MSCA-COFUND-CLEAR-Doc - PhD Position #CD21-17 "Multi-material optimization to reduce urban heating in pavements"

Since the last few years, rising temperature in urban areas, commonly referred to as urban heat island (UHI) effects, has been a focus of attention from researchers, scientists and engineers and the general public (ADEME 2012). A recent example of this phenomenon from European perspective was captured by the National Aeronautics and Space Administration (NASA) (https://www.jpl.nasa.gov/news/nasas-ecostress-maps-european-heat-wave-fr...) during the heat wave in 2019. Heat canyons and microclimatic events from UHI not only add tremendous stress on electrical grids, ecology, and infrastructure elements, it takes a toll on human life (more than 1000 fatalities per year in United States has been attributed to UHI). Significant efforts are on-going in France (such as discussed at CEREMA’s Ilots de chaleur project, the Institut de Recherche en Sciences et Techniques de la Ville - iRSTV Nantes, the LABEX ImU studio surchauffe urbaine à Lyon or in different projects using the SmartCity equipment of Université Gustave Eiffel) to lower UHI through innovations mainly focused on modifying building technologies, increasing vegetation in urban areas, and managing water distribution.

From the perspective of roadways, few solutions have been proposed, most prominent ones can be categorized as: installation of green spaces within roadway geometric boundaries, pavement material changes, use of evaporative cooling by water application on surface and use of subsurface energy harvesting and cooling systems. Within the last decade, development of new pavement materials to lower UHI have been undertaken resulting in proprietary materials (for example, Climat’Road and Eiffage BioKlair), high albedo pavement paints, porous/drainable layer and heat exchange embedment (for example, Ooms Road Energy Systems and Eurovia PowerRoad). Implementation efforts with some of these solutions is underway in France, for example City of Lyon has used Climat’Road coatings to lower roadway temperatures by as much as 10°C and water spray systems in Paris has demonstrated lowering of asphalt pavement surface temperature by up to 15°C (Hendel et al. 2018, Parison et al. 2020). It should be noted that majority of previous and ongoing efforts have adopted thermal analyses to optimize heat flow characteristics with limited evaluation of mechanical response and degradation from vehicular and thermally induced loads.

On the contrary to projects dealing with inventing new materials and pavement layer types to counter UHI, this doctorate proposal will focus on structural optimization (interface performance, layer arrangements, geometric extents) of UHI reducing pavement systems that currently exist and are under development. Current heat reducing treatments rely on multi-material approaches, often necessitated by need for balancing optimal thermal properties (low conductivity, high albedo and low heat capacities) with cost (ability to use conventional pavement materials and be able to use technology with existing pavements). Multi-materials are defined as those with significant mismatch of mechanical, thermal and moisture properties. Interfaces within multi-material pavements are weak links, mismatching mechanical and thermo-mechanical properties result in very high interfacial stresses and corresponding degradation (Chabot et al. 2017). This threatens resilience of future UHI lowering roadways. Climate change induced thermal cycling and increased precipitations intensifies moisture penetration to interfaces causing accelerated damage, debonding and separation of materials. To optimize a composite structure of heat reducing pavements, there is an urgent need to adopt and develop fundamental characterization of multi-material interfaces.

Previous research by within RILEM technical committees have made significant strides on this topic using conventional pavement materials (Buttlar et al. 2018; Petit et al. 2018), that can provide a pathway to initiate proposed research. Further, mechanistic properties of such interfaces need to be adopted within a computational analysis framework to find optimality of geometries. To ensure resilience of adapted pavement, effects of moisture on the interface durability and degradation cannot be ignored in characterization and modelling.

