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Measurement Science for Sustainable Infrastructure Materials

The primary core competencies for the Strategic Priority Area of Measurement Science for Sustainable Infrastructure Materials are performance, durability, and the service-life prediction of building materials. A secondary core competency involves fire protection and fire spread within buildings and communities.

The areas of expertise in this Strategic Priority Area are materials-based and include polymers, concrete and associated inorganic materials, and flammability, with an emphasis on polymeric materials. This subject area covers three primary topics, involving three groups, in the overall area of building and fire research. The BFRL divisions involved with this priority are the Fire Research Division and the Materials and Construction Research Division. The specific groups are the Polymeric Materials Group and the Inorganic Materials Group in the MCRD and the Materials Flammability Group in the FRD.

The major change in these topics since the previous review is the transition from an emphasis on nanotechnology to an emphasis on sustainability. The prediction of the life cycle of high-performance polymers and composites, including nanocomposites, is an area that is now embracing sustainability concerns relative to the choice of materials selected for present and emerging applications. An area of increasing interest relative to sustainability involves predicting the service-life performance of concrete building and infrastructure materials. Another project involves the reduction of the flammability of materials as halogenated flame retardants become less accessible to the material suppliers for use in flame-retardant compositions. The areas reviewed have done an excellent job of making the transition from an emphasis on nanotechnology to an emphasis on sustainability, and there are overlapping goals for each emphasis.

TECHNICAL MERIT RELATIVE TO STATE OF THE ART

In the study of the life cycle of high-performance polymers and composites, several topics are being investigated, including outdoor and accelerated aging of nanostructured polymeric systems, multiscale mechanical properties of polymeric materials, and nanoparticle release during the life cycle of nanostructured materials. The outdoor accelerated aging of nanostructured polymeric materials is a research thrust of national importance. Using reliability principles to establish a relationship between accelerated and real-time aging using cumulative damage models appears to be an appropriate approach. More information on the successes of this model in relating the accelerated test results with outdoor weathering data would be helpful in assessing the results of this effort. The multiscale study of the properties of polymeric composite materials is focused on nano-reinforced polymers using nano-indention to determine elastic modulus. Although modulus is an important measure, other measures such as glass transition temperature, coefficient of thermal expansion, and cure shrinkage are important properties influenced by reinforcement characteristics. The application of other approaches such as Dynamic Mechanical Analysis and Differential Scanning Calorimetry



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4 Measurement Science for Sustainable Infrastructure Materials The primary core competencies for the Strategic Priority Area of Measurement Science for Sustainable Infrastructure Materials are performance, durability, and the service-life prediction of building materials. A secondary core competency involves fire protection and fire spread within buildings and communities. The areas of expertise in this Strategic Priority Area are materials-based and include polymers, concrete and associated inorganic materials, and flammability, with an emphasis on polymeric materials. This subject area covers three primary topics, involving three groups, in the overall area of building and fire research. The BFRL divisions involved with this priority are the Fire Research Division and the Materials and Construction Research Division. The specific groups are the Polymeric Materials Group and the Inorganic Materials Group in the MCRD and the Materials Flammability Group in the FRD. The major change in these topics since the previous review is the transition from an emphasis on nanotechnology to an emphasis on sustainability. The prediction of the life cycle of high-performance polymers and composites, including nanocomposites, is an area that is now embracing sustainability concerns relative to the choice of materials selected for present and emerging applications. An area of increasing interest relative to sustainability involves predicting the service-life performance of concrete building and infrastructure materials. Another project involves the reduction of the flammability of materials as halogenated flame retardants become less accessible to the material suppliers for use in flame-retardant compositions. The areas reviewed have done an excellent job of making the transition from an emphasis on nanotechnology to an emphasis on sustainability, and there are overlapping goals for each emphasis. TECHNICAL MERIT RELATIVE TO STATE OF THE ART In the study of the life cycle of high-performance polymers and composites, several topics are being investigated, including outdoor and accelerated aging of nanostructured polymeric systems, multiscale mechanical properties of polymeric materials, and nanoparticle release during the life cycle of nanostructured materials. The outdoor accelerated aging of nanostructured polymeric materials is a research thrust of national importance. Using reliability principles to establish a relationship between accelerated and real-time aging using cumulative damage models appears to be an appropriate approach. More information on the successes of this model in relating the accelerated test results with outdoor weathering data would be helpful in assessing the results of this effort. The multiscale study of the properties of polymeric composite materials is focused on nano-reinforced polymers using nano-indention to determine elastic modulus. Although modulus is an important measure, other measures such as glass transition temperature, coefficient of thermal expansion, and cure shrinkage are important properties influenced by reinforcement characteristics. The application of other approaches such as Dynamic Mechanical Analysis and Differential Scanning Calorimetry 22

