Sustainable Infrastructure Materials_ Challenges And Opportunities.pdf

Int. J. Appl. Ceram. Technol., 1–9 (2013) DOI:10.1111/ijac.12083

Sustainable Infrastructure Materials: Challenges and Opportunities Mohammad Pour-Ghaz Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Campus Box 7908, 431C Mann Hall, Raleigh, North Carolina, 27695-7908

The recent quest for developing new low carbon footprint construction materials to lower the environmental emissions and implications of infrastructure has imposed many challenges and has created many opportunities for research and development in academia and industrial sectors. The present paper, discusses and summaries these challenges and opportunities and provides a synopsis of the ideas presented in the Infrastructure sessions of the Fourth International Congress on Ceramics (ICC4). This paper also discusses recent advances in the development of sustainable infrastructure materials.

Executive Summary The recent quest for developing new low carbon footprint construction materials to lower the environmental emissions of infrastructure has imposed many challenges and has created many new opportunities for research and development in academia and industrial sectors. The present article discusses these challenges and opportunities and summaries the presented ideas in the infrastructure sessions of the Fourth International Congress on Ceramics (ICC4). Specifically, this article discusses the ideas presented by Dr. H. Jennings,1 Dr. R. Moon,2 Mr. L. Lemay,3 Dr. L. *[email protected] © 2013 The American Ceramic Society

Barcelo,4 Dr. A. Tselebidis,5 Mr. T. S. Rushing,6 Dr. M. Raimondo,7 and Dr. W. Vichit-Vadakan.8 Five major areas of emerging opportunities are discussed: (1) integration of life-cycle assessment into design methodologies and the use of innovative design to reduce the environmental loadings of the use stage of the built environment; (2) research and development is the area of multifunctional bio-inspired materials with the overall goal of sustainable development of construction materials; (3) research and development in the area of carbon sequestering construction materials; (4) developing new material processing techniques to utilize engineered nanoparticles in construction materials with an emphasis on developing

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methods for dispersing engineered nanoparticles; (5) developing “multiphysics multiscale” modeling techniques that can contribute to our fundamental understanding of the structure and long-term performance of materials with the overall goal of developing bottom-up material design approaches and reducing the experimental effort required to fundamentally characterize new materials. History and Current The projected annual demand for concrete by 2050 is approximately 16 billion tonnes.9† In general, only 13 –15% (by total mass) of concrete consists of cement. In comparison with other materials, concrete is not essentially a high carbon footprint material. The significant use of concrete as a construction material, however, results in a large overall energy consumption and environmental loadings: Cement is responsible for 70–80% of the global industrial energy use by the nonmetallic production sectors, 5% of the global anthropogenic CO2 emissions, and 3.4% of the global CO2 emissions.10 To reduce the environmental emissions and energy consumption of cement, cement manufacturers have been leading intensive research and development efforts in Portland cement manufacturing technology. As a result of these efforts, today, the Portland cement manufacturing technology is an extremely efficient technology (if the best available technology in manufacturing is used with approximately 3000 MJ/t clinker11) compared with the cement manufacturing technology used prior to the mid-1990s.12 While research in improving the cement manufacturing technology continues, research in this area will most likely result in incremental improvements and reduction in environmental emissions and implications since this technology is already advanced12 (of course, the question of whether “the best” manufacturing process available is being used by all cement manufacturing plants is not only a question of environmental emission implications and regulations, but it also requires economic feasibility). Therefore, the cement manufacturers have been investigating other avenues to reduce the environmental emissions of cement production. The use of low carbon raw materials to reduce the CO2 release from carbonate calcination is one of the

