4. Wind damage to concrete surfaces

Particles of various materials suspended in the air are stirred up and transported by the wind. When these particles strike a wall, they do so with a certain kinetic energy, which is a function of the mass and speed (squared) of the grains. Depending on the nature of the wall, its elasticity and roughness, the particles may adhere or rebound. These points of impact, constantly renewed, can cause local micro-destruction. Wind speed plays an important role, depending on a number of factors: altitude, turbulence; screens create obstacles. Depending on the orientation of the walls to the prevailing winds, erosion will be more or less significant.

Air pollutants fall into two categories: solid and liquid particles.

The most abrasive particles are hard rock debris (quartz), iron oxides, cement, coal and so on. Depending on their diameter, the...