混凝土RCM试验分析的面均法研究

Area average method for RCM test of concrete

现行RCM试验普遍采用点均法确定混凝土的氯离子扩散系数,存在结果离散性大且不稳定等问题。为此,提出混凝土RCM试验分析的面均法(area average method)。首先,通过试验设计制备74组具有不同氯离子扩散系数的混凝土试件,并据此开展变电压RCM试验;其次利用图像获取装置和Adobe Photoshop软件测量混凝土试件轴向断面上的氯离子扩散面积,据此计算氯离子扩散深度及扩散系数。最后,通过对比分析验证文中面均法的合理性,并建立点均法与面均法结果之间的转换关系式。结果表明:点均法测量结果离散性大,且随测点间距的减小而变小;只有当测点间距小于2mm时点均法结果才能收敛,且与面均法结果相吻合。而面均法可以有效克服点均法的缺陷,操作方便快捷,结果离散性小。国内外现行规范普遍采用10mm间距的测点布置方案测试混凝土的氯离子扩散系数,导致RCM试验结果偏大。

In current RCM test,the chloride diffusion coefficient of concrete is usually determined by the point average method(PAM)in which the problem of unstable and inaccurate results exists.In order to overcome this limitation,the area average method(AAM)is proposed to estimate the chloride diffusion depth in concrete.Firstly,the areas of chloride diffusion were measured in the axial sections of concrete specimens by means of the image acquisition device and the Adobe Photoshop software.Both the chloride diffusion depth and chloride diffusion coefficient were determined according to the chloride diffusion area.Then the AAM was validated by test data and comparison with the PAM.Finally,the relationship model between the results by the AAM and the PAM was developed by statistical analysis of the test data.Research results show that the results by the PAM have larger fluctuation and decrease with the distance of measuring.Only when the distance of the measuring points is less than 2 mm can the results by the PAM converge to the results by the AAM.It can be concluded that the proposed AAM is convenient and easy to use,yielding stable and less fluctuating results.However,for the cases with 10 mm distance of measuring points,the PAM adopted in the current design specifications will overestimate the chloride diffusion coefficient of the concrete.