Alkali-activated limestone powder and groundnut shell ash based geopolymer for stabilizing earth blocks

Utilizing appropriate waste materials as substitutes for cement or river sand offers a feasible and practical strategy for addressing the shortage of construction materials. SriLanka’s construction industry faces a growing demand for sand, leading to environmental concerns and potential scarcity. This research investigates geopolymer earth blocks, a promising alternative utilizing locally available lateritic soil and waste products like limestone powder and groundnut shell ash. The optimal combination of these precursors for strength, water absorption, and durability while minimizing environmental impact and production costs was explored. The optimal results were obtained when a geopolymer mortar mixture of 50 g of limestone powder, 50 g of groundnut shell ash, and 35 g of caustic soda was combined with 833 g of lateritic soil. A specific mix exhibited a 16% increase in water absorption compared to the control mortar but maintained comparable compressive strength (15% increase for both dry and wet). Initial sorptivity increased by 59%, while subsequent sorptivity decreased by 20%. Cost, CO₂ emission, and embodied energy per unit strength significantly decreased by 20.1%, 44.8%, and 55.8%, respectively. The results suggest that the geopolymer mortar has the potential to satisfy the strength criteria specified in the regional regulations for non-load-bearing masonry, provided that they are assembled in a particular manner. The study’s findings further illustrate that the utilization of geopolymer technology has the potential to significantly decrease energy requirements and carbon dioxide emissions linked to the production of mortar. The findings demonstrate that geopolymer earth blocks offer a sustainable solution with comparable strength and acceptable water absorption while significantly reducing embodied energy and CO₂ emissions compared to traditional cement-based blocks. However, further research is needed to address durability concerns under various environmental conditions.