methods to reduce the environmental loadings of cement production.13 Approximately 60% of the CO2 produced in the manufacturing of the cement is the result of carbonate calcination9,12,13 (despite the common belief of 1 tonne of CO2 per tonne of cement, more accurate calculations show that the direct CO2 emission from cement is approximately 0.680 tonne of CO2 per tonne of cement4). Substitution of limestone with other low carbon materials such as slag and fly ash can result in lower liberation of CO2.13,14 The use of slag may also result in lowering of fuel consumption as lower amounts of calcium carbonate need to be dissociated.13 The use of industrial waste raw materials in cement production has been more successful in Europe compared to North America.4 Currently, cement manufacturers are investigating more innovative approaches to reduce the environmental emissions of cement. An example of these efforts is production of high-belite Portland cements. High-belite cements require less calcium carbonate for production and therefore release less CO2.12,13 High-belite cements also are produced at lower temperatures, which translates into lower CO2 emission from fuel consumption. CO2 savings from calcium carbonate and burning temperature in production of high-belite cement can amount to 10%.12 High-belite clinker, however, is significantly harder material, and grinding this clinker requires more energy. It is unclear whether the production of high-belite cement will result in less CO2 emission. High-belite cement also suffers from slow rate of hydration.13 Recently, Lafarge has produced belite calcium sulfoaluminate ferrite (BCASF)4‡ cement that not only results in 30% reduction in the direct CO2 emission (compared with Portland cement) but also this product keeps the desired characteristics of Portland cement including producibility from abundant local materials, durability, rapid strength gain, and producibility in the existing cement plants.4 In addition, this product can be substituted with supplementary cementitious materials in relatively high-volume fractions.4 BCASF is a softer material compared with the Portland cement clinker which reduces the energy consumption during grinding.4 Despite the lack of data on the long-term performance

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A tonne is a unit of mass in SI system of units and represents 1000 kg.

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Certain commercial products are identified in this paper. In no case does such identification imply endorsement by the authors, nor does it indicate that the products are necessarily the only or the best available.

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of this cement, this cement is a promising product for significant reduction in CO2 emission.4 In addition to the research and development in the area of low carbon footprint cements, researchers are developing new materials and methods to reduce the environmental impacts of concrete. Traditionally, a large portion of efforts have aimed at replacing large quantities of cement (or the entire cement) with industrial byproducts (such as fly ash, ground granulated blast furnace slag, and silica fume) or naturally occurring materials (such as limestone powder or Metakaolin). Examples of these concrete materials, among others, are high-volume fly ash (HVFA) concrete,15 alkali activated slag cements,16 alkali activated fly ash materials,17 and replacement of cement with fine limestone powder.14,18 In addition to direct methods (i.e., cement replacement) of reducing the environmental impact of concrete, indirect methods of reducing environmental impact of concrete have also been explored by researchers and industry practitioners. Examples of indirect methods are the replacement of aggregates with crushed glass19 or the use of recycled concrete.20 Recently, more advanced approaches that can potentially decrease the environmental loadings of concrete have been used. The use of lightweight aggregates (LWA)21 and superabsorbent polymers (SAP)8,22,23 as internal water reservoirs for providing internal curing (as opposed to traditional external curing) are examples of these new methods. Internal curing reduces the risk of shrinkage cracking and potentially can increase the service life of the structure by decreasing the rate of mass transport.24,25 Recently, internally cured concrete mixtures using prewetted LWA have been used in construction of superstructure of bridges, and the benefits of internal curing have been confirmed in field conditions.24,26 While production of LWA and SAP requires energy inputs and is associated with significant environmental emissions (especially in the case of LWA), if the increased service life of the infrastructure and reduced number of repairs and replacements are considered in calculating the overall environmental impact of the internally cured concrete, an overall reduction in the energy consumption and environmental loading might be achieved. To further enhance the sustainability of internally cured mixtures, researchers have incorporated internal curing into HVFA concretes,27 where the net benefit from the use of internal curing is further increased by decreasing the amount of cement used in production of concrete.

