For many agencies, paving season is already underway while for others it has to wait until the beginning of the fiscal year. Either way, asphalt paving is even more stressful this year as a result of oil prices and that means that being a good consumer is more important than ever. There are many elements of paving that can set the path for a long service life, but tack is one that is too often comprised, so it is worth checking your job specs to ensure that you are requiring the contractor to apply tack and then ensuring through inspection that they do apply it and they do so correctly.
We talked a bit more in-depth about tack in our April 2021 e-newsletter and from there referred you to some resources to learn more, so we won’t repeat ourselves here. That is, except to say that tack represents approximately one percent of the cost of a pavement job, and yet some contractors still seek shortcuts, some owners fail to adequately specify tack in their contracts, and some inspectors are unwilling to hold the contractor to the requirements of the job. In all instances, the public suffers because their tax dollars purchase a less durable pavement.
Some local agencies fail to mention tack at all in their request for proposals, so that is a bad place to start. Ideally, any such request should have specifications about mix design, milling, surface preparation, compaction, utility relocations, and the whole ball of wax, but at least some passing reference to tack is a must or you will have no ability to enforce it. We can help you develop that language if you get stuck, so just reach out to our engineering circuit rider.
Remember, tack is an emulsion (a mix of water and oil, just like they always told us was impossible), which enables a uniform distribution of asphaltic binder to the surface once the mixture “breaks.” So, we just need to get the contractor to place the emulsion uniformly and in sufficient quantity to bond the pavement layers and then just wait a bit until it breaks. If the surface preparation was done well, we are on our way to a long lasting pavement job. Without tack, we’ve compromised the job almost before it got started. Without proper application of tack, you have to ask yourself at some point why you’re bothering.
Seriously, aside from maybe the brooming of the surface, it’s the cheapest part of the paving job, so make sure you specify it and insist on it being applied correctly.
Don’t forget, the PPRA Resource Center is worth a little time to better understand tack, because so many pavements projects could benefit from better tack application. The Delaware T2/LTAP Center’s Municipal Engineering Circuit Rider is intended to provide technical assistance and training to local agencies, so if you have pavement management questions or other transportation issues, contact Matt Carter at matheu@udel.edu or (302) 831-7236.
You must be logged in to post a comment.