Accelerated curing of concrete with high volume Pozzolans-resistivity, diffusivity and compressive strength

This investigation presents results of the temperature effect on durability properties (resistivity and diffusivity) and compressive strength of concrete with pozzolans, and the effect of pozzolanic admixtures on microstructure and chemical compositions of concrete pore solution. A set of experiments were carried out. Temperature dependence of electrical resistivity and chloride diffusivity was studied by dynamic temperature tests. Accelerated curing regimes involving curing concrete specimen’s in 35°C lime water with different durations were tested. Compressive strength test, resistivity measurement and rapid chloride migration (RCM) test were performed. A leaching method was used to measure pH and conductivity of concrete pore solution. Based on the results, general normalization equations were developed to describe the temperature effect on resistivity and diffusivity of concrete. The accelerated curing regimes were found to increase the compressive strength and resistance to chloride ion penetration at short-term and long-term. With the developed correlation between resistivity and migration coefficients, it is possible to employ the resistivity measurement as an alternative or replacement of the RCM test to evaluate resistance of chloride ion penetration of concrete. Pozzolanic admixtures were found to decrease both pH and conductivity of concrete pore solution as the replacement ratio increased. Moreover, the migration coefficients were found to be greatly correlated to the microstructure properties of concrete, such as porosity, formation factor and tortuosity.