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The recent advances in nanotechnology have also provided many innovative methods to reduce the energy consumption and environmental loading of construction materials. Recently, researchers have used calcium silicate hydrate (C-S-H) nanoparticles to accelerate the hydration rate of Portland cement28,29 and have used limestone nanoparticles30,31 to accelerate the pozzalanic reaction. The slow hydration of HVFA concrete has been a major obstacle in its extensive application. The mechanical measurements using micro- and nano-indentations have provided significant information on the mechanical properties of C-S-H32 and secondary hydration products.33 These experimental data are valuable for multiscale modeling of cementitious materials. Carbon nanotubes34 and cellulose nanomaterials (as an alternative to carbon nanotubes)2 have shown potential to be used in construction materials to enhance the mechanical properties of construction materials (such as strength and fracture toughness), which can translate into thinner members and ultimately lower environmental emissions. Field application of cement-based carbon nanotube composites, however, may not be expected in close future due to economic and technical difficulties. The recent advances in molecular simulations have enabled researchers to develop breakthrough approaches toward low carbon footprint construction materials. Molecular simulations have been used to study and enhance the reactivity of belite by aluminum and sulfate doping.35 This research can result in reduction in environmental loading of cements as manufacturing belite requires substantially lower energy input and requires less limestone (i.e., decreased CO2 release from carbonate calcination).12,13 Molecular simulations have also enhanced our understanding of the role of water on the mechanical performance of C-S-H36 and formation of hydration products at extremely small time increments.37 This understanding can enable us to develop potentially transformative approaches for “design for sustainability” by engineering the materials using bottom-up philosophy. For example, computer simulations and nanoscale measurements have enhanced our understanding of the role of Ca/Si ratio on mechanical properties of cementbased materials.38 While it is not currently feasible, engineering clicker and hydration products for optimum Ca/ Si ratio to enhance their mechanical properties can ultimately reduce the amount of cement used in construction by reducing the size of concrete-based structural elements. Despite all the recent advances and the plethora of knowledge and research data, many challenges lay

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ahead of us. These challenges provide opportunities for research and development in academia and industrial sectors. In the following sections of this article, these challenges and opportunities are discussed.

Challenges While developing new materials has been the main approach to reduce the environmental emissions and implications of cement-based construction materials, characterizing and understanding the long-term behavior of the newly developed materials require significant amount of experimental efforts before they can be utilized as structural materials.1 Such experimental efforts can be a multidecade effort, while the need for construction material continues to increase. The use of byproducts in cement-based construction materials has been extensively studied, and literature is replete with research data on this subject. While the use of byproducts, such as fly ash, results in energy savings in production of concrete, the end-of-life implications of these materials are unclear. For example, concrete ground residue (CGR)—which results from grinding processes used for resurfacing of concrete pavements—is traditionally considered as a nonhazardous material.39 CGR from concrete containing byproducts, such as fly ash, may, however, contain heavy metal elements and may be considered as hazardous materials.40 Therefore, considering appropriate boundaries in performing life-cycle analysis (LCA) to assess the net environmental impact of byproducts is an important task, which imposes many challenges.41 The raw materials and processes used in the industries producing byproducts that are used in concrete are evolving. These changes can have drastic impact on the quality of the byproducts and can significantly impact the mechanical properties and the long-term performance of construction materials. Consequently, the previously developed empirical models (and research data) to predict the properties and the long-term performance of the concrete materials produced with these byproducts might not be directly applicable to the materials that will be produced using future byproducts. The use of nanoparticles in construction materials can impose environmental and health risks42,43 and has not been explored adequately. The environmental risks of engineered nanoparticles used in construction materials are especially important as workers may potentially

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be subjected to direct contact with these materials. Transportation of nanoparticles can also be a potential risk as large quantities of these materials are used and need to be transported. Exploring the use of potentially nonhazardous nanoparticles such as cellules-based nanoparticles44,45 might provide a solution to the risk associated with the use of engineered nanoparticles.2 While engineered nanoparticles have been very successful in the laboratory, the dispersion of engineered nanoparticles remains a challenging issue and has been a major obstacle in widespread application of these materials.2,46 Dispersion of engineered nanoparticles is especially problematic in high-performance cementitious mixtures that are produced with low water-tocementitious material ratio (w/cm). Dispersion of engineered nanoparticles remains one of the major challenges in widespread application of these materials. Acceptance of new materials by practitioners has always been a major issue.3 Standardization of the new materials can help the acceptance of these materials; however, other factors such as experience (and therefore preference) in using a certain materials influences the decision-making processes. Resolving this issue requires an extensive collaboration between academic and industry partners. Emerging Opportunities Utilizing Innovative Approaches to Reduce the Environmental Loadings of the Use Stage Recent studies using LCA have shown that the embodied energy of buildings amounts to a small portion of the total energy consumed during the life time of the structure.3,47 Figure 1, for example, compares the global warming potential (GWP) of a steel and a concrete commercial building located in Chicago, IL, and Phoenix, AZ, over a 60-year period. The overall GWP of concrete and steel buildings is approximately the same (concrete buildings show slightly lower GWP47). In all cases illustrated in Figure 1, the embodied (preuse) GWP of the structure is only a small fraction of the total GWP and the use stage is the major contributor to the total GWP of the building. Therefore, reducing the environmental emissions during the use stage can result in significantly more reduction in total emissions compared with the use of lower carbon footprint materials in the construction of the building (i.e., reducing the preuse environmental emissions). Innovative

