BITU2020 : Review of the aspects connected to changing supply of bitumen on the Finnish market in the context of performance and quality assurance of asphalt concrete

Since 2020, the International Maritime Organization (IMO) has had a sulphur
limit for ship fuel oils, which will cause changes in the crude oil market and
refinery operations. The changes will affect the quality of bitumen used as a
binder for asphalt pavements. In Finland, the amount of imported bitumen has
increased in recent years so that from 2021 onwards all the bitumen will come
from abroad.
The first part of the report describes the background to the imposition of the
IMO2020 regulation for setting a sulphur limit, as well as its possible effects, in
so far as they may have an impact on the bitumen industry. Changes in the
chemical composition of residues from the refining process can affect bitumen
products and the properties of asphalt pavements. The second part of the report
identifies methods for detecting future differences between various bitumen
products, due in particular to their chemical composition. The methods were
critically evaluated according to the fact how quickly they could be deployed in
the industry. The most promising would seem to be a separation based on
infrared spectroscopy combined with machine learning algorithms (MLAs).
The third part of the report examines the causes and possible damage
mechanisms leading to the type of damage that has been observed more and
more frequently in Finland, suggesting deficiencies in water resistance. They can
be caused by raw materials and weakness of the bonds between them, or
excessive voids content. These factors affect the cohesion of the asphalt mass
under the increasingly varied conditions; winter weather conditions are
becoming more fluctuating and demanding as the relative humidity and the
freezing-melting cycles increase.
The fourth part of the report surveys and presents laboratory methods for
assessing the water resistance of asphalt pavements; test methods previously
used in the ASTO study 1989–1991 and currently used in Europe and the USA, as
well as possible new test methods. In addition, the effects of the properties of
bitumen from various crude oil sources and the use of adhesion-promoting
additives on water resistance and studded tyre wear resistance are reviewed, in
addition to how they have been evaluated in previous studies. The results of the
ASTO study need to be reviewed in the light of current data.
The fifth part of the report reviews the implementation of the questionnaire
survey conducted during the project and analyses its results. The survey
examined the views and experiences of both those commissioning and
producing asphalt pavements regarding damage related to the water resistance
of asphalt pavements and their causes, evaluation criteria, test methods and
interpretation of their results, as well as the properties of bitumen.
As a result of the study, recommendations shall be made; as bitumen types
change and differentiate, it is worth collecting a database of the properties of
the bituminous mixtures, combined with the properties of the bitumen used in
them (chemical composition and rheological properties of fresh and aged
bitumen). A more uniform use of the water resistance tests currently in use
should be developed. In addition, it is worth exploring the potential benefits of
new methods, such as the Semi-circular Bending (SCB) and Hamburg Wheel
methods. Water resistance testing is recommended to verify the dosing of the
adhesion agents in the design of the mass. Adhesion agents can also have an
impact on studded tire wear and deformation resistance. When improving water
resistance, assessments should also include the potential effects on cold
resistance, resistance to deformation and fatigue, and the ageing properties of
bitumen.
A fast and efficient method for detecting differences in the chemical
composition of bitumen would be needed, and this will be investigated in the
second phase of the project. The purpose is to collect a database of bitumen
compositions determined by infrared spectroscopy and combine them with the
rheological properties of bitumen using machine learning methods.
In order to develop the level of know-how, it is noted that awareness of the
increase in risks should be raised. It is worth reducing the risks by testing more
frequently than the minimums required by the standards, as well as by
monitoring variations in the properties of raw materials and masses. It is
recommended that the standards, guidelines and quality requirements be more
clearly combined.