How to Ensure Quality Control in Asphalt Supply for Your Projects

Much distress on asphalt pavement, including environmental cracking, rutting, and early life raveling, can be traced to poor construction and lack of QC/QA efforts. Fortunately, several best practices that are relatively easy to implement on each project can significantly improve quality and reduce those distresses. From ensuring that you are using the best equipment (you can check out Roller hire rates for a cost breakdown) to mixing high quality materials for optimum construction, all of it comes together for a brilliant result.

Additionally, in-place density measurements are essential for QC/QA of materials and construction. They can be obtained via nuclear and new non-nuclear density gauges, cores, and intelligent compaction (IC) equipment.

Trial Batches

For road construction, a thorough testing and inspection process must be implemented to ensure that the materials used for the project are of the highest quality asphalt supply near me. For asphalt, that means a variety of tests must be done to assess the material’s strength, stability, and density.

Testing and inspection at the plant level ensure that the HMA meets specifications before being transported to the construction site. A trial batch, a limited plant run before total production starts, can help make necessary changes to get the HMA in spec before paving work begins. Since the primary QA factors for asphalt paving are temperature and compaction, regular checks of those two processes must be made by QC personnel.

In addition to those in-field tests, a lab-molded density sample can give QC a picture of the mixture’s properties. Sensor-based inline viscosity measurements can also be added to the mix design process, allowing closed control loops that automatically correct any production deviation.

Tests

Asphalt is a mixture of aggregates (crushed stone, sand, and gravel) and bitumen (asphalt binder) heated to high temperatures during road construction. Firms conduct field and plant inspection and testing to analyze asphalt mixtures and ensure consistency.

Testing for asphalt includes:

• Obtaining moisture from aggregate stockpiles.
• Collecting cores of the finished mat.
• Performing nuclear density tests.
• Measuring critical sieve size gradation and moisture content.
• Monitoring plant performance.

Some agencies have moved away from “method” specifications to “end-result” specifications, which define the level of asphalt quality desired rather than describe how the construction should be done.

Control charts make it easy to see trends and identify plant or mix issues. For example, if the binder content data points are consistently below target, the plant operator should be notified. Other tests include rolling thin film ovens, pressure aging vessels, viscometers, dynamic shear rheometers, and ductility testers to assess the short-term and long-term aging of the asphalt binder.

Spreadsheets

Building pavements takes a lot of taxpayer dollars, and you deserve to know that your contractor is paying attention to QA/QC. While some distress, like environmental cracking and oxidation of surface layers, come from other causes, others, such as delamination between layers, potholes early in the life of a pavement, and shoving that results in poor compaction, are often caused by improper mix design, production, and placement.

The Asphalt Tank Screen shows several values that must be entered for each day’s asphalt binder usage. Beginning Time: Enter the time of the last tank stick reading taken before the plant started production that day.

Tank Capacity: Enter the total capacity of the tank. Outage Stick Reading: (or Direct Reading) If your contractor is using a direct reading tank stick, do not make an entry here. Pounds per Gallon: Enter the net weight printed on the certified truck tickets that accompanied each load of asphalt binder delivered to the tank during the day.

Materials

Asphalt concrete mixtures must be carefully monitored from the plant to the construction site to ensure they are of high quality. Hot mix asphalt (HMA) is a mixture of bitumen, a sticky black material derived from crude oil, aggregates like crushed stone, sand, and gravel. Firms perform HMA testing and inspection in two ways: field monitoring of paving operations and plant control testing.

Plant control tests verify that the specified mix design is used, that equipment is operating correctly, and that the aggregates meet graduation requirements. These tests also help confirm that the HMA is mixed to the proper temperature for consistent quality.

During the paving process, compaction specifications are verified using nuclear or new non-nuclear density gauges and cores of the as-built pavement. These measurements are necessary to ensure that the HMA is compacted to the required spec to provide a pavement with good long-term performance. However, these measures are often influenced by environmental conditions such as ambient temperatures and roller speed, which can cause over- or undercompaction of the pavement.