Eco-friendly Geopolymer Composite Based on Non-heat-treated Phosphate Sludge Reinforced With Polypropylene Fibers

Abstract

Geopolymers produced with metakaolin (MK) and thermally untreated phosphate sludge (PS) are beneficial and environmentally advantageous materials, but their fragility limits its applications. The present research aims to evaluate the influence of polypropylene fibers PPF inclusion in MK/PS based geopolymers in view of overcoming the brittleness of these materials. The geopolymer matrix was prepared by mixing the thermally untreated phosphate sludge with the metakaolin in a proportion of 50% by weight, then short polypropylene fibers (PPFs) as reinforcement material were incorporated in amounts of 0.25, 0.50, 1, and 1.5%. Composite performances were assessed in the fresh state through flow measurement, and in the hardened state through the properties of the composites under bending and compressive loading conditions. In addition, the fiber/matrix interfacial contact area was examined using scanning electron microscopy (SEM). The outcomes demonstrate that the PPF incorporation of up to 1.5% by weight into MK/PS based geopolymer paste significantly improves the flexural strength with an increase of 41% (6.41 and 9.62 MPa), as well as leads to a slight decrease of compressive strength and density. The findings of the current research reveals also that MK/PS based geopolymers can achieve a high ductility with an adequate reinforcement.