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Contribution of fly ash (FA) as a complementary additive for dredged sediment (DS) stabilization was studied. The study is focused on definition of an efficient combination(s) to raise the DS properties. FA with lime and cement with both was used. Then, micro and macroscale investigations was performed. Test results demonstrate that FA additions promoted nucleation, formation of cementitious compounds and fabric modifications in sediment. DS stabilized using FA component show lower shrinkage and higher mechanical resistance than that stabilized using conventional binders. FA is found to be efficient in sediment-lime and sediment-cement mixtures since it accelerates cementation and strength gain.

The combined effects of the chemical stabilization of sediments using lime, cement and fly ash on the sediment shear strength behavior are studied for geotechnical purposes. An elemental analysis is carried out to examine the chemical aspects of stabilized sediments resulting from a series of chemical reactions. Direct shear strength measurements are performed to investigate shear strength improvements and stress-strain behavior of mix samples. A statistical analysis using the principal component analysis and the ANOVA (ANalysis Of Variance) method is also conducted to examine the correlation between cohesion and elemental ratio resulting from the chemical reactions. The analysis of the principal components suggests that Ca and Si and Al and K have greater impact on cohesion than the other elements. However, the ANOVA method reveals that the elemental ratios of Si, Al and Ca produce less impact on the sediment overall gain in cohesion at 28 days of curing. These results demonstrate that the gain in cohesion mostly depends on some other physical parameters, which need to be yet examined. The prediction equation of the cohesion indicates each elemental component gain weight on the overall cohesion gain resulting from the chemical reactions. In short, the considered equation still needs to be refined, notably in terms of performing further laboratory testing.