A Fundamental Parametric Study on the Solidification of Malaysian Dredged Marine Soils

An enormous amount of dredged soils was generated from Malaysian rivers, lakes and seas. These dredged soils have poor geotechnical properties and are generally classified as “useless materials” [1]. However dredged soils can be recycled and reused as a potentially useful geo-material by solidification. This paper presents the study exploring the reuse potential of Malaysian dredged marine soils via the solidification technique, i.e. by using ordinary Portland cement and Class F fly ash. The dredged sample was essentially a high plasticity clay with a natural moisture content of approximately 166 %. As determined from standard compaction tests, the maximum dry density and the optimum moisture content were 1.49 Mg/m (equivalent to14.62 kN/m ) and 24 % respectively. XRF (X-ray fluorescence) analysis showed that the material 3 contained high concentrations of SiO and Al O This was supported by the XRD (X-ray diffractometry) results, 2 2 3. showing presence of quartz, halite, calcite and kaolinite as the primary compounds in the sample. The dredged soil was solidified with 10 % of additives by dry mass of soil with various ratios of cement: fly ash, i.e. 10:0, 7:3, 5:5, 3:7 and 0:10. The specimens were then subjected to curing times of 3, 7 and 28 days. pH of the solidified specimens showed an increment with increased cement content as well as curing time. Observations with FESEM (Field Emission Scanning Electron Microscopy) revealed effective sealing of voids within the original soil mass through the solidification process, evidence of the formation of cementitious products. These cementitious gels, such as calcium silicate hydrate (CSH) and calcium aluminium silicate hydrate (CASH), would play a crucial role in strength development of the treated dredged soil. As a general conclusion, solidification using cement-fly ash could revive the otherwise discarded dredged marine soils for reuse as a sound geo-material in various civil engineering applications, especially as a backfill material.