CEMENT最新文献 - Book学术

Downstream processing of End-of-Life concrete for the recovery of high-quality cementitious fractions 对报废混凝土进行下游处理以回收优质胶凝组分

CEMENT

Pub Date : 2024-11-06 DOI: 10.1016/j.cement.2024.100121

A.T.M. Alberda van Ekenstein , H.M. Jonkers , M. Ottelé

The clinker in cement largely determines the environmental footprint of concrete. Therefore, concrete recycling should focus on retrieving high-quality cementitious fractions to replace clinker. This requires a shift from current traditional recycling techniques towards innovative recycling methods, enabling recovery of not only clean secondary aggregates, but also residual cementitious fines (RCF), potentially eliminating the carbon dioxide emissions associated with them. The production and upcycling of RCF offer new implementation routes that were previously deemed unfeasible. However, the properties of RCF may vary based on their origin, affecting their replacement and upcycling potential. Consequently, assessing the original concrete quality, with a focus on the binder type, before demolition is important. A handheld x-ray fluorescence technique appears promising for this purpose. To achieve effective separation of clean secondary aggregates from the original cementitious content, innovative crushing and separation techniques are needed. Additionally, electrostatic separation shows significant research potential for further optimizing RCF.

水泥中的熟料在很大程度上决定了混凝土的环境足迹。因此，混凝土回收应侧重于回收高质量的胶凝组分来替代熟料。这就要求从目前的传统回收技术转向创新的回收方法，不仅能够回收干净的二次骨料，还能回收残余胶凝细粒（RCF），从而消除与之相关的二氧化碳排放。RCF 的生产和升级再循环提供了新的实施途径，这在以前被认为是不可行的。然而，RCF 的特性可能因其来源而异，从而影响其替代和再循环潜力。因此，在拆除之前评估原始混凝土质量（重点是粘合剂类型）非常重要。手持式 X 射线荧光技术在这方面似乎大有可为。为了从原始胶凝成分中有效分离出干净的二次集料，需要采用创新的破碎和分离技术。此外，静电分离技术在进一步优化 RCF 方面也具有巨大的研究潜力。

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引用次数: 0

The impact of relative humidity on the nanoindentation relaxation in calcium silicate hydrates 相对湿度对硅酸钙水合物纳米压痕松弛的影响

CEMENT

Pub Date : 2024-10-16 DOI: 10.1016/j.cement.2024.100120

Zhao Chen , Jessy Frech-Baronet , Hang Tran , Luca Sorelli

Despite extensive research efforts, understanding the time-dependent behavior of concrete remains an enigma due to the complex nature of cement microstructure. In this study, the statistical nanoindentation was employed to investigate the influence of relative humidity (RH) on the relaxation behavior of calcium silicate hydrates (C-S-H) in a cement paste. Our experiments, performed at RH levels of 33 % and 86 %, revealed significant enhancements in both the indentation modulus and hardness of the C-S-H as RH increased. Remarkably, the internal water exerted a significant influence on the asymptotic relaxation behavior, displaying a clear power-law fashion. Further analysis identified the presence of short- and long-term viscoelastic behaviors within the C-S-H, distinguished by a transition observed within the initial seconds. These findings advance the understanding of nanoscale mechanisms driving concrete creep under different humidity conditions.

尽管进行了大量研究，但由于水泥微观结构的复杂性，对混凝土随时间变化的行为的理解仍然是一个谜。本研究采用统计纳米压痕法研究相对湿度（RH）对水泥浆中硅酸钙水合物（C-S-H）松弛行为的影响。我们在相对湿度为 33% 和 86% 的条件下进行的实验表明，随着相对湿度的增加，C-S-H 的压痕模量和硬度都有显著提高。值得注意的是，内部水分对渐进松弛行为产生了重大影响，呈现出明显的幂律模式。进一步分析发现，C-S-H 中存在短期和长期粘弹性行为，并在最初几秒钟内出现了过渡。这些发现加深了人们对不同湿度条件下混凝土徐变的纳米级驱动机制的理解。

