# Bitumen and Bitumen Modification: A Review on Latest Advances
## 1 Introduction  
### Bitumen Functionality  
According to the European specification (EN 12597), bitumen is defined as a virtually involatile, adhesive, and waterproofing material derived from crude oil, or present in natural asphalt, which is completely or nearly completely soluble in toluene, and very viscous or nearly solid at ambient temperatures [1]. It is well-accepted that the original characteristics of bitumen are highly dependent on its production and processing procedure, as well as bitumen crude oil characteristics [2]. Good crude oils and proper distillation processes can enhance bitumen properties. Generally, heavier crude oil gives higher bitumen yields [3]. Therefore, having a complete knowledge on the bitumen characteristics from different aspects is of paramount importance. This knowledge proves to be more important when, for some bitumen applications, some difficulties such as discontinuity in phase, mal-dispersion, and instability with polymers/additives make it challenging in the production and application of bituminous materials.  
From a commercial point of view bitumen is a low-cost thermoplastic material that has been widely used in roofing and pavement application, paving mixtures, and industrial products for a long time. In both paving and industrial applications, the bitumen should be resistant to climate and more demanding traffic loads, for which reason rheological properties play a key role in different aspects [4; 5; 6]. From a functional point of view, the bitumen has to be fluid enough at high temperature (\(\approx\)160 \({}^{\circ}\)C) to be pumpable and workable to allow for a homogeneous coating of aggregate upon mixing. Moreover, it has to be stiff enough at high temperatures to resist rutting (according to the local temperatures, \(\approx\)60 \({}^{\circ}\)C). Finally, it must remain soft and elastic enough at low temperatures to resist thermal cracking [4]. All the mentioned requirements are almost opposite, and most of the available neat bitumens would not provide all the needed characteristics together. Moreover, in some applications, the performance of conventional neat bitumens may not be satisfactory considering the required engineering properties because it is brittle in a cold environment and softens readily in a warm environment. This limited performance temperature range is the main drawback to neat bitumen, limiting its use for both roofing and road paving applications. In addition, as the traffic speed and load has dramatically increased, unplanned overloading has notably shortened the life of asphalt pavements, increasing its costs of maintenance and risks to users. Hence in order to enhance the performance properties of neat bitumen, to date, a variety of additives have been introduced and some have been used successfully for many applications. Modifiers and additives have been used to boost bitumen performance include: polymers, chemical modifiers, extenders, oxidants and antioxidants, hydrocarbons, and anti-stripping additives. The following sections are dedicated to the discussion about bitumen chemistry composition in order to describe the main features and mainly to describe the additives used over the last few decades of research, providing a comprehensive and in-depth coverage of the science and technology of bitumen modifiers.