Recycled concrete powder-derived calcium carbonate ceramics by in-situ polymorph transformation-enhanced cold sintering

Abstract

This study presents the preparation of calcium carbonate (CaCO₃) ceramics using vaterite derived from recycled concrete powder (RCP) through a novel in-situ polymorph transformation-enhanced cold sintering process. The resulting chemically bonded CaCO₃ ceramics consists of 100 % calcite and achieve high compressive strength and a relative density of up to 80.5 %. The initial transformation from vaterite to calcite occurs at particle surfaces, decreasing porosity between particles and gradually forming a core-shell structure with a dense outer shell and a porous interior. The fusion of these shells at the contact points of adjacent particles enhances the interparticle chemical bonding. Later polymorph transformations increase pore size and volume and promote particle fusion to form a more homogeneous microstructure. This increases strength by up to 40 % compared to CaCO₃ ceramics produced by conventional cold sintering. The research highlights the potential of utilizing waste concrete for sustainable and high-value CaCO₃ ceramic production.