Geotechnical performance of dredged material-steel slag fines blends: Laboratory and field evaluation

This paper contains the results of a combined laboratory and field demonstration project exploring the use of dredged material (DM) blended with steel slag fines [SSF; 9.5 mm (3/8 in:) minus] as synthetic fill materials. The granular nature [a well graded sand (SW) soil], mineralogy, reactivity, and residual lime content of the SSF media make it well suited for blending with DMhigh-plasticity organic (OH) soil, so that geotechnical and environmental soil improvement occur simultaneously with one amendment. The source materials (100%DM, 100%SSF)were evaluated along with 80/20, 60/40, 50/50, 40/60, and 20/80 DM-SSF blends (dry weight basis), where the DM content is reported first. Key findings include that the 100%DMhad a φ′_CIÛ of 27.3°, which increased to a peak φ′_CIŪ value of 45° for the 50/50DM-SSF blend. The hydraulic conductivity (k) of the 100%DM(10^-8 cm/s) remained relatively constant until SSF content reached 80%,where an abrupt increase to 105 cm/s was observed. The field demonstration project confirmed that the DM-SSF blends could be easily blended to within ±5% of their target DM content.Trial highway embankmentswere constructed with 100%DM, 100%SSF, and the 80/20, 50/50, and 20/80DM-SSF blends tomodified Proctor compaction goals ranging from85 to 95%relative compaction on themaximumdry unitweight, depending on the blend. The average cone penetration test (CPT) tip resistance for 100% DM and 100% SSF media were approximately 1.3 and 57.3 MPa, respectively. The compacted 80/20, 50/50, and 20/80DM-SSF blend embankments were generally characterized by average CPT tip resistances on the order of 2.9, 6.2, and 11.6 MPa, respectively.