Publications
57 results found
D'Amico B, Myers RJ, Sykes J, et al., 2019, Machine learning for sustainable structures: a call for data, Structures, Vol: 19, Pages: 1-4, ISSN: 2352-0124
Buildings are the world's largest contributors to energy demand, greenhouse gases (GHG) emissions, resource consumption and waste generation. An unmissable opportunity exists to tackle climate change, global warming, and resource scarcity by rethinking how we approach building design. Structural materials often dominate the total mass of a building; therefore, a significant potential for material efficiency and GHG emissions mitigation is to be found in efficient structural design and use of structural materials.To this end, environmental impact assessment methods, such as life cycle assessment (LCA), are increasingly used. However, they risk failing to deliver the expected benefits due to the high number of parameters and uncertainty factors that characterise impacts of buildings along their lifespans. Additionally, effort and cost required for a reliable assessment seem to be major barriers to a more widespread adoption of LCA. More rapid progress towards reducing building impacts seems therefore possible by combining established environmental impact assessment methods with artificial intelligence approaches such as machine learning and neural networks.This short communication will briefly present previous attempts to employ such techniques in civil and structural engineering. It will present likely outcomes of machine learning and neural network applications in the field of structural engineering and – most importantly – it calls for data from professionals across the globe to form a fundamental basis which will enable quicker transition to a more sustainable built environment.
Myers RJ, Fishman T, Reck BK, et al., 2019, Unified Materials Information System (UMIS): an integrated material stocks and flows data structure, Journal of Industrial Ecology, Vol: 23, Pages: 222-240, ISSN: 1088-1980
Modern society depends on the use of many diverse materials. Effectively managing these materials is becoming increasingly important and complex, from the analysis of supply chains, to quantifying their environmental impacts, to understanding future resource availability. Material stocks and flows data enable such analyses, but currently exist mainly as discrete packages, with highly varied type, scope, and structure. These factors constitute a powerful barrier to holistic integration and thus universal analysis of existing and yet to be published material stocks and flows data. We present the Unified Materials Information System (UMIS) to overcome this barrier by enabling material stocks and flows data to be comprehensively integrated across space, time, materials, and data type independent of their disaggregation, without loss of information, and avoiding double counting. UMIS can therefore be applied to structure diverse material stocks and flows data and their metadata across material systems analysis methods such as material flow analysis (MFA), input‐output analysis, and life cycle assessment. UMIS uniquely labels and visualizes processes and flows in UMIS diagrams; therefore, material stocks and flows data visualized in UMIS diagrams can be individually referenced in databases and computational models. Applications of UMIS to restructure existing material stocks and flows data represented by block flow diagrams, system dynamics diagrams, Sankey diagrams, matrices, and derived using the economy‐wide MFA classification system are presented to exemplify use. UMIS advances the capabilities with which complex quantitative material systems analysis, archiving, and computation of material stocks and flows data can be performed.
Lothenbach B, Kulik DA, Matschei T, et al., 2019, Cemdata18: A chemical thermodynamic database for hydrated Portland cements and alkali-activated materials, Cement and Concrete Research, Vol: 115, Pages: 472-506, ISSN: 0008-8846
Li J, Geng G, Myers R, et al., 2019, The chemistry and structure of calcium (alumino) silicate hydrate: A study by XANES, ptychographic imaging, and wide- and small-angle scattering, Cement and Concrete Research, Vol: 115, Pages: 367-378, ISSN: 0008-8846
Geng G, Myers RJ, Yu Y-S, et al., 2018, Synchrotron X-ray nanotomographic and spectromicroscopic study of the tricalcium aluminate hydration in the presence of gypsum, Cement and Concrete Research, Vol: 111, Pages: 130-137, ISSN: 0008-8846
The rheology of modern Portland cement (PC) concrete critically depends on the correct dosage of gypsum (calcium sulfate hydrate) to control the hydration of the most reactive phase - tricalcium aluminate (C3A). The underlying physio-chemical mechanism, however, remains unsolved mainly due to the lack of high-spatial-resolved and chemistry-sensitive characterization of the C3A dissolution frontier. Here, we fill this gap by integrating synchrotron-radiation based crystallographic, photon-energy-dependent spectroscopic and high-resolution morphological studies of the C3A hydration product layer. We propose that ettringite (6CaO·Al2O3·SO3·32H2O) is the only hydration product after the initial reaction period and before complete gypsum dissolution. We quantify the 2D and 3D morphology of the ettringite network, e.g. the packing density of ettringite at various surface locations and the surface dissolution heterogeneity. Our results show no trace of a rate-controlling diffusion barrier. We expect our work to have significant impact on modeling the kinetics and morphological evolution of PC hydration.
