Field Performance of Warm Mix Asphalt Technologies (2014) / Chapter Skim
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Engineering Properties and Field Performance of Warm Mix Asphalt Technologies P A R T 1
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3 Recent surveys show that the use of warm mix asphalt (WMA) continues to expand in the United States because of its environmental benefits, energy savings, and construction advantages.
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4in differences in pavement performance relative to HMA. Reduced oxidation of the binder may improve the cracking resistance of a pavement but may reduce its moisture and rutting resistance.
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5 • Measuring plant stack emissions of duplicate production runs at three projects consisting of three HMA controls and eight WMA mixtures. • Collecting worker exposures to respirable fumes over complete production days during two multi-technology projects consisting of two HMA controls and six WMA mixes.
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6greenhouse gases are consistent with reductions in fuel usage. Use of WMA should receive credit for reductions in greenhouse gases in life-cycle assessments.
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7 The test sections were built on a stiff subgrade and a gradedaggregate base commonly used at the test track. The cross sections for each of the test sections consisted of a 3-in.
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8rest of this section are based on FWD tests conducted in the right wheelpath with the 9-kip load. The pavement layer moduli were backcalculated from deflection data using EVERCALC 5.0 for a three-layer cross section consisting of asphalt concrete, aggregate base, and subgrade soil.
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9 follow an exponential function; the regression constants and correlation coefficients are shown in the figure. A statistical analysis found that the regression coefficients of the WMA sections were not statistically different from the control.
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10 steady, and texture changes were typical for the first 2 years of dense-graded surface mixes. Pavement moduli backcalculated from FWD testing throughout the research period are shown in Figure 1.5.
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11 The WMA technology vendors provided on-site guidance regarding modifications to the asphalt plant to accommodate the WMA additives. Advera and Evotherm DAT were introduced to the mix through pipes installed below and into the asphalt binder supply line, respectively, while the Sasobit was pre-blended with the asphalt binder in a tank before mix production.
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12 criterion was met. None of the sections showed any indication of moisture damage on completion of testing.
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13 HMA bottom layer. Below the HMA was an aggregate base approximately 40 cm thick.
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14 Figure 1.9. Phase 3 HVS Group 1 rutting performance.
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15 but it stiffened with time. Tensile strength ratio (TSR)
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16 Introduction Plans for field and laboratory experiments were developed to meet the objectives of this study. The field experiment was developed to gather information to assess short-term pavement performance of new and existing warm mix asphalt (WMA)
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17 Asphalt Foaming Processes Advera®. Advera is a synthetic zeolite composed of aluminosilicates and alkalimetals that contains approximately 20% water of crystallization that is released by increasing the temperature above the boiling point of water.
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18 contractor. The system foams asphalt outside of the rotating drum and then injects the foamed asphalt into the drum's mixing chamber (10)
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19 • Fuel Usage/Energy Audit. A comprehensive energy audit was conducted for multiple technology projects in conjunction with stack emissions testing.
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20 other cases, the data were obtained from the agency's online records. Two-way average annual daily truck traffic was calculated for each project from these data.
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21 The MEPDG only accepts creep compliance and strength test data conducted at -4°F, 14°F, and 32°F. The samples from Rapid River were tested at lower temperatures because of the project's PG 52-34 binder.
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22 binders were then long-term aged using the PAV before testing for intermediate temperature DSR and low temperature characteristics using the BBR. Table 1.12 shows a summary of the binder tests, output, and criteria.
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23 necessary fatigue data. The complete theoretical background of this method can be found elsewhere (18)
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24 projects selected for mix verification. One goal of the mix verifications was to determine if plant production of WMA could be simulated in the laboratory.
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25 mixed for the 90 seconds specified in the Draft Appendix to AASHTO R 35. If the mixture produced a degree of coating that failed the specification compared to the field result, a longer mixing time would be tried.
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26 The existing and new projects are discussed in the chronological order of their construction. Existing Projects St.