引用次数: 0

Low-grade fly ash in portland cement blends: A decoupling approach to evaluate reactivity and hydration effects 硅酸盐水泥掺合料中的低标号粉煤灰：评估反应性和水化效应的解耦方法

CEMENT

Pub Date : 2024-10-04 DOI: 10.1016/j.cement.2024.100119

Qingxu Jin , Wenyu Liao , Xiaoqiang Ni , Hongyan Ma

Fly ash with low glass content is often prohibited from use in concrete due to the low reactivity and/or the inclusion of contaminants. However, the scarcity of high-quality fly ash promotes the evaluation of the feasibility of using fly ash with low glass content (e.g., low-grade fly ash) in concrete. This study proposes a decoupling method to quantitatively estimate the degree of reaction of fly ash with extremely low glass content, which partially replaces cement, and the degree of hydration of the hosting cement, simultaneously. The estimation is derived from the contents of calcium hydroxide and chemically bonded water in hydrated binary cement pastes, which can be determined by thermogravimetric analysis-based experiments and theoretically validated stoichiometric parameters. The results exhibit that the fly ash tends to retard the early-age hydration of cement but promotes its later-age hydration, resulting in a higher ultimate degree of reaction of cement than the reference paste. The microstructural and porosity evaluation shows that the fly ash, though has relatively low degrees of reaction due to its low glass content, can result in a more tortuous pore network of the hydrated pastes, which could be potentially more resistant to the penetration of water and aggressive chemicals.

玻璃含量低的粉煤灰由于反应活性低和/或含有污染物，通常被禁止用于混凝土中。然而，优质粉煤灰的稀缺促进了对在混凝土中使用低玻璃含量粉煤灰（如低等级粉煤灰）可行性的评估。本研究提出了一种解耦方法，可同时定量估算部分取代水泥的玻璃含量极低的粉煤灰的反应程度和宿主水泥的水化程度。估算值来自水化二元水泥浆中氢氧化钙和化学键水的含量，可通过基于热重分析的实验和理论验证的化学计量参数确定。结果表明，粉煤灰往往会延缓水泥的早期水化，但会促进其后期水化，从而使水泥的最终反应度高于参考浆体。微观结构和孔隙率评估结果表明，粉煤灰虽然因其玻璃含量低而反应度相对较低，但却能使水化浆料的孔隙网络更加曲折，从而可能更能抵御水和侵蚀性化学品的渗透。

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引用次数: 0

Accelerating effect of low replacements of carbonaceous materials in cement paste and mortar 水泥浆和砂浆中碳质材料低替代率的加速效应

CEMENT

Pub Date : 2024-09-30 DOI: 10.1016/j.cement.2024.100118

Victor Brial, Thomas Duplessis, Claudiane M. Ouellet-Plamondon

This study investigated the effect of incorporating small amounts of carbonaceous materials in cement paste and mortar systems at a low dosage. The materials studied include industrial graphite, natural graphite, carbon black, activated charcoal, and decolorized charcoal. The effect of this material on cement hydration through different techniques such as compressive strength mortar, TGA, SEM, isothermal calorimetry, rheology, and calcium isotherm adsoprtion. These tests studied the influence of carbonaceous materials’ properties on cement hydration. With the exception of industrial graphite G1, the carbonaceous materials showed an acceleration of setting after 1 day by favoring the nucleation of hydrates, reducing the porosity, and improving the mechanical properties. On the other hand, traces of this acceleration are no longer visible beyond 28 days. The accelerating effect of different carbons sources appears to be less dependent of crystallinity, mineralogy, or particle size, but rather on surface chemistry and the quality of particle dispersion.

