Short-Term Laboratory Conditioning of Asphalt Mixtures (2015) / Chapter Skim
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Pages 103-119
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From page 103... ...
B-1 A P P E N D I X B Objective and Scope .
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B-2 been a significant amount of work on aging of asphalt binders, there has been very little work investigating the effects of different types of asphalt plants on aging characteristics of asphalt binders . Much of the information on the effect of plant operations on asphalt aging was developed based on the experience of the research team .
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B-3 this aging process . Knowing the effect of binder and mixture properties on short-term aging will allow these components to be controlled so that the effect of plant operations can be more accurately determined .
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B-4 These higher temperatures may provide for a more workable mixture and a safety factor in mixture temperature in case there is a delay in the construction operation . It is reasonable to believe that this increase in temperature has increased the rate of mixture aging resulting in some loss in durability .
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B-5 Plant Type Lund and Wilson (1984) compared the aging in asphalt binder between batch mix plants (BMPs)
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B-6 particles that are less than approximately 20µm in diameter may become part of the asphalt binder, causing an increase in hardening of the binder and a stiffer mixture . An increase in the dust percentage will normally fill some of the voids in the aggregate matrix and hence decrease the VMAs .
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B-7 elevator, referred to as the hot elevator, and discharged from the elevator onto a set of vibrating screens where it is separated by size and deposited into hot bins . The correct aggregate proportion to be used from each bin is determined by weight by its introduction into a weigh hopper .
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B-8 indirectly by drum diameter, length of mixing unit, slope, and speed of rotation of the drum . Changes in mixing time and temperature will definitely affect the aging of the binder .
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B-9 and the air flow evaporate the moisture in the aggregate . Because of this, the time the aggregate temperature remains constant depends in part on its moisture and its porosity (US Army Corps of Engineers 2000)
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B-10 lift some of the aggregate from the bottom of the drum and tumble the material through the exhaust gases . The aggregate then moves down the drum; near the center of the drum, a veil of aggregate develops across the cross-sectional area .
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B-11 mixing unit inside the drum but located on the end of the drum behind the flame . The second type refers to a drum mixer most commonly referred to as a double-barrel plant that has the mixing unit folded back around the aggregate dryer portion of the drum .
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B-12 from the inner drum into the nonrotating outer shell or drum (US Army Corps of Engineers 2000)
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B-13 mixing time . The mixing time is controlled by the rate of production, slope of mixer, and the capacity of the mixer .
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B-14 Table B-1. Description of asphalt plants produced by selected plant manufacturers.
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B-15 tested during the construction operation, so it is not known if the properties change significantly or not . Surprisingly, there is not much literature that looks at the amount of oxidation, if any, that occurs in the storage silo .
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B-16 will help ensure that excess oxidation has not occurred to the asphalt binder at the time of mixing . Storage of asphalt for 6 hours or less is recommended .
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B-17 References Anderson, D .
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