Analysis of Geotechnical Properties of Expansive Soil from Sucre (Colombia) Area Mixed with Sawdust Fiber Treated in Alkaline Condition

Abstract

Sawdust is a biodegradable material produced by the timber industry and is abundant worldwide. Inadequate final disposal of waste has adverse environmental effects. The random addition of fibers to soils is primarily inspired by the natural phenomenon of grass and/or plants that can enhance the stability of a slope when they grow on it. Although not novel, this concept has gained popularity in recent years in the field of geotechnical engineering. It has been observed that its addition can improve some of its mechanical properties by increasing the bond between the soil grains, owing to the increase in friction between the fibers and the soil matrix. This study analyzes the impact of the addition of variable doses of oak sawdust (Tabebuia Rosea) on the engineering properties of clayey soil from the Department of Sucre (Colombia) with respect to its shear strength parameters (cohesion and angle of internal friction). The fibers used were divided into three different sizes (less than 2.0 mm, between 2.0 mm and 9.52 mm and greater than 9.52 mm). The fibers were previously subjected to the mercerization process (alkaline treatment with sodium hydroxide) at concentrations and times of 3.0, 5.0 and 8.0 N and 15, 45, and 60 min, respectively, and added in percentages of 2.0, 4.0, and 8.0% in relation to the dry weight of soil. The results indicate that the addition of small amounts of sawdust can positively affect the engineering properties of soils with appreciable clay contents. In this study, it was observed that the optimal results were obtained with the addition of 6% fibers with respect to the dry weight of the soil, improving its density by 7.4%, its unconfined compressive strength by 19.3%, and its cohesion by 24%.