废弃混凝土再生微粉掺量与粒度等级对胶砂试件力学性能的影响

Influence of content and size grade of waste concrete recycled powder on mechanical properties of cement sand specimens

废弃混凝土在破碎制备再生骨料的过程中会产生许多粒径在0.16 mm以下的细小颗粒,称为微粉。这些微粉主要为混凝土中硬化的水泥石破碎时形成的,其具有一定的活性。将废弃混凝土微粉进行再生利用对减轻环境污染和节约成本具有重要意义。从废弃混凝土再生微粉的掺量和粒度等级角度研究了对胶砂试块强度的影响,以期指导工程实际应用。研究结果表明,在再生微粉细度不变的情况下,随着再生微粉掺量的增加,胶砂试件3 d的抗折强度和抗压强度均呈现先升高后降低的趋势,7、28 d的抗折强度和抗压强度均呈现递降的趋势,当再生微粉掺量为10%时,可有效提高胶砂试件的早期强度,综合考虑对各龄期力学性能的影响,最佳掺量为10%;当再生微粉掺量为10%时,对于50~160、5~50、<5μm这3种不同的粒度等级的再生微粉,粒径<5μm的活性高,有利于提升胶砂试件的强度。

In the process of crushing waste concrete to prepare recycled aggregate,many fine particles with particle size below 0.16mm will be produced,which are called recycled powders,these powders are mainly formed when the hardened cement stone in concrete breaks down,it has some activity.It is of great significance to recycle waste concrete powder to reduce environmental pollution and save cost.It studies the influence of recycled powder of waste concrete on the strength of cement sand specimens from the perspective of content and size grade order to guide the practical application of the project.The results show that with the constant fineness of the recycled powder,the content of the recycled powder increases,the flexural strength and compressive strength of the 3 d cement sand specimens showed a trend of first increasing and then decreasing,the flexural strength and compressive strength of 7 d and 28 d showed a decreasing trend.When the regenerated powder content is 10%,the early strength of the cement sand specimens can be effectively improved.Considering the influence on the mechanical properties of each age,the optimal content is 10%.When the content of the recycled powder was 10%,the activity of the recycled powder with particle size<5μm was highest in the recycled powder with particle size 50~160μm,5~50μm and<5μm,which was helpful to improve the strength of the cement sand specimens.