Kirchheim AP, Rodríguez ED, Myers RJ, et al., 2018, Effect of gypsum on the early hydration of cubic and Na-doped orthorhombic tricalcium aluminate., Materials (Basel, Switzerland), Vol: 11, ISSN: 1996-1944
The tricalcium aluminate (C₃A) and sulfate content in cement influence the hydration chemistry, setting time and rheology of cement paste, mortar and concrete. Here, in situ experiments are performed to better understand the effect of gypsum on the early hydration of cubic (cub-)C₃A and Na-doped orthorhombic (orth-)C₃A. The isothermal calorimetry data show that the solid-phase assemblage produced by the hydration of C₃A is greatly modified as a function of its crystal structure type and gypsum content, the latter of which induces non-linear changes in the heat release rate. These data are consistent with the in situ X-ray diffraction results, which show that a higher gypsum content accelerates the consumption of orth-C₃A and the subsequent precipitation of ettringite, which is contrary to the cub-C₃A system where gypsum retarded the hydration rate. These in situ results provide new insight into the relationship between the chemistry and early-age properties of cub- and orth-C₃A hydration and corroborate the reported ex situ findings of these systems.
Hertwich E, Heeren N, Kuczenski B, et al., 2018, Nullius in Verba1: Advancing Data Transparency in Industrial Ecology, Journal of Industrial Ecology, Vol: 22, Pages: 6-17, ISSN: 1088-1980
With the growth of the field of industrial ecology (IE), research and results have increased significantly leading to a desire for better utilization of the accumulated data in more sophisticated analyses. This implies the need for greater transparency, accessibility, and reusability of IE data, paralleling the considerable momentum throughout the sciences. The Data Transparency Task Force (DTTF) was convened by the governing council of the International Society for Industrial Ecology in late 2016 to propose best‐practice guidelines and incentives for sharing data. In this article, the members of the DTTF present an overview of developments toward transparent and accessible data within the IE community and more broadly. We argue that increased transparency, accessibility, and reusability of IE data will enhance IE research by enabling more detailed and reproducible research, and also facilitate meta‐analyses. These benefits will make the results of IE work more timely. They will enable independent verification of results, thus increasing their credibility and quality. They will also make the uptake of IE research results easier within IE and in other fields as well as by decision makers and sustainability practitioners, thus increasing the overall relevance and impact of the field. Here, we present two initial actions intended to advance these goals: (1) a minimum publication requirement for IE research to be adopted by the Journal of Industrial Ecology; and (2) a system of optional data openness badges rewarding journal articles that contain transparent and accessible data. These actions will help the IE community to move toward data transparency and accessibility. We close with a discussion of potential future initiatives that could build on the minimum requirements and the data openness badge system.
