Effect of Construction Cracks on the Tensile and Bond Strength of Asphalt Pavements

Traffic loads and environmental (climate) conditions are among the most important variables governing the long-term performance of asphalt pavement developed by pavement designers. Several studies done at Carleton University indicate that construction methods can also affect the long-term performance of asphalt pavement by creating hairline surface cracks that allow water to penetrate the asphalt layer. This reduces the tensile strength of the asphalt layer and destroys the bonds in the asphalt between pavement layers. This paper presents the results and major findings of an experimental investigation performed on large-scale asphalt slabs that were extracted from newly laid pavement from an actual highway project. The laboratory work included testing the slabs under direct tensile stress and subjecting them to temperatures ranging from room temperature ($+20°\mathrm{C}$) to $-20°\mathrm{C}$. The testing included one hundred nineteen $300\times 100\mathrm{mm}$ asphalt samples, with thicknesses of 50 mm for single layer and 100 mm for double layer. The research also included evaluating the bonds between asphalt layers built in the field for what the authors believe is the first time. The results showed that construction-induced cracks affect the tensile strength of new asphalt roads and can weaken the bond between the upper and lower layers when overlays are constructed. Statistical analysis confirmed that the differences observed in the results are significant.