Maximizing Nano-Silica Efficiency in Laboratory-Simulated Recycled Concrete Aggregate via Prior Accelerated Carbonation: An Effective Strategy to Up-Cycle Construction Wastes

Cheng-Gong Lu; Xiu-Cheng Zhang; Xue-Fei Chen

doi:10.3390/molecules29245995

Maximizing Nano-Silica Efficiency in Laboratory-Simulated Recycled Concrete Aggregate via Prior Accelerated Carbonation: An Effective Strategy to Up-Cycle Construction Wastes

Molecules. 2024 Dec 19;29(24):5995. doi: 10.3390/molecules29245995.

Authors

Cheng-Gong Lu¹, Xiu-Cheng Zhang^{2

3}, Xue-Fei Chen^{2

3}

Affiliations

¹ School of Civil Engineering and Transportation, Guangzhou University, Guangzhou 510006, China.
² School of Civil Engineering, Putian University, Putian 351100, China.
³ Engineering Research Center of Disaster Prevention and Mitigation of Southeast Coastal Engineering Structures (JDGC03), Fujian Province University, Putian 351100, China.

Abstract

Herein, the study explores a composite modification approach to enhance the use of recycled concrete aggregate (RCA) in sustainable construction by combining accelerated carbonation (AC) and nano-silica immersion (NS). RCA, a major source of construction waste, faces challenges in achieving comparable properties to virgin aggregates. Nano-silica, a potent pozzolan, is added to fill micro-cracks and voids in RCA, improving its bonding and strength. AC pretreatment accelerates RCA's natural carbonation, forming calcium carbonate that strengthens the aggregate and reduces porosity. Due to the complexity of the original RCA, a laboratory-simulated RCA (LS-RCA) is used in this study for the mechanism analysis. Experimental trials employing the composite methodology have exhibited noteworthy enhancements, with the crushing index diminishing by approximately 23% and water absorption rates decreasing by up to 30%. Notably, the modification efficacy is more pronounced when applied to RCA derived from common-strength concrete (w/c of 0.5) as compared to high-strength concrete (w/c of 0.35). This disparity stems from the inherently looser structural framework and greater abundance of detrimental crystal structures in the former, which impede strength. Through a synergistic interaction, the calcium carbonate content undergoes a substantial increase, nearly doubling, while the proportion of calcium hydrate undergoes a concurrent reduction of approximately 30%. Furthermore, the combined modification effect leads to a 15% reduction in total porosity and a constriction of the average pore diameter by roughly 20%, ultimately resulting in pore refinement that equates the performance of samples with a water-to-cement ratio of 0.5 to those with a ratio of 0.35. This remarkable transformation underscores the profound modification potential of the combination approach. This study underscores the efficacy of harnessing accelerated carbonation in conjunction with nano-silica as a strategic approach to optimizing the utilization of RCA in concrete mixes, thereby bolstering their performance metrics and enhancing sustainability.

Keywords: concrete; construction wastes; recycled aggregates.

Grants and funding

This project was funded by the Natural Science Foundation of Fujian under grant number (No. 2023J01999) and the Startup Fund for Advanced Talents of Putian University with grant number (2024051). Additionally, it received support from the Putian University Zixiao Scholars-Young Top Talent Program-2024 with grant number (2024174) and the Mulan River Comprehensive Governance Research Institute of Putian University, specifically for the project titled “Research on the Comprehensive Governance and Efficient Recycling Utilization Model of Resources in the Mulan River Basin under the Guidance of Xi’s Ecological Civilization Thought” (No. ZX2024-12).