The reasons for the unqualified water permeability coefficient of asphalt pavement are divided into two reasons: the unqualified water permeability coefficient of newly paved asphalt pavement and the high water permeability rate of old asphalt pavement.

Causes of water seepage in newly paved asphalt pavement

1. Materials: the mix proportion of asphalt mixture is unreasonable. In the mix proportion design of asphalt mixture, the skeleton is composed of coarse aggregate with a certain particle size and a certain proportion, and the skeleton is filled with mineral powder, stone, asphalt and other materials. Appropriate porosity shall be reserved between coarse aggregates. If the porosity is too small, the coarse aggregate skeleton will be opened, or the coarse aggregate will be broken during rolling, the overall structure of asphalt mixture will be damaged, and the skid resistance of pavement will be affected. If the porosity is too large, asphalt mixture is prone to cracks, resulting in pavement water seepage.

2. Construction: water seepage caused by segregation. During the construction of asphalt pavement, each process shall be strictly controlled to reduce mixture segregation and temperature segregation and ensure the uniformity of asphalt pavement. Certain segregation will occur in the process of asphalt mixture mixing, transportation and paving. If it is not handled carefully in the construction, the paved surface will be uneven, especially in the location with more coarse aggregate, the greater the voidage of asphalt concrete, and the more serious the pavement water seepage will be.

Causes of water seepage in old asphalt pavement

1. Asphalt pavement aging: after the asphalt road is put into use, the asphalt in the mixture is affected by high-temperature thermal aging and ultraviolet aging, resulting in weak adhesion, reduced ductility, falling off from the aggregate surface, excessive porosity and water seepage. At this time, the main performance of asphalt pavement is: lean oil, whitening and fine net crack.

2. Close to service life: the wearing course of the pavement is worn, resulting in the reduction of strength and stability of the wearing course, the loss of oil volume and water seepage.