Search the forums

Loading

compacting gravel /crushed rock fill

oops's picture

compacting gravel /crushed rock fill (post #201476)

When compacting soil, you do it in 6" lifts. What about compacting washed gravel or crushed rock? I was told that # 57 gravel is self compacting.  I find this hard to believe. I want to be dang sure. 

What do you do?  What has been your experience. Anyone here have the answer. Thanks

The situation is filling a 3' wide x 7' deep ditch that will have concrete paving over it.

I don't think you can compact (post #201476, reply #1 of 3)

I don't think you can compact gravel.  I've always heard that you can make sure it's settled all the way with a viratory compactor.  But not something like a jumping jack.

I don't think you can compact (post #201476, reply #2 of 3)

I don't think you can compact gravel.  I've always heard that you can make sure it's settled all the way with a viratory compactor.  But not something like a jumping jack.

Probably self compacting (post #201476, reply #3 of 3)

#57, which is 1/2 to 3/4-inch gravel is generally considered to be self compacting.  This is because there are no fines to inerfer with the movement, so it goes to where there is direct contact between the particles.  Short of braking the rocks, which would require a great deal of force, the material won't get any tighter. 

Generally granular, as opposed to rounded, materials are prefered if you are using it for backfill, because the interlocking of the material on the edges makes it slightly more stable. 

So, you put it in, hit it with a concrete vibrator, and it will settle as much as it will in human time frames. 

A word of caution however:  If you have fine grained materials adjacent to it, the fines may migrate into the voids, causing settelement of the adjacent areas.  This is worse if there is mositure that can carry the fine material into the voids.  And worse if there is less clay in the trench walls.  Typically the excavation should be lined with geotextile felt to prevent migration of the fines.