Roadway Base Rock Sizing

[martin888888]

Anyone have any thoughts on using 1 1/4"-0 base rock under ashphalt instead of 3/4"-0? Both compact very well. I have seen 1 1/4" used often but always with a 2" leveling course which I really dont think is needed.

 

[oldestguy]

The subject of what kind of base course to use always brings forth a lot of different ideas. One factor that should be considered in most areas is the possibility of the subgrade soil intruding and "contaminating" the base course. Another is the possible migration of fines up out of joints or cracks under the effect of traffic and wet conditions.
Another is the shear strength of the mixture, affecting load transfer down to the subgrade. Of course we could go on as with soundness and frost heave effects, etc.

Be prepared for several different viewpoints.

 

[Ron]

One of the more important items is the thickness of the base. Make sure the base thickness is about 3 or 4 times the thickness of the larger material. If uniformly graded to fine material from there, compaction and stability are improved.

 

[civilman72]

There is also the issue with blading the larger material, developing a consistent crown and matching survey bluetops: 3/4" is easier to work with.