Does concrete degrade over time?

Concrete degradation occurs when concrete is damaged for almost any reason, such as calcium leaching, physical damage or bacterial corrosion. While these are just some of the main reasons concrete degrades, we will go over some of the other ways it is destroyed over time and whether anything can be done about it. Concrete degradation can have several causes. Concrete can be damaged by fire, aggregate expansion, the effects of seawater, 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. But it is not a wonder material. As concrete cures, it shrinks, which can lead to cracking. And when reacting with water, concrete does something else: it creeps, or deforms progressively over time.

This has been known for decades and is included in all concrete-related calculations used in construction projects, so it is nothing new. But the actual cause of creep remains a mystery. Concrete deterioration can cause major headaches for building owners. It is important to correctly identify these defects early and plan appropriate repair strategies.

Concrete deterioration can occur through spalling, disintegration, erosion, reinforcement corrosion, delamination, spalling, alkali-aggregate reactions and concrete cracking. If the concrete is rapidly exposed to very high temperatures, explosive spalling of the concrete can occur. Steel formwork pinches the top surface of a concrete slab due to the weight of the next slab to be built. Some free calcium hydroxide (Ca(OH) remains within the hardened concrete and can further dissociate to form Ca2 and hydroxide (OH-) ions.

Exposure of concrete structures to neutrons and gamma radiation in nuclear power plants and high flux material test reactors can induce radiation damage to their concrete structural components. The critical difference is the modern use of steel reinforcements, known as rebar, hidden within the concrete. This means that concrete structures, despite their stone-like surface qualities, are actually made from the skeletons of rock-crushed sea creatures. Concrete is the most widely used building material in the world, with more than six billion tonnes produced each year.

However, none of these developments can solve the inherent problem that putting steel into concrete ruins its potentially great durability. Concrete also makes up the largest proportion of construction and demolition waste, accounting for about a third of all landfill waste. Above 600 °C, concrete turns light grey, and above 1000 °C, yellow-brown. Above the water's surface, mechanical damage can be caused by erosion from the waves themselves or from the sand and gravel they carry, and by the crystallisation of salts in the water that soak into the pores of the concrete and then dry out.

The researchers used a combination of experimental and theoretical techniques to determine this mechanism: they used microindentation (which involves pressing a tiny, hard point into concrete samples and observing their response) and vertical scanning interferometry (which involves imaging 3D C-S-H patches and measuring them as they shrink or grow). Another option is to treat the concrete with a rust inhibitor compound, although this can be toxic and inappropriate for buildings. The effects are more pronounced above the tidal zone than where the concrete is permanently submerged. Within a decade, a very rare hydrothermal mineral called aluminium tobermorite (Al-tobermorite) has formed in concrete.

Chloe Robinson
Chloe Robinson

Evil pop culture fanatic. Extreme zombie trailblazer. Devoted coffee fanatic. Hardcore social media scholar. Wannabe coffee geek.