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VOLUMETRIC PROPERTIES OF MIXTURES
Maximum Specific Gravity , G (^) mm Specific gravity of an asphalt mixture when there is no air voids. This can be measured by ASTM 2041 test procedure, which is also known as the Rice Test.
Effective Specific Gravity of Aggregate, Gse (for 100 g of mix) = Ps / (100/G (^) mm - Pb /Gb )
100/G (^) mm = Volume of mixture with no air voids Pb/G (^) b = Volume of asphalt
Maximum specific gravities of mixtures, G (^) mm, at different asphalt contents can be computed by assuming that the asphalt absorption is constant and thus the effective specific gravity of the aggregate is constant at all asphalt contents. G (^) mm = 100 / (Ps /Gse + Pb /Gb )
Ps /Gse = Effective volume of aggregate Pb /Gb = Volume of asphalt
Asphalt Absorption , Pba is expressed as a percent by weight of the aggregate
Pba = (100/Gsb - 100/Gse) Gb where 100/Gsb = bulk volume of aggregate 100/Gse = effective volume of aggregate
Effective Asphalt Content , Pbe = Pb - PbaPs / where Pba Ps /100 = % asphalt absorption by weight of mix
Air Voids in Compacted Mixture , P a
= Va / V mb X 100%
= (V mb - (V s + V be)) / V mb X 100%
= (1 - (100/G mm) / (100/Gmb ) ) X 100%
= (1 - G mb/ G mm) X 100%
= ((G mm - G mb )/ G mm) X 100%
EXAMPLES OF COMPUTATION OF
VOLUMETRIC PROPERTIES
Bulk Spe. Gr. of agg., Gsb = 2. Max. Spec. Gr. of mix, G (^) mm = 2. Bulk Spe. Gr. of mix, G (^) mb = 2. % Asphalt , P (^) b = 6.96 % Spec. Gr. Of asphalt, G (^) b = 1.
Effective Specific Gravity of Aggregate, Gse = Ps / (100/G (^) mm - Pb /Gb ) = 93.04/(100/2.438 - 6.96/1.01) = 2.
Asphalt Absorption, Pba = (100/Gsb - 100/Gse) Gb = (100/2.651 - 100/2.726) X 1. = 1.05 %
Effective Asphalt Content, Pbe = Pb - PbaPs / = 6.96 - (1.05)(93.04)/ = 5.
Air Voids in Compacted Mixture, Pa = ((G (^) mm - G (^) mb )/ G (^) mm) X 100% = (2.438 - 2.344)/2.438 X 100% = 3.86%
VMA = 100 - G (^) mb Ps / G (^) sb = 100 - 2.344 (93.04)/2. = 17.73% VFA (Voids Filled with Asphalt) = (VMA - Pa) / VMA X 100% = (17.73 -3.86)/17.73 X 100% = 78.2%
If the alternative definition of VMA is used, VMA = 100 - G (^) mb Ps / Gse = 100 - 2.344 (93.04)/2. = 20.00% VFA = (20.0 -3.86)/20.0 X 100% = 80.7%