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27 specimens were compacted to 100 gyrations at temperatures equal to the compaction temperature behind the paver as shown in Table 1.18. Figure 1.14 shows the air void contents for the samples compacted both hot and reheated.
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28 Mix Sample Day Lab Compaction Temperature (°F) SGC Volumetrics Hot at Plant Reheated at NCAT Control 1 300 X X 1 250 X X Sasobit 2 250 X X 2 250 X X 3 225 X X 3 225 X X Evotherm ET 4 250 X X 4 250 X X 5 225 X X 5 200 X X Aspha-min 6 250 X SGC: Superpave gyratory compactor Table 1.18.
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29 Figure 1.15. Locations of test sections in St.
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30 PG for the HMA was substantially higher than for the WMA sections, possibly due to the increased aging associated with the higher construction temperatures. Table 1.24 shows the average densities and tensile strengths by location for the 5-year cores.
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31 pave design compacted to 86 gyrations. The aggregate used in the mix design was basalt, and a PG 58-34 virgin binder was used as the base binder for both mixes.
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32 thousand tons of WMA mix were produced. Mixing temperatures for the control HMA and the WMA were 325°F and 260°F, respectively.
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33 contained cracking, whereas two of the WMA sections had cracking. The number of cracks was fairly low, however, and all cracking was of low severity.
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34 Core Testing At the time of the 5-year project inspection, seven 6-in.
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35 portion of I-70 is at a high elevation and has a very harsh winter climate. The project began at the town of Silverthorne at milepost (MP)
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36 stockpile percentages. Table 1.34 shows the mix design for the control mix.
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37 Construction Paving was performed at night because of high traffic volumes during the day. Distance to the paving sites from the plant varied from 5 miles to 15 miles, which corresponded to a 10-minute to 25-minute haul time.
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38 Three-Year (38-Month) Project Inspection A field-performance evaluation was conducted in October 2010 after 38 months of traffic applied to the roadway.
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39 Sand patch tests were conducted at the beginning and end of each evaluation section between the wheelpaths. The sand patch test was also performed on the cores taken during the 3-year inspection.
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40 Property HMA Advera Sasobit Evotherm Sieve Size % Passing 19.0 mm (3/4")
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41 and four WMA -- were produced out of three different nearby plants. One of the HMA mixes, the Advera mix, and the Sasobit mix were produced at the LoJac plant in Franklin.
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42 produced at a target production temperature of 230°F. All three Franklin mixes contained the antistripping agent AD-Here 77-00 at a rate of 0.3% by weight of asphalt.
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43 Set Statistic HMA 1 Advera Sasobit HMA 2 Evotherm DAT Astec DBG Set #1 Average 92.1 89.0 90.3 93.0 90.4 87.0 Standard Deviation 1.4 1.2 1.6 1.4 1.1 1.1 Set #2 Average -- 93.0 92.2 -- 91.2 91.9 Standard Deviation -- 0.6 0.5 -- 2.4 0.6 Table 1.48. In-place density results (% of Gmm)
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44 cracking by crack type. The Sasobit and Advera sections showed the most cracking, and the Evotherm was the only section to exhibit fatigue cracking.
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45 Figure 1.27. Fatigue cracking in Evotherm section in Franklin, Tennessee.
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46 The material transfer device transferred the mixes into a 2005 RoadTec 190 paver. Figure 1.32 shows the material transfer device and paver used for both trial mixtures.
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47 Figure 1.29. Portable asphalt plant used for Graham, Texas, project.
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48 Figure 1.32. Material transfer device and paver used for Graham, Texas, project.
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49 Figure 1.34. Transverse cracks on the Graham, Texas, project after 30 months.
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50 also called for 20% RAP. However, in the state of Washington, RAP is not used in the design process.
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51 Property JMF HMA Sasobit Tolerance Limit Sieve Size % Passing 19.0 mm (3/4")
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52 requirement. This yields 6.3% and 1.8% failing the density requirements for the HMA and WMA respectively.
