Cement and Concrete Research最新文献

英文中文

Investigation of the AFm-Cl system: Fe-to-Al solid solution, thermal behavior and carbonation AFm-Cl 系统研究：铁-铝固溶体、热行为和碳化

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-15 DOI: 10.1016/j.cemconres.2024.107696

Aurore Lechevallier , Mohend Chaouche , Jérôme Soudier , Evelyne Prat , Guillaume Renaudin

Due to increasing interest in reducing CO₂ emissions, new hydraulic binders are emerging, many of which contain significant amounts of iron and aluminum oxides. The reactivity of such binders can be activated using CaCl₂. It thus appears essential to investigate mixed Al/Fe-Cl hydrates to better characterize the hydration products and hydration processes of these new hydraulic binders. AFm-Cl phases with varying proportions of Al³⁺ and Fe³⁺ trivalent cations were synthesized and characterized. Carbonation of AFm-Cl samples is unavoidable at ambient atmosphere and leads to phases with Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O general composition (samples were synthesized for x = 0, 0.17, 0.33, 0.50, 0.67, 0.83 and 1). A complete solid solution between the two Ca₂Al(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O and Ca₂Fe(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O endmembers was demonstrated. Two hydration states were identified with characteristic interlayer distances of about 7.8 Å and 6.8 Å for, respectively, the Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O hydrate and the Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15 dehydrated phase. Thermal studies indicated a similar succession of thermal events for Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O regardless of the nature of the trivalent cation; the presence of iron however decreasing the degradation temperatures. Finally, the Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O phase was investigated in the presence of carbonate anions, showing a progressive exchange of chloride for carbonate within the interlayer to form Ca₂Al_1-xFe_x(OH)₆·(CO₃)_0.5·3H₂O before degrading into calcite.

由于人们对减少二氧化碳排放的兴趣与日俱增，新型液压粘合剂不断涌现，其中许多都含有大量的铁和铝氧化物。使用 CaCl2 可以激活此类粘合剂的反应活性。因此，研究 Al/Fe-Cl 混合水合物以更好地描述这些新型液压粘合剂的水化产物和水化过程显得至关重要。我们合成并表征了具有不同比例 Al3+ 和 Fe3+ 三价阳离子的 AFm-Cl 相。AFm-Cl 样品在环境气氛中不可避免地会发生碳化，从而形成具有 Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15-2H2O 基本成分的阶段（合成了 x = 0、0.17、0.33、0.50、0.67、0.83 和 1 的样品）。结果表明，Ca2Al(OH)6-Cl0.7(CO3)0.15-2H2O 和 Ca2Fe(OH)6-Cl0.7(CO3)0.15-2H2O 两种内含物之间存在完整的固溶体。确定了两种水合状态，Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15-2H2O 水合物和 Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15 脱水相的特征层间距离分别约为 7.8 Å 和 6.8 Å。热研究表明，无论三价阳离子的性质如何，Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15-2H2O 都会发生类似的连续热事件；但铁的存在会降低降解温度。最后，在碳酸根阴离子存在的情况下对 Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15-2H2O 相进行了研究，结果表明在降解为方解石之前，氯离子在层间逐渐交换为碳酸盐，形成 Ca2Al1-xFex(OH)6-(CO3)0.5-3H2O。

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引用次数: 0

Revealing the connection between carbonation regimes and early pozzolanic reactivity of recycled concrete powder: Impact of composition and microstructure 揭示再生混凝土粉末碳化机制与早期胶凝反应性之间的联系：成分和微观结构的影响

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-13 DOI: 10.1016/j.cemconres.2024.107697

Zihan Ma , Yi Jiang , Jionghuang He , Peiliang Shen , Qinglong Qin , Zhenjiang Gu , Jiangshan Li , Chi Sun Poon

This study aims to establish relationship between carbonation regimes and the early pozzolanic reactivity of carbonated recycled concrete powder (CRCP) by comparing the composition, structure and surface properties of the carbonation products. The surface of dry CRCP was characterized by a silica-rich layer and contains low-polymerized silica phases along with over 18 % of unstable calcium carbonate (Cc). Wet CRCP exhibits a silica-rich surface with the highest degree of silica polymerization and stable calcite in its composition. Semi-dry CRCP has a calcium-rich surface also contains high silica polymerization and over 29 % unstable calcium carbonate, and the highest specific surface area, leading to the fastest silicon dissolution and calcium consumption during pozzolanic reactions. The early pozzolanic reaction kinetics in semi-dry and wet carbonation are limited by the dissolution of carbonation products, whereas dry carbonation does not exhibit this limitation. Understanding this connection is crucial for selecting optimal carbonation techniques to enhance waste concrete utilization.