本研究调查了在水泥浆和砂浆系统中加入少量低剂量碳质材料的效果。研究的材料包括工业石墨、天然石墨、炭黑、活性炭和脱色炭。通过不同的技术，如抗压强度砂浆、热重分析、扫描电镜、等温量热、流变学和钙等温吸附等，研究了这些材料对水泥水化的影响。这些测试研究了碳质材料的特性对水泥水化的影响。除工业石墨 G1 外，其他碳质材料在 1 天后通过促进水化物成核、降低孔隙率和改善机械性能，显示出加速凝结的作用。另一方面，这种加速的痕迹在 28 天后就不再明显。不同碳源的加速效果似乎与结晶度、矿物学或颗粒大小的关系不大，而是取决于表面化学和颗粒分散的质量。

引用次数: 0

Measuring concrete air-entraining admixture adsorption on coal ash using three-phase equilibrium and fluorescence-based methods 利用三相平衡法和荧光法测量煤灰对混凝土引气外加剂的吸附量

CEMENT

Pub Date : 2024-09-21 DOI: 10.1016/j.cement.2024.100115

Yujia Min , Erin Stewartson , Prannoy Suraneni , Christopher R. Shearer , R. Doug Hooton , Lisa E. Burris

This manuscript presents two novel methods of evaluating the adsorption of air-entraining admixtures (AEAs) by coal ashes used in cementitious mixtures. A developed three-phase equilibrium (TPE) method measures fly ash adsorption capacity accounting for carbon adsorption, Ca²⁺ interactions with AEA, and the equilibrium between the two. A fluorescence-based method (FBM) was also developed, utilizing a non-ionic NP-10 surfactant as a representative for AEA. This study verifies the applicability and accuracy of the TPE and FBM methods using seven class C and F coal ashes with a wide range of loss on ignition values, varying from 0.2 to 15.6 %, and three commercial AEAs. Verified with foam index test results, the TPE method was applicable to all tested AEAs and coal ashes. The results were consistent between the FBM and TPE methods when comparing rosin- and fatty acid-based AEAs, but less consistent when using a sulfonate-based AEA. These findings help us understand the applicability and limitations of the TPE and FBM methods and provide two methods for quantifying adsorption in fly ash samples.

本手稿介绍了两种评估水泥基混合物中使用的煤灰对引气外加剂（AEA）吸附情况的新方法。开发的三相平衡法 (TPE) 可测量粉煤灰的吸附能力，其中包括碳吸附、Ca2+ 与 AEA 的相互作用以及两者之间的平衡。利用非离子 NP-10 表面活性剂作为 AEA 的代表，还开发了一种基于荧光的方法 (FBM)。本研究使用七种 C 级和 F 级煤灰（着火损失值范围从 0.2% 到 15.6% 不等）以及三种商用 AEA，验证了 TPE 和 FBM 方法的适用性和准确性。经泡沫指数测试结果验证，TPE 方法适用于所有测试的 AEA 和煤灰。在比较松香基和脂肪酸基 AEA 时，FBM 法和 TPE 法的结果是一致的，但在使用磺酸盐基 AEA 时，结果则不太一致。这些发现有助于我们了解 TPE 和 FBM 方法的适用性和局限性，并为量化粉煤灰样品中的吸附性提供了两种方法。

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引用次数: 0

Phase evolution and performance of sodium sulfate-activated slag cement pastes 硫酸钠活化矿渣水泥浆的相变和性能

CEMENT

Pub Date : 2024-09-20 DOI: 10.1016/j.cement.2024.100117

Zengliang Yue , Yuvaraj Dhandapani , Samuel Adu-Amankwah , Susan A. Bernal

This study evaluates the reaction kinetics, phase assemblage, and microstructure evolution of Na₂SO₄-activated slag cements produced with three commercial slags. The main reaction products identified are ettringite and calcium aluminosilicate hydrates, alongside a poorly crystalline SO₄^2- intercalated Mg-Al-layered double hydroxide (LDH) phase. Results revealed that the Al₂O₃ slag content alone does not correlate with the cement performance. While pastes made with a higher Al₂O₃ content slag exhibit faster reaction kinetics, those made with a slag with a higher Mg/Al ratio developed superior compressive strength and reduced porosity over extended curing periods. Thermodynamic modelling simulations indicate that sulfate consumption occurs via ettringite and LDH phase formation, influencing the slag reaction degree, pH value, and porosity reduction in these cements. This research highlights the critical role of slag composition in controlling microstructure and, consequently, performance of sodium sulfate activated slag cement pastes.

