Efeito da adição de resíduo de casca de café em geopolímeros a base de metacaulim

Abstract

Portland cement is the most used binder in civil construction, with several applications for the production of different composites, whether for structural or finishing purposes. Some authors indicate that this material is one of the most consumed in the world, and that, through its production process, releases a large amount of CO2, responsible for about 9% of the world's emission of this gas. With this, the need arises for the use and study of materials that generate less impact on the environment, as is the case of geopolymers. This material is defined as mineral polymers produced from the alkaline activation of precursors rich in alumina and silica, presenting properties superior to Portland cement in terms of durability, resistance to fire and acids and compressive strenght. Another great advantage is the possibility of using agro-industrial waste for the production of these composites, since these wastes have favorable characteristics for geopolymer synthesis, as is the example of rice husk ash, coffee husks, red mud, blast furnace slag, iron ore dam tailings, among others. Thus, this work aims to present alternative possibilities for the use of sustainable binders, based on the production and analysis of metakaolin-based geopolymers with the addition of coffee husk residue (CC). The results showed that when CC was added to the composites, less durability was found when subjected to sulfuric acid solution (H2SO4) and greater water absorption. In addition, there was a reduction in initial and final setting times (reduction from 4 to 81%) and also greater heat release (increase from 1.7 to 17.3%). Finally, when 2% of ground CC was added to the composites, the flexural tensile strength increased (from 4 to 51%) and the compressive strength did not show perceptible differences. Thus, it was concluded that sustainable binders with the use of agro-industrial waste have great potential to be applied as an alternative material to Portland cement.