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This paper presents a semi‐quantitative review of measures to achieve net‐zero greenhouse gas emissions ("decarbonization") in the cementitious materials (CMs) cycle, that is, activities directly related to cement spanning extraction through to end of life. It focuses on the United Kingdom and Europe in order to relate these measures, comprising emissions, energy, and material efficiency, to the policy landscape. We summarize our findings in an annotated CMs cycle, produced by reconciling the diverse yet relatively underdeveloped literature on the topic, to quantify decarbonization potentials of the various measures in a systematic manner. We find that decarbonization measures with significant potential exist along the entire CMs cycle, although upstream (of use), energy, and emission efficiency measures are better quantified than downstream (of use) and material efficiency measures. Notably, the decarbonization potentials of recycling technologies and the ways in which technological advancements may transform the CMs cycle and thus the stocks, flows, and processing of materials, as well as effectiveness of decarbonization measures, are poorly understood. Therefore, this paper provides a basis to systematically understand the effects of emissions, energy, and material efficiency measures on decarbonization of the CMs cycle and, in this context, the interplay between technology, economic actors, and policy. This article met the requirements for a gold–gold JIE data openness badge described at http://jie.click/badges. [ABSTRACT FROM AUTHOR]

Summary: 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. [ABSTRACT FROM AUTHOR]

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 (C 3 A). The underlying physio-chemical mechanism, however, remains unsolved mainly due to the lack of high-spatial-resolved and chemistry-sensitive characterization of the C 3 A dissolution frontier. Here, we fill this gap by integrating synchrotron-radiation based crystallographic, photon-energy-dependent spectroscopic and high-resolution morphological studies of the C 3 A hydration product layer. We propose that ettringite (6CaO·Al 2 O 3 ·SO 3 ·32H 2 O) 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. [ABSTRACT FROM AUTHOR]

This paper presents a solution chemistry-focused analysis of orthorhombic and cubic tricalcium aluminate (orth-C 3 A and cub-C 3 A, respectively) hydration. It is shown that the different solubilities of cub- and orth-C 3 A influence the bulk aqueous Ca to Al concentration ratio and the C 3 A/solution interface chemistry. The results are consistent with the bulk solution chemistry controlling orth-C 3 A dissolution, and with cub-C 3 A dissolution controlled by the formation of an Al-rich leached layer and adsorption of Ca‑sulfur ion pair complexes onto this layer. The polynaphthalene sulfonate-based admixture used here is identified to modify the solution chemistry and retard cub-C 3 A dissolution. Strategies to inhibit C 3 A dissolution in Portland cement are discussed. [ABSTRACT FROM AUTHOR]

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 + Al 2 O 3 + 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. [ABSTRACT FROM AUTHOR]

