An experimental methodology to assess the self-healing capacity of cementitious composites with “aero-crystallizing” additives

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 addi-tives featuring a “delayed crystalline” activity, which, when in contact with water or atmosphere humidity, form chemi-cal 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 ability and its effects on the recovery of mechanical properties of the material, a methodology has been developed and will be presented in this paper. It consisted in pre-cracking up to different crack opening levels (a three point bending scheme with COD measurement was employed) prismatic beam specimens, made with both concrete added or not with the aforementioned additives. Specimens were then submitted to accelerated temperature and humidity cycles, representative of autumn climate conditions in northern Italy, for dif-ferent exposure times. Finally, three point bending tests were performed on either uncracked or pre-cracked speci-mens and results, in terms of load-crack opening curves, were compared with those obtained from virgin specimens before any “conditioning”. This allowed crack “self-closure” to be evaluated and “self-healing” indices to be defined and correlated, e.g., to the load-recovery capacity.