Influence of waxes on bitumen & Asphalt
Natural wax is part of practically all bitumen and may in different ways affect bitumen properties. it refers to all found in organic substances that crystallize on cooling and melt on heating. Wax practically exists in all types of Bitumen and in many ways, affects Bitumen properties. The structure of wax is on crude oil and depends on how Bitumen is generally manufactured.
Natural wax in bitumen may influence binder properties to a larger or minor extent. In some cases, such an influence may give rise to negative effects, like increased sensitivity to cracking or plastic deformation in asphalt concrete pavements. In other cases, the wax may show positive effects on bitumen, such as increased stiffness at higher temperatures, leading to improved resistance to rutting.
Different methods for determining wax contents give different values for the same bitumen, which is one reason concerning the effects of wax on bitumen properties that have varied so much.
Bitumen produced from the Middle East crude oil has low to medium wax content. The countries in Europe limit the wax content to 2.2%.
In China, the standard classifies bitumen into three grades (A, B& 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.
However, the wax content of Bitumen is not directly related to its performance in pavement materials and routine test methods are not able to provide information related to the rheological properties of Bitumen under different loading, loading time, and thermal conditions.