Using titanium gypsum in FA-GGBS based geopolymer for soil stabilization

Abstract

This study investigates the potential use of titanium gypsum (TG), a by-product of the titanium dioxide industry, as a supplementary precursor in fly ash-ground granulated blast furnace slag (FA GGBS) based geopolymers for soil stabilization.

A series of laboratory tests are conducted to evaluate the effects of TG on the fresh and hardened properties of geopolymer grout, including setting time, flowability, and unconfined compressive strength (UCS), as well as its performance when applied to soft soil. Microstructural analyses using Microstructural analyses using X-Ray Diffraction (XRD), Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA) are performed to elucidate the reaction mechanisms. The results show that an appropriate dosage of TG (4%) significantly enhances the formation of C-(A)-S-H gel and needle-like ettringite, leading to improved strength and microstructural densification. However, TG addition shortens the setting time and reduces flowability, necessitating the use of a phosphate-based retarder to ensure adequate workability. With 4% TG and 3% retarder, the geopolymer grout achieves a 28-day UCS of nearly 60 MPa, exceeding the strength requirement of Portland cement (PO 42.5).

When applied to soil stabilization, the geopolymer–soil mixtures exhibit very low strength at low binder contents, but strength gradually increases with higher binder dosage. Nevertheless, even at 40% binder content, the 28-day UCS reaches only 4.95 MPa, which remains lower than that of cement stabilized soil at the same dosage (about 28% UCS lower than cement soil in group of 30% stabilizer). This highlights the need for further research to bridge the performance gap, particularly on how to enable geopolymer binders to match the strength of cement at equivalent contents.

Overall, the findings demonstrate that TG-modified FA-GGBS geopolymers hold promise as sustainable stabilizers, offering significant environmental-friendly advantages by utilizing industrial waste as raw materials and featuring a low-carbon production process compared to Portland cement.

Date of Award	15 Jul 2026
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Juan Wang (Supervisor), Weizhuo Shi (Supervisor) & El Said M.M. Zahran (Supervisor)