Produção e caracterização de cinzas pozolânicas a partir da biomassa da casca do coco verde

Abstract

The cement industry is responsible for a large part of greenhouse gas emissions, especially during clinker production. Studies carried out are unanimous in reporting that cement manufacturing is responsible for about 7% of the total CO2 emissions in the world. Based on this fact, there is the continuous expansion of civil construction, with the consumption of nonrenewable inputs, such as those used in concrete production. Due to these factors, the experimental program present in this work aimed to study the feasibility of producing pozzolanic ashes from the burning of green coconut shell biomass. The proposal of this research was due to the fact that Brazil is the fifth largest producer of coconut in the world and faces problems with the disposal of this agro-industrial residue, causing accumulation in landfills. In addition, there are also the environmental impacts caused by the manufacture of Portland cement. The experimental program began with the collection of coconut, followed by drying the raw material, grinding and chemical processing of the green coconut biomass for the production of chemically treated and untreated ash at 600 °C, 700 °C and 800 °C. Ashes were characterized by laser particle size, X-ray fluorescence, X-ray diffraction, electrical conductivity, Chapelle pozzolanic activity index and BET surface area for the analysis of temperatures where the ash showed reactivity. The results showed that the ash without chemical treatment had undesirable alkali metals for their use as pozzolans. On the other hand, the ash produced after the chemical treatment of coconut exhibited a sum of SiO2, Fe2O3 and Al2O3 greater than 50%, in addition to a loss of ignition less than 6%, classifying them as pozzolanic according to NBR 12653 (ABNT, 2014), except by the SO3 content. By analyzing the pozzolanic activity index data measured by electrical conductivity and modified Chapelle, results were obtained up to 0.945 mS/cm and 1263.09 mg Ca(OH)2, respectively. Such values demonstrate that the material has pozzolanic activity, according to the classification by Luxán et al. (1989) and Raverdy et al. (1980). Finally, the results of characterization of the leached ash found that there is the feasibility of green coconut husk ash as a mineral addition to the cementitious paste, since it has chemical composition, loss of ignition and Chapelle pozzolanic activity index that are interesting for the application of this as pozzolan