The Compressive Strength Development of Alkali Activated Fly Ash/Slag Concretes with Different Alkali Activator Ratios

摘要

Recently, geopolymer oralkali-activated concrete takes great attention due to low carbon footprintsince fly ash and ground granulated blast furnace slag (industrial by-productmaterials) has been utilized as binder materials in the alkali-activatedconcrete. In this research, the compressive strength (CS) development of thealkali-activated fly ash/slag (AAFAS) concrete was investigated in an ambientenvironment at 7., 14., 28., and 56. days using alkali activator (sodiumsilicate to sodium hydroxide) ratios of 1, 1.5, 2, and 2.5 with 6M SH (low)concentration. In addition, the effect of delayed oven-curing condition wasalso studied at 56.day. The results indicated that for theambient-cured specimens with 6M SH concentration, the maximum and minimum CSwere reached in the AAFSS concrete with alkali activator (SS/SH) ratios of 2and 1, respectively. The AAFAS concrete with an alkali activator ratio of 2.5showed the lowest CS enhancement after 7.day and 14.day, while the AAFASspecimens with an alkali activator ratio of 1.5 performed the least CSimprovement at 28.day in the ambient environment. Meanwhile, the highest CSenhancement was observed in the specimens with an alkali activator ratio of 2for all ages. Due to the delayed oven-curing, theleast and the highest CS enhancements were observed in the AAFAS specimens withalkali activator ratios of 2 and 1.5, respectively. The results pointed outthat AAFAS concrete with a higher alkali activator ratio (≥2) should be usedfor structural applications in the ambient environment.