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can be helpful in understanding resulting properties. Non-invasive characterization of dispersion in polymeric composites is a grand challenge that will benefit the field of nanocomposites enormously, but progress has been slow. Dispersion of nanoparticles is a critical issue. The measurement of dispersion using angular optical scattering should be complemented by using laser scattering, x-ray scattering, and microtomography imaging. The nanoparticle life-cycle study focused on the release of carbon nanostructures from polymer nanocomposites subjected to ultraviolet radiation. This project is in response to a major concern on the potential toxicity of nanoparticles employed in materials that may be released to the environment in their life cycle. The development of a system for the detection and collection of released products is the primary objective of this study. It is important that the study establish test samples with appropriate degrees of dispersion, since poorly dispersed systems are likely to show high levels of carbon nanotube release that may not be characteristic of well-dispersed systems. The development of measurement science for sustainable cement-based materials is of great importance to the civil infrastructure in the United States. Research currently being conducted in the Inorganic Materials Group in sustainable cement-based materials will retain, strengthen, and extend the historic global leadership of the BFRL in microstructure modeling and characterization tools. This research is well aligned with its core mission in regard to performance, durability, and service-life predictions of building materials. There is a strong urgency to extend the service life of the U.S. infrastructure while utilizing cements with a low carbon footprint by substituting cements with industrial waste products such as fly ash or slag. The research being conducted at the BFRL is at the forefront in regard to developing rheology-based models and measurement and characterization tools that will enable the routine commercial use of high volumes of fly ash and slag in concrete, which are essential for producing more durable and sustainable concrete structures. The BFRL approach in characterizing fly ash and relating it to its performance is unique, and no such projects are currently being conducted in or outside the United States. Major accomplishments in this area are evidenced by the receipt of the ASTM P.H. Bates Memorial Award (2008) and the NIST Bronze Medal (2007) for the development of a new ASTM x-ray diffraction (XRD) standard method. In addition, the mitigation of early age cracking is essential in enhancing the durability of concrete structures. The BFRL is currently working on guidelines for measuring the concrete properties that contribute to early age cracking and on mitigation strategies. The BFRL’s impact in this area is evidenced by the receipt of the prestigious American Concrete Institute (ACI) Wason Medal and the Frank G. Erskine Award. The BFRL should continue the microstructure modeling with the emphasis on molecular dynamic modeling in collaboration with the efforts currently underway in Europe. NIST is a global leader in the realm of understanding material flammability. Over the past several years, the BFRL team has been very instrumental in providing critical scientific data that help in understanding fire protection, durability, and service-life prediction. The objective of the Reduced Flammability of Materials Program is to develop measurement science tools to help the material industry in producing sustainable, cost-effective, and fire-safe materials. The team has made a concerted effort in focusing on sustainability. A roadmap was established after an innovative fire protection workshop was conducted, which involved experts from academia and industry. As a 23

