Relative Density and Absorption - Memphis - Civil Handouts/3 - Relative Density...Relative Density Relative density is the mass density of an object relative to the mass density of

  • View
    219

  • Download
    0

Embed Size (px)

Text of Relative Density and Absorption - Memphis - Civil Handouts/3 - Relative Density...Relative Density...

  • Relative Density and Absorption

  • CIVL 3137 76

    Aggregate Moisture

    Dry SSD Wet

  • CIVL 3137 77

    Absorption

    AW

    D

    M% Abs 100%M

    MD

    MAW

  • Question

    A 1-ft3 bucket holds 100 lb. of aggregate. How much volume is occupied by the air and how much by the aggregate particles?

    CIVL 3137 78

  • Particle Density

    Particle density is the ratio of the massof an aggregate particle to its own volume(also called mass density of solids).

    MV

    CIVL 3137 79

  • Relative Density

    Relative density is the mass densityof an object relative to the mass densityof water (also called specific gravity).

    w

    RD w

    M V

    w

    MV

    CIVL 3137 80

  • CIVL 3137 81

    Relative Density

    Relative density depends on the volumeyou assume for the aggregate particles.

    NetVolume

    BulkVolume

  • Apparent Relative Density

    D

    NA

    w

    MR

    VD

    Net volume

    CIVL 3137 82

  • Bulk Relative Density

    D

    BB

    w

    MR

    VD

    Bulk volume

    CIVL 3137 83

  • SSD Relative Density

    SSD

    BSSD

    wVM

    RD

    SSD aggregate

    CIVL 3137 84

  • Example

    An aggregate sample has an oven-dry mass of3954.2 g, an SSD mass of 4006.8 g, and a netvolume of 1532.6 cm3.

    Find RDA, RDB, RDSSD, and %Abs

    CIVL 3137 85

  • Measuring Relative Density

    CIVL 3137 86

  • Measuring Relative Density

    CIVL 3137 87

  • Measuring Relative Density

    w

    MRD

    Vmass of water displaced

    CIVL 3137 88

  • CIVL 3137 89

    Measuring Relative Density

    aggregate

    water displaced

    MRD

    M

  • CIVL 3137 90

    Buoyancy

    Mwater displaced g

    Min water g

    =Min air g

  • CIVL 3137 91

    Measuring Relative Density

    water displaced in air in waterM M M

  • CIVL 3137 92

    Apparent Relative Density

    in air

    Ain

    OD

    ODair in water

    MRD

    M M

    Net volume

  • CIVL 3137 93

    Bulk Relative Density

    in air

    Bin aSSD

    OD

    ir in water

    MRD

    M M

    Bulk volume

  • CIVL 3137 94

    SSD Relative Density

    in air

    SSDi

    SSD

    SSDn air in water

    MRD

    M M

    Bulk volume

  • Achieving an SSD State

    Coarse aggregate should be soaked in room temperature water for 244 h then rolled in a large absorbent cloth to remove all visible surface moisture.

    CIVL 3137 95

  • Achieving an SSD State

    Fine aggregate should be brought to a moisture content of at least 6% and allowed to stand for 244 h. Aggregate is then spread out on a nonabsorbent surface and air is blown across it until it attains a free flowing condition.

    CIVL 3137 96

  • Achieving an SSD State

    CIVL 3137 97