CRISPS Newsletter – February 2022
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.
References
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
Launch of the project CRISPS – Climate resilient sustainable road pavement surfacings
One or several simultaneous changes in the climate conditions, e.g. hotter seasons, extreme precipitation events, increasing severe storms and sea level rise could severely affect roads in LICs. Missing to appreciate such an impact in future road design, maintenance and operating planning and protocols, could cause accelerated road deterioration and increased risk of damage, traffic disruption and accidents with knock-on effects on economy.
To address this, the CRISPS multi-disciplinary research project will operate over 18 months under the leadership of the University of Birmingham (UoB) and in collaboration with the University of Auckland (UoA), the Universiti Putra Malaysia (UPM) and the International Road Federation (IRF).
The aim of this project is to achieve an affordable high-volume road resilient approach to climate change and traffic demands, by assessing the suitability of three global best practice types of road surfacing technologies for use in LICs to counter the impacts of climate change, namely Modified Epoxy Chip Seals (MECS), Modified Epoxy Asphalt Surfaces (MEAS) and Fibre Mastic Asphalt (FMA) respectively. The technologies are a result of many years of research in New Zealand (MECS and MEAS) and Malaysia (FMA) where their in-situ performance has been demonstrated through trials and they are as a result routinely used in service.
The research will utilise a modelling approach which considers life cycle analysis and via the practical application of the approaches in Ethiopia. An anti-fraud methodology for testing the components of the technologies using neutron beam particle analysis will also be trialled. The objectives of the research are:
- The development of models of the behaviour of the three technologies under the variety of current and future environmental (i.e., climate and subgrade/ base course) and traffic conditions found in HVT roads in LICs in Africa and S. Asia.
- A scoping exercise to identify existing chip seals in LICs that are at risk and could benefit from MECS, MEAS or FMA and for new roads.
- The development of life cycle models for the technologies, considering the effects of climate change, both for the construction of new roads and for resurfacing (overlay).
- Scoping inexpensive anti-fraud in-situ testing methodologies for MEAS, MECS, based on neutron beam particle analysis.
- Building and testing in Ethiopia innovative low-cost easy application methods for the three technologies.
Join the CRISPS LinkedIn Group to become part of the community of practice and exchange knowledge and expertise.
An introductory webinar on the project will be hosted on 10th December at 9:00 AM (CET). Register your participation.
