Physical properties of materials for roofing

The physical properties are as follows:
- Density;
- Porosity;
- Water absorption;
- Water yielding;
- Hygroscopicity;
- Permeability;
- Frost;
- Thermal conductivity;
- Absorption;
- Fire resistance;
- Fire resistance, and others.

The density of the material is high and true. The average density is determined by the ratio
body weight (brick, stone, etc.) to the entire volume occupied by them, including those already in it pores and voids, and is expressed as a ratio of kg / m
True density - is the limit of the mass of a volume, excluding those already in it voids and pores.
In dense materials, such as in steel and granite, the average density is almost equal to the true, the porous (brick, etc.), it is smaller.

This characteristic is determined by the number of pores in the material volume, which is calculated as a percentage. Porosity affects the material properties such as strength, water absorption, thermal conductivity, frost, etc.
Largest since the materials are divided into fine-pore, in which the pore size is measured in hundredths or thousandths of a millimeter, and the large pore (pore size from tenths of a millimeter to 2.1 mm). Porous building materials varies widely. So, for example, glass and metal, it is zero, the brick porosity is 25-35%, in mipory - 98%.

Water yielding capacity
This property describes the ability of the material to lose its pores being in the moisture. Water yielding calculated percentage of water which loses material at ambient relative humidity 60% and a temperature of 20 ° C.
Water yielding capacity is of great importance for many materials and products, such as wall panels and blocks that are in the process of construction of the building generally have higher humidity, and under normal conditions of water loss due to dry (the water evaporates as long as the balance between moisture and humidity of the wall material ambient air, that is, until the material reaches the air-dry state).

Water absorption
Water absorption - is a material's ability to absorb and retain moisture in its pores.
By volume of water absorption is always less than 100%, and the mass can be more than 100%, such as in thermal insulation materials. Water saturation of the material affects its main properties, increases the thermal conductivity and the average density, reduces the strength.
The reduction in strength of the material at the limit of its water saturation is called the water resistance and is characterized by a coefficient of softening.
Materials by a factor of at least 0.8 softening referred to as water-resistant. They are used in the construction in the water, and in areas with high humidity.

Hygroscopic properties - a property of porous materials absorb moisture from the air. Hygroscopic materials (wood, insulation materials, brick dry pressing, etc.) can absorb large amounts of water. This increases their weight, decreased strength, resized.
Some materials in high humidity and even had to use a normal protective coatings.
A material such as bricks dry pressing, can be used only in areas with low humidity.

Permeability is the ability of the material to pass water under pressure. This characteristic is determined by the amount of water held at a constant pressure for 1 hour through the material of 1 m and a thickness of 1 m
To include waterproof especially hard materials (steel, glass, asphalt) and dense materials with closed cell foam (eg concrete specially selected composition).

Frost resistance - the ability of the material in the saturated water can withstand repeated freezing and thawing without sacrificing strength and weight, and without cracks, delamination, crumbling.
For the construction of foundations, walls, roofs and other parts of the building were exposed to repeated freezing and thawing should use materials increased hardiness. Dense materials that do not have time, or materials with low porosity, with water absorption less than 0.5% have a high resistance to frost.

Thermal conductivity
Thermal Conductivity - ability of material to transfer heat in the presence of the temperature difference between the outside and inside the building. This feature depends on several factors: the nature and structure of the material, porosity, moisture content, and the average temperature at which the transfer of heat. And large pore crystalline materials are generally more thermal conductivity than amorphous materials and finely porous structure. Materials having closed pores have lower thermal conductivity than materials with communicating pores. Uniform thermal conductivity of a material depends on the average density: the lower the density, the lower the thermal conductivity, and vice versa. Thermal conductivity of moist materials more than dry, because the thermal conductivity of water is 25 times higher thermal conductivity of air. From this figure depends on the thickness of the walls and floors of heated buildings.

Sound absorbing
Sound absorption ability of a material to weaken the volume as it passes through the material. Absorption depends on the structure of the material: communicating open pores absorb sound better than closed. Indicators have the best sound-layered walls and partitions with alternating layers of porous and dense materials.

Fire resistance
Fire resistance - the ability of materials to withstand high temperatures. According to the fire resistance of materials is divided into non-combustible, flammable and nonflammable. Fireproof materials (brick, concrete, steel) in a fire or high temperature non-flammable, not smoldering and charred, but can strongly deformed. Nonflammable material (fiberboard, asphalt concrete) and smoldering charred, but after removal of the source of fire, these processes are terminated. Combustible materials (wood, roofing material, plastic) or smoking ignite and continue to burn or smolder and after removal of the source of fire.

Fire resistance - a property material to withstand without deformation, prolonged exposure to high temperatures. According to the degree of fire resistance material divided by fireproof, resistant to temperatures up to 1580 ° C and above (fireclay brick), refractory, can withstand temperatures of 1350-1580 ° C (refractory bricks) and fusible, soften or disintegrate at temperatures below 1350 ° C (ceramic brick).
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