Effects of Xanthan Gum and Lime on Physical Properties and Mechanical Behavior of Organic Soil

A sample of organic soil collected from the Chaharmahal-Bakhtiari Province, Iran, was treated with 0.5, 1, 1.5, 2, 2.5, and 3% of xanthan gum and 1, 3, and 5% of lime. The untreated and the treated specimens were subjected to physical and mechanical tests, including soil classification, pH measurement, compaction test, unconfined compressive strength test, indirect tensile test, and direct shear test. An increase in lime by 3% led to the greatest increase in the compressive strength (5 and 6 times for the 7-day and 21-day samples, respectively) and the tensile strength (3.7 and 4.5 times for the 7-day and 21-day samples, respectively). Xanthan gum also improved the compressive strength (3 and 6 times for the 7-day and 21-day samples, respectively) and the tensile strength (5.9 and 7.5 times for the 7-day and 21-day samples, respectively). Increasing lime up to 3% enhanced the adhesion of the stabilized soil for 3.5 and 7.5 times that of the organic soil for 7 and 21 days of curing, respectively. Also, the friction angle increased by 40%  and 68% times with the increase of lime up to 3% during 7 and 21 days of curing, respectively. Stabilization with xanthan gum led to 11.5 and 17.5 times increase adhesion for 7-day and 21-day samples, respectively. Moreover, xanthan gum increased the friction angle by 47% and 75% for 7-day and 21-day samples, respectively. The findings generally suggest that xanthan gum can be a good ecofriendly alternative to lime as a soil stabilizer.