Interview to Carmen Andrade, professor of investigation of the Institute of Sciences of the Construction Eduardo Torroja

At the beginning of the 1990s, the Spanish manufacturers of concrete asked me what test better reflected the durability of the concrete. I answered them that there was not only one but several. In 1993, I began to investigate to find a single trial fast and easy. This year, at the Institute we have created a portable resistivímetro, a small team capable of reporting the potential durability of concrete in 30 seconds.

Yes. So far taking samples that were put in contact with solutions of chlorides either introduced in cameras with carbon dioxide. After several days of research in specialized laboratories, determined its durability by measuring the diffusion coefficients. The equipment we have designed is not destructive, i.e. its user does not have to remove a witness or a piece of concrete. It can also measure properties of this many times as you want and in situ.

According to Andrade, the instruction EHE-08 is "a step forward with respect to the above and, as the human, still room for improvement". Above all, explains, annex 9, which is not compulsory and opens the door to the use of models for the prediction of durability of concrete, needs modernization, an update. "In fact, I would like this rule, at the time, to take into account our essay".

Yes, durability but also other properties. The team can offer much more information. At the time that is mixed, in fresh State, cannot be predicted what will be their mechanical strength and durability. The concrete is like a rock with pores. The resistivity measured impermeability, the resistance of the concrete to the input of substances from the outside. With the resistivity, we can measure what will be the concrete.

As I mentioned, the trials that are currently used are very complex, with formulas with many parameters. I was looking for something that, to put it in some way, not mareara the manufacturer and the user. The device is very simple: is ultrasound, which collects data from the surface without need to biopsy the body. With our team, the manufacturer is autocontrola and saves time and money. He can introduce the device in its own cement mixer and see how the concrete is stiffening and if this is fulfilling or not with the specifications. In addition, the user may check product that serve.

In reality, what does is apply Ohm's law, i.e. a current applied and measures the potential difference. The potential is divided by the stream and gives the electrical resistance. With it, in addition to measuring the properties of the concrete, its microstructure and the degree of curing, we can find out if the armor that is inside is corroding. In science, we say that the most simple is more elegant. Always liked look for simple things.

Yes, the most known and used worldwide, manufactured by an American company, called Gecor and so develop US 20 years along with the Cenim and Geocisa company. We want that the current resistivímetro also as corrosímetro for measuring the corrosion of the armor.

We now have the prototype and first model manufactured by the Spanish company of Geotechnics Geocisa. The idea is to market it between manufacturers of concrete and the laboratories of quality control, at both national and internationally, throughout 2010.

Our portable resistivímetro is simple and cheap... I think that it will become a common apparatus within the sector of the concrete structures. What we have already proposed to the European legislation and in United States.