Michael D. Lepech

Dynamic Life-Cycle Modeling of Pavement Overlay Systems: Capturing the Impacts of Users, Construction, and Roadway Deterioration

Pavement systems provide critical infrastructure services to society but also pose significant impacts related to large material consumption, energy inputs, and capital investment. A life-cycle model was developed to estimate environmental impacts resulting from material production and distribution, overlay construction and preservation, construction-related traffic congestion, overlay usage, and end of life management. To improve sustainability in pavement design, a promising alternative material, engineered cementitious composites (ECC) was explored. Compared to conventional concrete and hot-mixed asphalt overlay systems, the ECC overlay system reduces life-cycle energy consumption by 15 and 72%, greenhouse gas emissions by 32 and 37%, and costs by 40 and 47%, respectively. Material, construction-related traffic congestion, and pavement surface roughness effects were identified as the greatest contributors to environmental impacts throughout the overlay life cycle. The sensitivity analysis indicated that traffic growth has much greater impact on the life-cycle energy consumption and environmental impacts of overlay systems compared to fuel economy improvements.

Cradle-to-gate life cycle assessment for a cradle-to-cradle cycle: biogas-to-bioplastic (and back).

At present, most synthetic organic materials are produced from fossil carbon feedstock that is regenerated over time scales of millions of years. Biobased alternatives can be rapidly renewed in cradle-to-cradle cycles (1-10 years). Such materials extend landfill life and decrease undesirable impacts due to material persistence. This work develops a LCA for synthesis of polyhydroxybutyrate (PHB) from methane with subsequent biodegradation of PHB back to biogas (40-70% methane, 30-60% carbon dioxide). The parameters for this cradle-to-cradle cycle for PHB production are developed and used as the basis for a cradle-to-gate LCA. PHB production from biogas methane is shown to be preferable to its production from cultivated feedstock due to the energy and land required for the feedstock cultivation and fermentation. For the PHB-methane cycle, the major challenges are PHB recovery and demands for energy. Some or all of the energy requirements can be satisfied using renewable energy, such as a portion of the collected biogas methane. Oxidation of 18-26% of the methane in a biogas stream can meet the energy demands for aeration and agitation, and recovery of PHB synthesized from the remaining 74-82%. Effective coupling of waste-to-energy technologies could thus conceivably enable PHB production without imported carbon and energy.

Life-Cycle Optimization of Pavement Overlay Systems

Preservation (maintenance and rehabilitation) strategy is the critical factor controlling pavement performance. A life-cycle optimization (LCO) model was developed to determine an optimal preservation strategy for a pavement overlay system and to minimize the total life-cycle energy consumption, greenhouse gas (GHG) emissions, and costs within an analysis period. Using dynamic programming optimization techniques, the LCO model integrates dynamic life-cycle assessment and life-cycle cost analysis models with an autoregressive pavement overlay deterioration model. To improve sustainability in pavement design, a promising alternative material for pavement overlays, engineered cementitious composites (ECCs), was studied. The LCO model was applied to an ECC overlay system, a concrete overlay system, and a hot mixed asphalt (HMA) overlay system. The LCO results show that the optimal preservation strategies will reduce the total life-cycle energy consumption by 5–30%, GHG emissions by 4–40%, and costs by 0.4–12% for the concrete, ECC, and HMA overlay systems compared to the current Michigan Department of Transportation preservation strategies, respectively. The impact of traffic growth on the optimal preservation strategies was also explored.

Network-Level Pavement Asset Management System Integrated with Life-Cycle Analysis and Life-Cycle Optimization

AbstractThe authors have developed a new network-level pavement asset management system (PAMS) utilizing life-cycle analysis and optimization methods. Integrated life-cycle assessment and cost analysis expand the scope of the conventional network-level PAMS from raw material extraction to end-of-life management. To aid the decision-making process, the authors applied a life-cycle optimization model to determine the near-optimal preservation strategy for a pavement network. The authors utilized a geographic information system (GIS) model to enhance the network-level PAMS by collecting, managing, and visualizing pavement information data. The network-level pavement asset management system proposed in this paper allows decision makers to preserve a healthy pavement network and minimize life-cycle energy consumption, greenhouse gas (GHG) emissions, or cost as a single objective, and also meet budget constraints and other agency constraints within an analysis period. A case study of a pavement network in Michi...

Large-Scale Processing of Engineered Cementitious Composites

Large scale investigation of engineered cementitious composite (ECC) design, processing, and evaluation is undertaken up to 3 cu m (4 cu yd). In order to retain high-performance fiber-reinforced cementitious composites (HPFRCC) characteristic pseudo-tensile strain-hardening properties while transit truck mixing procedures and short mixing times are optimized, ECC design is undertaken. Tensile multiple cracking and grain size distribution criterion form the basis of material design. Both large scale (3 cu m (4 cu yd) and small scale (200 L (7 cu ft)) design procedure success is demonstrated. To establish a preliminary large-scale mixing test result statistical analysis-based preliminary design value set, there was testing of large-scale mixing specimen material properties. Tests show that for the ECC-M45 material tested with 99% confidence, tensile strain, tensile strength, and compressive strength design parameters can be set at 2.0%, 4.35 MPa (630 psi), and 60 MPa (8.75 ksi), respectively.

