Effect of wax on basic and rheological properties of bitumen with similar Penetration-grades

This paper presents the results of a study on the wax content, the basic and rheological properties of seven unmodified bitumens with Penetration-grades 60–70 and the effect of wax on these bitumens. Among the bitumens, one (currently used in Hong Kong) was supplied by a manufacturer in Singapore while the other six bitumens were obtained from manufacturers in Mainland China. The results of the basic tests show that all bitumens are Penetration-grade 60–70 and have similar basic properties. The test results comply with the Hong Kong bitumen specification. However, the wax contents of some of the bitumens manufactured from crude oil deposited in China are relatively high. The test results obtained by the dynamic shear rheometer further indicate that the bitumens with low wax content performed better than those with high wax content under a high temperature environment. The test results exhibit relatively good correlation between the wax contents and the rheological properties of the bitumens. Therefore, standards and procedures should be established in Hong Kong to specify requirements on wax content or Performance-grade for bitumen used in road paving.