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Fig. 2. Water drop on a super-hydrophobic surface. The contact angle is 178o (Picture courtesy of M. Raimondo7). Fig. 1. Embodied and operational emissions of commercial buildings (courtesy of Mr. L. Lemay3)

approaches can be utilized to reduce the environmental loadings of the use stage. Examples of these innovative approaches include the use of heating/cooling elements in floors and walls, the use of solar panels as roofing systems,48 the use of phase change materials encapsulated in LWA to store thermal energy in concrete,49 and the use of thermal mass of concrete structures to reduce energy requirement for heating the buildings.3,47 High thermal mass in concrete structures (as compared to low thermal mass in steel structures) can result in annual energy savings of 5–6% depending on the climate (Fig. 1).3,47 The use of innovative approaches to reduce the environmental loading of the use stage is one of the emerging opportunities in the field of sustainable infrastructure. Over the next few years, more innovative approaches in design of buildings and infrastructure are expected to be seen. Bio-Inspired Materials The nature is full of biological materials with complex structures that offer extraordinary mechanical and durability performance (Meyers et al.,50 and references therein). These materials very often serve multiple functionalities. The recent advances in nanotechnology, imaging, and computer modeling and simulation have enabled us to gain more insight to the underlying mechanisms responsible for the extraordinary performance of biomaterials.6,51 The hierarchical structure of

biomaterials is the main reason for their unexpected performance.52 Such a structure has been observed in antlers53—one of the most impact resistant materials— dactyl clubs of stomatopod,54 and abalone shell.55 The lessons learned from biological materials may be used in developing new construction materials that are lightweight, tough, and ductile. While understanding the underlying reason for superior mechanical performance of biomaterials has been a major focus in many studies, other interesting aspects of biomaterials are also being studied. Self-cleaning (the Lotus effect) is one of the extraordinary properties of biological surfaces, which is a result of superhydrophobic effect.7,56 Interestingly, similar to the mechanical properties of biomaterials, the super-hydrophobic properties of Lotus leaves are also tied to their hierarchical structure.7,56 Recently, self-cleaning building materials with super-hydrophobic surfaces that are inspired by the structure of Lotus have been developed.7 Figure 2 illustrates a water droplet sitting on a superhydrophobic surface having a contact angle of close to 178o.7 Research and development in the area of bioinspired materials and multifunctional bio-inspired materials is one of the emerging opportunities in the area of developing sustainable construction materials. Carbon Capture for Production of New Materials Carbon sequestering is one of the Grand Challenges of the 21st century.57 Many strategies for carbon sequestering including injection of CO2 to

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depleted oil wells and ocean floor have been suggested and studied.57 The use of CO2 in production of new materials can provide opportunities for locking CO2 away.3 By mimicking natural biological processes, researchers have developed biological processes to convert CO2 to solid carbonates that can potentially be used as construction materials.58 Recently, CALERA Corporation has developed a process to produce stable minerals (such as calcium and magnesium carbonates) by Mineralization via Aqueous Precipitation (MAP).59 TIS & Partners Ltd, a Japanese company, has developed a process in which CO2 is used to produce bricks.60 In this process, CO2 reacts with silica to form the initial skeleton of a porous brick. The brick is then epoxy impregnated. While in this process CO2 capture is used, performing LCA might be necessary to better quantitate the net environmental loading of this product. This class of construction materials is relatively new, and structural application of these materials might not be feasible in close future. Nonstructural applications of these materials (such as decorative concrete and sidewalks) are expected to be seen in close future. New Material Processing Techniques Despite the recent advances in material processing, material processing techniques that can ensure proper and uniform dispersion and distribution of nanoparticles within the cementitious mixtures are required. Such material processing techniques can potentially result in breakthroughs in large-scale application of advanced engineered nanoparticles. The current methods of dispersion of nanoparticles in cementitious materials are either limited to small laboratory-scale specimens or they are limited to very low dosage of nanoparticles. Only recently advanced material processing techniques such as the Green Sense Concrete,5 developed by BASF, has become available. Green Sense Concrete is developed by fundamental understanding of different aspect of concrete materials such as hydration kinetics and physical–chemical interaction of nanoparticles.5 This new technology has been used in construction of the new World Trade Center.61 Developing material processing techniques, with an emphasis on developing techniques for dispersion and incorporating engineered nanoparticles in construction materials, is an emerging opportunity in the area of sustainable construction materials.

