Cimento álcali ativado à base de cinzas do carvão mineral e escória de aciaria

• Autor(a) principal: Costa, Heloina Nogueira da
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Ceará (UFC)
• Texto Completo: http://www.repositorio.ufc.br/handle/riufc/64793
• topic: Cimento; Pastas; álcali-ativação; Geopolímero; Cinza volante; Cinza pesada; Escória BOF; Escória KR

The availability of steel slag and coal ash in the Metropolitan Region of Fortaleza (RMF) motivates the search for reuse and applications of these materials in new production chains. In this perspective, the possibility of using these by-products as precursors of alkali-activated cements, however, it is necessary to investigate their feasibility of use. Therefore, the present research aims to obtain alkali-activated cements based on fly ash, bottom ash, KR steel slag (Kanbara Reactor) and BOF steel slag (Basic Oxygen Furnace), using sodium silicate and sodium hydroxide solutions. Initially, the chemical, physical and mineralogical characterization of the by-products in powder form was carried out. Then, preliminary studies were carried out producing cement pastes. In another step, the study of properties in the fresh state, of the mechanical behavior and of the microstructural characteristics obtained from binary and unary mixtures was carried out. The main results obtained indicate that bottom ash and steel slag have potential use as precursors for alkali-activated cements, especially when combined with fly ash. It was observed that the pastes obtained from KR slag showed cementing properties and the formation of C-A-S-H gel (hydrated calcium aluminosilicate), although with compressive strengths below 7 MPa. Cement produced with the combination of 75% fly ash and 25% bottom ash showed satisfactory mechanical behavior for structural applications, with a compressive strength, at 28 days, of 47,4 MPa. Its microstructure is formed by N-A-S-H gel (hydrated sodium aluminosilicate). Cement produced with 50% fly ash and 50% BOF slag obtained a compressive strength, at 28 days, of 62,3 MPa, it can also be indicated for structural applications. The incorporation of BOF slag promotes the formation of C-(N)-A-S-H (hydrated calcium-sodium aluminosilicate) and C-A-S-H gels. Finally, cements obtained from the mixture of heavy ash and BOF steel slag showed compressive strengths between 10 MPa and 13 MPa, being indicated for non-structural composites, showed the formation of aluminosilicate gels, mainly on the surfaces of the particles. Therefore, the feasibility of obtaining alkali-activated cements from coal ash and steel slag studied is confirmed.