Lecture 6-Glass

Introduction to Glass in Construction

  • Great Building Material: Glass fosters visual relationships between the inside and outside of buildings.

  • Materials Used: Made primarily from

    • Sand (silica)

    • Lime (calcium oxide)

    • Soda (sodium oxide)

  • Recyclable Material: Glass is an eco-friendly choice due to its recyclability.

Characteristics of Glass

  • Properties: Hard, brittle, and may be transparent or translucent.

  • Production Process:

    • Fused from soda, lime, and silica along with minor additives (magnesia, alumina).

    • Cools to a solid state without crystallization.

Production Methods

  • Blown Glass: Challenging for flat pieces.

  • Moulding: Glass is shaped using molds.

  • Rolling: Moistened glass is drawn between rollers.

  • Float Glass: Created by pouring molten glass onto molten tin, heated to 1500°C.

Float Glass Production History

  • Sir Alastair Pilkington's Process (1952):

    • Initially produced 6mm thick glass.

    • Current productions range from 0.4mm to 25mm.

    • Facilities operate continuously for 11-15 years producing 6000km of glass, 3m wide.

Composition of Float Glass

  • Raw Material Composition:

    • Sand: 72.6%

    • Soda Ash: 13.0%

    • Limestone: 8.4%

    • Dolomite: 4.0%

    • Alumina: 1.0%

    • Other materials: 1.0%

Forming Process of Float Glass

  1. Batching Raw Materials:

  • Quantities of silica, soda, calcium oxide, and magnesium ( 73%, 13%, 9%, 4% ) mixed with cullet to improve efficiency.

  • Cullet reduces energy consumption.

  1. Melting:

  • Materials melted in a 5-chamber furnace at approximately 1500°C.

  1. Drawing:

  • Molten glass is floated onto 1100°C tin bath forming ribbons of glass (width: 3210mm; thickness: 3-25mm).

  1. Cooling:

  • Processed in an annealing lehr, allowing internal stresses to dissipate and ensuring flatness. No polishing required.

  1. Quality Checks: Glass cooled, checked for quality, washed, cut into sheets, and stored.

Glass Treatments for Strength

  • Strengthening Methods:

    • Annealed Glass: Basic glass; easily broken, sharp shards.

    • Heat Strengthened: 2x stronger, less distortion, breaks like annealed glass.

    • Tempered Glass: 4x stronger, small granule breakage, regulated by law near floors.

    • Other methods include laminated glass which retains fragments when broken.

Types of Glass

  • Glass Fibers: Used in GRP, GRC, GRG, etc., providing a variety of applications.

  • Glass Blocks: Single or hollow blocks, available in various sizes with thermal and sound insulation properties.

Applications of Different Glass Types

  • Float Glass: Clear applications for windows and display surfaces.

  • Patterned Glass: Provides obscurity and diffusion, suitable for offices and restrooms.

  • Wired Glass: Fire resistance with safety mesh.

  • Laminated Glass: Retains fragments, high UV blockage.

  • Decorative Laminated Glass: Custom colors and patterns available.

Additional Glass Types and Technologies

  • Heat-Absorbing Glass: Blends metal oxides to reduce interior heat, used in large buildings.

  • Reflective Glass: Reflects sunlight, commonly for aesthetic and privacy purposes.

  • Insulating Glass: Double layers designed to prevent heat loss and improve sound insulation.

  • Low-E Glass: Coating reduces heat flow, highly efficient for temperature control.

  • Anti-Reflective Glass: Allows maximum transparency and is used where clarity is critical.

  • Self-Cleaning Glass: Uses a UV-activated coating to break down dirt and debris.

Maintenance Challenges

  • Cleaning Requirements: Glass cleaning can be labor-intensive and difficult in high-rise buildings.

  • Lotus Leaf Effect: Mimics natural self-cleaning surfaces, promoting dirt removal with minimal water use.

References

  • Foster, J. S. & Greeno, R., 2008. Structure and Fabric: Pt. 1. Prentice Hall.

  • Emmitt, S. & Gorse, C., 2005. Introduction to Construction of Buildings. Blackwell Publishing.

  • Allen, E. & Iano, J., 2008. Fundamentals of Building Construction: Materials and Methods. Wiley.

  • Chudley, R. & Greeno, R., 2004. Building Construction Handbook. Elsevier.

  • Ching, F. D. K., 2008. Building Construction Illustrated. Wiley.