Effects of Superplasticizer dosage and Molarity of Alkaline solution on Workability and Compressive Strength of Self-Compacting Geopolymer Concrete

The research investigates the effects of super plasticizer and molarity of sodium hydroxide solution on the workability and compressive strength of self compacting geopolymer concrete (SCGC). SCGC is an improved way of concreting execution that does not require compaction and is made by complete elimination of ordinary Portland cement content. The parameters studied were superplasticizer (SP) dosage and molarity of NaOH solution. SCGC were synthesized from low calcium fly ash, activated by combinations of sodium hydroxide and sodium silicate solutions, and by incorporation of superplasticizer for self compactability. The SP dosage were 3%, 4%, 5%, 6% and 7% and the different molarity of NaOH solution were 8M, 10M, 12M and 14M. The effects of SP dosage and molarity of NaOH solution on fresh properties such as filling ability, passing ability and resistance to segregation were assessed. The fresh properties were measured using slump flow, T-50 V-funnel, L-Box and J-ring test methods. The essential workability requirements for self compactability according to European Federation of National Associations Representing Producers and Applicators of Specialist Building Products for Concrete (EFNARC) were satisfied. Results show that the workability and compressive strength improved with the increase in Super plasticizer dosage. An increase in strength and a decrease in workability of these concrete samples was observed with the increase in molarity of NaOH solution from 8M to 14M. However, the strength decreased when the concentration increased from 12M to 14M. The compressive strength of 51.52MPa was obtained for SCGC with SP dosage of 6% and NaOH concentration of 12M.