6506-9 - COMPUTATION OF VOLUMETRIC PROPERTIES IN THE...

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1 COMPUTATION OF VOLUMETRIC PROPERTIES IN THE MARSHALL MIX DESIGN EXAMPLE Bulk spec. grav. of agg., G sb = 2.683 Max. size = 1/2 in. Spec. grav. of asphalt, G b = 1.05 At 6.5% asphalt, max. spec. grav. of mix , G mm = 2.463 Effective spec. grav. of agg., G se = P s / (100/G mm -P b /G b ) = 93.5/(100/2.463 - 6.5/1.05) = 2.717 Asphalt Absorption, P ba = (100/G sb - 100/G se ) G b = (100/2.683 - 100/2.717) X 1.05 = 0.5 % RESULTS OF 50-BLOW MARSHALL TEST %AC G mb Stability, Lb. Flow, 1/100 in. 5.5 2.348 800 8 6.0 2.364 1300 11 6.5 2.360 1710 13 7.0 2.353 1850 17 7.5 2.341 1575 22
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2 SAMPLE CALCULATIONS At 6.0% asphalt, Maximum specific gravities of mixture, G mm = 100 / (P s /G se + P b /G b ) = 100 / (94/2.717 + 6/1.05) = 2.481 Air Voids in Compacted Mixture, P a = ((G mm -G mb )/ G mm ) X 100% = (2.481 - 2.364)/2.481 X 100% = 4.72% Maximum specific gravities of mixture, G mm can also be computed by the following equation: G mm = 100 / (P s /G sb + (P b -(P ba P s /100)) / G b ) = 100 / (94/2.683 + (6.0 - 0.005 X 94)/1.05 = 2.481 The same value of G mm is obtained in both cases.
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3 VMA = 100 - G mb P s / G sb = 100 - 2.364 (94)/2.683 = 17.18% If the alternative definition of VMA is used, VMA = 100 - G mb P s / G
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6506-9 - COMPUTATION OF VOLUMETRIC PROPERTIES IN THE...

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