Caltrans Pipe Bedding Sand

[DirtDelight]

Working on a job where the spec for bedding is a max of 5% passing 200 sieve and 90-100% passing a no.4 sieve. We brought a fill sand to the job and the lab came back with 12% passing the no 200 sieve. Does this seem right for
" fill sand ". If so, does anyone have a suggestion of a sand type that will meet those gradation requirements ? A washed sand maybe? Any help would be appreciated.

BG

 

[dgillette]

The low fines requirement may reflect a need for very high permeability, or at least I can't think of any other reason for it. Is it someplace where there needs to be a capillary breaker, like where it's frequently below 0 degrees F and you don't want heave from ice lenses?

ASTM C33 concrete sand will meet the spec and it's readily available, but it will co$t you.

Regards,
DRG

 

[trout211]

Like DRG said, we had a need for drainage around the pipe and didn't want sand at all, just standard pea gravel. Is there an upper limit to the gradation?

 

[cvg]

while pea gravel will provide excellent drainage capacity, it does allow finer soil to "pipe" into the trench bedding. This could cause voids in the trench walls ultimately causing trench subsidence and requiring the street to be repaved. If your native soils are fine, this may be the concern. concrete sand generally will not allow the piping to occur while still providing good drainage capacity.

My typical experience in California (years ago) was to require sand bedding material with a sand equivalent of 30 according to CalTrans test method 217. I'm not sure if your fill sand would meet this spec or not.

 

[DirtDelight]

Thanks to all who responded. The upper limit to the gradation is the 90-100% passing the 4. Project management figured out how to deal with the issue. They had all the material dug out and started over.