Concrete 4 (physical properties)

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Marciaho
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269750
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Concrete 4 (physical properties)
Updated:
2014-04-08 07:09:10
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Concrete physical properties
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Concrete 4 (physical properties)
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Concrete 4 (physical properties)
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  1. Hardened cement paste
    Consists of several phases
    • Calcium silicate hydrate which provide most of the strength
    • Calcium hydoxide which is a by product of hydration process
    • Calcium sulfoalumiates which are a minor component of HCP
  2. Quality of HCP is influenced by
    • Water/cement ration
    • Water/binder/
    • Binder/typer/combination
    • Age of concrete
    • Curing of concrete
  3. porosity of concrete
    Compaction poresĀ 
    Entrained air
    Capillary pores
    Gel pores
    Why is it important?
    • Compaction pores (1-10mm)
    • Entrained air (0.1-0.3mm)
    • Capillary pores (10nm -100micron)
    • Gel pores (2-10 nanomenters)
    • Porosity is important since concrete is a brittle material
  4. porosity at
    0.6 w/c
    0.5
    0.4
    • 31%
    • 22%
    • 12%
  5. Relationship between porosity and strength equation
    • S = S0(1-P)^n
    • S = property in question
    • S0 = value zero porosity
    • P = Porosity
    • n = constant (3)
  6. What happens with quality aggregate
    It is stronger and stiffer than HCP and failure occurs around agg
  7. Surface of aggregate is characterised in terms of:
    What is it more important for than ___
    • Surface texture (physical interlock with HCP)
    • Chemistry of agg (calcium silica)
    • Cleanness of aggregate (dust and slip layer)

    It is more important for dimensional stability than for strength since paste controls strength
  8. Interfacial transition zone (ITZ) contains the following
    • Less CSH
    • More Calcium hydoxide
    • More ettringite
    • More porosity
  9. effect of ITZ can be limited by
    • Use of rough textured aggregate
    • Use of SCM that reacts with CH
    • Use fine fillers to improve ITZ pacting
    • Use super plasticiser for dispersion
    • Important for high performance strength conretes
  10. Tests for physical properties of concrete
    (5)
    • Compression
    • Flexure
    • Shear
    • Bond
    • Modulus of elasticity
  11. Factors affective concrete strength
    • Intrinsic (materials related)
    • Extrinsic (testing related )
    • factors
    • Concrete has extremely good strength /cost ratio
  12. Extrinsic factors
    that may effect the measure compressive strength include (4)
    • 1. Moisture content at time of testing (dry>wet)
    • 2. Speciment size (small>large)
    • 3. Shape (cube>cylinders)
    • 4. Aspect ration (short>long)
    • Strength is not an inherent property of concrete
    • Additional factors
    • Load rate
    • Eccentricity of load
  13. Intrinsic Factors
    affecting strength
    • Water/cement ratio
    • cement type and proportions
    • Degree of hydration
    • Age of concrete
    • Amount of dispersion times
    • Compaction of concrete
    • Aggregate quality for HCP
    • Mix design for bleeding and segregation
  14. Compressive strength testing
    • load rate of 10-20MPa /min
    • check cracking pattern
    • square and flat ends
    • Diamete four times agg
  15. Concrete will continue to gain strength as long as:(3)
    • Some hydrated cement remains
    • concrete remains moist (relative humidity >80%)
    • Temperature is above freezing
  16. Strength development - effect of temperature
    Increased temp = increased rate of hydration = increased strength early age= decrease long term strength
  17. Cement paste and aggreate both have ____ behaviour
    linear
  18. How is tensile strength of concrete determing
    • Cylinder splitting test
    • Flexural test

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