Abstract:
The subject of concrete recycling is crucial in the general attempt for sustainable development. Although there have been extensive research and positive experience on the use of recycled aggregate (RA) from concrete waste for new concrete production, the concept of recycling construction and demolition (C&D) waste has limited practice in Ethiopia. The main reason for this is the lack of confidence and/or knowledge on how concrete waste can be recycled into new concrete constitute or other construction material use. Besides, there are only few studies carried out in Ethiopia which investigated the potential use of recycled concrete aggregate (RCA) for new concrete production. Keeping this in mind, this study investigates the impact of new aggregate replacement method on workability and compressive strength of recycled aggregate concrete (RAC). Eight concrete specimen type including the control mix were prepared with a constant water-cement ratio of 0.49 and a design slump between 75-100 mm for concrete having a target 28-day compressive strength of 25 MPa. Seventy-two (72) concrete cubes (150mm×150mm×150mm) were casted and tested. The workability of each fresh concrete mix was checked via slump test immediately following mixing, while the compressive strength was determined after curing for 3, 7 and 28 days in a curing bath. Five recycled concrete aggregate (RCA) replacement percentages (i.e., 0%, 25%, 50%, 75% and 100%) were considered. The mixes that incorporate RCA are prepared with both the conventional replacement and the new replacement method. The results show that the new replacement method enhances the workability of recycled aggregate concrete compared to the conventional method. A 18%, 20% and 25% increase in slump value was observed at 75%, 50% and 25% replacement respectively. Whereas, no significant difference in compressive strength was obtained between mixes prepared with the two replacement methods.