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Are Self-Healing technologies interesting for UHPC?

self healing technologies in uhpc

Good afternoon everyone! I am happy to launch this first post of autumn 2022. Let’s talk about the UHPC and the Self-healing technologies.

Today I am providing my point of view of a question where I really would like to receive the perspective from you, the readers. I am wondering if the self-healing technologies may be particularly useful for UHPC.

To start, a self-healing (SH) technology in concrete is a specific admixture or system added to concrete to allow the healing of a crack(s) once it appear. As the wound healing in our skin avoids the entrance of bacteria, SH in concrete prevent that water and chlorides reach the rebar and generate corrosion. There is a large variety of SH technologies: Bacteria, macro-capsules, vascular networks… Some of them are already in the market, but some others are still in embryonic stage. You can find detailed information about more technologies in the research project SMARTINCS, of which RDC is one of the beneficiaries.

Certainly, SH concept seems a good idea to increase the lifespan of a structure. However, clients are rarely willing to pay a little bit more for the promise of a larger lifespan. If you think about it, in many fields of life we do not appreciate durability as it deserves: Do we consider durability as a criterion to purchase sneakers? Or even to decide the brand of our new car? Do we really consider lifespan when we choose our house, which is possibly the largest expense of our lives? The answer is that generally no. This could be an explanation of why, despite of being interesting, SH technology is not penetrating decisively into the market yet. 

Does this ring a bell? UHPC technology suffered the same issue years ago. Clients generally did not choose to pay a little bit more for the promise of a higher lifespan. Thus, UHPC solutions developed in two main fields:

1) In applications submitted to very aggressive environments, as durability of traditional materials is far from be acceptable;
2) In any application where the UHPC structure is as economic as its alternative, so the extra durability is an improvement that the client receives “for free”, for the same cost. Now we know that UHPC is very welcome by any client, but we need to reach a design for the same cost than the alternative.

uhpc bridge self-healing

Coming back to SH technology, I feel that in the UHPC sector it could be more appreciated. It is only my perspective, but I have several arguments to explain it:

  • The volume of concrete used is 50% to 70% lower, so the expense in SH product is lower.
  • The cost per m3 of UHPC is 5 to 10 times higher than the cost of ordinary concrete. This means that the influence of the cost of the SH product per m3 is much more reduced.
  • Crack width in UHPC is lower than in ordinary concretes, so the efficiency of the SH agent is much higher. Normally, cracks smaller than 50 μm close in less than a month.
  • Many UHPC structures are in the sea or in wet environments, where the efficienty of some self-healing technologies is higher.
  • Normally UHPC structures are used there where durability is very relevant, and there is where it is particularly interesting to close cracks if they appear.

Do you agree with this perspective? Do you think that it makes sense to combine these two concrete technologies? Or UHPC is already too good and too expensive to add more functionalities?

It would be exciting to have an open discussion about this.

Thank you,

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