Experimental study on chloride permeability in concrete by non-contact electrical resistivity measurement and RCM

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A new non-contact electrical resistivity (NC-ER) measurement technique was proposed to measure the chloride diffusion coefficient of cement-based materials, and the results from testing were compared with the rapid chloride migration test, traditionally called RCM. Cement pastes with water cement ratios of 0.30, 0.35 and 0.40, and concrete with a water cement ratio of 0.4 were prepared for the chloride diffusion coefficient measurement by the two methods.The chloride diffusion coefficient results obtained by both approaches show a reasonable decrease with hydration age and increase with the increase of water cement ratio. The results for the pastes from the RCM test are in range of (0.69∼3.15)×10−7cm2/s at 3d∼80d, and the results from the NC-ER test are in the range of (0.53∼1.71)×10−7cm2/s., which are of the same order of magnitude and follow a linear relationship DRCM=1.8821DNC-ER−0.3506 (R2=0.9205).From the NC-ER test, the chloride diffusion coefficient of concrete C0.4 is lower than that of paste P0.3 at the same ages and was verified by the porosity and formation factor analysis, while the RCM test obtained opposite trends. A better linear correlation between the chloride diffusion coefficient of the concrete and paste samples was obtained based on the NC-ER test. It can be deduced that the NC-ER set-up has advantages over the RCM set-up in measuring the chloride diffusion coefficient of concrete, such as there being no electrodes in the NC-ER setup which eliminates errors, and taking a much shorter time (about 5min) to complete a test.