Avaliação do uso de ativador sustentável na produção de ligantes álcali-ativados

Abstract

This work evaluates the performance of alkali-activated pastes produced from sustainable precursors and an alternative alkaline activator, aiming to reduce the environmental impact associated with the use of Portland cement and conventional activators. Ladle furnace slag, from the steel industry, and red ceramic waste, from the regional ceramic industry, both processed to a particle size of 150 μm, were used as precursors. As an alternative alkaline activator, a sodium silicate was developed from waste glass, and its performance was compared to that of commercial sodium silicate. The pastes were produced with different proportions between the precursors (70/30, 50/50, and 30/70) and distinct ratios between sodium hydroxide and sodium silicate (40/60 and 60/40), keeping the activator/precursor ratio constant at 0.45. The experimental methodology included the evaluation of fresh state properties, through mini-slump tests (Kantro mini-slump), apparent bulk density, and initial and final setting times, as well as hardened state properties, through the axial compressive strength tests at 7 and 28 days. The results indicated that the pastes activated with commercial sodium silicate presented greater fluidity and compressive strengths varying between approximately 11.87 and 19.36 MPa at 7 days and 19.80 to 29.03 MPa at 28 days. The pastes produced with alternative sodium silicate synthesized at 60 °C presented lower strengths, varying between 1.08 and 2.93 MPa at 7 days and between 1.54 and 4.46 MPa at 28 days. However, increasing the synthesis temperature of the alternative activator to 80 °C resulted in significant strength gains, reaching values close to 6.73 MPa at 7 days and 9.48 MPa at 28 days, evidencing the influence of temperature on the dissolution of silica from the waste glass. Statistical analysis by ANOVA and Tukey’s test confirmed the existence of significant differences between some of the formulations produced with alternative sodium silicate, with no statistically significant differences observed between the pastes activated with commercial sodium silicate. In general, the results demonstrate the potential of using industrial wastes as precursors and alternative alkaline activators in the development of more sustainable alkali-activated materials for civil construction, although the production of the alternative activator still requires adjustments to optimize its performance.