Fresh and Hardened Properties of Fly Ash-Slag Blended Geopolymer Paste and Mortar

Huge amounts of by-products are generated from industrial processes which affect the environment adversely. Production process of conventional cement is energy demanding and it also emits enormous amounts of greenhouse gases. Geopolymers are the new generation green material that has a great potential of replacing the conventional cementitious materials. The fresh and hardened properties of sodium hydroxide activated binary blends of slag and fly ash based geopolymer paste and mortars are reported in this paper. Experimental outcomes on fresh and hardened properties such as normal consistency, flow value, setting time, drying shrinkage, soundness, and compressive strengths of the geopolymer binders are presented. Additionally, the chemical products, bonding and microstructural changes occurring during the setting and hardening course are examined. The experimental outcomes showed that the physical and mechanical properties of the binders are very much akin to that of conventional cement and the same is significantly influenced by the chemical composition of the source materials, concentration of the activator and the processing environment. The consistency and setting times of geopolymers are found to be within the ranges that are prescribed for ordinary Portland cement. Highest compressive strength of around 44 MPa is obtained for slag based geopolymer mortar that is activated using 8 M sodium hydroxide solution. Fly ash and slag geopolymers exhibited excellent stability against expansion and shrinkage. Raw materials are optimized by design of experiment and the fitted model shows a good relation with the experimental data.