HMA Production Facilities: Training for the Move to QC/QA

Kent Hansen / December 28, 2000

The nature and level of responsibility of individuals involved in the production and placement of hot-mix asphalt (HMA) is changing with the implementation of quality control/quality assurance (QC/QA).

Agencies are no longer prescribing mix components and placement procedures, and are relying more and more on contractors’ own quality control data. This would not be possible without the emergence of strong partnerships between agencies and contractors, with all partners working together to construct better HMA pavements.

To help meet this challenge, a new training course, “HMA Production Facilities,” has been developed by the National Asphalt Pavement Association (NAPA) under the auspices of the Joint AASHTO/FHWA/Industry Training Committee on Asphalt. The course is designed to teach participants how HMA plants operate and how the operation of these facilities affects the quality of the mix.

The National Highway Institute (NHI) offers both “HMA Production Facilities” and another course, “HMA Construction,” which was developed by NAPA in a similar process a few years ago. More than 6,000 individuals have already graduated from “HMA Construction.”

The NHI attempts to ensure that participants in each session of both courses be an equal blend of agency and contractor personnel. This helps improve the partnership necessary for QC/QA and improves the learning experience.

Partnering for success

When everyone involved in the production of HMA understands how HMA facilities operate, they can work as a team to avoid and solve problems. There are many questions that need to be answered when producing HMA:

•Do the materials—aggregates and asphalt—meet the specified requirements?

•Are the aggregates properly stockpiled to avoid segregation and mingling of materials?

•Are the aggregates properly removed from the stockpile to avoid segregation and wet material at the bottom of the pile?

•Is the aggregate feed system properly calibrated and operating within an acceptable range?

•Is the weigh bridge calibrated and operating correctly?

•Is the burner operating at top efficiency? Are there any air leaks?

•Are aggregates being dried completely? Is there proper veiling of material?

•Are screen decks in batch plants in good condition?

•Are asphalt meters calibrated and operating correctly?

•Are there any points of material transfer that may cause segregation?

•Are surge storage silos being operated to avoid segregation?

•Are trucks being loaded to avoid segregation?

•Are proper sampling and testing procedures being followed?

•Does the final product meet the owner’s requirements?

These are only some of the questions that must be answered daily. Normally, the answer to all questions is a simple “yes.” When there is a problem, though, finding the solution can require looking at many facets of the operation.

The course provides participants with the tools to answer these questions and solve the problem as a team.

Common elements

Some of the key elements common to both batch and drum plants discussed in the course are aggregate stockpiling, aggregate feed systems, dryers, asphalt metering, emission control equipment, and surge storage equipment. Elements specific to batch or drum plants are discussed in separate sections.

A section on quality control/quality assurance discusses elements of a quality control plan. It is anticipated that the section on QC/QA may be revised to meet the requirements of individual agencies. Included throughout the course are Q and E (quality and efficiency) tips.

Improving the skills of the work force is a never-ceasing challenge. “HMA Production Facilities” will aid in the transition to QC/QA and help in production of improved hot-mix asphalt.

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