Investigating the impact of carbonation curing concentrations on the mechanical properties and microstructure of recycled concrete

Abstract

This investigation examines the impact of different CO2 curing concentrations on the mechanical and microstructural properties of recycled concrete aggregates, aiming to optimize the carbonation process for enhanced practicality. Utilizing 25 recycled concrete samples, the study varied CO2 concentrations (20 %, 40 %, 50 %, 60 %, and 95 %) and pre-conservation durations (24–120 h), conducting tests for carbon sequestration, compressive strength, and splitting tensile strength to determine the effects on recycled concrete's performance. Key findings reveal a direct correlation between increased CO2 curing concentrations and carbon sequestration levels, with an observed pattern of initial increase followed by a plateau or decrease in sequestration with extended pre-conditioning. Interestingly, while compressive strength generally improved with higher CO2 concentrations, splitting tensile strength showed a decrease, suggesting different impacts of CO2 concentration on various mechanical properties. A notable observation was that at 60 % CO2 concentration, compressive strength was slightly lower (by 2.46 %) compared to the 95 % concentration, yet the splitting tensile strength was 2.84 % higher at 60 %, indicating that a 60 % CO2 curing concentration might offer an optimal balance between economic efficiency and material performance enhancement. This balance suggests significant improvements in resource utilization compared to traditional pure CO2 curing methods. In conclusion, this study provides substantial evidence supporting the optimization of CO2 curing for recycled concrete, advocating for a 60 % concentration as the most effective strategy to enhance both the environmental sustainability and the mechanical performance of recycled aggregates. These insights significantly contribute to advancing low-carbon and sustainable practices within the construction industry.