本研究旨在通过比较碳化产物的组成、结构和表面特性，确定碳化机制与碳化再生混凝土粉（CRCP）早期胶凝反应性之间的关系。干法 CRCP 的表面特征是富含二氧化硅层，含有低聚合二氧化硅相和超过 18% 的不稳定碳酸钙 (Cc)。湿润的 CRCP 表面富含二氧化硅，二氧化硅聚合度最高，成分中含有稳定的方解石。半干的 CRCP 表面富含钙质，也含有较高的二氧化硅聚合度和 29% 以上的不稳定碳酸钙，比表面积最大，因此在水胶凝反应过程中硅的溶解和钙的消耗速度最快。半干法和湿法碳化的早期水胶凝反应动力学受到碳化产物溶解的限制，而干法碳化则没有这种限制。了解这种联系对于选择最佳碳化技术以提高废弃混凝土利用率至关重要。

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引用次数: 0

The Cement and Concrete Research Le Chatelier Awards 水泥与混凝土研究勒沙特里耶奖

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-12 DOI: 10.1016/j.cemconres.2024.107689

Robert J. Flatt

引用次数: 0

Quantifying the immobilization mechanisms of heavy metals by Calcium Silicate Hydrate (C-S-H): The case of Cu2+ 量化硅酸钙水合物（C-S-H）固定重金属的机制：以 Cu2+ 为例

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-10 DOI: 10.1016/j.cemconres.2024.107695

Qi Liu , Pan Feng , Lijing Shao , Chen Chen , Xin Liu , Yuefeng Ma , Lizhi Zhang , Guoqing Geng

Understanding the interactions between calcium silicate hydrate (C-S-H) and heavy metals is vital for optimizing the use of solid waste in cementitious materials. This paper introduces an innovative approach to elucidate the immobilization mechanism of Cu²⁺, a representative heavy metal. The roles of Ca²⁺ and OH⁻ in Cu²⁺ immobilization were comprehensively investigated through being treated by C-S-H samples with varying interlayer Ca²⁺ contents via meticulous immersion in ammonium chloride (NH₄Cl). Our results indicate that Cu²⁺ immobilization primarily occurs via complete substitution of interlayer Ca²⁺ and partial substitution of intralayer Ca²⁺, with contributions of 40 % and 59 %, respectively, for a Ca/Si ratio of 1.2. Minor mechanisms like OH⁻ complexation and surface adsorption account for the remaining immobilization. The formation of Si-O-Cu complexes was confirmed by X-ray photoelectron (XPS) and Extended X-ray Absorption Fine Structure (EXAFS) analysis. This study provides a quantitative methodology that informs strategies for sustainable cementitious waste utilization.

了解水合硅酸钙（C-S-H）与重金属之间的相互作用对于优化水泥基材料中固体废弃物的利用至关重要。本文介绍了一种创新方法来阐明具有代表性的重金属 Cu2+ 的固定化机理。通过将不同层间 Ca2+ 含量的 C-S-H 样品精心浸泡在氯化铵（NH4Cl）中，全面研究了 Ca2+ 和 OH- 在 Cu2+ 固定化过程中的作用。我们的研究结果表明，Cu2+ 固定化主要是通过层间 Ca2+ 的完全置换和层内 Ca2+ 的部分置换实现的，在 Ca/Si 比为 1.2 时，两者的贡献率分别为 40% 和 59%。其余的固定化作用主要来自于一些次要机制，如羟基络合和表面吸附。X 射线光电子（XPS）和扩展 X 射线吸收精细结构（EXAFS）分析证实了 Si-O-Cu 复合物的形成。这项研究提供了一种定量方法，为水泥基废物的可持续利用战略提供了依据。

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引用次数: 0

Setting reaction of a olivine-based Mg-phosphate cement 橄榄石基磷酸镁水泥的凝结反应

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-10 DOI: 10.1016/j.cemconres.2024.107694

Davide Bernasconi , Alberto Viani , Lucie Zárybnická , Simone Bordignon , Jose R.A. Godinho , Alexey Maximenko , Cem Celikutku , Sadaf Fatima Jafri , Elisa Borfecchia , Quentin Wehrung , Roberto Gobetto , Alessandro Pavese

