Capacità di autoriparazione dei compositi cementizi fibrorinforzati ad elevate prestazioni

In this paper the results are shown of a thorough characterization of the self-healing capacity of High Performance Fiber Reinforced Cementitious Composites (HPFRCCs). In detail, the capacity of the material will be investigated to completely or partially re-seal cracks, as a function of its composition, maximum crack opening and exposure conditions. Challenging perspectives could be foreseen for the use of a material not only intrinsically more durable but also able to recover its pristine durability levels, thus guaranteeing a longer service life of the designed applications and a lower sensitiveness to environmental induced degradation. This also implies a new structure concept and a wider worthiness of the sustainability of engineering applications which can be achieved thanks to the use of HPFRCCs, which overcomes and encompasses the traditional one related to the use of by-products, which can anyway be effectively pursued also in this case. The topic has been investigated including the effect of different flow-induced alignment of fibres, which can result into an either a strain hardening or softening behaviour, whether the material is stressed parallel or perpendicularly to the fibres. Specimens were initially pre-cracked in 4-point bending and up to different values of crack openings, and submitted to different exposure conditions, including water immersion, exposure to humid or dry air, and wet-and-dry cycles. After scheduled exposure times, speci-mens were tested up to failure according to the same test set-up and outcomes of the self-heal-ing, if any, were quantified in terms of recovery of stiffness, strength and ductility. In a durability-based design framework, self-healing indices to quantify the recovery of mechanical proper-ties were also defined and their significance checked.