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Multi–sensory Monitoring and Non–destructive Testing of New Materials for Concrete Engineered Barrier Systems 混凝土工程屏障系统新材料的多感官监测和无损检测
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-09-06 DOI: 10.3151/jact.22.516
Vera Lay, Franziska Baensch, Anna Maria Skłodowska, Tobias Fritsch, Michael Stamm, Prathik Prabhakara, Sergej Johann, Patrick Sturm, Hans-Carsten Kühne, Ernst Niederleithinger

The crucial part of nuclear waste storage is the construction of sealing structures made of reliable, safe and well–understood materials. We present an extended analysis of long-term multi–sensory monitoring and non–destructive testing (NDT) inspection of two laboratory specimens aiming at potential materials for sealing structures for nuclear waste repositories. Specimens with a volume of 340 litres made from newly developed alkali–activated materials (AAM) and established salt concrete (SC) were analysed using embedded acoustic emission and wireless radio-frequency identification (RFID) sensors, ultrasonic echo imaging, active thermography, and X–ray computed tomography. The monitoring analysis showed lower heat of reaction and 50% less acoustic emission events in AAM compared to SC. However, due to the surface effects of the AAM material, the number of acoustic emission events increased significantly after approximately two months of monitoring. Subsequently performed NDT inspections reliably located embedded sensors and confirmed the absence of major cracks or impurities. The presented laboratory results show the feasibility and potential of comprehensive NDT monitoring and inspection to characterise cementitious and alternative materials as well as the need for multi–parameter long–term monitoring. Thus, our study demonstrates that tailored NDT investigations will help to develop safe sealing structures for nuclear waste repositories.

核废料贮存的关键部分是使用可靠、安全和易于理解的材料建造密封结构。我们介绍了对两个实验室试样的长期多感官监测和无损检测(NDT)的扩展分析,这些试样是核废料贮存库密封结构的潜在材料。使用嵌入式声发射和无线射频识别(RFID)传感器、超声回波成像、有源热成像和 X 射线计算机断层扫描,对新开发的碱活性材料(AAM)和成熟的盐混凝土(SC)制成的 340 升试样进行了分析。监测分析表明,与盐拌混凝土相比,AAM 的反应热更低,声发射事件减少 50%。然而,由于 AAM 材料的表面效应,声发射事件的数量在大约两个月的监测后显著增加。随后进行的无损检测可靠地确定了嵌入式传感器的位置,并确认不存在重大裂缝或杂质。所提供的实验室结果表明,通过全面的无损检测监控和检查来确定水泥基材料和替代材料的特性是可行的、有潜力的,同时也表明需要进行多参数的长期监控。因此,我们的研究表明,有针对性的无损检测调查将有助于为核废料储存库开发安全的密封结构。
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引用次数: 0
Ion Evolution in Pore Solution of Alkali-activated Slag System and Its Effect on Passivation Behaviour of Steel Bars 碱激活炉渣体系孔隙溶液中的离子演化及其对钢棒钝化行为的影响
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-08-27 DOI: 10.3151/jact.22.499
Zhantao Du, Zuquan Jin, Bo Pang, Shicai Li, Chencui Wang

The passivation of steel bars in concrete is determined by the characteristics of the concrete pore solution. However, ion evolution in the pore solution of alkali-activated slag/limestone powder (AAS/L) systems is not yet well known. Therefore, in this study, ion evolution in real and simulated pore solutions of alkali-activated slag/limestone powder mortars is investigated using high-pressure and solid-liquid extraction methods. The study focuses on investigating the passivation behaviour of steel bars when exposed to the simulated pore solution. The results demonstrate that the contents of Ca, Na, Al, Si, and S2O32- first increase and then decrease with time, whereas the contents of K and SO42- consistently increase. Among the simulated pore solutions, the one with a solid-liquid ratio of 1 : 1 and an age of 14 days closely resembles the actual pore solution. In addition, the presence of a high S content resulting from the dissolution of S in the slag inhibits the passivation process of the steel bars in the simulated pore solution of AAS. However, the passivation film of the steel bars formed in the simulated AASL pore solution is strengthened by the addition of the limestone powder.

