The National Center for Asphalt Technology says whether the asphalt manufacturing process for ground tyre rubber powder is cryogenic or ambient, it does not impact the performance of the rubber material or, ultimately, the asphalt. This is based on study findings the US centre has undertaken and which it expects will accelerate the use of sustainable material in highway construction. The centre also says that by increasing the use of ground tyre rubber, asphalt producers will benefit from price stability as compared to more volatile oil prices which impact the cost of traditional, oil-based polymers. Importantly, ground tyre rubber produced cryogenically or ambiently provides high performance and cost benefits in asphalt. In recent years, as oil prices have risen, the number of states reassessing the potential of GTR mixtures has begun to increase; however, little research has been published which characterises the influence of particle size, grinding technique and blending methodology. The NCAT study addressed these needs and indicates that surface area and particle size of the rubbers had the most influence on the modified asphalt binder – smaller particle size, which equates to larger surface area, provides better performance. (RJA)