Tricalcium aluminate (cement clinker phase), gypsum, katoite, ettringite, and calcium monosulfoaluminate hydrate (abbreviated as kuzelite) are the major minerals in the hydration reaction of tricalcium aluminate in the presence of gypsum and have critical impacts on the kinetics and thermo- dynamics of early-age cement hydration mechanisms. Here, spectroscopic analysis of these minerals is conducted using scanning transmission X -ray microscopy (STXM). Their Ca L2,3-edge near edge X-ray absorption fine structure (NEXAFS) spectra are measured and correlated to the known Ca coordination environments. The results indicate that these minerals have unique Ca environments that can be differentiated from one another based on the intensities and positions of the absorption peaks at 346.5-348.5 and 350.5-351.5 eV. It is concluded that Ca in tricalcium aluminate (cubic and orthorhombic polymorphs) and katoite is in cubic-like coordination with negative 10Dq, whereas Ca is in an octahedral-like coordination with positive 10Dq in ettringite, gypsum, and kuzelite. For tricalcium aluminate, the Ca atoms in both polymorphs are in similar chemical environments with slightly more distortion in the orthorhombic polymorph. As a common issue in STXM experiments, absorption saturation of NEXAFS spectra is also investigated. It is demonstrated that the optical density difference between pre- and post-edge absorption levels provides a reliable indication of the sample thickness in the systems studied. The present work provides a reference for the STXM study of the calcium (sulfo)aluminate reactions in cement hydration and natural aqueous environments, and in the former case, provides a more complete understanding of a system that may serve as a low-C alternative to Portland cement. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper presents a thermodynamic modelling analysis of alkali-activated slag-based cements, which are high performance and potentially low-CO 2 binders relative to Portland cement. The thermodynamic database used here contains a calcium (alkali) aluminosilicate hydrate ideal solid solution model (CNASH_ss), alkali carbonate and zeolite phases, and an ideal solid solution model for a hydrotalcite-like Mg–Al layered double hydroxide phase. Simulated phase diagrams for NaOH- and Na 2 SiO 3 -activated slag-based cements demonstrate the high stability of zeolites and other solid phases in these materials. Thermodynamic modelling provides a good description of the chemical compositions and types of phases formed in Na 2 SiO 3 -activated slag cements over the most relevant bulk chemical composition range for these cements, and the simulated volumetric properties of the cement paste are consistent with previously measured and estimated values. Experimentally determined and simulated solid phase assemblages for Na 2 CO 3 -activated slag cements were also found to be in good agreement. These results can be used to design the chemistry of alkali-activated slag-based cements, to further promote the uptake of this technology and valorisation of metallurgical slags. [ABSTRACT FROM AUTHOR]

The interplay between the solubility, structure and chemical composition of calcium (alkali) aluminosilicate hydrate (C-(N,K-)A-S-H) equilibrated at 50 °C is investigated in this paper. The tobermorite-like C-(N,K-)A-S-H products are more crystalline in the presence of alkalis, and generally have larger basal spacings at lower Ca/Si ratios. Both Na and K are incorporated into the interlayer space of the C-(N,K-)A-S-H phases, with more alkali uptake observed at higher alkali and lower Ca content. No relationship between Al and alkali uptake is identified at the Al concentrations investigated (Al/Si ≤ 0.1). More stable C-(N,K-)A-S-H is formed at higher alkali content, but this factor is only significant in some samples with Ca/Si ratios ≤1. Shorter chain lengths are formed at higher alkali and Ca content, and cross-linking between (alumino)silicate chains in the tobermorite-like structure is greatly promoted by increasing alkali and Al concentrations. The calculated solubility products do not depend greatly on the mean chain length in C-(N,K-)A-S-H at a constant Ca/(Al + Si) ratio, or the Al/Si ratio in C-(N,K-)A-S-H. These results are important for understanding the chemical stability of C-(N,K-)A-S-H, which is a key phase formed in the majority of cements and concretes used worldwide. [ABSTRACT FROM AUTHOR]

The structural development of a calcium (sodium) aluminosilicate hydrate (C-(N-)A-S-H) gel system, obtained through the reaction of sodium metasilicate and ground granulated blast furnace slag, is assessed by high-resolution 29Si and 27Al MAS NMR spectroscopy during the first 2 yr after mixing. The cements formed primarily consist of C-(N-)A-S-H gels, with hydrotalcite and disordered alkali aluminosilicate gels also identified in the solid product assemblages. Deconvolution of the 27Al MAS NMR spectra enables the identification of three distinct tetrahedral Al sites, consistent with the 29Si MAS NMR data, where Q³(1Al), Q4(3Al), and Q4(4Al) silicate sites are identified. These results suggest significant levels of crosslinking in the C-(N-)A-S-H gel and the presence of an additional highly polymerized aluminosilicate product. The mean chain length, extent of cross-linking, and Al/Si ratio of the C-(N-)A-S-H gel decrease slightly over time. The de-crosslinking effect is explained by the key role of Al in mixed cross-linked/non-cross-linked C-(N-)A-S-H gels, because the cross-linked components have much lower Al-binding capacities than the noncross-linked components. These results show that the aluminosilicate chain lengths and chemical compositions of the fundamental structural components in C-(N-)A-S-H gels vary in a way that is not immediately evident from the overall bulk chemistry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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–(Na 2 O,Al 2 O 3 )–SiO 2 –H 2 O 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. [ABSTRACT FROM AUTHOR]

