Microstructure and Mechanical Properties of Laterite-Based Geopolymer and OPC Concretes: Influence of Type Aggregates

The present study focuses on the production of geopolymer concretes using calcined laterite at 750 °C and an activator solution, with various coarse aggregates such as basalt, granite, and volcanic scoria. The physical and mechanical properties of the resulting concretes were characterized and compared to those of ordinary Portland cement (OPC). The study utilized XRD, FTIR, optical microscopy, and SEM analysis to evaluate the raw materials and concretes. The 28-day flexural and compressive strengths of laterite-based geopolymer concretes range between 13.88 ± 0.69–14.81 ± 0.74 MPa and 102.58 ± 5.13–139.16 ± 7.06 MPa, respectively, which are comparable to OPC-based concretes. The laterite-based geopolymer concretes were denser and exhibited higher water absorption and porosity values. SEM analysis revealed that the concretes made with volcanic scoria aggregates exhibited a more compact and dense microstructure due to additional geopolymerisation reactions and the formation of an aluminosilicate gel. Overall, laterite-based geopolymer concretes have promising properties for engineering applications.