The cementitious properties of natural Mg-rich olivine when reacted with a phosphoric acid solution are investigated, as a function of acid concentration and liquid/solid mass ratio. The obtained cements are composed of residual olivine crystals and amorphous silica nanoparticles dispersed in a dense and compact newberyite (MgHPO₄∙3H₂O) matrix. The latter was mostly formed by packed micrometric tabular crystals, although evidence of the presence of a fraction of amorphous MgHPO₄ was also found. Water content in the raw mix was observed to play a pivotal role on the reaction pathway, either promoting porosity or hindering the crystallization of the products. Up to 57 % of olivine reactivity, whose dissolution was promoted by the curing temperature (60 °C) and low pH, was achieved. All in all, these results indicate that the industrial mineral olivine may serve a viable source of Mg for the production of phosphate cements.

研究了天然富镁橄榄石与磷酸溶液反应时的胶结特性，以及酸浓度和液体/固体质量比的函数关系。所获得的胶结物由残余橄榄石晶体和无定形二氧化硅纳米颗粒组成，它们分散在致密紧密的新贝里岩（MgHPO4∙3H2O）基体中。后者主要由堆积的微米级片状晶体形成，但也发现了部分无定形 MgHPO4 的存在。据观察，原料混合物中的水含量对反应路径起着关键作用，既可促进孔隙度，也可阻碍产物结晶。由于固化温度（60 °C）和低 pH 值促进了橄榄石的溶解，因此橄榄石的反应活性高达 57%。总之，这些结果表明，工业矿物橄榄石可作为生产磷酸盐水泥的可行镁源。

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引用次数: 0

Phase, structure, and hygroscopic property evolutions of alkali-silica reaction gels under freeze drying 冷冻干燥条件下碱硅反应凝胶的物相、结构和吸湿性能演变

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-09 DOI: 10.1016/j.cemconres.2024.107692

Arkabrata Sinha, Jianqiang Wei

Alkali-silica reaction (ASR), a detrimental process causing volume expansion and cracking in concrete by forming hygroscopic and swellable gel-like products, has been a long-standing challenge faced by concrete structures across the world. Understanding the underlying mechanisms of formation, moisture uptake and swelling of ASR gels requires thorough characterizations, where an appropriate drying method to remove free water and stop the reactions in the samples is essential. This study aims to elucidate the effect of freeze-drying, an emerging drying technique increasingly employed in sample preparations, on the phase, molecular structure, and moisture absorption behavior of ASR gels. Towards this end, six ASR gels with three calcium-to-silica (Ca/Si) ratios (0.1, 0.3, and 0.5) and two alkali-to-silica [(Na + K)/Si] ratios of 0.3 (low-alkali gels) and 1.0 (high-alkali gels) were studied. The results indicate that the chemical bonds and mineral components of ASR gels can be maintained during the removal of free and loosely bound water in freeze drying, while slight changes in crystallization and relative contents of alkali-silicate hydrate and calcium silicate hydrate phases were observed, in particular, for the high-alkali ASR gels. Although slight decreases in Q¹, Q^2, and Q³ silica polymerization sites and increases in the mean chain length and degree of polymerization were observed from the nuclear magnetic resonance (NMR) spectroscopy, the intrinsic layered silicate structure of ASR gels remains. The moisture absorption of low-alkali and high-alkali ASR gels was found to be governed by gel pores and mesopores, respectively. After freeze-drying, slight increases in moisture sorption (a 6.8 % increase in absorption and a 2.2 % decrease in desorption) and enhanced hysteresis were observed from the low-alkali gels. The high-alkali gels, however, showed a slight decrease in hygroscopicity along with a 16.6 % reduction of mesopores.

碱硅反应（ASR）是通过形成吸湿性和膨胀性凝胶状产物而导致混凝土体积膨胀和开裂的有害过程，是全球混凝土结构长期面临的挑战。要想了解 ASR 凝胶的形成、吸湿和膨胀的基本机制，就必须对其进行全面的表征，其中必须采用适当的干燥方法去除游离水并停止样品中的反应。冷冻干燥是一种新兴的干燥技术，在样品制备过程中被越来越多地采用，本研究旨在阐明冷冻干燥对 ASR 凝胶的相位、分子结构和吸湿行为的影响。为此，研究人员研究了六种 ASR 凝胶，它们的钙硅比（Ca/Si）分别为 0.1、0.3 和 0.5，碱硅比（(Na + K)/Si] 分别为 0.3（低碱凝胶）和 1.0（高碱凝胶）。结果表明，ASR 凝胶的化学键和矿物成分可在冷冻干燥过程中去除自由水和松散结合水的过程中保持不变，同时观察到结晶和碱硅酸盐水合物及硅酸钙水合物相的相对含量发生了轻微变化，尤其是在高碱 ASR 凝胶中。虽然从核磁共振（NMR）光谱中观察到 Q1、Q2 和 Q3 硅聚合位点略有减少，平均链长和聚合度有所增加，但 ASR 凝胶的固有层状硅酸盐结构依然存在。研究发现，低碱和高碱 ASR 凝胶的吸湿性分别受凝胶孔隙和中孔的支配。冷冻干燥后，低碱凝胶的吸湿性略有提高（吸湿性提高 6.8%，解吸性降低 2.2%），滞后性也有所增强。然而，高碱凝胶的吸湿性略有下降，中孔减少了 16.6%。

