Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Hot Mix Asphalt (HMA) Characterization for the 2002 AASHTO Design Guide
The two study objectives were to conduct dynamic modulus and APA rutting tests of selected Mississippi HMA mixtures. A total of twenty-five mixtures were tested including aggregate combinations of gravel and gravel/limestone; 9.5mm, 12.5mm and 19.0mm NMAS gradations; asphalt binder grades of PG 67-22, PG 76-22 and 82-22; and compaction N(sub design) levels of 50, 65 and 85. Twenty-four of the mixtures were designed for four percent air voids and one was designed for three percent air voids. Sample preparation proved to be problematic. Target air void content for the dynamic modulus samples was 7.0 plus or minus 0.5 percent. Results (air voids) for a given compaction level can vary with gradation, aggregate type, asphalt content and mass of mix compacted. Another problem is the density gradient of Superpave gyratory compacted cylindrical samples. Developers of the test method minimized the density gradient by cutting a 100mm core from the larger, original 150mm sample. To achieve the target air void content of 7.0 plus or minus 0.5 percent for cored dynamic modulus test specimens, the 150mm samples were compacted to an air void level of approximately 8.0 plus or minus 0.5 percent. Because of uncertainty in the air void level that would be produced, four to five 150mm samples of a mixture were compacted with a goal of producing three with the target air void level. The cored 100mm diameter test specimens were checked that the target 7.0 plus or minus 0.5 percent air void level was achieved. In some cases, new samples and cored specimens had to be prepared with an adjusted air void level. After compaction, specimen preparation for dynamic modulus testing requires fixtures, coring equipment and saw rugged enough to produce specimens meeting required geometric tolerances. Some end spalling during sawing was largely stopped by wrapping duct tape around the specimens ends. Results of the study were parameters of the fitted sigmoid functions and associated shift factors of the master curve for twenty-fine HMA mixtures. MDOT will use these functions to estimate HMA dynamic modulus as input for calibrating the 2002 pavement design guide. Asphalt Pavement Analyzer rutting test results for the twenty-five mixtures are compared with MDOT rutting criteria.
Hot Mix Asphalt (HMA) Characterization for the 2002 AASHTO Design Guide
The two study objectives were to conduct dynamic modulus and APA rutting tests of selected Mississippi HMA mixtures. A total of twenty-five mixtures were tested including aggregate combinations of gravel and gravel/limestone; 9.5mm, 12.5mm and 19.0mm NMAS gradations; asphalt binder grades of PG 67-22, PG 76-22 and 82-22; and compaction N(sub design) levels of 50, 65 and 85. Twenty-four of the mixtures were designed for four percent air voids and one was designed for three percent air voids. Sample preparation proved to be problematic. Target air void content for the dynamic modulus samples was 7.0 plus or minus 0.5 percent. Results (air voids) for a given compaction level can vary with gradation, aggregate type, asphalt content and mass of mix compacted. Another problem is the density gradient of Superpave gyratory compacted cylindrical samples. Developers of the test method minimized the density gradient by cutting a 100mm core from the larger, original 150mm sample. To achieve the target air void content of 7.0 plus or minus 0.5 percent for cored dynamic modulus test specimens, the 150mm samples were compacted to an air void level of approximately 8.0 plus or minus 0.5 percent. Because of uncertainty in the air void level that would be produced, four to five 150mm samples of a mixture were compacted with a goal of producing three with the target air void level. The cored 100mm diameter test specimens were checked that the target 7.0 plus or minus 0.5 percent air void level was achieved. In some cases, new samples and cored specimens had to be prepared with an adjusted air void level. After compaction, specimen preparation for dynamic modulus testing requires fixtures, coring equipment and saw rugged enough to produce specimens meeting required geometric tolerances. Some end spalling during sawing was largely stopped by wrapping duct tape around the specimens ends. Results of the study were parameters of the fitted sigmoid functions and associated shift factors of the master curve for twenty-fine HMA mixtures. MDOT will use these functions to estimate HMA dynamic modulus as input for calibrating the 2002 pavement design guide. Asphalt Pavement Analyzer rutting test results for the twenty-five mixtures are compared with MDOT rutting criteria.
Hot Mix Asphalt (HMA) Characterization for the 2002 AASHTO Design Guide
T. D. White (Autor:in) / J. C. Littlefield (Autor:in) / J. Pittman (Autor:in) / R. C. Plummer (Autor:in) / J. R. Easterling (Autor:in)
2008
122 pages
Report
Keine Angabe
Englisch
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