UHPC微裂纹在蒸汽环境中的快速愈合机制  

Rapid Healing Mechanism of UHPC Microcracks in a Steam Environment

作　　者：谭昱 吕梁胜 王俊颜[2] 肖汝诚[3] 方明山 TAN Yu;LYU Liang-sheng;WANG Jun-yan;XIAO Ru-cheng;FANG Ming-shan(College of Civil Engineering and Architecture,Zhejiang University,Hangzhou 310058,Zhejiang,China;Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education,Tongji University,Shanghai 201804,China;School of Civil Engineering,Tongji University,Shanghai 200092,China;Zhejiang Communications Investment Group Co.Ltd.,Hangzhou 310020,Zhejiang,China)

机构地区：[1]浙江大学建筑工程学院,浙江杭州310058 [2]同济大学先进土木工程材料教育部重点实验室,上海201804 [3]同济大学土木工程学院,上海200092 [4]浙江省交通投资集团有限公司,浙江杭州310020

出　　处：《中国公路学报》2021年第8期55-64,共10页China Journal of Highway and Transport

基　　金：交通运输行业重点科技项目清单项目(2019-MS1-016);浙江省交通运输厅科研计划项目(2019-GXKY-01)。

摘　　要：为了在蒸汽环境中快速修复超高性能混凝土(UHPC)浇筑过程中产生的收缩裂纹和结构服役过程中产生的裂纹,加速UHPC结构刚度和抗渗性能的恢复,需要确定不同损伤程度的微裂纹在蒸汽环境中的快速愈合机制。因此,选取拉伸变形(应变为1000×10^(-6),1500×10^(-6),2000×10^(-6))作为损伤指标,将损伤开裂后的UHPC试件分别放置在蒸汽环境中1,3,5d,研究微裂纹在蒸汽环境中的快速愈合机制。通过直接拉伸试验、气体渗透试验和声发射分析不同拉伸变形的UHPC试件在蒸汽环境中的自愈合行为。拉伸试验结果表明:放置在蒸汽环境中,预裂试件的弹性模量的恢复程度随着拉伸变形的增大而减小,但依然大于预裂至相同拉伸应变的未愈合试件(放置在室内环境中)的弹性模量。刚度恢复程度随着放置在蒸汽环境时间的增长而增大,但愈合到一定程度后,延长放置时间对愈合的效果不明显。采用气体渗透试验表征了微裂纹的愈合程度,结果表明蒸汽环境中的微裂纹能快速愈合,但随着拉伸变形的增加,自愈合的程度减小,表明拉伸变形越大,微裂纹越多,自愈合产物填充所需时间越长。声发射分析表明:UHPC内部发生损伤时才会产生声发射源,在重新加载阶段,对于已经愈合的微裂纹,在微裂纹的2个界面之间新形成的晶体会再次开裂,此时会检测到声发射源。然而,对于未愈合的微裂纹重新张开时,则不会产生声发射源,直至旧裂纹发展和新裂纹的产生才会产生声发射源。To accelerate the recovery of the structural stiffness and impermeability of ultra-high performance concrete(UHPC)in a steam environment by shrinkage cracks generated during the pouring and service processes of UHPC,it is necessary to determine the rapid healing mechanism of microcracks with different damage degrees in a steam environment.Therefore,in this study,tensile deformation(1000,1500,and 2000microstrains)was adopted as the damage index,and the UHPC specimens after damage cracking were placed in a steam environment for 1,3,and 5 days,respectively,to study their rapid healing mechanisms.The self-healing behavior of UHPC specimens with different tensile deformations in a steam environment was studied by direct tensile test,air permeability test,and acoustic emission analysis.The results of the tensile test indicated that the elasticity modulus of the precracked specimens when placed in the steam environment decreased with an increase in tensile deformation.However,it remained larger than that of the unhealed specimens with similar tensile strains when placed in an indoor environment.In the steam environment,the degree of stiffness restoration increased with increasing time;however,the effect of prolonged setting time on healing at a certain degree,was not significant.An air permeation test was utilized to characterize the healing degree of the microcracks.The results indicated that the microcracks in the steam environment could heal rapidly;however,with the increase in tensile deformation,the degree of self-healing decreased,thus indicating that the larger the tensile deformation,the more the microcracks emerge,and the more time required to fill the self-healing products.Acoustic emission analysis indicated that the acoustic emission source will only be generated when damage occurs inside the UHPC.In the reloading stage for the healed microcracks,the newly formed crystal between the two interfaces of the microcracks will crack again,and the acoustic emission source will be detected.However,when the unhealed

关 键 词：桥梁工程 超高性能混凝土 蒸汽环境 快速愈合 气体渗透 声发射 

分 类 号：U444[建筑科学—桥梁与隧道工程]