Prime Coat Calculations for IDOT

(Article Updated 8/10/24)

Several years ago, the Illinois Department of Transportation (IDOT) changed the way it measures & pays for bituminous prime coat. What used to be a simple computation became complicated (just like everything in construction anymore….). The specification requirements were expanded, increasing the degree of surface prep, cleaning & application parameters than with former specifications. IDOT made the change in response to research that has shown the expanded role that prime/tack coats play in the longevity of HMA overlays.

The 2022 IDOT Standard Specifications for Road & Bridge Construction includes Article 406.05 – Preparing, Prime Coat for Aggregate Bases, and Tack Coat or Full Lane Sealant. In years past, IDOT used to pay for the total quantity of emulsion applied (in either gallons or pounds of emulsion). In the current provisions, IDOT now pays for the residual asphalt (or the actual quantity of bitumen). To derive the quantity, the engineer must determine and subtract ALL water (both dilution water AND water in the emulsion) from the volume of material shipped & applied.

When IDOT first modified the calculation method, I sat down and built a spreadsheet that allowed me to enter all of the material and application area data to develop the payment quantities. As I am updating this article in August, 2024, I’ve had to make some adjustments to the initial spreadsheet:

-Modified the Jobsite Information block to only calculate the “Weight of Residual AC Applied” and deleted the “Weight of Emulsion Applied” row

-Updated the “Specified Application Rate” data to correctly correspond to the current Article 406.05 nomenclature

The hard part of maintaining a website is keeping the content evergreen. As requirements in our industry are always changing, it requires our tools to respectively change. That’s one of the reasons I’m hesitant about posting spreadsheets and calculations as I don’t want to have outdated information posted….

With the current set of updates, I believe that I’ve got the sheet running correctly. But, I’m always looking for input from those who have read this article and developed calculation methods on your own. If you see anything in this worksheet that looks incorrect, please reach back to me in the comments. I want to keep the tools I have sharp.

If you are interested in getting a copy of this worksheet and trying/testing it out for yourself, send me an email link in the COMMENTS below and I’ll try to help you out.

44 Comments

  1. Looks like a great work sheet. Appreciate that you are willing to share it. BTW, your blogs have been very interesting. Great job!

  2. Bob, I am a young Resident Engineer and was referred to your blog from a past manager. I have found the material to be extremely well written and a valuable resource to me. I would really appreciate a copy of this worksheet for it would be a great tool for me in the field. Thank you and I look forward to the blogs to come!

  3. Bob– this is Pat Kielty. I jsut finished DOC course last week and saw Tim Hussey there. Can you sent me a link or copy of your spreadsheet.

  4. Hey, Bob!

    I work in documentation and I would LOVE a copy of your spreadsheet to share with my construction guys and to help me get through this pay item in their reviews.

  5. Hello, Robert. If you could send me a copy of your prime worksheet, I’d appreciate it. Thanks.

  6. Hello Bob,
    You done a great job on the worksheet. Please send me a copy of your worksheet, this will help me out so much. Thank you

  7. Hello Bob,
    You done a good job on creating the worksheet. Please send me a copy of the worksheet. Thank you

  8. Hey Bob, could you send me the spreadsheet? BTW great blog. Its been a great resource for me.

  9. Hey Bob, just stumbled upon your blog, and must say you provide a lot of gems.
    Hope it’s not too late to get a copy of your tack coat spreadsheet. Thank you for sharing.

  10. Thank you for doing this. Could you email me a link to the spreadsheet when time allows?

  11. Could you please email me the link to calculate the tack coat. This will help me final my IDOT project. This is really helpful and thank you for sharing this to us.

  12. Would really appreciate a copy of the worksheet! Your website is awesome, so much great information! Thank you!!

  13. Hi,

    I liked your spreadsheet. I was wondering if you could send a copy(The post age). Also, I love your website.

  14. New to IDOT work, and a copy of your spreadsheet would be very helpful. Thanks for all the great content you post!

  15. I’ve only ever seen tack and prime coats paid per unit area applied (I.e. surface area of new asphalt). I’m curious to know why IDOT uses this measure for payment? Is there a QC check built into this method? Thanks!

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