Bubling in road base compacted. 3

[ts54]

Gents,

Here, there are an interesting issue. We are building a asphalt road in the Chilean desert and the compacted material that formed the base where we will make a doble treatement asphalt road, has begin to formed bubling in the surface. Really we keep all specification according with AASHTO ( granulometric, sales content, fines materials content, etc). Someone said that perhaps the water inside the soil when by evaporation it is raising to top of carpet,dragging to its step fine particles of the filling material. Now we can't apply the asphalt until discover the problems, any idea it is appreciated.

Best regards

ts54

 

[VAD]

I think "someone" has the correct answer. If you have observed "blisters" on asphalt pavement during rolling caused by hest and excess water from the drums on a very hot mat, the same can be conceived for the base re the heat and perhaps some excess moisture. This should disappear and allow you to proceed with your double surface treatment. You may have to recompact the surface of the base before applying your asphalt treatment. Observation and a few shallow probes in the base should allow you to make proper decisions.

 

[BigH]

VAD is probably right (as per usual) in the need to observe. Is the bubbling more like sponginess? If so, we have discussed this in a number of other threads on compaction - my take is that you may have had your base course too wet - as your vibration is done, the water comes to the surface and brings fine silty particles with it. But, with the evaporation, the fine silty particles are left forming a thin but low permeability "dusting" on the surface. As more compaction is given, the water wants to rise but the low permeability of the intial passes' residual silt prevent the water from escaping - hence you get sponginess and some cracking under wheel loads. Try to ensure that your base course material is a percent of so under the optimum moisture content. See how that works.