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引用次数: 0

Plugging effect of fine pore water in OPC and LC3 paste during accelerated carbonation monitored via single-sided nuclear magnetic resonance spectroscopy 通过单面核磁共振波谱监测加速碳化过程中 OPC 和 LC3 浆料中细小孔隙水的堵塞效应

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-08 DOI: 10.1016/j.cemconres.2024.107688

Luge Cheng , Ryo Kurihara , Takahiro Ohkubo , Ryoma Kitagaki , Atsushi Teramoto , Yuya Suda , Ippei Maruyama

This study investigates the influence of CO₂ concentration on the carbonation process in cementitious paste, focusing on water content distribution in ordinary Portlandite cement and limestone-calcined clay cement (LC³). Employing single-sided nuclear magnetic resonance spectroscopy for water profiling, we revealed that under accelerated carbonation of 5 % and 1 %, the water content in fine pores (interlayer space and gel pores) kept constant at the carbonation front, demonstrating the plugging effect where fine pore water removal governs carbonation progress. This effect was absent under natural carbonation conditions because evaporation precedes the carbonation process. This study emphasizes that to accurately characterize cementitious materials under natural carbonation conditions, CO₂ concentrations in accelerated methods should be constrained to prevent the plugging effect.

本研究探讨了二氧化碳浓度对水泥基浆料碳化过程的影响，重点研究了普通硅酸盐水泥和石灰岩煅烧粘土水泥（LC3）中的含水率分布。利用单面核磁共振波谱进行水剖面分析，我们发现在 5 % 和 1 % 的加速碳化条件下，碳化前沿细孔（层间空间和凝胶孔）中的含水量保持恒定，这表明了细孔脱水主导碳化进程的堵塞效应。在自然碳化条件下不存在这种效应，因为蒸发先于碳化过程。本研究强调，要准确表征自然碳化条件下胶凝材料的特性，应限制加速方法中的二氧化碳浓度，以防止堵塞效应。

引用次数: 0

New insights on the basic creep mechanism of one-part alkali activated slag and fly ash paste 关于单组分碱激活炉渣和粉煤灰浆基本蠕变机理的新见解

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-08 DOI: 10.1016/j.cemconres.2024.107691

Han Gao , Igor Shikhov , Ehab Hamed , Ailar Hajimohammadi , Iman Al-Damad , Christoph Arns , Stephen J. Foster

In this paper, basic creep mechanism of ambient cured one-part alkali activated slag-fly ash (AASF) paste is examined at the microscopic level. A special mini creep rig is constructed enabling in-situ monitoring of water redistribution over time between high- and low-density (HD, LD) gel pores within the loaded paste specimens using ¹H NMR relaxometry. The results suggest that the contraction of C-(N)-A-S-H particles is accompanied by the reduction of water content in HD gel for loaded AASF paste. In contrast, in the loaded OPC paste a noticeable decrease of water residing in LD rather than HD C-S-H gel was observed, implying the presence of a distinct creep mechanism. In addition to the different water environment, the more crosslinked bonding structure of AASF could partially account for its lower creep response supported by ²⁹Si NMR measurement. The findings of this study provide evidence in understanding underlying basic creep mechanism of AASF.

