COVID and concrete, by Mr. Christian Tridon

22/09/2020

Concrete is a composite material, a binding agent and various aggregates.  Even though it is very resistant in compression, it has a notable weakness regarding tensile forces. This is why the frames generally made in carbon steel are carefully laid in order to overcome this weakness.

Let’s remind us that the lime which is the main material of the artificial cement has been decarbonated in the oven of the cement-manufacturer.

Then, the lime will constantly be re-carbonating itself. The consequence is that the PH of the fresh concrete will drop to reach an acidic area, in which steels corrosion will grow. That will lead to the breakage of the concrete.

Here, very briefly, one of the most common pathologies of reinforced concrete.

So, what we can do?

It is to protect the surface of the concrete in order to limit the spread of the atmospheric agents (and in particular carbon dioxide) through this material. All reinforced concrete structures are potentially concerned by this pathology.

What is the similarity with the coronavirus?

It is obvious. Here too it is a matter of protection. If we had been more vigilant, we could have avoided or at least limited the outbreak. For concrete, this the same case. Due to a lack of anticipation, the « virus » that causes the re-carbonation of the cement, spreads inexorably and reaches all the unprotected concrete structures.

In this case, we don’t have masks and social distancing, but we can repair and reinforced the sick structure. However, as for the Covid-19, we need to « test » the structure in order to be able to diagnose the sick structure and to assess their scope.

The heritage of reinforced concrete structures is immense, it is important to act before degradation becomes irreversible.

Article by Mr. Christian Tridon, STRESS President