Yuriko Kizu
A study on comparison between an actually measured value and a calculated value of theoretical maximum specific gravity of asphalt mixtures
Osamu Takahashi
A theoretical maximum specific gravity of asphalt mixtures has been determined by a calculation method or a measurement method. The value from the calculation method is figured out based on the each specific gravity of the mixture ingredients and their blend percentages. On the other hand, the value from the measurement method, called Rice method, is obtained using the separated particles of the sample mixture.
Japanese pavement engineers use the calculation method on a process of mixture design, whereas U.S. and Canadian pavement engineers commonly use Rice method because of the rationality.
Japanese pavement engineers should discuss the advantage aspects and the test procedures on Rice method, since many countries are changing from the calculation method to the measurement method.
This study improved the testing apparatus, which was developed by the last research of the laboratory, and evaluated the test protocol of Rice method standardized in AASHTO. The study also investigated a quantitative difference between the values of theoretical maximum specific gravity determined by calculation method and Rice method.
The following findings were obtained form the study.
a) Sufficient agitation of the separated particles is very important to remove air trapped in the sample.
b) The difference between the values determined by calculation method and Rice method is about 0.03 for dense graded mixtures with 13 mm of maximum aggregate size.
c) The difference of theoretical maximum specific gravity probably causes the decrease of 0.3 % in design asphalt content. This decreased asphalt content considerably influences physical properties of the asphalt concrete.
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