Reuse existing base and subbase course

[Okiryu]

We have a site with an existing parking lot. New construction will be done and we will have the new parking lot in the same area of the existing one. The existing parking lot was installed about 30 years ago. As result of the new grading, we will need to cut and fill in the area of the parking lot. I took samples of the base course and it’s properties are fine so I am planning to keep it in place and cut and fill new base as required (by the way, we are doing the pavement design). My first concern was about if the existing base and subbase are properly compacted. However, the existing parking lot does not show evidence of pavement failure so I am assuming that the base and subbase courses were properly compacted.

Do you have any input or any comments about this approach? Do you think that it will be better to remove the entire existing base and subbase and replace them with new material? Perhaps, some sand cone tests to validate the compaction may be needed? Any feedback will be appreciated. Thanks!

 

[Ron]

Okiryu... re-use the base material. It can be tilled to full depth using a reclaimer machine. At that point you can re-grade and supplement with material prior to recompaction.

If the base material is sufficiently competent, scarify, supplement and recompact.

 

[Okiryu]

Thanks Ron. Yes, I will plan to reuse the existing material, scarify and recompact. The project has budget issues so any savings will help.

 

[Okiryu]

Ron, also, can you send me a link for reclaimer machines? I am looking at Google for them but not sure if that is the equipment you are recommending...Thanks again !

 

[oldestguy]

As to compaction level existing, that should not be an issue. What do you plan to do where the existing material thickness is OK and then you plan to cut some? So you end up with insufficient base thickness later. That can lead to a real mess, by removing and saving what you can, dig down removing enough subgrade and then filling with base. Tracking all that removed stuff out over OK base then means scraping off the contaminated base, etc. You had better have a qualified person on site all the time to stake out the fix-up locations, etc. Sometimes these sort of schemes sound OK, but it might be better to forget the saving idea and go with possibly more new base, etc. and do it right. I'd not fool around with any two layer system with base and sub-base either for a parking lot. That would mean salvaging all you can first, do the subgrade grading and then do the job right reusing the old and quite likely adding some.

 

[Okiryu]

OG, thanks for the advise.

We are thinking in this approach: for fill areas, I think that we can just scarify, recompact and supplement. For cut areas, to keep it simple, remove the entire existing base and replace it with new base/subabse. The removed base can be reused as new base as long as it is not contaminated with the subgrade soils.