混凝土中钢筋的钝化取决于混凝土孔隙溶液的特性。然而,碱活性矿渣/石灰石粉(AAS/L)体系孔隙溶液中的离子演变情况尚不十分清楚。因此,本研究采用高压和固液萃取方法研究了碱激活矿渣/石灰石粉砂浆实际和模拟孔隙溶液中的离子演变。研究重点是调查钢筋暴露在模拟孔隙溶液中的钝化行为。结果表明,随着时间的推移,Ca、Na、Al、Si 和 S2O32- 的含量先增加后减少,而 K 和 SO42- 的含量则持续增加。在模拟孔隙溶液中,固液比为 1 : 1、龄期为 14 天的模拟孔隙溶液与实际孔隙溶液非常相似。此外,炉渣中 S 的溶解导致 S 含量较高,这抑制了 AAS 模拟孔隙溶液中钢筋的钝化过程。然而,在模拟 AASL 孔隙溶液中形成的钢筋钝化膜却因石灰石粉的加入而得到加强。
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引用次数: 0
Carbonated Concrete Slurry Waste as Supplementary Cementitious Material 作为补充胶凝材料的碳化混凝土浆废料
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-08-23 DOI: 10.3151/jact.22.485
Frank Winnefeld, Johannes Tiefenthaler, Andreas Leemann

Concrete slurry waste is generated at concrete plants and generally re-used in new batches of concretes. Due to the presence of hydrated cement paste it has the potential to be carbonated prior to re-use in order not only to store CO2, but also to enhance its reactivity in blends with cement. In this study, a concrete slurry waste obtained at a ready-mix concrete plant was investigated. For accelerated carbonation, a wet process was used at laboratory scale. The carbonated product was dried afterwards, characterized and used as supplementary cementitious material. When carbonated, the hydrate phases of the concrete slurry waste decomposed to calcite, gypsum and a silica-alumina gel. When blended with Portland cement (30% replacement by mass) early hydration kinetics was accelerated by the carbonated concrete slurry waste. The pozzolanic reaction of the silica-alumina gel consumed a significant part of the portlandite and showed a slightly positive contribution to compressive strength compared to inert quartz powder and to the uncarbonated concrete slurry. This offers the use of carbonated concrete slurry waste to store CO2 in concrete with the additional benefit of reducing the cement content.

混凝土工厂会产生混凝土浆废料,通常会在新批次的混凝土中重复使用。由于水化水泥浆的存在,它有可能在重新使用前被碳化,这样不仅可以储存二氧化碳,还可以提高其与水泥混合的反应能力。本研究对一家预拌混凝土厂产生的混凝土浆废料进行了调查。为了加速碳化,我们在实验室采用了湿法工艺。碳化后的产品经过干燥、表征并用作胶凝补充材料。碳化后,混凝土浆料废料中的水合物相分解为方解石、石膏和硅铝凝胶。当与波特兰水泥(30% 替代质量)混合时,碳化混凝土浆废料加速了早期水化动力学。二氧化硅-氧化铝凝胶的水胶化反应消耗了大量的波特兰石,与惰性石英粉和未碳化的混凝土浆相比,对抗压强度的贡献略微增加。这为利用碳化混凝土浆废料在混凝土中储存二氧化碳提供了可能,同时还能降低水泥含量。
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引用次数: 0
Investigating the Influence of SCMs on Mechanical Performance through Experimental Feret's Coefficients in Low-carbon Concrete 通过低碳混凝土中的试验费雷系数研究单体材料对力学性能的影响
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-08-23 DOI: 10.3151/jact.22.471
Ana Antunes, Eliana Soldado, Hugo Costa, Ricardo do Carmo, Eduardo Júlio

The focus on sustainable construction materials has prompted research into alternatives to reduce the carbon dioxide emissions associated with the production of Portland cement. Several studies have attempted to minimise the use of Portland cement in structural concrete mixtures. However, traditional formulations and prediction models are not applicable to low-carbon concrete. Therefore, this study aimed to evaluate low carbon concrete mortar matrices, focusing on cement replacement by supplementary cementitious materials (SCMs), such as fly ash, natural pozzolans and electric arc furnace slag, increasing the compactness of the mixtures, and limiting the water-binder ratio. Different binder powder contents were studied (350 and 400 kg/m3) in two types of concrete for prefabrication: dry consistency and plastic consistency. The results showed that dry consistency mixtures with a higher fly ash content allow higher compactness. Higher compactness promotes an overall increase in Young's modulus, up to 16%, for all eco-mixtures. The analysis enabled the estimation of the Feret coefficients for each combination of cement with SCMs and their correlation with a power function, dependent on the water-cement ratio. This allows the future estimation of the strength for binder pastes of mixtures incorporating different percentages of these additions.