Abstract: Durability of alkali-activated binders is of vital importance in their commercial application, and depends strongly on microstructure and pore network characteristics. X-ray microtomography (μCT) offers, for the first time, direct insight into microstructural and pore structure characteristics in three dimensions. Here, μCT is performed on a set of sodium metasilicate-activated fly ash/slag blends, using a synchrotron beamline instrument. Segmentation of the samples into pore and solid regions is then conducted, and pore tortuosity is calculated by a random walker method. Segmented porosity and diffusion tortuosity are correlated, and vary as a function of slag content (slag addition reduces porosity and increases tortuosity), and sample age (extended curing gives lower porosity and higher tortuosity). This is particularly notable for samples with ≥50% slag content, where a space-filling calcium (alumino)silicate hydrate gel provides porosity reductions which are not observed for the sodium aluminosilicate (‘geopolymer’) gels which do not chemically bind water of hydration. [Copyright &y& Elsevier]

Urban development is a key driver of global biodiversity loss. "Green" infrastructure is integrated to offset some impacts of development on ecosystem quality by supporting urban biodiversity, a prominent example being green roofs. The effects of green infrastructures on urban biodiversity are not well understood and poorly included in life cycle assessment (LCA) methodology. Here, we present a novel methodology that quantifies the local impact of green infrastructures on terrestrial biodiversity—demonstrated here for sedum roofs in London, UK—and integrates within LCA. It relates energy provision by plants to the metabolic requirements of animals to determine what species richness (number of species) and species abundance (number of individuals) are supported. We demonstrate this methodology using a case study, comparing the life cycle impact of developing 18 buildings, with either asphalt concrete or sedum roofs, on ecosystem quality. We found the sedum roofs (0.018 km2) support 53 species (673 individuals), equivalent to 1.3% of the development's life cycle impacts on ecosystem quality. Complete offsetting requires considerable reduction in transport use throughout the development's lifetime, and lower environmental impact material selection during construction (contributing 98% and 2%, respectively). The results indicate sedum roofs offer minor impact mitigation capacities in the context of urban development, and this capacity is limited for all green infrastructures by species richness in local species pools. This paper demonstrates the potential and limitations of quantifying terrestrial biodiversity offsets offered by green infrastructures alongside urbanization, and the need for realistic expectations of what role it might play in sustainable urban design. [ABSTRACT FROM AUTHOR]

At a time of system shocks, significant underlying challenges are revealed in current approaches to delivering infrastructure, including that infrastructure users in many societies feel distant from nature. We set out a research agenda on systems approaches to infrastructure, drawing on ten years of interdisciplinary work on operating infrastructure, infrastructure interventions and lifecycles. Research insights and directions on complexity, systems integration, data-driven systems engineering, infrastructure life-cycles, and the transition towards zero pollution are summarised. This work identifies a need to better understand the natural and societal impacts of infrastructure interventions under uncertainty. We argue for a change in current approaches to infrastructure: starting from the natural environment and its resources, encompassing societal use of infrastructure and the supporting infrastructure assets and services. To support such proposed new systems approaches to infrastructure, researchers need to develop novel modelling methods, forms of model integration, and multi-criteria indicators. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Socioeconomic demand for natural capital is causing catastrophic losses of biodiversity and ecosystem functionality, most notably in regions where socioeconomic‐and eco‐systems compete for natural capital, e.g., energy (animal or plant matter). However, a poor quantitative understanding of what natural capital is needed to support biodiversity in ecosystems, while at the same time satisfy human development needs—those associated with human development within socioeconomic systems—undermines our ability to sustainably manage global stocks of natural capital. Here we describe a novel concept and accompanying methodology (relating the adult body mass of terrestrial species to their requirements for land area, water, and energy) to quantify the natural capital needed to support terrestrial species within ecosystems, analogous to how natural capital use by humans is quantified in a socioeconomic context. We apply this methodology to quantify the amount of natural capital needed to support species observed using a specific surveyed site in Scotland. We find that the site can support a larger assemblage of species than those observed using the site; a primary aim of the rewilding project taking place there. This method conceptualises, for the first time, a comprehensive "dual‐system" approach: modelling natural capital use in socioeconomic‐and eco‐systems simultaneously. It can facilitate the management of natural capital at the global scale, and in both the conservation and creation (e.g., rewilding) of biodiversity within managed ecosystems, representing an advancement in determining what socioeconomic trade‐offs are needed to achieve contemporary conservation targets alongside ongoing human development. [ABSTRACT FROM AUTHOR]

