Self-healing of cementitious materials via embedded macro-capsules

Concrete is the most widely used construction material in the building and civil infrastructure fields. However, its high sensitivity to crack formation leads to a severe reduction of durability and to an increase of the overall life cycle cost due to both maintenance expenses and loss of serviceability during the repair works. To deal with this problem, a growing attention has been devoted in the last decades to the development of proper technological systems aimed to introduce self-healing properties in the concrete. In the present work, some experimental results on the use of embedded macro-capsules filled with foaming polyurethane precursor are presented. The self-healing efficiency was assessed in terms of durability increase and strength regain after pre-cracking in three-point-bending. The increased durability was evaluated in terms of sealing efficiency during water permeability and absorption tests. The strength regain was evaluated after reloading in three-point-bending. Promising results were achieved: a substantial tightness and strength recovery was observed, even in specimens presenting large crack widths, suggesting that the proposed self-healing system can be effective in prolonging the material functionality. Further research is needed to test the efficacy of the proposed solution under different testing protocols, with a view to a final scale-up.