Fishman T, Myers R, Rios O, et al., 2018, Implications of emerging vehicle technologies on rare earth supply and demand in the United States, Resources, Vol: 7, Pages: 1-15, ISSN: 2079-9276
We explore the long-term demand and supply potentials of rare earth elements in alternative energy vehicles (AEVs) in the United States until 2050. Using a stock-flow model, we compare a baseline scenario with scenarios that incorporate an exemplary technological innovation: a novel aluminum–cerium–magnesium alloy. We find that the introduction of the novel alloy demonstrates that even low penetration rates can exceed domestic cerium production capacity, illustrating possible consequences of technological innovations to material supply and demand. End-of-life vehicles can, however, overtake domestic mining as a source of materials, calling for proper technologies and policies to utilize this emerging source. The long-term importing of critical materials in manufactured and semi-manufactured products shifts the location of material stocks and hence future secondary supply of high-value materials, culminating in a double benefit to the importing country. This modeling approach is adaptable to the study of varied scenarios and materials, linking technologies with supply and demand dynamics in order to understand their potential economic and environmental consequences
Ortaboy S, Li J, Geng G, et al., 2017, Effects of CO2 and temperature on the structure and chemistry of C–(A–)S–H investigated by Raman spectroscopy, RSC Adv., Vol: 7, Pages: 48925-48933
<p>Calcium (alumino)silicate hydrate (C–(A–)S–H) is the critical binding phase in modern Portland cement-based concrete, yet the relationship between its structure and stoichiometry is not completely understood.</p>
Myers RJ, Geng G, Rodriguez ED, et al., 2017, Solution chemistry of cubic and orthorhombic tricalcium aluminate hydration, Cement and Concrete Research, Vol: 100, Pages: 176-185, ISSN: 0008-8846
Geng G, Myers RJ, Qomi MJA, et al., 2017, Densification of the interlayer spacing governs the nanomechanical properties of calcium-silicate-hydrate, Scientific Reports, Vol: 7, Pages: 1-8, ISSN: 2045-2322
Calciuam-silicate-hydrate (C-S-H) is the principal binding phase in modern concrete. Molecular simulations imply that its nanoscale stiffness is ‘defect-driven’, i.e., dominated by crystallographic defects such as bridging site vacancies in its silicate chains. However, experimental validation of this result is difficult due to the hierarchically porous nature of C-S-H down to nanometers. Here, we integrate high pressure X-ray diffraction and atomistic simulations to correlate the anisotropic deformation of nanocrystalline C-S-H to its atomic-scale structure, which is changed by varying the Ca-to-Si molar ratio. Contrary to the ‘defect-driven’ hypothesis, we clearly observe stiffening of C-S-H with increasing Ca/Si in the range 0.8 ≤ Ca/Si ≤ 1.3, despite increasing numbers of vacancies in its silicate chains. The deformation of these chains along the b-axis occurs mainly through tilting of the Si-O-Si dihedral angle rather than shortening of the Si-O bond, and consequently there is no correlation between the incompressibilities of the a- and b-axes and the Ca/Si. On the contrary, the intrinsic stiffness of C-S-H solid is inversely correlated with the thickness of its interlayer space. This work provides direct experimental evidence to conduct more realistic modelling of C-S-H-based cementitious material.
Myers RJ, Bernal SA, Provis JL, 2017, Phase diagrams for alkali-activated slag binders, Cement and Concrete Research, Vol: 95, Pages: 30-38, ISSN: 0008-8846
Phase diagrams for alkali-activated slag (AAS) binders are simulated at (metastable) thermodynamic equilibrium, spanning the relevant compositional envelopes for these materials. The phase diagrams are generally consistent with experimental observations in the literature, dominated by calcium (alkali) aluminosilicate hydrate (C-(N-)A-S-H) gels and Mg-Al layered double hydroxides. Relationships between the stabilities of the predicted solid phase assemblages, pore solution compositions, and the bulk chemical composition are identified, yielding an improved understanding of AAS binder chemistry. Strätlingite is predicted at low to intermediate Si concentrations and at high Al content, while zeolites (and thus most likely also disordered alkali-aluminosilicate (hydrate) gels) tend to precipitate at higher concentrations of both Si and Al; katoite and AFm-type phases are stabilised at intermediate levels of CaO + Al2O3 + MgO. The application of these results in designing AAS binders can enable the phase assemblages and chemical properties of these materials to be more precisely controlled.
