Abstract: Traditional cement soil is of high alkaline, high carbon emissions and dependency on water conservation, and also has adverse effects on the desertification in northwest region of China. Indoor experiment was conducted to investigate the curing effect of biopolymer (xanthan gum) on northwest silty soil and the curing mechanism. Compared with plain soil, xanthan gum as a biopolymer curing agent has good curing effect on silty soil. The compressive strength of dry-mixed soil is higher than that of wet-mixed soil. With the decrease of water content, the ionic bond strength between the molecular chain of xanthan gum and the soil particles increases rapidly, resulting in the growth in strength of solidified soil. The molecules of xanthan gum are firmly adsorbed on the surface of soil particles, playing a very strong cementation role. Moreover, biopolymer solidified soil is neutral, environmental-protecting and renewable, whose strength is formed in natural environment. It is of prominent application prospect and research value, for arid area of northwest China, in particular, as it has functions of moisturizing and anti-desertification.

Key words: biological polymer, xanthan gum, natural curing, solidification, unconfined compressive strength, ionic bond