Concrete use in infrastructures such as roadways, bridges and pipes causes huge material flows between natural and human systems. Global concrete construction exceeds 6 billion tons/yr and contributes to significant challenges in sustainability performance as measured by environmental, economic and social indicators. Critical issues include substantial greenhouse gas emissions, major land disturbances, air pollution, and roadway-related traffic congestion and vehicle damage. Alternative materials are being developed to improve the functional performance of concrete infrastructure systems. Engineered cementitious composites (ECC) are an especially promising material for these applications. ECC formulations can be designed through microstructure tailoring of input materials including matrix (cement, fly ash), fiber (virgin and recycled polymers) and interface elements. Strain capacities up to 500-600 times greater than normal concrete have been achieved, giving aluminum-like properties. Currently, decisions about formulating and applying ECC are guided strictly by functional performance and financial cost. Broader environmental, social and economic issues related to life cycle impacts of infrastructure systems have gone unrecognized. The goal for this research is to integrate life cycle indicators and ECC microstructure tailoring to enhance the sustainability of infrastructure systems.
To address the complexity in optimizing the sustainability of ECC-based infrastructures, a conceptual framework that integrates multi-criteria evaluations, multi-scale boundaries, and multi-disciplinary perspectives was proposed. The traditional civil engineering approach to infrastructure design has only considered structural shape and dimensions, and material properties for meeting performance requirements. This research is developing and applying life cycle environmental, economic and social criteria to guide materials science and engineering research in the development of ECC-based infrastructure systems. The development of criteria is complex due to the diverse nature of impacts, the range of scales of analyses (nanometers in materials science to kilometers in the geological sciences), the long-lived nature and consequences of infrastructure systems, and the need to optimize the timing of large infrastructure capital investments. To effectively integrate these factors, a multi-disciplinary team of investigators drawn from civil engineering, materials science and engineering, industrial ecology, environmental economics, economic geology, and environmental health sciences is collaborating. Results from the proposed novel framework, which integrates microstructure tailoring and macroscale life cycle modeling and assessment, will enhance decision-making capabilities of earth scientists, materials scientists, infrastructure planners and public policymakers. An important benefit is that framework will be transferable to the design of other emergent materials that are characterized by large societal investments and complex sustainability challenges.
Research is organized into three complementary sets of tasks: microscale research activities, macroscale research activities, and integrated activities. An integrated material design framework will be developed to translate infrastructure environmental, economic and social requirements into microstructure design parameters. It will be tested and refined by applying it to a specific infrastructure system. Specific research activities include: 1) mapping various ECC formulations to functional performance requirements of infrastructure applications; 2) screening ECC formulations and infrastructure applications; 3) conducting preliminary sustainability evaluations (i.e., environmental, economic and social) of a specific ECC infrastructure application; also, conducting a baseline assessment of a conventional concrete system; and 4) performing sensitivity analyses to identify the key micro and macro model parameters that influence the sustainability indicators. Results of this research will be reported and used to plan a multi-year proposal that will involve detailed life cycle modeling, microstructure tailoring and laboratory testing of an expanded set of ECC systems.
This research draws upon the diverse expertise and resources of a multi-disciplinary network of faculty at the University of Michigan. Participating units include the Advanced Civil Engineering Material Research Lab, the Center for Sustainable Systems, College of Engineering, School of Public Health, School of Natural Resources and Environment, and the Department of Geological Sciences. This project emphasizes student education and research training through the following: two graduate student research assistantships; specialized curriculum in the field of industrial ecology; a field component at a local cement manufacturer; a MUSES seminar series, and participation in monthly research team workshops.