Crushed Concrete Used as Soil Stabilization?

[samond]

Has any one had experience with crushed concrete being used for soil stabilization? The contractor is hogging out soupy muck from an 8' wide sanitary sewer trench. We are requiring the contractor to place 6-12" rock and apply pressure until the rock cannot go any deeper (so far it has been about 2'). The contractor asked if they could use recycled concrete. I have not heard of recycled concrete being used for stabilization.
I like the idea of using recycled material but I am concerned that when pressure is applied to push the recycled concrete into the muck it will crumble and we will not have the size rock we were wanting. Furthermore, should I be concerned about the admixtures in the concrete, fly ash, calcined clay, silica fume, etc?
Thank you for your opinions.

 

[Ron]

samond...crushed, recycled concrete would be excellent for this application. It is a robust base material for pavements and for stabilizing. I would not hesitate to use it in your application.

 

[racookpe1978]

The concrete chips should be "rough" or coarsely crushed, right? Not with "smooth" corners or tumbled or polished. Same size as the gravel or rock you'd otherwise specify.

If rebar is left in the chunks, it needs to be short sections only.

 

[dicksewerrat]

Recycled/crushed concrete also has some free cement particles that will set up if exposed to water. I saw this when using crushed concretr as road base.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[DougHole]

i have seen crushed concrete use for under slab fill and it has worked fine. only problem is writing a compaction spec for it but it sounds like you might not need to worry about this. i would be concerned about contamination issues though. recommend getting it tested to make sure it doesn't exceed your local contamination thresholds. good luck

Doug Hole
Junior Geotechnical Engineer

 

[Okiryu]

That material is very good for soil stabilization, however here in Japan we have to check that the material does not leach hexavalent chromium. This is also done for soil-cement treatment for soil improvements.