Abstract: In order to study the effect of polypropylene fiber on the unconfined compression performance of the lime stabilized recycled subgrade, the unconfined compression strength tests of 6 mm, 9 mm and 12 mm length polypropylene fiber modified lime stabilized recycled subgrade materials at sample curing ages of 7 days and 28 days, respectively, were conducted. The test results show that: (1) at the curing age of 7 days, the polypropylene fiber has no effect on improving the unconfined compressive strength of the lime stabilized recycled subgrade; at the curing age of 28 days, the polypropylene fiber has obvious improvement effect on the unconfined compressive strength of the lime stabilized recycled subgrade. Among them, the fiber with a length of 6 mm has the most obvious improving effect, and the unconfined compressive strength of the lime stabilized recycled subgrade with non fiber modified was increased by 42.2%. (2) The addition of the polypropylene fiber greatly improves the durability of the lime stabilized recycled subgrade, and the residual strength of the sample increases with the increase of fiber length. (3) The ductility of the lime stabilized recycled subgrade increases with the increase of the fiber length. 

Key words: polypropylene fiber, lime soil, recycled subgrade