Casca de arroz como fonte de sílica para produção de concretos refratários autoescoantes

Abstract

In Brazil, rice is one of the most consumed foods by the population, in addition to being one of the main agricultural crops. The rice husk represents on average 20% by mass of the rice produced and is a renewable source of silica. Silica is a raw material widely used in refractory materials. Obtaining it through a residue from the rice industry associated with the continuous effort of the refractory industry to produce a more sustainable product and apply new technologies, can result in resource savings and improvement in the quality of its products. In this context, the objective of this work was to analyze the effect of using rice husk ash as a partial substitute for microsilica on the mechanical, physical, thermal and microstructural properties of self-flowing refractory castables. The rice husks were washed with acetic acid in an autoclave. Subsequently, they were dried at 105 ° C for 24 hours and calcined at 600 ° C for 4 hours. The ashes of rice husk obtained after calcination were subjected to analysis of particle size distribution, analysis by X-ray fluorescence spectrometry, X-ray diffraction (XRD) and pycnometric density. Refractory castables were produced with the replacement of 0%, 5%, 10% and 15% (by mass) of rice husk ash. After curing, the specimens were demolded, dried in the oven at 110 ° C for 24 hours, sintered at 800 ºC for 5 hours and at 1430 ºC in the tunnel oven for 8 hours. Subsequently, the concretes were subjected to physical, mechanical, chemical and microstructural characterization. Concrete sintered at 800 ° C and 1430 ° C showed greater resistance to thermal shock. The ashes of rice husk and microsilica have very similar chemical compositions, and the size and shape of the ash particles are different. The results of this work contributed to the development of a self-flowing refractory concrete using partially as a raw material, a residue. Refractory concrete with 10% ash from rice husk sintered at 1430 ° C showed better mechanical performance, rupture modulus of 55.10 MPa and compressive strength of 119.62 MPa.