Stone mastic asphalt, or SMA, was developed in Germany in the 1960’s to provide a more hard wearing surface layer for roads, highways, highly trafficked car parks and other commercial areas.
Stone mastic asphalt consists of a high content of coarse aggregate (70% – 80%) which interlocks, and is filled with a mastic mixture containing bitumen (6% – 7%), filler (10%) and fibres (less than 1%). The high content of aggregate creates a greater stone on stone contact than bitmac to provide a more stable and durable finished surface than tarmacadam, which resists deformation.