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

Abstract

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.