Does anyone have any experience in thermal imaging of asphalt roads as a part of an ongoing preventative maintenance program? I am interested in the capabilities from your experience. We can all see surface cracks and pot holes, could you pick up unseen faults? Things such as
- could you pick up voids under the asphalt
- could you see water erosion under the asphalt
and anything else you can offer

Oh, most important, what lessons have you learnt along the way.

thanks for your time

Mick Windsor
www.windsorbusinesssolutions.com.au

Is it worth doing? If for inspection during construction, maybe more usefull.

Hi Josh,
It is certainly worth doing during construction as you can see any temperature differences during the pour which can cause issues

There has been some work done on existing roads and there are papers on the web. That is part of the reason why I ask the question as I would like to hear of people's experience's using thermal imaging on existing roads. Was it feasible and cost effective. I do see thermo as only one tool in the kit for this purpose though.

could you pick up voids under the asphalt, YES
could you see water erosion under the asphalt, YES

I have not done this myself, but have like you read published papers, I have also spoken to the authours of such papers. This is a very difficult application, and only possible under transient conditions. I suggest training to at least level 2 before trying this.

www.thermalvision.ie

Thanks Bob,
what type of conditions are required to be able to pick up the voids and water erosion?

The success will depend on the size and depth of the void, and the amount of water present. I would suggest looking at it in traisient after sunset. Try looking at known voids first, before jumping straight in. You may need a small span, and the level set correctly, but theoretically this is possible.

Hi Bob,
what do you mean by looking at it under transient conditions?

cheers
Mick Windsor
www.windsorbusinesssolutions.com.au

A good deal of work was done on this application in the 1980s by Gary Weil (St. Louis area) and published in the Proceedings of Thermosense. Gary used scanning systems, image averaging and some software processing that he developed. He could routinely find objects buried under roadways prior to repaving. He got his start on finding underground voids in brick sewer systems which would cave in after water infiltrated. I've lost touch with him over the years but he may well still be at it.

Transient conditions occur when the ground is changing temperature (or is in thermal transition) such as happens on a clear evening after a sunny day. The ground and the anomalies cool at different rates and, with planning and some luck, you can be there at the right time to see them.