improvements in asphalt properties have been achieved by selecting the proper
starting crude, or tailoring the refinery processes used to make asphalt.
Unfortunately, there are only a few crudes that can produce very good asphalts,
and only a limited number of actions that can be taken to control the refining
process to make improved asphalts. The next step taken by the industry was to modify
the asphalt. Air blowing makes asphalt harder. Diluent oils are sometimes used
to soften the asphalt. Another method that can significantly improve asphalt
quality is the addition of polymers.
Modified bitumen is a type of asphalt
product that can be applied in a number of ways to the roof in both hot and
cold temperatures. Modified bitumen roofs have a lot of advantages including
flexibility, energy efficiency over other types of membrane roofing, and are
often seen as the modern alternative to the built up roof. The modified binder are more stable under heavy loads, accelerating forces and shows increased
resistance to permanent deformation in hot weather. It resists fatigue loads
and having better adhesion between aggregates and binders. There are two type
of modified bitumen. There
are many modifier materials that can be used to mix with bitumen to improve
their performance as paving material. Rubbers are preferred as bitumen modifier
due to their lower prices and the availability however, the viscosity increased
significantly by modification with rubber. Nevertheless, the selection of
modifier is depending on the user or company.