Recycled Concrete Aggregate as Part Replacement of Natural Coarse Aggregate

This research attempts to determine the percentage of recycled concrete aggregate that will be acceptable for blending as part replacement of natural coarse aggregate in the production of concrete. The result for the sieve analysis carried out for the fine sand showed that the soil was well graded, as the aggregates fell within the upper and lower limits of the grading requirement. The natural coarse aggregate was also well graded while sieve analysis for the recycled aggregate was closely graded because the particles were about the same size. The specific gravity for the fine sand used was 2.84 while that of the natural concrete aggregate was 2.43 and recycled aggregate concrete was 2.21. The water absorption for natural concrete aggregate was 32.2 while for recycled concrete aggregate it was 38.9. The slump obtained from a w/c of 0.5 for natural concrete aggregate was 0.7mm while the slump of recycled aggregate concrete ranged from 0 – 13mm for different percentages of blending the recycled aggregate concrete with natural concrete aggregate. The concrete produced from 100% natural concrete aggregate had a maximum compressive strength of 39.1mpa at a curing age of 7days and 34.7mpa at a curing age of 14days and 25.8mpa at a curing age of 28days. The compressive strength of concrete produced with blending of recycled aggregate concrete with natural aggregate concrete from varying percentages ranges from 5.3 to 41.8mpa. The use of recycled aggregate concrete will reduce dumps and thus a cleaner environment.