested results showed that all the specimens after exposure to high temperatures with sustained restrained stress would suffer remarkable residual compressive deformations and the sustained restrained stress would have a significant effect on the residual compressive strength and modulus of elasticity of concrete after exposure to high temperatures.The residual compressive strength of concrete with no restrained stress experienced an initial reduction at lower temperatures,recovery and decay at higher temperatures.For restrained stress level up to 0.4,the concrete specimens with sustained restrained stress experienced the same variation trend of residual compressive strength deterioration.Restrained stress could improve the residual modulus of elasticity of concrete,but the residual modulus of elasticity was remarkably lower than that of the tested concrete specimens at room temperature.After exposure to high temperatures,concrete specimens with sustained restrained stress would become brittle and be loaded to failure suddenly.The tested results can provide a reference for reasonably assessing the mechanical properties of concrete with restrained stress after exposure to high temperatures.