Silica fume for cross valley bridge UHPC can be used as an additive in the construction of bridges across valleys.silica powder for UHPC plays a role in improving the strength of UHPC from two aspects: one is because of the microfilling effect produced by its own fine particles, microsilica particles filled in the pore space and larger cement particles, reducing the number of macropores in the matrix, optimising the grading of the cementitious material, and strengthening the compactness of the system; the second is that silica fume's volcanic ash effect, which alters the hydration process of the cementitious component of the UHPC, and reduces the strength of weak Ca(OH)2, resulting in significant increase in the content of the generated C-S-H gel material. ) 2, so that the generated C-S-H gel material content was significantly improved. Figure 4 shows the effect of silica fume dosing on the compressive strength of 52.5 grade silicate cement matrix. The matrix compressive strength…