Chiang Mai Journal of Science

In this research, the properties of geopolymer materials containing aggregate from recycled concrete masonry blocks were studied. Metakaolin and waste lignite bottom ash were selected as the geopolymer raw materials. The effects of concrete block waste particle size on the mechanical properties of geopolymer materials were investigated. Concrete block waste from a construction site was crushed and classified into three different size groups smaller than 5 mm, 2 mm, and 1 mm. The Na₂SiO₃/NaOH ratio was fixed at 3:2 with the NaOH concentration at 10M. The compressive strength, density, porosity, and water absorption were determined. The results showed that geopolymer materials containing recycled aggregate with potential applications could be made. The compressive strength of metakaolin-based geopolymer using concrete block waste aggregates with a particle size smaller than 2 mm on the 28^th day was between 39.79-44.75 MPa. SEM analysis results indicated the particle size of the concrete block waste influences the strength development of geopolymer. In which, the aggregates with a particle size smaller than 2 mm can reinforce geopolymer under certain conditions.