Alkaline Activation of Ceramic Waste Materials

Abstract

Ceramic materials represent around 45 % of construction and demolition waste, and originate not only from the building process, but also as rejected bricks and tiles from industry. Despite the fact that these wastes are mostly used as road sub-base or construction backfill materials, they can also be employed as supplementary cementitious materials, or even as raw material for alkali-activated binders. This research aimed to investigate the properties and microstructure of alkali-activated cement pastes and mortars produced from ceramic waste materials of various origins. Sodium hydroxide and sodium silicate were used to prepare the activating solution. The compressive strength of the developed mortars ranged between 22 and 41 MPa after 7 days of curing at 65 °C, depending on the sodium concentration in the solution and the water/binder ratio. These results demonstrate the possibility of using alkali-activated ceramic materials in building applications. Ceramic materials represent around 45 % of construction and demolition waste in Spain. In the present study, two different ceramic materials, red ceramic bricks and porcelain stoneware were alkali-activated in order to produce pastes and mortars. The figure shows the microstructure of pastes obtained using a sodium silicate solution and NaOH pellets as activators. Both materials presented differences related to the process and the optimum concentration of activator. Mortars with compressive strengths ranging from 22 to 41 MPa were obtained after 7 days of curing at 65 °C, which make them suitable for building applications.