If you can't stand the heat, get out of the laboratory. © HOCHTIEF/Kleber

The concrete designers

Burst, grilled, frozen and squashed—Our experts push concrete to limits. Innovation the (rock) hard way.

The concrete blocks in the shelves at the HOCHTIEF Innovation & Testing Center look rather battered. In fact, they were subject to extreme torture here in Mörfelden-Walldorf. We lock them into a cooling chamber at minus 40 degrees Celcius, let them fall to the ground from several meters of height, clamp them into grinding discs—and grill them at up to 1,200 degrees. However, it's not torture our testers are after, but research and development as well as quality assurance. To this end, we push the material to its limits—and sometimes beyond. "Concrete is an exciting material because it's so multi-faceted", says Marco Tschötschel who heads the HOCHTIEF laboratory.

A multi-talent
Concrete can carry bridges and support houses. It can dam and channel water. It protects against fire and cold, radiation or sound. In short: it's a multi-talent. And Tschötschel and his team can put many of its talents to the test. Always with the goal of improving concrete quality even further.

The way towards achieving this goal is brutal sometimes. The silent witnesses: destroyed concrete samples lining the courtyard in front of the laboratory which we also call "cemetery" here. They had to undergo load tests, breaking and grinding tests, tensile and compression tests, fire and cold shocks. With practical tests, the only private institute of this type in the German construction industry conjures ever new possibilities out of the concrete or mortar. "Ultimately, it's the right mix that counts," says Tschötschel.

Recipe? Top secret
Gravel, sand, water, and cement—that's the basic recipe for concrete. We promote its special talents by means of chemicals and minerals so that, when adorning facades, it can unfold an effect similar to Flanders lace, harden right on time after 30 minutes in the tunnel or, as a meter-thick casing for radioactive material, protect the environment against radiation.

Just like a star chef's risotto does not disclose its ingredients, you can't tell a concrete recipe merely from the outside either. But you will marvel at the material’s impressive performance: the "damper concrete" for nuclear waste casks, for example, to which the HOCHTIEF engineers added polystyrene balls in order to soften possible falls. Or the concrete mixture for the prototype of the deep-sea energy store StEnSea, which withstands the water pressure at a depth of 100 meters.

The extreme challenges for both material and testers, plus not least its successes are the foundation of the international reputation of the Innovation & Testing Center. Our engineers go about their work with cool heads. They keep testing until the mixture is right. And their recipes? Remain top secret.

On the radar
When bridges crumble or building structures need refurbishment, our experts are also in demand. "In order to find damage hidden inside the material, we X-ray concrete like doctors do patients,” says civil engineer Bente Ebsen. She locates iron inside the concrete and marks it via radar. The strength and homogeneity of the concrete are analyzed by using ultrasound. Ebsen examines hollow spaces in the structural elements with a button-size camera installed at the end of an endoscope. Wherever else boring is necessary or material samples have to be taken from the building structure, Tschötschel's team can help non-destructively. Because their diagnosis is based on experience and countless tests.

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