Investigation of the bond strength and microstructure of the interfacial transition zone between cement paste and aggregate modified by Bayer red mud

In this study, a method is proposed for modifying aggregate with Bayer red mud (RM), and the bond strength and microstructure of the interfacial transition zone (ITZ) in the concrete prepared using the modified aggregate is determined. Compared to concrete prepared using natural basalt aggregate, concrete prepared with RM-modified basalt aggregate aged for 7 and 28 days had a 25.08 % and 21.75 %, respectively, higher compressive strength and a 39.53 % and 15.30 %, respectively, flexural strength. Compared to concrete prepared using natural limestone aggregate, the compressive and flexural strengths of concrete prepared with RM-modified limestone aggregate increased by over 10.00 % and 20 % respectively, after aging of both 7 and 28 days. The RM had a higher wettability to cement paste than basalt and limestone, implying that cement paste on the surface of RM-modified aggregate had a correspondingly stronger microflow and filling capacity. In addition, concrete prepared with the RM-modified aggregate had a low voidage, a compact ITZ structure and strong interfacial adhesion, resulting in considerably enhanced mechanical properties. This study provides novel applications for RM that can be widely used in building materials and waste reduction and a new method for improving the mechanical properties of concrete.

Automated summary

This study proposes a method for modifying aggregate with Bayer red mud and determines the bond strength and microstructure of the interfacial transition zone in the concrete prepared using the modified aggregate. The results show that concrete prepared with RM-modified aggregate has significantly higher compressive and flexural strengths, stronger microflow and filling capacity, compact structure, and strong interfacial adhesion compared to concrete prepared with natural aggregates. This study provides a novel application for RM in building materials and waste reduction, as well as a new method for improving the mechanical properties of concrete.