AAC: Stable even when the earth shakes

Earthquakes are not uncommon. For example, on these three days at the end of May 2023: A series of earthquakes measuring 4.0 on the Richter scale shook people living far below Mount Etna. The day before, people in the Tokyo area suffered even more. There, tremors at a depth of 46 kilometers produced a magnitude of 6.1. Almost at the same time, a magnitude 6.0 quake struck the Tonga archipelago. Two days before Etna, instruments in Yellowstone National Park recorded a magnitude 2.8 quake. Europe, America, Japan: Residents' lives depend largely on the materials used to build their homes in the event of an emergency. Photographs from around the world show streets where some buildings have been reduced to rubble, while others remain standing. Despite cracks, especially on the first floor, they remained pressure-resistant, and their occupants were able to leave in time.

How resistant is Ytong's autoclaved aerated concrete?

The Institute of Civil Engineering in Ljubljana has now tested which building materials can withstand seismic forces. On the institute's seismic platform, the Slovenian experts tested three models of a typical Ytong building against other blocks.

The models were three- and four-storey Ytong models that were 1:4 replicas. The dimensions of the base of the prototype building were 6.85 x 8.75 m and the height of the floor was 2.70 m. Two models had three floors and a mansard roof, another had four floors and a mansard roof. The floor was made of white concrete or monolithic reinforced concrete. Realistic and different severe earthquake scenarios were simulated by the experts. The dynamic behavior and a tangential failure mechanism were analyzed. This can be calculated based on the diagonal cracks in the walls.
The engineers found that all models retained the stability performance of their non-seismic reference objects. The dynamic support mechanism and the tangential failure mechanism make the Ytong houses as strong as brick buildings. The houses were cracked, but this did not affect their stability.

Tests on the seismic platform in Ljubljana showed that the vertical damage in the load-bearing walls successfully connected the walls, prevented the disintegration of the cracked parts of the walls and ensured the stability of the building until demolition.

In-house earthquake research at Xella

Xella Technologie- und Forschungsgesellschaft mbH (T&F) maintains its own test facilities for earthquake simulation at the Emstal site in order to continuously improve the resistance of cellular concrete. Here, for example, the deformability of Ytong is measured. As in an earthquake, test walls are subjected to cyclic horizontal loads for several hours. Based on these test results, computers analyze the earthquake resistance of eleven different building configurations made of autoclaved aerated concrete blocks.

Since autoclaved aerated concrete systems are not specifically covered by the European earthquake standard, Xella T&F worked with the Italian EUCENTRE to develop an evaluation document that served as the basis for issuing a European Technical Assessment (ETA).

To find out why Icelandic families decided to build their houses in Ytong and how a swarm of seismic shocks made planners and craftsmen sweat, click here.

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