Performance and mechanism of silt modified with high dosage soda residue composite material

ObjectiveThis study investigates the combination of soda residue, as an alkaline activator, with fly ash and solid waste based binder. The purpose is to improve the road performance of silt with low liquid limit.MethodThe unconfined compressive strength test, swelling test and water stability test for the modified silt were carried out. Microscopic analysis on solidification mechanism was conducted through Zeta potential, X-ray diffraction, scanning electron microscopy and energy dispersion spectrometer.ResultThe silt strength could be modified by adding soda residue. The optimal dosage is 45%. The addition of fly ash and solid waste based binder could improve the compressive strength and water stability of modified silt with alkaline excitation effect. It meets the bearing capacity of subgrade or subbase of extremely heavy expressways. The swelling ratio of silt, mixed with soda residue, increases. Fly ash could effectively reduce the swelling ratio of soda residue modified silt. The swelling ratio increases when adding solid waste based binder on the basis of adding fly ash. The silt mixed with a large amount of soda residue has more pores. A large amount of hydrated gelling materials (i.e., calcium silicate hydrate, calcium aluminate hydrate and ettringite) is produced by the reaction of fly ash and solid waste based binder in alkaline environment. The pores are mainly filled with hydrated gelling materials, effectively improving the performance of soda residue modified silt.ConclusionThe addition of fly ash has no significant effect on the early strength improvement for soda residue modified silt. The use of fly ash in combination with solid waste based binder for soda residue modified silt would increase the utilization rate of soda residue, as well as reduce the amount of fly ash, and achieve better overall performance.