Experimental Study On Resistance To Moisture Damage Of Asphalt Mixture

Moisture damage is one of the main early damaging form of asphalt pavement. Studies have shown that under the repeated action of vehicle load, the water inside the pore of asphalt mixture will produce dynamic water pressure and vacuum negative pressure suction effect, which is an essential condition of moisture damage. The existing evaluation methods of asphalt mixture water stability in current specification, such as immersing Marshall test and freeze-thaw splitting test, can not simulate the flushing and destroying process of asphalt mixture, thus can not accurately reflect the moisture damage of the asphalt mixture. Therefore, how to simulate the dynamic water flushing process of asphalt mixture, has become a hot spot in the field of road engineering, many scholars have conducted a lot of researchs about this.This paper has done the following research:(1) The current researching situation of moisture damage of asphalt mixture is summarized, and the existing problems are raised.(2) The field test of asphalt pavement dynamic water pressure is did. The hydrodynamic pressure inside the road under the effect of the vehicle is measured by water pressure sensor. The dynamic water pressure is analyzed, the results show that with the increase of the depth of pavement, the water pressure decreases, but not too much, and max hydrodynamic pressure delays. With the increase of the speed, the water pressure increases, but not too much.(3) Using ABAQUS software, the hydrodynamic pressure inside the road under the effect of the vehicle is calculated, and the calculated and the actual pressure is compared. The results show that the calculated hydrodynamic pressure is basically consistent with the measured hydrodynamic pressure in variation. With the increase of the speed, the water pressure increases, and the speed mainly affects the hydrodynamic pressure of the surface and to a less extent on internal hydrodynamic pressure. With the increase of the depth of pavement, the water pressure decreases, and it changes significantly.(4) A new method of evaluating water stability of asphalt mixture is introduced. By using hydrodynamic pressure generator and triaxial apparatus, the dynamic water flushing process of asphalt mixture is simulated. We choose flushing time, temperature and axial pressure to be factors and conduct orthogonal test of three factors and three levels. Also, we conduct indoor dynamic water flushing test. By determining unconfined compressive strength of specimen before and after scouring, and analysising the range and variance, we find the main factor and the secondary factors affecting dynamic water flushing damage level of asphalt mixture. On the basis, On this basis, we select the temperature of 35 degrees, axial pressure 500kPa to do dynamic water flushing test and obtain the variation of the residue unconfined compressive strength and porosity under different flushing time.