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53 tion. The cores were first tested for density according to AASHTO T 166, then tested for tensile strength using ASTM D6931, and then combined and the cut faces were removed.
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54 However, the difference is very small and can be attributed to sampling and material variability. New Projects Walla Walla, Washington A WMA field evaluation was placed on US-12 in Walla Walla, Washington, in April 2010.
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55 shown in Figure 1.40, uses a foaming gun (enlarged for detail on the right side of the figure) to create the foam.
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56 The haul distance from the plant to the roadway was less than 5 miles, so little production stoppage occurred from lack of trucks during the day. The delivery temperature of the WMA ranged between 244°F and 259°F, whereas that of the HMA ranged between 272°F and 295°F.
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57 and HMA. From this analysis, the WMA and HMA mixtures had similar cooling rates.
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58 138 steel wheel roller. A different breakdown roller was used for the HMA because the roller used on the WMA section was mistakenly transported to another site.
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59 inspections, no cracking was evident in either the HMA or WMA sections. The surface textures of both the HMA and WMA test sections were measured using the sand patch test according to ASTM E965.
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60 cut faces were removed. This mix was split into two samples that were used to determine the maximum specific gravity according to AASHTO T 209.
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61 then tested according to ASTM D6931. It was observed that the peak failure loads for both the 4-in.
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62 Figure 1.52 compares the predicted longitudinal cracking for US-12 over the design life. Although the MEPDG predicts slightly more cracking for the WMA compared to the HMA -- 61.7 ft/mi versus 34.8 ft/mi (11.7 m/km versus 6.6 m/km)
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63 used for mix design submittal and production are shown in Table 1.80. The asphalt mixture used a polymer-modified PG 76-22 asphalt binder supplied by Nustar in Baltimore, Maryland.
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64 WMA would have slightly higher mix moisture content for two reasons. First, the addition of 2% water by weight of virgin binder for the foaming process is approximately equal to about 0.1% of the total mix, and the WMA had about a 0.1% higher mix moisture content.
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65 The temperature of the mix behind the paver was measured using both a hand-held temperature gun and the PAVE-IR™ system manufactured by the MOBA Corporation. The PAVE-IR system consists of 12 infrared sensors that measure and record pavement temperatures across the mat and display on a mounted monitor.
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66 mitigate thermal segregation if it becomes apparent. The PAVE-IR system is shown in Figure 1.58.
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67 Construction Core Testing After construction, seven 6-in.
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68 Core Testing At the time of each project inspection, seven 6-in.
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69 the wheelpath as compared to the cores between the wheelpaths; however, the WMA cores from the wheelpaths had higher tensile strengths at both inspections. The difference is most likely attributed to sampling and testing variability, as all of the cores were taken at different longitudinal locations.
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70 additive Evotherm 3G developed by MeadWestvaco Asphalt Innovations. The estimated two-way AADT for County Road 513 was 1,000 vehicles with 6% trucks.
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71 Table 1.92 shows the production temperatures for each surface mix placed on this project. The plant was a portable parallel-flow drum plant manufactured by Dillman Equipment, Inc.
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72 first couple of hours of construction for each mixture. These volumetric samples were plant-mixed and compacted on-site in the NCAT mobile laboratory so that the mixes would not have to be reheated.
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73 Figure 1.65. Locations of test sections in Rapid River, Michigan.
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74 right wheelpath, and four 6-in.
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75 the same as previous projects. A summary of results for the core testing from the 13-month inspection compared to the construction data is shown in Table 1.98.
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Property HMA Advera Evotherm HMA Advera Evotherm Production Mix (July 2010) 13-Month Cores (August 2011)
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77 Performance Prediction The initial AADTT for County Road 513 near Rapid River, Michigan, was 60 trucks per day with one lane in each direction. The MEPDG suggests a typical minimum of 100 trucks per day, and this was used in the analysis.
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78 was also used for the WMA with no changes. The aggregate used for the design was a virgin crushed gravel blend with no RAP.