本研究评估了使用三种商用矿渣生产的 Na2SO4 活性矿渣水泥的反应动力学、相组合和微观结构演变。发现的主要反应产物是乙长石和铝硅酸钙水合物，以及结晶度较低的 SO42-插层镁-铝层双氢氧化物（LDH）相。研究结果表明，矿渣中 Al2O3 的含量本身与水泥的性能并不相关。用 Al2O3 含量较高的矿渣制成的水泥浆反应动力学速度更快，而用 Mg/Al 比率较高的矿渣制成的水泥浆在较长的固化时间内抗压强度更高，孔隙率更低。热力学模型模拟表明，硫酸盐的消耗是通过乙长石和 LDH 相的形成而发生的，从而影响了这些水泥的炉渣反应度、pH 值和孔隙率的降低。这项研究强调了矿渣成分在控制硫酸钠活化矿渣水泥浆微观结构以及性能方面的关键作用。

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引用次数: 0

Prediction of strength activity index using chemical and physical properties of pozzolans 利用灰泥的化学和物理特性预测强度活性指数

CEMENT

Pub Date : 2024-09-18 DOI: 10.1016/j.cement.2024.100116

Farzaneh Elyasigorji, Habib Tabatabai

Reductions in cement use have essential benefits in reducing the embodied energy in concrete and CO₂ emissions. Hence, effective assessment of potential pozzolanic materials is highly desirable to facilitate usage as sustainable supplementary cementitious materials (SCMs). However, assessment of pozzolanic reactivity using conventional experimental tests is typically time-consuming and expensive. Pozzolanic reactivity is mainly related to the chemical and physical characteristics of various pozzolans, such as amorphous silica and alumina contents and specific surface area. This study develops and presents an equation that can predict the strength activity index (SAI) as an indirect method for the assessment of potential pozzolans and their strength outcome using their chemical and physical properties. The development of a prediction equation not only saves time and resources but also helps with designing optimized and improved pozzolanic SCMs. The strength activity index (SAI) of seven different materials with varying pozzolanic properties was measured at an age of 90 days. The powdered test materials included pottery cull, brick powder, lightweight aggregate fines, glass powder, silica fume, dolostone, and Class C fly ash. In the second stage, correlation analyses were performed to find parameters (based on chemical and physical properties) that were highly correlated with SAI. An equation was then developed as a function of the chemical and physical properties of raw pozzolanic materials using an optimization tool. Consequently, an equation predicting SAI was derived which had a high degree of correlation (R = 0.972) with measured SAI.

减少水泥用量对降低混凝土的内含能耗和二氧化碳排放量有着至关重要的益处。因此，对潜在的胶凝材料进行有效评估，以促进其作为可持续胶凝补充材料 (SCM) 的使用，是非常可取的。然而，使用传统的实验测试评估水青酸反应性通常既耗时又昂贵。胶凝反应性主要与各种胶凝剂的化学和物理特性有关，如无定形二氧化硅和氧化铝含量以及比表面积。本研究开发并提出了一个可以预测强度活性指数（SAI）的方程，作为一种间接方法，利用其化学和物理特性来评估潜在的胶凝剂及其强度结果。该预测方程的开发不仅节省了时间和资源，而且有助于设计优化和改良的胶凝单体材料。在 90 天的龄期内，测量了七种不同材料的强度活性指数（SAI），这些材料具有不同的水泥酚醛特性。粉状测试材料包括陶粒、砖粉、轻集料细粉、玻璃粉、硅灰、白云石和 C 级粉煤灰。在第二阶段，进行了相关性分析，以找到与 SAI 高度相关的参数（基于化学和物理特性）。然后，使用优化工具建立了一个等式，该等式是原始混合材料化学和物理特性的函数。因此，得出了一个预测 SAI 的等式，该等式与测得的 SAI 高度相关（R = 0.972）。

