CHARACTERISTICS OF PROCESSED CONCRETE RUBBLE

The generation of building waste in the Eastern Germany region, with 2,5 Mio inhabitants amounts about 3 Mio tons per year. Approximately, half of this amount is processed at the recycling plants to produce recycled aggregates. Although stationary recycling plants offer the better conditions for the production of aggregates which meet high quality standards, mobile plants are predominant in the tested region.

The results of material tests on a large number of samples from different stationary recycling plants show that the processed concrete rubble is a relatively pure material. The particle size distribution mostly meets the requirements of the aggregate grading curves. The bulk density ranges from 1,86 g/cm³ to 2,33 g/cm³. Only 3 of the 13 tested samples lie below the required limit for the bulk density of 2,0 g/cm³. A strong dependence between the grain size and the bulk density was found being typical for all recycling products. During the crushing process the weakest bond or the material with the lowest strength was broken, for instance the interface between mortar and brick in masonry, the interface between cement paste and aggregate in concrete or the cement paste itself. This results in a concentration of the cement paste in the fine fraction and in a decrease of the bulk density.

Effects of the comminution on the micro-structure of the concrete aggregates may exist. First results show a higher total porosity of granulates produced in a jaw crusher compared with the products of an impact crusher. The formation of additional pores with diameters of about 1 μm may be the reason.

• ABSTRACT

• INTRODUCTION

• OVERVIEW OF PROCESSING TECHNOLOGIES

• PROPERTIES OF AGGREGATES OF CONCRETE RUBBLE

• REFERENCES