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The Churchill Way flyovers in Liverpool city centre have been closed after a routine inspection found design and construction flaws.
The new survey will involve structural testing, removal of the road surface and drilling into the decks as well as underground assessments of every supporting column.
The Highways Agency revealed in 1999 and 2000 that the post-tensioning tendons holding the precast concrete structure together were corroding and work began by the new bridge owner, Transport for London (TfL) to slow down the corrosion process. However in 2009 further inspections revealed significant deterioration in the tendons which resulted in TfL establishing probably the largest structural monitoring programme in Europe, with 400 acoustic sensors on the eastern section. This proved vitally important at highlighting the urgency of works required. For example, the system picked up about one break a month on the Huntingdon flyover; Hammersmith flyover had one wire break a day. There was no doubt that the situation was critical.
Steel reinforcement was a dramatic innovation of the 19th century. The steel bars add strength, allowing the creation of long, cantilevered structures and thinner, less-supported slabs. It speeds up construction times, because less concrete is required to pour such slabs. These qualities, pushed by assertive and sometimes duplicitous promotion by the concrete industry in the early 20th century, led to its massive popularity.
. . .
Early 20th-century engineers thought reinforced concrete structures would last a very long time – perhaps 1,000 years. In reality, their life span is more like 50-100 years, and sometimes less.
The new composite material, which is more than twice as strong and four times more water resistant than existing concretes, can be used directly by the construction industry on building sites. All of the concrete samples tested are according to British and European standards for construction.
Crucially, the new graphene-reinforced concentre material also drastically reduced the carbon footprint of conventional concrete production methods, making it more sustainable and environmentally friendly.
Said to be the strongest material ever measured . . .
The problem that scientists face is that these "miracle" properties have only ever been demonstrated on a tiny scale.
"The kind of strengths that people quote may not even apply to microscopic samples," says Dr Lin.
"So, while it may be true that on a local level it has this strength much stronger than steel, we have to be careful about these claims.
"We recognise the limitations of graphene and are trying to do things that do not bend the rules of physics.
originally posted by: Phage
a reply to: Pilgrum
Concrete is not waterproof (without help) water gets to the steel. Steel oxidizes and gets bigger. Concrete is not so good at making room for it.
Stainless rebar works, but holy crap, it's expensive. And who knew, 50 years ago? Put the bridge up! Now!