Re-use of recycled concrete sand fraction

These investigations relate to the development of alternative possibilities for the recycling of concrete sand of 0/4 mm grain size. Laboratory standard tests and the results achieved are reported. Full quality sections of scrap concrete sand of different origin are examined as a reference case. Here one deals in particular with the specifications of this sand, which contains transformation capable stages in addition to inert ones. The investigations then have three focal points. As a first reuse possibility, the thermal reactivation of the concentrated cement stone to a hydraulic binding agent is proved. As a second utilization possibility, investigations are carried out for use as a secondary binding agent. Ground scrap concrete sand was added to cement, and the qualitative characteristics of the cement mix have been tested. No participation of the scrap concrete flour on stability formation could be proved, but a significant improvement in the workability of green mortars was demonstrated. The third utilization possibility for recycled concrete sand results from its chemical analysis. The chemical composition shows similarities between scrap concrete sand containing siliceous aggregates and that from magmatic rocks which is used in the production of mineral insulants. Investigations for sintering and melting behaviour showed, for instance, that the temperature of the start of softening of the concrete sands matches that cf the insulants of mineral threads. However, the melting range is far broader. But it is found to be influenced by the addition of other components taken from building waste, such that a melting behaviour similar to that of mineral threads results. Results are presented for the investigations for use as a secondary binding agent and as a raw material component for mineral insulants.

• 1 INTRODUCTION

• 2 INVESTIGATIONS FOR USE AS A SECONDARY BINDING AGENT

• 3 INVESTIGATIONS FOR USE AS A RAW MATERIAL COMPONENT FOR MINERAL INSULANTS

• REFERENCES