Cracking and desiccation of water treatment sludge for incorporation into soils for alternative liner material production

Abstract

Cracks may lead to hydraulic failure in soils due to increase of hydraulic conductivity which facilitate water infiltration, impacting negatively for liner materials. Therefore, cracking and desiccation investigation on liner material is advised. Water treatment sludge (WTS) is a by-product resulting from water treatment plants, and it seems to be suitable for geotechnical applications and soil replacement due to hydraulic latent properties, chemical similarities to soils, and mechanical behaviour. In this work WTS samples were incorporated into soil in different ratios – 05%; 10%; 15% and 20% of waste in dried mass of the geocomposites. The four mixtures, a soil sample and a WTS were tested according to the following procedure: two different circular Petri dishes samples were used, 5mm(H5) and 10mm(H10), and two cylindrical compacted samples with 65-70mm of diameter and 20-140mm of height (EDO-TRI, respectively) - dried for 10 days in controlled temperature and humidity. Water release curves (WRC), digital images correlation supported Crack Intensity Factor (CIF) index results were obtained for each material. Cracking behaviour results were compared with the permeability through falling head laboratorial tests, and studies around WTS ratio. Composites with 10% and 15% had the best results, showing no cracks during Petri dishes procedures for H10, in addition, the permeability for these materials reached the maximum for liner production – 10-9 m/s according to European and American directives - making possible the development of an alternative and feasible liner material.