page_title: Rust
section_title: Economic effect
hierarchical_section_title: Rust / Economic effect
caption_attribution_description: Deutsch: Dies ist eines von einer Serie von 46 Bildern, die einen Vergleich anstellt zwischen 2 Brücken. Die erste Brücke (Bilder 1 bis 45) ist Teil der kanadischen Autobahn QEW (Queen Elizabeth Way) überquert einen Fluss und die Straße „Oakwood Drive“ in Niagara Falls, Ontario, Kanada. Die zweite Brücke (Bild 46) überquert einen Kanal innerhalb der Stadt Amsterdam, Niederlande. Der Baustahl und Beton der kanadischen Brücke sind in einem Korrosionszustand. Die Brücke verrottet. Die niederländische Brücke ist unversehrt. Die kanadische Brücke wurde bereits saniert. Allerdings haben die Sanierungsarbeiten an der kanadischen Brücke nicht die Ursachen der Korrosion behoben. Daher setzt sich die Korrosion des Stahls und der Verfall des Betons ungehindert fort. Die oberen Stahlträger der kanadischen Brücke sind durch eine kovalente Beschichtung gegen Rostbildung geschützt. Dies erscheint unsachgemäß da Betonelemente anscheinend direkt auf der Beschichtung aufliegen, wodurch die Beschichtung zerstört wird. Der Beton ist porös und lässt daher Regenwasser mitsamt Chloriden (Streusalz) rein und raus. Der dann ungeschützte Stahl ist dadurch dem Wasser und auch Chloriden und Luft ausgesetzt und verrostet. Es scheint keine Schutzschicht zwischen den Stahlträgern und dem Beton zu sein. Man sieht keinerlei Platz zwischen den beiden Elementen. Selbst wenn etwas dort wäre um die Rostfarbe zu beschützen, scheint dies offensichtlich nicht zu funktionieren, weil sonst kein Rost dort wäre um sich weiter auszubreiten. Der Rost unterwandert die Beschichtung und verbreitet sich, genau wie bei einem rostendem Auto. Selbst wenn neu gesandstrahlt und beschichtet wird, bleibt der Kontaktpunkt zwischen Baustahlträgern und Beton ungeschützt. Daher bleiben neue Sanierungsarbeiten dieser Art erwartungsgemäß erfolglos. Der Beton ist von schlechter Qualität, da er das Wasser mitsamt Chloriden (Streusalz) einlässt, welches dann die Stahlbewehrung angreift. Ein kleiner Rostbezug der Bewehrung ist normalerweise unbedenklich, da der alkalische Beton so besser auf der Bewehrung haftet. Hier wurde allerdings ein billiger Beton genommen mit Zement, der gegen Bewitterung und Salzeinwirkung unbeständig ist. Daher rostet die Bewehrung stark. Dies führt zu einer Expansion der Bewehrung, bis der Beton außen abplatzt, welches die Stärke der Brücke sowie die Bevölkerung einer Gefahr aussetzt. Da die Ursachen der Verrottung nicht behoben wurden, lässt sich erkennen, dass die Sanierungsflicken aus Beton nur von kurzfristiger Wirkung sind, da die im Beton sich ausdehnenden Risse sich auch in die Flicken ausdehnen, welche von Anfang an zum Abplatzen verurteilt sind. Die niederländische Brücke hingegen leitet die Last über kovalente Kautschukplatten auf Stützen ab, in einer Art und Weise, dass keine Korrosion entsteht. Der Beton ist durch eine kovalente Beschichtung gegen Wetter und Viehsalzeinflüsse geschützt. Der Stahl der kanadischen Brücke ließe sich über eine leicht Stromleitung gegen weitere Korrosion schützen. Die physikalischen und chemischen Fehlerquellen, die zu der Verrottung der kanadischen Brücke führten, waren zu Bauzeit bekannt und Lehrgegenstand in internationalen, technischen Hochschulen. English: This is one of a series of 46 pictures, which compares two bridges. The first bridge, (pictures 1 – 45) is part of the Canadian freeway QEW (Queen Elizabeth Way), crossing a river and “Oakwood Drive” in Niagara Falls, Ontario, Canada. The second bridge (picture 46) crosses a canal inside the City of Amsterdam, Netherlands. The structural steel and concrete of the Canadian bridge are in a state of corrosion. The bridge is rotting. The Dutch bridge is unharmed. The Canadian bridge has already had restoration work done on it. However, the restoration work has apparently not eliminated the causes of the corrosion. Because the causes of the corrosion have not been eliminated, the corrosion and disintegration of the steel and the concrete continue unhindered. The upper steel beams of the Canadian bridge are coated with a covalent paint to prevent rust formation. This does not resolve the rust formation issue because it appears that the steel beams are directly supporting concrete elements above, which then crush/destroy the coating, so it can no longer protect the steel against rust. The concrete is porous, thus letting rain water together with chlorides (road salt) in and out. The now vulnerable and unprotected steel then rusts due to the water, salt and air contact. Once rust has set in, it then