Using Recycled Asphalt Shingles with Warm Mix Asphalt Technologies (2018) / Chapter Skim
Currently Skimming:
Pages 30-102
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 30... ...
30 Production, Construction, and Performance of Field Projects Production and construction information were collected from three WMA–RAS projects built before the start of this study and five new WMA–RAS projects that were constructed and monitored during the course of this study. The projects built before this study are referred to as the "existing projects"; the five projects built and evaluated during this study are referred to as the "new projects." For each project (existing and new)
|
From page 31... ...
31 Texas DOT Section Number Base Binder WMA RAP (%)
|
From page 32... ...
32 Figure 3-1. Test section layout on FM 973 in Austin, Texas.
|
From page 33... ...
In -P la ce D en si ty (% ) WMA PG 64-22 15%–3% HMA PG 64-22 15%–3% HMA PG 58-28 15%–3% HMA PG 64-22 0%–5% Figure 3-2.
|
From page 34... ...
34 The HMA mix with 15% RAP and 3% RAS using a PG 64-22 binder exhibited the most cracking, with block cracking observed in all three data sections. Figure 3-3 shows one of the three cracks observed in the WMA section, while Figure 3-4 shows the block cracking observed throughout the HMA 15% RAP–3% RAS sections.
|
From page 35... ...
35 section in the HMA mix using a PG 58-28 binder was no longer in service at the time of this inspection. Traffic had been diverted, and construction was underway on a new bridge south of the test sections.
|
From page 36... ...
36 Mix Mean Texture Depth (mm) Standard Deviation Mean Texture Depth (mm)
|
From page 37... ...
37 But for the purposes of this research, only the outside westbound lane from Mileposts 113.0 to 91.5 was investigated. The stone matrix asphalt mixtures on this project consisted of a 19-mm NMAS gradation with a compactive effort of 80 gyrations.
|
From page 38... ...
38 were taken from between the wheelpaths for each mix to determine the in-place density after each time period. Rutting.
|
From page 39... ...
39 of these cracks appeared to be reflective cracking from the underlying concrete, since cracks were evident across both lanes and the shoulder at these locations. To verify the type of cracking, two cores were taken on transverse cracks in 2015, and two more were taken in 2016.
|
From page 40... ...
40 (a) Low-Severity Transverse Crack, Gravel (b)
|
From page 41... ...
41 Mix Mean Texture Depth (mm) Standard Deviation Mean Texture Depth (mm)
|
From page 42... ...
42 ANOVA was performed to evaluate how the mix (gravel or quartzite) , the age of the pavement, and the interaction between these two variables affected the in-place density.
|
From page 43... ...
43 Production temperatures and rates were monitored and recorded throughout production of the two mixes. Table 3-15 shows production temperature information, and Table 3-16 shows the production rates and totals.
|
From page 44... ...
44 Note: na = not applicable; NA = not available. aNo WMA technology.
|
From page 45... ...
45 Figure 3-18. Location of test sections in Fort Worth, Texas.
|
From page 46... ...
46 Figure 3-20 shows an example of the surface of the mat during construction. Ten cores were obtained from the HMA mix section, and six were obtained from the WMA sections.
|
From page 48... ...
48 Mix Mean Texture Depth (mm) Standard Deviation Mean Texture Depth (mm)
|
From page 49... ...
49 The asphalt mixtures consisted of a fine-graded 12.5-mm NMAS Superpave mix design with a compactive effort of 75 gyrations. The same mix design was used for all three mixes, with the only difference between the HMA and WMA mixes being the addition of the WMA additives.
|
From page 50... ...
50 plant operator for monitoring the amount of each material being introduced. Second, the drum was fitted with two separate recycled material collars to better control feed rates for RAP and RAS.
|
From page 51... ...
51 Table 3-25a and Table 3-25b show the results from NCAT's testing on the three Wisconsin mixes. The values shown in these tables are based on NCAT's work with the large sample taken once the mix production was stable.
|
From page 52... ...
52 intermediate course was placed, followed by a 1.75-in. surface course.
|
From page 53... ...
53 Figure 3-30. Location of test sections near Larsen, Wisconsin.
|
From page 54... ...
54 Three rollers were used for compaction to target a minimum in-place density of 91.5%. The breakdown roller -- a Sakai SW850 -- was operated in vibratory mode for five passes.
|
From page 55... ...
