STRENGTH DEPENDENCE OF STEEL SLAG–DREDGED SOIL MIXTURES ON SOIL ORGANIC MATTER REMOVAL WITH HEAT TREATMENT AND DILUTION WITH VOLCANIC ASH

Abstract

The effect of soil organic matters (SOMs) to the uniaxial compressive strength (q_u) of steel slag–dredged soil mixtures was evaluated by partial removing and altering SOM by heat treatment. The effect was also evaluated by dilution of SOMs using a volcanic ash soil. Two dredged soils formed soft mixtures, in which SOM was suspected to be inhibiting the q_u development. Within the studied cases, it was clarified that the dilution of SOMs by the volcanic ash did not improve the q_u, whereas partial removal and alteration of SOMs by heat treatment could improve it significantly. This study demonstrated that moderate heat treatment could modify the structural development of steel slag–dredged soil mixtures. In addition, q_u of the different SOM removal ratios showed that even a slight SOM removal could still increase q_u. From the comparison of the different heat treatments, it was further suggested that a specific type of SOM inhibited the q_u development of the mixtures. Raman microscopy and Emission Excitation Matrices analysis revealed heat treatment did not only remove SOMs but also decreased the aromatic structures and the molecular size of SOMs, which likely depicted the characteristics of SOMs inhibiting the q_u of the mixtures.