On the classification of mixed construction and demolition waste aggregate by porosity and its impact on the mechanical performance of concrete |
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Authors: | S C Angulo P M Carrijo A D Figueiredo A P Chaves V M John |
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Affiliation: | 1.Instituto de Pesquisas Tecnológicas do Estado de S?o Paulo,Cidade Universitária,S?o Paulo,Brazil;2.Department of Construction Engineering, Escola Politécnica,University of S?o Paulo,S?o Paulo,Brazil;3.Department of Mining Engineering, Escola Politécnica,University of S?o Paulo,S?o Paulo,Brazil |
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Abstract: | The properties of recycled aggregate produced from mixed (masonry and concrete) construction and demolition (C&D) waste are
highly variable, and this restricts the use of such aggregate in structural concrete production. The development of classification
techniques capable of reducing this variability is instrumental for quality control purposes and the production of high quality
C&D aggregate. This paper investigates how the classification of C&D mixed coarse aggregate according to porosity influences
the mechanical performance of concrete. Concretes using a variety of C&D aggregate porosity classes and different water/cement
ratios were produced and the mechanical properties measured. For concretes produced with constant volume fractions of water,
cement, natural sand and coarse aggregate from recycled mixed C&D waste, the compressive strength and Young modulus are direct
exponential functions of the aggregate porosity. Sink and float technique is a simple laboratory density separation tool that
facilitates the separation of cement particles with lower porosity, a difficult task when done only by visual sorting. For
this experiment, separation using a 2.2 kg/dm3 suspension produced recycled aggregate (porosity less than 17%) which yielded
good performance in concrete production. Industrial gravity separators may lead to the production of high quality recycled
aggregate from mixed C&D waste for structural concrete applications. |
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