Ambient-Cured One-Part Geopolymer Concrete Activated by Powdered Sodium Metasilicate

This paper assesses ambient-cured one-part geopolymer concrete in which powdered sodium metasilicate is used as the principal alkaline activator. The material concept is based on a dry binder system where class F fly ash, ground granulated blast furnace slag (GGBFS) and solid activator are blended before water is added. Such a procedure reduces the dependence on strongly alkaline liquid solutions and brings the mixing sequence closer to ordinary concrete production. Five one-part geopolymer mixtures were examined and compared with an ordinary Portland cement reference in terms of setting behaviour, workability, compressive strength, flexural strength, splitting tensile strength, modulus of elasticity, water absorption, permeable void volume, drying shrinkage, creep, restrained shrinkage and pore-structure features. The 28-day compressive strength of the one-part mixtures ranged from 26.2 to 41.7 MPa, while flexural and splitting tensile strengths were 4.55-6.35 MPa and 3.65-5.05 MPa, respectively. The mixture containing 60% fly ash and 40% GGBFS, activated only with powdered sodium metasilicate anhydrous, provided the most balanced response. Reducing the water-to-precursor ratio to 0.35 improved strength, microstructural compactness and creep resistance, although it shortened the workable period. Compared with the cement reference, several geopolymer mixtures showed higher water absorption and free drying shrinkage; nevertheless, optimized formulations exhibited lower creep and restrained shrinkage. The findings confirm that powdered sodium metasilicate can be an effective single activator for ambient-cured one-part geopolymer concrete when precursor balance and water dosage are controlled together.

One-part geopolymer concrete, powdered sodium metasilicate, ambient curing

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