Sustainable alkali activated materials: Precursor and activator derived from industrial wastes

The aim of the present paper is to analyse the potential application of a solution used to wash moulds from the aluminium casting industry as an alkali activator, for inclusion in the production of alkaline cement. To evaluate the effectiveness of this cleaning solution (CS), two different by-products/wastes were considered as a precursor: fly ash type F (FA) and glass powder (GP) from the production of optical lenses. An 8 molar sodium hydroxide commercial solution was used to establish threshold values for the CS activator. Several mixtures were prepared and cured for 20 h, at 85 degrees C, at high humidity (>= 90%). Mechanical behaviour was assessed by uniaxial compression strength tests. The reaction rate was determined by calorimetry, and the resulting reaction products were characterized by X-ray diffraction (XRD), electron microscopy (SEM/EDX) and nuclear magnetic resonance (NMR-MAS). The results show that the cleaning solution has a high potential to be used as an activator in the manufacturing of alkali activated cement, especially due to its tetrahedral aluminium content, which is particularly effective for the activation of low-Al raw materials, since it acts simultaneously as a cheap aluminium source. (C) 2017 Elsevier Ltd. All rights reserved.