Investigation of carbonation-induced microstructural changes in low-cement concrete using sustainable binders: GGBS and calcium carbonate

Concrete manufacturing makes a major contribution to the world economy, especially the construction industry, but it has a high level of CO₂ emissions, which harm the environment. To address this environmental issue, this paper investigates the possibility of utilizing a natural mineral that consists of iron, silica, and magnesium, and that is referred to as calcium carbonate, to partially substitute cement. This has been neglected material in past studies, even though it can be used to boost the process of hydration, chemical stability, and even be low in solubility in water. The study is exploring the characteristics of calcium carbonate (CaCO₃)-modified concrete, such as its physical, rheological, and microstructural properties. CaCO₃ and ground granulated blast furnace slag were taken as a replacement of 5%, 10%, 15% and 20% of the cement by weight, with a constant water to cement ratio being 0.45, and 50% replacement of cement by ground granulated blast furnace slag (GGBS). The plots of Nyquist and Bode that the microstructural analysis of the changes in the concrete matrix. Non-destructive testing was used to test the performance of the concrete in the long term, quality, homogeneity, and the hardness of the surface. The findings revealed that CaCO₃-modified concrete was better than traditional concrete, especially in its resistance to carbonation. It gave the best result with 15% cement replacement, where compressive strength was 71.1 MPa, split tensile strength was 4.72 MPa, and flexural strength was 5.89 MPa after 90 days. The results indicate that CaCO₃ can be an effective alternative to cement that can be used in the production of concrete.