自然潮差环境下混凝土渗透性稳定时间及机理

Stable time and mechanism of concrete permeability in naturaltidal environment

基于自然潮差环境下1160 d的暴露试验,测试并计算了在不同暴露时间后不同水灰比普通混凝土的氯离子扩散系数、水及本征气体渗透系数;提出了统一的混凝土渗透系数稳定时间的计算方法,并分析了水灰比对混凝土三种渗透性稳定时间的影响。同时,采用了核磁共振技术跟踪测得了不同水灰比混凝土的弛豫时间,并得到孔隙率等微观结构参数,分析了水灰比对普通混凝土渗透系数及其微观结构参数时变性的影响,最后探讨了两者稳定时间的关系。结果表明,普通混凝土三种渗透性及其稳定时间均随水灰比的加大而增加;混凝土孔隙率随暴露时间延长而降低的过程,与其渗透系数的时变性相似,且两者的稳定时间是相关的,其中混凝土水渗透性稳定时间与其孔隙率稳定时间最接近;混凝土贡献孔隙率(100~1000 nm)的演变特点与其孔隙率的是相类似的,但与其渗透性的稳定时间相关性更高。混凝土的氯离子即时扩散系数最先稳定,其次稳定的是水渗透性,气体渗透性最后稳定。

Based on 1160-day exposure tests to ocean tidal environment,three permeability coefficients(water,intrinsic gas and chloride)of ordinary concrete were measured and calculated for different water-cement ratios and different exposure time periods.A unified method for calculating the corresponding stable time of these coefficients was developed,and the influence of water-cement ratio on the stable time was analyzed.Then,we adopted the nuclear magnetic resonance to track the relaxation time and microstructure parameters of concrete,and examined the influence of the ratio on the time dependence of both permeability coefficients and microstructure parameters.Finally,the relationship between the stable times of both was studied.The results show the three permeabilities of ordinary concrete and their stable times increase with the increasing ratio.The decreasing trend of total porosity with exposure time is similar to that of time-dependent permeability coefficients,showing a correlation between the both stable times;the stable time of water permeability has the highest correlation with that of total porosity.And the evolution of contribution porosity(100-1000 nm)is similar to that of total porosity,but the stable time of permeability is more related to it.The instantaneous chloride diffusion coefficient is stable first,followed by water permeability and gas permeability.