The Role of an Industrial Alkaline Wastewater in the Alkali Activation of Biomass Fly Ash


Featured Application This work aims to further decrease the environmental footprint of alkali-activated materials by using an industrial wastewater to partially replace a commercial activator. Alkali-activated materials are generally considered a more sustainable alternative to Portland cement binders. This derives not only from the use of solid wastes as precursors, but also from the low temperatures required for their synthesis. However, to increase the environmental advantages of these materials, alternative activators should be explored, as the common route involves the use of commercial activators such as sodium silicate or sodium hydroxide solutions. In this work, the possibility of using an alkaline industrial wastewater, coming from a Portuguese paper and pulp industry, as a partial replacement of the commercial sodium hydroxide solution was studied. The results show that the use of the industrial wastewater decreased the workability of the pastes and their setting times, higher incorporations inducing a stronger reduction. Despite this, the results demonstrate the feasibility of replacing up to 25 vol.% of the sodium hydroxide solution with the industrial wastewater without compromising the mechanical performance of the binder. The compressive strength of this composition reached 22.7 MPa, this being slightly higher than the value seen in the reference (20.0 MPa). The use of a waste-containing activator, as reported here, might be a key driver to foster the wider use of this technology.



subject category

Chemistry; Engineering; Materials Science; Physics


Novo, CC; Senff, L; Seabra, MP; Novais, RM; Labrincha, JA

our authors


The authors would like to acknowledge the project ERA-MIN/0001/2019 (SMART-G-Smart Geopolymers). R.M. Novais also acknowledges the FCT support under the grant (2020.01135.CEECIND). This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC).

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