One-part Geopolymer Cements Synthesized by Low Aggresive Hybrid Activators

“One-part” geopolymer is a new class of geopolymer binder that consists of solid aluminosilicate precursors, solid activators and possible admixtures as bagged ready-mixed dry powder similar to ordinary Portland cement (OPC). However, the high cost of commercial anhydrous sodium metasilicate (a commonly-used solid activator) and the companioned environmental issues during its production might limit the in-situ engineering application of one-part geopolymers.

In order to balance the environmental, cost and performance-related requirements, this paper proposes the synthesis of a one-part fly ash/slag geopolymer binder using different hybrid combinations of solid activators including anhydrous sodium metasilicate, sodium carbonate and sodium aluminate with the aim of modifying the properties of the sole sodium metasilicate activated geopolymer. The influences of carbonates and aluminates on the microstructural and engineering properties including setting time, workability and compressive strength of the one-part geopolymers were experimentally assessed. It was found that the moderately gentle hybrid activators could achieve geopolymer binders with superb mechanical properties alike that of mono-silicate-activated one-part geopolymer binders.