Team introduction – Gemma Mathieson (PhD Candidate)
Gemma has 10 years of industry experience in asset management, where she specialised in asset deterioration modelling and lifecycle planning across the asset classes of pavements, 3 waters pipe renewals and bridges. Gemma has completed both a Master of Engineering Studies in Transportation and a Bachelor of Engineering in Engineering Science at the University of Auckland. She is currently studying towards a Doctor of Philosophy in Civil Engineering.
Gemma’s role in the project is to analyse the various data sets, calibrate the HDM-4 models and develop new model formats.
Deterioration Model Development
This phase of the project was designed to develop, calibrate, and test models to predict the performance of Modified Epoxy Chip Seals (MECS) and Modified Epoxy Asphalt Surfaces (MEAS) under changing climates and traffic, based on data collected from existing roads and trials. This includes both the calibration of the existing HDM-4 models, as well as the development of new models.
Although the performance of modified epoxy surfacings has been demonstrated through trials in New Zealand and, in the case of MEAS, is now routinely used in service, the trial or in-service data in Ethiopia will only become available in later years. The following figure depicts the overview of the approach to be adopted to recognise this limitation.
There are two potentially comparable data sets available to the research, one in New Zealand and one in Ethiopia. The New Zealand dataset, identified in yellow in the figure on the right, is the Long-Term Pavement Performance (LTPP) dataset. This dataset contains approximately 20 years of data, across different traffic loadings and climatic regions within New Zealand. The Ethiopia dataset, identified in turquoise, is the Highway Development and Management (HDM) study trials.
A comparative analysis of these two datasets will allow for the establishment of relationships that quantify/model the relative performance between New Zealand roads and Ethiopian roads with reasonably similar characteristics for traditional chipseals and asphalt surfacings.
The next step, identified in blue, is to understand the relationship, in terms of improved performance, between the traditional surfacings in the New Zealand LTPP study and the modified epoxy trials in New Zealand. The epoxy laboratory studies will also be used as appropriate to help develop these relationships.
Finally, given that the relative performance of the New Zealand LTPP surfacings to both the Ethiopian surfacings and the New Zealand modified epoxy surfacings will be known, a calibration or adjustment factor, identified in red, will be determined to predict the performance of modified epoxy surfacings in Ethiopia.
Trial and Laboratory Test Results
On the 14th December 2021, Dr Theuns Henning (University of Auckland) and David Alabaster (New Zealand Transport Agency) presented the performance results from laboratory tests, trials and application of the epoxy modified bitumen. The results showed that epoxy modified bitumen significantly outperforms traditional bitumen in all tests undertaken thus far. These laboratory tests will be invaluable to understand the relative performance difference between traditional surfaces and the Epoxy Modified Binders.
The photos below show an example of the re-orientation and embedment test comparing traditional 180/200 bitumen (left) and epoxy bitumen (right). The test simulated 12 hours of traffic at 35 degrees Celsius.
Another test performed in the laboratory was a fatigue test. The following graph shows the resulting cycles to failure of six different OGPA samples. The samples included four epoxy mixes, unmodified 80/100 bitumen, and Sytrenebutadiene-styrene (SBS) polymer. All of the mixes containing epoxy outperformed the latter two. The 75% and 100% epoxy samples reached the maximum number of cycles without failure. This suggests the epoxy modified OGPA will significantly outperform traditional OGPA in terms of long term durability.
Bagshaw, S. A., Herrington, P. R., & Wu, J. P. (2015). Preliminary examination of chipseals prepared with epoxy-modified bitumen. Construction and Building Materials, 88, 232–240. https://doi.org/10.1016/j.conbuildmat.2015.04.003
Wu, J. P., Herrington, P. R., & Alabaster, D. (2019). Long-term durability of epoxy-modified open-graded porous asphalt wearing course. International Journal of Pavement Engineering, 20(8), 920–927. https://doi.org/10.1080/10298436.2017.1366764