Hydraulic performance of activated calcium bentonite treated by polyionic charged polymer

The present paper discusses the hydro mechanical behavior of activated Ca–bentonite mixed with two soluble polyelectrolyte powder polymers. To understand better the clay polymer interaction, swelling, water adsorption and hydraulic performance are studied. Synthetized leachate (LS) is used to reproduce the hydrochemical phenomena in the system. Hydraulic performance tests were performed with an oedopermeameter and modified API filter press. Both methods gave the similar bentonite material behaviors and classification order, showing that polymers are reducing the permeability, in contact with the LS. Water adsorption and free swell index tests results have confirmed that (1) adsorption, swelling and permeability parameters are linked for clay polymer mixtures and (2) the polymers could improve the overall clay properties. Each polymer has a different effect: the anionic polymer induces a low permeability to the mixture; the cationic polymer makes the bentonite more swellable, with high ability to retain water and to become more resistant to the LS. Laboratory tests results demonstrate that the behavior of bentonite polymer mixtures for landfill liner applications depends essentially on the nature of the surface charge of the polymer.