再生骨料比表面积和形状指数测定方法计算与分析

再生骨料颗粒形状和大小决定了再生混凝土拌合物是否能够紧密结合、能否达到良好的成型效果,一般以比表面积、形状指数来反映其拌和性能。通过选用废弃路面混凝土制备出4.75~9.50 mm和9.50~19.00 mm粒径的再生骨料,用比表面积理论计算和净浆试验法进行再生骨料比表面积测定,以粗骨料颗粒形状评定方法对再生骨料形状指数进行测定,最终对再生骨料拌和性能作出评判。研究发现:再生骨料表面粗糙,颗粒棱角较多,4.75~9.50 mm和9.50~19.00 mm粒径的再生骨料比表面积分别为5.98 cm²/g和4.19 cm²/g,均高于碎石、卵石骨料的比表面积;其形状指数分别为0.172 7和0.246 6,颗粒形状不好。因此,再生骨料要选用颗粒形状接近球体、形状指数高的骨料。研究结果为实际工程中再生骨料的推广和利用提供了参考。

Determining Specific Surface Area and Shape Index of RecycledAggregate: Calculation and Analysis

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.