Evaluation of the impact of fiber reinforcement on the durability of lignosulfonate stabilized clayey sand under wet-dry condition

It is a good practice to change the soil properties when dealing with inappropriate soils in geotechnical engineering, which is referred to as soil improvement. In this study, the effect of lignosulfonate (2% weight ratio of soil as an optimum percentage), stabilizer and PP fibers (0.4, and 0.8% weight ratio of stabilized soil) as reinforcement on the soil durability of clayey sand was investigated. For this purpose, 23 unconfined compressive strength tests, 11 durability tests, 60 ultrasonic pulse velocity (UPV) tests, 7 SEM tests, 2 Atterberg limit tests, and 4 standard compaction tests were performed. The results of this study showed that the addition of lignosulfonate improves the durability of clayey sand. However, the stabilized sample only resisted two Cycles of Wet-Drying. The addition of fibers increased the durability of stabilized samples up to 12 cycles by 0.8%. Therefore, this amount of fiber is recommended for improving the behavior of soil stabilized with lignosulfonate. The accumulate loss of mass diagram indicated that the addition of fiber in lignosulfonate treated soils causes a reduction in the Mass-loss rate of the spacemen. Also, by increasing the number of cycles, samples showed softer behavior, and the ultrasonic pulse velocity was reduced, which these results can be interpreted from the deformation coefficient equivalent to 50% strength diagram and ultrasonic pulse velocity of stabilized and reinforced samples. The SEM results showed that the flocculated structure and also the 3D reinforcement by fibers prevented the weight loss of the materials. Finally, the results of UPV test showed that it could be used as a nondestructive test to control the durability of lignosulfonate-stabilized soils.