Evaluation of the Mechanical Properties of Adobe with the Addition of Rice Husk Ash and Opuntia Ficus-Indica

Raw Earth continues to be a widely used material in rural construction due to its accessibility and low cost; however, Adobe has significant limitations, such as its low mechanical strength and high vulnerability to moisture, which negatively affect its durability and structural safety. In view of this problem, this research aimed to evaluate the effect of incorporating Rice Husk Ash (RHA) and Prickly Pear Juice (Opuntia ficus-indica, PPJ) on the mechanical, physical, and thermal properties of Adobe, with a view to developing a more sustainable and environmentally friendly alternative. To this end, soil extracted from the Cullpa Alta quarry, located in the district of El Tambo, was used and cl assified according to the SUCS system. As for the additives, RHA was obtained through a process of controlled calcination and subsequent sieving of rice husks, while PPJ was prepared from the collection, washing, cleaning, and blending of prickly pear cactus pads. Next, six dosage levels were tested for both additives (RHA: 0%, 2%, 4%, 6%, 8% and 10%; PPJ: 0%, 10%, 11.5%, 13%, 14.5% and 16%), resulting in 210 samples that were subjected to compressive strength, tensile strength and flexural strength tests, as well as tests on adobe walls, water absorption and thermal conductivity. As a result, the combination of 6% RHA with 13% PPJ proved to be the most effective, achieving increases of 65.85% in compression, 294.37% in traction, 98.73% in flexion, and 159% in walls, as well as reductions of 47.46% in water absorption and 43.44% in thermal conductivity. Finally, an ANOVA analysis verified that these improvements were statistically significant (p < 0.05), demonstrating that the incorporation of these natural additives allows for a comprehensive improvement of traditional Adobe, positioning this alternative as a viable, durable, and environmentally friendly construction solution.