Research On Aging Characteristics Of Nano-Montmorillonite Modified Asphalt And Asphalt Mixture

It is urgent for the high-quality asphalt pavement in modern traffic with the increasing of the traffic volume and traffic load. Therefore, it is significant to improve the aging resistance of the asphalt binders in order to prolong the service life of asphalt pavements. Some researchers found out that nano-composite based on the layered silicate and polymer can effectively improve the aging resistance of the polymers. This paper aims at manufacturing nano-meter montmorillonite modified asphalt and researching the aging characteristics of nano-meter montmorillonite modified asphalt and asphalt mixtures. It also studied the influences of nano-meter montmorillonite on the pavement performances and the aging resistance of the modified asphalt and asphalt mixture. These researches provide theoretical basis for the application of the nano-meter montmorillonite modified asphalt in the asphalt pavement engineering.Firstly, this paper researched the influences of nano-meter montmorillonite on the aging properties of asphalt with three indexes and viscosity. Experiment results show that the softening point and viscosity of asphalt increases, nevertheless, both the penetrate degree and ductility of asphalt decreases when the montmorillonite content is less than three percents, which indicates that the montmorillonite can improve the properties of the asphalts at the high temperatures significantly. Investigation of aging asphalt shows that the softening point increment and VAI of asphalt are decreasing with the increasing of the content of the montmorillonite, but both the residual penetration ratio and residual ductility value are increasing. The results show that nano-meter montmorillonite modified asphalt has a better ageing resistance and the crack-resistant is better than the base asphalt.Secondly, the temperature and frequency sweep tests showed that the composite modulus of base bitumen and nano-meter montmorillonite modified bitumen were increasing and the phase angle was decreasing with the aging process. Compared to the base bitumen, nano-meter montmorillonite modified bitumen had lower complex modulus and higher rut factor when the montmorillonite content was less than three percents, which showed a good aging resistance and the high temperature stability. The hardening degree of asphalts in aging process decreased significantly when the montmorillonite content increased to five percents. Under this circumstance, it can effectively improve the low temperature crack resistance of asphalt especially at the low frequency. Thirdly, the creep loading test showed that the deformation of asphalts loaded were increasing with the increasing contents of the nano-meter montmorillonite powders.It found that the stiffness modulus of the aging asphalt decreased with the the five percents contents of the layered silicate montmorillonite, which indicates that the nano-meter montmorillonite power can effectively improve the aging resistance of the asphalts. The modulus of shear creep decreased with the increasing contents of the montmorillonite at minus ten centigrade, while at twenty centigrade it increased, which indicated that the montmorillonite can improve the low temperature crack resistance of the asphalts and the high temperature shear resistance of asphalts in the long-term ageing.Fourthly, the Marshall stability, splitting strength, water resistance and tensile or compressive strength of aged asphalt mixture sharply increased while adding three percents montmorillonite modifier. At the same temperature, the indirect tensile fracture time of asphalt mixture decreased with the increase of loading speed, while the tensile strength increased. At the same applied strain rate, the indirect tensile strength sharply decreased with the rise of the temperatures.Fifthly, it founded that the fatigue life of asphalt mixture decreased with the increasing loading stress. Meanwhile, there is a decrease in fatigue cycle numbers when the aging time continued. Both the indirect tensile modulus and the degree of aging decreased while aged asphalt mixture was modified by nano-meter montmorillonite. Experiment results show that the nano-meter montmorillonite can improve the fatigue strength of aged asphalt mixture effectively.