Enhancing properties of cement mortar with tyre-char derived graphene oxide: Mechanical and microstructural analysis

Cement is one of the most widely used materials in the building industry due to its cost-effectiveness and availability. However, its performance limitations have prompted the incorporation of nanomaterials to improve mechanical and microstructural characteristics. Graphene oxide (GO) has shown significant potential as an additive, though its high-cost limits large-scale application. This study presents a sustainable approach to synthesise GO from waste tyre rubber using microwave-assisted pyrolysis (MAP), followed by characterisation through XRD, Raman spectroscopy, XPS, and SEM. The resulting tyre char-based GO (TC-GO) was incorporated into cement mortar at 0.01 %, 0.03 %, and 0.05 % by weight. For comparison, control samples and samples with only tyre char (TC) were also prepared. The results showed that workability decreased in both TC and TC-GO mixes due to particle agglomeration. Nevertheless, the addition of TC-GO had a greater positive effect on mechanical performance. At 28 days, the highest compressive strengths were reached by 0.01 % TC (29.0 MPa) and 0.03 % TC-GO (30.0 MPa), while the highest flexural strengths were found for 0.03 % TC (6.9 MPa) and 0.03 % TC-GO (7.6 MPa). The 0.03 % TC-GO sample performed the best overall, with a 15 % improvement in both strengths over the control. SEM and EDS analyses confirmed a denser microstructure and a reduced Ca/Si ratio (1.9 vs. 2.4 in control), indicating enhanced calcium silicate hydrate (C-S-H) formation. These findings highlight the potential of TC-GO as a low-cost, sustainable nanomaterial for improving the durability and mechanical performance of cement mortar. • TC-GO was synthesised from tyre char via two-step microwave pyrolysis. • 0.03 % TC-GO improved mortar strength by 15 % over control at 28 days. • SEM showed denser matrix and enhanced C-S-H formation in TC-GO mortar. • Novel use of waste tyres offers a low-cost method to enhance cement properties.