Influence of Alkaline Binders on the Workability and Strength of Self Compacting Geopolymer Concrete

Self-compacting geopolymer concrete (SCGC) has emerged as a promising alternative to traditional concrete due to its environmental benefits. In SCGC, alkaline binders, such as sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃), play a crucial role in influencing both workability and strength. Notably, the ratio of alkaline binders significantly impacts the overall performance of SCGC. This study investigated five SCGC mixes with varying alkaline binder (A/B) ratios ranging from 0.40 to 0.60, incorporating 50% fly ash (FA) and 50% ground granulated blast furnace slag (GGBS). The mixes included 14 M NaOH, a superplasticizer (9 kg/m³), and extra water (54 kg/m³) to evaluate the effect of the A/B ratio on workability and mechanical strength properties. The results revealed that the fresh properties of SCGC with A/B ratios of 0.4, 0.45, and 0.5 complied with EFNARC guidelines, as assessed by the slump flow test, with the lowest T50cm slump flow recorded at 696 mm. The mix with an A/B ratio of 0.5 exhibited the best mechanical performance, achieving a compressive strength (CS) of 38.3 MPa, a splitting tensile strength (STS) of 4.63 MPa, and a flexural strength (FS) of 5.85 MPa. These findings suggest that an SCGC mix with a 0.5 A/B ratio optimizes rheological and mechanical properties at a 14 M NaOH concentration.