Impact Of Freeze-thaw Cycles On The Performance Of Asphalt Mixtures

With development of economy, road traffic is also undergoing tremendous changes. Most of the highways are asphalt concrete pavement because of the following characteristics:low noise, low fuel consumption, low vehicle wear and tear, friction performance and high skid resistance. But as the increase in traffic and traffic load, high performance requirements are made to asphalt concrete especially with the technologies of deicing and snow-melting. The process of deicing and snow-melting will speed up the freeze-thaw cycles. With the process of repeated freezing and thawing, direct connection strength of the asphalt and the skeleton structure and the stability of asphalt concrete structure will decrease. The road will break when the external loading has come to a certain amount. Therefore, it is necessary to study the influence of freeze-thaw cycles to the performance of asphalt concrete.The multiform samples were prepared under laboratory experiment, one or more contracted freeze-thaw cycles had been acted on those samples.First the influence of accelerating freezing and thawing was evaluated for the volume property and resistance capacity to water damage of asphalt concrete. The results showed that accelerating freezing and thawing will have a great effect on the air void of Marshall Specimen, and the effect will be different with different initial air void. The mass loss rate of specimen will decrease first and then increase. Accelerating freezing and thawing will have a great effect on splitting strength and freeze-thaw splitting intensity ratio, and the effect will different with different initial air void. The addition of lime can effectively enhance the performance of concrete resistance to water damage. The properties of samples which are not mixed with lime will decrease to 85% of blank samples' after accelerating freezing and thawing for 2 or 3 times, while the properties of samples which are mixed with lime will decrease to 85% of blank samples'after accelerating freezing and thawing for 5 times.Then the influence of accelerating freezing and thawing on the high temperature stability and low temperature frost resistance of asphalt concrete was evaluated. The results showed that a rapid freezing and thawing will have a great influence on the high temperature stability of specimens, and the properties of specimens will decrease at least 50% after accelerating freezing and thawing for 2 times. A rapid freezing and thawing will also have a great influence on the low temperature frost resistance of specimens. The properties of specimens will decrease to at most 80% of blank specimens'after accelerating freezing and thawing for 2 times. But the addition of lime can effectively enhance the performance of concrete frost resistance to low temperature, and the properties of specimens which were added with lime were remain 80% of blank specimens'after accelerating freezing and thawing for 3 times.Finally, the influences of fatigue performance of asphalt concrete were evaluated by the accelerated freezing and thawing. The fatigue performances of asphalt concrete were evaluated by the Indirect tensile fatigue tests under the influence of freeze-thaw cycles. The results showed that the fatigue life of asphalt mixtures increased with the loading force decreases in the case of constant loading force, and the influence of freeze-thaw cycles on the life of asphalt mixture is very large, the fatigue life was reduced to 75% after 2 cycles.