Design of Green Engineered Cementitious Composites for Improved Sustainability

The sustainability of the built environment is increasingly coming to the forefront of infrastructure design and maintenance decisions. To address this, development of a new class of more sustainable cement-based materials is needed. These materials should be developed with respect to the final application in which they will be used. Neglecting the connection between material development, structural design, and sustainability objectives can lead to shorter-lived, costly, and resource-intensive structures that require greater maintenance. Within this study, a green materials design framework is presented and used to complete a case study in the design of green materials for a specific infrastructure application. Through deliberate control of composite constituents and the interactions among them, cement-based composites have been developed that incorporate industrial waste streams while not sacrificing critical material properties.

Techno-ecological synergy: a framework for sustainable engineering.

Even though the importance of ecosystems in sustaining all human activities is well-known, methods for sustainable engineering fail to fully account for this role of nature. Most methods account for the demand for ecosystem services, but almost none account for the supply. Incomplete accounting of the very foundation of human well-being can result in perverse outcomes from decisions meant to enhance sustainability and lost opportunities for benefiting from the ability of nature to satisfy human needs in an economically and environmentally superior manner. This paper develops a framework for understanding and designing synergies between technological and ecological systems to encourage greater harmony between human activities and nature. This framework considers technological systems ranging from individual processes to supply chains and life cycles, along with corresponding ecological systems at multiple spatial scales ranging from local to global. The demand for specific ecosystem services is determined from information about emissions and resource use, while the supply is obtained from information about the capacity of relevant ecosystems. Metrics calculate the sustainability of individual ecosystem services at multiple spatial scales and help define necessary but not sufficient conditions for local and global sustainability. Efforts to reduce ecological overshoot encourage enhancement of life cycle efficiency, development of industrial symbiosis, innovative designs and policies, and ecological restoration, thus combining the best features of many existing methods. Opportunities for theoretical and applied research to make this framework practical are also discussed.

Dynamic Life Cycle Assessment of Building Design and Retrofit Processes

Designers and managers of buildings and other constructed facilities cannot easily quantify the sustainability impacts of structures for improved analysis, management, or decision-making. This is due in part to the lack of interoperability between design and analysis software and datasets that enable full life cycle assessment (LCA) of constructed facilities. This work develops a computational framework to enable building designers, engineers, contractors, and managers to reliably and efficiently construct dynamic life cycle models that capture environmental impacts associated with every life cycle phase. This includes 3D architectural tools, structural software, and virtual design and construction packages. Use phase impacts can be quantified using distributed sensor networks. This integration provides a dynamic LCA modeling platform for management of facility footprints in real-time during construction and use phases, offering unique analysis opportunities to examine the tradeoffs between design and construction/operation decisions.

Overview of a cyber-enabled wireless monitoring system for the protection and management of critical infrastructure systems

The long-term deterioration of large-scale infrastructure systems is a critical national problem that if left unchecked, could lead to catastrophes similar in magnitude to the collapse of the I-35W Bridge. Fortunately, the past decade has witnessed the emergence of a variety of sensing technologies from many engineering disciplines including from the civil, mechanical and electrical engineering fields. This paper provides a detailed overview of an emerging set of sensor technologies that can be effectively used for health management of large-scale infrastructure systems. In particular, the novel sensing technologies are integrated to offer a comprehensive monitoring system that fundamentally addresses the limitations associated with current monitoring systems (for example, indirect damage sensing, cost, data inundation and lack of decision making tools). Self-sensing materials are proposed for distributed, direct sensing of specific damage events common to civil structures such as cracking and corrosion. Data from self-sensing materials, as well as from more traditional sensors, are collected using ultra low-power wireless sensors powered by a variety of power harvesting devices fabricated using microelectromechanical systems (MEMS). Data collected by the wireless sensors is then seamlessly streamed across the internet and integrated with a database upon which finite element models can be autonomously updated. Life-cycle and damage detection analyses using sensor and processed data are streamed into a decision toolbox which will aid infrastructure owners in their decision making.

Guiding the design and application of new materials for enhancing sustainability performance: Framework and infrastructure application

This paper presents a framework for guiding the design of new materials to enhance the sustainability of systems that utilize these materials throughout their production, use and retirement. Traditionally, materials engineering has focused on the interplay between material microstructure, physical properties, processing, and performance. Environmental impacts related to the system’s life cycle are not well integrated into the materials engineering process. To address this shortcoming, a new methodology has been developed that incorporates social, economic, and environmental indicators – the three dimensions of sustainability. The proposed framework accomplishes this task and provides a critical tool for use across a broad class of materials and applications. Material properties strongly shape and control sustainability performance throughout each life cycle stage including materials production, manufacturing, use and end-of-life management. Key material parameters that influence life cycle energy, emissions, and costs are highlighted. The proposed framework is demonstrated in the design of engineered cementitious composites, which are materials being developed for civil infrastructure applications including bridges, roads, pipe and buildings. This research is part of an NSF MUSES (Materials Use: Science, Engineering and Society) Biocomplexity project on sustainable concrete infrastructure materials and systems (http://sci.umich.edu).