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