Study of olive pomace bottom ashes as a sustainable alkaline activator in the syntesis of geopolymers

Abstract

The increase of the cogeneration industry in Spain due to the policies to promote sustainable energies has produced an accumulation of ash in landfills that cause an environmental impact. The research focuses on the re-use of olive pomace bottom ashes (OPBA), a kind of bottom biomass ashes (BBA), as a sustainable alkaline activator for the replacement of NaOH and partial replacement of Na2SiO3. As precursor material, chamotte (CH) was used to valorize wastes from the ceramic industry considering different Na2SiO3/OPBA ratios (1.0, 1.2, 1.3, 1.5, 1.8, 2.1, 5.0). Ceramic and power generation wastes were physical and chemically characterized, and novel geopolymers were subjected to physical and mechanical tests. The results obtained showed that the enrichment of OPBA gives rise to physical and mechanical properties comparable to those of cementitious materials. Values of 26.46 MPa were obtained after 24 h of curing at 85± 5 °C and 27 days at ambient temperature with OPBA substitution ratios of 30 %. Therefore, it is important to highlight the feasibility of alkaline activated geopolymers with biomass ashes and ceramic wastes as a precursor material in the manufacture of mortars, reducing waste and emissions and promoting the circular economy due to the manufacture of sustainable products.