Water in all its forms: couples, liquid and ice, it is the greatest and enemy of many materials and structures. Moisture, penetrating into materials, it triggers the mechanism that causes the harmful changes, as a result of physical processes, chemical or biological occurring frequently in relation to each other.
In masonry structures, the appearance of moisture can be caused by:
- air humidity absorption by porous and hygroscopic materials and mortars,
— przenikania pary wodnej w pory i szczeliny i skraplania się jej wewnątrz konstrukcji lub na jej powierzchni,
— zamakania powierzchniowego podczas opadów atmosferycznych lub infiltracji i wsiąkania w mury wody z innych źródeł,
— kapilarnego podciągania wody z podłoża.
Moisture in the structure of walls in historic buildings is the first link in the process of their destruction, especially when the water contains harmful or aggressive additives.
Walls loaded with heterogeneous. structure, containing hygroscopic materials, when saturated with water, they become less resistant to deformation, route with its original strength and bearing capacity.
Water penetrating inside the walls causes swelling of some masonry materials and mortars and gradually dissolves the binding substances. By leaking through the wall, the water contributes to the mechanical rinsing of the mineral components of the mortar and less cohesive grains of materials., which - as mentioned before - is conducive to the intensity of the deflation phenomena, ablation and corrosion.
Water when freezing, turning to ice, increases its volume by approx 9%, thus causing a significant increase in pressure on the surrounding material. Even when the temperature drops to 0 ° C, the pressure on the material wall is approx. 100 kG/cm², (10 MPa), at -10 ° C the pressure rises to 1139 kG/cm², (113,9 MPa), a at —20 ° C to 2050 kG/cm², (205 MPa). As a result of this phenomenon, excessive deformations are created in the material, which in the weaker parts of the structure cross-section cause a violation of the cohesiveness and compactness of the structure, shifting or cracking of stones and bricks as well as epidermal deformations in the form of bulges and separation of layers. Periodic changes in melting and freezing facilitate erosion, and penetration into the interior of other corrosive agents can lead to a catastrophe.
Parts of masonry structures sunk into the ground and in contact with it become damp as a result of this, that the ground is always saturated with Softer or less water. Capillary wicking of water in walls, above, water-saturated ground level, it even comes to 3 m. If the groundwater also contains components that are harmful to building materials (e.g. organic acids, dissolved salts, lyes etc.), then materials and mortars that are not resistant to their action undergo unfavorable transformations, and even disintegrating.