Large quantity of construction and demolition waste has been produced due to therneconomic growth of the world. However, the most common way to dispose of such wasternis by landfill. Without proper sorting and handling of it, as time passes, landfills will causernmany environmental issues. Furthermore, the continuous utilization of natural aggregatesrnwill cause resource scarcity. The potential solution for these problems is the recycling ofrnaggregates. Still, due to strength reduction associated with recycled aggregates, its usagernis restricted for low strength concrete. rnOn the other hand, incorporation of metakaolin as a cement replacement in recycledrnaggregate concretes could pave a path towards a sustainable future. In addition, kaolin, thernoriginal material from which metakaolin is produced, is found in large quantities inrnEthiopia which makes it an attractive option. rnThis research presents the effect of metakaolin as a cement replacement on the propertiesrnof fresh and hardened recycled coarse aggregate concrete as well as natural coarsernaggregate concrete. The recycled coarse aggregate is extracted from first-hand castrnlaboratory cubes with known average compressive strength. Different types of concreternmixtures are tested: concrete made with natural coarse aggregate as a control concrete,rnconcrete made with recycled coarse aggregate (0%, 25%, 50%, 75% and 100%rnreplacement of natural coarse aggregate), concrete made with metakaolin as cementrnreplacement (0%, 6%, 12%, 18%, and 24% replacement of cement), and concrete madernwith recycled coarse aggregate (0%, 25%, 50%, 75% and 100% replacement of naturalrncoarse aggregate) with metakaolin as cement replacement (6%, 12%, and 18%rnreplacement of cement). Additionally, a separate experiment has been conducted to checkrnthe production of metakaolin from locally found kaolin samples. rnThe outcomes of this research show that the use of metakaolin as a cement replacementrnimproved the compressive strength of recycled coarse aggregate concrete and evenrnresulted in a compressive strength almost equal to natural coarse aggregate concrete. Inrnaddition, this thesis has shown that metakaolin can be produced from locally occurringrnkaolin by thermal activation.