Mechanical behavior and strengthening mechanism of red clay solidified by xanthan gum biopolymer

To avoid engineering diseases induced by negative geotechnical properties of red clay and to positively reduce adverse impacts on ecological environments caused by employing lots of inorganic solidified material for treating the clays, it is essential to explore low-environmental impact material to improve engineering mechanical performances of the red clay. To date, xanthan gum (XG) biopolymer is regarded as a potentially eco-friendly material with excellent pseudo-plasticity, safety, and stability. Hence, unconfined compressive strength, unconsolidated undrained shear, scanning electron microscopy-energy dispersive spectroscopy, and X-ray diffraction tests were performed to study the solidification effects and strengthening mechanism of XG for red clay under varied additive contents and curing period. The results indicated the optimal XG content and curing ages to increase the macro-mechanics of red clay are 1.5% and 28 d, in which the compressive strength and cohesion are increased by 93.31% and 79.47%, respectively. Further, the mathematical model is established by modifying the Duncan-Chang constitutive model and used to describe the stress–strain relationship of XG-solidified red clay, presenting preferable consistency in the calculated and trial results. The strengthening mechanism is derived from the ionic bondings between XG and red clay, producing significant effects of cementing and filling to form compact composite matrices during the microstructural evolution process.