A Cost-Effective Slag-based Mix Activated with Soda Ash and Hydrated Lime: A Pilot Study

Abstract

This study investigates the cost-effective binder material of silica fume blended slag mix using industry grade soda ash and hydrated lime as solid activators. The study followed a "just add water" methodology, observing paste rheology and strength development. Microstructural analysis and TGA-DTA studies were conducted to validate the results. A side-by-side comparison was conducted with other mixing procedures. The study found that using pre-mixed analytical grade Na2CO3 in water can cost up to 60% more than using a mixture activated by NaOH pellets. Using industrial-grade chemicals could save 94.5 percent of the budget. For a 10% SF addition and a 10% targeted NaOH content at a w/s ratio of 0.45, the mixes showed the highest strength development and commendable rheology. The mix demonstrated 35.1 MPa after 28 days and 41.33 MPa after 120 days, making it suitable for use as a structural material. The presence of magnesian calcite, magnesite, and hydrotalcite was detected in the XRD analyses. SEM images showed a denser microstructure developed at 28 days. The TG-DT analysis provided insights into phase transitions and bound water associated with hydration products. The higher strength was attributed to calcite transitioning into magnesian calcite and portlandite supplanting CNASH and CSH