高温后再生砂浆单轴受压应力-应变关系试验研究

Experimental research on uniaxial compressive stress-strain relationship of recycled mortar after high temperature

为得到高温后再生砂浆单轴受压应力-应变关系,对72个70.7 mm×70.7 mm×216 mm不同再生细骨料取代率的再生砂浆试件进行单轴受压试验,实测了20~800℃温度作用后试件的应力-应变全曲线,分析了再生砂浆的高温性能,以及再生细骨料取代率和经历温度对再生砂浆峰值应力、峰值应变、弹性模量、泊松比、体积应变和单轴受压应力-应变全曲线的影响。结果表明:不同再生细骨料取代率的砂浆试件高温后的表面颜色均经历灰色、浅红、灰白的过程,温度高于400℃以后开始出现裂缝、掉皮、疏松等现象;再生砂浆试件高温后质量损失率高于普通砂浆试件,温度高于400℃以后各类砂浆试件的质量损失率保持稳定;相同温度下,随着再生细骨料取代率的增加,单轴受压应力-应变曲线峰值应力减小,峰值应变增加,弹性模量减小,脆性更加显著;随着温度的升高,峰值应变逐渐增大,而峰值应力、弹性模量与体积应变临界点对应的应力比均持续减小,应力-应变曲线渐趋扁平。通过回归分析,建立了再生砂浆高温后峰值应力、峰值应变、弹性模量与温度的关系计算式,以及单轴受压分段式本构方程。

To obtain the constitutive relationship under uniaxial compression of recycled mortar after high temperature,the uniaxial compression experiments were conducted on 72 prismatic specimens with the size of 70. 7 mm × 70. 7 mm ×216 mm after being exposed to 20-800 ℃. The effects of recycled fine aggregates content and exposure temperature on different mechanical properties of recycled mortar were investigated. The test results show that: the surface color of all kinds of recycled mortar exhibits the sequence of grey,light red,and ashen. Cracking,spalling and loosening occur after 400 ℃; the mass loss rate of recycled mortar is much higher than natural mortar,and the mass remains stable after400℃; After the same temperature,it 's found that the peak point moves down with the increase of recycled fine aggregate replacement rate,while the elastic modulus and ductility deteriorate gradually; as the temperature increases,the peak strain increases gradually,while the peak stress,elastic modulus and volumetric strain critical point corresponding stress ratio continue decreasing,besides,the stress-strain curve turns to be flat. Through regression analysis,the formulas reflecting the relations between peak stress,peak strain,elastic modulus and the temperature,as well as the segmented constitutive equation under uniaxial compression are proposed.