Performance Evaluation of Groundnut Shell Ash-Modified Calcined Clay Geopolymers for Construction Applications

The environmental impacts of Portland cement production, notably high carbon dioxide emissions and energy consumption, have accelerated the development of sustainable alternative binders for construction purposes. Geopolymers produced from aluminosilicate-rich materials present a viable low-carbon alternative. This study examined the influence of groundnut shell ash (GNA) on the performance of calcined clay (CC) geopolymer pastes and their application for building purposes. Groundnut shells sourced locally were thermally treated at 800 °C, and characterized using X-ray fluorescence (XRF), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray diffraction (XRD). Geopolymer pastes were produced by activating CC blended with 5-20 wt% GNA using sodium silicate solution only, followed by phase and properties evaluation. Based on 28-day compressive strength, the optimal CC/GNA paste was further modified with quarry dust to produce geopolymer mortars. A control geopolymer (RG) consisting of 100% CC activated with 8 M NaOH/Na₂SiO₃ was also prepared. All samples were cured at room temperature for 7 and 28 days. The results showed that the compressive strength of GNA geopolymer pastes and mortars at 28 days ranged from 23.8±0.3 to 63.5±0.1 MPa, and porosity values from 12.9 to 20.6%, outperforming the control geopolymer (18.1 ± 0.3 MPa; 49.5%). The results demonstrated that GNA enhances densification and strength development, supporting its effective use as a supplementary precursor in calcined clay geopolymers for sustainable construction applications and contributed new insights into the utilization of agricultural waste in geopolymer technology.