According to Chatham House, each year, more than 4 billion tonnes of cement are produced, accounting for around 8% of global CO2 emissions. In fact, as useful as concrete is for our construction, it is actually really bad for our planet.
The new system seeks to make concrete elements leaner, yet durable and stable. They plan to do this through pre-stressing, a process that sees a concrete element withstand very high loads.
In a traditional pre-tensioning, the reinforcements or tendons are usually made of steel. The issue here is that steel is susceptible to corrosion requiring the concrete layer around it to have a certain thickness. This means the amount of cement used can not be reduced.
There is a method of using carbon ﬁber-reinforced polymers (CFRP) to replace steel reinforcement that has been around since the 1990s. CFRP does not corrode allowing for the creation of leaner concrete components.
“But if you want to pre-stress these CFRP reinforcements in order to be able to build even thinner structures with a higher load-bearing capacity, you reach your limits,” said Empa scientist Mateusz Wyrzykowski. This is because the anchoring of CFRP bars is much more complicated and expensive than that of steel... until now.
The Empa team has come up with a new method of pre-stressing that sees the CFRP bars automatically pre-stress themselves. It is a special formula that allows the concrete to expand as it hardens.
“Our technology opens up completely new possibilities in lightweight construction,” added Wyrzykowski. “Not only can we build more stable structures, we also use considerably less material.” Are you ready for leaner cement?