Geotechnical parameters of mixtures of a tropical soil with water treatment sludge

Abstract

Addition of Water Treatment Sludge (WTS) to soils in earthworks may reduce land disposal of WTS and exploitation of natural soils. In this perspective, geotechnical properties of mixtures of a Brazilian tropical soil with WTS in the proportions 5:1, 4:1 and 3:1 (by wet weight) were evaluated. Grading curve and Atterberg limits were obtained for the WTS, soil and mixtures. One-dimensional consolidation, triaxial compression and permeability tests were carried out on compacted specimens of the soil and the soil-WTS mixtures. Geotechnical characteristics of the mixtures resulted slightly different from those of the soil, and previous air-drying affected the compaction parameters of the mixtures. The mixtures presented higher compression indexes than the soil, however swelling indexes were similar for all materials. Hydraulic conductivity decreased with WTS addition, whereas internal friction angles of the mixtures increased and effective cohesion decreased with increase of WTS content. The geotechnical parameters of the mixtures are acceptable for earthworks and indicate possibility of WTS reuse, to be further analyzed relative to environmental feasibility.