Wei Da, Zhu Pinghua, Gao Shan, Yan Xiancui, Liu Hui, Fan Haifeng
Department of Civil Engineering, Changzhou University, 21 Gehu Middle Road, Wujin District, Changzhou 213164, China.
School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China.
Materials (Basel). 2022 Sep 5;15(17):6153. doi: 10.3390/ma15176153.
To promote the in-situ and structural application of waste concrete in cold regions, the sustainable application potential of waste concrete in a freeze-thaw (F-T) environment was comprehensively evaluated from three aspects of performance, environmental load, and economic benefit. The recycled aggregate concrete (RAC) was produced by recycled coarse aggregate (RCA), which was obtained from the crushing of natural aggregate concrete (NAC) after every F-T 150 cycles until F-T failure. The effects of F-T damage of parent concrete on the physical properties of RCA and mechanical and frost resistance of RAC under 35% flexural stress were studied. Besides, the sustainability of NAC and RAC was compared and analyzed by emergy theory. The results suggested that the physical properties of RCA deteriorated gradually with the accumulation of F-T damage to parent concrete. The RCA obtained from parent concrete that suffered F-T damage could be used as coarse aggregate for structural concrete when F-T damage is smaller than 0.367. The F-T damage of parent concrete had an adverse effect on the mechanical properties and frost resistance of RAC. The frost resistance of RAC obtained from parent concrete with larger F-T damage was worse. The RAC prepared from parent concrete without F-T failure can serve 50 years in cold regions, while that with F-T failure can only serve 30 years. The F-T damage microelements were dispersed in the adhesive mortar of RCA and transferred to RAC, resulting in the reduction of the mechanical properties and frost resistance of RAC. Emergy analysis showed that the reuse of waste concrete after F-T failure required higher economic input, higher environment load, lower output efficiency, and sustainability. The performance, environmental load and economic benefit of RAC prepared by using waste concrete after F-T failure were inferior to that of waste concrete without F-T failure. Waste concrete after F-T failure is not recommended to be used as coarse aggregate for structural concrete.
为促进废弃混凝土在寒冷地区的原位及结构应用，从性能、环境负荷和经济效益三个方面综合评估了废弃混凝土在冻融（F-T）环境下的可持续应用潜力。再生骨料混凝土（RAC）由再生粗骨料（RCA）制成，RCA是通过对天然骨料混凝土（NAC）进行每150次冻融循环直至冻融破坏后破碎得到的。研究了母体混凝土的冻融损伤对RCA物理性能以及35%弯曲应力下RAC力学性能和抗冻性的影响。此外，运用能值理论对NAC和RAC的可持续性进行了比较分析。结果表明，随着母体混凝土冻融损伤的积累，RCA的物理性能逐渐恶化。当冻融损伤小于0.367时，受冻融损伤的母体混凝土得到的RCA可作为结构混凝土的粗骨料。母体混凝土的冻融损伤对RAC的力学性能和抗冻性有不利影响。冻融损伤较大的母体混凝土得到的RAC抗冻性较差。由未发生冻融破坏的母体混凝土制备的RAC在寒冷地区可服役50年，而发生冻融破坏的RAC只能服役30年。冻融损伤微量元素分散在RCA的胶结砂浆中并转移到RAC中，导致RAC力学性能和抗冻性降低。能值分析表明，冻融破坏后的废弃混凝土再利用需要更高的经济投入、更高的环境负荷、更低的产出效率和可持续性。冻融破坏后使用废弃混凝土制备的RAC的性能、环境负荷和经济效益均低于未发生冻融破坏的废弃混凝土。不建议将冻融破坏后的废弃混凝土用作结构混凝土的粗骨料。
