Eco-friendly metakaolin-basalt geopolymer blocks: A sustainable building material alternative

This study investigates the development and characterization of eco-friendly metakaolin-based geopolymer blocks incorporating basalt rock powder as a silica source. The geopolymer samples were synthesized with varying metakaolin-to-basalt ratios (70:30, 60:40, and 50:50) and characterized using X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). XRF analysis confirmed the high silica (50.70 %) and alumina (40.15 %) content of metakaolin, while basalt exhibited significant iron oxide (8.78 %) and calcium oxide (10.60 %), contributing to improved mechanical properties. Fourier-transform infrared spectroscopy (FTIR) showed progressive polymerization in geopolymer samples with increased MK content, evidenced by shifts in Si-O-Al stretching vibrations. Physical and mechanical tests demonstrated that increasing basalt content led to improved bulk density and compressive strength, with the 50:50 MK-basalt mix achieving the highest values: 2.31 g/cm³ density and 19.6 MPa compressive strength after 28 days. Water absorption decreased with higher basalt content and longer curing, dropping to 8.0 % for the 50:50 mix at 28 days. Scanning electron microscopy (SEM) revealed that the 60:40 mix achieved the most uniform and densely packed microstructure after 28 days, balancing N-A-S-H gel formation and filler efficiency. Overall, the 60:40 blend offers an optimal balance of durability, strength, and microstructural integrity for geopolymer applications. These results highlight the potential of metakaolin-basalt geopolymer blocks as sustainable construction materials with enhanced durability and reduced environmental impact.