Gb5® high modulus asphalt

Abstract

With ever increasing volumes of traffic on South African roads, and particular that of heavy vehicles, the road building industry has recognized the need for specialised asphalt mixes to address the rutting and fatigue problems experienced currently. GB5 is a cost effective asphalt base mix, designed for high performance and long life, similar to stiff grade bitumen mixes (EME’s). This mix can be produced with most of the aggregate and bitumen road grade types available in South Africa that is currently being used in the production of hot mix asphalt. Usage of this mix will allow for reduced pavement thickness, increased longevity and decreased rutting. The GB5 alternative controls the volumetric properties by optimizing the combination of fine and coarse aggregates, resulting in an interactive network of particles in the mix to obtain a high stiffness modulus; at the same time uses modified bitumen, instead of high binder contents to obtain good fatigue properties. GB5 has already proven itself in France, where it was developed, under heavy traffic (more than 500 000 tons paved) where legal axle loading limits are significantly higher than those in South Africa. The extensive trials done in eThekwini Metro in KZN have shown that the GB5 technology has now successfully been transferred to South Africa.