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result of the workshop, changes were made to strategic goals and programs. The three specific thrusts that were identified are (1) the development of bench-scale flammability measurement methods, (2) the evaluation of new models and materials for fire-safe products, and (3) the development of data and methods to enable a critical assessment of the sustainability of new fire-safe technologies. The goal of the thrusts is fully aligned with the BFRL mission and vision. One of the program goals is to design and implement measurement science tools that enable the development of fire-safe products. The compilation of a database of materials with promising sustainability attributes and the development of tools to evaluate these materials for their effectiveness as sustainable flame retardants in a series of polymer systems have already been started. The team has done an excellent job in working with a number of agencies and partners, both domestic and international, as this effort will require the tools and expertise from different disciplines such as environmental science, nanotechnology, flame retardancy, and life-cycle assessment. One of the major practical issues is the flammability of polyurethane foam. According to National Fire Protection Association (NFPA) reports,7,8,9 reducing the flammability of materials used in products found in homes, automobiles, and building insulation could reduce the total core cost of fire to the U.S. economy. This would also significantly enhance public safety. U.S. fire deaths attributed to the burning of polyurethane foam products remain a major fraction of the total fatalities recorded in home fires. Development of the measurement science to enable industry to produce fire- safe foam products requires the development of an extensive knowledge base for several complex technologies. The BFRL team had taken this as a goal several years ago and was able to develop a vertical cone calorimeter test method. In the past 2 years, the team has been able to show the utility of this test method as a possible screening tool that will take dripping into consideration. This test method has already gained traction, as some laboratories have started using it. The next step will have to be that of working with regulatory bodies to show the relevance as a test method and to incorporate it into a standard test. NIST has made major contributions to the understanding and use of nanocomposites to reduce flammability in polymers. One of the concerns that the industry has regarding nanocomposites is the release of nanoparticles into the environment. The BFRL team has been working on a project to develop techniques to quantify the yields, chemical compositions, morphologies, and size distributions of nanoparticles released into the environment. This is not an easy problem. The challenge is that of making measurements of nanoparticle release while still considering the potential health hazards. The developments in this area will be critical in answering the question of nanoparticle release in terms of actual quantifiable data. 7 John R. Hall, Jr., “The Total Cost of Fire in the United States,” Fire Analysis and Research Division, National Fire Protection Association, February 2008. 8 Michael J. Karter, Jr., ”U.S. Fire Loss for 2006,” NFPA Journal 101(5):64, 2007. 9 Marty Ahrens, “Home Fires That Began with Upholstered Furniture,” National Fire Protection Association, Quincy, Mass., May 2008. 24

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ADEQUACY OF INFRASTRUCTURE The equipment and personnel necessary to carry out the goals and objectives of the projects in place appear to be adequate. Specific equipment deficiencies have been partially resolved with ARRA stimulus funds obtained in the past year. Additional equipment and capital items could, however, advance the performance of this division as it focuses on critical sustainability issues involving key materials. The concrete area appears to be one in which the Inorganic Materials Group offers a unique service to the huge (and energy-consuming) concrete industry by conducting more fundamental research and establishing measurement standards for more-sustainable concrete products. This area could benefit from a state-of-the-art testing facility for future cement-based materials (such as fly-ash-modified concrete) and for the potentially huge concrete market in the re-emerging nuclear power market. A need was expressed for a polymer materials scientist with modeling skills and also for life-cycle analysis expertise for the flame-retardant materials area. Succession planning was discussed with the panel; the plans should be reviewed as needed, because several retirements may occur in the next several years. ACHIEVEMENT OF OBJECTIVES AND IMPACT The change in priority emphasis from nanotechnology to sustainability obviously modifies the objectives and desired impacts of each specific project. The Sustainable Infrastructure Materials priority area has done an excellent job in making the proper changes in the priorities. This was quite helpful, as the projects in place also were directed toward goals consistent with sustainability issues. A review of the two major impact areas noted in the previous (2008) panel report demonstrated continued effort and success in implementing these measurement techniques into broader external use. The integrating sphere weatherability testing equipment has several companies seeking Small Business Innovation Research support for commercialization, and the modified cone calorimeter vertical flammability test apparatus is now used by several external laboratories for polyurethane foam. The measurement science developed in the BFRL group for sustainable cement- based materials provides the fundamental understanding in developing standards and ASTM protocols, which allows the technology to be readily transferred to industry. For example, the XRD standard test method that was developed at the BFRL in the Inorganic Materials Group has recently been incorporated into a new ASTM standard. The BFRL was contacted by Roman Cement LLC to utilize the characterization tools developed in the Inorganic Materials Group. The Virtual Cement and Concrete Test Laboratory, resulting from its pioneering work in hydration modeling, is well recognized by national and international researchers and is in the process of being adopted by industrial partners. The inorganic cement group has an excellent record of publishing in peer-reviewed journals and of collaboration with universities, nationally and internationally. The areas where achievements in the past several years should result in potential impact in areas of national interest include the fundamental measurement and characterization work conducted on fly-ash-modified concrete. The assessment of nanoparticle release into the environment was addressed as a concern several years ago, 25

