Performance of modified asphalt binder and mixtures under increased truck loading limits

In many developing countries the truck loading limits are not well enforced. It is also an economic challenge to enforce truck loading limits when demand for rapid construction and limited transportation facilities are available. Design of asphalt mixtures to resist the higher loads carried by trucks is a real challenge. The information regarding sensitivity of asphalt binders and mixtures to high stresses is scares. This study is a laboratory investigation for the response of selected asphalt binders and mixtures to increased stresses under repeated loading at pavement temperatures in the range of warm climates, such as the climate in the Gulf area. Advanced testing procedures including the Dynamic Shear Rheomter for binders and the Simple Performance Testing Device for mixtures was used to compare basic rheological behavior under repeated loading. The loading levels were varied within a wide range and the deformation was analyzed in terms of recoverable and permanent. The results clearly show that the asphalt binders plays a major role in the non-linear stress dependency of mixtures. The effect of modification type is also found to affect performance. A discursion of the need for considering and modeling of stress dependency of permanent deformation is presented. The paper points out the need to simulate actual loading ranges in testing of paving materials and the possible errors that could result from underestimating loads or using Linear Visco-elastic properties to characterize asphalt binders and mixtures.