Aggregate Base Density Data 1

[mo76]

Hello All,

I am converting (CY) of aggregate (for a road construction project) to (TONS). Does any one have scientific data to use for the density of aggregate base rock?

Several sources state that "most natural" aggregates have particle densities between 150 and 181 (lb/ft^3). In the Civil Engineering Reference Manual (CERM), under chapter 48, "Properties of Concrete and Reinforcing Steel" Pg. 48-2, "Aggregate" states that, "Most sand and rock aggregate has a specific weight of approximately 165 (lb/ft^3).

A common practice of industry professionals is to divide TONS by (2) to get CY. Dividing TONS by (2) to get CY assumes that the in place aggregate will have a density of 148 lb/ft^3. However, a differential of a couple of units (148 vs 165) makes a big difference in cost on big projects. Therefore I thought that somebody must have a more scientific approach to deal with this issue.

The (150-180) density data comes from a "Design and Control of Concrete Mixtures" book and appears to refer to the "particle" density of aggregate. However, since the aggregate is made up of particles, it is reasonable that the compacted density of the aggregate is between (150-180 lb/ft^3).

If you consider an entire road bed compacted at 95%, would it be reasonable to estimate that the density of the aggregate road bed is 165 (lb/ft^3) as stated in the CERM under aggregate properties section?

 

[mo76]

REVISED POST...
(Revision two the second to last paragraph in the above post)

I am converting (CY) of aggregate (for a road construction project) to (TONS). Does any one have scientific data to use for the density of aggregate base rock?

Several sources state that "most natural" aggregates have particle densities between 150 and 181 (lb/ft^3). In the Civil Engineering Reference Manual (CERM), under chapter 48, "Properties of Concrete and Reinforcing Steel" Pg. 48-2, "Aggregate" states that, "Most sand and rock aggregate has a specific weight of approximately 165 (lb/ft^3).

A common practice of industry professionals is to divide TONS by (2) to get CY. Dividing TONS by (2) to get CY assumes that the in place aggregate will have a density of 148 lb/ft^3. However, a differential of a couple of units (148 vs 165) makes a big difference in cost on big projects. Therefore I thought that somebody must have a more scientific approach to deal with this issue.

Data from the "Design and Control of Concrete Mixtures" book, states that the particle density of aggregate is between 150 and 180 (lb/ft^3). This data refers to the "particle" density of aggregate. However, since aggregate is made up of particles, it is reasonable that the compacted density of the aggregate is between (150-180 lb/ft^3).

If you consider an entire road bed compacted at 95%, would it be reasonable to estimate that the density of the aggregate road bed is 165 (lb/ft^3) as stated in the CERM under aggregate properties section?

 

[JedClampett]

You need to talk to someone with experience in doing this calculation. For example, the weight of poured in place concrete, with reinforcement, is only 150 lb/ft^3. There is no way that compacted base weighs more than that. You're going way off on a tangent using some inappropriate information and extrapolating it to fit.
I'm guessing compacted AB weighs no more than 120 pcf. But you need to touch base with someone who has local experience.

 

[BigH]

JedClampett - sorry, but we have compacted crushed stone coming in at over 150pcf. Why? Our specific gravity is 3.0. I agree with you. M076 can look in tables of swell/shrink on variouis materials from bank to in truck to in place. I have a chart but how to put it on here?

 

[bltseattle]

Here in Washington the state DOT provides guidance for engineer's to prepare their estimates that includes unit densities for different materials, as placed. I would think most states have something similar for use on highway projects, so you should check with your state DOT if you haven't already done so.

FYI,
It is Figure 520-1 in the Washington State DOT Design Manual, for reference. This table has in-truck and placed densities. SO a crushed gravel is about 1.43 T/cy in the truck and 1.85 T/cy placed, typ. They note that placed density varies from 1.7 to 1.9 T/cy, with the lower end of the range for materials with say 40% sand and the upper end for more open-graded ballast.

 

[GeoPaveTraffic]

It depends on the gradation of the rock and the compative effort being put into the rock. In the Midwest for a material with some fines, the maximum modified Proctor desity is typically 135 to 140 pcf. If the compaction requirement is 95 percent, the final inplace density would be 128 to 133 pcf. Then of course there is waste...

 

[cvg]

this is standard information that can be obtained from your geotech, your highway department, your local material supplier or your favorite contractor. but it varies from locale to locale and you will have to ask somebody local.

 

[Dirtmaster]

I my region (the Atlanta, GA area), most of the granite quarried has a density of around 150 pounds per cubic
foot (pcf)

Most pavers use 110 pounds per square yard per inch of thickness (or 146.67 pounds pcf) for estimating graded aggregate base. This seems to work well.

Talk to your local quarry sales department. They should
be able to give you densities for your region. Our quarries
publish tables indicating compacted densities of all their
products.

Go to

http://www.vulcanmaterials.com/

Select construction materials, product calculator
construction aggregates, geology, product (select the product)Estimate density.

 

[tmctim]

I agree, call the local quarries and contractors for your best guess.
My many years estimating on the contractor's side give me confidence using a factor of about 150 lbs/cu ft (or about 2.03 tons per cubic yard) -- this is higher than a soil engineer will tell you (that is, a this same aggregate soil lab compaction at 100% proctor may be about 128-130 pcf dry density; and 138-145 pcf wet density).
The difference: when buying rock from a quarry, there always is water (including some for evaporation) that you wind up paying for (at the right moisture content, this is a good thing, it is much better to have the proper moisture in the material before it is shipped, because the cost to add water and mix by the grader at the jobsite is higher than paying for some extra water).