Fresh State Properties of Self-Compacting Concrete Using Recycled Aggregates

Self compacting concrete (SCC) is concrete that does not require vibration for placing .It consists of same components as conventionally vibrated concrete which are cement, aggregates and water in addition to mineral and chemical admixtures. This research focused on the fresh state properties of self compacting concrete using recycled aggregates wastes from constructed and demolished structures. Recycled coarse aggregates used in the production of the concrete was in varying percentages of 0%, 20%, 40%, 60%, 80% and 100% as replacement of natural coarse aggregates by volume. Portland cement of 42.5N conforming to BS12 (1996) and superplasticizing admixture was used to maintain a slump of 75mm in all the six mixes used. All mixes exhibited slump flow in the range of 620 – 770mm which ranked them in the SF1 and SF2 slump flow class under EFNARC guidelines. T50 slump flow was between 2.08secs to 3.15secs categorized under vicious flow (VF2) class. V-funnel time was from 6 – 10 secs which is considered adequate under VF1 class while the L-box test was not less than 0.8 indicating deformability and segregation resistance. Self-compacting concrete made with recycled aggregates have achieved the target strength in all the mixes and also satisfied the fresh state properties required for SCC as per EFNARC specification. The work undertaken has demonstrated the suitability of recycled coarse aggregate s(RCA) for use in a range of normal grade concrete applications. Indeed, the results have shown that up to 30% RCA can be used, without any modification in the mix design, in concrete construction with performance similar to natural aggregate concrete