Characterisation of bentonite polymer for bottom liner use

This paper aims to study the hydromechanical behaviour and the clay polymer interaction of amended Ca-bentonite. Specimens were formed by mixing Ca-bentonite with two soluble polyelectrolyte polymer powders. Some important parameters are studied: swelling, water adsorption and hydraulic performance for landfill applications. Tests are performed with tap water and synthetic leachate (SL) to reproduce the hydrochemical phenomena. Hydraulic performance tests were performed with an oedopermeameter. Tests results show that polymers tend to reduce the permeability when in contact with the SL. Water adsorption and free swell index tests confirmed that adsorption, swelling and permeability parameters depend on the clay polymer mixtures and that adding polymers improves the clay properties. Each polymer’s charges has a different effect: the anionic polymer gives low permeability to the mixture, and the cationic polymer enhances the bentonite swell ability and water retention, which can be used also as a performance index.