Study On The Waterproof And Cohesive Layer Of Porous Asphalt Overlay

Porous asphalt has been widely promoted in China.Waterproof and cohesive layer is an important part of porous asphalt.It consists of asphalt and gravel or asphalt only,so there are different combinations when asphalt type,gravel coverage and gravel size change.For porous asphalt,the requirement of the waterproof and cohesive layer is higher than that of common asphalt pavement.There are two reasons:first,compared with the ordinary AC pavement,the contact area between the porous asphalt layer and bearing layer is smaller,therefore the waterproof and cohesive layer must have a strong cohesiveness to ensure excellent contact between layer and layer;Secondly,the waterproof and cohesive layer should show good water resistance,so as to ensure that the lower bearing layer is not eroded by water,or it would lead to pits,water damage and other road diseases.At present,the construction specification for the waterproof and cohesive layer of porous asphalt is not available in China.Moreover,there is no standard requirement for material consumption,gravel size,and gravel distribution of it.So the waterproof and cohesive layer needs to be studied in detail.In this research,firstly,verified the necessity of study on the bond strength of pavement structure.Established a three-dimensional model of pavement structure by ABAQUS finite element software,then calculated the maximum shear stress of pavement layers under disadvantageous conditions including long and steep slope,overloading and crossroad.The results show the shear strength increases obviously under these conditions.Then studied how to develop bond strength of waterproof and cohesive layer by shear test and pull test.The research focused on both single layer porous asphalt and double-layer porous asphalt.Analyzed the influence of the following variables on the bond strength:temperature,asphalt type,gravel size and gravel coverage.Obtained several recommended waterproof and cohesive layer combinations.The water resistance of these recommended combinations were tested.And their effects of increasing bond strength were verified by constructing a test section.Finally,applied the waterproof and cohesive layer combinations when constructed porous asphalt in Jiangsu province.After construction,drilled cores from there and carried out shear test at different temperatures to study the effect of texture depth on bond strength of waterproof and cohesive layer.Summarized construction technologies,which would provide guidance for the construction of waterproof and cohesive layer of porous asphalt in the future.