Silicate solutions can improve the durability of concrete conveniently and effectively. To horizontally compare the enhancement effects of different composite silicate solutions, three types of silicate surface treatment agents were prepared by using sodium silicate, potassium silicate, and lithium silicate as the main agents, along with urea, sodium polyacrylate, catalysts, and fluoro-carbon surfactants as the adjuvants. Furthermore, their effects on the durability of concrete were compared. The results showed that silicate surface treatment could reduce the content of Ca(OH)₂, increase the content of hydrated calcium silicate (C-S-H), and improve the compactness and hydrophobicity of the hardened cement surface. Although the three surface treatments enhanced the durability of concrete, the effects differed based on the complexities and mixtures. The sodium silicate compounded with potassium silicate performed the best of all three, wherein the content of the C-S-H gel increased by 389.8%, the permeability decreased by 60.6%, the water contact angle improved to 83.5° and the chloride ion resistance and freeze–thaw resistance of concrete increased by 36.7% and 37.34%, respectively, compared with the control sample.

A series of triaxial compression tests with different confining pressures were conducted for gravels, road surface milling materials, and surface–base milling mixtures to investigate the stress–strain relationships of these three kinds of materials. On the basis of the analysis of the test results, the strength and the deformation of the geocell-reinforced surface milling materials and the geocell-encased surface–base milling mixtures were predicted and compared with those of the gravels via the constitutive model of geocell–soil composites. The effects of the geocell pocket size, tensile stiffness, and the peak internal frictional angle on the stress–strain responses of the geocell-reinforced surface–base milling mixtures were examined. Moreover, by employing the finite element strength reduction technique, stability analysis was conducted on the geocell-reinforced retaining wall with the surface–base milling mixtures to investigate the factor of safety and the failure mechanism of the structure. The study results indicated that the surface milling materials exhibited strain hardening, while the gravels and the surface–base milling mixtures exhibited strain softening. The surface milling materials displayed evident shear contraction characteristics, whereas the gravels and surface–base milling mixtures first displayed shear contraction and later dilatancy features. In addition, the strength of the geocell-reinforced surface milling materials is smaller than that of the gravels, but the strength of the geocell-encased surface–base milling mixtures is larger than that of the gravels. Thus, the geocell-reinforced surface–base milling mixtures can be used to replace the gravels in engineering practices. Additionally, the size of the sliding wedge and the factor of safety of the retaining walls increase significantly with reductions in the geocell pocket size.