Air Void Study

5 days ago by
Discussion about the best way to come to the target air voids of the cored asphalt specimen.
File attached: Air Void 3 Part Study-Example.pdf (86.11 KB)

According to AASHTO PP-60 you determine a target gyratory specimen mass from the following equation:

$Mass=\left(\frac{100-\left(Va_t+F\right)}{100}\right)\cdot G_{mm}\cdot176.7147\cdot H$Mass=(100(Vat+F)100 )·Gmm·176.7147·H


Mass = estimated mass of mixture to prepare a test specimen to the target air voids
Vat = target air void of the cored test specimen, % by volume
Gmm = maximum specific gravity of the mixture
H = height of the gyratory specimen, cm
F = air void adjustment factor: 1 for fine-graded; 1.5 for coarse-graded

PP-60 suggests the cyclical trial and correction method but you can also use a 3 part study method.

You can use the above equation to calculate the mass required to achieve your target air voids.  
Then calculate the mass for gyratory specimens that have 2% higher and 4% higher target air voids. 
Fabricate all three gyratory specimens at the same time. 
You then core the gyratory specimens and determine the cored specimen air voids. 
Plot the gyratory specimen mass to resultant air voids and add a linear trend line (line of best fit) to the data. 
The equation of this line will enable you to select the correct mass to achieve your target specimen air voids and will also enable you to fabricate to different air void targets without further trial and error gyratory specimen fabrication.
written 5 days ago by Casey Nash  

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