Effect of Activating Solution Modulus on the Synthesis of Sustainable Geopolymer Binders Using Spent Oil Bleaching Earths as Precursor


The valorization of spent oil bleaching earths (SOBE) is crucial for the protection of the environment and the reuse of resources. In this research, alkali-activated binders were manufactured at room temperature using SOBE as a precursor by varying the mass ratio between the activating solutions of sodium silicate (Na2SiO3) and 6 M sodium hydroxide (NaOH) (activating solution modulus) (Na2SiO3/NaOH ratio = 1/1; 1/2; 1/3; 1/4) to investigate the influence on the technological properties of the materials. This process intends to evaluate the potential of SOBE, heat-treated at 550 degrees C (1 h), as a precursor of the reaction (source of aluminosilicates). Samples produced with higher amounts of sodium silicate developed a denser structure, with lower porosity and a higher amount of geopolymer gel. Maximum flexural (8.35 MPa) and compressive (28.4 MPa) strengths of samples cured at room temperature for 28 days were obtained with a Na2SiO3/NaOH mass ratio of 1/1. The study demonstrates that SOBE waste can be used as a precursor in the manufacture of geopolymer binders that show a good compromise between physical, mechanical and thermally insulating characteristics.



subject category

Green & Sustainable Science & Technology; Environmental Sciences; Environmental Studies


Delgado-Plana, P; Rodriguez-Exposito, A; Bueno-Rodriguez, S; Perez-Villarejo, L; Tobaldi, DM; Labrincha, JA; Eliche-Quesada, D

our authors


This research was funded by the project GEOCIRCULA: Circular Economy in the manufacture of new geopolymeric composites: towards the goal of zero waste (P18-RT-3504), funded by the Consejeria de Economia, Conocimiento y Universidad of the Junta de Andalucia, with co-financing from the European Union through ERDF funds, from the incentive program for Universities and public research entities qualified as agents of the Andalusian Knowledge System, within the scope of the Andalusian Plan for Research, Development and Innovation (PAIDI 2020).

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