The role of dissolved rice husk ash in the development of binary blast furnace slag-sewage sludge ash alkali-activated mortars

• Published in: Journal of Building Engineering 2022-07, Vol.52, p.104472, Article 104472
• Main Authors: Istuque, Danilo Bordan, Payá, Jordi, Soriano, Lourdes, Borrachero, Maria Victoria, Monzó, José, Tashima, Mauro Mitsuuchi
• Format: Article
• Language: English
• Subjects: Alkaline activation; Blast furnace slag; Microstructure; Rice husk ash; Sewage sludge ash; Sodium silicate suspensions
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2022.104472

This study evaluated the compressive strength performance and microstructure of binary blast furnace slag-sewage sludge ash (BFS-SSA) alkali-activated mortars, in which rice husk ash (RHA) was dissolved in NaOH solution to replace commercial sodium silicate. The dissolution of RHA, performed in a thermal bottle with NaOH solution, enhanced the compressive strength of the alkali-activated mortars based on BFS up to 4.5-fold. BFS-SSA based mortars (10–40% SSA), activated with NaOH/RHA-based sodium silicate suspensions, reached a compressive strength up to 30 MPa after 28 curing days at 20°C. The RHA dissolution enhanced the strength and sustainability of the BFS-SSA alkali-activated mortars. •Blast furnace slag (BFS) and sewage sludge ash (SSA) mixtures were used as precursors.•The strength of BFS-SSA alkali-activated mortars is enhanced using NaOH/RHA-based sodium silicate suspensions.•Compressive strength above 30 MPa was achieved for the BFS-SSA alkali-activated mortars.•The main gel formation in the BFS-SSA alkali-activated materials was C-(N)-A-S-H.•SSA increased the occurrence of porous C-(N)-A-S-H gel type.