对可持续建筑材料的关注促使人们研究替代品,以减少与波特兰水泥生产相关的二氧化碳排放。一些研究试图尽量减少结构混凝土混合物中硅酸盐水泥的使用。然而,传统的配方和预测模型并不适用于低碳混凝土。因此,本研究旨在评估低碳混凝土砂浆基质,重点是用粉煤灰、天然毛细管和电弧炉矿渣等辅助胶凝材料(SCMs)替代水泥,提高混合物的密实度,并限制水-粘结剂比率。研究了两种预制混凝土中不同的粘合剂粉末含量(350 和 400 千克/立方米):干稠度和塑性稠度。结果表明,粉煤灰含量较高的干稠混合物可获得较高的密实度。密实度越高,所有生态混合物的杨氏模量都会全面提高,最高可达 16%。通过分析,可以估算出水泥与单体材料的每种组合的费雷系数,以及它们与幂函数的相关性(取决于水灰比)。这样,今后就可以对含有不同比例这些添加物的混合物粘结浆的强度进行估算。
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引用次数: 0
Structural Performance of RC Members Affected by Alkali–silica Reaction According to Crack Patterns 根据裂缝形态确定受碱-二氧化硅反应影响的 RC 构件的结构性能
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-08-22 DOI: 10.3151/jact.22.455
Hyo Eun Joo, Yuya Takahashi

The structural performance of reinforced concrete (RC) members affected by alkali–silica reaction (ASR) is difficult to predict because of the multi-scale phenomena. Recent structural tests reveal that the performance of RC members also depends on ASR-induced crack patterns, including localized cracks and dispersed microcracks. Additionally, microscopic factors, such as crack-filling by gel and presence of microcracks, are relevant. To explore this in detail, a computational system for finite element analysis of ASR-damaged RC members was developed. This study numerically investigated the structural behavior of ASR-affected RC members based on localized/dispersed crack patterns and microscopic factors. The applicability of the developed computational system was verified by comparing the analysis results with experimental data. The analysis results showed that ASR-damaged RC members with dispersed microcracks exhibited highly ductile behavior, while those with localized cracks failed in shear. This is because the dispersed crack pattern prevents the shear crack propagation and enhances the mechanical contribution of gel filling cracks, while the localized ASR cracks facilitate critical crack propagation, leading to failure, and minimize the gel-filling effect. Through the analytical investigations, it was found that the localized ASR cracks can result in significant loss of structural performance; thus, this study recommends the assessment of structural capacity of RC members in the case where the localized cracks were observed.

受碱-硅反应(ASR)影响的钢筋混凝土(RC)构件的结构性能因其多尺度现象而难以预测。最近的结构测试表明,RC 构件的性能还取决于 ASR 诱导的裂缝形态,包括局部裂缝和分散微裂缝。此外,微观因素,如凝胶体的裂缝填充和微裂缝的存在,也与此相关。为了详细探讨这一问题,我们开发了一套用于对 ASR 损坏的 RC 构件进行有限元分析的计算系统。该研究基于局部/分散裂纹模式和微观因素,对受 ASR 影响的 RC 构件的结构行为进行了数值研究。通过将分析结果与实验数据进行比较,验证了所开发计算系统的适用性。分析结果表明,具有分散微裂纹的 ASR 损坏 RC 构件表现出高度延展性,而具有局部裂纹的构件则在剪切中失效。这是因为分散的裂纹模式阻止了剪切裂纹的扩展,增强了凝胶填充裂纹的力学贡献,而局部的 ASR 裂纹则促进了临界裂纹的扩展,导致破坏,并将凝胶填充效应降至最低。通过分析研究发现,局部 ASR 裂缝会导致结构性能的显著损失;因此,本研究建议在观察到局部裂缝的情况下评估 RC 构件的结构承载能力。
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引用次数: 0
Effect of Calcium-Magnesia Compound Expansive Agent on the Macroscopic Performance and Microstructure of Concrete 钙镁复合膨胀剂对混凝土宏观性能和微观结构的影响
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-08-20 DOI: 10.3151/jact.22.445
Ji Xiao, Lang Jin, Feixiang Chen, Yong Leng, Guozhi Zhang, Kexin Liu

