Avaliação do emprego de lodo de tratamento de esgoto (LTE) e casca de arroz (CA) na produção de cerâmicas vermelhas

Abstract

Rice husk (RH) and sewage sludge (SS) are industrial by-products largely produced daily. The SS is classified as class II-A (not inert) non-hazardous waste. Despite its physical and chemical similarities to the ceramics industry's raw materials, the SS is commonly disposed in landfills. The RH has applications in power generation as a biofuel and agriculture as a fertilizer. Nonetheless, the production of RH exceeds its industrial consumption and, thus, becomes an environmental liability. The valorization of the RH and SS as raw materials for the ceramics industry is one alternative to its' current disposal in landfills. To evaluate the viability of using RH and SS in the ceramics manufacturing process, different mixtures were produced using the vacuum extrusion method. The mixtures had SS incorporated in 0 %, 2 % and 6 % weight ratio and RH incorporated in 0 %, 2 % and 5 % in volume ratio. The extruded specimens formed 30 mm cubic shape blocs. The firing temperature was set to 900 °C for three hours. The heating ratio adopted was 0,85 °C/min to obtain defects-free ceramics. The specimens' linear shrinkage, compressive strength, water absorption, apparent density, efflorescence, and visual defects were evaluated. RH addition decreased linear shrinkage and increased firing shrinkage. Compressive strength was not affected by 2% SS substitution. Although, 6% SS substitution caused the ceramics' compressive strength to decrease or to be less reliable. The tested RH proportions did not affect the ceramics' strength characteristics. The addition of both SS and RH led to an increase in water absorption and a decrease in the apparent density. The samples produced with 6% SS showed clear efflorescence stains. Meanwhile, the 2 % SS samples had similar behavior to the control group. The tests showed that it is possible to produce good quality red ceramics bricks with up to 2% w.r. SS and 5% v.r. RH.