PROPERTIES OF FRESH CONCRETE

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PROPERTIES OF FRESH CONCRETE

• Workability
• Definition, is the ease with which the concrete
  can be transported, placed and compacted in such
  a way that there is no segregation of the
  individual constituents.

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PROPERTIES OF FRESH CONCRETE

• TESTS
• Slump - method AS 1012.3.1
• Vebe consistometer method AS 1012.3.3
• Compacting factor method AS 1012.3.2
• Flow

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PROPERTIES OF FRESH CONCRETE

• SLUMP

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PROPERTIES OF FRESH CONCRETE
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PROPERTIES OF FRESH CONCRETE
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PROPERTIES OF FRESH CONCRETE

• Slump tolerances

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PROPERTIES OF FRESH CONCRETE

• Slump limitations
• Different mixes same slump but different
  workability
• Stone size
• Cement content
• Less sensitive at low slumps and very high slumps
  

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PROPERTIES OF FRESH CONCRETE

• Vebe consistometer
• Mould as for slump
• Place disc on top of concrete
• Switch on vibrating table and stop watch
  simultaneously
• Switch off stop watch when disc coated with
  cement paste
• Record time in seconds

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PROPERTIES OF FRESH CONCRETE

• Apparatus

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PROPERTIES OF FRESH CONCRETE

• Compacting factor
• Fill top cone with concrete
• Open trap door to allow concrete to fall into 2nd
  cone
• Open trap door to allow concrete to fall into
  cylinder
• Strike off excess concrete and weigh 1
• Empty cylinder and refill with fresh concrete
  compacting thoroughly
• Determine weight of compacted concrete in
  cylinder 2
• Compacting factor weight1/ weight2
• Higher ratio more workable concrete

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PROPERTIES OF FRESH CONCRETE

• Apparatus

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PROPERTIES OF FRESH CONCRETE

• Concrete flow test

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PROPERTIES OF FRESH CONCRETE

• Air content

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PROPERTIES OF FRESH CONCRETE

• Bleeding of concrete
• Method AS 1012.6
• Place concrete into cylindrical container and
  compact
• Cover and place on level surface
• Draw bleed water off at regular intervals
  record quantity
• Stop when less 5 ml collected in ½ hour period
• Report as
• Volume /unit time/ unit area
• Ratio of bleed water to total mix water

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PROPERTIES OF FRESH CONCRETE

• Yield
• AS 1012.5 ( Mass per unit volume)
• Cylinder of known volume litres
• Place concrete in cylinder and compact thoroughly
  
• Weigh kg
• Density kg/m3 or kg/1000litres 1
• Calculate weight loaded into mixer or truck 2
• If 1lt 2 over yielding or giving material away
• If 1gt 2 under yielding or short delivery