本文从微观层面研究了常温固化单组分碱活性矿渣飞灰（AASF）浆料的基本蠕变机理。利用 1H NMR 驰豫测定法，构建了一个特殊的微型蠕变装置，可对加载浆糊试样中高密度和低密度（HD、LD）凝胶孔之间的水分随时间的重新分布进行原位监测。结果表明，在加载 AASF 浆料的高密度凝胶中，C-(N)-A-S-H 颗粒的收缩伴随着水分含量的减少。与此相反，在负载的 OPC 胶浆中，观察到 LD 而不是 HD C-S-H 凝胶中的水分含量明显减少，这意味着存在一种独特的蠕变机制。除了不同的水环境外，AASF 的交联键合结构也可能是其蠕变响应较低的部分原因，29Si NMR 测量证明了这一点。这项研究结果为了解 AASF 的基本蠕变机制提供了证据。

引用次数: 0

Insights on the mechanical properties and failure mechanisms of calcium silicate hydrates based on deep-learning potential molecular dynamics 基于深度学习潜在分子动力学的硅酸钙水合物力学性能和失效机理透视

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-02 DOI: 10.1016/j.cemconres.2024.107690

Weihuan Li , Chenchen Xiong , Yang Zhou , Wentao Chen , Yangzezhi Zheng , Wei Lin , Jiarui Xing

The molecular-scale mechanical properties of calcium silicate hydrates are crucial to the macro performance of cementitious materials, while achieving coincidence between accuracy and efficiency in computational simulations still remains a challenge. This study utilizes a deep-learning potential, specifically developed for calcium silicate hydrates based on artificial neural network, to achieve molecular dynamics simulations with accuracy comparable to first-principle methods. With this potential, the elastic properties and uniaxial mechanical behaviors are explored, wherein the anisotropy and impact mechanism of calcium ratios are analyzed. The results add to evidence that the deep-learning potential possess a higher accuracy than common force fields. The anisotropy of elastic modulus is mainly attributed to different atomic interactions in various directions, while the anisotropy of strength is additionally affected by the form of failure. This study may advance the accurate molecular-scale simulation and deepen the understanding of the strength source and cohesion mechanism of cement-based materials.

硅酸钙水合物的分子尺度力学性能对胶凝材料的宏观性能至关重要，但如何在计算模拟中实现精度与效率的兼顾仍是一项挑战。本研究利用基于人工神经网络专门为硅酸钙水合物开发的深度学习势能，实现了分子动力学模拟，其精度可与第一原理方法相媲美。利用该势垒探索了硅酸钙水合物的弹性特性和单轴力学行为，其中分析了钙比例的各向异性和影响机制。研究结果进一步证明，深度学习势比普通力场具有更高的精度。弹性模量的各向异性主要归因于不同方向上的原子相互作用，而强度的各向异性则受到破坏形式的影响。这项研究可推进分子尺度的精确模拟，加深对水泥基材料强度来源和内聚机理的理解。

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引用次数: 0

Importance of adsorption compared with complexation for retarding C3S hydration via adding sodium gluconate 在通过添加葡萄糖酸钠延缓 C3S 水化方面，吸附作用与络合作用相比具有重要意义

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research

Pub Date : 2024-10-02 DOI: 10.1016/j.cemconres.2024.107686

Guitao Luo , Muyu Liu , Hua Li , Yang Liu , Hongbo Tan , Qimin Liu

Adsorption effect on particle surfaces and complexation effect with free Ca²⁺ mostly determine the retarding performance of organic admixtures on cement hydration. However, it is difficult to identify which effect plays a more important role in retarding hydration by experimental methods. Here, a theoretical model was developed to investigate the retarding mechanisms of sodium gluconate (SG) on hydration of tricalcium silicate (C₃S). Based on obstruction theory and complexation reaction kinetics, effects of adsorption and complexation were simulated to examine the retarding performance of C₃S hydration with addition of SG. The proposed model well predicted the effect of additional dosing of SG on the retarding performance of C₃S hydration. Theoretical parameter studies demonstrated that adsorption ratio contributed much largely to the delays in C₃S hydration, compared with rate constant of complex generation. Therefore, it is confirmed that adsorption plays a more important role in regulating the retarding mechanism of C₃S hydration.

颗粒表面的吸附效应和与游离 Ca2+ 的络合效应在很大程度上决定了有机外加剂对水泥水化的延缓性能。然而，通过实验方法很难确定哪种效应在延缓水化中起着更重要的作用。本文建立了一个理论模型来研究葡萄糖酸钠（SG）对硅酸三钙（C3S）水化的延缓机制。根据阻塞理论和络合反应动力学，模拟了吸附和络合的影响，以研究加入 SG 后 C3S 水化的阻滞性能。所提出的模型很好地预测了添加 SG 对 C3S 水化延缓性能的影响。理论参数研究表明，与络合物生成速率常数相比，吸附比对 C3S 水合延迟的影响更大。因此，吸附在调节 C3S 水化延迟机制中起着更重要的作用。

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引用次数: 0

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