Did you know that the in-place air void content of the compacted asphalt pavement is in many ways the single most important factor that affects the overall performance of the asphalt mixture throughout the life of the pavement?
Compaction is the process used to reduce the volume of a mass of material. The goal of compacting a hot mix asphalt (HMA) pavement is to achieve the optimum air void content in-place and to provide a smooth, uniform surface.
There are many different activities that can influence the proper compaction of an asphalt mixture in the field such as the mixture design, production operations, placement operations, and environmental influences.
Achieving the Right Compaction
To properly achieve the required compaction, paving operations can utilize different types of rollers or combinations of rollers depending on the requirements. Typical self-propelled compaction rollers include: Static Steel-Wheel Rollers, Vibratory Rollers, and Pneumatic-Tire Rollers also known as Rubber-Tire Rollers. The compaction process is usually achieved in a sequence of roller operations known as breakdown rolling, intermediate rolling, and finish rolling. It is critical during these operations to monitor the pavement density with each roller pass to help establish the rolling pattern necessary to achieve the optimum density.
Since compaction reduces air voids (or increases density) in HMA, the area of concern is the in-place air voids of the compacted asphalt. The two most common ways to measure the in-place air voids of the pavement are core sampling and nuclear gauges.
The core sampling method is the most common form of sampling from a completed HMA pavement. Core sampling is often used as an acceptance tool by agencies and owners to verify the quality control density testing performed during the placement operations. Portable drills with wet-cut diamond-studded core barrels are used to cut through the pavement and obtain the sample. The core sample is then sent off to a lab for testing. The construction crew can have the test results as quickly as a few hours or more commonly a day or two depending on the testing procedures used to evaluate the density.
The most common quality control practice for monitoring in-place density and compaction is to use a Nuclear Gauge. The nuclear gauge process is less intrusive and measures the compacted HMA using gamma radiation. While this method is quicker and easier, the gauge must be properly correlated using core samples to the specific asphalt mixture being measured; otherwise, the reading will be inaccurate. The practice of establishing a correlation typically takes place during startup operations or a test strip prior to full production and construction.
Testing the Asphalt
We think of ourselves as a well-versed company; at G3 we offer many inspection and testing services, including hot mix asphalt inspection and testing, pavement coring, and compaction control. Our field services department is highly trained and provides testing services to some of the most intricate and complex cases. Our inspectors and technicians are Caltrans, ACI, CWI, AWS, and ICC certified professionals and will get the job done in a timely and professional manner – The G3 Way!
At G3 Quality, we are industry leaders who are always embracing change and excellence. We are an elite team of engineers and professionals who provide world-class quality management, pavement engineering, materials design, construction inspection, and testing on infrastructure projects throughout California and the Western United States.
To learn more about how G3 Quality can contribute knowledge, expertise, consulting, and professional services to your project, contact us.