Study on Recycled Concrete Powders as Mineral Admixture in Recycled Concrete

Abstract

The process of recycling waste concrete generated fine powders with a particle size of less than 0.16mm; it contains a large amount of hardened cement and unhydrated cement and has high activity. In order to meet the requirement of sustainable development in concrete industry, this study aims to improve the recycle use level of these fine powders in concrete. First, the properties of the recycled concrete powder were analyzed, and compared with one normal mineral admixture such as fly ash. Then the workability and compressive strength test of the concrete which mixed by different replacement ratio of the recycled concrete powder and fly ash were performed. The results show that the the content of SiO2 in recycled concrete powder is more than cement and fly ash. The replacement rate of RCP has little influence on the slump of fresh recycled concrete compared to fly ash. When the replacement rate of the recycled concrete powder is 20 %, the compressive strength of corresponding concrete at each age is close to that of control concrete, especially at 56d, the compressive strength of concrete reach to 90% of that of control concrete. So the application of the recycled concrete powder can save cement and has certain environmental and economic benefits.