Abstract
abstract: As a solution to the high depletion of natural resources and huge waste generated by the construction industry, the use of coarse recycled aggregate has become a trend in many countries. The construction and demolition waste is heterogeneous and mostly composed of concrete and masonry debris. The recycling process usually involves not only crushing and screening but also advanced techniques to separate these two fractions. These processes are costly and most frequently ineffective. Although most studies and international standards focused only on recycled concrete aggregate for structural use, it is possible to achieve similar characteristics with mixed recycled aggregates that have a ceramic fraction of up to 20%. This initiative can decrease recycling costs and make it more feasible. Therefore, this work presents an experimental investigation of a Brazilian recycled aggregate, which was separated into three fractions: mixed, concrete, and masonry aggregates. The analyses showed that the mixed recycled aggregate displayed geometric, physical, and mechanical properties similar to the recycled concrete aggregate. In addition, concrete made with 20% of mixed recycled aggregate presented a reduction of only 0.6% in maximum compressive strength and 36.8% in the modulus of elasticity compared with concrete made with the same amount of recycled concrete aggregate.
Highlights
The construction industry is responsible for approximately 23% of global emission and demands around 4 x 1013 kg per year of raw material since aggregate typically accounts for approximately 70% of concrete in volume [1], [2]
Because of this heterogeneity, recycled aggregates are usually classified as Recycled Concrete Aggregate (RCA) when it is composed mostly of cement-based fragments and natural rocks, and as Mixed Recycled Aggregate (MRA) when it is composed of a mixture of ceramic debris, bricks, cladding, concrete blocks, and mortar
Similar results were obtained by Salles [35]: more than 90% of the final water absorption occurred in the first five minutes of testing for the three types of recycled aggregate analysed (MRA, recycled concrete aggregate (RCA) and recycled masonry aggregate (RMA))
Summary
The construction industry is responsible for approximately 23% of global emission and demands around 4 x 1013 kg per year of raw material since aggregate typically accounts for approximately 70% of concrete in volume [1], [2]. The use of recycled aggregate from CDW recycling as a replacement for natural coarse aggregate in concrete can promote a decrease in the number of irregular waste depositions but can reduce the consumption of non-renewable natural resources. In Brazil, for example, 70% of the recycling plants claim to receive predominantly mixed material [7], since wall portioning in most reinforced concrete buildings in Brazil have masonry and CDW collection is disorganized [9] Because of this heterogeneity, recycled aggregates are usually classified as Recycled Concrete Aggregate (RCA) when it is composed mostly of cement-based fragments and natural rocks, and as Mixed Recycled Aggregate (MRA) when it is composed of a mixture of ceramic debris, bricks, cladding, concrete blocks, and mortar. The impact of this substitution was evaluated through the analysis of the maximum compressive strength, the modulus of elasticity, and the behaviour of the stress-strain curve
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