Papers by Author: Guo Jun Zhu

Abstract: The effects of aging on the fatigue property of polymer modified asphalt mixtures are investigated in this paper. Two kinds of aging procedures are adopted for the aging of specimens prepared with polymer modified asphalt mixtures. One is the short-time aging which means that the hot asphalt mixtures was heated in the oven for 4 hours at 135°C before compacted; The other called natural aging, with the original specimen exposed in the sunlight and subjected to the rain and temperature change for 3, 6 and 9 months. Four-Point Bending Test was conducted to evaluate fatigue properties of aged asphalt mixtures at 15°C compared with the original specimens. Test results indicate that the fatigue line of aged specimens have the same tendency as the original asphalt mixtures. However, the life of aged specimen is decreased significantly when compared with the original ones, especially of the natural aged specimens.

Abstract: According to three-point bending test, this paper explores the influence of low temperature on the flexural strength, the tensile strain and bending stiffness modulus of the aged Stone Mastic Asphalt (SMA-13) concrete. The asphalt mixtures are aged according to the short-term aging (at 135°C, 4 hours), and long-term aging (asphalt concrete at 85°C, 120 hours) and natural aging (3 months, 6 months and 9 months). The result shows that, with the same loading rate, the tensile strain of specimens at -30°C are smaller than those at -10°C; but when temperature is certain, the tensile strain of specimens lager than those of aged specimens. The longer the aging time lasts, the more flexural strength differences between high and low temperatures can be found. A pretty well index variation can be found between the tensile strain and temperature. The same trend also appears between the bending stiffness modulus and temperature of SMA-13 asphalt concrete.

Abstract: Asphalt ageing induced by heat, oxidation and ultraviolet (UV) radiation was investigated using various laboratory simulation ageing methods and outdoor ageing. One normal 70 penetration asphalt and its styrene-butadiene-styrene (SBS) modified asphalt were employed to assess the changes in chemical and rheological properties by infrared spectroscopy and dynamic shear rheometer under various ageing conditions, thus the relationship among rolling thin-film oven(RTFO), pressurized ageing vessel (PAV) and UV radiation ageing was distinguished. Experimental results showed that photodegradation caused by outdoor exposure UV ageing of 50~200µm thin films for a month, was found to be the most severe, following by PAV and then RTFO with respects to rehological and chemical changes. Photodegradation effect decreased as the thickness of asphalt film increases. Dynamic shear tests indicated that polymer networks were gradually destroyed during ageing, but the aged SBS modified asphalts still displayed better rheological properties than the corresponding base asphalt. The weight percent of oxygen as carbonyl increased and of SBS as butadiene decreased after ageing based on infrared spectrums. However, chemical and rheological changes were not generally consistent, and ageing susceptibility may be ranked differently when different evaluation methods were used.