Wu Yang, Bian Xiaoya, Liu Jie, Chi Ruan, Chen Xuyong
School of Civil Engineering and Architecture, Wuhan Institute of Technology, Wuhan 430073, China.
Hubei Provincial Engineering Research Center for Green Civil Engineering Materials and Structures, Wuhan Institute of Technology, Wuhan 430073, China.
Materials (Basel). 2023 Oct 9;16(19):6607. doi: 10.3390/ma16196607.
The proper reutilization of the phosphogypsum (PG) by-product derived from the production of phosphoric acid and recycled concrete aggregate (RCA) from waste concrete in roadbase materials is of great necessity and importance. This investigation tried seeking a new approach to reuse them to high quality, including turning PG into calcinated PG (CPG) via washing and calcination, as well as adopting sodium metasilicate nonahydrate (SMN) to strengthen the roadbase materials of cement-stabilized CPG and RCA. Upon the mix design, with a series of experiments including unconfined compressive strength, the wet-dry cycle, freeze-thaw cycle, and scanning electron microscopy, the comprehensive effects of PG treatment, the CPG to RCA mix ratio, SMN dosage, wet-dry cycle and freeze-thaw cycle on the road performance of roadbase materials were well evaluated, and the traffic bearing capacity and microstructure characteristics were also analyzed. The results demonstrate that the 7 d unconfined compressive strength of CPG/RCA roadbase materials can reach 5.34 MPa as the CPG and SMN dosage are 20% and 11%, respectively, which meets the requirements of an extremely and very heavy traffic grade. After five wet-dry cycles and freeze-thaw cycles, the resistance of the CPG/RCA roadbase materials to moisture and frost was significantly improved as 11% SMN was added. Meanwhile, SMN contributes to the reduction in crack width and densifies the microstructure of CPG/RCA roadbase materials. The research results can be used to provide new guidance for building more durable roadbase materials.
磷酸生产过程中产生的磷石膏（PG）副产品以及废弃混凝土中的再生混凝土骨料（RCA）在道路基层材料中的合理再利用具有极大的必要性和重要性。本研究试图探寻一种将它们再利用为高质量材料的新方法，包括通过水洗和煅烧将PG转化为煅烧磷石膏（CPG），以及采用九水偏硅酸钠（SMN）来增强水泥稳定CPG和RCA的道路基层材料。在配合比设计方面，通过一系列包括无侧限抗压强度、干湿循环、冻融循环和扫描电子显微镜的实验，很好地评估了PG处理、CPG与RCA的混合比例、SMN用量、干湿循环和冻融循环对道路基层材料路用性能的综合影响，同时分析了其交通承载能力和微观结构特征。结果表明，当CPG和SMN用量分别为20%和11%时，CPG/RCA道路基层材料的7天无侧限抗压强度可达5.34MPa，满足特重和极重交通等级的要求。经过五次干湿循环和冻融循环后，添加11%的SMN显著提高了CPG/RCA道路基层材料的抗水和抗冻性能。同时，SMN有助于减小裂缝宽度并使CPG/RCA道路基层材料的微观结构致密化。研究结果可为建造更耐用的道路基层材料提供新的指导。