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79 mobile laboratory so that the mixes would not have to be reheated. The bulk specific gravity (Gmb)
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80 Figure 1.73. Portable parallel-flow drum plant in Baker, Montana.
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81 typical for all pavements in this area to be topped with a chip seal within the first year. Weather data were collected hourly at the paving location using a hand-held weather station.
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82 in accordance with AASHTO T 166. Six cores from each mix also were tested for tensile strength according to ASTM D6931.
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83 remaining on cores after trimming. The asphalt contents at 22 months were similar for both mixes and a little closer to the as-constructed results.
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84 higher in the wheelpaths for both sections, as expected. At the time of the first inspection, the tensile strength of the WMA was lower in the right wheelpath than between the wheelpaths.
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00.1 0.2 0.3 0.4 0.5 0.6 0.7 0 24 48 72 96 120 144 168 192 216 240 264 Ru t D ep th (i n.
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86 The asphalt mixture used for this trial consisted of a coarse-graded 9.5-mm NMAS Superpave mix design with a compactive effort of 75 gyrations. The mix design used for the HMA was also used for all WMA technologies with no changes.
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87 to be highly absorptive, which means there was residual moisture in the aggregate that was not completely removed in the drier. It was expected that the WMA mixes might have slightly higher mix moisture contents because of the lower mix production temperatures, which could leave more residual moisture in the aggregate or RAP going through the plant as compared to the HMA mixture.
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88 because of the high volume of traffic in the area. The HMA and Ultrafoam GX2 foam mixes were placed in the southbound outside and northbound outside lanes, respectively.
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89 verse cracks at the time of the first inspection. These four cracks totaled 8 ft (2.4 m)
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90 The surface textures of both the HMA and WMA test sections were measured using the sand patch test according to ASTM E965. The calculated mean texture depths for each mix are shown in Table 1.118.
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91 cores were substantially lower than the results from the production samples. The results of the 13-month cores are more consistent with the maximum specific gravity results and the slightly higher raveling in the HMA section.
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92 mixes, the average tensile strength between the wheelpaths was slightly greater than in the wheelpath. Performance Predictions The initial AADTT for Calumet Avenue, Munster, Indiana, was 2,697 trucks with two lanes in each direction.
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93 Property HMA Foam Evotherm Wax HMA Foam Evotherm Wax 13-Month Cores (October 2011) 24-Month Cores (September 2012)
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00.1 0.2 0.3 0.4 0.5 0.6 0.7 0 24 48 72 96 120 144 168 192 216 240 264 Ru t D ep th (i n.
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95 Level I IDT thermal cracking inputs were available for the Munster, Indiana, project. The predicted thermal cracking is presented in Figure 1.92.
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96 Volumetric Mix Properties Samples of both mixtures were obtained during production to compare moisture contents, percent coating, and volumetric properties between the HMA and WMA. Samples were taken from trucks leaving the plant.
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97 plant in Tallahassee. The WMA was placed in the eastbound lane while the HMA was placed in the westbound lane.
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98 cracking, and raveling. Cores were also extracted to determine the in-place density, indirect tensile strengths, theoretical maximum specific gravity, gradation, and asphalt content.
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99 Temperature (°F) Measuring Device HMA Terex Foam Average Temperature gun 296.3 273.3 PAVE-IR 268.4 247.0 Standard deviation Temperature gun 9.0 10.0 PAVE-IR 14.4 13.6 Maximum Temperature gun 312.3 287.7 PAVE-IR 304.0 278.0 Minimum Temperature gun 273.3 249.3 PAVE-IR 229.0 170.0 Table 1.127.
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100 For the second inspection, the sand patch test was performed both in the field and on the cores from the wheelpath. The calculated mean texture depths for each mix are shown in Table 1.131.
