Rheology and stability of bitumen/EVA blends

Rheological measurements reveal that the viscoelastic properties of a 60/70 penetration grade bitumen are improved when either a virgin EVA or a recycled EVA copolymer of similar vinyl acetate content are mixed with it. Risk of cracking at low temperatures and rutting at high temperatures, are both reduced. Better viscoelastic features are obtained with the bitumen modified with recycled EVA, probably due to the presence of carbon black, which acts like a filler in this material. Stability tests performed combining oscillatory flow and microscopy results disclose that blends with the higher polymer proportion (3%) are susceptible of phase separation after 24 h of storage at 165 degreesC, but 1% blends are stable for at least 4 days. A general evaluation of the results indicates that the performance of this bitumen as a binder for road pavement, is particularly improved when 1% of recycled EVA or virgin EVA is added. (C) 2004 Elsevier Ltd. All rights reserved.