This study aims to discuss the effects of calcium-magnesia compound expansive agent on the mechanical strength, shrinkage, and creep of concrete. On this basis, the expansive mechanism is investigated by using XRD, TG measurement, and MIP with percolation and backbone fractal dimension analysis. It is shown that replacing fly ash with calcium-magnesia compound expansive agent has little effect on the axial compression strength, but significantly reduces the elastic modulus. Moreover, increasing the amount of expansive agent from 0% to 12% leads to a reduction in autogenous shrinkage values by 9.1% to 14.8% at 180 days while causing an increase in creep by 24.5% to 37.8%. Concurrently, the porosity of the concrete increases with the addition of the calcium-magnesia compound expansive agent, and the proportion of gel and medium capillary pores in the total porosity also increases. However, fractal dimension analysis shows that it also decreases the complexity of overall connectivity of interconnected pores. Furthermore, the results obtained from TG also indicate that the calcium-magnesia compound expansive agent is beneficial for the formation of gel hydration products.

本研究旨在探讨钙镁复合膨胀剂对混凝土机械强度、收缩和徐变的影响。在此基础上,利用 XRD、TG 测量、MIP 与渗流和骨架分形维度分析研究了膨胀机理。结果表明,用钙镁复合膨胀剂替代粉煤灰对轴向压缩强度影响不大,但会显著降低弹性模量。此外,将膨胀剂的用量从 0% 增加到 12%,可使 180 天的自生收缩值降低 9.1% 至 14.8%,同时使蠕变增加 24.5% 至 37.8%。同时,混凝土的孔隙率随着钙镁复合膨胀剂的添加而增加,总孔隙率中凝胶孔和中等毛细孔的比例也随之增加。然而,分形维度分析表明,它也降低了相互连接的孔隙整体连通性的复杂性。此外,TG 得出的结果还表明,钙镁复合膨胀剂有利于凝胶水合产物的形成。
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引用次数: 0
Influence of the Unit Content and Grading Distribution of Fine Aggregates on the Long-term Skid Resistance of Concrete Pavement 细集料的单位含量和级配分布对混凝土路面长期抗滑性的影响
IF 1.6 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-08-10 DOI: 10.3151/jact.22.431
Jaganmuthu Senthilvelan, Hidefumi Izuo, Taiju Endo, Atsushi Ueno
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引用次数: 0
Cold-sintered Carbonated Concrete Waste Fines: A Calcium Carbonate Concrete Block 冷烧结碳酸混凝土废粉:碳酸钙混凝土砌块
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-07-24 DOI: 10.3151/jact.22.406
Ippei Maruyama, Ngoc Kien Bui, Amr Meawad, Ryo Kurihara, Yuji Mitani, Hikotsugu Hyodo, Manabu Kanematsu, Takafumi Noguchi

Cementitious materials generally have large carbon footprints because of the high CO2 emitted during Portland cement production. This is because limestone is used as an essential CaO resource, and its decomposition by calcination emits CO2. From this perspective, the concrete in urban buildings can be considered an urban mine of CaO resources. In this study, we propose obtaining a solidified product by crushing all the waste concrete, carbonating it, pressurizing it with a calcium bicarbonate solution, and drying it. The experimental results show that the bicarbonate solution, high-temperature conditions, and extended loading period produce a higher strength. In addition, neck growth at the contact surfaces of the carbonated concrete fines was confirmed using scanning electron microscopy. Consequently, the proposed method indicates that the hardening mechanism is the cold sintering of calcium carbonate on the surface of fine-carbonated concrete particles. This method allows the developed blocks to be used semi-permanently with relatively low energy consumption through repeated crushing and re-pressurization.

由于波特兰水泥生产过程中会排放大量二氧化碳,因此水泥基材料的碳足迹通常较大。这是因为石灰石是一种重要的 CaO 资源,其煅烧分解过程会排放二氧化碳。从这个角度来看,城市建筑中的混凝土可被视为 CaO 资源的城市矿山。在这项研究中,我们建议通过粉碎所有废弃混凝土、碳化、用碳酸氢钙溶液加压和干燥来获得固化产品。实验结果表明,碳酸氢盐溶液、高温条件和加载时间的延长可产生更高的强度。此外,扫描电子显微镜还证实了碳化混凝土细料接触面的颈部生长。因此,所提出的方法表明,硬化机制是碳化混凝土细粒表面的碳酸钙冷烧结。通过这种方法,开发出的砌块可以通过反复破碎和再加压,以相对较低的能耗实现半永久性使用。
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引用次数: 0
Influence of Rebar Strength, Pre-treatment, and Measurement Method on Residual Stress Measurement using Portable X-ray Diffractometer 钢筋强度、预处理和测量方法对使用便携式 X 射线衍射仪测量残余应力的影响
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-07-24 DOI: 10.3151/jact.22.391
Ryohei Yanagida, Saiji Fukada, Toshihiko Sasaki

