| This research investigated AC impedance characteristics of hardened cement paste, mortar and concrete with Portland cement-fly ash-slag ternary cementitious binder. In AC impedance studies of hardened cement paste, with five groups of specimens(water to cement ratio from0.25to0.5) at different ages, the development of AC impedance characteristics of a pure cement paste hardened paste in hydration process has been obtained. The relationship between bulk resistance of paste and hydration process has been determined, and accordingly, the regression equation among bulk resistance, water-to-cement ratio and ages of hydration has been established. The same time, the model of hardened cement paste pore structure has established, from that, the proportion of connected and non-connected pore can be shown, and the evaluation of the pore structure provides a simple and reliable method. From analyzing AC impedance spectroscopy of the hardened cement paste age, development and changes of pore solution concentration with age has been obtained. In addition, with studying on paste of using fly ash and slag replaced, found AC impedance characteristics of paste with different contents of fly ash and slag, and that it is important to using fly ash and slag for improving the pore structure of hardened paste, but, before7days of hardening, increasing the replacement of slag, is benefit, the same time, to improving the slurry density at later, the slag content should be greater the40%. By the AC impedance studies of hardened paste, using fly ash, slag at same time is very useful to improve the density of paste, but also need to note that the content of slag should be higher than27%but not more than51%. With studing on capacitance of hardened paste mixed with fly ash, slag system capacitance, found the corresponding relationship of the pore solution ion concentration and capacitance. This study investigated the impedance characteristics of ternary cementitious materials and obtained the electrical resistance contours of the materials at different ages. It was found that when total content of fly ash and slag powder was in the range of50-65%and fly ash to slag content ration was around1, mortars made with the ternary cementitious material demonstrated the highest resistance. The results show that the system of cementitious material paste and mortar systems, the AC impedance spectrum in a manner consistent, but the overall resistance rate is basically the same, at the same time, the impact of mineral admixtures on resistance, not the aggregate join changed. This paper, the resistance of different water to cement ratio or mineral admixture concrete for stray current has been studied, using a simulated subway form of electrochemical corrosion of reinforcing steel in concrete structures to carry out reinforced concrete accelerated corrosion test, through AC impedance technology, the AC impedance characteristics changes before and after the steel corrosion degree of steel corrosion evaluation, combined with the mechanical model, predicted the service life of concrete structure before cracking caused by expansion of steel, and combination studies have been carried out on pulverized coal ash, slag, performance to stray current, the study found, concrete reinforced anti-electrochemical corrosion and AC impedance characteristics of concrete has a direct relationship. |
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