Waste glass powder as silica source for the activator in the preparation of alkali activated SiMn slag mortar

The main objective of this work is to improve the performance of alkali activated ground granulated SiMn slag mortars, avoiding the use of waterglass for the preparation of a more sustainable alkali activator. In this work the sustainable activator was used to develop masonry mortars whose binder is formed by granulated SiMn slag as a solid precursor, and an alternative alkaline activator which was obtained from waste glass powder by a hydrothermal process, varying the NaOH concentration, duration and temperature of the process. The mortars samples were characterized for workability, setting time, strength, bond strength (adherence to masonry bricks), shrinkage and porosity. Life cycle analysis was carried out to assess the environmental impact of replacing Portland cement and commercial solutions with the use of SiMn slag and these alternative activators. Mortars manufactured with the alternative activator have similar setting times, lower compressive strength (reaching values between 35 and 44 MPa after 90 days) and greater porosity compared to those manufactured with commercial activators. The different behaviours observed depending on the different alternative activators used can be attributed to the different quantity of Si that each of them presents. All the studied mortars manufactured with an alternative activator have more than sufficient properties to be used as masonry mortars. These mortars are manufactured using a majority percentage of waste (SiMn slag and glass waste as a source of silica for the activator), so they represent a sustainable alternative in terms of reducing raw materials, energy, and carbon footprint in their production. • Waste glass powder (WGP) has been proved to be a possible source of silica by alkaline hydrothermal process. • Moderate temperatures (60–80°C) and highly alkaline solutions are required for extracting significant amounts of silica form WGP. • Also adiabatic treatments in highly alkaline solutions provided high silica solubilisation from WGP. • The compressive strength of the mortars obtained with an alternative activator reached values between 35 MPa for adiabatic conditions and 44 MPa for 80°C of treatment after 90 days. • Reduction of 40 % of the carbon footprint compared to Portland cement mortar and 10 % compared to the use of commercial solutions for alkaline activation have been achieved.