Abstract
Insufficient shear performance in an asphalt mixture is a primary reason for rutting deformation and pavement surface longitudinal cracking. Thus, it is important to choose a suitable shear test method to evaluate shear performance in an asphalt mixture. Current testing methods mainly evaluate the bonding strength between asphalt layers, and the current shear test method for an asphalt mixture is disadvantaged by high equipment cost and complicated procedures. Our study proposes a torsional test method under normal stress condition, and evaluation was done for four types of asphalt mixture under different temperature conditions. Through the mechanical analysis, the calculation formulas for shear strength and shear parameters (cohesion and internal friction angle) for the torsional test under a normal stress condition were obtained. Testing results were also obtained for shear strength, shear modulus, and cohesion and internal friction angle of the asphalt mixtures. Experimental testing indicated that the method was able to provide repeatable results for the shear resistance of asphalt mixtures at different temperatures and also reflected the difference in shear performance of the various asphalt mixtures and the influence of temperature on shear performance. The failure mode of the specimen was the appearance of an oblique crack of about 45° from the vertical axis after the specimen was destroyed, which accorded with shear failure characteristics. A shear fatigue model was obtained considering different shear stress levels. The torsional test method under normal stress formed a compression‐shear action on the specimen by applying torque and normal stress and was used to evaluate the shear performance of the asphalt mixtures.
Highlights
With the rapid growth of traffic volume and the continuous development of heavy-duty transportation in China, various damages have occurred to asphalt pavement on expressway and trunk highway
Four asphalt mixtures were selected for torsional testing under normal stress condition at different temperature conditions. e following conclusions can be summarized from this study and laboratory investigation: (i) During the torsional test, the height and the volume of the specimen were kept basically constant, which ensured the accuracy and reliability of the shear test results
(iii) rough mechanical analysis, the calculation formulas for shear strength and shear parameters of the torsional test under normal stress condition were obtained
Summary
With the rapid growth of traffic volume and the continuous development of heavy-duty transportation in China, various damages have occurred to asphalt pavement on expressway and trunk highway. Permanent deformation (rutting) and pavement surface longitudinal cracking are the two main forms of asphalt pavement damage currently seen in China. Permanent deformation (rutting) is a surface depression in wheel paths caused by repeated loading due to heavy traffic loading that causes a progressive accumulation of permanent deformation under repetitive tire pressure. Is densification of materials was generally caused by excessive air voids or inadequate compaction of pavement layers. More severe premature distortion and rutting failures were related to lateral movements or a plastic flow of materials from wheel loads upon asphalt layers with inadequate shear strength and/or due to large shear stress states from traffic loads. Results of trenching studies from the American Association of State Highway Officials (AASHO) Road Test as well as other test tracks indicated that shear deformation rather than densification was the primary permanent deformation mechanism [1,2,3]
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