EXPERIMENTAL INVESTIGATION ON RHEOLOGY AND STRENGTH OF BLAST FURNACE SLAG-FLY ASH BASED ALKALI ACTIVATED BINDER SYSTEMS WITH ADMIXTURES

Abstract

Alkali activated binders (AABs) are a sustainable alternative to Portland cement. They make use of industrial byproducts rich in aluminosilicates to produce hardened binder which contain contains hydrous alkali-aluminosilicates under alkaline condition. The local availability of suitable raw materials (precursors and activators) is a key factor to determine the utilization of alkali-activated binders in any specific location. This study thus focuses on using locally available industrial byproducts to make AABs. Rheology and mechanical properties of Blast furnace slag (BFS)- fly ash binder system activated by sodium hydroxide and sodium silicate is studied considering different control factors including Na2O/b ratio, BFS/binder and ⁄ ratio. Na2O/b ratio and ⁄ ratio are optimized considering the rheology of the alkali activated paste (AAP). The value of BFS/b ratio is then optimized considering both rheology and mechanical behaviour of AAB system. Alkali activated materials exhibit poor workability in mixing because of high viscosity of the paste and fast setting. This is great disadvantage considering the placing and transport of the AABs. In this study, red gypsum and phosphoric acid as additives to enhance the rheological properties ensuring that the resulting binder have strength comparable to the conventional cement mortar