Characterisation of mortars using municipal solid waste incinerator bottom ash and slag

¹ University of Antwerp, EMIB-research group, Groenenborgerlaan 171, 2020 Antwerp, Belgium
² Odisee University College, DUBit Research Unit, Kwalestraat 154, 9320 Aalst, Belgium

^* Corresponding author: hanne.bielen@uantwerpen.be

Abstract

The high cement content in repair mortars necessitates the development of sustainable and durable alternatives using supplementary cementitious materials (SCMs). Municipal solid waste incinerator bottom ash (MSWI_BA), generated in substantial volumes annually, is currently being landfilled or used in low-value applications, overlooking its potential as valuable SCM. This study investigates the mechanical properties of traditional clinker-based CEM I mortars modified with fresh (type-V) or matured (type-M) MSWI_BA and ground granulated blast-furnace slag (GGBS). CEM I was partially replaced with 10% and 20% MSWI_BA, and GGBS contents of 0%, 15%, 26%, 56%, and 71% by weight of the 10% MSWI_BA. Tests at intervals up to 120 days examined fresh properties, density, and flexural and compressive strength. Results indicate that MSWI_BA reduces density, while GGBS has a minimal effect. MSWI_BA-mortars exhibited lower flexural strengths, with 10% MSWI_BA outperforming 20%, and 15% GGBS yielding the highest flexural strength among MSWI_BA-mortars. Higher GGBS levels delayed early hydration yet promoted long-term strength development. In compressive strength, 10% MSWI_BA outperformed 20%, with type-M achieving comparable results to CEM II and CEM III/A 32.5 after 120 days, and outperforming type-V. These findings highlight the possibilities of MSWI_BA-GGBS blends as sustainable secondary materials for traditional clinker-based repair mortars.