Can German roads hold up against the heat?

Scorching hot temperatures — such as those in which Germany and much of Europe have baked in recent days — can cause things to fray and crack, not least a person's nerves.

It turns out that airport runways can crack under the strain too. On Tuesday evening, Hanover Airport, Germany's ninth-busiest, had to cease operations after the ongoing heatwave caused damage to one of its two runways.

With the other runway already out of commission due to previously scheduled renovation work (unrelated to the heatwave) planes could not land or take off and the airport was closed until Wednesday morning, with repair work taking place overnight.

Temperatures as high as 36 degrees Celsius (96.8 Fahrenheit) had caused slabs of concrete on the runway to buckle and crack. The head of the airport, Raoul Hille, said the damage caused by the high temperatures could not have been foreseen. "There are no sensors for that," he said.

However, reports that the affected concrete slabs in Hanover dated from the 1960s — a golden era of capital investment in Germany, now very much in the past — did beg the question as to whether the older concrete had as much to do with the so-called runway "blow-up” as the soaring temperatures did.

No investment please, we're German

Germany has a long-established infrastructure investment problem. Since a post-reunification investment boom in the early 1990s, the net infrastructural investment of German states has plummeted, with the belt-tightening generally blamed on "debt brakes" imposed on state and federal spending by the German government during a financial crisis in 2001 and during the global financial crisis almost a decade ago.

With less money available for capital projects across the country, important investment has often been delayed. Stories of crumbling infrastructure — from road, to rail to public buildings — have been quite common in Germany in recent years.

But if the heat continues, could what happened with the runway in Hanover also happen on German roads or other concrete surfaces in need of investment?

It is important to note that there is still no evidence to suggest that the concrete at the airport buckled because of its age.

During extreme heat, concrete surfaces can crack due to a process known as thermal expansion. Moisture may seep into a small crack or near a joint in the concrete and on a particularly hot day, when temperatures go above 30 degrees or more, it is possible for the crack to expand and ultimately buckle if there is not enough room for the expansion. This problem is not isolated to older concrete.

"In regions like Qatar, expansion joints in concrete are designed for high temperatures of up to 60 degrees," Heinrich Grossbongardt, an independent airline advisor told the public broadcaster NDR this week following the incident in Hanover.

"In Germany, on the other hand, dealing with aspects like frost protection and heavy precipitation have been the focus so far," he explained, in the context of the country's airport runway infrastructure.

Running out of road?

Despite the aforementioned problems with German infrastructural investment, the country's road network still ranks relatively highly by EU standards.

According to the European Commission's mobility and transport division, in 2016/2017, Germany ranked sixth in the EU in terms of "quality of roads", scoring 5.51 out of a possible mark of 7. The Netherlands, France, Portugal, Austria and Denmark were the only countries ranked ahead of it in the study.

Nonetheless, there have already been signs this summer that Germany's road network may be threatened by hot weather. In early June, when temperatures also crossed the 30 Celsius mark, some sections of German motorways cracked apart.

Three lanes of the A1 between Bad Oldesloe and Bargteheide in the north of the country had to be closed due to buckled concrete, while sections of the A10 near Berlin and the A9 in Saxony-Anhalt were also damaged.

The German automobile club (ADAC), the largest in Europe, said at the time that the damage showed the need for the federal government to increase investment in the country's road infrastructure.

"Short-term measures have begun on the sections that are particularly at risk," said an ADAC spokesperson last month. "But this should not replace a thorough overhaul that is required for most of the motorways concerned."

Buckling under the strain

While older, already-damaged roads and motorways are more at risk of excessive heat damage than newer ones, it is a simple fact of physics that unusually high temperatures will pose a risk of "blow-up" to sections of concrete at risk of thermal expansion.

Given that Germany does not regularly experience temperatures of more than 30 degrees, the wisdom of proofing the country's road infrastructure specifically for hot weather can be questioned, given the obvious additional costs and know-how required.

Yet, when one considers the widespread implications of global warming and the fact that German summers are getting hotter, as well as the fact that many experts believe German roads already need something of an overhaul — heatwaves or not — it is surely a worthy area of debate.