Geopolymers from Olive Stone Bottom Ashes for Sustainable Construction: Influence of the Molding Method

Elena Picazo Camilo (), Juan José Valenzuela Expósito, Raúl Carrillo Beltrán, Griselda Elisabeth Perea Toledo and Francisco Antonio Corpas Iglesias
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Elena Picazo Camilo: Higher Polytechnic School of Linares, University of Jaén, 23700 Linares, Spain
Juan José Valenzuela Expósito: Higher Polytechnic School of Linares, University of Jaén, 23700 Linares, Spain
Raúl Carrillo Beltrán: Higher Polytechnic School of Linares, University of Jaén, 23700 Linares, Spain
Griselda Elisabeth Perea Toledo: Higher Polytechnic School of Linares, University of Jaén, 23700 Linares, Spain
Francisco Antonio Corpas Iglesias: Higher Polytechnic School of Linares, University of Jaén, 23700 Linares, Spain

Sustainability, 2025, vol. 17, issue 13, 1-40

Abstract: The forming methodology influences the physicochemical, mechanical, and microstructural properties. In this study, which aims to develop a geopolymeric material for potential insulation applications in buildings such as vertical walls, geopolymers were developed using industrial wastes from different industries: slate stone cutting sludge (SSCS) and chamotte (CH) were used as precursors, and olive stone bottom ash (OSBA) and sodium silicate (Na 2 SiO 3 ) were used as alkaline activators. Two forming methods were evaluated: uniaxial pressing and casting of the material, varying the forming method and the liquid/solid ratio. The results showed that the pressed geopolymers achieved higher bulk densities (up to 2.13 g/cm 3 ) and significantly higher compressive strength (28.04 MPa at 28 days), attributable to a higher compactness and degree of geopolymer reaction. In contrast, the casting geopolymers exhibited surface efflorescence, related to slower curing and higher porosity, which reduced their compressive strength (17.88 MPa). In addition, the pressed geopolymers showed better thermal stability and fire performance. These results demonstrate that the variation of the forming method has a direct influence on the material properties of geopolymers, and that the pressing process allows for a reduction of the alkaline activator content, thus reducing its environmental footprint.

Keywords: geopolymers; cold pressing; casting; mining waste; bottom biomass ash; chamotte (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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