Recycled glass concrete with cementitious materials: Study of mechanical prediction model and dry shrinkage mechanism

Abstract

Recycled Glass Concrete (RGC) exhibits low mechanical strength due to the loose structure of its interfacial transition zone. Adding supplementary cementitious materials is an effective approach to address the issues of low mechanical performance and durability in RGC. In order to improve the performance of recycled glass concrete, three series of tests were prepared for mechanical testing, drying shrinkage testing and microstructure analysis: single-doped limestone powder (RGC-L), single-doped metakaolin (RGC-M), and limestone-metakaolin mix (RGC-LM). The mechanical results demonstrate that RGC, with the addition of 5 % limestone powder and 5 % metakaolin, exhibits optimal strength improvement. Specifically, compressive strength increased by 23.3 %, splitting tensile strength by 38.1 %, and flexural strength by 7.3 %. Additionally, a mechanical prediction model for RGC was proposed, yielding relational equations for splitting tensile strength (ft), flexural strength (fr), and compressive strength (fc): ft=0.14fc0.93,fr=0.72fc0.56. The drying shrinkage results indicate that RGC containing 10 % limestone powder and 20 % metakaolin exhibits the best performance, with a 32.5 % reduction in shrinkage rate. Microstructural analysis revealed that the reaction between Al₂O₃ in metakaolin and limestone powder produces CO₃-AFm, which results in a denser structure in the interfacial transition zone of the recycled glass concrete. Ultimately, this study elucidates the micro-mechanisms and drying shrinkage mechanisms of limestone powder and metakaolin in RGC, offering a promising approach for the effective utilization of construction waste.