Explain the Marshall method of asphalt mix design.

Marshall method designs asphalt mix through: (1) Aggregate gradation selection meeting specification bands, (2) Prepare specimens at various asphalt contents (typically 4-6%), (3) Test specimens for stability (maximum load at 60C) and flow (deformation at max load), (4) Calculate volumetric properties - air voids, VMA (voids in mineral aggregate), VFA (voids filled with asphalt), (5) Select optimum asphalt content meeting all criteria (usually 4% air voids with acceptable stability, flow, VMA, VFA). Superpave has largely replaced Marshall for higher traffic roads.