| Concrete structures located in rivers,lakes and other water environments,are easily corroded by soft water,causing the material durability degradation and structural performance reduction of concrete.In order to reveal the durability degradation of cement based materials caused by calcium leaching in water environment,calcium leaching experiments of cement paste mixed with compound mineral admixture in deionized water and 6M ammonium chloride solution were designed in this paper.Influence of different mineral admixtures on the erosion resistance of the hardened cement paste was studied through the experimental test and numerical simulation using the model.The main research results and conclusions are as follows:(1)In deionized water corrosion condition,researches on effects of different mineral admixtures on dissolution performance of cement based materials were carried on,using EDTA measuring calcium ion concentration,water satured-dry weighing method,SEM and EDS to measure calcium ion dissolution,porosity,micro morphology and Ca/Si of composite paste mixed with different mineral admixtures in dissolution process,effects of different mineral admixtures on dissolution performance of cement based materials in pure water corrosion condition were obtained.Test results show that fly ash and slag can improve corrosion resistance of cement paste to a certain extent,however the corrosion resistance of composite paste mixed with slag is better than that of paste mixed with fly ash.(2)In 6M ammonium chloride accelerated corrosion condition,calcium leaching tests of slag-cement composite paste and 20%fly ash-cement composite paste column specimens mixed with different content of slag were carried on,through tests on corrosion depth,porosity,Ca/Si,micro morphology and XRD,the results show that the dissolution performance of fly ash-cement composite paste obviously improves with slag mixed in it.(3)One dimensional diffusion model of calcium dissolution of cement based materials in pure water corrosion condition was established,and taking account of effect of mineral admixtures on initial parameters of cement based materials,the dissolution process of thin slices in soft water corrosion condition and column specimens in 6M ammonium chloride corrosion condition was simulated by adjusting parameters of calcium leaching model,the calculation results of simulation were compared with those of tests,and the results show that the testing results of specimens agree with the calculation results of model simulation well in two corrosion conditions,therefore,the model can be used to predicate change rules of calcium leaching of cement based materials in pure water corrosion condition. |
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