Replacing Asphalt base and/or subbase course for asphalt repair

[LG3P]

I am working on an asphalt repair/replacement project where we need to replace about 19,000 SY of asphalt between airfield shoulders and non-heavy equipment parking. The asphalt shows moderate alligator cracks however the asphalt is not under heavy use and is at least 10 years old. I suspect that much of the cracking is from aging as the location is southern california where the temperatures in the summer reach above 95F regularly. I am wondering if full base and subbase course replacement is really necessary or if removal of the asphalt and scarifying and recompacting the base course would be enough. Any suggestions for repair options that I may not have thought about?

http://files.engineering.com/getfil...6-12dfcd14eeb1&file=Asphalt_repair_needed.pdf

 

[civilman72]

If you're going to replace that much asphalt, you really should spend some money on a geotech pavement design report, which will provide you recommendations including extent of base and subbase removal.

Have you thought about recycling/pulverizing the existing asphalt?

 

[Ron]

Agree with civilman72.....likely just the asphalt needs to be replaced if only weathered; however, those cracks have likely let water into the base and subgrade, so there might be compromise there. Assuming the shoulders need to withstand inadvertent traffic loading, you don't want a base failure if an aircraft rolls off the runway/taxiway onto the shoulder.

Recycling is good way to go on this.

 

[BigH]

Do some background studies on "top down cracking" of asphalt. Brittleness of the asphalt at the surface does end up in alligator cracking and it has nothing to do with the underlying base and subbase courses. Have you tried drilling cores to see how "deep" the cracks extend?

http://www.superpave.psu.edu/portal...etings/2004/03Drakos Energy Ratio NE 2004.pdf

http://www.civil.uminho.pt/transportinfra/publications/2003_(Mairepav3)_Freitas_Pereira_Picado.pdf

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w162.pdf

http://classes.engr.oregonstate.edu.../09_pavement_evaluation/top_down_cracking.htm

We had the issue with new pavement in India when straight asphalt was used as the binder - polyer modified behaved better.

 

[BigH]

Another - this time from a Brit perspective

http://www.transport-links.org/transport_links/filearea/publications/1_762_PA3738_2001.pdf

 

[EireChch]

It could be considered to remove the asphalt and undertake benkelem beam tests. This would indicate the deflection on the base course. If deflection is more that 2.5mm may require replacement or recompaction maybe incorporating a geodrid.

I agree with the above comments though more geotech may be required. Clegg testing could also be inconjustion with benkelem beam testing. This would be substantially cheaper and could be used as supplementary test data for assessment