Desenvolvimento de cimentos á base de silicatos utilizando rochas vulcânicas

Abstract

Silicate based cements (SBC) are ceramic materials obtained through the reaction between solid silicon and aluminium-rich materials and a strong alkaline solution. Such SBC are produced at temperatures close to ambient and can present high mechanical strength and chemical and thermal stability, if correctly processed. The solid precursors used in the production of these materials present, in most cases, amorphous structures, which favour their dissolution and general reactivity in alkaline environments. It has been observed that, when predominantly crystalline solid precursors are used, the material’s chemical stability (hydrolytic resistance) is not adequate. In this work, the performance of basaltic rocks with three different particle size distributions was evaluated against sodium silicate solutions with different compositions. It was observed that the conventional processing route and formation kinetic models reported in the literature did not result in chemically stable SBC. Therefore, a simplified kinetic model and a new processing route were set forward to enable the development of chemically stable SBC from crystalline raw materials and sodium silicate. Thus, it could be concluded that chemical stability is not dependent on the nature of the atomic structure of the solid precursors but rather on ideal chemical relationships between equivalent oxides and the removal or complete stabilization of the water remaining in the material’s structure.