Asphalt Structural Number

[ghiadunedin]

We are replaceing a cracked 5" thick portland concrete driveway that is used by our fire department, i would like to replace it with full depth asphalt(because of the short cure time) on exist subbase of compacted sandy soil, i don't have a soil test, but the area has no problems with drainage and is in Florida so freezing isn't an issue. I've looked at AASHTO and i don't have some of the necessary numbers to calculate SN is there some simple way to calculate full depth asphalt thickness to support (fire engine)/semi truck weights with approx.10-20 trips a day? Thank you for any advice.

 

[jdonville]

See

http://training.ce.washington.edu/WSDOT/Modules/06_structural_design/06-3_body.htm

For the 1993 design equation.

Getting the W18's should be straightforward - take the fully loaded vehicle weight and divide by 18000 lbs. Follow the links on the page to get estimated numbers for some of the other terms. You will end up with a relation between asphalt thickness and stone thickness. We generally like to keep the ratio of asphalt to stone near 1/2.

Post back with the terms you are having difficulty with.

Jeff

 

[1Kat1]

A 3" total thickness would suffice the weight. Typically a 1" binder course is laid. Then you would put your 2" wearing course. In your case with the wieght of the trucks, a 2" binder would be more appropiate.

 

[namdac]

Ihave to ask how can 3" Asphalt be sufficent for a WB-18. With the temperatures in florida won't it rut, due to the weight of let's say a pumper?
Regards,
Namdac

 

[1Kat1]

Go to the link below and it will have a explanation, and pointers on load limits, and HMA's (Hot Mix Asphalt). It does also state that monitoring the asphalt placement is a good idea, to ensure the asphalt supplier is within the guidelines of the particular client's needs.

http://www.asphaltalliance.com/upload/Concept Paper_974913343_112006174257.pdf