Mechanical Properties and Modification Mechanism of Disintegrated Carbonaceous Mudstone Reinforced with Xanthan Gum

Disintegrated carbonaceous mudstone (DCM) is widely used as embankment fillers in concrete engineering because of its low cost and ecofriendly features. However, DCM has low strength and large deformation; further disintegration will also occur, especially under the rainy conditions. These shortages limit its performance and impede its extensive application. Herein, xanthan gum (XG) is utilized as a cementitious material to reinforce the mechanical properties of DCM. The unconfined compressive strength (UCS), direct shear, dry–wet cycles, permeability coefficient, dynamic rebound modulus (DRM), and physicochemical properties have been studied to evaluate the mechanical behavior and modification mechanism of the XG-modified DCM. Results demonstrate that the optimal addition of XG at a content of 2.5% generated a significant enhancement in UCS strength, reaching 1.12 MPa after 14 days, which is more than twice as the unmodified DCM (0.54 MPa). Further, the cohesion and internal friction angle improved by 23 kPa and 4.2°, respectively. Additionally, attenuation amplitudes of DRM and the permeability coefficient under dry–wet cycles conditions are also significantly reduced. The modification mechanism of XG on DCM was further illustrated by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller analysis. The addition of XG effectively fills the internal pores of DCM and binds the particles into a dense, solid polymer structure through colloidal interactions. Besides, the interaction between the cations on the surface of XG and DCM contributes to the particle strength; further, intermolecular hydrogen bonds reinforced DCM, as well. This study provides an experimental and theoretical basis for the modification and sustainable utilization of DCM in engineering applications.