Cements based on magnesium oxide (MgO) and reactive (alumino-)silicates (xSiO 2 -yAl 2 O 3) have drawn increasing attention owing to their potential to be produced using raw materials with low CO 2 emissions. This study examines how the phase assemblages and compressive strengths of magnesia (alumino-)silicate cements are influenced by the addition of sodium hexametaphosphate (NaHMP) and sodium carbonate (Na 2 CO 3). Cement paste samples with a Mg/Si molar ratio of 1.5 and Al/Si molar ratios of 0 and 1.0 were prepared using microsilica (SF) and metakaolin (MK), respectively, and investigated using SEM, TGA, XRD, and 29Si, 27Al, 31P, and 13C MAS NMR. The results showed that the addition of NaHMP and sodium carbonate enhanced the reactivity of the raw materials in the Al-free MgO-SF systems, with magnesium silicate hydrate (M-S-H) being the primary hydrated phase. After 91 days, the degrees of reaction of microsilica were ∼86% and 96% for systems containing 0 and 2.5 wt % Na 2 CO 3 , respectively. In contrast, the reactivity of metakaolin in the Al-containing MgO-MK systems was limited to ∼53%, irrespective of Na 2 CO 3 addition, likely due to the excess sodium hexametaphosphate covering the surface of MK. Here, the main reaction products were magnesium aluminosilicate hydrate (M-A-S-H) and hydrotalcite (Mg 6 Al 2 CO 3 (OH) 16 ·4(H 2 O))-like phases. Despite the MgO-SF systems displaying higher degree of reaction than the MgO-MK systems, the latter exhibited higher compressive strength. Sodium carbonate increased the compressive strength of the MgO-SF systems but decreased that of the MgO-MK systems. Thermodynamic modelling was also carried out and the results generally agreed with the phase formation observed with XRD and solid-state NMR. • Coupled NaHMP + Na2CO3 additives fasten the formation of M-S-H. • Coupled NaHMP + Na2CO3 additives improve the compressive strength of MgO–SiO2 binders. • NaHMP + Na2CO3 can easily be overdosed. • NaHMP + Na2CO3 below 2 wt % is recommended. [ABSTRACT FROM AUTHOR]

Abstract: The structural development and carbonation resistance of three silicate-activated slags (AAS) with varying MgO contents (<7.5wt.%) are reported. AAS with lower MgO content reacts faster at early age, forming gismondine and C-A-S-H type gels, while in slags with higher MgO content (>5%), hydrotalcite is identified as the main secondary product in addition to C–A–S–H. Higher extent of reaction and reduced Al incorporation in the C–S–H product are observed with higher MgO content in the slag. These gel chemistry effects, and particularly the formation of hydrotalcite, seem to reduce the susceptibility to carbonation of AAS produced with higher MgO contents, as hydrotalcite appears to act as an internal CO2 sorbent. This is evidenced by an inverse relationship between natural carbonation depth and slag MgO content, for paste samples formulated at constant water/binder ratio. Thus, the carbonation performance of AAS can be enhanced by controlling the chemistry of the precursors. [Copyright &y& Elsevier]

