Reflective cracking is a well-known weak point of semirigid pavements. It advances upward from a rigid base through the asphalt layers. Various techniques for countering reflective cracking (e. g., Stress Absorbing Membrane Interlayer (SAMI) and Stress Absorbing Membranes (SAM) membranes, geogrids) have been used. But their effect usually comes down to more or less effectively slowing the growth of cracking, not preventing it from occurring. Asphalt courses with increased crack resistance are characterized by considerable shear and tensile strength. These properties may be achieved through the appropriate selection of the gradation of an aggregate mix, the type of binder and possibly the mastic strengthening additives.
12.2.3 Test Methods for Crack Resistance
Different methods for testing crack resistance have been used, and so far there has not been one commonly regarded as the dominant standard. There are some popular methods such as the thermal stress restrained specimen testing (TSRST; discussed later), local procedures used by specific research centers (e. g., Judycki, 1990), and methods under standardization, such as the semicircular bending test (Krans et al., 1996; Molenaar and Molenaar, 2000). Test methods for asphalt binders (e. g., the BBR method) have also opened up some new possibilities. In addition, the oldest engineering method—namely, observation of test road sections—is still in use.