It is effective for the maintenance of existing structures to understand the current status, such as the residual stress of the materials used, and a portable X-ray diffractometer is used as a technique for measuring steel stress. Although measurement methods and pre-treatment for steel bars with low strength have been revealed, the influence of the strength on the X-ray stress measurement and the appropriate measurement method has not been clarified. In this study, residual stress measurements using the X-ray diffraction are performed on steel bars, the differences in the results for various steels with different strengths are discussed, and measurement conditions for accurate measurement are reported. In addition, the cause of the tendency of the X-ray stress measurement to be smaller than the actual increment value under high stress is investigated. The experimental results show that the appropriate measurement conditions vary depending on the rebar strength, and that the X-ray stress measurement under high stress also varies. The metallurgical structure of the steel was shown to be related to the cause of this phenomenon through microstructural observation and analysis of the deformation behavior.

了解所使用材料的残余应力等现状对现有结构的维护非常有效,便携式 X 射线衍射仪被用作测量钢应力的技术。虽然低强度钢筋的测量方法和预处理方法已被揭示,但强度对 X 射线应力测量的影响以及合适的测量方法尚未明确。本研究利用 X 射线衍射对钢筋进行了残余应力测量,讨论了不同强度的各种钢材测量结果的差异,并报告了精确测量的测量条件。此外,还研究了在高应力下 X 射线应力测量值小于实际增量值的趋势的原因。实验结果表明,钢筋强度不同,适当的测量条件也不同,高应力下的 X 射线应力测量结果也不同。通过微观结构观察和变形行为分析,证明钢材的冶金结构与造成这种现象的原因有关。
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引用次数: 0
Development of a Large-scale Thermogravimetry and Gas Analyzer for Determining Carbon in Concrete 开发用于测定混凝土中碳含量的大型热重仪和气体分析仪
IF 2 4区 工程技术 Q3 CONSTRUCTION & BUILDING TECHNOLOGY Pub Date : 2024-06-24 DOI: 10.3151/jact.22.383
Ippei Maruyama, Koichiro Noritake, Yoshinobu Hosoi, Haruka Takahashi

One carbon neutralization measure applied in the concrete sector is the use of artificial carbonate in concrete for immobilization. This CO2 reduction technology corresponds to the CO2 emitted during concrete production. When considering the marketability of these technologies, especially for newly developed products in the carbon market, it is essential to quantify the amount of CO2 fixed as inorganic carbonate. Additionally, as a representative test specimen for concrete containing aggregate, a φ100 × 200 mm cylinder specimen is conventionally used for physical property evaluation. To evaluate the amount of CO2 fixed in one batch of concrete, a mass far from that of the conventional chemical analysis sample may need to be analyzed. Therefore, in this study, we investigated a pulverization process for concrete analytical materials. We also propose a new analytical apparatus that can be used to measure large cylinder specimens. Experimental results showed that the newly developed analyzer, equipped with a mass balance and CO2 and H2O gas analyzer for large cylinders, exhibited excellent analytical variability and measurement speed performance. It was also inferred that the homogenization process is necessary to grind the entire cylindrical concrete specimen into a fine powder and homogenize it to improve the representativeness of the concrete.

混凝土行业采用的一种碳中和措施是在混凝土中使用人工碳酸盐进行固定。这种二氧化碳减排技术与混凝土生产过程中排放的二氧化碳相对应。在考虑这些技术的可销售性时,尤其是碳市场上新开发的产品,必须量化以无机碳酸盐形式固定的二氧化碳量。此外,作为含骨料混凝土的代表性试样,φ100 × 200 毫米的圆柱体试样通常用于物理性质评估。要评估一批混凝土中固定的二氧化碳量,可能需要分析与传统化学分析样本质量相差甚远的质量。因此,在本研究中,我们对混凝土分析材料的粉碎过程进行了研究。我们还提出了一种可用于测量大型圆柱体试样的新型分析仪器。实验结果表明,新开发的分析仪配备了质量平衡和用于大型圆柱体的 CO2 和 H2O 气体分析仪,在分析变异性和测量速度方面表现出色。此外,还推断出匀质过程是将整个圆柱形混凝土试样研磨成细粉并进行匀质处理以提高混凝土代表性的必要过程。
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引用次数: 0
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Journal of Advanced Concrete Technology
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