A more sustainable destination for water treatment sludge (WTS) is its use in earthworks and as landfills liners. However, because of its high water content and plasticity, the investigation of WTS workability in construction procedures is mandatory. As a contribution for this purpose, this paper investigated the thixotropic effect of Cubatao WTS by means of laboratory vane tests. The experimental procedure consisted in preparing triplicate samples of sludge remolded at the liquid limit and storing them for different times to determine the gain of undrained shear strength. Results indicate that Cubatao WTS is thixotropic. The very low remolded undrained shear strength triples after five months of storage. Despite the thixotropic regain reaching 200%, the strength is still insufficient for geotechnical purposes and additional treatments will be necessary to turn the sludge into a reusable material for earthworks.
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