goes underneath the coating on the rest of the steel, popping off more of the coating as it goes along, just like it does on a rusting car. Even if that steel were sandblasted and re-coated, the contact point between the top of the steel beams and the concrete above would remain unprotected. It does not appear as though there is any room or barrier between the steel and the concrete. Even if there were something there, it does not appear to have protected the rust paint enough to remain intact under the weight of the concrete. Because of this apparent dynamic, it cannot be expected that further restoration work of this type (sandblasting and recoating that does not reach the contact points that are the root cause) will be successful. The concrete is of poor quality for this application because it lets the water and diluted road salt in, which then attacks the reinforcing steel bars. A small coating of rust on the rebars normally is not cause for concern because it allows the alkaline concrete to adhere better. However, in this case it appears that a cheap concrete was chosen, with a cement that cannot withstand outdoor weather and salt influence. Because of this, the rebar is corroding vigorously. The added rust causes the volume of the rebar to expand, until the outer concrete pops off, which reduces the strength of the bridge and imperils the population. Because the root causes of the rot were not removed, it is apparent that concrete repair patches are but a temporary measure as the existing and new cracks carry on right into the repair patches, which dooms the patches to pop off along with the rest of the concrete right from the start. The Dutch bridge on the other hand transfers its load through purpose-made covalent rubber pads to the columns below in such a manner that no corrosion is created. The concrete has received a covalent paint such as to protect it against the influence of outdoor weather and road salt. It would be possible to protect the steel in the Canadian bridge by conducting a small electrical current through it. The physical and chemical error sources that have led to the rot in the Canadian bridge were known and were the subject of teaching engineers in technical universities internationally during the time of the construction of the Canadian bridge.
context_page_description: Rust is an iron oxide, a usually reddish brown oxide formed by the reaction of iron and oxygen in the presence of water or air moisture. Several forms of rust are distinguishable both visually and by spectroscopy, and form under different circumstances. Rust consists of hydrated iron(III) oxides Fe₂O₃·nH₂O and iron(III) oxide-hydroxide.
  Given sufficient time, any iron mass, in the presence of water and oxygen, could eventually convert entirely to rust. Surface rust is commonly flaky and friable, and it provides no protection to the underlying iron, unlike the formation of patina on copper surfaces. Rusting is the common term for corrosion of iron and its alloys, such as steel. Many other metals undergo similar corrosion, but the resulting oxides are not commonly called rust.
  Other forms of rust exist, like the result of reactions between iron and chloride in an environment deprived of oxygen. Rebar used in underwater concrete pillars, which generates green rust, is an example.
context_section_description: Rust is associated with the degradation of iron-based tools and structures. As rust has a much higher volume than the originating mass of iron, its buildup can also cause failure by forcing apart adjacent parts — a phenomenon sometimes known as "rust packing". It was the cause of the collapse of the Mianus river bridge in 1983, when the bearings rusted internally and pushed one corner of the road slab off its support.
  Rust was an important factor in the Silver Bridge disaster of 1967 in West Virginia, when a steel suspension bridge collapsed in less than a minute, killing 46 drivers and passengers on the bridge at the time. The Kinzua Bridge in Pennsylvania was blown down by a tornado in 2003, largely because the central base bolts holding the structure to the ground had rusted away, leaving the bridge anchored by gravity alone.
  Reinforced concrete is also vulnerable to rust damage. Internal pressure caused by expanding corrosion of concrete-covered steel and iron can cause the concrete to spall, creating severe structural problems. It is one of the most common failure modes of reinforced concrete bridges and buildings.
caption: Rusting rebar has expanded and spalled concrete off the surface of this reinforced concrete support
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