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and meaningful progress has been achieved toward answering this environmental and health issue. CONCLUSIONS The Strategic Priority Area of Measurement Science for Sustainable Infrastructure Materials is focused on the measurement and characterization of materials for meeting the sustainability requirements of the future. The core competency is crucial to the infrastructural materials requirements of the future. The critical skills are present to meet the core competency requirements as well as to investigate the technical projects in progress. Overall, the laboratory is well equipped (except as noted), and changes in project execution made in the past several years have proven fruitful. These changes include the implementation of a more detailed safety review procedure and adaptation of the Stage-Gate process to ensure that projects are properly focused and not directed in a chaotic fashion. The publications and presentations by group members continue to be impressive, illustrating the technical impact that this area has on its external peer group. One of the important missions of this Strategic Priority Area (as well as of most programs at NIST) is to ensure that other government agencies have the necessary information to make proper decisions. The material choices for present and future needs are sometimes dominated by other agencies (the Environmental Protection Agency as an example). Where material choices are impacted by sustainability issues, this group should be proactive with other government agencies to ensure that proper choices are made. Many of these decisions involve risk–reward analysis, which NIST is more equipped to determine than most other agencies are. The group is placing appropriate emphasis on utilizing the sustainability model developed at NIST (Building for Environmental and Economic Sustainability, or BEES). It would be useful if this model were specifically linked to infrastructure materials. Another emerging area, in which the Inorganic Materials Group involved with concrete should be actively engaged, is the emerging nuclear power plant construction. Codes and standards for these plants are more than 30 years old. This group is in a unique position to offer valuable expertise related to concrete utilization in this re-emerging industry. RECOMMENDATIONS The recommendations of the panel based on its assessment of the Strategic Priority Area of Measurement Science for Sustainable Infrastructure Materials are as follows:  The measurement of the dispersion of nanoparticles using angular optical scattering should be complemented by the use of laser scattering, x-ray scattering, and microtomography imaging.  It is important that the nanoparticle life-cycle study establish test samples with appropriate degrees of dispersion.  The BFRL should continue the microstructure modeling, with the emphasis on molecular dynamic modeling, in collaboration with the efforts currently underway in Europe. 26

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 The next steps for the vertical cone calorimeter test method will have to be those of working with regulatory bodies to show its relevance as a test method and incorporating it into a standard test.  Additional equipment and capital items could advance the performance in the Measurement Science for Sustainable Infrastructure Materials Strategic Priority Area as the researchers focus on critical sustainability issues involving key materials.  The concrete work could benefit from a state-of-the-art testing facility for future cement-based materials (such as fly-ash-modified concrete) and for the potentially huge concrete market in the re-emerging nuclear power market.  The expressed needs for a polymer materials scientist with modeling skills and for life-cycle-analysis expertise for the flame-retardant materials area should be addressed.  Staff succession plans should be reviewed as needed.  The material choices for present and future needs are sometimes dominated by other agencies. Where material choices are impacted by sustainability issues, the staff in the Measurement Science for Sustainable Infrastructure Materials Strategic Priority Area should be proactive with other government agencies to ensure that proper choices are made.  The sustainability model developed at NIST (Building for Environmental and Economic Sustainability) should be specifically linked to infrastructure materials.  The Inorganic Materials Group involved with concrete should be actively engaged with the re-emerging nuclear power plant construction industry to offer its valuable expertise related to the use of concrete. 27