Washed crushed recycled concrete

[sgwpe1]

Hi: We have designed a porous asphalt pavement parking lot with 3-ft +/- thick stone reservoir beneath. We have had several constructed projects constructed with clean No. 2 virgin stone aggregate and they have worked and held up well. We have had a contractor propose to use recycled concrete as the aggregate for the stone reservoir on this current project. The first bucketful he showed us had a lot of fines and cement adhered to the material and we rejected that for use and said he should try washing it. He brought in washed samples which look a lot better but still have some concrete dust and a few fines. Our concern is that any fines could migrate down and clog the infiltration surface; especially since concrete fines could reactivate and bond to each other, soil and geosynthetic fabric. Does anyone have experience with this or similar use of recycled concrete that you could share? Thanks, Scott

 

[Ron]

Crushed concrete has fines and unhydrated cement particles. Your concerns are reasonable. It will require multiple washings.

 

[chicopee]

My experience with recycled concrete from bridge demolitions is that when we used it as fill on the company owner's properties, it would turn rock hard solid after a few years when we tried to excavate to install water lines.

 

[dicksewerrat]

Ron has it right. City of Mpls used crushed concrte for street base. A little water and vibratory roller on 8-12 inches of crushed, then add 2-3 inches of asphalt and you are good to go. The crushed has a lot of free cemnt particles that will hydrate and bind up the base very well. Not a good plan for a dry well.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[dik]

We've used recycled concrete for road bases numerous times... our experience is excellent, but as noted, we would not use it as a drainage medium because it tends to reconstitute itself back into a cementitious mass...

Dik

 

[sgwpe1]

Thanks, all. Scott