When it comes to constructing roads and pavements, Hot Mix Asphalt (HMA) is an option known for its superior durability and flexibility.
However, to ensure that a mix meets the required standards, delivers optimal performance, and can last, certain testing and inspection processes are required. Here at G3 Quality, our certified inspectors have provided hot mix asphalt testing for pavement projects all around the golden state.
But what is hot mix asphalt, and what processes are used to test for quality and indicate future performance?
Learn what HMA is used for, how it’s tested in the field, and scroll to the bottom for an example of G3 Quality’s work in this area.
Hot Mix Asphalt, Defined
Hot mix asphalt, or HMA, is a broad industry term that refers to a mixture of aggregates, such as crushed stone, sand, and gravel, and bitumen (asphalt binder) – a sticky black substance derived from crude oil. The mixture is then heated at high temperatures to produce a workable material that can be placed and compacted during road construction.
Firms like G3 Quality test HMA in two ways: field and plant inspection and testing.
Types of Hot Mix Asphalt Testing
Inspectors and testers use both field and plant inspection and testing to analyze the quality of HMA. While the former is meant to monitor asphalt placement, the latter helps to ensure mixture performance and consistency.
Field Testing (Compaction & Control)
Field testing focuses on compaction control of asphalt during the construction process, and is a critical component of HMA quality control.
During this process, QA/QC professionals closely monitor asphalt placement from the moment it’s delivered in trucks, to its final compaction with rollers. Here at G3 Quality, we carefully observe the entire placement process, assessing factors such as the temperature of the asphalt, rolling patterns, and the behavior of the material as it’s being compacted. We measure the density of the compacted surface with a nuclear density gauge, which provides insights into whether compaction is up to standard.
With this comprehensive approach, firms like G3 Quality allow project owners to rest easy knowing that their materials are being placed and compacted appropriately. Plant control testing and inspection, on the other hand, takes place before the asphalt is transported to the job site.
Plant Testing & Inspection
Before asphalt is delivered to the construction site, plant testing and inspection are conducted to analyze HMA composition – the proportions of aggregates, asphalt binder, and additives.
The goal of plant testing is to verify that the correct mix design is followed, aggregate properties are within tolerances, equipment is certified, and that the asphalt binder is brought to the appropriate temperature for mixing.
“There are a number of considerations within the plant testing and inspection process. What’s in the mixture? Are the right proportions of aggregate, binder, and additives being used? Is asphalt being brought to the optimal temperature? Not enough rock, dust, or oil? All of these factors influence the subsequent field process.”
- Zachary Wheeler, G3 Quality Director of Operations
The process itself consists of analyzing individual components in the asphalt mixture, including moisture content, temperature, and the percentages of each material. This comprehensive assessment confirms that mixture components are accurately combined, making for an asphalt mixture that meets design specifications.
Plant testing is also designed to detect any potential issues that could impact the field process. Not having enough rock in a mixture, for example, or having too much dust or asphalt binder, can negate the quality of compacted surface. By identifying these concerns before the HMA reaches the job site, inspectors and testers can prevent potential issues or delays before they arise.
Hot Mix Asphalt Case Study
One recent HMA project that G3 Quality supported was the $127M San Francisco International Airport Airfield Improvement Program, a runway rehabilitation effort that was carried out from March to October 2021.
G3 Quality was under contract to perform on-site QC testing of soil subgrade materials, crushed aggregate base, cement treated base, and hot mix asphalt. Compaction testing was conducted using a nuclear density gauge to establish and monitor rolling patterns, provide feedback to paving crews, and document all measurements; while coring of the completed HMA pavement was performed to provide in-situ data, and core holes were backfilled with non-shrink grout to maintain pavement performance.
Reach Peak HMA Quality & Durability with G3
For any project involving pavement, hot mix asphalt testing is integral to ensuring that road surfaces meet both quality and durability standards. At G3 Quality, we’ve been delivering HMA field and plant inspection and testing services for years, serving a number of major projects all around California. If you have a pavement project in the works, don’t hesitate to contact California’s preferred QA/QC firm to ensure your materials are safe, long-lasting, and high-performing.
Fill out a form on our Contact page to keep your materials in line with project and safety requirements.