Investigation of unconfined compressive strength for biopolymer treated clay

In this study, six typical biopolymers (xanthan gum (XG), sodium alginate (SA), kappa gum (KG), locust bean gum (LBG), agar gum (AG) and gellan gum (GE)) are selected to investigate the mechanical strength of biopolymer treated clay with the consideration of different hydrated conditions, biopolymer concentration, curing time, wetting–drying, the combination of two different types of biopolymers and biopolymer-soil mixing method. From the results, it can be seen, under the same conditions, out of the six different biopolymers, SA-treated clay provided the highest unconfined compressive strength (UCS) (3.58–4.5 times of untreated clay). Moreover, an optimum reinforcement performance was found when biopolymer concentration was within the range of 1–2% with a curing time between 28 and 42 days. Furthermore, despite biopolymers being eco-friendly materials, with great potential under the biodegradation process, current research results demonstrated that XG treated clay can maintain UCS even after curing 378 days and undertaking 3 cycles of wetting–drying processes. In addition, the maximum UCS of XG combined KG treated soil can be observed in the ratio of 1:1. Hot-water dry mixing method can be adopted to obtain uniform XG, SA or KG-clay mixture further improving the soil strength, while AG, GE and LBG treated clay has a better strengthening efficiency by using hot-water wet mixing method.