Which testing methods are used to evaluate the stiffness of asphalt mixtures?

The choice of Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) as the correct answer is based on their specific applications in characterizing the rheological properties of asphalt mixtures, particularly stiffness.

The DSR is instrumental in evaluating the viscoelastic properties of asphalt binders and mixtures under controlled temperature and frequency conditions. It provides crucial data regarding the stiffness of the asphalt binder, which is essential for predicting the performance of asphalt pavements, especially under varying temperature and loading conditions.

The BBR complements this evaluation by measuring the low-temperature stiffness of asphalt binders, which is vital for understanding how the material will behave in cold weather conditions. The BBR assesses the creep properties of the binder, helping to determine its susceptibility to cracking.

In contrast, the other options involve methods that either do not directly measure stiffness or focus on different properties of asphalt mixtures. For example, the Standard Proctor test and AASHTO T-99 are primarily utilized for soil compaction testing, while Marshall Mix Design and Superpave Gyratory Compactor focus on mixture design rather than stiffness evaluation. Lastly, fatigue testing and tensile strength testing do not specifically address the stiffness but rather other mechanical properties of the material. Hence