Concrete degradation is a process that occurs when concrete is damaged due to a variety of reasons, such as calcium leaching, physical damage, bacterial corrosion, and more. In this article, we will discuss the various causes of concrete degradation and what can be done to prevent it. Fire, aggregate expansion, the effects of seawater, bacterial corrosion, calcium leaching, physical damage, and chemical damage (from carbonation, chlorides, sulphates and non-distilled water) are some of the main causes of concrete degradation. Fire can cause explosive spalling of the concrete if it is rapidly exposed to very high temperatures.
Steel formwork can also pinch the top surface of a concrete slab due to the weight of the next slab to be built. Free calcium hydroxide (Ca(OH)) can remain within the hardened concrete and dissociate to form Ca2 and hydroxide (OH-) ions. Neutrons and gamma radiation in nuclear power plants and high flux material test reactors can also induce radiation damage to concrete structural components. The modern use of steel reinforcements (rebar) hidden within the concrete can also lead to deterioration.
This is because steel in concrete ruins its potentially great durability. Spalling, disintegration, erosion, reinforcement corrosion, delamination, spalling, alkali-aggregate reactions and concrete cracking are some of the effects of concrete deterioration. Above 600 °C, concrete turns light grey, and above 1000 °C, yellow-brown. Mechanical damage can also be caused by erosion from waves or from the sand and gravel they carry.
Crystallisation of salts in the water that soak into the pores of the concrete can also cause damage when they 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). Treating the concrete with a rust inhibitor compound is one option for preventing deterioration. However, this can be toxic and inappropriate for buildings.
Above the water's surface, the effects are more pronounced than where the concrete is permanently submerged. Within a decade, a very rare hydrothermal mineral called aluminium tobermorite (Al-tobermorite) has formed in concrete.
