高温后HVFA-SHCC的单轴压缩力学性能及本构关系

Uniaxial Compressive Behavior and Constitutive Relationship of HVFA-SHCC after Exposure to High Temperature

采用40mm×40mm×160mm棱柱体试件,研究了高温后大掺量粉煤灰-应变硬化水泥基复合材料(HVFA-SHCC)的单轴压缩力学性能,探讨了不同目标温度(100、200、400、600、800℃)和不同冷却方式(自然冷却、浸水冷却)条件下HVFA-SHCC试件抗压强度、弹性模量、压缩韧性、破坏模式及质量的变化.采用扫描电子显微镜(SEM)对试件的微观结构进行分析,获得了高温后HVFA-SHCC单轴压缩性能的劣化机理.结果表明:当温度低于200℃时,温度对试件力学性能及质量损失的影响较小;400~800℃时,试件内部结构变得疏松,残余力学性能劣化严重,尤其是800℃时,试件的抗压强度仅为常温状态的39.9%,弹性模量为常温状态的32.3%,压缩韧性指数为常温状态的59.0%,质量损失率达15.5%;浸水冷却试件的残余力学性能得到了一定程度的提高.同时,基于试验结果,建立了高温后HVFA-SHCC的单轴压缩本构方程.

Investigations on the residual uniaxial compressive behaviors of strain hardening cementitious composites with high-volume of fly ash(HVFA-SHCC)subjected to elevated temperatures were carried out.Specimens with dimension of 40mm×40mm×160mm were exposed to different temperatures(100,200,400,600,800℃).Residual compressive strength,stress-strain curves,compressive toughness,elastic modulus and failure mode were determined after two cooling methods(natural cooling and water cooling).Scanning electron microscope(SEM)was used to analyze the degradation mechanism of HVFA-SHCC at mesoscale level.Experimental results indicate that the temperature has little effect on the mechanical properties and mass loss of HVFA-SHCC when temperature is lower then 200℃.At 400800℃,the internal micro-structures of HVFA-SHCC specimen become loose and the residual mechanical properties deteriorate seriously.When the temperature is higher than 800℃,the average residual compressive strength,the elastic modulus and the toughness index of the samples is only 39.9%,32.3%and 59.0%of that at room temperature,respectively.And the mass loss rate is increased to 15.5%.Meanwhile,the effect of cooling method on residual mechanical properties is significant.The specimens cooled in water exhibit superior residual mechanical performance.Finally,based on the test results,the uniaxial compressive constitutive relationship of HVFA-SHCC after high temperature is proposed.