Desempenho térmico-acústico-mecânico-durabilidade de compósitos de matriz cimentícia com reduzida massa específica reforçados por casca e palha do arroz

Abstract

Aiming to develop products with high thermal-acoustic performance, composites were produced by introducing waste from the rice industry into a cellular concrete matrix. The purpose of this work was to investigate the effect of adding these byproducts to the matrix. In the total, ten mixtures were analyzed, one of them of cellular concrete, containing only rice husk, and the others, being combinations of the bark and the rice straw in three different lengths and percentages. Thus, the composite with the best performance was studied in the light of addition of saturated fibers. All composites were evaluated for mechanical, acoustic and thermal performance. From the mechanical strength analysis, it was verified that the addition of rice husk reduced the axial compressive strength and increased the tensile strength in the bending. As a result, the substitution of rind plots per rice straw maintained the statistically similar axial compression resistance results up to the 10% volume, but, from 15% straw addition, those results were reduced. Regarding the flexural tensile strength, the addition of rice straw was positive. Considering the acoustic performance, the acoustic absorption presented an increase of approximately 72% with the addition of the rice husk, and 83% with the addition of 15% of straw of 3 cm in length. The results of acoustic insulation were not statistically different; therefore, it was not possible to determine if the vegetal fibers brought positive results to the sound insulation capacity. In terms of thermal performance, it was verified that there is reduction of the conductivity due to the increase of the length of the rice straw. Finally, the durability analysis indicated that the materials have a large amount of the calcium hydroxide, which in turn, in contact with carbon dioxide, forms calcium carbonate, which causes white spots to appear on the surface of the products and accelerates the process of depassivation of metallic reinforcements. The design of the products has shown to be promising due to its satisfactory thermal-acoustic performance, however, it is necessary to carry out more detailed studies on durability and, as an alternative to solve this question, it is suggested to add pozolanas to control the formation of calcium hydroxide.