摘要
基于自然潮差环境下840 d的暴露试验,测试了粉煤灰掺量分别为水泥质量的0%、20%、30%、40%和50%混凝土中自由氯离子浓度,计算了氯离子表观扩散系数及即时扩散系数;提出了混凝土氯离子扩散性能稳定时间的分析方法,并分析了粉煤灰掺量对试验混凝土氯离子扩散性能稳定时间的影响;同时,通过核磁共振技术(NMR)测得不同暴露时间后混凝土的弛豫时间和孔隙率等混凝土微观结构参数,分析了掺量对粉煤灰混凝土氯离子即时扩散系数及微观结构参数时变性的影响,探讨了混凝土氯离子扩散性能稳定时间与其微观结构参数时变性之间的关系。结果表明,混凝土氯离子扩散系数均其随暴露时间的延长和粉煤灰掺量的增大而减小;不同粉煤灰掺量的混凝土氯离子即时扩散系数达到稳定时间不一致,且其氯离子即时扩散系数的稳定时间随粉煤灰掺量的增加而缩短;混凝土的孔隙率均随暴露时间的延长而减少,表现出与其氯离子即时扩散系数一致的明显时变性;混凝土孔隙的弛豫时间及孔隙率等微观结构参数的时变性,总体上反映了粉煤灰掺量对混凝土氯离子扩散性能时变性及其稳定时间的影响。
Based on 840 d exposure test in the natural tidal environment,the stable time of fly ash concrete was studied.First,the free chloride concentrations of concrete with 0%,20%,30%,40%and 50%fly ash at six exposed times were obtained.Second,the apparent and instantaneous chloride diffusion coefficients of concrete were calculated.Furthermore,the calculated method of stable time of chloride diffusion coefficient in concrete was proposed and the influence of fly ash content on the stable time was analyzed.Finally,the influence of fly ash on the time dependency of instantaneous chloride diffusion coefficient and the microstructure parameters is obtained based on the relaxation time and porosity of fly ash concrete under different exposure time is obtained by nuclear magnetic resonance(NMR)technology test.Results show that both apparent and instantaneous chloride diffusion coefficients decrease with the increase of exposure time and fly ash content.In addition,the stable time of instantaneous chloride diffusion coefficient of concrete with different fly ash content is inconsistent,and the stable time of instantaneous chloride diffusion coefficient is shorter with the increase of fly ash content.The total porosity of concrete decreases with the extension of exposure time,which shows an obvious time dependency consistent with the instantaneous chloride diffusion coefficient.In addition,the time dependency of the microstructure parameters such as the relaxation time and the total porosity of concrete generally reflects the influence of fly ash content on the time dependency and stable time of concrete chloride diffusion properties.
作者
高延红
汪蒙
周晓芸
章玉容
张俊芝
GAO Yanhong;WANG Meng;ZHOU Xiaoyun;ZHANG Yurong;ZHANG Junzhi(College of Civil Engineering and Architecture,Zhejiang University of Technology,Hangzhou 310014,China;Key Laboratory of Civil Engineering Structure&Disaster Prevention and Mitigation Technology of Zhejiang Province,Hangzhou 310014,China)
出处
《自然灾害学报》
CSCD
北大核心
2020年第6期30-40,共11页
Journal of Natural Disasters
基金
国家自然科学基金项目(52079124,51279181)
浙江省自然科学基金项目(LY19E090006,LQ18G010007,LY17E090007)。
关键词
粉煤灰混凝土
潮差环境
氯离子扩散系数
稳定时间
微观结构参数
fly ash concrete
tidal environment
chloride diffusion coefficient
stable time
microstructural parameter
