Use of Reclaimed Asphalt Pavement and Recycled Asphalt Shingles in Asphalt Mixtures (2016) / Chapter Skim
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Pages 75-93
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76 • 2005–2010 -- Additional performance (rut testing) and durability (permeability)
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77 • Likely to show an accumulation of coarser particles behind the paver screed at the auger gear box (center of screed) , at screed extensions, and at the outside edges of the screed (e.g., longitudinal joints)
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78 Between 2005 and 2010, performance testing for mixture approval was added to GDOT's mix design procedures. The Hamburg wheel tracking device is used to evaluate the mixture rutting potential.
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79 – Mix RAP aggregate remaining at the end of ignition oven testing increasing percentages of virgin asphalt in increments of 0.25% to 0.5%. • Part 2: – Preheat RAP to a temperature achieved during dry mixing at the plant.
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80 would be measured for the asphalt mixture produced at the plant will be 5.93%. Step 4: Performance and Durability Check Additional samples are prepared using the COAC, and rutting potential (APA rut testing)
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81 the percentage of RAP increases to 25% or more, the clients are more likely to specify the RAP asphalt availability factor. From four to six agencies specify the RAS or combination of RAP/RAS asphalt availability factors.
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82 burning. The difference between what is burned and the optimum is the (ignition oven)
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83 Additional comments provided by the contractors included: • Recycled materials are dried before batching: – In air – In an oven at: n 140°F (60°C)
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84 Performance testing of mixtures is limited to using the APA to evaluate the rutting potential during the mix design. A few of the contractors indicated that they do not evaluate rut resistance; however, some of their clients do use the Hamburg (dry, wet)
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85 RAP may need to limit the silo storage time to prevent the mixture from getting too stiff. Batch plant (three contractors)
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86 Contaminates do not mix with the other mixture components and result in a nonuniform asphalt mixture. Contaminates can sometimes be identified in the finished pavement surface.
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87 do not cool as quickly as thin lifts. Using a material transfer device helps keep the mixture blended (i.e., limits segregation)
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88 Missouri DOT changed its specifications in 2012 to address previously identified mix design problems for BP-1, BP-2, BP-3, and bituminous base mixtures. The specification changes include: • Lowered design air voids to 3.5%.
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89 • Year constructed, • Design type (wear or nonwear) , • Mix design record, • Asphalt performance grade, • Total asphalt content (recycled asphalt plus virgin asphalt)
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90 Year Type (lift in.) PG Grade Lift Thickness RAP, % Total Asphalt Content Virgin Asphalt Added No.
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91 FIGURE 36 Appearance of No. 6 limestone after dry mixing with RAP in laboratory pugmill (Source: Hines 2015)
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92 Temperatures and % RAP 420°F 10% RAP 490°F 24% RAP 400°F 24% RAP Samples from haul trucks for Run 1, Run 2, and Run 3 FIGURE 39 RAP asphalt transferred to virgin aggregate after dry mixing for 30 seconds in batch plant (Source: Johnson et al.
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93 Run 1 Run 2 Run 3 FIGURE 40 Balls of asphalt and fines after dry mixing in batch plant (no virgin asphalt) (Source: Johnson et al.
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94 to calculate the percentage of uncoated, partially coated, and completely coated particles. Visual evaluations showed: • Duplication of dry mixing at the batch plant was not replicated in the laboratory.
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