Mix design of recycled aggregate concrete using packing density method

Packing density method is new kind of mix design method, generally used for design normal, highstrength and self-compacting concrete. This method considers the volume and density variation between different types and sizes of aggregate. The adoption of packing density method optimises the particle packing density of concrete by selecting the right amount of various aggregates to fill up the voids between large and small aggregates, which allows a more dense and stiff structure. This paper is devoted to the studies of material and mechanical properties of recycled aggregate concrete using packing density method. This paper considers mix of two different aggregate sizes of 10 and 20mm, 0, 30, 50, 70 and 100% recycled aggregate replacement ratios, and water-cement ratio of 0.35, 0.45 and 0.55. In total of fifteen concrete mix designs are considered. The paper presents the material properties of aggregates which were obtained from the material testing. The mix design method and results of mechanical testing will be discussed. The results show that the packing densities of natural and recycled aggregates are different, and should not be treated in the same way. By using packing density mix design method, recycled aggregated concrete strengths fluctuation can be resolved, and the concretes can have similar strengths consistency, regardless the recycled concrete aggregate replacement ratios. This method minimise the influence of recycled concrete aggregates obtain from various sources with variable quality.