Self-Healing Concrete: Innovating Concrete Repair

BESIX is actively taking steps to make a positive environmental impact by contributing to investigations of new material developments. One of the latest initiatives is the participation in the research project SMARTINCS on self-healing concrete. As an industrial sponsor, BESIX Engineering plays a crucial role in the SMARTINCS project, collaborating with Ph.D. Researcher Yasmina Shields from Ghent University.

Funded by the EU Horizon 2020 research and innovation program, the SMARTINCS project aims to incorporate life cycle thinking into the execution of concrete structures. By integrating self-healing materials, this initiative seeks to prolong the service life of concrete projects while reducing maintenance and repair costs, as well as the need for demolition and reconstruction.

BESIX’s contribution

As an industrial sponsor, BESIX provides researchers with the opportunity to test self-healing repair methods under real job site conditions and evaluate construction procedures. Nine trial concrete walls, 2m² and 10cm thick, were constructed on the Henneaulaan bridge site in Zaventem, adhering to authentic job site execution conditions. The selection of this site was based on the availability of necessary formwork materials and convenient concrete delivery.

To assess the effectiveness of self-healing, deliberate efforts were made to induce cracks in the concrete walls during the construction process. Techniques typically avoided in construction, such as excessive cement usage, insufficient reinforcement, absence of horizontal reinforcement, rapid formwork removal, and unfavourable building conditions, were implemented.

Yasmina Shields: “I express my deep gratitude to BESIX for not only locating the site but also providing the necessary resources and skilled workforce for this project. This truly exemplifies BESIX’s unwavering dedication to exploring every avenue in the pursuit of sustainability.”

The self-healing technique

The self-healing system involves a network of polymeric tubes fixed to the steel rebars before concrete casting operations. The vascular network system is partially fabricated using a 3D printer and extruded tubes. The tubes have pre-perforated holes covered with gelatine. The gelatine dissolves during concrete curing. The accessible ends of the tubes outside the concrete element allow for the injection of self-healing products in these tubes after hardening. The injection products then distribute through the holes within the concrete and filling the cracks.

Vascular networks placed on the reinforcement of the walls.

The reason why

Although concrete is a widely used construction material, its largest weakness lies in the vulnerability for cracking. Common examples are large slabs or long tunnel walls that show excessive cracking due to restrained shrinkage. Cracks can be detrimental for watertightness reasons, but also for long-term durability as it gives an easy entrance for harmful substances such as CO2 or chlorides (de-icing salts or sea water). This leads to accelerated corrosion and reduces the lifespan of concrete, necessitating costly maintenance procedures throughout the project's life cycle. Introducing self-healing properties to concrete can extend the service life of elements and reduce maintenance, particularly in projects where accessibility during operation is challenging or where temporary closure for repairs would have significant economic or environmental consequences on the society.

What’s next

The Ph.D. researcher is currently monitoring and testing the effects and benefits of the self-healing agent. Various healing products such as resin, polyurethane, and water repellents are being examined for their efficiency in laboratory settings. Tests are conducted before and after the injection of these products into the vascular network. Additionally, core drilling will be performed on the walls where the product was injected to assess the efficiency of the process using various testing methods like water absorption and wave velocity.

Healing agent leaking out of the crack after pumping through a water-repellent agent.

After the research and development phase, if the tests yield positive results, several subsequent steps, including certification, standardisation, and commercialisation, will be necessary to bring the solution to market. While certification and standardization are lengthy processes, the main challenge lies in making the self-healing methodology commercially attractive compared to traditional injection methods. Nonetheless, this innovative self-healing approach shows great potential in new projects where maintaining watertightness and durability in certain areas is essential. It proves particularly beneficial in situations where traditional injection methods are deemed unsafe or unfeasible due to factors such as limited accessibility.