Construction and Maintenance Practices for Permeable Friction Courses (2009) / Chapter Skim
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Pages 32-42
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From page 32... ...
Materials Selection Materials needing selection include coarse aggregates, fine aggregates, mineral fillers, asphalt binders, and stabilizing additives. The current state of practice for selection of these materials is discussed here.
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. Asphalt Binders A wide range of asphalt binders have been used in PFC mixes.
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Generally, the literature indicates that binders with a high stiffness are needed for PFCs, hence most agencies require modified asphalt binders. High stiffness binders are needed to help prevent draindown which promotes thick films of asphalt binder coating the aggregates.
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Use of modified asphalt binders helps to retain the thick asphalt binder film, thus improving durability. In addition, research has shown that the use of modified asphalt binders improves the short-term performance of PFCs.
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Within this section, only typical PFC gradations will be discussed because the following section will provide the different mix design criteria. The literature review and survey of agencies resulted in a wide range of gradations encountered for PFC mixes.
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1 in. Permeable Friction Course Gradations ~ US Agencies Figure 17.
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Selection of Optimum Binder Content The philosophy of selecting the optimum binder content for PFC mixes is relatively uniform around the world. However, no specific process or procedure that identified an absolute optimum asphalt binder content was identified.
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Permeable Friction Course Gradations ~ International Agencies Figure 20.
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A maximum asphalt binder content is identified by conducting some type of draindown potential test; more asphalt binder improves durability, but too much asphalt binder leads to draindown. The Cantabro Abrasion test is the most common test utilized worldwide to evaluate the durability of PFC mixes.
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From page 41... ...
for 1 hour. A visual examination of the bowl is conducted after the 1 hour to qualify the amount of asphalt binder left in the Pyrex bowl.
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(36) used the Asphalt Pavement Analyzer to evaluate the stability of PFC mixes.
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