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

Year 2019, Volume: 5 Issue: 2, 84 - 89, 30.06.2019

Anıl Niş

Abstract

Recently, geopolymer or
alkali-activated concrete takes great attention due to low carbon footprint
since fly ash and ground granulated blast furnace slag (industrial by-product
materials) has been utilized as binder materials in the alkali-activated
concrete. In this research, the compressive strength (CS) development of the
alkali-activated fly ash/slag (AAFAS) concrete was investigated in an ambient
environment at 7., 14., 28., and 56. days using alkali activator (sodium
silicate 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 was
also studied at 56.day. The results indicated that for the
ambient-cured specimens with 6M SH concentration, the maximum and minimum CS
were reached in the AAFSS concrete with alkali activator (SS/SH) ratios of 2
and 1, respectively. The AAFAS concrete with an alkali activator ratio of 2.5
showed the lowest CS enhancement after 7.day and 14.day, while the AAFAS
specimens with an alkali activator ratio of 1.5 performed the least CS
improvement at 28.day in the ambient environment. Meanwhile, the highest CS
enhancement was observed in the specimens with an alkali activator ratio of 2
for all ages. Due to the delayed oven-curing, the
least and the highest CS enhancements were observed in the AAFAS specimens with
alkali activator ratios of 2 and 1.5, respectively. The results pointed out
that AAFAS concrete with a higher alkali activator ratio (≥2) should be used
for structural applications in the ambient environment.

Keywords

Alkali activated fly ash/slag concrete, alkali activator, delayed oven-curing, sodium silicate to sodium hydroxide ratio

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