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The data on changing asphalt properties, especially the low-temperature ductility measured at 39.2 and 60°F (4 and 15.6°C), have been analyzed and related to the performance of ten experimental pavements in Pennsylvania.
It has been observed that aging of the pavement results in progressively lower penetration and higher viscosity. However, the accompanying decrease in low-temperature ductility is an important factor. After the penetration of asphalt drops below 30 due to hardening. the pavements containing asphalt with low ductilities are likely to show poorer service than pavements containing asphalts of the same penetration but with high ductilities. The data also indicate the probable ranges of low-temperature ductility values at which the progressive deterioration of the pavement (such as loss of fines, raveling, cracking, etc.) takes place under Pennsylvania climatic conditions.
At lower temperatures, the ductility values are lower, reproducible, and better defined than the values at higher temperatures determined on long, thin threads of asphalt. Therefore, a specification requirement at a 60°F or lower temperature should provide better criteria.
bitumens, asphalts, bituminous cements, durability, ductility, low temperature tests, bituminous concretes, roads, pavements
Bituminous testing and research engineer, Bureau of Materials, Testing and Research, Pennsylvania Department of Transportation, Harrisburg, Pa.