Aeolian sand stabilized by using fiber- and silt-reinforced cement: Mechanical properties, microstructure evolution, and reinforcement mechanism

Abstract

Northwest China has a large amount of aeolian sand, which exhibits poor gradation, low cohesive force, and loose structure; thus, this sand is difficult to be directly used as engineering construction materials. To solve this problem, this study mixed fiber, silt, and cement to stabilize aeolian sand. The effects of the fiber content (0%, 0.5%, 1%, 2%, 3%, and 4%), fiber length (6, 12, and 19 mm), silt content (10%, 15%, and 20%), and curing time (7, 14, and 28 d) were evaluated by conducting indoor unconfined compressive strength tests, and the strength prediction and constitutive models were established. In addition, the microstructural and pore variation characteristics were studied by performing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and nuclear magnetic resonance (NMR) tests, and the stability mechanism was elucidated. The results showed that the addition of fibers and silt can significantly improve the strength and ductility of cement-stabilized aeolian sand. Under the optimal mixing conditions (fiber length: 12 mm; fiber content: 2%; silt content: 15%), the strength of the sample increased by 274.2% (reaching 1684 kPa) compared with that of cement-stabilized aeolian sand (450 kPa). A positive correlation was observed between the curing time and strength development of the samples. The established strength prediction model effectively predicted the strength variations in the specimens, whereas the constitutive model accurately reflected the stress-strain relationship of the specimens. The SEM results revealed that the coupling effect of fibers, silt, and cement makes the specimens more compact and improves the overall stability. The results of the NMR showed that the numbers of macropores and mesopores decreased significantly and that the numbers of small pores and micropores increased with 2% fiber content; the porosity of the specimen was 12.3%, which was 28.6% lower than that of ordinary-cement-stabilized aeolian sand. This study advocates making full use of local silt to stabilize aeolian sand, which has significant advantages in terms of improved mechanical properties, environmental protection, and reduced project costs compared with traditional cement-stabilized aeolian sand. The results of this study have important theoretical and practical significance for the engineering and design of projects in aeolian sand areas.