Expansive clay treated with lignin: Insight on water pollution

¹ Engineering Faculty, Universidad Nacional de la Patagonia San Juan Bosco, Argentine
² Natural Science Faculty, Universidad Nacional de la Patagonia San Juan Bosco, Argentine
³ ETS Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, Spain

^* Corresponding author: sandra.orlandi@gmail.com

Abstract

Modification of the expansive properties of clays can be addressed using additives. This is a widespread practice, with lime being the most used additive. In the last two decades, polymeric additives, mostly by-products or residues from local industries, have gained importance. Many of these additives are organic, such as lignins and lignosulphonates. The approach used to validate the efficiency and efficacy of each new additive focuses on analyzing the changes that occur in both swelling potential and swelling pressure. Stabilization mechanisms can be analyzed by studying changes in mechanical, hydraulic, and microstructural properties. An effect that has been little studied is the environmental impact caused by the incorporation of additives into soils. In this article, the toxicity of a calcium lignosulphonate is studied using the method of control organisms, in our case Lactuca Sativa seeds, and by determining the pH. The study was conducted with different concentrations of leachate obtained from triaxial consolidated drained (CD) tests. The results showed the concentrations at which the lignosulphonate solution inhibited (50% development) or prevented (0% development) the growth of radicles of the control organism. Changes in the pH of the concentrations are also shown. These changes not only represent positive results for calcium lignosulphonate used as an expansive soil stabilizer. They also aim to raise awareness of the environmental impact of these additives and the importance of including them in routine testing.