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Physically Based Multiscale Modeling Developing “multiphysics multiscale” modeling approaches with the goal of understanding and predicting the properties of construction materials is one of the emerging opportunity in the field of sustainable construction materials1 (the term “multiphysics multiscale” is borrowed here from reference62). The two major impacts of such a multiphysics multiscale (among others) on developing sustainable materials include the following: (1) rapid characterization of new materials as they become available (or before their production)1 and (2) reducing the environmental emissions of materials by identifying the underlying mechanisms that contribute to their environmental loadings.1 If the macroscale properties of construction materials can be related to their microstructure and molecular structure, using multiphysics multiscale modeling, researchers and engineers may be able to reduce the amount of necessary experimental efforts for characterizing, predicting the long-term performance, and understanding the coupled nonlinear properties of new construction materials.1 Multiscale modeling can also provide a solution to the major problem facing the cementitious materials made with industrial byproducts: The fact that the physical and chemical properties of industrial byproducts are changing rapidly and therefore influencing the properties of cementitious materials made with these byproducts. Multiscale modeling offers a great potential in predicting the influence of these byproducts used in production of binders (e.g., used as raw materials in cement production) or used as supplementary cementitious materials (to replace the cement). Furthermore, multiphysics multiscale modeling can be used for engineering the cementitious materials so that change in molecular structure of the byproducts can be compensated by other byproducts or tailored to benefit the long-term performance of the materials. Accurate service life prediction is another area where multiphysics multiscale modeling can have significant contributions. Generally, accurate prediction of the service life of concrete infrastructure is a challenging task as concrete is an aging material, different mechanisms contribute to degradation of concrete materials, and concrete is subjected to varying boundary conditions during its service life. Currently, more advanced service life prediction models are becoming available.63 These advanced service life prediction models require

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Fig. 3. Molecular model of C-S-H – blue: oxygen of water molecules, white: hydrogen of water molecules, green: interlayer calcium ions, gray: intralayer calcium ions, yellow: silicon in silica tetrahedral, red: oxygen atoms in silica tetrahedral (courtesy of Dr H. Jennings1).

more data and more extensive experimental support compared with more traditional service life prediction models. Multiphysics multiscale modeling can be used to obtain the required data for more advanced service life prediction models, and as a larger number of properties of materials can be quantified, more advanced service life predictions that consider multiple degradation mechanisms can be developed and used. While promising, developing multiphysics multiscale modeling approaches are challenging. For more than five decades, perhaps starting with the earlier work of Powers,64 researchers have been trying to understand and quantify the microstructure of the cement paste (the term microstructure is used rather liberally herein, and it implicitly encompasses smaller length scales as well). Different models have been discussed in literature, and they provide different views of the microstructure of C-S-H or cement paste,65–67 but only recently quantitative molecular models of cement paste have become available through computer modeling and simulations (Fig. 3).68 While these contributions are significant milestones in cement science, yet there is a need for more advanced models that can take into account the interaction of pore solution with C-S-H and provide more insight to the role of pore solution on the mechanical properties and long-term performance of C-S-H.1 One of the first detailed molecular dynamic studies on the interactions of water molecules with tobermorite has been presented by Kalinichev

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Fig. 4. Schematic illustration of the mesoscale gap in multiphysics multiscale modeling of cementitious materials (courtesy of Dr. H. Jennings1).

et al. (2007).69 While structure of C-S-H is significantly more complex and disordered compared with tobermorite (or jennite),70 Kalinichev et al. (2007)69 provided significant insight to the behavior of water in nano-sized pores of C-S-H. Perhaps even more significant challenge in multiphysics multiscale modeling is bridging the gap at mesoscale and developing a comprehensive model that can link the mechanistic models at different length scales to each other.1,62 Figure 4 illustrates a plot that schematically illustrates current modeling capabilities verses complexity axis. This schematic illustration clearly shows the missing link at mesoscale modeling.62

Summary In the three infrastructure sessions of the Fourth International Congress on Ceramics (ICC4), scientists and engineers identified major challenges in developing sustainable infrastructure materials and discussed the emerging opportunities in this area. The major challenges identified in the area of sustainable construction materials include characterizing the new low carbon footprint materials as they become available, predicting the long-term performance of new materials, uncertainties associated with utilizing industrial byproducts in construction materials, dispersion of engineered nanoparticles in cementitious materials, environmental emission implications of engineered nanoparticles, and acceptance of new materials by practitioners.

