Bitumen data collection project: review and findings

A variety of traditional and new test methods are used for the technical classification and assessment of different types of bitumen and bituminous binders at assorted temperatures. When the product standards for bitumens are under revision, most recently the specification for polymer modified bitumens, Eurobitume provided expert input recommending the appropriate incorporation of new assessment methods.

To help Eurobitume member companies determine what will be the likely testing requirements for future binder specifications, so they can efficiently incorporate the implications into their forward plans, Eurobitume’s Technical Committee organised and ran a large-scale data collection and analysis project in conjunction with member companies.

This project also provided a valuable opportunity for the Technical Committee to review the validity of previously agreed Eurobitume positions on certain specifications and test methods, and thus to update the framework of tests methods for future development.

Working with member companies to collect anonymised data sets

Over a period of time, each participating Eurobitume member company tested a cross-section of their binders using appropriate test methods, particularly those which are discussed for potential inclusion in future specifications.

The data was collated by Eurobitume and ended up as a significant, anonymised database comprising 172 data sets covering paving grade bitumen (99), hard paving grade bitumen (13) and polymer modified bitumen, PMB, (60).

Based on all data, the results from each test and calculation method - particularly those expected to be implemented in future specifications - were then carefully evaluated and analysed by Eurobitume´s Technical Committee and Task Forces, so the likely implications for testing and calculation methods could be determined.

Findings and recommendations

  • DSR (Dynamic Shear Rheometer) - test method standard EN 14770 describes how to use this device to determine the complex shear modulus and phase angle: measurements were considered and confirmed that this is a more accurate and reliable way to assess binder properties, specifically with regard to elevated service temperature performance, than Softening Point Ring and Ball.

Eurobitume has produced a helpful Technical Information Sheet for the DSR test method, based upon EN 14770, which is available here.

  • Needle Penetration - EN 1426: is still a good test of the behaviour of all types of bitumen at intermediate service temperatures, especially for quality control purposes, as it is based on decades of experience in correlating with field data.

Eurobitume’s Needle Penetration Technical Information Sheet is available here.

  • BBR (Bending Beam Rheometer) - EN 14771: valuable input was generated that Eurobitume will put forward into the test standard’s revision, in order to assess the low service temperature crack resistance:

    • Suggest the use of BBR test data (creep stiffness S and m-value) to calculate further useful parameters, such as the temperature where S equals a threshold value and the respective m-value.
    • Recommend logarithmic interpolation for creep stiffness-based calculations and linear interpolation for m-value calculations.

Eurobitume’s BBR Technical Information Sheet is available here.

Validated Eurobitume technical positions

Analysis of the data collection project results showed that the positions Eurobitume used in 2020 to input into the revision of PMB standard EN 14023, while not all limited to PMB, were still valid.

  • On BBR testing and the assessment of low temperature binder performance
    • Recommendation to test on long-term aged binders for specification purposes
    • Conduct logarithmic interpolation for calculations relating to stiffness, S
    • Use linear interpolation for calculations relating to m-value
  • Equi-stiffness temperature - should be addressed by T (G* = 15 kPa) and respective phase angle, calculated from DSR testing.

  • MSCRT testing: conduct MSCRT (Multiple Stress Creep and Recovery Test) testing on short-term aged binders to assess performance. The potential for MSCRT to provide additional, useful data on non-modified binders should be explored. Eurobitume’s MSCRT Technical Information Sheet is available here.

  • MSCRT test temperatures: preference to test at different temperatures, e.g. for specification purposes in Europe 45, 60 and 75°C.

  • Introduce DSR temperature sweep on fresh binders for specifications on polymer modified binders, instead of measuring the softening point using the Ring and Ball test method. This is because the results of the Ring and Ball softening point test method on PMB need to be interpreted differently from those on paving grade bitumen.