Forum Message



Name: Ken  Day
Heading: 1.1.1.1.1.1RE:Percent Voids in Aggregate
Message:
IS anyone using a specific ASTM or AASHTO test for measuring the voids in coarse aggregates?

We are beginning to see an upswing in requests for the %voids for pervious stone base applications.


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Brian Glackin


Brain,

ASTM C 29, Vol. 4.02 is what you should be using for percent voids in coarse aggregate.
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Karthik Obla


Thanks Karthik for the quick reply.

Our QC manager and I had been devised a quick %voids test based on steps from other AASHTO tests but he could not find a specific test. I will pass this on to him.
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Brian Glackin


Brian,
You mentioned that you have developed a quick method to determine % voids. If you don't mind could you briefly explain it? We are currently looking at buying a fairly expensive piece of equipment (Instrotek Corelok System)to measure % voids and if your method is easy and accurate, we might reconsider our purchase.

John Cherne
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John Cherne


If I recall correctly, we did the following.

weighed up a dry 1/2 cuft pail (empty) on the scale

Filled the pail with coarse aggregate (jigged the pail several times as we filled it to consolidate the stone)

The top of the pail was struck and eyeballed so that no aggregate pieces were completely above the lip of the pail. We allowed them to protrude past the lip but used the 50% rule meaning for every piece above the lip, there was a corresponding "hole".

We then weighed up the bucket

Finally with the bucket on the scale, we poured water in slowly (to avoid trapping air) until the water created a flat surface across the lip of the pail.

Record all weights and repeat 2 more times with fresh aggregate to ensure a good average.

From this, we obtained a "jigged density" to approximate the rodded density of the aggregate.

Also, I compared this density against the density I have for the rock mass (170 lbs/cuft in my case) and came up with a theoretical voids (1-jigged/rockmass)

We then took the weight of the water and divided it by 31.2 lbs (half of 62.4 lbs per cuft) and got the voids based upon the volume of water.

We ignored the absorption loss to the stone since this was a quick and dirty test.

The theoretical and the water values were within several percent so we were satifisied for the time.

Timewise, I think it took an our to beat out the method and less than 10 minutes to do the test 3 times.


Off to get a ton of other work done, I hoped this helped. It got us a quick answer and the contractor was satisfied with waat we gave him since he did not specify how to determine the voids.

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Brian Glackin


Why the water? If you know (or determine) the SG of the rock and get its bulk density (weight per cubic foot, loose poured, rodded, or vibrated, as appropriate to your use) then you have the % voids by simple maths. Also why HALF of 62.4?
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Ken Day
 
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