Mariely Mejias-Santiago

Assessment of Warm-Mix Asphalt for Heavy Traffic Airfields

This paper presents the results of tests of warm-mix asphalt (WMA) mixtures designed for airfield pavements. The study was conducted in two phases. The first phase included laboratory tests on 11 WMA technologies. The tests in Phase 2 were performed on three WMA mixtures and one hot-mix asphalt (HMA) mixture produced in an asphalt plant. The evaluation included performance tests to assess WMA susceptibility to permanent deformation and moisture damage compared with that of HMA produced with the same aggregate blend. Test results indicated that WMA potentially was a viable product for surface mixtures on airfield pavements. Although WMA exhibited poorer performance than HMA in moisture damage tests on laboratory-produced specimens, the plant-produced mix indicated little difference compared with HMA. Rutting potential for WMA was somewhat greater than for HMA for mixtures produced both in the laboratory and in an asphalt plant according to asphalt pavement analyzer and Hamburg wheel tracking tests. Differences in performance of WMA mixtures were not attributed to a specific WMA technology category. Variations in performance test results between laboratory-produced specimens and plant-produced specimens were noted and indicated a need to require performance testing as part of a comprehensive quality assurance plan.

Accelerated Pavement Testing of Warm-Mix Asphalt for Heavy-Traffic Airfields

The results from accelerated pavement testing on warm-mix asphalt (WMA) mixtures designed for airfield pavements are presented. Three WMA mixtures and one hot-mix asphalt (HMA) mixture produced in an asphalt plant were evaluated under simulated heavy aircraft traffic. The evaluation was conducted at extreme traffic conditions, including heavy aircraft loading, high tire pressure, and high pavement temperature. Pavement structural response and rutting were evaluated to assess the susceptibility to permanent deformation of WMA mixtures compared with that of HMA produced with the same aggregate blend. Test results indicated that WMA was a viable product for surface mixtures on airfield pavements.

Development of Foam Backfill Repair Techniques for Airfield Pavement Repairs

Recent military operations have highlighted the need for new expedient pavement repair capabilities to improve current guidance on airfield damage repair. Damaged or distressed military airfield pavements must be repaired with expedient methods and durable materials to minimize the time the pavement is removed from service and to reduce or eliminate additional closure times for subsequent repairs. Extensive research was conducted to develop several airfield pavement repair techniques that could be applied across the full spectrum of military airfield repair operations. This paper focuses on the research conducted to develop a new foam backfill technology for airfield pavement repairs. Results of initial laboratory and field tests showed that rigid, poured polyurethane foam is the most applicable backfill solution for deployed locations because of its ability to expand to several times its shipped liquid volume when mixed, reducing the logistical burden of transporting aggregate backfill materials. This paper describes laboratory and field experiments that used foam backfill and prototype equipment to develop a pavement repair technique that supports threshold and objective aircraft pass levels defined for expedient airfield repairs. The research included laboratory testing, full-scale field testing, and simulated and actual aircraft traffic tests with C-17 and F-15 aircraft. Results of these tests validated and certified the foam backfill repair technique for military aircraft use. However, these experiments also identified material and equipment limitations that will require additional research before the repair technique is adopted by military repair teams. Conclusions and recommendations for future equipment and material improvements are provided.

Performance of Grooved Warm-Mix Asphalt Pavement Surfaces Under Heavy Aircraft Load and High Tire Pressure

This paper presents an evaluation of the performance of grooved warm-mix asphalt (WMA) under heavy aircraft loading compared with that of grooved hot-mix asphalt (HMA). Runway surface grooving is often required to provide high skid resistance for aircraft braking, particularly in wet conditions where hydroplaning must be minimized. An area of potential concern with the use of WMA on the surface of airfield runway pavements is the material response to surface grooving. If the asphalt binder in WMA is softer than that of comparable HMA because of reduced binder aging during production and placement, the WMA mixture may be more likely to experience groove closure or collapse. This condition could result in hydroplaning issues because of the reduction in water discharge and also in chipping of aggregate from the groove edges, which could increase the potential for foreign object damage. A full-scale experiment was designed to evaluate two pavement curing conditions and three WMA mixtures. Traffic was applied to the pavements with an F-15 load cart, and testing occurred during the summer of 2013. The performance of WMA, measured as the percentage of groove closure, was compared with that of comparative HMA. It was concluded that WMA could perform as well as HMA under different pavement curing conditions. This result indicates that WMA runway surface pavement that is properly cured before grooving should not exhibit groove closure under normal aircraft traffic conditions.

Asphalt Pavement Analyzer Sensitivity to Specimen Preparation Procedures and Testing Parameters

The Asphalt Pavement Analyzer (APA) is a laboratory accelerated pavement test device that has been used by many researchers and agencies as a tool to assess rutting potential of asphalt mixtures. Typically, the test is performed on cylindrical or beam specimens using a vertical load of 445 N, a hose inflation pressure of 690 kPa, and a test temperature equal to the high binder performance grade (PG) temperature. A simulated wheel load is repetitively applied to test specimens, typically for 8,000 cycles, and the rut depth is measured as a function of load cycles. This study evaluated the sensitivity of the APA to specimen preparation procedures (e.g., mixing, compaction, and volumetrics) and test parameters (e.g., temperature, wheel load, and hose pressure). Results from the study indicate several parameters can have an important impact on APA performance. These influences become important considerations when using the APA as a design or performance assessment tool.

Binder and Mixture Testing to Assess Rutting Performance of Warm Mix Asphalt (WMA)

Warm mix asphalt (WMA) technology is steadily gaining popularity due to the environmental, energy, and cost savings it offers as a sustainable alternative to conventional hot mix asphalt (HMA). However, adoption of WMA for commercial and military airfield pavements has been slow due to lack of documented good performance on airfields and concerns about potential rutting problems. This paper presents testing results for 11 WMA technologies, compared with traditional HMA. One unmodified base binder and one aggregate gradation were utilized throughout. Both laboratory full-scale plant-produced materials are tested. Binder performance grade (PG) data and Asphalt Pavement Analyzer (APA) mixture rutting data are presented. Relationships between laboratory and plant produced binder data and APA rutting are explored. The overall conclusion is that WMA is a viable alternative to HMA to improve the sustainability of airfield pavements.