Water absorption and humidity
The practical significance of this property is significant; Water, getting into the pores, weakens the connection of particles, so the strength of the materials saturated with water decreases: for example, the strength of brick saturated with water decreases by 25% of its strength in a dry state, and the undigested brick, being saturated with water, slides and does not have any strength. Wet materials become more thermal.
To determine the water absorption, the sample of the material is pre -dried and weighed, then immersed in the water and left in it until the increase in weight stops, t. e. to constant weight. Boiling in water accelerates the saturation process. After saturation with water, the sample is again weighed. The difference in the weight of the sample saturated with water, and dry, attributed to weight in a dry state, determines the degree of water supply, t. e. water absorption.
Water saturation of the material can occur not only when it is completely immersed in water. Even if the material is in contact with water with only one surface, then the water will be absorbed in the pores and saturate the material. This phenomenon of water absorption depends on the form of the pore. If the pores are very small in the cross section, no more than the thickness of the hair and extended in length, then the water rises up and the higher, the higher, the more than they are already. Such pores are called capillaries, and the phenomenon itself with capillary absorption. The penetration of dampness through the foundation into the walls is based on this property if the insulating layer between the foundation and the wall is poorly made, as well as the penetration of moisture into the wall when wetting it with rain.
The ability to resist the destructive action of external forces is called strength. External forces, depending on their direction, act differently on the material: some are compressed, others stretch, others bend. Each of the strength can surpass the resistance of the material and destroy it: for example, the compressive power to crush, and the stretching force – to break. Each material is differently resists of differently components. Iron equally resists both compressive and stretching efforts.
