Influence of aluminum powder content and powder-to-sand ratio on the physical and mechanical properties of aerated lightweight mortar

After the 2015 Nepal earthquake, numerous human casualties resulted from the collapse of substantial brick walls. Concurrently, the proliferation of air pollution attributed to brick kilns has become a pressing concern in urban areas of Nepal. The dual challenge of fortifying building structures and safeguarding the urban environment necessitates innovative solutions. This paper outlines the development of aerated lightweight mortar, incorporating diverse proportions of aluminium powder and various powder-to-sand combinations, aiming to achieve a density below 1000 kg/m³. Three fundamental mixtures, characterized by water-powder ratios (W/P) of 63.3 %, 57.9 %, and 35.3 %, and total powder to sand ratios (P/S) of 0.344, 0.520, and 1.275 (by weight) were employed. The aluminium powder content ranged from 0 % to 1.2 % (by weight of cement). Standard-sized cubes and cylinders were prepared to evaluate the impact of aluminium powder on density, strength, and water absorption. From the test results, the most suitable mixture for aeration proved to be the mortar with a W/P of 35.3 % and P/S of 1.275. This formulation demonstrated a significant 50 % density reduction (<1000 kg/m³) with 0.6 % aluminium powder, accompanied by a 58 % decrease in 28-day compressive strength, a 52 % drop in modulus of elasticity, and a 44 % reduction in splitting tensile strength. The study emphasized the critical role of both aluminium powder content and powder-to-sand ratio in mortar aeration. The developed aerated lightweight mortar not only enhances seismic resilience by reducing building weight but also serves as an eco-friendly alternative to traditional burnt clay bricks, mitigating environmental impact.