Una metodologia sperimentale per valutare la capacità di autoriparazione di calcestruzzi con additivi aerocristallizzanti

The self-healing capacity of cementitious composites employed for either new or repairing applications opens challenging perspectives for the use of materials intrinsically able to recover their pristine durability levels, thus guaranteeing a longer service life of the designed applications and a performance less sensitive to environmental-induced degradation. One possibility of achieving the aforementioned self-healing capacity stands in the use of additives featuring a “delayed crystalline” activity, which, when in contact with water or atmosphere humidity, form chemical compounds which are able to reseal the cracks thus guaranteeing the partial recovery of the pristine mechanical performance. In order to quantify this self-healing capacity and its effects on the recovery of mechanical properties of the material, a methodology has been developed and will be presented in this paper. The method starts with pre-cracking, up to different crack opening levels prismatic beam specimens (a three point bending scheme with COD measurement has been employed in this study), made with concrete, both added or not with the aforementioned additives. Specimens are then submitted, for different exposure times, to accelerated temperature and humidity cycles, which may be chosen as representative of climate conditions relevant to the intended application. Finally, three point bending tests are performed once again on the same “conditioned“, either uncracked or pre-cracked specimens, and results, in terms of load-COD curves, are compared with those obtained from virgin specimens before any “conditioning”. This allows crack “self-closure” to be evaluated and “self-healing” indices to be defined and correlated, e.g., to the load-recovery capacity.