Dr. Wolfram Schmidt uses a rheometer in the lab to examine the flow properties of concrete.

Dr. Wolfram Schmidt uses a rheometer to examine the flow properties of concrete.

Source: BAM/David Weyand

If concrete is not installed correctly there is a risk of cracks developing. In simple applications these can be compensated for using particular techniques. In the case of special concretes used in wind turbines, high-rise buildings or tunnels, a lack of knowledge about flow properties can lead to significant structural and safety defects.

Dr. Wolfram Schmidt from BAM is researching the flow properties of concrete in the interdisciplinary "M-Flow" project. The BAM team want to provide fresh impetus, especially as many of the standards and regulations in the construction sector are still based on knowledge about building materials from the 1960s.

Much more than water, cement and sand

In the process they are particularly interested in the smallest particles during the transition from liquid to solid, because concrete has long since consisted of more than just water, cement and sand. It is composed of a multitude of chemical additives for example polymers, i.e. molecular chains, or nanoparticles used as a binding agent. They provide better cohesion between the components of the concrete without them clumping together, and they enable the mixture to flow more smoothly. It is precisely because of its many components that the flow properties of concrete are very varied and complex.

Chemists, physicists and engineers for greater efficiency

Therefore the BAM project involves not only chemists and physicists – experts on additives – but also engineers as specialists in construction chemistry and concrete processing. Together they want to gain a better understanding of how the flow properties can be altered.

This would enable the construction material to be used in a more targeted way. Manufacturers would be able to optimise the chemical composition of their products, while architects and structural engineers would gain new possible applications. It would even be conceivable that concrete walls, which previously needed to be 60 centimetres thick, would end up being only 30 centimetres. But we will only be able to use modern concretes without error and thereby save resources if we can learn how they flow. The majority of structural defects actually arise from incorrect processing. This also applies to offshore wind turbines: greater understanding of the flow properties of concrete could significantly increase the safety and longevity of the turbines.