Diffusion-assisted fracture mechanism and linseed oil-effect in compacted waste sludge from paper industry
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Paper mill sludge (PMS) is a waste material produced in large amounts during the paper recycling industrial process. In some countries, landfilling still represents the most common end-of-life destination for PMS. Nevertheless, due to its granular nature, after compaction through mechanical pressure, it may constitute an alternative eco-friendly raw material to be employed as insulation panels for buildings' interspaces and walls. The present work describes the possibility of controlling the panels' thickness by exploiting natural linseed oil to perform successive compactions. In fact, the oil acts as a natural binder for each PMS layer interface, favoring particles' interaction and enhancing surface adhesion. The experimental tests are interpreted according to the phase field approach to fracture to simulate layers debonding. To investigate the degradation and wettability of PMS, which are crucial factors in understanding how the material response depends upon environmental moisture, a computational framework is also provided. In this regard, a water diffusion-assisted fracture mechanism leading to volumetric swelling in PMS specimens has been experimentally observed and numerically modeled within the phase field approach extended to deal with such a multi-physics scenario.