Avaliação do uso de escória Baosteel Slag Short Flow (BSSF) na produção de cimento supersulfatado

Abstract

The study presents an alternative to traditional Portland cement by exploring the use of supersulfated cement (SSC) incorporating Baosteel Slag Short Flow (BSSF) slag, a material that has been scarcely tested in Brazil. The goal is to develop a construction material that reduces the environmental impact of the cement industry, as Portland cement is one of the main contributors to global CO₂ emissions. In contrast, SSC, which requires little to no clinker, generates lower carbon emissions and demands less energy for production. Composed mainly of ground granulated blast-furnace slag (GGBFS), calcium sulfate, and an alkaline activator (such as calcium hydroxide or sodium carbonate), SSC stands out for its low environmental impact and high resistance to aggressive environments. The general objective of this research is to produce a supersulfated cement using Baosteel Slag Short Flow and evaluate its compressive strength and the formation of cementitious products through microstructural and thermal analyses. The methodology involved preparing SSC pastes with GGBFS and BSSF, varying the BSSF content from 0% to 25%, while maintaining a constant base of calcium sulfate and water. The samples underwent accelerated curing in an oven at 55°C for 24 hours, followed by additional curing at room temperature for testing at 7 and 28 days. Compressive strength tests were conducted, along with scanning electron microscopy (SEM) and thermal analyses, including thermogravimetric analysis (TGA), differential thermal analysis (DTA), and derivative thermogravimetry (DTG). The results indicated that pastes with higher BSSF content, particularly those with 20% (P20) and 25% (P25), exhibited better compressive strength at 28 days. The P20 paste achieved a compressive strength of 5.7 MPa. SEM microstructural analysis at 28 days revealed incomplete hydration, indicating low chemical reactions and limited formation of cementitious products. The microstructure of the P20 paste showed a greater presence of hydrated products such as ettringite and C-S-H, explaining its higher compressive strength results. Thermal analyses revealed endothermic peaks associated with the decomposition of compounds such as C-S-H and ettringite. The temperature range of 120°C to 130°C highlighted the presence of these hydrated products, with higher mass loss observed in P20 and P25 samples, reinforcing the formation of cementitious products. It is concluded that BSSF slag can be used in the formulation of supersulfated cements, showing promising performance, although still inferior to that of Portland cement.