Efeito dos componentes da madeira e bambu na hidratação do cimento

Abstract

The development and application of cement-wood composites has been increasing in recente decades. The interest in this material is due to its advantages over conventional materials, as weel as the global trend in the use of bioagregates. The biggest benefits in using this type of aggregate are the reduction in density and cost of the final product. Despite the benefits, there are some challenges in the production of cement-based products with bio-aggregates. Most of the materials used for this purpose ore derived from wood. These materials have a large amount of carbohydrates (sugars) in their composition, which alter inhibit the hydration of the cement affecting it resistance. This work aims to deepen the understanding of how wood and its components affect the hydration of cement-based matrices. Theree plant species were studied, Pinus taeda from a population with more than 28 years of planting, Bambusa vulgaris over three years and Cereus jamacaru. After grinding in a hammer mil and granulommetric separation with 60 mesh retention, part of the lignocellulosic material of each espécies went through three stages of washing with deionized water, in a hot plate at 80°C for 1 hour each, to remove the water-soluble extracts. After determining absorption, apparent density and moisture of each ground lignocellulosic material, drying in na oven was carried out for 48 h at 103°C. Then, chemical characterization was performed to quantify the levels of celulose, hemicellulose and lignina extracts of each species. After molding with the cement and water in a proportion of 33% of particle in relation to the cemnt mass, part of the mixture was coated in the calorimetry analysis to quantify the heat flow. The hydration of mixtures coated on plastic films was interrupted with acetone at diferente ages, to perform the thermogravimetric analysis (TGA). 10 mg of cemnt mixture was used with each lignocellulosic material, in na alumina crucible, with a flow of 50 ml/min of nitrogen and a heating rate of 10°C per minute, until reaching a temperature of 900°C. Calorimetry analyses was also performed to mix the componentes: Linin, pectin, cellulose and glucose in proportions of 1%, 2% and 4% in relation to the cement mass. As a result, Bambusa vulgaris and Pinus taeda showed similar chemical composition. Higher extractive contente was quantified for Cereus jamacaru. The glucose and pectin componentes showed greater inhibition in hydration. The Cereus jamacaru particles interfered more negatively in the cement hydration than the Bambusa vulgaris and Pinus taeda particles, making it possible to conclude that the extractives showed greater inhibition in the cement hydration, due to the correlation of the results obtained for the mixtures of lignocellulosic particles and the results of mixtures with the componentes.