Cementless controlled low-strength material (CLSM) based on waste glass powder and hydrated lime: Synthesis, characterization and thermodynamic simulation

Sustainable infrastructure materials are always correlated with the innovative and value-added disposal of solid waste. This study investigates the production of cement-free controlled low strength material (CLSM) depending on the pozzolanic reaction between waste glass powder (GP) and hydrated lime (CH). CLSM mixtures with varying GP/CH ratios were characterized by flow consistency, mechanical properties and durability. The microstructure and phase assemblages of GP-CH binders were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermodynamic simulation. The results showed that a high GP/CH ratio could enhance the workability and self-compacting behavior of the mixtures. Different GP/CH ratios changed the chemical composition of starting system and hence the phase assemblages of the reaction products. It was found that a higher amount of precipitated calcium-silicate-hydrate (C-S-H) gels significantly improved the mechanical properties and duability of CLSM. The GP/CH ratio of 8:2 contributed to the most C-S-H formations and best material properties. On the other hand, the portlandite could impair the water stability and frost durability due to its relatively high solubility in water. Both experimental and modelling results indicated that Ca-rich jennite-type C-S-H tended to react with SiO₂ to form the low-Ca tobermorite-type C-S-H at high Si/Ca conditions, which resulted in the structure evolution of C-S-H gels as GP/CH increased. Finally, the overall phase assemblages of GP-CH binders based on Gibbs free energy minimization (GEM) were proposed, considering different reaction extents of GP. This study paves the path for the large-scale utilization of waste glass in both cement and construction industry.