Geng G, Myers RJ, Kilcoyne ALD, et al., 2017, CaL2,3-edge near edge X-ray absorption fine structure of tricalcium aluminate, gypsum, and calcium (sulfo)aluminate hydrates, American Mineralogist, Vol: 102, Pages: 900-908, ISSN: 0003-004X
Geng G, Myers RJ, Li J, et al., 2017, Aluminum-induced dreierketten chain cross-links increase the mechanical properties of nanocrystalline calcium aluminosilicate hydrate., Scientific reports, Vol: 7, Pages: 44032-44032, ISSN: 2045-2322
The incorporation of Al and increased curing temperature promotes the crystallization and cross-linking of calcium (alumino)silicate hydrate (C-(A-)S-H), which is the primary binding phase in most contemporary concrete materials. However, the influence of Al-induced structural changes on the mechanical properties at atomistic scale is not well understood. Herein, synchrotron radiation-based high-pressure X-ray diffraction is used to quantify the influence of dreierketten chain cross-linking on the anisotropic mechanical behavior of C-(A-)S-H. We show that the ab-planar stiffness is independent of dreierketten chain defects, e.g. vacancies in bridging tetrahedra sites and Al for Si substitution. The c-axis of non-cross-linked C-(A-)S-H is more deformable due to the softer interlayer opening but stiffens with decreased spacing and/or increased zeolitic water and Ca2+ of the interlayer. Dreierketten chain cross-links act as 'columns' to resist compression, thus increasing the bulk modulus of C-(A-)S-H. We provide the first experimental evidence on the influence of the Al-induced atomistic configurational change on the mechanical properties of C-(A-)S-H. Our work advances the fundamental knowledge of C-(A-)S-H on the lowest level of its hierarchical structure, and thus can impact the way that innovative C-(A-)S-H-based cementitious materials are developed using a 'bottom-up' approach.
Myers RJ, Geng G, Li J, et al., 2017, Role of Adsorption Phenomena in Cubic Tricalcium Aluminate Dissolution, Langmuir: the ACS journal of surfaces and colloids, Vol: 33, Pages: 45-55, ISSN: 0743-7463
The workability of fresh Portland cement (PC) concrete critically depends on the reaction of the cubic tricalcium aluminate (C3A) phase in Ca- and S-rich pH >12 aqueous solution, yet its rate-controlling mechanism is poorly understood. In this article, the role of adsorption phenomena in C3A dissolution in aqueous Ca-, S-, and polynaphthalene sulfonate (PNS)-containing solutions is analyzed. The zeta potential and pH results are consistent with the isoelectric point of C3A occurring at pH ∼12 and do not show an inversion of its electric double layer potential as a function of S or Ca concentration, and PNS adsorbs onto C3A, reducing its zeta potential to negative values at pH >12. The S and Ca K-edge X-ray absorption spectroscopy (XAS) data obtained do not indicate the structural incorporation or specific adsorption of SO42- on the partially dissolved C3A solids analyzed. Together with supporting X-ray ptychography and scanning electron microscopy results, a model for C3A dissolution inhibition in hydrated PC systems is proposed whereby the formation of an Al-rich leached layer and the complexation of Ca-S ion pairs onto this leached layer provide the key inhibiting effect(s). This model reconciles the results obtained here with the existing literature, including the inhibiting action of macromolecules such as PNS and polyphosphonic acids upon C3A dissolution. Therefore, this article advances the understanding of the rate-controlling mechanism in hydrated C3A and thus PC systems, which is important to better controlling the workability of fresh PC concrete.
Myers RJ, Lothenbach B, Bernal SA, et al., 2016, Corrigendum to “Thermodynamic modelling of alkali-activated slag-based cements” [Appl. Geochem. 61 (2015) 233–247], Applied Geochemistry, Vol: 67, Pages: 186-186, ISSN: 0883-2927
Myers RJ, Lothenbach B, Bernal SA, et al., 2015, Thermodynamic modelling of alkali-activated slag cements, APPLIED GEOCHEMISTRY, Vol: 61, Pages: 233-247, ISSN: 0883-2927
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- Citations: 145
Myers RJ, Bernal SA, Gehman JD, et al., 2015, The Role of Al in Cross-Linking of Alkali-Activated Slag Cements, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 98, Pages: 996-1004, ISSN: 0002-7820
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- Citations: 155
Bernal SA, Provis JL, Myers RJ, et al., 2015, Role of carbonates in the chemical evolution of sodium carbonate-activated slag binders, MATERIALS AND STRUCTURES, Vol: 48, Pages: 517-529, ISSN: 1359-5997
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- Citations: 159
Myers RJ, L'Hopital E, Provis JL, et al., 2015, Effect of temperature and aluminium on calcium (alumino)silicate hydrate chemistry under equilibrium conditions, Cement and Concrete Research, Vol: 68, Pages: 83-93, ISSN: 0008-8846
There exists limited information regarding the effect of temperature on the structure and solubility of calcium aluminosilicate hydrate (C–A–S–H). Here, calcium (alumino)silicate hydrate (C–(A–)S–H) is synthesised at Ca/Si = 1, Al/Si ≤ 0.15 and equilibrated at 7–80 °C. These systems increase in phase-purity, long-range order, and degree of polymerisation of C–(A–)S–H chains at higher temperatures; the most highly polymerised, crystalline and cross-linked C–(A–)S–H product is formed at Al/Si = 0.1 and 80 °C. Solubility products for C–(A–)S–H were calculated via determination of the solid-phase compositions and measurements of the concentrations of dissolved species in contact with the solid products, and show that the solubilities of C–(A–)S–H change slightly, within the experimental uncertainty, as a function of Al/Si ratio and temperature between 7 °C and 80 °C. These results are important in the development of thermodynamic models for C–(A–)S–H to enable accurate thermodynamic modelling of cement-based materials.
