Dimensional Stability of Ambient-Cured One-Part Geopolymer Concrete Activated by Powdered Sodium Metasilicate: Drying Shrinkage, Restrained Shrinkage and Creep

Dimensional stability is one of the key serviceability criteria for geopolymer concrete, especially when the binder is produced by a one-part route and cured at ambient temperature. This paper evaluates drying shrinkage, restrained shrinkage and compressive creep of one-part geopolymer concrete activated mainly with powdered sodium metasilicate anhydrous. The binder system was based on class F fly ash and ground granulated blast furnace slag (GGBFS), and the assessment focused on the effects of slag content, water-to-precursor ratio and solid activator composition. Five one-part mixtures were compared with an ordinary Portland cement concrete reference. Free shrinkage was monitored for one year together with mass loss and ultrasonic pulse velocity, while restrained shrinkage was measured on slab specimens by a photogrammetry-based procedure. Creep was evaluated under sustained compressive stress applied at 28 days. The slag-dominant mixture showed the highest one-year free shrinkage, reaching 1769 microstrain, whereas mixtures containing 60% fly ash and 40% GGBFS generally remained between 723 and 1091 microstrain. Lowering the water-to-precursor ratio from 0.45 to 0.35 reduced creep strain from about 1706 to 1551 microstrain and decreased the creep coefficient from 2.56 to 1.87. Restrained shrinkage of geopolymer mixtures was markedly lower than that of the Portland cement reference, with optimized mixtures remaining around 255-270 microstrain after one year. The results show that powdered sodium metasilicate can produce dimensionally stable one-part geopolymer concrete when slag content and water dosage are controlled to limit mesopore development, capillary pressure and early-age self-desiccation.

One-part geopolymer concrete, powdered sodium metasilicate, drying shrinkage

Davidovits, J. Geopolymers and geopolymeric materials. Journal of Thermal Analysis, 1991, 37, 1633-1656.

Provis, J.L.; Bernal, S.A. Geopolymers and related alkali-activated materials. Annual Review of Materials Research, 2014, 44, 299-327.

Luukkonen, T.; Abdollahnejad, Z.; Yliniemi, J.; Kinnunen, P.; Illikainen, M. One-part alkali-activated materials: A review. Cement and Concrete Research, 2018, 103, 21-34.

Deb, P.S.; Nath, P.; Sarker, P.K. Drying shrinkage of slag blended fly ash geopolymer concrete cured at room temperature. Procedia Engineering, 2015, 125, 594-600.

Ye, H.; Radlinska, A. Shrinkage mitigation strategies in alkali-activated slag. Cement and Concrete Research, 2017, 101, 131-143.

Ye, H.; Cartwright, C.; Rajabipour, F.; Radlinska, A. Understanding the drying shrinkage performance of alkali-activated slag mortars. Cement and Concrete Composites, 2017, 76, 13-24.

Hojati, M.; Radlinska, A. Shrinkage and strength development of alkali-activated fly ash-slag binary cements. Construction and Building Materials, 2017, 150, 808-816.

Castel, A.; Foster, S.J.; Ng, T.; Sanjayan, J.G.; Gilbert, R.I. Creep and drying shrinkage of a blended slag and low calcium fly ash geopolymer concrete. Materials and Structures, 2016, 49(5), 1619-1628.

Sagoe-Crentsil, K.; Brown, T.; Taylor, A. Drying shrinkage and creep performance of geopolymer concrete. Journal of Sustainable Cement-Based Materials, 2013, 2(1), 35-42.

Gunasekera, C.; Setunge, S.; Law, D.W. Creep and drying shrinkage of different fly-ash-based geopolymers. ACI Materials Journal, 2019, 116(1), 39-49.

Ma, J.; Dehn, F. Shrinkage and creep behavior of an alkali-activated slag concrete. Structural Concrete, 2017, 18(5), 801-810.

Neupane, K.; Hadigheh, S.A. Sodium hydroxide-free geopolymer binder for prestressed concrete applications. Construction and Building Materials, 2021, 293, 123397.