Marshall Value for Binder

[SCGeo]

I am currently involved in the paving portion of a large commercial project. The Marshall Value for the binder that has been forwarded to me by the asphalt lab is 168.7 lb/cf. This seems incredibly high to me, as the highest dry value I have ever measured was around 150. I have requested the mix design, but I'm still curious as to whether any of you have encountered values this high.

 

[BigH]

It does seem high - we have values of 2.65 g/cc here but our specific gravity of the coarse aggregate approaches 3 (2.95 to 3.05). This is the only way I can see how your Marshall Density is so high. Or, perhaps, they have given you not the Marshall Density but the Rice Density (maximum theoretical density) - usually taken as 104% Marshall = 100% Rice.

 

[Ron]

SCGeo...I agree with BigH...awfully high. Even if your Rice value is high, I wouldn't expect that much.

In your area (assuming "SC" means the Palmetto state), coarse aggregate specific gravities will vary from a low of about 2.45 to a high of about 2.70.

One thing you might look out for is that someone is using steel slag as coarse aggregate in the asphalt (you have a producer in Georgetown). Steel slag has a highly variable specific gravity. Not a good idea because of the instability and potential destructive expansion of steel slag, but it has been done and the mistake often repeats itself every 10 years or so!

Get the mix design. I can't imagine a producer having a mix design with a density that high....tough to get compaction if its wrong!