Lu Cheng-Gong, Zhang Xiu-Cheng, Chen Xue-Fei
School of Civil Engineering and Transportation, Guangzhou University, Guangzhou 510006, China.
School of Civil Engineering, Putian University, Putian 351100, China.
Molecules. 2024 Dec 19;29(24):5995. doi: 10.3390/molecules29245995.
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.
在此，本研究探索了一种复合改性方法，通过结合加速碳化（AC）和纳米二氧化硅浸渍（NS）来提高再生混凝土骨料（RCA）在可持续建筑中的应用。RCA作为建筑废弃物的主要来源，在实现与原生骨料相当的性能方面面临挑战。纳米二氧化硅是一种有效的火山灰，被添加以填充RCA中的微裂缝和孔隙，改善其粘结性和强度。AC预处理加速了RCA的自然碳化，形成碳酸钙，增强了骨料并降低了孔隙率。由于原始RCA的复杂性，本研究使用实验室模拟的RCA（LS-RCA）进行机理分析。采用复合方法的试验显示出显著的增强效果，压碎指标降低了约23%，吸水率降低了高达30%。值得注意的是，与高强度混凝土（水灰比为0.35）相比，该改性效果应用于普通强度混凝土（水灰比为0.5）衍生的RCA时更为明显。这种差异源于前者固有的结构框架较松散以及有害晶体结构更丰富，从而阻碍了强度。通过协同作用，碳酸钙含量大幅增加，几乎翻倍，而氢氧化钙的比例同时减少了约30%。此外，联合改性效果使总孔隙率降低了15%，平均孔径缩小了约20%，最终导致孔隙细化，使水灰比为0.5的样品性能等同于水灰比为0.35的样品。这一显著转变突出了组合方法的深刻改性潜力。本研究强调了将加速碳化与纳米二氧化硅结合作为一种优化混凝土混合料中RCA利用的战略方法的有效性，从而提高其性能指标并增强可持续性。
