Strategies for large-scale implementation of self-healing concrete using cementitious macro-capsules: an experimental study and economic assessment.

Self-healing technologies are increasingly being targeted by academic and industrial researchers for concrete applications because of their potential to actively repair the material when cracked, without the need for external intervention. In this sense, they could represent a decisive step toward addressing some of today’s greatest challenges: rethinking the entire life cycle of concrete materials starting from their durability, and achieving sustainability, quality, and cost-effectiveness. However, despite the promising results achieved in research, several obstacles remain for the on-site implementation of self-healing technologies, including cost uncertainties, site feasibility, and the transition to large-scale production. To explore possible pathways, this work identifies and compares three potential strategies for the use of cementitious macro-capsules, namely incorporating them into the concrete mix through: a) controlled placement, b) semi-controlled placement, c) random placement. Both technical performances and economic implications were evaluated by means of an ad-hoc experimental study and the relative cost analysis, respectively. Specifically, tests were carried out to characterize fresh and hardened properties of the mixes, capsule survivability during mixing and casting, and self-healing effectiveness (in terms of recovery of watertightness), in order to assess how different capsule incorporation methods influence their behavior and the overall technical performance of the material. An economic evaluation was also conducted to estimate the potential impact of this technology on the overall cost of the final product, identifying the threshold for it to be potentially competitive on the market. Experimental results showed that the capsules, as designed, successfully resisted the mixing and/or casting operations while still being able to break when required, without significantly affecting workability and inherent mechanical properties. Controlled placement of capsules ensured the best self-healing efficiency with an optimized use of material, while semi-controlled or random incorporation within the mix also provided significant benefits compared to not adopting the technology at all. From the economic perspective, a maximum unit cost for the capsules was estimated, and two scenarios of cost impact were proposed, showing how variations in unit price can determine which strategy is the most economically advantageous.