55 they can break and cause surface pop-outs. These pop-outs were not observed to have worsened in severity between the two inspections.
|
From page 56... ...
56 While the control section had a slightly higher density compared to the two sections with WMA additives at the time of construction, the densities of all sections increased with traffic and were similar by the first inspection. ANOVA was performed to determine how the mix type (HMA or WMA)
|
From page 57... ...
57 lower than the QC laboratory's results. Upon investigation, it was learned that the QC laboratory was not heating their gyratory molds but instead used cold molds for compaction, which caused higher air voids for their QC samples.
|
From page 58... ...
58 Aggregate Type Mix Design (%) Production Low Air Void WMA (%)
|
From page 59... ...
59 Production temperatures and rates recorded throughout production of the four mixes are summarized in Table 3-34. Production temperatures for the WMA mixtures were generally 40°F to 50°F lower than the HMA mixtures.
|
From page 60... ...
60 asphalt content from both methods are shown in Table 3-36. For each of the mix samples, the results from the solvent extractions were higher than for the ignition method.
|
From page 61... ...
61 the mixtures were similar.
|
From page 62... ...
62 Figure 3-42. Location of test sections in Enterprise, Alabama.
|
From page 63... ...
63 Statistic Low Air Void WMA Temp.
|
From page 64... ...
64 Source df Adjusted SS Adjusted MS F-Value P-Value Air voids 1 9.35 9.35 5.73 0.044 Mix type 1 6.45 6.45 3.95 0.082 Mix type × Air voids 1 0.03 0.03 0.02 0.897 Error 8 13.07 1.63 Total 11 28.89 Statistical Grouping Air voids N Mean Grouping Low 6 93.3 A Adjusted 6 91.5 B Table 3-39. Initial density ANOVA for Enterprise, Alabama.
|
From page 65... ...
65 were still within the normal range for dense-graded mixes. Figure 3-49 shows examples of the surface texture for the low air void WMA and the low air void HMA and for the adjusted air void WMA and the adjusted air void HMA, respectively.
|
From page 66... ...
66 Figure 3-50. Example of binder pooling on surface in Enterprise, Alabama.
|
From page 67... ...
67 Source df Adjusted SS Adjusted MS F-Value P-Value Mix type 3 12.19 4.06 3.01 0.041 Age 2 27.43 13.72 10.16 0.001 Mix type × Age 6 21.5 3.58 2.66 0.029 Error 40 53.99 1.35 Total 51 113.14 Statistical Grouping Age (months) N Mean Grouping 29 20 94.3 A 17 20 93.8 A 0 12 92.4 B Mix Type N Mean Grouping Low air void WMA 13 94.1 A Low air void HMA 13 93.9 A Adjusted air void HMA 13 93.3 A B Adjusted air void WMA 13 92.8 B Mix type × Age (months)
|
From page 68... ...
68 Compactor, a density correlation was conducted on site to determine the number of gyrations that provided the same density as 75 blows with the Marshall hammer. This yielded a seemingly low gyration level of 25.
|
From page 69... ...
69 Sieve Size Percent Passing JMFa HMAa WMA (Evotherm 3G) Tolerance 19.0 mm (3/4 in.)
|
From page 70... ...
70 Construction. The two test sections were placed in the westbound lane of Raccoon Valley Drive.
|
From page 71... ...
71 The WMA section averaged about 50°F lower than the HMA section. Three rollers were used for compaction of both mixes.
|
From page 72... ...
72 Field Cores. At the time of each inspection, five cores were obtained from both sections.
|
From page 73... ...
73 Figure 3-58. Example of surface texture of HMA in Oak Ridge, Tennessee (2015)
|
From page 74... ...
74 Aggregate Type Mix Design MW–RAS Mixes (%) Production MW–RAS HMA (%)
|
From page 75... ...
75 Figure 3-61. Astec Double Barrel plant used in Simms, North Carolina.
|
From page 76... ...
76 Variable MW–RAS JMFa MW–RAS HMAa MW–RAS WMA (Evotherm 3G) Tolerance Asphalt content (%)
|
From page 77... ...
77 The asphalt content of each mix was determined both by ignition method and by solvent extraction. The binders were recovered and graded after extractions.
|
From page 78... ...
