1. Home
  2. TRID
  3. View Record
https://www.nationalacademies.org/trb/events

Level II Hot Mix Asphalt, 2011

In simplest terms, hot mix asphalt (HMA) is nothing more than a combination of rocks and asphalt. The rock provides the skeleton and the asphalt provides the glue or “muscles” to hold the skeleton together. The skeleton must carry the weight while the muscles must be strong enough to hold the skeleton in place but still be flexible. Over the last one hundred years, engineers and technicians have observed that certain combinations of rocks and asphalt work well while others do not. Those who purchase HMA have taken those observations and turned them into specifications or requirements that the HMA is expected to meet. Today, the producer of HMA must be able to prove that he will deliver a product that meets the requirements for the job. That proof is often called the “Job Mix Formula” (JMF) or “Mix Design”. The JMF is the proportions of the aggregates to be used and the amount of asphalt to add. These proportions are established by testing various combinations in the laboratory until one is found that meets all the requirements. On the surface, this sounds simple, until one considers how many combinations of various aggregates are possible and how many requirements must be met. Not all jobs have the same requirements and more than one aggregate is usually needed. Over the years the requirements have become more stringent and more numerous, while the number of high quality aggregate sources have dwindled. Of course, the most important requirement from the HMA producer’s point of view is to make money while supplying a product that meets the purchaser’s needs. The JMF can have a significant effect on the costs associated with the production of the HMA. The mix designer, therefore, can affect the HMA producer’s bottom line. This places the mix designer in a difficult position, where costs must be minimized but a certain level of quality must be maintained. Add to this the fact that most JMF’s require some adjustment during plant production in order to maintain the required quality, and the complexity of the mix designer’s job becomes obvious. The purpose of this training course is to help the student sort through these complexities and learn how to balance conflicting expectations while designing a mixture that will produce a durable pavement.

Language

  • English

Media Info

  • Media Type: Print
  • Edition: Technical Training and Certification Program
  • Features: Photos; Tables;
  • Pagination: 530p

Subject/Index Terms

Filing Info

  • Accession Number: 01345773
  • Record Type: Publication
  • Files: TRIS, STATEDOT
  • Created Date: Jul 28 2011 2:22PM