Abstract: Waste ultra-fine sand from waterway regulation project was used as main raw material to prepare fine-grained concrete by vibrating forming. An initial study on the effect of fly ash proportion on the packing density of dry mix of fine grained concrete was conducted by the method of maximum packing density of the dry mix, then the compressive strength, tensile strength and compressive strength after immersion at 7-d, 14-d and 28-d ages were tested to determine the influence of fly ash content on the performance of fine grained concrete. Result manifests that the optimum mixing ratio of this fine grained concrete is 66.8% waste ultra-fine sand, 16.6% cement, and 16.6% fly ash with water/binder ratio of 0.38 and water reducing agent dosage of 0.45%. The 28-d compressive strength, tensile strength and compressive strength after immersion of the fine grained concrete with this mixing ratio reach the optimum. X-ray diffraction(XRD) analysis shows that the prepared fine concrete contains a lot of hydrated products such as hydrated calcium silicate and ettringite. Compared with C20 concrete, the production cost of fine grained concrete reduced by 45.1%. The study provides a technical approach for the utilization of waste ultra-fine sand.

Key words: fine-grained concrete, fly ash proportion, waste ultra-fine sand, mechanical properties, optimum mix ratio