Building Materials: Timber and Concrete
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Questions and Answers

What are the tracheids held together by in timber?

  • Lignin (correct)
  • Cement
  • Cellulose fibre
  • Polyester resin

    • What is a downside of using timber as a resource?

  • It is difficult to work with
  • It is not renewable
  • It can damage fragile ecosystems when removed (correct)
  • It is extremely expensive

    • What is the typical ratio of aggregate to sand to cement in concrete?

  • 2:2:1
  • 4:2:1 (correct)
  • 3:2:1
  • 1:2:3

    • What is the purpose of the cement in concrete?

    <p>To act as a binder</p> Signup and view all the answers

    What is a characteristic of fibre-reinforced polymers?

    <p>They have improved rigidity and impact resistance</p> Signup and view all the answers

    What is an example of a fibre-reinforced polymer?

    <p>Glass fibre in polyester resin</p> Signup and view all the answers

    Why is concrete a stronger material than cement alone?

    <p>Because the aggregate and sand add strength</p> Signup and view all the answers

    What is a natural composite mentioned in the passage?

    <p>Timber</p> Signup and view all the answers

    What is the primary reason for selecting materials with biocompatibility in bio-engineered products?

    <p>To prevent adverse reactions with the body</p> Signup and view all the answers

    What property of stainless steel makes it a suitable material for bio-engineered products?

    <p>formation of a thin oxide layer</p> Signup and view all the answers

    What is the primary advantage of titanium in bio-engineered products?

    <p>Excellent corrosion resistance</p> Signup and view all the answers

    Why are conventional steels not suitable for bio-engineered products?

    <p>They are prone to corrosion and weaken over time</p> Signup and view all the answers

    What is the primary application of titanium in bio-engineered products?

    <p>All of the above</p> Signup and view all the answers

    Why are materials like stainless steel and titanium preferred in bio-engineered products?

    <p>They resist corrosion and are biocompatible</p> Signup and view all the answers

    Study Notes

    Timber

    • Composed of cellulose fibre, tracheids, and lignin, a natural resin
    • Excellent specific strength, but prone to weather damage and pest attacks
    • Renewable resource, but many hardwoods are difficult to replace once felled
    • Removal can harm fragile ecosystems

    Concrete

    • Composite of cement, sand, and aggregate
    • Sand fills gaps between aggregate particles, cement acts as binder
    • Portland cement is a man-made ceramic that reacts with water and sets to a hard, brittle solid
    • Stronger and more efficient than cement alone for large structures and paths
    • Typical composition: 4 parts aggregate, 2 parts sand, 1 part cement

    Fibre Reinforced Polymers

    • Polymers with added fibre for improved rigidity and impact resistance
    • Examples: glass and carbon fibre in polyester or epoxy resins
    • Widely used, with extensive applications in aeronautical fields

    Bio-Engineered Materials

    • Stainless steels, aluminium alloys, and tungsten alloys are commonly used in bio-engineered products.
    • Polymers and ceramics are also important, especially for internal use.

    Importance of Biocompatibility

    • Biocompatibility is crucial when designing devices that are implanted or in contact with the skin.
    • Materials must not react with the body and must remain inert to ensure product integrity and health.

    Stainless Steels

    • Advantages: creates a stable, thin oxide layer that resists corrosion when exposed to atmosphere or body fluids.
    • Conventional steels are prone to corrosion, weakening the material and causing infection or rejection by the body.

    Titanium

    • Derived from minerals rutile and ilmenite (oxide layers).
    • Properties: lightweight, excellent corrosion resistance, high strength-to-weight ratio, and good high-temperature properties.
    • Corrosion resistance is provided by an adherent TiO2 film stable until 535°C.
    • Uses: hip joints, bone screws, knee joints, bone plates, dental implants, and pacemaker cases.
    • Machining properties are comparable to stainless steel.

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    Description

    Explore the characteristics and properties of timber and concrete, two common building materials, including their composition, strengths, and weaknesses.

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