Abstract: The size and shape of recycled aggregate particle determine whether the recycled concrete mixture can be closely combined, thus achieving a good forming effect. Specific surface area and shape index are used to reflect the mixing performance of recycled aggregate. By preparing recycled aggregates with particle size of 4.75-9.50 mm and 9.5-19.0 mm by waste pavement concrete, we measured the specific surface area of recycled aggregate through theoretical calculation and net slurry test method; in the meantime we also measure the shape index of recycled aggregate via the shape evaluation method for coarse aggregate, and finally assessed the performance of recycled aggregate. Results demonstrate that the surface of recycled aggregate is rough with many particle edges and corners. The specific surface area of 4.75-9.50 mm and 9.50-19.00 mm recycled aggregate is 5.98 cm²/g and 4.19 cm²/g, respectively, which are higher than the specific surface area of gravel and pebble aggregate; the shape index is 0.172 7 and 0.246 6 respectively, which is inferior. Therefore, aggregate with sphere particle shape and high shape index should be selected for recycled aggregate. The research finding offers a reference for the promotion and utilization of recycled aggregate in practical engineering.

Key words: recycled aggregate, specific surface area, shape index, needle and flaky particles, particle sphericity