Integrated study on rheological behaviour, bleeding resistance, and strength of xanthan gum as additive in cement grout

The incorporation of biopolymer-based viscosity modifying agents has emerged as a promising approach for improving the stability of cementitious grouts. This study investigates the influence of xanthan gum (XG) on cement grout with a water-cement ratio of 0.6 over a dosage range of 0–1.5% by weight of cement. Rheological properties were characterised using the Herschel-Bulkley model, while thixotropic behaviour was evaluated using a three-interval thixotropy test (3ITT). Bleeding resistance and compressive strength at curing ages of 7, 14, and 28 days were assessed. The results show that increasing XG dosage progressively modifies the rheological response of the grout. Yield stress and consistency index increase with XG content, while the flow index decreases, indicating increasingly pronounced shear-thinning behaviour. Structural breakdown during high shear remains relatively constant (95.9–97.0%), whereas the structural recovery ratio decreases at low XG dosages and then remains relatively stable at approximately 80% at higher XG contents, indicating a stable rebuilding response at higher XG dosages. Bleeding decreases substantially from 7.04% in the reference grout to 1.22% at 1.25% XG, demonstrating improved suspension stability. At low dosages (≤0.2%), the compressive strength remains comparable to that of the control mixture, whereas higher XG contents gradually reduce the strength. When considered in relation to practical grouting requirements, including rheological behaviour, thixotropic response, bleeding resistance, and compressive strength, low to moderate XG dosages provide the most balanced performance. The results highlight the potential of xanthan gum to enhance the stability of cement grout while maintaining mechanical performance for grouting applications.