Ion-doped γ-C2S: Clinker characteristics, carbonation products, and carbonation properties

Abstract

The γ-crystalline form of dicalcium silicate (γ-C₂S) is recognized for its carbonation activity, making it a promising low-carbon binder. This study investigates how impurity ions such as sodium, magnesium, phosphorus, potassium, titanium, nickel, copper, and zinc influence the carbonation characteristics of γ-C₂S. Results on the calcined γ-C₂S powders indicate that Na, P and K doping hinder the β-γ phase transition. Mg, Ti, Ni and Cu doping have little effect on the crystal form of γ-C₂S, but substantially alter their morphology, evident in reduced particle size and increased surface folds. This increases the specific surface area and may facilitate the carbonation reaction. Analysis on carbonation products reveals calcium carbonate content is increasing especially in calcite crystals. The results of carbonation exothermic show the elevation of maximum temperature with the doping level increases. This may be attributable to ion doping promoting the dissociation of Ca²⁺. The increase in degree of carbonation and compressive strength illustrates the beneficial effects of these ionic doping on mechanical and carbonation properties, in particular, Ti ion doping increased 15.6 % and 75.7 % compared to the blank group, respectively. However, Zn doping is contrary to the results of other four ions and its addition has a negative effect on the properties of γ-C₂S. All five ions (Mg, Ti, Ni, Cu, Zn) can be effectively solidified into the calcium carbonate crystals of the carbonation product, which is an important guideline for the future resource utilization of waste and industrialized production. Ion doping provides a reliable reference for future modification of γ-C₂S.