Although members of the public assess a paving job based on subjective factors such as smoothness and appearance, professionals know that pavement quality is based primarily on asphalt density. They do so because even minute improvements to density result in ten-fold increases in durability. In the past, a construction partner making a density evaluation had no choice but to test small samples and then extrapolate findings to the entire project. Today, however, modern construction technology allows for more thorough quality checks of larger areas. Here are two of the newer devices we now use to create denser pavement.
Nuclear Density Compaction Gauges
No one sees the aggregate material poured on native soil, but the quality of the sub-base is just as important as what goes on top. Cutting corners here may result in a support structure lacking in integrity or durability, causing pockets of the finished product eventually to crumble. In the past, there was no good way to test the sub-base other than to trust contractors to make periodic visual inspections.
Nuclear density compaction testing is the modern method of assuring that the strongest possible foundation supports a paved area. This method consists of using an on-site gauge containing radioactive materials to conduct a series of 1-minute tests of the sub-base’s water content. Technicians divide the results by the maximum theoretical compaction value of the material to obtain a percent value of density. Workers can then fix or re-pour any areas that score less than 99%.
Paver-Mounted Profiling Units
The temperature of asphalt is another variable that negatively affects density when lowered too quickly or spread unevenly throughout the mat. The following are three types of temperature readings that workers should monitor:
- Asphalt mixture: Workers should strive to apply the mixture at 275-300 degrees Fahrenheit, the same temperature at which they originally receive asphalt shipments.
- Air: Warmer days are more suitable for paving projects, with sub-optimal conditions occurring below 50 degrees Fahrenheit and on days with strong winds.
- Ground: The ground to be paved should also have a temperature over 50 degrees.
Thermometers are a low-tech method that construction workers have traditionally used to monitor the temperature. However, it is impossible to conduct enough measurements to guarantee uniform conditions over the course of the project. Paver-mounted profiling units are a superior technology that companies have been using during the past decade. These devices identify uneven mat temperatures by creating visual thermal profiles. The goal is to obtain differences in mat temperature of less than 25 degrees, with discrepancies of 50 degrees or more risking unacceptably negative effects on density.
The Pavement Network Buyer’s Alliance
The members of PNBA are professionals who pool their talents and resources for the good of everyone in the pavement field. By partnering with preferred vendors, we obtain the most competitive prices. We understand the importance of asphalt density and are keenly aware of the benefits of improved technology used to evaluate it and other parameters of construction quality. For more information about what we do or to become a member or vendor, contact us today.