In-depth investigation of the long-term strength and leaching behaviour of inorganic polymer mortars containing green liquor dregs. (20th May 2019)

• Record Type: Journal Article
• Authors: Novais, Rui M.; Carvalheiras, João; Senff, Luciano; Seabra, Maria P.; Pullar, Robert C.; Labrincha, João A.
• Is Part Of: Journal of cleaner production. Volume 220(2019)
• Page Start: 630
• Page End: 641
• Publication Date: 2019-05-20
• Subjects: Green liquor dregs -- Biomass fly ash -- Geopolymer -- Mechanical resistance -- Long-term performance -- Leaching; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2019.02.170
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: Green liquor dregs are the most challenging waste stream coming from the pulp and paper industry. Despite tremendous efforts, there are not currently any viable recycling alternatives for this massively produced waste (2 Mt/year), which inevitably ends up in landfills. Urgent actions must be undertaken to tackle this. In this work, a substantial amount of dregs was incorporated into eco-friendly, waste-based inorganic polymer (geopolymer) mortars as fine filler. Then, and for the first time, the long-term strength performance (up to 270 days) and heavy metals leaching behaviour of the dregs-containing mortars was evaluated. The effect of the mixture composition and dregs incorporation content on the fresh- and hardened-state properties of the mortars was also studied. Dregs were found to increase the initial and final setting time of the slurries, thus extending the open time before their in-situ application. The use of dregs as fine filler effectively enhances the compressive strength of the mortars, and decreases their water absorption levels. These eco-friendly building materials showed excellent long-term performance, as their strength continuously increases up to the 270 th day (after mixture), and no signs of efflorescence formation were detected. Moreover, the heavy metals leaching levels of the mortars were well below the contamination limits in soil, which demonstrates the feasibility of this recycling methodology. Graphical abstract: Image 1 Highlights: Eco-friendly geopolymer mortars containing green liquor dregs were synthesised. For the first time the durability and leaching behaviour of dregs-containing mortars was studied. Dregs effectively enhanced mortars' compressive strength (up to 44%). Samples' compressive strength increased with ageing demonstrating their durability. Mortars' heavy metals leaching levels were below the contamination limits in soil.