暴露于高温环境后的超高性能混凝土自愈合能力研究

Study on self-healing ability of UHPC exposed to high temperature

超高性能混凝土(UHPC)以其优越的力学性能和耐久性能在工程建设中具有广阔的应用前景.然而,UHPC内部结构致密,耐高温性能不佳,在高温环境下暴露后其各方面性能会大幅度下降,限制了其在结构工程和地下施工中的应用,本研究旨在研究UHPC在暴露于高温环境后的自修复能力.UHPC采用水泥-粉煤灰-硅灰水泥基体和钢纤维设计制备,掺入聚丙烯纤维以增强耐高温性.通过模拟在地下环境中的暴露,评估了UHPC在高温暴露后的自愈合能力.自愈合能力是通过测量高温暴露前后和自愈合试验后的抗压强度、弯曲强度及裂纹宽度的变化来进行表征.自愈合试验对UHPC断裂韧性的影响通过裂口张开位移(CMOD)测试和数字图像相关方法(DIC)表征.研究发现,地下水环境的自愈合效应可以恢复UHPC的刚度、抗拉强度,以及高温后裂纹宽度的愈合.同时,由于钢纤维的腐蚀,抗压强度的恢复很小.本研究可为拓宽UHPC的应用领域提供坚实的基础.

Ultra-High Performance Concrete(UHPC)has a broad application prospect in engineering construction with its superior mechanical properties and durability performance.However,UHPC has a dense internal structure and poor high temperature resistance,and its performance in all aspects decreases significantly after exposure to high temperature environment,which limits its application in structural engineering and underground construction.This study aims to investigate the self-healing ability of UHPC after exposure to high temperature environment.UHPC is prepared using cement-fly ash-silica fume cement matrix and steel fiber design,with polypropylene fiber blended to enhance high temperature resistance.The self-healing ability of UHPC after high-temperature exposure was evaluated by simulating the exposure in the subsurface environment.The self-healing ability was characterized by measuring the changes in compressive strength,flexural strength and crack width before and after the high temperature exposure and after the self-healing test.The effect of self-healing tests on UHPC fracture toughness was characterized by fracture opening displacement(CMOD)tests and digital image correlation(DIC)methods.It was found that the self-healing effect of the groundwater environment restores the stiffness and tensile strength of UHPC,as well as the healing of high-temperature cracks.Meanwhile,the recovery of compressive strength was minimal due to corrosion of steel fibers.This study can provide a solid basis for broadening the application fields of UHPC.