Civil engineering materials

UNIT – II

Chapter - 4

CIVIL ENGINEERING MATERIALS

CIVIL ENGINEERING MATERIALS

Civil Engineering Materials are also known as Building Construction Materials. These are obtained from Nature in their natural condition or after conversion by manufacturing processes. Various construction materials are: Bricks, Stones, Sand, Cement, Concrete, Steel Sections, etc.

1. PROPERTIES OF BUILDING CONSTRUCTION MATERIALS

a. Physical Properties

1. Density: Density is defined as the mass of a material per unit volume.

2. Bulk Density: It is defined as weight of material per unit volume.

3. Specific Gravity: It is a dimensionless quantity. It is the ratio of density of a material to the density of water.

4. Porosity: It is the ratio of volume of voids in a material to the volume of granular materials.

5. Water Absorption: It is the property of the material to absorb water and retain it. It is expressed as a percentage in weight of absorbed water to the weight of dry material.

6. Permeability: It is the property of the material to allow water to flow through it. Soil has this property. Dense materials like steel, glass, etc., are waterproof or impervious to water.

7. Weathering Resistance: It is the ability to sustain alternating changes in wet and dry conditions of weather. Materials with good weathering resistance do not undergo considerable changes in dimensions and also in mechanical strength.

8. Durability: It is the ability to resist combined effects of atmosphere and other factors.

9. Thermal Conductivity: It is the ability of material to transfer heat. Example: Metals.

10. Fire Resistance: It is the property by virtue of which a material resists the action of high temperature without undergoing substantial change in shape and loss of strength.

11. Corrosion: It is the destruction of a material due to slow oxidation.

12. Soundness: A material is said to be sound, if it has good resistance to heat, alternate freezing and thawing and other destructive actions of the atmosphere.

13. Chemical Resistance: It is the ability to withstand the actions of acids, alkalis, gases, etc.;

b. Mechanical Properties

Resistance to various applied forces is referred as Mechanical Properties.

1. Strength: For designing the structural elements, the following strength properties of the construction materials are necessary:

(i) Tensile Strength: It is the maximum stress (resistance per unit area) that the material can resist tensile load or tensile force.

(ii) Compressive Strength: It is the maximum stress that the material can resist compressive load or compressive force.

(iii) Shear Strength: It is maximum stress the material can resist shearing force.

2. Fatigue: Wherever repeated loading occurs, fatigue property is to be considered.

3. Hardness: It is the ability of the material to resist penetration by another material.

4. Elasticity: When an external force acts on a body, in undergoes some deformation. The property by which a body returns to its original shape after the removal of external load is called Elasticity.

5. Plasticity: Plasticity is the converse of elasticity. It is the property of the material by which it retains its deformed (changed) shape and size, after the external load is removed. It is a required property when the material is to be moulded into different shapes.

6. Abrasive Resistance: This is the property of a material to resist the forces acting at contact surfaces, when one material moves over the other.

7. Ductility: It is the ability of a metal to withstand elongation or bending. Due to this property, wires are made by drawing out through a hole.

8. Brittleness: When a body breaks easily when subjected to shocks, it is said to be brittle.

9. Toughness: Toughness is the strength of a material to absorb energy without fracture.

2. BIS SYMBOLS OF BUILDING MATERIALS IN SECTIONS (IS : 962 - 1967)