THE EFFECTS OF RAPID CARBONIC ACID ON THE STRUCTURE OF THE MICROSTRUCTURE OF CALCIUM SILICATE

A possible method for carbon capture and storage is mineral carbonation of alkaline solid waste, such as used cement paste. By reusing the solid waste, environmental contamination may be decreased. One of the most common mineral phases that may be carbonated is calcium silicate hydrate (C-S-H). In this research, C-S-H with a C/S ratio of 1.50 was synthesized, and the effects of rapid carbonation on microstructure were examined. The Rietveld refineness (QXRD) was used to describe the carbonation products, while nuclear magnetic resonance, scanning electron microscopy, and nitrogen physisorption were each used to examine the microstructure. The findings show that carbonation causes the development of three distinct polymorphs of calcium carbonate as well as silica gel. Aragonite and vaterite have very low decomposition temperatures, whereas well-crystallized calcite decomposes at a greater temperature. Calcium carbonate starts to break down about 300 °C. Due to the stack of thick calcium carbonate, the average pore width drops from 10.33 nm to 6.69 nm, and the specific surface area decreases from 85.6 m₂/g to 67.7 m2/g. In the interlayer of C-S-H, the Ca-O decalcifies, and the remaining silica tetrahedron protonates or connects with other silica tetrahedrons to create Q₃ or Q₄ with a higher degree of polymerization.