The SPS-10 experiment, “Warm Mix Asphalt Overlay of Asphalt Pavement Study,” aims to compare the performance of warm mix asphalt (WMA) to that of hot mix asphalt (HMA), both in the short and long term. The study expects to reduce the current knowledge gap between the performance of WMA and HMA, which is partially attributable to the lack of documentation of long term performance. The majority of the industry is adopting WMA technology, but there is no real grasp of its long term impact. This study will aid in determining that impact and how WMA can be used to save money and improve road life and performance. Currently, WMA has numerous benefits including increased haul distances and time to work with the mix versus HMA. WMA can also be used as a compaction aid and is more environmentally friendly than HMA.
Researching Pavement Performance
The SPS-10 experiment is designed to explore how a set of primary factors affect pavement performance. These factors include: the type of WMA technology used, the climatic elements of temperature and moisture, and the traffic loading. SPS-10 projects overlay existing asphalt pavement, and consist of 500 foot test sections with different overlay properties. Each project is required to have three core sections: HMA control, WMA produced using foaming process, and WMA created using a chemical additive. For the purpose of these studies, WMA is defined as asphalt pavement produced at 30°F below standard HMA production temperatures or below 275°F.
In addition to the core sections, the corresponding state department of transportation (DOT) and Canadian provinces may choose to include supplemental core sections in order to perform additional research relative to their own network. For example, the state or province may choose to study the effects of increased recycled asphalt pavement (RAP) content, decreased overlay thickness, or other WMA production methods. All materials testing and performance monitoring related to the supplement sections will be performed by the LTPP team at no additional cost to the state or province.
Fugro and LTPP Working Together
The first SPS-10 project was constructed in the fall of 2014 along westbound Interstate 40 in central New Mexico, near Santa Rosa in Guadalupe County. The project included the three core sections as well as two supplemental sections selected by the New Mexico DOT (NMDOT). Fugro and the Southern Region Support Contractor (SRSC) for LTPP evaluated the condition of the pavement before and after construction, and Fugro will continue to monitor the condition of the pavement many years to come. Additionally, through careful coordination with NMDOT, Fugro documented all construction activities, sampled materials during construction, and collected cores after construction. Fugro engineers and LTPP State Coordinators Thomas Burchett and Tahmid Rahman were responsible for coordinating with NMDOT staff as well as with the construction contractor Fisher Industries in completing the placement of the WMA core sections.
As the existing Southern Region Support Contractor for the FHWA LTPP Program, Fugro has been involved with state coordination, data collection, data processing, analysis, and quality control (QC) during the evolution of this program over 27 years. The goal of the LTPP program is to increase pavement life by investigating various designs of new and rehabilitated pavement structures, using different materials and under different loads, environments, subgrade soil, and maintenance practices. This will significantly improve the design and management of the nation’s pavements, which will ultimately require improved capabilities for predicting pavement performance.
James Sassin, LTPP’s Southern Region Project Manager, stated, “Fugro Roadware eagerly welcomed the opportunity to assist FHWA in the SPS-10 experiment and to learn more about the long term performance of warm mix asphalt pavements compared to traditional hot mix asphalt.”