The new concrete is thus environmentally friendly. However, it also needs to be stable. To test this, the team from the EPF Lausanne investigated the carbonation of the new concrete. In the construction sector, this term denotes a chemical reaction that takes place in the concrete in the presence of carbon dioxide and moisture. This changes the pH value of the concrete and, for reasons of statics, the steel elements embedded in it become susceptible to rust.
In order to measure the carbonation, the scientists developed methods that artificially bring about the chemical process in the concrete without changing the process itself. They thus simulated natural carbonation. The simulation revealed the factors that influence the process. In addition to moisture, these include the porosity of the concrete and its composition. Here, it was shown that the burnt oil shale and limestone, which partially replaced the traditional cement, had a positive impact. They inhibited the carbonation process.
Generally speaking, the results suggest that the effect of carbonation on the structure of the concrete is smaller than had been assumed until now – its structure obviously also changes when it dries up.