The proposed thesis is expected to undertake five main tasks to fulfil the goal of bridging knowledge gap on optimizing multi-materials in urban pavements to lower UHI and to develop a methodology for characterization of multi-material pavements and optimizing them. Task-1 will develop a detailed bibliography and a summary on the current state of the art on topic of pavement UHI solutions and their thermal, mechanical and thermo-mechanical characterizations. Topic will also include gathering of datasets to develop a loading catalogue that includes vehicular loads and future climate projections (for example, using global and regional climatic models within CMIP6) for temperature boundary conditions and moisture exposures. A case-study oriented approach will be adopted for catalogue development, targeting major French metropolitan regions. Task-2 will focus on experimental design development. Key variables will include material types, composite structures, test configurations, moisture exposure levels and loading conditions. The experimental design will be informed by task-1 findings as well as extensive experience of Ph.D. supervisor and the host institution in mechanical testing of composite materials and pavements. Task-3 will execute the testing plan developed in task-2 through laboratory characterization. Inverse analysis techniques will be employed to extract intrinsic properties of interfaces in multi-material UHI reducing pavement systems. A similar effort, using wedge splitting test results (Gharbi et al. 2022), has been used by the PhD supervisor in a recent collaborative Master’s project done with Ecole Centrale de Nantes and UNH partner. Task-4 will utilize intrinsic fracture properties of interfaces and develop pavement scale simulation models for UHI reducing pavements. Developed models will be used to optimize the composite structures with thermo-mechanical loading scenarios of real-life urban roadways.As part of mobility with UNH, Ph.D. candidate will interact with researchers in the pavement life cycle assessment domain (Haslett et al. 2019)(Haslett et al. 2021) to include LCA benchmarks (such as, global warming index) within UHI structure optimization. Lastly, task-5 of the Ph.D. thesis will focus on dissemination efforts through presentations (conference, workshop, webinars) and publications (journal articles, dissertation). CLEAR DOC external partners, specifically Pays de la Loire region will be engaged in obtaining data from actual roadways and also for technology transfer purposes."

Keywords:

multi-materials, urban heat island, urban pavement, interface, modeling

Bibliography:

ADEME (2012) Recommandation pour lutter contre l’effet d’îlot de chaleur urbain à destination des collectivités territoriales. Guide ADEME N°786

Buttlar WG, Chabot A, Dave EV, Petit C, Tebaldi G (eds) (2018) Mechanisms of Cracking and Debonding in Asphalt and Composite Pavements. Springer International Publishing, Cham. RILEM State-of-the-Art Reports 28. https://doi.org/10.1007/978-3-319-76849-6

Chabot A, Hammoum F, Hun M (2017) A 4pt bending bond test approach to evaluate water effect in a composite beam. European Journal of Environmental and Civil Engineering 21(sup1):54–69. https://doi.org/10.1080/19648189.2017.1320237

Gharbi M, Chabot A, Geffard J-L, Nguyen ML (2022) Interlaminar Mode-I Fracture Characterization Underwater of Reinforced Bituminous Specimens. Springer International Publishing, Cham, ISBM 2020. RILEM Bookseries 27: 1119–1125. https://doi.org/10.1007/978-3-030-46455-4_142

Haslett KE, Dave EV, Mo W (2019) Realistic Traffic Condition Informed Life Cycle Assessment: Interstate 495 Maintenance and Rehabilitation Case Study. Sustainability 11(12):3245. https://doi.org/10.3390/su11123245

Haslett KE, Knott JF, Stoner AMK, Sias JE, Dave EV, Jacobs JM, Mo W, Hayhoe K (2021) Climate change impacts on flexible pavement design and rehabilitation practices. Road Materials and Pavement Design 22(9):2098–2112. https://doi.org/10.1080/14680629.2021.1880468

Hendel M, Parison S, Grados A, Royon L (2018) Which pavement structures are best suited to limiting the UHI effect? A laboratory-scale study of Parisian pavement structures. Building and Environment 144:216–229. https://doi.org/10.1016/j.buildenv.2018.08.027

Parison S, Hendel M, Grados A, Jurski K, Royon L (2020) A lab experiment for optimizing the cooling efficiency and the watering rate of pavement-watering. Urban Climate 31:100543. https://doi.org/10.1016/j.uclim.2019.100543

Petit C, Chabot A, Destrée A, Raab C (2018) Recommendation of RILEM TC 241-MCD on interface debonding testing in pavements. Mater Struct 51(4):96. https://doi.org/10.1617/s11527-018-1223-y

International Mobility :

A 6 to 9 month secondment at University of New Hampshire, USA, is planned. For more details contact the PhD supervisor.