Chemical and Oxidative Controlled Hardening of Epoxy-Modified Bitumen

The addition of epoxy modifier in bitumen is a relatively new modification technology (1-4) and the most critical epoxy polymerization-induced changes of the epoxy-bituminous materials are not fully understood. Different phenomena take place when epoxy modifiers are incorporated into bitumen and they are dependent on the material hardening conditions. Temperature is one of the most crucial parameters that influences to the development of physical, chemical and mechanical characteristics at the early life (curing or chemical hardening - CH) (5-7) and long-term service (oxidative hardening - OH) (4) of epoxy-modified binders. For this reason, in-depth exploration of epoxy chemistry in bitumen is needed to understand the evolution of the properties of these binders in time. Within this framework, the chemical compounds and their reaction products generated under various conditions were studied to reveal the time dependency of molecular microstructures of modified binders. Special attention was given to the evaluation of physiochemical characteristics and the mechanical properties of epoxy-bituminous binders, concluding that the degree of CH and OH was dependent on the level of epoxy modification in bitumen. It was observed that the sulfoxide compounds are the most representative index for assessing the age hardening of epoxy-modified bitumens. Finally, the enhanced resistance against environmental aging in combination with the superior mechanical characteristics (i.e., higher tensile strength, flexibility and enhanced longevity) when the epoxy modification is implemented in bitumen promises a very effective technology for developing long-lasting pavement materials.