The potential application of partial activation for synthesizing one-part alkali-activated slag/fly ash precursor: A way for commercializing alkali-activated materials

Abstract

In this paper, a new strategy is applied to synthesize a safe-to-use one-part (OP) alkali-activated binder via controlling the activation rate of blast furnace slag (BFS) and fly ash (FA). The proposed strategy involved creating a reactive powder with a high capacity to interact with water, similar to Portland cement (PC). This was achieved by partially activating BFS/FA in the presence of water, which makes the activated paste in a non-workable form, followed by immediate drying at 80°C for 24 hours and pulverizing to produce one-part (OP) alkali-activated powder. The impacts of sodium hydroxide (NaOH) concentration and water/raw material powder (W/RMP) on the performance of the prepared OP-activated powder and the relevant hardened pastes are addressed. Different contents of hazardous lead glass sludge (LGS) include 5, 10, and 15 wt% were incorporated during the preparation process to evaluate the potential applicability of the synthesized OP-activated powders in the immobilization of hazardous lead (Pb). The obtained results revealed that, regardless of NaOH concentration and W/RMP ratio, all the synthesized OP-activated powders showed a high capability to interact with water, yielding hardened materials with appropriate mechanical properties. However, adjusting NaOH concentration at 10 wt% and W/RMP ratio of 0.1 during the synthesis process has resulted in the formation of OP-activated powders with the highest compressive strength values at all ages. Moreover, this mixture exhibited compressive strength comparable to those of the conventional two-part (TP) alkali-activated binder at the same NaOH concentrations. The proposed strategy presents a high affinity to restrict the free Pb inside the alkali-activated mixtures through its transformation from soluble to insoluble form.