Myers RJ, L'Hopital E, Provis JL, et al., 2015, Composition-solubility-structure relationships in calcium (alkali) aluminosilicate hydrate (C-(N,K-)A-S-H), DALTON TRANSACTIONS, Vol: 44, Pages: 13530-13544, ISSN: 1477-9226
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- Citations: 51
Myers RJ, Bernal SA, Provis JL, 2014, A thermodynamic model for C-(N-)A-S-H gel: CNASH_ss. Derivation and validation, Cement and Concrete Research, Vol: 66, Pages: 27-47, ISSN: 0008-8846
The main reaction product in Ca-rich alkali-activated cements and hybrid Portland cement (PC)-based materials is a calcium (alkali) aluminosilicate hydrate (C-(N-)A-S-H) gel. Thermodynamic models without explicit definitions of structurally-incorporated Al species have been used in numerous past studies to describe this gel, but offer limited ability to simulate the chemistry of blended PC materials and alkali-activated cements. Here, a thermodynamic model for C-(N-)A-S-H gel is derived and parameterised to describe solubility data for the CaO–(Na2O,Al2O3)–SiO2–H2O systems and alkali-activated slag (AAS) cements, and chemical composition data for C-A-S-H gels. Simulated C-(N-)A-S-H gel densities and molar volumes are consistent with the corresponding values reported for AAS cements, meaning that the model can be used to describe chemical shrinkage in these materials. Therefore, this model can provide insight into the chemistry of AAS cements at advanced ages, which is important for understanding the long-term durability of these materials.
Bernal SA, Nicolas RS, Myers RJ, et al., 2014, MgO content of slag controls phase evolution and structural changes induced by accelerated carbonation in alkali-activated binders, CEMENT AND CONCRETE RESEARCH, Vol: 57, Pages: 33-43, ISSN: 0008-8846
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- Citations: 294
Myers RJ, L'Hopital E, Provis JL, et al., 2014, EFFECT OF TEMPERATURE, ALKALI AND ALUMINIUM ON CALCIUM ALUMINOSILICATE HYDRATE CHEMISTRY UNDER EQUILIBRIUM CONDITIONS, 2nd International Conference on Advances in Chemically-Activated Materials (CAM-China), Publisher: R I L E M PUBLICATIONS, Pages: 302-308, ISSN: 1461-1147
Myers RJ, Bernal SA, San Nicolas R, et al., 2013, Generalized Structural Description of Calcium-Sodium Aluminosilicate Hydrate Gels: The Cross-Linked Substituted Tobermorite Model, LANGMUIR, Vol: 29, Pages: 5294-5306, ISSN: 0743-7463
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- Citations: 316
Provis JL, Hajimohammadi A, White CE, et al., 2013, Nanostructural characterization of geopolymers by advanced beamline techniques, Publisher: ELSEVIER SCI LTD, Pages: 56-64, ISSN: 0958-9465
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- Citations: 33
Provis JL, Myers RJ, White CE, et al., 2012, X-ray microtomography shows pore structure and tortuosity in alkali-activated binders, CEMENT AND CONCRETE RESEARCH, Vol: 42, Pages: 855-864, ISSN: 0008-8846
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- Citations: 337
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