Analysis of the effect of wax content on bitumen under performance grade classification

This paper describes an analysis of the effect of wax content on bitumen under performance grade (PG) classification. Wax content affects the performance and rheological behavior of bitumen. Bituminous mixtures with bitumen of high wax content tend to become very soft at high temperatures leading to rutting problem on pavement. Also the rheological behavior of bitumen has a great influence on the behavior of bituminous mixtures. To address the potential adverse effect of wax on bitumen, countries in Europe limit the wax content to 2.2% (BS EN 12606-1). In Mainland China, the standard (JTG F40-2004) classifies bitumen into three grades (Grades A, B and C). Grade A, with wax content below 2.2%, is used for highway pavement construction. Grades B and C, with wax content limits of 3.0% and 4.5% respectively, can only be used on roads with relatively lower traffic. The current binder specifications in Hong Kong Special Administration Region is based on penetration testing, which does not properly account for pavement performance. This paper assesses the effects of wax content and the rheological properties of seven types of bitumens and provides the basis for a performance grading binder standard for Hong Kong