Experimental And Numerical Study Of Accelerated Carbonation In Cement Brick And Tile

Carbonation is a common phenomenon in cement-based materials. It will resultin decreasing of concrete pore solution pH value and cause corrosion of steelreinforcement, the influence on the reinforced concrete structure has adverse effecton the durability of reinforced concrete structures. But on the other hand, aftercarbonation physical and chemical properties of the materials will change and alsohave beneficial effects, mainly because the precipitation of calcium carbonate in thepore structure which may lead to compactness enhancement, the improvement ofcompressive strength and anti-permeability performance, absorbing a lot ofgreenhouse gas carbon dioxide at the same time. Wall materials in our countryaccounts for about70%of all building materials, if we apply acceleratedcarbonation in improving the performance of cement building materials such ascement tile, cement recycled brick, autoclaved aerated concrete block and providean effective way to recycle carbon dioxide, it is of great significance for China’sdevelopment to promote low-carbon economy.This thesis summarize the process and influencing factors of naturecarbonation and analyze the core changes in accelerated carbonation brought byhigh pressure and temperature. Then the working pressure, temperature, andcarbonation time are chose as the control factors of the following experimentalwork. The accelerated carbonation test of cement tile, cement brick and aeratedbrick focus on low pressure, supercritical carbonation test of three kinds of blockfocus on cement paste, cement mortar and concrete. Low pressure acceleratedcarbonation experiments aim to determine minimum reaction conditions of eachblock when complete carbonation is achieved. The various degree of the ability toabsorb carbon dioxide of different materials is analyzed. Supercritical carbonationexperiment mainly studied the reaction conditions and material compositioninfluence on carbonation degree, carbonation depth after carbonation and rule of theabsorbing carbon dioxide weight of each block are also analyzed.Accelerated carbonation test results are analyzed by new numerical model forsupercritical carbonation of our research group under different environmentconditions of carbonation process. Different material parameter and the actualenvironment pressure and environment temperature curve are input into the model,and the influence of experiment process of pressure unloading to the finalcarbonation depth is also taken into account. Carbonation depth from simulationresults and experimental results are compared to verify the applicability of the newmodel and the material parameters. After that, to determine the influence of the parameter selection of materials, initial intrinsic permeability, initial porosity initialliquid saturation, environmental pressure and environmental temperature influenceare analyzed using the numerical simulation results. Carbonation depth predictionformulas for cement mortar, cement paste and cement tile under acceleratedcarbonation are put forward by fitting the numerical results, carbonationcoefficients for environment pressure and temperature are determined.