To enhance the mechanical and durability properties of cement-fly ash stabilized aeolian sand and crushed stones, the synergistic optimization effects of basalt fibers and polycarboxylate superplasticizer were investigated. First, two full factorial experiments were conducted to evaluate the individual and combined effects of basalt fiber volume content and polycarboxylate superplasticizer mass content. Then, four mix proportions were selected to verify the durability optimization. Finally, SEM, EDS, and XRD were used to elucidate the underlying micro-mechanisms. The results indicate that the optimal combination was 0.1% volume content of 12-mm-long basalt fibers and 1.0% mass content of polycarboxylate superplasticizer, which yielded a compressive strength of 13.3 MPa and a splitting tensile strength of 1.14 MPa at 28 days. Compared to the control group and individual addition of basalt fibers or polycarboxylate superplasticizer, the group with both basalt fibers and polycarboxylate superplasticizer had 33.00%, 16.67%, and 14.66% higher compressive strength and 52.00%, 31.03%, and 28.09% higher splitting tensile strength, respectively. Furthermore, the combined optimization improved the durability, decreased the thermal shrinkage by 49.85%, 32.35%, and 28.84%, and decreased the drying shrinkage by 68.95%, 33.15%, and 47.58%. The micro-experiments demonstrate that the bridging effect of basalt fibers during micro-crack formation and the synergistic action of polycarboxylate superplasticizer enhanced the uniformity and density of the mixture and that they are the primary factors that contribute to the strength development. Therefore, cement-fly ash stabilized aeolian sand and crushed stones can be optimized by using basalt fibers and polycarboxylate superplasticizer.

This study investigates the strength and microstructural evolution of SRX-stabilized aeolian sand–gravel mixtures for flexible base applications in desert roads. CBR, UPS (uniaxial penetration strength), and compressive resilient modulus tests were conducted under varying SRX dosages (0.4–1.0%) and aeolian sand contents (30–50%). The results show that increasing the SRX dosage significantly improves all three indices, with the 0.5% SRX and 30% aeolian sand mixture yielding the CBR (385.89%) and UPS (0.938 MPa) and achieving a compressive resilient modulus that meets the requirements for graded aggregate base layers. XRD FTIR and SEM–EDS analyses reveal that the SRX enhances material structure primarily through physical mechanisms, forming dense films and bonding networks without inducing significant chemical reactions. Extended curing improves structural integrity, while excessive aeolian sand reduces compactness. SRX-stabilized aeolian sand gravel is a viable base and subbase material for desert highways.