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101 Property HMA Terex Foam HMA Terex Foam HMA Terex Foam Production Mix (October 2010) 14-Month Cores (December 2011)
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102 Figure 1.99 compares the predicted longitudinal cracking for US-98 over the design life. More longitudinal cracking is predicted for the WMA (1,320 ft/mi)
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103 manufactured by the Arkema Group. The second WMA technology used was the additive BituTech PER produced by Engineered Additives, LLC.
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104 Volumetric Mix Properties Samples of each mixture were obtained during production to determine moisture contents, percent coating, and volumetric properties for comparisons between the HMA and WMA mixes. Samples were taken from a mini-stockpile made each day specifically for sampling.
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105 Construction The field sections on Little Neck Parkway were located approximately 12 miles from the plant. The travel time to the site ranged from 20 minutes to 50 minutes depending on the time of day and traffic.
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106 The densities for the BituTech PER and Cecabase RT mixes were similar; the densities for the HMA and SonneWarmix were lower. The tensile strengths for the Cecabase RT and SonneWarmix were slightly lower than for the HMA and BituTech PER.
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107 cally significant, however. Also, the surface texture results are similar for the 15-month and 26-month inspections, which indicates that weathering of the pavements had stabilized.
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108 4-in. cores typically yield higher tensile strengths compared to 6-in.
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109 Property HMA Bitu-Tech Cecabase SonneWarmix HMA Bitu-Tech Cecabase SonneWarmix Production Mix (October 2010) 15-Month Cores (January 2012)
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110 Hillside Avenue. The Cecabase and HMA were in the southbound lanes and the SonneWarmix and BituTech PER were in the northbound lanes.
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111 WMA and companion HMA control took place on December 6 and December 7, 2011, respectively. The asphalt mixture used for this trial consisted of a finegraded 19.0-mm NMAS Marshall mix design with a compactive effort of 75 blows.
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112 PG 70-10 asphalt binder supplied by Valero was used as the virgin binder for both mixes. The laboratory and production JMFs, optimum asphalt contents, specifications, and allowable tolerances are shown in Table 1.150.
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113 The percentages of completely coated particles were 96.2% and 96.3% for the HMA and Sasobit WMA mixtures, respectively. This shows that the WMA and HMA exhibited similar coating characteristics.
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114 Property Production JMF HMA Sasobit WMA Production Limits Sieve Size % Passing 25.0 mm (1")
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115 mixes were topped with a chip seal approximately 4 months after construction. It is typical for all pavements in this area with similar traffic to be topped with a chip seal.
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116 The gradations were similar for both mixes at the time of the inspection and were similar to the gradations from production. The asphalt contents of the 9-month cores were higher for the HMA than for the as-constructed mix samples.
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117 Layer Thickness (in.)
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118 Comparison of Observed and Predicted Performance of WMA and HMA for New Projects When evaluating new technologies, it is desirable to compare the long-term performance of both the new and the existing technologies. Because desired pavement performance is in the range of 12 years to 20 years, however, it is generally impractical to base comparisons on the long-term performance of field-test sections.
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119 WMA y = 0.1187x + 0.2879 R² = 0.0267 HMA y = 0.5164x + 0.3558 R² = 0.2285 0.0 1.0 2.0 3.0 4.0 5.0 6.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 O bs er ve d Ru t D ep th (m m ) MEPDG Predicted Rut Depth (mm)
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120 and 24 months. The comparison was performed for both the subtotal of all asphalt layers and the experimental (surface)
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121 Figure 1.113 shows a comparison of the observed and predicted cracking. The data that approximate both the 12-month and 24-month field visits are shown.
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122 the predicted thermal cracking after 12 years and 20 years of service. Table 1.164 presents the statistical comparison.
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123 peratures are less likely with parallel-flow plants than with more efficient counter-flow plants. Typically, exhaust gases for parallel-flow drum plants range from 20°F (11°C)
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124 temperatures are more susceptible to moisture, affecting flow back into the mix. • Condensation may only occur in a limited portion of the baghouse, such as the windward side.
