Upgrading the Quality of Recycled Aggregates from Construction and Demolition Waste by Using a Novel Brick Separation and Surface Treatment Method.

Kui Hu,Shihao Cao,Yujing Chen,Rui Pang,Dong Xu,Caihua Yu

doi:10.3390/ma13132893

Abstract

Mixed recycled aggregates (MRA) from construction and demolition waste (CDW) with high-purity and environmental performance are required for highway construction application in base layer and precast concrete curbs. The main problematic constituents that reduce the quality level of the recycled aggregates applications are brick components, flaky particles, and attached mortar, which make up a large proportion of CDW in some countries. This paper studies the potential of brick separation technology based on shape characteristics in order to increase the recycled concrete aggregates (RCA) purity for MRA quality improvement. MRA after purification was also processed with surface treatment experiment by rotating in a cylinder to improve the shape characteristics and to remove the attached mortar. The purity, strength property, densities, water absorption ratio, shape index, and mortar removal ratio of MRA were studied before and after the use of the brick separation and surface treatment proposed in this study. Finally, the recycled aggregates upgradation solution was adopted in a stationary recycling plant designed for a length of 113 km highway construction. The properties of CDW mixed concrete for precast curbs manufacturing were conducted. The results indicate that problematic fractions (brick components, particle shape, and surface weakness) in the MRA were significantly reduced by using brick separation and surface treatment solution. Above all, it is very important that the proposed brick separation method was verified to be practically adopted in CDW recycling plant for highway base layer construction and concrete curbs manufacturing at a low cost.

Highlights

Construction and demolition waste (CDW) represent one of the largest waste streams worldwide because of continuous industrial development, the demolition of infrastructure, and house-building activities
The new brick separation technology and device developed in this study considered both quality upgradation of recycled aggregates and its practicality in production application
It can be concluded that the brick fractions can be reduced from 45 wt.%~55 wt.% to less than 15 wt.% after processed by brick separation technology adopted in this study

Summary

Introduction

Construction and demolition waste (CDW) represent one of the largest waste streams worldwide because of continuous industrial development, the demolition of infrastructure, and house-building activities. About 100 million tons of construction and demolition waste is generated from the new buildings, whereas, about 200 million tons of CDW is produced by demolition of old buildings in Shenzhen, China [1]. A large proportion of CDW was used or recycled at construction sites for low-grade unbound applications such as embankments, foundations, and landfills [3]. The largest recycled proportions of CDW are the stony fractions. A high recycling rate of mixed fractions of concrete, brick, mortar, and tiles was achieved in some countries, but CDW is mostly reused in low-grade applications such as nonstructural concrete mixtures, embankments, subbase, and road leveling [4,5]. Typical recycled components for civil engineering reuse in CDW are concrete and brick, which are generally believed to be a substitute for virgin natural aggregates in civil engineering [8]

Methods

Results

Conclusion