The magnesium and sodium sulfate attacks on Portland cement paste in the presence of applied electric fields were studied, and the mineralogical alterations were investigated by both experiments and thermodynamic modeling. When an electric current flows out of the cement paste, the electric migration of ions induced sulfate ingress and decalcification. Compared with the specimen exposed to Na 2 SO 4 , that exposed to MgSO 4 for 28 d proceeded to a later degradation stage, which is characterized by the decomposition of ettringite, portlandite, and AFm phases, and the formation of CaSO 4. Thermodynamic modeling indicates a neutralization process induced by the electric migration of OH−, which is potentially responsible for the decomposition of ettringite. When an electric current flows into the cement paste, the Mg2+ and Na+ showed different migration behavior. Mg2+ was incorporated to form brucite and M-S-H–like products in a shallow area (~100 μm) on the surface of the specimen, whilst a part of the Na+ could be bonded to form Na-rich silica gel with the other part penetrating through the specimen. By coupling the pore solution chemistry obtained from thermodynamic modeling with the Nernst-Planck equation, the migration behaviors of the ionic species (SO 4 2-, Mg2+, and Na+) were analyzed. [ABSTRACT FROM AUTHOR]

[Display omitted] • BiOI microflower/Bi metal junctions were grown using a solvothermal process. • Their photocatalytic activity towards NO was examined under UVA and visible light. • The effect of Bi particle size on the activity, from the nano- to micron-scale, was examined. • The nanoparticulate Bi sample showed an NO conversion of ∼26% under visible light. • This visible light activity was > 6 times higher than a commercial TiO 2 benchmark. Herein, we investigate the effect of Bi particle size in BiOI/Bi junctions on their photocatalytic function towards NO gas. BiOI microflowers (BiOI) and BiOI microflowers decorated with micron-sized Bi particles (BiOI/Bi MPs) were produced by a solvothermal method. BiOI decorated with nano-sized Bi particles (BiOI/Bi NPs) were produced by a reduction process. All samples were physically characterised by XRD, FT-IR, SEM, HR-TEM coupled with EDX analysis, DR-UV–visible and PL spectroscopy and functionally characterised by photocatalytic testing towards NO gas, TAS and EPR spectroscopy. Their photocatalytic activity towards NO gas was measured following ISO protocol (ISO 22197–1:2016). The best performing BiOI-based sample was BiOI/Bi NPs, showing NO and NO x conversion efficiencies of ∼33 and ∼11% under UVA light, and ∼26 and ∼8.1% under visible light, respectively. The BiOI and BiOI/Bi MPs samples showed significantly lower activities, displaying overall NO x conversion efficiencies of ∼3.5 and ∼0.8% under UVA light, respectively. Importantly, the best performing BiOI/Bi NPs samples showed visible light activity that was at least 6 times higher than that of a commercial TiO 2 benchmark (CristalACTiVTM PC-S7). TAS measurements showed that charge carriers were significantly longer lived in the BiOI/Bi NPs sample (t 50% from 10 μs of ∼90 μs) than the BiOI and BiOI/Bi MPs samples (t 50% from 10 μs of ∼50 μs). This was attributed to the significant degree of interfacial contact formed between Bi and BiOI in the BiOI/Bi NPs sample, which enhanced charge carrier separation. EPR studies showed that this interfacial contact between BiOI and Bi likely promoted the formation of V O , which may have contributed to enhancement seen in photocatalytic activity in the BiOI/Bi junction. [ABSTRACT FROM AUTHOR]