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125 • Sticking of silo gate • Need to raise truck bed higher to break the load when dumping Hand work can be difficult at reduced temperatures, particularly in urban environments where more hand work is required for manholes, storm water inlet grates, valves, and so forth. The New York, New York, project required a significant amount of hand work by the paving crew.
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126 Statistical analyses were conducted to assess whether differences exist between warm mix asphalt (WMA) and hot mix asphalt (HMA)
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127 Age Grade HMA AQUABlack Production mix High temperature (°C) 77.9 75.3 Low temperature (°C)
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128 high temperature grade, and the low temperature grade was the same for both recovered binders. Munster, Indiana (Table 1.170)
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129 It can be observed that, with a few exceptions, the performance grades for the HMA and WMA binders were the same for most of the projects at different ages. But in all of these cases, the difference in binder grades was only one grade (up or down)
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130 Table 1.174. Temperature difference -- high and low true grade (WMA–HMA)
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131 all the mixes of each existing project. The results are as follows: St.
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132 comparison of means graphically in terms of equal, higher, or lower values using the statistical analysis presented in Table 1.177. Post-construction, in-place density results were not available for HMA sections on the projects in St.
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133 Single WMA Technology Projects Project Location WMA Technologies Std.
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134 Single WMA Technology Projects Project Location WMA Technologies Std.
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Single WMA Technology Projects Project Location WMA Technologies Std.
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136 Densities for Projects More Than 3 Years Old A summary of the statistical analysis of densities from cores more than 3 years old is presented in Table 1.180. All results presented in this table correspond to existing projects.
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137 Given that there are no replicates for binder absorption, comparison for WMA and HMA results were made using paired t-tests for all projects. For the field-mix cores, the p-value is 0.041, which indicates that binder absorption of HMA and WMA is statistically different.
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138 content of WMA mixes should not be reduced to account for reduced absorption. Dynamic Modulus Dynamic Modulus (E*
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139 Figure 1.120. Dynamic modulus master curves for Centreville, Virginia.
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140 Figure 1.122. Dynamic modulus master curves for Baker, Montana.
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141 Figure 1.124. Dynamic modulus master curves for Rapid River, Michigan.
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142 Statistical Comparisons To establish if there was actually a statistical difference in E* between HMA and WMA mixes on each project, two sample t-test analyses were conducted using a 90% confidence interval.
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143 Project WMA Tech.
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144 Project WMA Tech.
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145 Project Additive Test Temp.
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146 • Munster, Indiana: Evotherm (20°C)
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Single WMA Technology Projects Project Location WMA Technologies Std.
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148 Single WMA Technology Projects Project Location WMA Technologies Std.
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149 project, the Advera section had a higher tensile strength than the HMA section. Overall, tensile strengths on these two projects are lower than on the other projects because of the softer virgin binder used (PG 58-34)
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Single WMA Technology Projects Project Location WMA Technologies Std.
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151 that the thinner field cores allow the WMA binder to cure or stiffen more between the time the specimens are obtained from the field and tested for tensile strength. Figure 1.130 summarizes the statistical analyses presented in Table 1.191.
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152 Table 1.192. Summary of statistical analyses of tensile strengths, 1-year cores.
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153 a paired t-test for all projects. The p-value of the paired t-test was 0.312, which indicates that overall TSR values of the WMA and HMA mixes are not significantly different.
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154 Single WMA Technology Projects Project Location WMA Technologies Std.
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155 • Rapid River, Michigan, Advera and Evotherm 3G • Munster, Indiana, Gencor Ultrafoam • New York, New York, BituTech PER, Cecabase, and Sonne Warmix Except for the Sasobit mix from Casa Grande, Arizona, all of these WMA mixes had statistically higher Hamburg rut depths than did their corresponding HMA mixes. The Terex foam WMA from Jefferson County, Florida performed very well in the Hamburg test, however, and would not be considered to be different from its companion HMA in a practical sense.
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156 the stripping inflection points of WMA and HMA are the same (no statistical difference) ; five are lower (worse)
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Single WMA Technology Projects Project Location WMA Technologies Std.
