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In order to reduce the high dependence on cement in the concrete preparation process, based on the Guangxi Lianhe Expressway Project, Micro-CaCO 3 and fly ash were selected for use as the composite admixtures to study the effects of their application on the concrete chemical properties, appearance quality and carbon emission in the life stage, and the SEM test was utilized to observe the microstructure of the corresponding mortar and to reveal its intrinsic mechanism. The research results show that Micro-CaCO 3 composite fly ash admixture can improve the flowability and early strength of concrete. For low-strength concrete, it can reach standard strength in about 7 days. Meanwhile, concrete with an appropriate amount of composite admixture can enhance its resistance to elastic deformation. SEM images indicate that the incorporation of Micro-CaCO 3 has a better filling and compacting effect on the internal pores of concrete. However, the dosage of Micro-CaCO 3 to replace the equivalent amount of cement should be controlled between 10% and 20%, while excessive dosage will easily affect the hydration and consolidation effect between cement and fly ash, which can reduce the carbon emission ratio of concrete in the stages of materialization, transportation, and construction by about 9%–18%.
Han et al. (Fri,) studied this question.