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 DM high-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% DM had a ϕCIU¯′ of 27.3°, which increased to a peak ϕCIU¯′ value of 45° for the 50/50 DM-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 10-5 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 embankments were constructed with 100% DM, 100% SSF, and the 80/20, 50/50, and 20/80 DM-SSF blends to modified Proctor compaction goals ranging from 85 to 95% relative compaction on the maximum dry unit weight, 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 20/80 DM-SSF blend embankments were generally characterized by average CPT tip resistances on the order of 2.9, 6.2, and 11.6 MPa, respectively.