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Properties Comparison of Asphalt Cement and Multigrade Asphalt in Asphalt Concrete.
Kosintra Jetiyanonta and Watcharin Witayakul

ABSTRACT The engineering properties of multigrade asphalt compared with asphalt cement grade 60/70 were investigated and the performance of asphalt concrete was mixed between both binding materials and limestones. The results showed that the engineering propertiesof multigrade asphalt did not pass the specifications of Department of Highways. Multigrade asphalt had more sensitivity of penetration index than asphalt cement grade 60/70, and provided flexible performance after torsion, rheological behavior and torsional recovery better than asphalt cement, but had less ductility than that of asphalt cement. Additionally, the performance of asphalt concretemixed with multigrade asphalt gave higher stability, flow and ratio of stability and flow than those mixed with asphalt cement grade 60/70. After compaction test, the samples mixed with multigrade asphalt gave higher tensile strength and modulus of elasticity than those mixed with asphalt cement grade 60/70 but had lower poisson’s ratio. Asphalt concrete mixed with multigrade asphalt also had greaterstrength index value and smaller rutting. Therefore, multigrade asphalt may be one of the alternative binders used for asphalt concrete design in highway construction if it had been notified of such use. Key word : asphalt, multigrade asphalt, multigrade asphalt concrete

INTRODUCTION Currently, the road surface made from asphalt concrete has been faced with the problem of having more trafficeach year due to the increase in loaded trucks and passenger vehicles. These could deform the road and causing the road’s cracking and slipping off from the surface resulting in shorten of the road capacity. The progress of technology and production, leads to the development and improvement of several binding materials such as polymer modified asphalt, stone mastic asphalt, and multigade asphalt.These binding materials have more resistant to deformation and erosion causing from temperature and more traffic. Multigade asphalt is produced by special

refinery processes to provide more structure to the product and enhance the engineering performance, without the addition of polymers. This manufacturing modified the bitumen characteristics in order that the final product presents an improvedstiffness modulus, visco-elastic and adhesive. It has a quality as binding material similar to asphalt cement. Nicholls (1994) tested the road trials by using hot mix constituting of multigrade asphalt comparing with conventional binder and polymer modified asphalt. He found that hot mix having polymer-modified asphalt had deformation resistance and durability better than multigrade asphalt andconventional binder, respectively.

Department of Civil Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand.

Australian Road Research Board (1999) investigated multigrade and regulated the Australian road’s standard for multigrade use as AS 2008 and AS2341. The objectives of this research were to 1) study the physical properties of multigrade comparing withasphalt cement grade 60/70 and 2) investigate the properties of asphalt concrete mixed with either multigrade or asphalt cement grade 60/ 70 compacted by Marshall method and gyratory compactor by comparing the strength index, tensile properties, and rutting. Results from this study may indicate the possible asphalt concrete properties used in the future. MATERIALS AND METHODS Experiment 1 was tocompare the physical properties of multigrade asphalt and asphalt cement grade 60/70. The experiment was conducted as Asphalt Institute (1984), AASHTO (1992) and ASTM (1981) involving penetration, softening point; ring and ball, penetration index, ductility, torsional recovery, flash point; cleveland open cup, solubility in trichloroethylene, loss on heating, absolute viscosity, kinematic viscosity,...