CLOSING THE CONCRETE LOOP – FROM REUSE TO RECYCLING

This presentation deals with a pre-feasibility study of the production of secondary aggregate and hardened cementstone by separation of used concrete. It will be shown that concrete can easily be separated into two main fractions: the fraction +150μm consists mainly of sand and gravel, while the fraction −150μm consists predominantly of hardened cementstone. The small-scale separation technology investigated consists of a wellbalanced stepwise heating-desagglomeration-sieving treatment. Both fractions have been tested for reuse. The coarse fraction as concrete aggregate, the fine fraction as cement constituent. In both cases laboratory tests yielded promising results.

The full process has been evaluated using the well-known Life Cycle Assessment methodology. In this study the LCA focussed on energy consumption, CO₂-emissions, the use of primary raw materials and the prevention of waste. Preliminary results indicate that the separation technology investigated enables us to close the concrete loop. Of course, further optimisation of process details and process organisation will be needed.

The structure of the presentation will as follows:

1. Current application of recycled concrete in the Netherlands

2. Separation technology for used concrete

3. Reuse and performance of the coarse aggregate fraction in concrete

4. Reuse and performance of the fine cementstone fraction as cement constituent

5. Life cycle assessment with respect to energy use, CO2-emissions, use of primary raw materials and waste prevention

6. Conclusions and recommendations

• ABSTRACT

• INTRODUCTION

• SEPARATION OF CONCRETE INTO ITS CONSTITUENTS

• PRE-FEASABILITY STUDY

• ENVIRONMENTAL PRE-FEASIBILITY

• CONCLUSIONS AND RECOMMENDATIONS

• ACKNOWLEDGEMENTS

• REFERENCES