基于废弃超细砂的细粒混凝土性能试验研究

以航道整治工程废弃超细砂为主要原料,通过振动成型制备新型细粒混凝土替代普通混凝土。首先在固定水泥掺量下,基于干混试样最大堆积密度方法检测粉煤灰不同掺量对干混试样密度的影响,然后以试件7、14、28 d抗压强度、劈裂抗拉强度和浸水强度为控制标准,研究粉煤灰掺量对细粒混凝土性能的影响。结果表明:水胶比为0.38、减水剂掺量为0.45%情况下,细粒混凝土最佳配合比为废弃超细砂掺量66.8%、水泥掺量16.6%、粉煤灰掺量16.6%;采用最佳配合比所制细粒混凝土的28 d抗压强度、劈裂抗拉强度和浸水强度均达到最优。XRD分析表明制备的细粒混凝土含有大量的水化硅酸钙和钙矾石等水化产物。与普通C20混凝土相比,单方超细砂细粒混凝土生产成本降低45.1%。研究成果为废弃超细砂资源化利用提供了有效途径。

Experimental Study on Properties of Fine-grained Concrete Made from Waste Ultra-fine Sand

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.