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PROPERTIES OF FRESH CONCRETE

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Switch on vibrating table and stop watch simultaneously. Switch off stop watch when disc coated with cement paste. Record time in seconds ... – PowerPoint PPT presentation

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Title: PROPERTIES OF FRESH CONCRETE


1
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.

2
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

3
PROPERTIES OF FRESH CONCRETE
  • SLUMP

4
PROPERTIES OF FRESH CONCRETE
5
PROPERTIES OF FRESH CONCRETE
6
PROPERTIES OF FRESH CONCRETE
  • Slump tolerances

7
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

8
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

9
PROPERTIES OF FRESH CONCRETE
  • Apparatus

10
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

11
PROPERTIES OF FRESH CONCRETE
  • Apparatus

12
PROPERTIES OF FRESH CONCRETE
  • Concrete flow test

13
PROPERTIES OF FRESH CONCRETE
  • Air content

14
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

15
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
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