In the past, concrete was considered an “indestructible” material. This belief has led many builders and designers to ignore the most basic rules to guarantee the durability of concrete structures. The result is that 20-30 years after construction, most of the concrete buildings show obvious signs of degradation, if they have not been maintained.

At present, the continuous increase of the construction costs makes it sometimes more advantageous to repair and consolidate the degraded concrete constructions, even if the degradation process has reached a rather advanced stage.

Causes of concrete degradation

The causes of the degradation are often favored by qualitative deficiencies of the concrete and are usually determined by the environmental conditions to which the building is exposed.

They can be divided into:

• Chemical
• Physical
• Aggression caused by freeze / thaw cycles
• Aggression caused by fire
• Mechanical
• Aggression caused by abrasion, erosion, tearing, overload and impact.

Normally, concrete deterioration progresses relatively slowly. In the initial phase, which could take quite some time, there are no visible signs on the concrete surface. However, in its structure, the carbonation process is already underway, to the point where the depth of neutralization reaches the reinforced steel and destroys the protective layer. Moreover, the products of this chemical reaction (e.g. rust) have a larger volume, which can cause cracks. In time, the concrete surface separates from the reinforcement and exposes the steel elements. From this moment, the entire structure becomes affected and it is very clear that the concrete needs to be restored by contractors involved with masonry restoration.