Valorization of rice husk ash and aluminum anodizing sludge as precursors for the synthesis of geopolymers

Abstract The growing demand for economic and sustainable solutions to reduce the environmental impact caused by the consumption of natural resources, and the resulting generation of waste, is the driving force for the search of clean technologies for the manufacture of construction materials using these tailings. Based on this scenario, this study aimed to evaluate the use of rice husk ash and aluminum anodizing sludge as aluminosilicate sources to obtain geopolymers in a mixture of sodium silicate and sodium hydroxide used as alkaline solution. The wastes were prepared by drying, milling, and sieving and cured at 40 °C for 28 days according to a statistical design of mixtures. After curing, the apparent density, shrinkage, tensile strength, and deformation at rupture were determined for four geopolymeric compositions. The ANOVA results showed that the aluminum sludge is the factor that most affects the apparent density, diametral shrinkage, tensile strength, and deformation at rupture. The higher the sodium silicate + sodium hydroxide solution content, the lower the apparent density, shrinkage, and deformation at rupture. Therefore, it is possible to use rice husk ash and aluminum sludge for the manufacture of geopolymers.