Effect of mixing method on properties of alkali-activated pastes along With polycarboxylate admixture: a novel hybrid mixing

This paper proposes a novel mixing method for preparing the alkali-activated materials (AAMs) along with polycarboxylate admixture named as “Hybrid-mixing”. A comparative experimental study was conducted on alkali-activated pastes prepared using conventional one-part (1GP), two-part (2GP) and hybrid-mixing (HM) approaches. The effects of the mixing approach on the flowability, compressive strength and total porosity of the AAMs were reported. The precursor used in all the mixes was a blend of 50% low-calcium Class-F fly ash and 50% slag, while the alkali activator used was solid anhydrous sodium metasilicate (Na2SiO3-Anhydrous) powder along with tap water and polycarboxylate admixture. The water-to-binder ratio was fixed at 0.4 for all mixes.
It was found that HM-AAMs achieved a relatively higher flowability (up to 16%) relative to both 1GP- and 2GP-AAMs. Further, the compressive strength of the HM-AAMs was 40% and 20% higher in reference with the 1GP- and 2GP-AAMs, respectively. The total porosity results were in consistence with the compressive strength results at which the HM-AAMs showed a markedly lower total porosity compared to that of 1GP- and 2GP-AAMs.