78 Figure 3-62. Location of test sections in Wilson, North Carolina.
|
From page 79... ...
79 This was repeated on the other side of the mat, and was then followed by one last static pass back up the middle of the mat. The same pattern was used for the breakdown roller.
|
From page 80... ...
80 Table 3-64 shows the results of ANOVA to evaluate how the mix type (HMA, WMA, MW–RAS, and PC–RAS) , the age of the pavement, and the interaction between mix type and age affected the in-place density.
|
From page 81... ...
81 Statistic MW–RAS HMA MW–RAS WMA PC–RAS HMA PC–RAS WMA Mean texture depth (mm) 0.4 0.3 0.4 0.4 Standard deviation (mm)
|
From page 82... ...
82 Superpave mix design mixes with a compactive effort of 75 gyrations. The WMA mix contained 15% RAP and 3% MW–RAS with a limestone and slag virgin aggregate blend.
|
From page 83... ...
83 Figure 3-72. Asphalt plant in La Porte, Indiana.
|
From page 84... ...
84 20 mi from the plant, which yielded an average haul time of 25 to 35 min. The test sections were paved to a target thickness of 1.5 in.
|
From page 85... ...
Figure 3-73. Location of test sections in La Porte, Indiana.
|
From page 86... ...
86 problems were reported during production and no issues during construction were found. For the Larsen, Wisconsin, project, the production temperatures for the HMA and WMA mixtures were similar.
|
From page 87... ...
87 Location Construction Date Mix Variables Production/Construction Notes Larsen, Wisconsin September 2013 HMA and two WMA additives No troubles. WMA and HMA production temperatures were within 10°F.
|
From page 88... ...
88 Location Mix Variable Age Field Performance SR-96 Larsen, Wisconsin Control, Rediset, Zycotherm 24 months Minor reflective cracking over unrubblized portland cement concrete pavement US-84 Enterprise, Alabama HMA and WMA (low air void) HMA and WMA (adjusted air void)
|
From page 89... ...
89 methods on any project can be influenced by inaccurate correction factors caused by recycled materials and natural variations in virgin aggregates. This table also compares the asphalt content of the HMA and WMA samples for each project location and additional project variables for both test methods.
|
From page 90... ...
90 for temperature control was used for grading all recovered binders. The bending beam rheometer samples of unaged RAS were tested at 0°C and +6°C, the two highest temperatures at which the bending beam rheometer bath can maintain temperature control.
|
From page 91... ...
91 The LAS Test, which is based on viscoelastic continuum damage mechanics, was conducted at 2.5% and 5.0% strain. Table 3-81 shows the results of LAS binder testing.
|
From page 92... ...
92 1.0 10.0 100.0 1,000.0 10,000.0 1.00E-06 1.00E-04 1.00E-02 1.00E+00 1.00E+02 1.00E+04 D yn am ic M od ul us (k si ) Reduced Frequency (Hz)
|
From page 93... ...
93 The master curves for the Tennessee mixtures are shown in Figure 3-80. Despite the WMA mixture having a substantially higher asphalt content, the HMA mixture was stiffer than the WMA mixture throughout most of the master curve.
|
From page 94... ...
94 1.0 10.0 100.0 1,000.0 10,000.0 D yn am ic M od ul us (k si ) HMA MW–RAS HMA PC–RAS WMA PC–RAS WMA MW–RAS Figure 3-81.
|
From page 95... ...
95 Location Mix ID Max.
|
From page 97... ...
97 The last column in Table 3-86 includes an interpolated number of cycles at a strain level of 400 µ to have a common baseline for comparisons. The ranking arrangement showed mixed results with no performance tendency between HMA and WMA (Figure 3-84)
|
From page 98... ...
98 for Florida's climate and materials. Different criteria may be required for other regions.
|
From page 99... ...
99 Location Mix ID Average Uncorrected Strength (psi) Average Corrected Strength (psi)
|
From page 101... ...
101 Carolina projects. For the Alabama mixtures, higher Jc values indicate an improvement in fracture resistance because of the use of WMA technology.
|
From page 102... ...
102 Location and Age Mix ID Sample Air Voids (%) Flexibility Index Thickness Corrected Average Average Standard Deviation CV (%)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.