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LPC Bituminous Mixtures Design Guide- Mix Design Procedure -3.5.4 Percentage of voids at 10 gyrations: v 10The percentage of voids at 10 gyrations represents the state of the materialsubmitted to very weak energy. The kind of mix that when exposed to such weakenergy yields a low percentage of voids would actually display excessive workability;it is likely that this result stems from weak internal friction of the granular skeleton,wherein lies the potential risk among more ordinary mixes (AC-BBSG, AC-GB, etc.)of offering only limited resistance to rutting. This risk gets taken into account in thespecifications on certain products, whose threshold has been set lower (9% to 14%).Such a criterion was selected within the scope of EN standards, yet due to itsempirical relation with rutting resistance cannot be imposed at the same time(overspecification).3.5.5 Percentage of voids at 1 gyration: v 1v 1denotes the percentage of voids calculated at one gyration (or C 1 the compacity atone gyration) in accordance with the equation model set forth in the EN 12697-10):v% = v 1- K1 ln ( ng )C = C K ln ngor ( )% + 1 10v 11 K 1 20200ngThe model is then adjusted with respect to a regression line for points (v, ln ( ng ) ) or(C, ln ( ng ) ) lying between 20 gyrations and 200 gyrations. V% is computed byconsidering that compaction using the Gyratory Compactor is linear as a function ofthe logarithm of the number of gyrations.The percentage of voids at 1 gyration also serves as a rutting resistance indicator (forthe same reasons as for v 10 ). The 20% threshold (AC-GB, AC-BBSG) seems toprovide a satisfactory estimation.3.5.6 Slope K 1The slope K 1in the model v% = v 1- K1 ln ( ng ) is sometimes referred to as the mixworkability indicator.Its value is more heavily correlated with the upper sieve size D of the mix. Shouldbitumen content vary over narrow ranges, K 1would stay constant for a given granularskeleton. On the other hand, K 1varies whenever the fines content varies.- 104 -
LPC Bituminous Mixtures Design Guide- Mix Design Procedure -Granular compacity does not vary any further for bitumen contentsabove 4%. An increase in bitumen content is equivalent to filling theinter-granular voids.For a binder content variation of δTL, compacity C 1 becomes C 2 , i.e.:C2≈ C ×1MVR× δTL× 1001( 100 +)(100 + TL ) x 1,03(The variation of maximum density (MVR) has been neglected herein.)3.5.7 Pseudo shear stress τThe pseudo shear stress τ is defined as the force necessary to straighten thespecimen submitted to gyratory compaction at a small internal angle (0,82°).F1× d1τ is defined by the following relationship: τ = ;h × SF 1 is the force necessary to maintain the Gyratory Compactorangle, expressed in Newtons;d 1 is the distance that force F 1 acts with respect to the specimenaxis, in millimeters;h is the specimen height, in millimeters; andS is the surface area of the specimen base.On the LPC gyratory compactors of types 1 and 2, τ ≅ 0,01 (in MPa).hThe evolution in τ has been tracked vs. percentage of voids v%. At the maximum τvalue, τ max , the value of v%(τ max ) corresponding with this maximum is obtained.1F 1ττ max% Voidsv % (τ max )- 105 -
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Table of ContentsPREFACE ..........
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3.4.4 Discontinuity ...............
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Table of illustrationsFigure 1: Gyr
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Table 40 - Adjustment to average te
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6. LPC Bituminous Mixtures Design Guide, Sept 2007. - Aapaq.org

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