Warm Mix Asphalt (WMA) is a new technology that was introduced in Europe in 1995. WMA offers several advantages over conventional asphalt concrete mixtures, including: reduced energy consumption, reduced emissions, improved or more uniform binder coating of aggregate which should reduce mix surface aging, and extended construction season in temperate climates. Three WMA techniques, Aspha-min, Sasobit, and Evotherm, were used to reduce the viscosity of the asphalt binder at certain temperatures and to dry and fully coat the aggregates at a lower production temperature than conventional hot mix asphalt. The reduction in mixing and compaction temperatures of asphalt mixtures leads to a reduction in both fuel consumption and emissions. This research project had two major components, the outdoor field study on SR541 in Guernsey County and the indoor study in the Accelerated Pavement Load Facility (APLF). Each study included the application of four types of asphalt surface layer, including standard hot mix asphalt as a control and three warm mixes: Evotherm, Aspha-min, and Sasobit. The outdoor study began with testing of the preexisting pavement and subgrade, the results of which indicated that while the pavement and subgrade were not uniform, there were no significant problems or variations that would be expected to lead to differences in performance of the planned test sections. During construction, the outdoor study included collection of emissions samples at the plant and on the construction site as well as thermal readings from the site. Afterwards, the outdoor study included the periodic collection and laboratory analysis of core samples and visual inspections of the road. Roughness (IRI) measurements were made shortly after construction and after a year of service. The indoor study involved the construction of four lanes of perpetual pavement, each topped with one of the test mixes. The lanes were further divided into northern and southern halves, with the northern halves having a full 16 in (40 cm) perpetual pavement, and with the southern halves with thicknesses decreasing in one in (2.5 cm) increments by reducing the intermediate layer. The dense graded aggregate base was increased to compensate for the change in pavement thickness. The southern half of each lane was instrumented to measure temperature, subgrade pressure, deflection relative to top of subgrade and to a point 5 ft (1.5 m) down, and longitudinal and transverse strains at the base of the fatigue resistance layer (FRL). The APLF had the temperature set to 40°F (4.4°C), 70°F (21.1°C), and 104°F (40°C), in that order. At each temperature, rolling wheel loads of 6000 lb (26.7 kN), 9000 lb (40 kN), and 12,000 lb (53.4 kN) were applied at lateral shifts of 3 in (76 mm), 1 in (25 mm), -4 in ( -102 mm), and -9 in ( - 229 mm) and the response measured. Then each plane was subjected to 10,000 passes of the rolling wheel load of 9000 lb (40 kN) at about 5 mph (8 km/h). Profiles were measured after 100, 300, 1000, 3000, and 10,000 passes with a profilometer to assess consolidation of each surface. After the 10,000 passes of the rolling wheel load were completed, a second set of measurements was made under rolling wheel loads of 6000 lb (26.7 kN), 9000 lb (40 kN), and 12,000 lb (53.4 kN) at the same lateral shifts as before. Additionally, the response of the pavement instrumentation was recorded during drops of a Falling Weight Deflectometer (FWD).

Warm Mix Asphalt (WMA) is a new technology which was introduced in 1995 in Europe. WMA is gaining attention all over the world because it offers several advantages over conventional asphalt concrete mixes. The benefits include: (1) Reduced energy consumption in asphalt mixture production process; (2) Reduced emissions, fumes, and undesirable odors; (3) More uniform coating of aggregate with binder, which should reduce surface aging; and (4) Extended construction season in temperate climates. WMA requires the use of additives to reduce the temperature of production and compaction of asphalt mixtures. WMA technologies include: -Aspha-min, the addition of sodium aluminum silicate or zeolite to the asphalt mix.-Sasobit, the addition of a paraffin-wax compound extracted from coal gasification.-Evotherm, the addition of an emulsion to improve the coating and workability of WMA mixes.

TRB's National Cooperative Highway Research Program (NCHRP) Report 691: Mix Design Practices for Warm-Mix Asphalt explores a mix design method tailored to the unique material properties of warm mix asphalt technologies. Warm mix asphalt (WMA) refers to asphalt concrete mixtures that are produced at temperatures approximately 50°F (28°C) or more cooler than typically used in the production of hot mix asphalt (HMA). The goal of WMA is to produce mixtures with similar strength, durability, and performance characteristics as HMA using substantially reduced production temperatures. There are important environmental and health benefits associated with reduced production temperatures including lower greenhouse gas emissions, lower fuel consumption, and reduced exposure of workers to asphalt fumes. Lower production temperatures can also potentially improve pavement performance by reducing binder aging, providing added time for mixture compaction, and allowing improved compaction during cold weather paving. Appendices to NCHRP Report 691 include the following. Appendices A, B, and D are included in the printed and PDF version of the report. Appendices C and E are available only online.

Sustainability is a cornerstone of today0́9s engineering world. Warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) are the most prominent sustainable materials in asphalt concrete pavements. WMA is a not a new concept, however new innovations and increased usage of WMA has been spurred by the increased focus on sustainable infrastructure systems. WMA enables reduced production temperatures through the use of wax, water, or other chemical packages. The effects of reduced production temperatures include fuel use and emissions reductions, improved compaction, and possible RAP concentration increases. RAP is the primary recycled product of the aged asphalt concrete pavements and its use leads to reductions in virgin aggregate and asphalt demand. However, significant performance issues can stem from the individual integration of WMA or RAP materials in asphalt concrete. In particular, WMA technologies can increase moisture and rutting susceptibility while RAP significantly increases the stiffness of the resulting mixture. Consequently, quality performance of sustainable asphalt pavements may require the combined use of WMA and RAP to produce mixtures with sufficient stiffness and moisture and fracture resistance. This study evaluates the potential of WMA technologies and their integration with RAP. Initially, an extensive literature review was completed to understand the advantages, disadvantages, and past field and lab performance of WMA and RAP mixtures. Rotational viscometer and bending beam rheometer tests were then used to evaluate Sasobit, Evotherm M1, and Advera WMA modified and unmodified binders. Finally, virgin and 45% RAP mixtures were designed and tested to examine the rutting, moisture, and fracture resistance of WMA and HMA mixtures. The results of this experiment provided several key observations. First, viscosity reductions may not be the primary cause for the availability of reduced production temperatures for WMA technologies. Second, WMA additive properties have a significant effect upon fracture, moisture, and rutting resistance. Furthermore, the addition of RAP to WMA mixtures improved the rutting and moisture sensitivity performance as characterized in the Hamburg and Tensile Strength Ratio testing procedures.

"TRB's National Cooperative Highway Research Program (NCHRP) Report 763: Evaluation of the Moisture Susceptibility of WMA Technologies presents proposed guidelines for identifying potential moisture susceptibility in warm mix asphalt (WMA). The report also suggests potential revisions to the Appendix to AASHTO R 35, "Special Mixture Design Considerations and Methods for WMA" as a means to implement the guidelines."--publisher's description