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20 January, 01:09

An aggregate blend is composed of 65% coarse aggregate by weight (Sp. Cr. 2.635), 36% fine aggregate (Sp. Gr. 2.710), and 5% filler (Sp. Cr. 2.748). The compacted specimen contains 6% asphalt binder (Sp. Gr. 1.088) by weight of total mix, and has a bulk density of 143.9 lb/ft^3 Ignoring absorption, compute the percent voids in total mix, percent voids in mineral aggregate, and the percent voids filled with asphalt.

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  1. 20 January, 01:32
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    From the given information:

    Addition of all the materials = 65 + 36 + 5 + 6 = 112 which is higher than 100 percentage; SO we need to find;

    The actual percentage of each material which can be determined as follows:

    Percentage of the coarse aggregate will be = 65 * 112/100

    = 72.80%

    Percentage of the Fine aggregate will be = 36 * 112/100

    = 40.32%

    Percentage of the filler will be = 5 * 112/100

    = 5.6%

    Percentage of the asphalt binder will be = 6 * 112/100

    = 6.72 %

    So; the theoretical specific gravity (Gt) of the mixture can be calculated as follows:

    Gt = 100 / (72.80/2.635 + 40.32/2.710 + 5.6/2.748 + 6.72/1.088)

    Gt = 100 / (27.628 + 14.878 + 2.039 + 6.177)

    Gt = 100 / (50.722)

    Gt = 1.972

    Also; Given that the bulk density = 143.9 lb/ft³

    LIke-wsie; as we know that unit weight of water is = 62.43lb/cu. ft

    Hence, the bulk specific gravity of the mix (Gm) = 143.9/62.43

    =2.305

    The percentage of air void = (Gt - Gm) * 100 / Gt

    = (1.972 - 2.305) * 100 / 1.972

    = - 16.89%

    The percentage of the asphalt binder is = (6.72/1.088*100) / (72.80+40.32+5.6+6.72) / 2.305)

    = 617.647/54.42

    = 11.35%

    Thus; the percentage voids in mineral aggregate = - 16.89% + 11.35%

    the percentage voids in mineral aggregate = - 5.45%

    The percent voids filled with asphalt. = 100 * 11.35/-5.45

    The percent voids filled with asphalt = - 208.26 %
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