carpentry 1- concrete flatwork

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carpentry 1- concrete flatwork
2014-03-25 00:22:38
carpentry 1- concrete flatwork
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  1. what does the term subgrade refer to?
    the ground or base that is directly under and supporting to the concrete slab
  2. what 2 parts may be included in the base for the concrete slab?
    • 1. sub grade
    • 2. sub base
  3. the prepoaration of the___is just as important as the slab.
  4. what are the properties of problem soils?
    clay and organic soils that are highly expansive or compressive and do not provide uniform support
  5. what is non uniformity?
    when the soil contains both hard and soft spots in close proximity
  6. what can occur when the soil is non uniform?
    point loading- different compression causes a bridging effect  creating cracks
  7. what precautions must be taken when a trench is back filled in a prepare base?
    it must be compressed back to its original density
  8. what is a sub base and under what conditions is it used?
    thin layer of granular material is helpful when it is not possible to level and compact the existing ground to a uniform height and density
  9. what are acceptable materials for a sub base?
    stone, gravel, sand, or a mixture of these
  10. where are slab thickening used?
    for the purpose of carrying greater loads, masonry block work, bearing walls, heavy machinery, and support wall loads
  11. where should reinforcement be placed in the slab?
    lower portions of the slab
  12. under what conditions should a vapour barrier be placed under the slab?
    where water or water vapour may be a problem
  13. where is air-entrained concrete used?
    should be used anywhere it would be subject to freeze thaw cycles (driveways, sidewalks, etc..)
  14. what method can be used to ensure that slab corners are square?
  15. what 2 forces must edge forms be able to resist?
    • 1. buckling- pressure of concrete
    • 2. downward pressure of screeding
  16. list and describe 3 basic types of joints.
    • 1. isolation joints- allow both vertical and horizontal movement between joints
    • 2. control joints- used to control the location of cracking
    • 3. construction joints- used where the pour has been intentionally stopped and will be continued
  17. on what 5 conditions does the spacing of control joints depend?
    • 1. slab thickness
    • 2. shrinkage potential
    • 3. sub-grade friction
    • 4. environment
    • 5. pressure or lack of reinforcement
  18. what is done to the sub-base when no vapour barrier is used?
    surface should be dampened with water to reduce loss of water from concrete to sub-base
  19. what is the most important factor in the screeding and striking off process?
    that it is completed before excess bleed water collects on the surface
  20. what does a low tolerance mean in relation to slab placement quality?
    that higher variations in the slab are allowed
  21. what type of trowel must not be used on air-entrained concrete?
    do not use a steel trowel
  22. what are the 3 goals of the curing process?
    • 1.protect from rapid drying
    • 2. " ¬†"temperature extremes
    • 3. " ¬†"damage from use