Effect of silica fume and waste rubber on the performance of slag-based geopolymer mortars under high temperatures

In this study, the fire resistance of slag-based geopolymer mortars was investi-gated and the effect of silica fume (SF) and waste rubber (WR) on this resistance was determined. In slag-based geopolymer mortars activated using 12M NaOH solution, 0%, 5%, and 10% by weight SF was substituted for slag; 0%, 5%, 10%, and 15% WR by volume were substituted for fine aggregate. The samples that completed the curing period were exposed to temperatures of 250 degrees C, 500 degrees C, and 750 degrees C for 1 h, and the mechanical (compressive, flexural and splitting tensile strengths, and impact resistance), physical (weight change and sorptivity) and microstructure (scanning electron microscopy [SEM] and energy dispersive spectroscopy [EDS]) properties of these samples were examined. The compres-sive strengths of the samples without WR were between 48.10 and 60.97 MPa, and the samples without SF were between 28.52 and 48.10 MPa. Strength losses at 750 degrees C were between 51.5% and 73.5%. As the SF substitution increased, the samples' mechanical and physical properties improved, whereas as the WR sub-stitution increased, the samples' mechanical and physical properties declined. While the SF substitution had a positive effect on the fire resistance of the sam -ples, the WR substitution had a negative effect. It is thought that the choice of geopolymer binder as a binder in the mortar and the use of waste tires as aggre-gate contribute to the literature in terms of both preventing environmental pollution and ensuring the recycling of these materials.