Foam-bonding process for granular wastes – BONDINGFOAM

One of the key stages in materials recycling is their crushing into granular material to be re-used by incorporation into the production lines of new objects. In a certain number of cases however, simple shaping using a binder, and a possible post-treatment of the peripheral surfaces, would make it possible to produce objects with a useful purpose (blocks for urban furniture and for construction). Our proposal is that complex liquid foam (liquid foam loaded with a binding component) represents a first-choice low carbon binder precursor to be pushed through the voids offered by a packing made with such grains, to give shape to the whole and to confer significant mechanical strength. The low binder content of the foam is an obvious advantage, but not the most important one: we have recently shown that in such a foam-grain system, liquid bridges are formed at the contacts between adjacent grains. This location induced by capillary forces would allow the binder to be deposited exactly where it is needed, rather than filling the entire pore space with it. The objectives of this project are: (1) to demonstrate the feasibility of the foam bonding process; (2) to identify the ways to optimize the process; (3) to highlight the potential advantages of this bonding process. We propose to focus our experimental and numerical studies on several points identified as potential critical issues to be solved in order to implement the process: the transport of complex liquid foam trough granular packings, the aging of the foam confined into porosities before the binder solidification, the mechanics of foam-bonded granular packings. Significant work will be done to determine by R-rays tomography the microstructure of the complex foam confined into the porosity of a granular packing, during solidification and once the material has solidified. A concrete case of application of this process will be implemented in a particle-bed 3D printing configuration.