The Properties of Hardened Concrete with Different Dosages of Recycled Concrete Aggregates

Research in the field of recycled aggregate reuse in load-bearing structures is essential, as is the increase in awareness of the impact of construction on the environment. Using secondary raw materials also reduces landfilling and rock mining, and, from a practical point of view, this practice provides new materials for concrete. In this paper, the effect of using recycled aggregate concrete (RAC) on the basic properties of standard concrete is studied. Three types of concrete were studied: natural aggregate concrete (NAC) and two mixtures with 50 % and 75% replacement of natural coarse aggregates by recycled concrete aggregate. Results showed that using recycled aggregates reduces the mechanical properties of hardened concrete. The different properties of hardened concrete with a rate of recycled aggregate also impact the design process of the load-bearing structures of the buildings. The standard regulations in Slovakia allow using recycled concrete aggregate for up to 55% of all aggregates, but many designers do not trust this material. However, we cannot avoid using secondary raw materials in designing new structures in the future. The knowledge of recycled aggregate concrete presented in this paper provides directions for research and the concrete industry to focus on sustainable concrete products systematically.