Research Topics by Professor Takahashi Osamu
Study on volumetric mix design method using Superpave gyratory Compactor
Study on SMA mixture design for binder course of the grid-panel-type buried joint
SHRP (Strategic Highway Research Program) has developed the new asphalt mixture design method called Superpave (Superior Performing Asphalt Pavement). In the U.S. Superpave method was planned to replace the conventional design procedures, like Hveem method and Marshall method. This method has been introduced and studied not only in European countries but also in some Asian countries, like Korea and China.Superpave method ties asphalt binder grading system and aggregate selection into the mixture design process, and considers traffic and climate conditions at the construction field as well. Superpave gyratory compactor (SGC) has been developed as the rational compaction device to relate the compaction effort to the expected traffic.
Introduction of SGC is the most remarkable point in the Superpave design procedures. In our country, an evaluation concerning the procedure of Superpave design method has not been sufficiently studied. SGC has been introduced in many research organizations, even though SGC can’t be applied to the conventional design method. However Japanese researchers accept that SGC is more suitable for a HMA design procedure than Marshall rammer.Japanese pavement researchers should study Superpave design method and make an effort to use SGC in HMA design procedure. Japanese HMA design method should be improved in a view point of rationality.
The objective of this research is to develop a volumetric design method using SGC based on the Japanese Marshall design method. The developed design method should provide the same design asphalt content, which is obtained by the conventional Japanese Marshall design method.
This objective is divided into following sub-objectives; (a)To decide the numbers of SGC revolution corresponding to the 50 and 75 blows of Marshall rammer. (b)To establish design parameters that take the place of Marshall stability and flow values. (c)To evaluate the validity of the HMA design method, which incorporates above-mentioned a) and b).
Reference
Nishioka K., Takahashi O., Itoh I. and Taguchi H. : A study on a number of SGC revolution based on Marshall rammer blows, The 62nd conference of JSCE, 5-103, 2007.9. (in Japanese)
A buried joint system is one of effective methods for joint-less on roadway viaducts.The grid-panel-type buried joint has comparatively high performance, and con be applied to long-spanned bridges. In this type buried joint, a mastic asphalt mixture is used for a binder course as a standard material, since the buried joint requires high leakless and flexible capacities on the binder course.
Use of a mastic asphalt mixture in field constructions has a disadvantage in a cost aspect, because special ingredients and expensive manufacturing equipments are necessary. In the recent Japanese situation, it is difficult to obtain a good quality ingredient, and manufacturing is impossible in some local provinces. In addition, construction and a quality control of a mastic asphalt mixture might not be easy. A new substitutable asphalt mixture is needed for the grid-panel-type buried joint.
In this situation, we have investigated several kinds of asphalt mixtures, such as fine graded HMA and open graded HMA with reinforce grouting, and have discussed which mixture is most appropriate. Based on the discussion, stone matrix asphalt (SMA) with small maximum aggregate size shall be the most promising mixture for binder course of the grid-panel-type buried joint. However, rating performance of conventional SMA mixtures is not sufficient and a mixture design procedure for SMA with small maximum aggregate size is not cleared.
The objective of this research is to select the appropriate SMA mixture for the grid-panel-type buried joint and to introduce a rational mixture design procedure for the SMA mixture. This mixture design procedure must be not only for definition of design asphalt content but also for selection of appropriate aggregate gradation. Applicability of the design procedure must be evaluated on the basis of the mixture performances.
Reference
1. Takahashi O., Maruyama T. and Inaba T. : The development of a crack prevention system for buried joints with a grid panel and sliding sheets, Cracking in Pavements, Proceedings of the Fifth International RILEM Conference, pp.89-96, 2004.5
2. Takahashi O. and Inaba M. : Reinforcement of open graded asphalt concrete with resin grouting, The 31st conference of JSCE Kanto branch, V-85, 2004.3. (in Japanese)