Carbonation resistance and prediction model of mineral admixture concrete
Through rapid carbonation test,combined with SEM microscopic morphology observation and EDS chemical composition analysis,the influence of fly ash and slag on the carbonation resistance of concrete was analyzed.The influence mechanism of mineral admixtures on concrete was discussed.Based on the exponential function,the prediction model of carbonation depth of mineral admix-ture concrete was established.The results show that the strength and carbonation resistance of concrete are reduced by adding mineral ad-mixtures.Under the condition that the total content is the same,the influence of single fly ash on concrete performance is greater than that of mixed fly ash and slag.When the content of fly ash exceeds 40%,the carbonation depth of concrete increases rapidly.The carbon-ation depth of the 60%fly ash group alone at 56 days has reached 18.5 mm,while the carbonation depth of the 60%fly ash and slag group at 56 days is only 6.5 mm.The results of SEM-EDS analysis show that the microstructure of the paste sample is relatively dense when the mineral admixture content is small.When the content of mineral admixtures exceeds 40%,the microstructure of concrete is loose,and pores and defects increase.SEM-EDS analysis corroborates the test results of concrete mechanical properties and carbonation resistance.The carbonation depth model curve of mineral admixture concrete established is in good agreement with the test results,and the fitting correlation coefficient is above 0.89.
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