04

Pen corrector

Pen Corrector

General use

For designing asphalt mixes and road constructions we need certain behavioral characteristics in order to predict the desired thickness. This is related to traffic load and desired lifetime. The stiffness and resilience of the used bitumen are responsible for the behavioral characteristics in the asphalt mixes. In 1935 we introduced the penetration and penetration index of bitumen to classify and control the predictable behaviour in designing calculations. This method has worked for all these years, and has brought designing properties and behaviour in practice together. Worldwide there is no designing method that works without penetration and penetration index levels. For the past 80 years penetration and penetration index classification has brought bitumen and asphalt mixes into reliable use, and has been responsible for predictable lifetimes.

Soft bitumen (high penetration)  caused roads with lower resistance to heavy truckloads, but a high resistance to cracks and rutting. Hard bitumen, with a lower penetration, caused the opposite, with high performance (not deforming) to heavy truckloads, but a more brittle behaviour leading to earlier cracks, rutting and end of lifetime. Most countries developed regulations with specified penetration usage in different specified road areas. The higher the traffic consumption in terms of truckloads and quantity, the lower the penetration grade of the bitumen.

In the past 80 years the most important influence of designing asphalt constructions has been experience with penetration grades. But nowadays, the original design methods are facing effects of high recycling amounts, very little usage of fresh bitumen in asphalt and other chemical compositions (SARA) due to use of cracking technologies. The reliability of bitumen and asphalt behaviour by penetration values no longer makes sense, and instability in performance has been observed. For this reason modern, recently produced, bitumen and asphalt mixes need an addition to bring back the performance observed during the previous 80 years experience. The ultimate goal is to ensure that the quality of the end product (the mix between old and new bitumen) maintains at least the same characteristics as the bitumen that we have known for the past decades.

Thanks to the use of an Penetration Corrector (Rheofalt HP-AM)) it is possible to restore fresh bitumen, or the mix between old and new bitumen in recycling mixes, back to defined and precalculated penetration values. Years of research have clearly demonstrated the connection between chemical and physical ageing. The polarity of the asphaltene and the possibility of agglomeration is the main cause for the stiffening of bitumen in the long term.  All the more reason to examine how this agglomeration of the polar asphaltenes can be delayed or prevented. The production of hundreds of thousands of tons of asphalt has demonstrated that RheoFalt HP-AM binds to the asphaltenes and subsequently stabilises them.  This means that even though in principle bitumen has a higher share of asphaltene, the agglomeration, which leads to brittleness, is far slower over the course of 20 years. RheoFalt HP-AM compensates for the accelerated decline of the mixture characteristics.

Whereas in the past, aged bitumen with a high level of asphaltene was mixed with lighter components, it now turns out that managing the stabilisation of the polar share in the bitumen generates a much greater effect over time. This science is new because until now only the physical component of the asphaltenes was studied, while the long-term behaviour of the asphaltenes was ignored.

In practice, production during the past ten years shows a linear correlation between the penetration of bitumen and the percentage of RheoFalt HP-AM. This means that the design of the road’s rigidness can be managed by means of the penetration value of the bitumen in the end mix (LogPen Mix).

Back to overview