#mining journal

Abstract

The recycling of Inert CDW in new concretes remains problematic. Only a part of this material can be used to substitute coarse aggregates in new concretes, mainly the liberated coarse aggregates from demolished concretes. This paper presents the processing of Inert CDW in air jigs aiming at concentrates with high concrete particle contents. The paper compares different studies carried out with laboratory air jigs aiming at a concentration of concrete particles, which can partially substitute coarse aggregates in new concretes.

Introduction

Nowadays, large quantities of CDW (Construction and Demolition Waste) are produced worldwide: European Union between 310 and 700 million tons [1], United States 145 million tons [2], China about 1 billion tons [3], etc. In Europe, this waste represents over 30% of all solid waste generated [1]. Current CDW processing plants only separate light materials (such as plastics, paper, wood, etc.) and metal parts (ferrous and non-ferrous) after their comminution [4-6]. The remaining material is known as Inert CDW and basically contains bricks, tiles, plaster, concrete, mortar and coarse aggregate [7-9]. The main uses of Inert CDW in terms of quantities are sub-base material for road works, drainage layers, concrete production as a paving block, etc. [10]. It is estimated that around 20% of Inert CDW can be used as coarse aggregate in the formulation of structural concretes [11] They are basically coarse aggregates from demolished concretes liberated by comminution, which can be separated and concentrated by gravity concentration processes. Thus, between 60 and 150 million tons can be generated in Europe alone each year. In Europe, more than 2,800 million tons of aggregates of all types [12] are produced annually, which could be partially replaced by concentrated Inert CDW. With this partial replacement, 2 major problems can be tackled: the use of part of the generated CDW and the production decrease of new aggregates [11,13]. Several publications present the use and characterization of coarse aggregates in construction engineering [14-17]. Knowledge of the physical properties of different demolished concretes is extremely important to enable their recycling [6]. Features such as particle liberation of different components by comminution, liberation of coarse aggregates from cement paste, density and porosity of individual particles, etc., allow the use of techniques for the separation and concentration of species that can be used as coarse aggregate in new concretes. One of these techniques derived from mineral processing is Air Jigging, also known as Pneumatic Jigging.

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