Assessment of Gilsonite and Trinidad Epuré natural asphaltmodified binders ability to relaxation at low temperature

摘要

The paper presents the results of the tests conducted on asphalt binders modified with additives of natural Gilsonite and Trinidad Epuré asphalts, as well as the 20/30, 35/50 and 50/70 penetration grade bitumens by use of an original observation method of the relaxation phenomenon in low temperature. In the tests the authors used a ductilometer equipped with a dynamometer and a bath filled up with a liquid with the temperature of-16°C. Relaxation of the asphalt binder was observed in the period of 20 minutes in the conditions of constant deformation of the sample caused by its prior extension with the constant speed of 1 mm/min. The value of the normal stress occurring in the asphalt binder is calculated on the basis of the measured value of the normal (tensile) force. It has been noted that asphalt binders with higher penetration values are characterised by a better relaxation ability at low temperature, that is relaxation takes place faster and has higher values of sample stress reduction in the domain of time, at constant strain. With approximate penetration values (the maximum penetration difference at 25°C amounting to ±2 mm/10), modified binders comprising Gilsonite are characterised by better relaxation abilities in comparison to binders containing the Trinidad Epuré additive.