RECYCLING METHODS FOR STEEL FIBER REINFORCED CONCRETE

Abstract

The favorable impact of steel fibers in concrete is well known. Steel fibers can affect various fresh and hardened properties of concrete, for instance the appearance and propagation of cracks in the concrete matrix. Thus far, extensive research has been conducted to describe and to analyze those phenomena. Furthermore, Steel Fiber Reinforced Concrete (SFRC) is state of the art and is used extensively in industrial floors, walls, and ceiling constructions. But, beside the beneficial impact, the recycling of SFRC and, in particular, the separation of crushed concrete and steel fibers should be focused too. Only a few research programs are described in literature and comprehensive suggestions or guidelines are missing completely. So, a first test program was carried out to evaluate the usual procedure to break the concrete with a jaw crusher and to separate the contained steel via magnet. In tests, the amount and the type of the fibers used were varied as well as the concrete strength. The tests suggest that a certain amount of fibers can be separated, but the majority of fibers is still bound to the crushed concrete. Via sieving, it is possible to further separate concrete still containing fibers from aggregates without fibers. Conglomerates of broken concrete and fibers may be crushed again afterwards, but, allegedly, the success of the described procedure strongly depends on the fiber amount and the concrete properties. Furthermore, the available test data is too small to sufficiently describe the entire recycling path, making further research inevitable.