True or False: Stone matrix asphalt (SMA) is defined by its gap grading and use of modified asphalt binders.

Stone matrix asphalt (SMA) is accurately defined by its gap grading and the use of modified asphalt binders. Gap grading refers to the intentional exclusion of certain aggregate sizes, which creates voids in the mix. This design helps to enhance the durability and resistance to deformation under loads, making SMA particularly effective in high-stress areas such as heavy traffic zones. The inclusion of modified asphalt binders further enhances the performance characteristics of SMA, offering improved resistance to rutting and moisture, along with better fatigue resistance.

The combination of these elements contributes to the overall effectiveness of SMA in providing a durable and high-performing pavement solution. This definition is widely accepted within the field, confirming the accuracy of the statement regarding SMA’s characteristics.