Demolished concretes recycling by the use of pneumatic jigs

• Published in: Waste management & research Vol. 38; no. 4; pp. 392 - 399
• Main Authors: Hoffmann Sampaio, Carlos, Cazacliu, Bogdan G, Ambrós, Weslei Monteiro, Kronbauer, Márcio André, Tubino, Rejane MC, Dal Molin, Denise CC, Oliva, Josep, Miltzarek, Gérson L, Waskow, Regis P, dos Santos, Viviane LG
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.04.2020; Sage Publications Ltd
• Subjects: Aggregates; Concrete; Construction; Construction Materials; Demolition; Density; Density distribution; Fines; High strength concretes; Industrial Waste; Jigging; Jigs; Landfills; Low resistance; Metals; Particle density (concentration); Particle size distribution; Recycling; Size distribution; Waste disposal; Waste disposal sites; Waste Management; construction and demolition waste; Concrete recycling; pneumatic separation; waste recycling; air jigging
• ISSN: 0734-242X; 1096-3669
• DOI: 10.1177/0734242X20902835

Large quantities of construction and demolition waste is generated annually around the world. Part of this material is processed in recycling plants. After removing metals, fines and lights, the construction and demolition waste is crushed and sized and can be used as aggregates for low resistance concrete, for road sub-base, city landfill and other low value-added applications. For their use as coarse aggregate in structural concretes, construction and demolition waste must exhibit high densities and regularity of the material. This material usually is presented in demolished concretes. About 20% of the particles from demolished concretes can be used as coarse aggregates substituting part of natural aggregates in structural concretes. This article presents studies of demolished concretes recycling by the use of a pneumatic jig. All jigging tests were carried out with three different concretes produced in three strength classes: C16/20, ordinary concrete; C50/60, high strength concrete; and C70/85, very high strength concrete. Based on density distribution of the three concretes, there are reasonable masses with densities over 2.7 g cm−3, particle density considered appropriate to the used as coarse aggregate for structural concretes. The concretes present different mass recoveries of the denser particles (different liberation). Coarse aggregates can be recovered with reasonable masses by the use of air jigs: About 65% for high strength concretes and about 75% for the low strength concrete. The jigging concentration efficiency depends on the concrete liberation, density and size distribution.