Engineering Chemistry - Building Materials

Engineering Chemistry - Lecture: Building Materials

• Cement is a material with adhesive and cohesive properties, enabling it to bond minerals.
• Egyptians used lime and gypsum mortar for pyramids.
• Greeks used lime mortar.
• Romans produced cement from siliceous-aluminous volcanic ash material.

Cement Industry

• Raw Materials:

  • Limestone: primary source of calcium oxide
  • Clay and clay-like materials: source of alumina and silica. These are also added from additional resources like slag, bauxite, iron ore, silica, and sand.
  • Gypsum (2-3%): added to regulate setting time.
  • Iron source
  • Sand

• Manufacturing Methods:

  • Wet process: Grinding and mixing raw materials in water
  • Dry process: Grinding and mixing dry raw materials

• Process Description:

  • Raw materials are mined, crushed, and transported
  • Raw materials are mixed, preheated, and dried
  • Clinker is prepared in a rotary kiln
  • Clinker is mixed with gypsum
  • Final product, cement, is then stored and packaged.

Cement Properties

• Setting and Hardening

  • Setting: Initial stiffening due to gel formation.
  • Hardening: Mechanical strength development.
  • The initial setting time is 45 minutes, and the final setting is 10 hours.
  • Gypsum is added to regulate setting time to slow hydration and prevent very rapid setting.

• Clinker Compositions

  • Dicalcium silicate (C₂S)
  • Tricalcium silicate (C₃S)
  • Tricalcium aluminate (C₃A)
  • Tetracalcium aluminoferrite (C₄AF)

Types of Cement

• Regular Portland cement: General construction use (not in soils or groundwater.)
• Sulfate resistant Portland cement: Used in construction exposed to sulfate attack.
• Rapid hardening Portland cement: For projects needing quick strength development.
• Low heat of hydration Portland cement: Low-heat of hydration, slower strength development, good for large structures.
• White Portland cement: White colored, no iron oxide.
• High alumina cement: Chemical resistance to corrosion.
• Oil-well cement: High C₂S and C₃S for low heat of hydration, coarser.
• Blended cements (Slag-rich, sand/limestone): Reduce cost, resistance to sulfates, chloride.

Glass

• History:

  • Glass production dates back thousands of years.
  • Egyptians and other early civilizations valued glass.
  • Modern glass production is efficient and productive.

• Properties:

  • Amorphous, inorganic, homogeneous, and transparent material.
  • Can be molded into various shapes.

• Manufacturing:

  • Raw materials (sand, limestone, soda ash, etc.) are crushed and mixed.
  • Mixed materials are melted in a furnace (typically 1500°C.)
  • Molten glass is formed and cooled.

• Types of Constructed Glass:

  • Common flat glass: Windows, doors
  • Float glass: Shopfronts, public places
  • Shatterproof glass: Added plastic so it doesn't shatter into pieces.
  • Laminated glass: Layers of glass with plastic interlayers.
  • Tempered glass: Strong, for impact resistance
  • Glass blocks: Walls, skylights.
  • Glass wool, fiber glass, insulated glazed units.