Use of Recycling Agents in Asphalt Concrete Mixtures (2022) / Chapter Skim
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8 2.1 Introduction This chapter present results of the literature review related to the use and evaluation of RAs in asphalt mixtures. This review covers a wide range of topics, including factors that affect the properties of RAs, methodologies used to determine the type and dosage of RAs, U.S.
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 9 Early efforts from Rostler and co-workers at Witco/Golden Bear (Rostler and White 1959; Kari et al.
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10 Use of Recycling Agents in Asphalt Concrete Mixtures The use of refined tallow increased the penetration level of the blend to the same level of the virgin binder with a dosage of 9.7% (by binder weight) , while naphthenic flux oil, WEO + FT wax, and WEO bottoms were found to be ineffective at reducing the viscosity of the aged asphalt within the tested dosage rates.
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 11 viscosity or penetration of the RA-treated binder blends with various amounts of RA to select the appropriate dose to meet the desired viscosity and penetration levels [Little et al. 1981; Zaumanis et al.
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12 Use of Recycling Agents in Asphalt Concrete Mixtures of asphalt binder modifiers, potential uses of re-refined engine oil bottoms (REOB) , and bio- additives.
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 13 2.4 Current Methods and Practices for Evaluation of RA-Treated Binder Blends This section summarizes the results from the literature review on various methods and practices that have been used to evaluate RA-treated asphalt binders. 2.4.1 Analytical Methods Many binder analytical methods have been used to evaluate chemical composition and identify important elements and functional groups, as well track the change of chemical properties for asphalt binders with RAs.
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14 Use of Recycling Agents in Asphalt Concrete Mixtures elements, typically from sodium to uranium in the periodic table (Barborak et al. 2016; Arnold, 2017)
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 15 Many research efforts (Masson et al. 2006; Masson et al.
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16 Use of Recycling Agents in Asphalt Concrete Mixtures DSC is the most widely used approach to determine the enthalpy-related transitions of asphalt binders and of polymeric materials. DSC analyses have been used successfully to evaluate the glass transition temperature (Tg)
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 17 2.4.4 Binder Performance Tests Although the binder penetration, viscosity, and PG grading systems have been extensively used to evaluate the properties of RA-treated binders, these methods, based only on traditional binder tests, may not be sufficient to fully reflect the behavior of complex asphalt blends and mixtures. Therefore, other mechanical tests and data analysis methods and tools have been developed and employed to evaluate asphalt blends and mixtures containing RAM and RAs.
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18 Use of Recycling Agents in Asphalt Concrete Mixtures representations of dynamic modulus and phase angle of viscoelastic materials) from E*
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 19 2.5.2 Permanent Deformation Rutting or permanent deformation is one of the major distresses in asphalt pavements. Resistance to rutting is a critical component of performance in the field.
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20 Use of Recycling Agents in Asphalt Concrete Mixtures thermal stress and strain test (UTSST)
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 21 damage. For asphalt mixtures that are susceptible to moisture, the internal bond between the binder and aggregate is weakened in the presence of water, which may lead to stripping and further significant damage of the asphalt pavement.
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22 Use of Recycling Agents in Asphalt Concrete Mixtures simulation, TxACOL/S-TxACOL for rutting and reflective cracking performance simulation, FlexPAVE for rutting and fatigue cracking performance prediction, and IlliTC for thermal cracking performance simulation. The biggest advantage of these advanced models is that they provide agencies and researchers a way to use laboratory-measured material properties to predict mixture performance in the context of local traffic and climate conditions (Zhang et al.
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 23 conditions are evaluated using finite-element analysis with a cohesive zone fracture model to simulate quasi-brittle cracking in asphalt concrete. For predicting the thermal performance of a specific pavement section, the relaxation modulus/creep compliance and fracture energy (from the DCT test)
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24 Use of Recycling Agents in Asphalt Concrete Mixtures in identifying how RAs affect the RAP binder chemically and mechanically. Mohammadafzali et al.
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 25 and an organic blend based on organic oils. The study found that the mixture experienced less aging with the use of RAs regardless of aging period.
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26 Use of Recycling Agents in Asphalt Concrete Mixtures Life-Cycle Assessment and Life-Cycle Cost Analysis Researchers have employed LCA and LCCA to evaluate and compare the environmental impacts and cost analysis of asphalt binders and mixtures containing RAP/RAS with virgin material (Mukherjee et al.
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Literature Review of Use of Recycling Agents in Asphalt Mixtures 27 2.8 Summary A summary of the findings from the literature review is presented here. RA is defined as a material with chemical and physical characteristics selected or designed to restore or rejuvenate the properties of aged asphalt to desired specifications.
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28 Use of Recycling Agents in Asphalt Concrete Mixtures The available methods for characterizing the RA-treated asphalt mixtures documented in the literature include (1) methods for measuring stiffness or viscoelastic characterization (e.g., E*
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