Foundation Design for 10'D Asphalt Tank

[nwitt]

Our typical foundation design for small asphalt (or other elevated temp. products) is simply a raised concrete slab with a sheet of asphalt impregnated fiberboard between the slab and the tank bottom. On a recent project, on of the other engineers in our office designed in (4) radially spaced 1 1/2"W x 1/2"D grooves in the pad. These grooves were sloped from the center of the pad to the edge supposedly to help remove moisture from below the tank (or actually from below the fiberboard). Has anyone ever seen a design like this? His feeling was that the hot product would create "sweat" below the tank bottom, keep the fiberboard moist, and eventually corrode the tank bottom. I've always assumed the fiberboard would keep moisture out and therefore thought the grooves weren't necessary.

 

[kslee1000]

Is there known case of such corrosion? Does the pad still meet the strength requirements after adding the grooves? If so, I see no harm, but small increase in concrete consumption. Maybe you shall let him try and watch if the result agrees with his thought.

 

[gerrytt]

Please refer to API 650

 

[aeoliantexan]

It's my understanding that moisture tends to migrate from warm areas to cold ones. Ths is true in soils as well as in insulation systems. I would not expect that moisture migration to the tank foundation would be a problem.

 

[civilperson]

"Sweat" is condensation which will only occur at temperatures less than the dew point. Hot asphalt will negate any condensation possibility for the tank and the ambient temperature for the foundation might cause occasional moisture but no problems.