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Table 1.197. Summary of statistical analyses of Hamburg stripping inflection points (SIPs)
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159 Figure 1.136, Figure 1.137, and Figure 1.138 show the pseudo-stiffness (C) versus damage parameter (S)
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160 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 50000 100000 150000 200000 250000 300000 Ps eu do -S ff ne ss (C ) Damage (S)
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161 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08 100 1000 Cy cl es to F ai lu re Microstrain NY HMA NY Bitutech PER NY Cecabase NY Sonnewarm Figure 1.140. AMPT fatigue results for New York, New York.
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162 actual field performance. The section is organized to discuss results and performance related to rutting, moisture damage, fatigue cracking, and low temperature cracking.
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163 were Jefferson County, Florida, and Casa Grande, Arizona. Table 1.201 summarizes the field measured rutting and the result of the laboratory rutting tests for the mixes from these two projects.
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164 River, Michigan, projects that used softer asphalt grades, nearly all mixes had tensile strengths above 100 psi. The TSR and conditioned tensile strength results indicate that the WMA and HMA mixes were generally resistant to moisture damage, which is consistent with the observation of no stripping in any field cores.
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165 not derived directly from replicate measurements as is commonly done for beam fatigue tests. Rather, the rankings are based on engineering judgment considering typical variability of fatigue testing and the observed spacing of the fatigue relationships on the log-log plots.
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166 fatigue test results and field performance, one project appeared to match, one did not match, and one was inconclusive. Low Temperature Cracking Thermal cracking characteristics were evaluated using the Indirect Tensile (IDT)
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From page 166... ...
167 from the Weather Underground website (www.wunder ground.com)
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From page 167... ...
168 The mixes from the warm mix asphalt (WMA) technology projects in Michigan, Indiana, and New York, along with the mixes from Montana and Florida, were verified according to the Draft Appendix to AASHTO R35: Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA)
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From page 168... ...
169 Table 1.207. Michigan design, field, and verification gradations and asphalt contents.
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From page 169... ...
170 Table 1.209. Montana design, field, and verification gradations and asphalt contents.
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From page 170... ...
171 SonneWarmix exceeded the d2s for relative density. The difference in voids for the HMA exceeded the 1s for relative density.
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From page 171... ...
172 Table 1.214. Summary of New York volumetric properties.
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From page 172... ...
173 Figure 1.142. Hydrofoamer (left)
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From page 173... ...
174 Table 1.217. Summary of Florida volumetric properties.
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From page 174... ...
175 0.4 0.3 0.2 0.1 0 0.1 0.2 0.3 0.4 0.5 P b a D iff er en ce , F ie ld - La b (% ) Figure 1.144.
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From page 175... ...
176 they are completely dry, heat transfer would tend to result in a degree of foaming with time. Essentially, this is the process used to produce low emission asphalt.
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From page 176... ...
177 y = 1.0906x 0.3129 R² = 0.0455 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 0.4 0.5 0.60.1 0.2 0.3 Di ffe re nc e in A ir vo id s, F ie ld - La b (% ) Field Mix Moisture Content (%)
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From page 177... ...
178 duced coating results that were similar to the degree of coating achieved in field mixtures. Compactability To evaluate the proposed WMA compaction temperature, the Appendix to AASHTO R 35 specifies that the ratio of the number of gyrations to 92% density at 30°C (54°F)
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From page 178... ...
179 between the field and laboratory results for six of the 10 mixes. Both Michigan WMAs had substantially lower TSR values for the laboratory-produced mixes, but the laboratory-verified optimum asphalt contents were also lower for these mixes.
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From page 179... ...
180 Table 1.222 shows a comparison of the laboratory-mixed and field-mixed flow number results. Since the laboratoryproduced samples were prepared at the optimum asphalt content determined from the mix verifications, differences in asphalt content as well as potential differences in aging affect the comparisons of the laboratory- and field-produced mix results.
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From page 180... ...
