Engineering Headlines

New Concrete is environmentally friendly

Concrete is now green, and that is not the color: researchers from the TU Graz have invented a concrete, which causes a third less carbon dioxide and requires 15% less energy. Nevertheless, the miracle concrete has the same properties as standard one.

Concrete should be the most used material in the civil engineering and construction worldwide, hardly a House, hardly a bridge or a tunnel coming off without concrete. And that not only recently: lime mortar as a Binder has been demonstrated in already 10,000 years old building remains in modern day in Turkey. This is also because that quite easy to manufacture is concrete: cement, aggregates and water.

30% less carbon dioxide

Despite this very short list of ingredients, the environmental performance of concrete is rather mediocre and this is due to the binder cement. Because the conventional Portland cement is fired at around 1,450°C. This requires enormous energy. In addition, much of carbon dioxide is released in this process.

green cement
Less water, this micro filler: So an extremely hard, resistant concrete can be with very low water/Binder ratio produced. Photo: Graz University of Technology (Germany)

The cement industry is the world’s second largest carbon dioxide source after the burning of fossil fuels. Therefore, the work of Joachim Juhart and his team from the Institute for material testing IMBT is a valuable contribution TU Graz. It succeeded to produce a concrete, which emits up to 30% less carbon dioxide and consumes about 15% less energy.

Sustainably improve concrete

“It comes us not to create alternatives to concrete, but to improve concrete as existing, proven building material”, emphasizes Juhart. “We have mixed with very fine rock flours as so-called micro filler and thus optimise the packaging density of the mixture. As a result we could admit more filler from stone dust or also on ground granulated slag.”

Graz University of Technology - New Concrete
A staff member at the Institute for materials testing and building material technology optimizes the composition of powdery substances from concrete. Photo: GRAZ University of Technology (Germany)

Filler from regional rocks

The advantage: This filler can be from several, also regional existing rocks, which must not only be burned with high energy costs. “The big challenge is firstly to identify the correct materials for it and secondly to get the correct mixing ratio”, explains Joachim Juhart.

Together with the Association of the Austrian concrete and precast works Juhart’s team in the project “OKO 2 Concrete” has developed a concept for the optimum composition of concrete that meets all requirements for precast concrete.

Comparable to standard concrete

On the campus at the TU Graz 2.4 x 3.0 m were now rebuilt large OKO 2 Concrete wall elements with produced in the normal production cycle of a concrete manufacturer. Team Juhart has been accompanying the new concrete element.

The result: OKO 2 Concrete for finished parts can be processed as well as standard concrete and also the early strength and curing time are similar to standard. Precast concrete must achieve eight hours a strength, which allows you to peel the pieces and lift. OKO 2 Concrete meets these requirements and is also visually by conventional precast concrete parts indistinguishable.

The next step involves the longevity

“This element proves that one concrete with less Portland cement, for supplementary materials can produce, thus he is more environmentally friendly, but has the same properties or the equivalent performance as conventional concrete”, explains Juhard. “We hope to be able to build prototype elements or structures with our external cooperation partners and partners subsequently.” Because it’s no longer all about the optics. In the next step Juhart wants to examine with his team, whether the new material with good climate and energy balance in a much more important construction aspect works: it’s all about the durability.