抄録
The present authors have reported in another paper about the glass transition phenomena and rheological properties of asphalt in a very wide range of asphaltene content. According to them, asphalt exhibits glass transition temperature Tg, which varies with asphaltene content from -40 to 10°C. Creep test has revealed that, above Tg, asphalt shows retarded elasticity as well as viscosity. Furthermore, the temperature dependence of the steady flow viscosity and retardation times obey Williams-Landel-Ferry's equation, the standard temperature TS involved in this equation being 56°C higher than Tg for each epecimen.
In this paper, physical interpretation of the penetration test and softening point test of asphalt is presented on the basis of these rheological results. The penetration, when measured at 25°C in 5 or 60 seconds (JIS K 2530), is not necessarily a measure of viscosity alone, but influenced by elasticity also. In the case of asphalt of high asphltene content, the penetration consists mostly of elastic deformation and is scarcely influenced by viscosity
A simple theory on the “Ring & Ball” softening point test is developed. The theory predicts that the softening temperature Tb should correspond to the temperature at which the viscosity of test material reaches a definite value, and log η(TS) (viscosity at TS) should be linearly dependent on (Tb-TS). The viscosity at Tb is predicted to be 2.5×104 poises from the dimensions of the routine test instrument (JIS K 2531). These predictions are very satisfactorily proved by experi-mental results.
