However, their void contents may be too low. Usually, deviations from 

 these curves will result in lower densities and higher VMA. The extent of 

 change in density and VMA depends on the amount of adjustment in fine or 

 coarse aggregate. Figure 39 illustrates a series of Fuller maximum density 

 curves plotted on a conventional semilog grading chart. 



Figure 40 illustrates maximum density curves determined from the maximum 

 density equation raised to the 0.45 power {p = 100 (d/D)* if5 } and plotted on 

 the Federal Highway Administration grading chart (based on a scale raising 

 sieve openings to the 0.45 power), which many designers find convenient to 

 use for adjusting aggregate gradings. The curves on this chart, however, 

 need not be determined from the maximum density equation. They may be 

 obtained by drawing a straight line from the origin at the lower left of the 

 chart to the desired nominal maximum particle size at the top. For processed 

 aggregate, the nominal maximum particle size is the largest sieve size 

 listed in the applicable specification upon which any material is permitted 

 to be retained. Gradings that closely approach this straight line usually 

 must be adjusted away from it within acceptable limits to increase the VMA 

 values. This allows enough asphalt to be used to obtain maximum durability 

 without the mixture flushing. 





FEDERAL HIGHWAY ADMINISTRATION 0.45 POWER GRADATION CHART 







SIEVE SIZES RAISEO TO 045 POWER 













1 



L , 



i ; 



1 / 



1 / 



/ 



/ 







90 

 80 

 TO 



60 

 50 

 40 

 50 





















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- 





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 1 



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ol 







}///, 





I 



1 



1 



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 1 









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10 



no. a 



c 







on 







40 



c 



i 







1 



10 



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6 



1 



3, 



SIEVE SIZ 



ES 



2* 



♦„. 



N 1 





 IW 



Figure 40. Maximum density curves on Federal Highway 

 Administration 0.45 power gradation chart 

 (Federal Highway Administration, 1975) . 



172 



