Properties of Materials

Properties of Construction Materials

Understanding the properties of materials is crucial for any civil engineer. These properties determine how a material will behave under load, how it will react to the environment, and how long it will last.

Physical Properties

Physical properties are those that can be observed or measured without changing the composition of the material.

Common physical properties include:

• Density ($\rho$): $\rho = \frac{m}{V}$
• Specific Gravity ($G_s$): $G_s = \frac{\rho_{material}}{\rho_{water}}$
• Porosity ($n$): The ratio of the volume of voids to the total volume.
• Void Ratio ($e$): The ratio of the volume of voids to the volume of solids.
• Moisture Content ($w$): The ratio of the mass of water to the mass of solids.

Mathematical Relationships

The relationship between void ratio and porosity is given by:

The relationship between saturation ($S$), void ratio ($e$), specific gravity ($G_s$), and moisture content ($w$) is:

Mechanical Properties

Mechanical properties describe how a material responds to applied forces.

Key mechanical properties:

• Strength: The ability to resist loads without failure (Compressive, Tensile, Shear).
• Elasticity: The ability to return to original shape after deformation. Young's Modulus ($E$) measures stiffness.
• Ductility: The ability to undergo significant plastic deformation before rupture.
• Brittleness: The tendency to fracture with little or no plastic deformation.
• Toughness: The energy absorbed by a material up to fracture (area under stress-strain curve).
• Hardness: Resistance to indentation or scratching.

Chemical and Thermal Properties

• Chemical Resistance: Ability to resist chemical attack (e.g., sulfates, acids).
• Corrosion Resistance: Resistance to deterioration by oxidation or galvanic action.
• Thermal Conductivity: Rate of heat transfer through the material.
• Thermal Expansion: Change in volume or length with temperature change.

Where $\alpha$ is the coefficient of thermal expansion.