Cement-based materials, including mortar and concrete, are the most used construction materials in the world. They account for 5-8% of global CO2-emissions, and targets have been set to reduce these emissions. This study was conducted to investigate whether concrete can be recycled as a binder or filler to help reduce emissions.To assess whether recycled concrete can be used as a binder or filler, well-hydrated concrete cubes were crushed and ground into fine powder, and new mortar prisms were cast with 10 wt.%, 20 wt.%, and 40 wt.% replacement of cement by recycled concrete [RC] fines. These prisms were tested for compressive and flexural strength and compared to a reference containing 100 wt.% cement. The same mixes were used in heat development tests conducted in an isothermal calorimeter.The test results indicated that the recycled concrete fines contributed to some extent to the heat development. However, it could not be determined whether this was due to the RC fines acting as a filler by accelerating the reaction of cement, or if it was binding reaction of its own.From the strength tests, it was observed that compressive strength decreased proportionally to the replacement of cement by RC fines. However, the difference from the reference decreased as the curing time increased, indicating that the recycled concrete might react more slowly than cement. Additionally, it was found that the difference in performance between using concrete from C30/37 and C40/50 strength classes was minimal.The recycled concrete powder produced is heterogeneous, meaning that different batches may contain varying amounts of unhydrated cement when incorporated into new mortar mixes. To increase the proportion of unhydrated cement cores in the material, the recycled concrete should ideally be separated into binder paste and aggregate.