Abstract Thermodynamic modelling can reliably predict hydrated cement phase assemblages and chemical compositions, including their interactions with prevailing service environments, provided an accurate and complete thermodynamic database is used. Here, we summarise the Cemdata18 database, which has been developed specifically for hydrated Portland, calcium aluminate, calcium sulfoaluminate and blended cements, as well as for alkali-activated materials. It is available in GEMS and PHREEQC computer program formats, and includes thermodynamic properties determined from various experimental data published in recent years. Cemdata18 contains thermodynamic data for common cement hydrates such as C-S-H, AFm and AFt phases, hydrogarnet, hydrotalcite, zeolites, and M-S-H that are valid over temperatures ranging from 0 to at least 100 °C. Solid solution models for AFm, AFt, C-S-H, and M-S-H are also included in the Cemdata18 database. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: 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. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) enables the production of structural components with topologically optimised geometries thus leading to significant self-weight reductions for a given load-carrying capacity. A common question arises regarding the environmental performance of WAAM structural components in comparison with conventional steel structural components. Thus, a comparative cradle-to-gate life cycle assessment has been conducted where the environmental impact of producing a topologically optimised WAAM steel beam is compared with that of producing a conventional hot-rolled steel I-beam. The beams are 2 m long, simply-supported and loaded vertically at midspan. The impact of using either carbon steel or stainless steel is investigated. The results demonstrate that the carbon steel and stainless steel WAAM beams have 7% and 24%, respectively, lower climate change impact than the corresponding I-beams. It is concluded that WAAM can lead to lower CO 2 -eq. emissions than conventional hot-rolling, provided that mass reductions of the order of 50% (which are readily attainable) can be achieved by employing WAAM in conjunction with, for instance, topology optimisation. Furthermore, it is shown that the shielding gas contributes greatly to the environmental impact of WAAM, and that, by using higher deposition rates or by utilising renewable energy sources, the impact of WAAM can be reduced by more than 30%. [Display omitted] • The environmental performance of WAAM structural components is assessed. • WAAM steel beams have lower climate change impact than steel I-beams. • Topology optimisation leads to significant environmental benefits in using WAAM. • The environmental impact of WAAM is highly dependent on the deposition rate. • The use of shielding gas contributes greatly to the climate change impact of WAAM. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the outcomes of a series of beamline-based studies, the results of which are combined to provide a more detailed multiscale understanding of the structure and chemistry of geopolymer binders. The range of beamline-based characterization techniques which have been applied to the study of geopolymer binders is increasing rapidly; although no single technique can provide a holistic view of binder structure across all the length scales which are of importance in determining strength development and durability, the synergy achievable through the combination of multiple beamline techniques is leading to rapid advances in knowledge in this area. Studies based around beamline infrared and X-ray fluorescence microscopy, in situ and ex situ neutron pair distribution function analysis, and nano- and micro-tomography, are combined to provide an understanding of geopolymer gel chemistry, nano- and microstructure in two and three dimensions, and the influences of seeded nucleation and precursor chemistry in these key areas. The application of advanced characterization methods in recent years has brought the understanding of geopolymer chemistry from a point, not more than a decade ago, when the analysis of the detailed chemistry of the aluminosilicate binder gel was considered intractable due to its disordered (“X-ray amorphous”) nature, to the present day where the influence of key compositional parameters on nanostructure is well understood, and both gel structure and reaction kinetics can be manipulated through methods including seeding, temperature variation, and careful mix design. This paper therefore provides a review outlining the value of nanotechnology – and particularly nanostructural characterization – in the development and optimization of a new class of environmentally beneficial cements and concretes. Key engineering parameters, in particularly strength development and permeability, are determined at a nanostructural level, and so it is essential that gel structures can be analyzed and manipulated at this level; beamline-based characterization techniques are critical in providing the ability to achieve this goal. [Copyright &y& Elsevier]

A methodology for calibrating pH meters in highly alkaline solutions such as those relevant to cementitious systems is presented. This methodology uses an extended form of the Debye-Hückel equation to generate a calibration curve of pH vs. the measured electrochemical potential (mV) based on a series of aqueous alkali hydroxide solutions of known concentrations. This methodology is compared with the 'built-in' process of calibration based upon pH 4, 7, and 10 standard solutions. The built-in calibration process underestimates the real pH values by up to 0.3 log units, which is attributed to the alkali error. A spreadsheet for determining the calibration curve and its application to pH meter readings is provided as Supporting Information. The implications of improperly calibrated pH meters on interpreting solution chemistry in cementitious systems are discussed. [ABSTRACT FROM AUTHOR]