Co-valorisation of Dunkirk dredged sediments and siliceous–aluminous fly ash using lime

The objective of this work was to investigate a viable alternative for the final disposal of siliceous–aluminous fly ash and dredged sediments by using them as roadbed materials. For this purpose, the physical parameters of sediments were studied through a series of laboratory tests. For designed mixes, in terms of mechanical property, the modified compaction tests, unconfined compressive tests and tensile strength tests are realised to evaluate the evolution of compaction and strength characteristics of sediments with different curing time and binder content. The standardised swelling tests were carried out to appraise the effect of lime and fly ash on swelling potential and Immediate California Bearing Ratio index. To appraise the durability of designed materials, the thawing–freezing tests and water immersion tests were carried out. A coefficient of strength loss was defined to quantify the effect of freezing–thawing damage and water immersion ageing on compressive strength of sediments. Finally, the X-ray diffraction analysis and schematic sketch were undertaken to explain the microstructure change and mechanism of strength improvement of lime/fly ash-treated sediments.