Olive biomass ash-based geopolymer composite: development and characterisation

Alternative fuels are being used increasingly to reduce energy costs and benefit the economics of electric power industries. Olive residues could be among those alternative fuels. This paper investigates the potential use of olive biomass ash (OBA) to develop a new sustainable binder (geopolymer composite). Refined binder chemistry was developed where the alkali and silica contents of the OBA are supplemented by calcined kaolin (CK) as alumina-rich constituents targeting balanced chemistry. The results showed that optimum formulation was achieved when 40 wt-% OBA and 60 wt-% CK were blended yielding geopolymer concrete with 28-day compressive strength of 30 MPa. Further refinements were carried out by adding of CaO or NaOH. The compressive strength reached to more than 45 MPa when 5 wt-% CaO or 10 wt-% NaOH was added to the optimum blend. microstructural and mineralogical studies were performed to get insight into the microstructural changes and explain the findings.Abbreviations: ASTM: American Society for Testing and Materials; CK: Calcined Kaolin; CSH: Calcium Silicate Hydrates; DTG: Differential Thermogravimetric Analysis; EDS: Energy Dispersive X-ray Spectroscopy; LOI: Loss-On-Ignition; NASH: sodium Aluminosilicate Hydrates; OBA: Olive Biomass Ash; SEM: Scanning Electron Microscopy; TGA: Thermogravimetric Analysis; XRD: X-Ray Diffraction; XRF: X-Ray Fluorescence