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## why is it important to study the properties of building materials?

Building materials are playing an important role in modern technology. It is impossible to construct anything without them. Also, the building materials industry is an important contributor to the economical growth of our nation. Before using them, it is very important to know about their important properties. These properties of substances affect the quality of construction work. Some important physical and mechanical properties are given below.

### Physical properties building materials

1. Density
2. Bulk density
3. Specific gravity
4. Porosity
5. Void ratio
6. Water absorption
7. Weather resistance
8. Water permeability
9. Frost resistance
10. Heat conductivity
11. Fire resistance
12. Refractoriness
13. Chemical resistance

### Density :

Density is the measure of mass per unit volume of material. The density of an material equals its total mass divided by its total volume.

Density = M/V kg/m3

M = Mass (g)

V = volume (cm3)

Density of some materials is as follows:

(Please note this is for reference purpose only and may vary from place and type of material.)

### Bulk density :

Bulk density is the measure of mass per unit volume of material in its natural state (with pores and Voids). For most materials, bulk density is less than density but for liquids and materials like glass and dense stone, these parameters are practically the same.

Bulk density = M/V kg/m3

Where

M = mass of specimen (kg)

V = volume of material in its natural state (m3)

Read more : Bulk density test of aggregate

Bulk density of some materials is as follows:

(Please note this is for reference purpose only and may vary from place and type of material.)

### Specific gravity

Spacific gravity of a material is the ratio of weight  of a given volume of solids to the weight of an equal volume of water at 4°C and other word specific gravity is ratio of the density of a substance to that of a standard substance.

### Porosity

Porosity is the degree to which volume of the material of the material is interspersed with pores. It is expressed as a ratio of the volume of pores to that of the material.

Porosity gives us more indication about the other properties of material, such as bulk density, heat conductivity, durability, etc. Those with low porosity are used for construction such as dense materials

### Void Ratio

Void ratio is the ratio of volume of voids (Vv) to the volume of solids (Vs).

Void ratio =  Vv / Vs

### Water absorption

Water absorption is ability of any material to absorb water. It is expressed as percentage in weight. The properties of building materials are greatly influenced the quality of construction when it saturated.

Ww = {(M1 –M) / M }× 100

where  M1 = Weight of saturated material (g)

M =  Weight of dry material (g)

### Weather Resistance

Weather resistance is the ability of a material to withstand alternating wet and dry conditions. For a long period without considerable distortion and loss of mechanical strength.

### Water permeability

Permeability  is the capacity of a material to allow water to penetrate. Materials like glass, steel and bitumen are impermeable.

## Frost Resistance

Frost resistance refers to the ability of a water-saturated material to endure repeated freezing and thawing with considerable decrease of mechanical strength.

In such situations, when the water is filled in the pores, it increases its volume up to 9 percent. Due to volume increase, walls experience a lot of stress and this can also cause wall failure.

### Heat conductivity

Heat conductivity is the ability of a material  to conduct heat. This ability is influenced by the nature of these of substances, its composition, porosity, character of holes and the temperature at which heat exchange would occur.

Materials with larger pores have higher heat conductivity because they have air inside them, These holes increase the heat transfer. Moist materials have higher heat conductivity than dryers. These properties of materials are a major concern for materials used in building construction.

### Fire Resistance

Fire resistance is the ability of a material to resist action without any high temperature deformation and substantial loss of strength. Fire retardant materials are those that ignite with difficulty when ignited or subjected to high temperatures.

Non-combustible material neither ignites nor char under the action of temperature. Some materials neither crack nor lose shape such as clay bricks, while some others such as steel suffer considerable deformation under high temperature action.

### Refractoriness

Refractivity is the ability of a material to withstand prolonged action of high temperatures without melting or losing shape. Materials that resist long temperatures of 1580 ° C or more are known as refractories. High melting materials can withstand temperatures from 1350–1580 ° C, while low melting Materials withstand temperatures below 1350 ° C.

### Chemical resistance

Chemical resistance is the ability of a material to withstand acid, alkali, ocean action water and gases. Natural stone materials, e.g. Limestone, marble, and dolomite have also been erased by weak acids, wood has low resistance to acids and alkalis, bitumen disintegrates under the action of alkali liquors.

## Mechanical properties building materials

The important mechanical properties for building materials are:

1. Strength
2. Hardness
3. Plasticity
4. Elasticity
5. Abrasion resistance

### Strength

Strength is the ability to resist failure under the action of stresses due to loads. The most important is compression, tension, bending and impact

The importance of studying different strengths will be highlighted by the fact that materials like stone and concrete has high compressive strength, but low in tensile, bending and impact Strength.

Compressive Strength tested by standard cylinders and cubes.

Tensile strength is the  maximum load that a material can resist without fracture when being stretched. Metals are tested in the form of round bars for tensile strength.

Bending strength tests are performed on small bars (beams) that are supported at their ends and Subjected to one or two concentrated loads that rise slowly until failure occurs.

### Hardness

Hardness is the ability of a material to resist penetration by a hard body. Mohs scale is used to check the hardness of materials

### Elasticity

Elasticity is the ability of a material to return to its initial form and dimension after removing the load. Within the limits of elasticity of solid bodies, the deformation is proportional to the stress. The ratio of unit stress to unit transformation is called as modulus of elasticity. A large value of it represents a material with very small deformation.

### Plasticity

Plasticity is the ability of any material to change its shape without cracking and under load, and maintain this shape after the load is removed. Some examples of plastic materials are steel, Copper.