Avaliação das condições de cura sobre a resistência à compressão e a microestrutura de argamassa álcali-ativada à base de cinza volante e escória de aciaria

Abstract

Ordinary Portland cement is a widely consumed product in the civil construction sector around the world, however, its production involves the generation of large raw materials and fuels, in addition to high emissions of carbon dioxide in the atmosphere. In view of this, the search for unconventional cements has emerged as a possibility for alternative mortars and concretes that cause less environmental impact. In this context, alkali-activated cements received attention and interest from researchers as an alternative to reduce the negative effects of the cement industry. Thus, the present study aims to evaluate the effect of curing conditions on the mechanical strength of alkali-activated mortars. The mortars were produced from the mixture of precursors composed of fly ash and Basic Oxygen Furnace (BOF) steelworks slag interacting with alkaline activators composed of sodium hydroxide and sodium silicate. As curing conditions, temperature variation (room temperature and 50°C), atmospheric exposure (exposed or isolated from contact with air) and humidity (dry or submerged in water). An experimental approach used was based on the experience of mechanical and microstructural properties. Through the surface resistance test, it was observed that the mortar exposed to thermal curing at 50°C and the basic teaching of contact with atmospheric air presented the best resistance results, 46.05 MPa after 28 days. While the initial curing condition at 50°C and subsequent immersion in water influenced the ability to gain resistance to resistance and caused the loss of resistance at more advanced ages. The microstructural analysis carried out by scanning electron microscopy - SEM test showed that this condition aggravated voids in the mortar microstructure.