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

Abstract

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.