Optimizing Precursors and Reagents for the Development of Alkali-Activated Binders in Ambient Curing Conditions

• Main Authors: Dhruv Sood, Khandaker M. Anwar Hossain
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Journal of Composites Science
• Subjects: alkali-activated binders; supplementary cementitious materials (SCMs); powder-based reagents; geopolymers; ambient curing; strength
• Online Access: https://www.mdpi.com/2504-477X/5/2/59

Alkali-activated binders (AABs) are developed through the activation of aluminosilicate-rich materials using alkaline reagents. The characteristics of AABs developed using a novel dry-mixing technique incorporating powder-based reagents/activators are extensively explored. A total of forty-four binder mixes are assessed in terms of their fresh and hardened state properties. The influence of mono/binary/ternary combinations of supplementary cementitious materials (SCMs)/precursors and different types/combinations/dosages of powder-based reagents on the strength and workability properties of different binder mixes are assessed to determine the optimum composition of precursors and the reagents. The binary (55% fly ash class C and 45% ground granulated blast furnace slag) and ternary (25% fly ash class C, 35% fly ash class F and 40% ground granulated blast furnace slag) binders with reagent-2 (calcium hydroxide and sodium sulfate = 2.5:1) exhibited desired workability and 28-day compressive strengths of 56 and 52 MPa, respectively. Microstructural analyses (in terms of SEM/EDS and XRD) revealed the formation of additional calcium aluminosilicate hydrate with sodium or mixed Ca/Na compounds in binary and ternary binders incorporating reagent-2, resulting in higher compressive strength. This research confirms the potential of producing powder-based cement-free green AABs incorporating binary/ternary combinations of SCMs having the desired fresh and hardened state properties under ambient curing conditions.