DB-U Prep.

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  1. Which Australian Standard applies to footings and slab construction?
    AS 2870-2011 Residential Slabs and Footings
  2. What is the meaning of site classification?
    AS 2870-2011

    • The meaning of site classification determines the expected movement of the site. All necessary investigation must be undertaken to provide sufficient information to adequately design the proposed structure. 
    • The amount of testing can be can be reduced if sufficient previously collected data can be obtained. 
  3. Why are there different classifications?
    There are different site classifications because footings must be designed in accordance with the different levels of site movement. Highly reactive soils require a more extensive footing design and the opposite is true for slightly or non-reactive sites.
  4. What is the maximum spacing of bar chairs?
    NCC Steel Reinforcing 

    800cts MAX for steel fabric.
  5. What concrete cover is required for reinforcing in a slab?
    NCC Steel Reinforcing

    • 40mm for unprotected ground
    • 30mm to membrane in contact with the ground
    • 20mm to an internal surface
    • 40mm to external exposure

  6. How would you recognise the difference between Trench Mesh and Slab Mesh?
    NCC Steel Reinforcing

    • Slab Mesh (Square Mesh) is detailed in terms of diameter of bars and spacings of bars.               Example: SL82 is 8mm diameter bars @ 200mm spacings.
    • Trench Mesh is detailed in terms of number of longitudinal bars and diameter of bars.            Example: 3-L11TM is 3 longitudinal bars which are 11mm in diameter.
  7. What does a slump test measure?
    NCC Concrete

    • A slump test measures how workable a concrete mix is and measured in millimetres. 
    • High slump = Sloppy
    • Low slump = Stiff

    Dont add water to mix onsite. Specify required slump when ordering concrete.
  8. What is the maximum slump allowed in concrete used in a slab?
    NCC Concrete

    • Max 100mm
    • Nominal 80mm
    • Min 60mm
  9. How long can a slab be before introducing an articulation joint?
    AS 2780-2011 Page 21

  10. What is the maximum distance drains should be placed away from footings?
    NCC - Page 116

    Suitable area for excavation in accordance with embankment slope ratio H:L
  11. Specify the requirements for a slab given the building type and soil type.
    NCC Fig.
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DB-U Prep.
2014-12-07 03:38:05
Concrete Slab Footings

Concrete Slabs and Footings
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