Structural Number for recycled in-place asphalt
Structural Number for recycled in-place asphalt
(OP)
Does anyone know the ASSHTO SN for crushed in-place asphalt?
I'm rehabilitating an existing parking lot in good shape, minor surface cracks only, by crushing 2" of existing pavement. 5" to 6" of existing agg. base will remain in place untouched, and overlaying with 2" of new HMA. Any thoughts on using just one layer in overlaying the existing crushed material?
Thanks.
I'm rehabilitating an existing parking lot in good shape, minor surface cracks only, by crushing 2" of existing pavement. 5" to 6" of existing agg. base will remain in place untouched, and overlaying with 2" of new HMA. Any thoughts on using just one layer in overlaying the existing crushed material?
Thanks.





RE: Structural Number for recycled in-place asphalt
RE: Structural Number for recycled in-place asphalt
You stand the chance of developing structural cracks in your new pavement since you may want to pave before the recycled crushed aggregate has been conditioned. However, if your loads are just cars then this may not occur.
Regarding the layer coefficient a value of around .14 is used for virgin crushed stone. This is still debatable. I would think that a somewhat smaller value would be appropriate for the recycled material. You should check Yyoder and Witckak pavement Design text to confirm the value suggested.
Dicksewerrat's question leads perhaps to provideing a layer coefficient value depending on the state of the material. The SN is obtained by multiplying the layer coefficient by the thickness of layer.
Good Luck
RE: Structural Number for recycled in-place asphalt
If you are just going to pulverize the existing asphalt and leave in place as a layer on top of the base, don't waste your time or money. That's an accident waiting to happen!
RE: Structural Number for recycled in-place asphalt
RE: Structural Number for recycled in-place asphalt
As far as a layer coefficient, we usually use 110% to 130% of the layer coefficient for the virgin stone base beneath the in-place asphalt. Where I hail from, the stone base # is 0.18 for crushed aggregate base, so we use 0.20 to 0.24 for the CPR mixture, depending on the size and quality of the asphalt stone as well as the amount of new stone added to the blend.
RE: Structural Number for recycled in-place asphalt
If there are minor cracks, would it not be cheaper to perform some maintenance on the existing structure and extend it's life rather than removal of the existing and then overlaying with a new lift of ACP?
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