Eco-Friendly Activating Solutions from Cocoa Pod Ash and Rice Husk Ash for Geopolymerization

This study investigated the potential of Cocoa Pod Ash (CPA) and Rice Husk Ash (RHA), respectively, as sustainable sources of potassium and amorphous silica, in the preparation of activating solutions for geopolymerization. CPA was successfully used to extract K-salt that was found to be a carbonate salt using FTIR analysis. The K-salt was used as substitute of NaOH, together with RHA as silica source to prepare activating solutions via hydrothermal dissolution. The obtained activating solutions were successfully used in the geopolymerization of both calcined kaolinitic and lateritic clays. The synthesized geopolymers were characterized using X-ray Diffraction (XRD), Fourier transformed infra-red (FTIR) and the measurement of some physico-mechanical parameters. including setting time, compressive strength, density, porosity and water absorption. The results indicate an improved response of the geopolymer products withing K-salt addition of 15–20% (w/w), with respect to total alkali. Beyond 20%, there was a lowering of the various responds that was associated to matrix weakening brought by carbonatation. The alkalinity of all the activating solutions was sufficient for geopolymerization without retention of excess alkali ions in the binder system, as indicated by the absence of efflorescence on the geopolymer surfaces. This study demonstrates the potential of using locally sourced agro-wastes materials to produce sustainable activating solution.