Carbonation resistance of recycled fine aggregate concrete reinforced by calcium sulfate whiskers

• Published in: Journal of Building Engineering Vol. 92; p. 109476
• Main Authors: Zhong, Chuheng, Chen, Xiaoyu, Mao, Weiqi, Xin, Sijia, Chen, Jinhui, Zhou, Jinzhi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-09-2024
• Subjects: Calcium sulfate whiskers; Carbonation; Carbonation model; Microstructure; Recycled fine aggregate; Recycled fine aggregate; Carbonation; Carbonation model; Microstructure; Calcium sulfate whiskers
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2024.109476

This study investigates mechanical and carbonation resistance tests conducted on Recycled Fine Aggregate Concrete (RFAC) with three different Recycled Fine Aggregate (RFA) replacement rates and four calcium sulfate whisker (CSW) contents, and investigates the effects of RFA replacement rate and CSW content on the mechanical properties of RFAC and the carbonation resistance of RFAC with calcium sulfate whiskers at different ages of carbonation. The microstructure of CSW-modified RFAC was observed and analyzed by SEM electron microscopy to explore further enhancement and toughening mechanisms of CSW in RFAC, as well as the optimal content of CSW in RFAC. In addition, the carbonation depth of recycled concrete with calcium sulfate beard is modeled based on a quadratic fitting formulation. The test results show that the mechanical properties and carbonation resistance of RFAC would decrease with the increase of the RFA replacement rate. Incorporating CSW can effectively improve the mechanical properties and carbonation resistance of RFAC. At 60 % RFA substitution, CSW at 2 % content has the most significant effect on the mechanical properties and carbonation resistance of RFAC. Microscopic analysis shows that CSW has a bridging effect at the micro-cracks in the concrete matrix, preventing the creation and expansion of micro-cracks in the concrete matrix, thus improving RFAC mechanical properties of RFAC and resistance to carbonation. The predicted results of the carbonation depth model which are constructed from the test data coincide with the results. We can use them to predict and analyze the carbonation depth of the carbonation resistance of recycled concrete.
•The addition of calcium sulfate whisker enhances the mechanical properties and carbonation resistance of RFAC.•The enhancement mechanism of RFAC by calcium sulfate whisker was investigated by applying SEM electron microscopy scanning technique.•A prediction model for carbonation depth is proposed.