KC

In-depth Study on Building Material Properties

Properties Generally

Overview of Properties

  • Properties pertinent to specific materials are discussed in other chapters.
  • This chapter covers general properties of building materials:
  • Density and specific gravity
  • Strength
  • Optical properties
  • Electrical properties
  • Thermal properties
  • Acoustic properties
  • Deformations
  • Deterioration
  • Appearance

1. Density and Specific Gravity

  • Density: Mass per unit volume, important for assessing material weight and loading.
  • Specific Gravity: Ratio of the density of a substance to the density of water at 4°C, used for various calculations.
  • Reference table of densities for common materials provided for practical use.

2. Strength

  • Definition: Ability of materials to support their own weight and applied loads without distortion.
  • Key readings include:
  • The New Science of Strong Materials by J E Gordon.
  • Strength Types:
  • Tensile Strength: Resistance against being pulled apart.
  • Compressive Strength: Resistance against being compressed.
  • Shear Strength: Resistance against forces causing sliding.
  • Behaviour of materials changes based on:
  • Moisture content (particularly in timber).
  • Load rates and frequencies.
  • Temperature impacts on materials (e.g., plastics).
  • Elastic vs. Plastic Failure:
  • Elastic materials revert to original shape post-load; plastic materials do not.
  • Ductility versus Brittleness:
  • Ductile materials can deform significantly before fracturing.
  • Brittleness: material fractures without significant deformation.
  • Creep: Gradual deformation under constant load over time.

3. Optical Properties

  • Reference materials related to optical properties are discussed under specific chapters (e.g. Glass).

4. Electrical Properties

  • For detailed information, refer to relevant sections in the chapters.

5. Thermal Properties

  • Thermal Conductivity (k): Measure of heat transfer through materials.
  • Defined as Watts (J/s) per unit thickness (m) over unit area (m²).
  • Thermal Resistivity (1/k): Opposition to heat flow, calculated from conductivity.
  • Effective insulation characteristics vary with thickness and surface types:
  • Optimum insulation achieved with sealed cavities.
  • Humidity Impact: Moisture materially alters thermal conductance (20% moisture can triple heat transmission).

6. Acoustic Properties

  • Sound insulation is achieved through mass and natural barriers.
  • Types of sound absorption properties:
  • Porous Materials: Absorb at higher frequencies.
  • Resonant Panels: Absorb at lower frequencies (specific designs).
  • Use of fallen materials is important for sound insulation and fire resistance considerations.

7. Deformations

  • Deformation types include:
  • Movements from applied loads.
  • Changes in moisture and temperature.
  • Restraint can lead to additional stresses and deformities in building materials.

8. Deterioration

  • Common deteriorating factors include:
  • Corrosion, sunlight, biological factors, and water.
  • Solutions for prevention include using resistant materials and appropriate design strategies.

9. Appearance

  • Factors influencing the appearance of buildings incorporate structural forms and chosen materials.
  • Economic considerations often guide the choice of materials with lower maintenance needs.