Concrete, a mixture of water, cement and aggregates (both fine and coarse) is currently the main material used in construction in Kenya. Elements such as slabs, beams and columns are made of concrete. Since the beginning of the new millennium, Kenya has undergone rapid urbanization, specifically in major cities, and construction of mega structures is a major feature. It is the demolition of the old structures in these areas that forms the main basis of this paper. Very little demolished concrete, if any, is recycled. These wastes are used in landfills or dumped in garbage sites. Furthermore, lack of dumping sites within major cities as well as difficulty in getting the raw materials creates the need to reuse this waste concrete. This paper shows a comparative analysis of experimental results to evaluate the effect of replacing the raw materials in different proportions. The compressive strengths were tested at 7 and 28 days and workability determined. Reusing of waste concrete in construction of structures is cost effective and meets the required strength parameters set when mixed in the correct proportions. This may well be a major change in the construction industry in Kenya.