The utilization of rice husk ash in the production of high-strength concrete facilitates the sustainable recycling of this agricultural byproduct, and the mechanical properties of rice husk ash concrete are significantly influenced by the curing conditions. The impact of rice husk ash, either used singly or in combination with silica fume, on the mechanical and microstructural properties of ultra-high-strength concrete was systematically evaluated under various curing conditions, including standard curing, steam curing at 90°C, and dry heat curing. The experimental results showed that ultra-high-strength concrete incorporating rice husk ash exhibits favorable mechanical properties and microstructural features, and an increased proportion of rice husk ash substantially enhances the densification and uniformity of the concrete, enhancing the strength and durability of the concrete, and contributes to the broader application of rice husk ash concrete in civil engineering infrastructure.