How do you calculate the density of hot mix (asphalt) just as it is loaded on trucks and before compaction.?
Answer:
The density of the mix cannot be determined based solely on the aggregates and bitumen, because some of the bitumen will be absorbed. You need to take density measurements of the loose mix, as produced.
Don't bother with using sand to figure your volume.
Asphalt is usually discussed in terms of specific gravity, not density. Specific gravity is density/(the unit weight of water).
Cut cores, then weigh them 1)dry, 2)saturated - surface dry(SSD), and 3)while suspended in water(submerged weight).
The bulk specific gravity, also known ad little d, is equal to (Dry weight)/(SSD weight - submerged weight).
Basically, the SSD weight minus the submerged weight is equal to the weight of water displaced by the core, or the volume of the core times the unit weight of water.
So, (dry weight of core)/(volume of core)x(unit weight of water) = density/unit weight of water.
You would calculate the maximum specific gravity, also known as big D similarly. Instead of testing the core, you would test the loose mix.
Specifics for the tests can be found at the links below.
The in-place mix should be compacted to 93% to 96% of the maximum specific gravity.
I am used to working with mix placed by a paver, but loose mix behind the paver is usually expected to compact approximately 1/4" per inch of thickness. If you are trying to place a 2" compacted lift, you should place approximately 2 1/2" of mix behind the paver, before compaction.
Hi,
I am sure you know the density equation.
The method is After filling the hot mix, go to the nearest weigh bridge and weigh the truck with the hot mix, so that the mix wont become cold or if you have heating system in the truck all the better. After pouring the mix out, weigh the empty truck. Density of hot mix before compaction can easily be calculated, d1 = (Wt. of filled truck - Wt. of empty truck)/filled volume of truck's container
After ccompaction, take a flat piece of Compacted and cold asphalt. the size of your palm. Put it in a container and pack well the empty space with dry sand up to the top of the container. Remove the contents and put the sand alone back.into the container. The depth of sand by Area gives the volume of sand. Total container volume - Volume of sand = Volume of compacted asphalt.
Find the weight and divide by the volume to get bulk density of compacted asphalt (d2). To get the % compaction is given by 100*(d2 -d1)/d1
Good luck
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