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The popularization of recycled concrete (RC) is an important way to achieve efficient resource utilization of construction solid waste (CSW), which can coordinate the sustainable economic development with environmental protection. In this paper, CiteSpace software is used to quantitatively analyze the literatures on RC field, identifying its research hotspots and recent developments. Based on the Web of Science database, we screened published literatures in the field of RC from 2004 to 2023, and obtained 2011 articles. CiteSpace software and knowledge graph technology are adopted to visually analyze the literature information, including the collaborators, keywords and citation status. The results show that, Xiao JZ from Tongji University, Poon CS from Hong Kong Polytechnic University and Tam VWY from University of Western Sydney publish a large number of articles and are frequently cited. It indicates that their researches are widely recognized in academic circles. There is a research team with a large size formed in the Chinese mainland, and the core members include Xiao JZ, Li WG, Chen ZP. At present, the research interest gradually shifts from recycled coarse aggregate to recycled fine aggregate, mainly focusing on microscale research of pore structure and interfacial transition zone. In addition, 8 co-citation clusters of selected references and the potential development trends are detailly analyzed. This study is helpful for researchers to fully understand the current hotspots and future research trends in the field of RC.

The aim of this study was to experimentally investigate the process of chloride binding and its sulfate-induced release in cementitious materials. The cementitious materials were replaced with hardened cement paste particles (HCPs) with water-to-cement ratios (w/c) of 0.35 and 0.45. A long-term immersion experiment of HCPs in 0.1 M sodium chloride solution was performed to investigate its chloride-binding capacity, and then it was immersed in sodium sulfate solutions with concentrations of 0.1 and 0.5 M to explore the release of chloride binding induced by sulfates. Silver nitrate titration and quantitative X-ray diffraction (QXRD) were used to measure the concentration of free chlorides in the solutions and the content of bound chlorides in HCPs, respectively. The results show that there is a higher chloride-binding capacity in HCPs with a w/c ratio of 0.45 compared to 0.35, and the content of chemically bound chlorides is associated with the formation and decomposition of Friedel's and Kuzel's salts in HCPs. The presence of sulfates can easily result in the release of bound chlorides in Friedel's salt, but it cannot cause a complete release of bound chlorides in Kuzel's salt. Physically bound chlorides are more easily released by sulfates than chemically bound chlorides, and a high w/c ratio or sulfate concentration can increase the release rate of bound chlorides in HCPs. [ABSTRACT FROM AUTHOR]