Construction of four-lane and six-lane national highways under the National Highway Development Program has been taken up in a massive way. Several stretches of asphalt pavements constructed under this program have already been opened to traffic. Premature surface cracks were observed on some stretches within a year or two of construction and these cracks were found to initiate from top and progress downwards which is generally known as top-down cracking. In the present study, an effort was made to examine the causes of the top-down cracking susceptibility of asphalt layers. Temperature gradients of typical asphalt layers were measured in the field as well as in the laboratory under high pavement temperature condition. Finite element analysis of typical asphalt pavements was carried out for the evaluation of the influence of high pavement temperature on surface tensile strains in the asphalt layer. The effect of heavy axle loads in combination with high pavement temperatures was analyzed for the evaluation of initiation of surface cracking. Surface traction forces developed during rolling and braking were also considered. Parametric analytical studies indicated that temperature was a critical parameter influencing the top-down cracking susceptibility of asphalt layer, especially in combination with heavy axle loading.
Samenvatting