Performance enhancement of recycled concrete through carbonation during ready-mix and curing

Incorporating COQ into the concrete mixing process is an effective method of carbon sequestration, though fewer studies have applied this technique to recycled aggregate concrete (RAC). This study explores the development of carbonation ready-mix recycled aggregate concrete (CRRC) through the incorporation of CO2 during the mixing process to enhance the properties. Various COQ dosages were tested to evaluate their effects on the compressive strength and uniaxial stress-strain behavior of CRRC. For comparative purposes, carbonation ready-mix mortar (CRM) was also produced using a similar mix design without recycled aggregate. The physical and mechanical properties of both CRM and CRRC were analyzed to assess the influence of COQ dosage and recycled aggregates. The results showed a 30.99 % reduction in CRM fluidity with increasing COQ doses, while mechanical properties improved by 43.62% compared to the control group. CRRC exhibited a similar trend in compressive strength improvement, with a more pronounced effect than CRM, resulting in a 93.8% increase at the 0.3% COQ dose. Uniaxial stress-strain tests indicated that the peak stress improvement at the 0.6% CO2 dose was comparable to that at 0.3 % dose. Additionally, peak strain and elastic modulus were both enhanced, with maximum increases of 41.6 % and 47.0%, respectively. These findings highlight the potential of RAC to efficiently sequester COQ during the mixing stage, leading to significant improvements in early strength and contributing to sustainability in concrete production.