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The emerging opportunities identified in the area of sustainable construction materials include utilizing innovative approaches to reduce the environmental loadings of the use stage of buildings and infrastructure, development and application of multifunctional bio-inspired materials, development of carbon sequestering construction materials, development of advanced material processing techniques to utilize available engineered nanoparticles, and development of multiphysics multiscale modeling for material characterization and predicting the long-term performance of new materials. Acknowledgments This article presents the ideas discussed in the infrastructure sessions of the Fourth International Congress on Ceramics (ICC4). More specifically this article provides ideas presented by Dr. H. Jennings, Dr. R. Moon, Mr. L. Lemay, Dr. L. Barcelo, Dr. A. Tselebidis, Mr. T. S. Rushing, Dr. M. Raimondo, and Dr. W. Vichit-Vadakan. The author is grateful for their contributions. The author also thanks Dr. K. Faber, Dr. W. J. Weiss, Mr. Greg Geiger, Mr. Mark Mecklenborg, and other members of the technical committee of ICC4. The author also acknowledges the helpful discussions with Dr. R. Ranjithan, Dr. J. Ducoste, and Dr. M. Barlaz. References 1. H. M. Jennings, “Models and Measurements with Implications to Understanding Mechanisms,” Proceedings of the 4th International Congress on Ceramics (ICC4) 2012. Chicago, IL, 2012. 2. R. Moon, J. Weiss, J. Youngblood, and P. D. Zavattieri, “Cellulose Nanomaterials an Opportunity for Cements?” Proceedings of the 4th International Congress on Ceramics (ICC4) 2012. Chicago, IL, 2012. 3. L. Lemay, “Innovations that Enhance the Sustainable Attributes of Concrete-based Materials,” Proceedings of the 4th International Congress on Ceramics (ICC4) 2012. Chicago, IL, 2012. 4. L. Barcelo, J. Kline, G. Walenta, and E. Gartner, “Belite, Calcium Sulfoaluminate and Calcium Aluminoferrite Based Clinkers, A New Way to Address the Sustainability Challenges of the Cement Industry,” Proceedings of the 4th International Congress on Ceramics (ICC4) 2012. Chicago, IL, 2012. 5. A. Tselebidis, “Sustainable Concrete,” Proceedings of the 4th International Congress on Ceramics (ICC4) 2012. Chicago, IL, 2012. 6. T. S. Rushing, “Materials Research at the U.S. Army Engineer Research and Development Center,” Proceedings of the 4th International Congress on Ceramics (ICC4) 2012. Chicago, IL, 2012. 7. M. Raimondo, “Making Super-Hydrophobic Building Materials: Static and Dynamic Behaviour of Nanostructured Surfaces,” Proceedings of the 4th International Congress on Ceramics (ICC4) 2012. Chicago, IL, 2012. 8. W. Vichit-Vadakan and J. Siramanont, “Superabsorbent Polymers in Portland Cement-Based Composites,” Proceedings of the 4th International Congress on Ceramics (ICC4) 2012. Chicago, IL, 2012.

