In the laboratory two procedures are used to investigate asphalt mixtures: short term ageing and long term ageing. STA (Short Term Ageing): The loose mixture was spread on a tray of a 600 cm2 area. The mixture was heated for 4 hours at a temperature of 135 degrees centigrade, and stirred at 1-hour intervals. After 4 hours the mixture was brought to the temperature required for compaction and the Marshall specimen prepared. In the laboratory, asphalt mixtures were produced with a mineral aggregate and different binders. Some standard bitumens were used: modified binders and natural asphalts. Beside these laboratory-mixtures, mixtures of plants were also tested. The volumetric values of the aged and unaged of the aged and unaged Marshall-specimen were compared. Differences in e.g air void are the consequence of change in binder properties. The proportion of the viscosity at 135 degrees centigrade is an expressive value. The results demonstrate, that the STA-Test is a very good method to predict the asphalt behaviour in service due to construction effects. LTA (Long Term Ageing): At this simple oven ageing procedure the Marshall-specimen were heated at 85 degrees centigrade during days (48 hours). After the two days the specimen were stored at room temperature for one day. The behaviour was investigated with an unaxial compression test in which the energy was evaluated and the deformation modulus was determined. In this case only asphalt mixtures of different plants were used. The compression test was carried out at temperatures of +50 degrees centigrade, +30 degrees centigrade, +10 degrees centigrade and -20 degrees centigrade. The deformation modulus of the agedand unaged Marshall-specimen was compared. The results show changes in the asphalt properties. But it is not certain, that it is possible to predict with this LTA-method the oxidation effects in place. Therefore the efforts this Spring will be directed to further studies of this LTA-method.
Abstract