181 ducing a trial batch or run of WMA, it is recommended that the plant level out its production with HMA, then begin the water injection process and decrease the mixing temperature to the desired WMA production temperature. Once the desired WMA temperature is reached, obtain samples for testing." Commentary Full-scale asphalt plant foaming systems appear to provide better mixing and coating than laboratory-scale plants.
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From page 181... ...
Project Location Technology Avg. WMA Temperature (°F)
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From page 182... ...
183 error. Overall, this suggests that the binder content of WMA mixes should not be reduced to account for reduced absorption.
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From page 183... ...
184 in the Draft Appendix to AASHTO R 35, versus the average in-place density achieved at the time of construction. The diamonds represent the compactability ratio measured at the optimum asphalt content determined according to AASHTO R 35.
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From page 184... ...
185 Economics of a new technology like warm mix asphalt (WMA) often make up one of the principal factors that determine its acceptance into mainstream practice.
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From page 185... ...
186 $1/MMBtu for transportation and the supplier's overhead and profit, a contractor's cost for natural gas is estimated to be $5.78 per million Btu. Therefore, for a 25°F drop from HMA to WMA, the energy savings when using natural gas is estimated to be $0.16/ton of mix, as seen in equation (5)
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From page 186... ...
187 additive with antistripping capabilities is used, the estimated savings for that case is shown in equation (7)
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From page 187... ...
188 Production and Construction of WMA 1. Lower mix production temperatures associated with warm mix asphalt (WMA)
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From page 188... ...
189 3. Worker exposures to respirable fumes during paving with WMA were significantly reduced.
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From page 189... ...
190 These tensile strength tests were conducted on the same cores used to determine and compare in-place densities.
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From page 190... ...
191 Mix Design Verification 1. For laboratory-produced mixes aged for 2 hours at the observed field compaction temperature, theoretical maximum gravity and calculated binder absorption were generally lower than for field-produced mixes.
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From page 191... ...
192 1. Hansen, K
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From page 192... ...
193 24. Aschenbrener, T., B
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From page 193... ...
194 Florida The falling weight deflectometer (FWD) data were provided by the Florida Department of Transportation (DOT)
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From page 194... ...
195 removed from the core height for the Evotherm section; however, the HMA and Advera sections used full-depth core data. The construction start point was at the intersection of CR-513 and US-2.
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From page 195... ...
196 0.000 0.200 0.400 0.600 0.800 1.000 1.200 0 5000 10000 15000 20000 25000 SN eff De si gn S ub gr ad e Re si lie nt M od ul us (p si ) Staon (Mile Marker)
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From page 196... ...
197 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0 2000 4000 6000 8000 10000 12000 14000 16000 SN eff De si gn S ub gr ad e Re si lie nt M od ul us (p si ) Staon Indiana NB FWD Analysis (Foam)
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From page 197... ...
198 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 SN eff De si gn S ub gr ad e Re si lie nt M od ul us (p si ) Staon Michigan Advera Surface NB Design Mr Design Mr Average SNeff SNeff Average Figure 1.A.6.
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From page 198... ...
199 There were no mileposts on this section of roadway. The SonneWarmix section started from the intersection of 87th Drive and Little Neck Parkway, while the BituTech PER section started at the intersection of Hillside Avenue and Little Neck Parkway.
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From page 199... ...
200 0.00 1.00 2.00 3.00 4.00 5.00 6.00 0 2000 4000 6000 8000 10000 12000 14000 16000 SN eff De si gn S ub gr ad e Re si lie nt M od ul us (p si ) Staon New York Cecabase SB Design Mr Design Mr Average SNeff SNeff Average Figure 1.A.9.
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From page 200... ...
201 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0 2000 4000 6000 8000 10000 12000 14000 SN eff De si gn S ub gr ad e Re si lie nt M od ul us (p si ) Staon New York Astec PER NB Design Mr Design Mr Average SNeff Sneff Average Figure 1.A.11.
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Key Terms
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More
information on Chapter Skim is available.