Wet-Carbonation of RCAs for Improved Carbonation Efficiency and Mechanical Properties of Carbonated RCAs and RCA Concrete

The increasing volume of construction and demolition waste (C&DW) poses significant environmental challenges, making its effective management and treatment crucial. Recycled coarse aggregates (RCA), derived from C&DW, often exhibit weak interfacial transition zones (ITZ), high porosity, and micro-cracks due to residual mortar, limiting their structural performance [1] [2]. This study developed a novel wet carbonation process using glycine acid as an inducer to enhance the mechanical and durability properties of RCA and RCA concrete. Glycine acid, with carboxyl and amino functional groups, formed stable complexes with Ca²⁺ ions, increasing calcium solubility and accelerating carbonation[3]. The process promoted the formation of vaterite, a reactive calcium carbonate polymorph, on RCA surfaces, improving ITZ density and bonding strength with the cement matrix [4, 5]. As a result, abrasion loss decreased to 45.71%, compared to 53.82% for untreated RCA, and California Bearing Ratio (CBR) values increased by 28% at 5 mm penetration, indicating enhanced physical property. Leachate analysis showed carbonated RCA exhibited a reduced pH of 8.47 and lower total dissolved solids (0.263 mS), demonstrating environmental benefits. Mechanical tests of recycled concrete with carbonated RCA revealed strength increases of 13% in compression, 15% in tension, and 12% in flexure. Enhanced surface resistivity and Rapid Chloride Permeability Test (RCPT) results further indicated improved durability and resistance to chemical attacks. These results demonstrate that glycine acid-induced carbonation enhances RCA properties and possibly offers a promising pathway for mitigating construction and demolition waste.