Several materials are required for construction. The materials used in the construction of Engineering Structures such as buildings, bridges and roads are called Engineering Materials or Building Materials. They include Bricks, Timber, Cement, Steel and Plastics. The materials used in Civil Engineering constructions can be studied under the following headings.
- Traditional materials
- Alternate building materials
- Composite materials
- Smart materials
It is necessary for an engineer to be conversant with the properties of engineering materials. Right selection of materials can be made for a construction activity only when material properties are fully understood.
Some of the most important properties of building materials are grouped as follows.
|Physical||Shape, Size, Density, Specific Gravity etc.,|
|Mechanical||Strength, Elasticity, Plasticity, Hardness, Toughness, Ductility, Brittleness, Creep, Stiffness, Fatigue, Impact Strength etc.,|
|Thermal||Thermal conductivity, Thermal resistivity, Thermal capacity etc.,|
|Chemical||Corrosion resistance, Chemical composition, Acidity, Alkalinity etc.,|
|Optical||Colour, Light reflection, Light transmission etc.,|
|Acoustical||Sound absorption, Transmission and Reflection.|
|Physiochemical||Hygroscopicity, Shrinkage and Swell due to moisture changes|
- Density: It is defined as mass per unit volume. It is expressed as kg/m3.
- Specific gravity: It is the ratio of density of a material to density of water.
- Porosity: The term porosity is used to indicate the degree by which the volume of a material is occupied by pores. It is expressed as a ratio of volume of pores to that of the specimen.
- Strength: Strength of a material has been defined as its ability to resist the action of an external force without breaking.
- Elasticity: It is the property of a material which enables it to regain its original shape and size after the removal of external load.
- Plasticity: It is the property of the material which enables the formation of permanent deformation.
- Hardness: It is the property of the material which enables it to resist abrasion, indentation, machining and scratching.
- Ductility: It is the property of a material which enables it to be drawn out or elongated to an appreciable extent before rupture occurs.
- Brittleness: It is the property of a material, which is opposite to ductility. Material, having very little property of deformation, either elastic or plastic is called Brittle.
- Creep: It is the property of the material which enables it under constant load to deform slowly but progressively over a certain period.
- Stiffness: It is the property of a material which enables it to resist deformation.
- Fatigue: The term fatigue is generally referred to the effect of cyclically repeated stress. A material has a tendency to fail at lesser stress level when subjected to repeated loading.
- Impact strength: The impact strength of a material is the quantity of work required to cause its failure per its unit volume. It thus indicates the toughness of a material.
- Toughness: It is the property of a material which enables it to be twisted, bent or stretched under a high stress before rupture.
- Thermal Conductivity: It is the property of a material which allows conduction of heat through its body. It is defined as the amount of heat in kilocalories that will flow through unit area of the material with unit thickness in unit time when difference of temperature on its faces is also unity.
- Corrosion Resistance: It is the property of a material to withstand the action of acids, alkalis gases etc., which tend to corrode (or oxidize).