Reducing the Carbonation Zone and Steel Corrosion Zone Widths of Recycled Aggregate Concrete by Optimizing Its Mixing Process

The optimization of mixing processes is an effective approach for strengthening the microstructure of the interfacial transition zone (ITZ) in recycled aggregate concrete (RAC). This study used iron oxide to distinguish between residual mortar (RM) and added mortar (AM) in RAC using the normal mixing method (NMM), two-stage mixing method (TSMM), and cement paste encapsulating aggregate method (CPEAM). The CaCO3 contents and pH values of the RM and AM of RAC were investigated separately. The carbonation zone and steel corrosion zone widths of RAC were determined separately based on the CaCO3 contents and pH values, and these widths were compared. The results showed that the TSMM and CPEAM decreased the carbonation and steel corrosion zone widths by improving the microstructures of the ITZs and further decreasing the interfacial effect zones in the RM and AM. In addition, the carbonation and steel corrosion zone widths determined using the RM as samples were higher than those using the AM. Consequently, theoretical models for carbonation and steel corrosion zone widths should reflect the effect of the mixing process. (c) 2021 American Society of Civil Engineers.

Automated summary

The study investigated the optimization of mixing processes to enhance the microstructure of the interfacial transition zone in recycled aggregate concrete. Results showed that certain mixing methods decreased the carbonation and steel corrosion zone widths by improving microstructures and reducing interfacial effect zones. Additionally, the study indicated that carbonation and steel corrosion zone widths were higher when using residual mortar samples compared to added mortar samples.