How long does concrete take to degrade?

The modern concrete used in everything from roads to buildings and bridges can break down in as little as 50 years. But more than a thousand years after the Western Roman Empire turned to dust, its concrete structures are still standing. Engineers in the early 20th century thought that reinforced concrete structures would last a long time, perhaps 1,000 years. In reality, their lifespan is more like 50 to 100 years, and sometimes less.

Building codes and policies often require buildings to survive several decades, but deterioration can begin in as little as 10 years. Concrete degradation can have several causes. Concrete can be damaged by fire, aggregate expansion, seawater effects, bacterial corrosion, calcium leaching, physical damage and chemical damage (from carbonation, chlorides, sulphates and non-distilled water). This process adversely affects concrete exposed to these damaging stimuli.

Our blue and green world is becoming increasingly grey. By one estimate, we may have already passed the point where concrete exceeds the combined carbon mass of all the trees, shrubs and bushes on the planet. In these terms, our built environment is outstripping the natural one. However, unlike the natural world, it does not actually grow.

Instead, its main quality is to harden and then degrade, extremely slowly. To the ordinary citizen, concrete can seem like an indestructible material. It can form huge structures, be almost completely weatherproof and last for years, but what is the real lifespan of concrete? Let's take a closer look at how long concrete can last and what you can do to improve the lifespan of your own concrete projects. Concrete is a durable material that can last a lifetime.

The term durability means that something can last for a long period of time without deteriorating significantly. With a durable material such as concrete, the environment is conserved and waste is reduced. Concrete is able to withstand weathering, chemicals and abrasion if properly installed and maintained. There are different applications of concrete that require different methods and offer varying degrees of durability.

Factors to consider include exposure to the environment and the desired properties of the concrete. An example of this was the 1996 Channel fire, where fire reduced the thickness of concrete in an underwater tunnel connecting France to England. Concrete in buildings that suffered a fire and remained standing for several years shows an extensive degree of carbonation from carbon dioxide being reabsorbed. As elsewhere, the concrete craze in South America's largest nation began benignly enough as a means of social development, then morphed into an economic necessity, and finally metastasised into a tool of political expediency and individual greed.

In general, it is important to consider the environment, the installation process, the concrete used and the climate of the area to determine how long the concrete will last. These coatings protect the concrete to some extent from other processes, such as magnesium, chloride and sulphate ion attack and carbonation. Often this means reapplying a protective coating every few years, regularly ensuring that the concrete is kept clean and free of any residues. It is worth mentioning that there are concrete mixes specifically designed to withstand extreme weather conditions.

The fact is that not all concrete is the same, so the service life of concrete varies from one characteristic to another. For months, or years, after the young concrete has cooled, the AFt crystallises very slowly in the form of small acicular needles and can exert considerable crystallisation pressure on the surrounding hardened cement paste (HCP). If the concrete is exposed very quickly to very high temperatures, explosive spalling of the concrete can occur. Fire will expose the concrete to gases and liquids that can be harmful to the concrete, including salts and acids that are produced when the gases produced by a fire come into contact with water.

For large-scale projects, such as buildings, concrete should last up to 100 years if properly cared for. Of course, if in doubt, it is always a good idea to consult a concrete professional. The effects are more pronounced above the tidal zone than where the concrete is permanently submerged. In the time it takes you to read this sentence, the global construction industry will have poured more than 19,000 concrete bathtubs.

Chloe Robinson
Chloe Robinson

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