Análise do comportamento no estado fresco e endurecido de pastas álcali ativadas à base de cinzas de combustão de carvão mineral e de escória de aciaria

Abstract

The most used binder in civil construction is Portland cement, however, this material is a large emitter of carbon dioxide (CO2). For this reason, new materials have been investigated to fully or in part replace the use of this binder. In this scenario, activated alkali cement emerges as an alternative. This material can be obtained from precursors such as fly ash, bottom ash and steel slag. As it is a new type of binder material, this work focuses on analyzing its main characteristics, such as workability, setting time and compressive strength. These properties were analyzed by making simple and binary pastes, using as ativators sodium hydroxide and sodium silicate, divided into three systems, containing pairs of precursors, and in the subsequent performance of tests such as mini slump, Marsh funnel, setting time and compression strength. Through the tests performed it can be observed that the bottom ash, together with the fly ash did not provide an ideal initial setting time for use in civil construction, since, for example, the paste containing 100% bottom ash, in the VP system, did not show a handle signal, the same occurred for the PB system and by adding only 25% of steel slag , in this system, the initial setting time became around 14.4 hours, making the slag function as a handle accelerator. Moreover, in the correct proportion, the steel slag when mixed with the combustion ash of coal, ends up positively influencing the workability and compressive strength, reaching values, at 28 days, such as 38.73 MPa, containing 50% of fly ash and 50% of steel slag. Thus, it can be said that the slag of a ciary contributes significantly when incorporated into pastes based on coal combustion ash.