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9. P. K. Mehta and P. J. M. Monteiro, Concrete Microstructure, Properties, and Materials, McGraw Hill, New York, 2005. 10. E. Worrell, L. Price, C. Hendricks, and L. O. Meida, “Carbon Dioxide Emissions from the Global Cement Industry,” Annu. Rev. Energy Env., 26 303–329 (2001). 11. M. Schneider, M. Romer, M. Tschudin, and H. Bolio, “Sustainable Cement Production-Present and Future,” Cem. Conc. Res., 41 [7] 642–650 (2011). 12. E. Gartner, “Industrially Interesting Approaches to “Low-CO2” Cements,” Cem. Conc. Res., 34 [9] 1489–1498 (2004). 13. H. F. W. Taylor, Cement Chemistry, Thomas Telford Services., London, 1997. 14. P. D. Tennis, M. D. A. Thomas, and W. J. Weiss, State-of-the-Art Report on Use of Limestone in Cements at Levels of up to 15% – SN3148, Portland Cement Association, Skokie, IL, 2011. 15. R. K. Mehta, “Performance of High-Volume Fly Ash Concrete in Hot Weather,” Amer. Conc. Inst., 209 47–52 (2002). 16. S. D. Wang and K. L. Scrivener, “Si-29 and Al-27 NMR Study of AlkaliActivated Slag,” Cem. Conc. Res., 33 [5] 769–774 (2003). 17. M. Criado, A. Palomo, A. Fernandez-Jimenez, and P. F. G. Banfill, “Alkali Activated Fly Ash: Effect of Admixtures on Paste Rheology,” Rheol. Acta, 48 [4] 447–455 (2009). 18. M. Nehdi, S. Mindess, and P. C. Aitcin, “Optimization of High Strength Limestone Filler Cement Mortars,” Cem. Conc. Res., 26 [6] 883–893 (1996). 19. R. U. D. Nassar and P. Soroushian, “Green and Durable Mortar Produced with Milled Waste Glass,” Mag. Conc. Res., 64 [7] 605–615 (2012). 20. T. C. Hansen, “Recycled Concrete Aggregate and Fly-Ash Produce Concrete Without Portland-Cement,” Cem. Conc. Res., 20 [3] 355–356 (1990). 21. D. P. Bentz and W. J. Weiss, Internal Curing: A 2010 State-of-the-Art Review, Vol. NISTIR 7765, National Institute of Standards and Technology, Washington, DC, 2011. 22. O. M. Jensen, “Use of Superabsorbent Polymers in Construction Materials,” Rilem Proc., 61 757–764 (2008). 23. P. Trtik, et al., “Neutron Tomography Measurements of Water Release from Superabsorbent Polymers in Cement Paste,” International RILEM Conference on Material Science, ed. W. Brameshuber, RILEM Publications SARL, Bagneux, France, Vol Iii, 77 175–185 (2010). 24. C. DiBella, C. Villani, E. Hausheer, and W. J. Weiss, “Chloride Transport Measurements for a Plain and Internally Cured Concrete Mixture,” The Economics, Performance and Sustainability of Internally Cured Concrete, Vol. SP-290, eds., A. K. Schindler, J. G. Grygar, and J. Weiss. American Concrete Institute, Farmington Hills, MI, 2012. 25. K. Raoufi and W. J. Weiss, “Corrosion and Service Life Estimates for Internally Cured Concrete,” The Economics, Performance and Sustainability of Internally Cured Concrete, Vol. SP-290, eds., A. K. Schindler, J. G. Grygar, and J. Weiss. American Concrete Institute, Farmington Hills, MI, 2012. 26. D. A. Streeter, W. H. Wolfe, and R. E. Vaughn, “Field Performance of Internally Cured Concrete Bridge Decks in New York State,” The Economics, Performance and Sustainability of Internally Cured Concrete, Vol. SP290, eds., A. K. Schindler, J. G. Grygar, and J. Weiss. American Concrete Institute, Farmington Hills, MI, 2012. 27. I. De la Varga, J. Castro, and J. Weiss, “Preliminary Findings from Research to Extend Internal Curing Concepts to Mixtures with Higher Volumes of Fly Ash,” International RILEM Conference on Material Scienceed. W. Brameshuber, RILEM Publications SARL, Bagneux, France, Vol Iii, 77 141–153 (2010). 28. L. Raki, J. J. Beaudoin, and R. Alizadeh, “Nanotechnology Applications for Sustainable Cement-Based Products,” Nanotechnology in Construction 3, Proceedings, 119–124 (2009). 29. R. Alizadeh, L. Raki, J. M. Makar, J. J. Beaudoin, and I. Moudrakovski, “Hydration of Tricalcium Silicate in the Presence of Synthetic Calcium-Silicate-Hydrate,” J. Mater. Chem., 19 [42] 7937–7946 (2009). 30. T. Sato and J. J. Beaudoin, “Effect of Nano-CaCO3 on Hydration of Cement Containing Supplementary Cementitious Materials,” Adv. Cem. Res., 23 [1] 33–43 (2011).

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