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引用次数: 0

Biomass ash (BA) waste as an activator to produce carbon-negative cement 生物质灰（BA）废料作为生产负碳水泥的活化剂

CEMENT

Pub Date : 2024-09-18 DOI: 10.1016/j.cement.2024.100112

Zehao Lei, Sara Pavia

The use of biomass, as a renewable energy source, to run heating and power plants is propelled by sustainable European policy. Olive is an important resource in Mediterranean countries. The residues from the extraction of olive oil are used as biomass, either to produce the oil or to generate heat or electricity. The disposal of ash residue poses an important burden. This study uses olive pit bottom ash waste (OBA) to produce carbon-negative cement. The OBA is mixed with waste GGBS (GGBS), and neither calcination nor thermal curing are used to lower environmental impact.

The cements produced contain up to 60 %OBA and have a carbon sequestration capacity up to -97.45 kg CO₂e/m³. An optimum mix with 40 %OBA is developed (using auxiliary activator), with compressive strength of 36–44 MPa and a carbon sequestration capacity of 40–45 kg CO₂/m³. A modified loss on ignition test is proposed to evaluate the embodied carbon of biomass ash.

The OBA's main chemical constituents: K₂O and CaO, afford outstanding activation and alkalinity to release Ca²⁺ Si⁴⁺ and Al³⁺ from GGBS to form calcite, hydrotalcite, C-(A)-S-H and amorphous cements. Using sodium carbonate (NC) and lime as supplementary activators enhanced the mechanical properties of the cements and slightly changed their composition and microstructure. NC is the most efficient activator, it increased dissolution, and produced a denser and stronger cement with higher Si and K concentration that includes gaylussite, N-A-S-H and C(K)-A-S-H. Pre-dissolving the NC prior to mixing increases the activator's efficiency, producing less calcite cement for the same amount of NC. By adding 4 % pre-dissolved NC, the compressive strength increased by 138.76 % (compared to OBA-GGBS mortar without auxiliary activators) and 113.94 % compared to the material with NC in powder form.

生物质能作为一种可再生能源，在欧洲可持续发展政策的推动下用于供热和发电厂。橄榄是地中海国家的重要资源。榨取橄榄油的残渣被用作生物质能源，既可以用来生产橄榄油，也可以用来供热或发电。灰渣的处理是一项重要负担。本研究利用橄榄油坑底灰渣（OBA）生产负碳水泥。OBA 与废弃 GGBS（GGBS）混合，既不煅烧也不热固化，以降低对环境的影响。所生产的水泥含有高达 60% 的 OBA，固碳能力高达 -97.45 kg CO2e/m3。开发出一种含 40 %OBA 的最佳混合物（使用辅助活化剂），其抗压强度为 36-44 兆帕，固碳能力为 40-45 千克二氧化碳/立方米。提出了一种改进的点火损失试验来评估生物质灰烬的含碳量：OBA 的主要化学成分：K2O 和 CaO 具有出色的活化和碱度，可从 GGBS 中释放 Ca2+ Si4+ 和 Al3+，形成方解石、水滑石、C-(A)-S-H 和无定形水泥。使用碳酸钠（NC）和石灰作为辅助活化剂可提高水泥的机械性能，并轻微改变水泥的成分和微观结构。碳酸钠是最有效的活化剂，它能增加溶解度，并产生一种更致密、更坚固的水泥，其中硅和钾的浓度更高，包括基质、N-A-S-H 和 C（K）-A-S-H。在混合前预溶解 NC 可提高活化剂的效率，在使用相同数量 NC 的情况下，可生产出更少的方解石水泥。通过添加 4% 的预溶解 NC，抗压强度提高了 138.76%（与不添加辅助活化剂的 OBA-GGBS 砂浆相比），与添加粉末状 NC 的材料相比，抗压强度提高了 113.94%。

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引用次数: 0

Multi-year cementitious hydrate product formation in non-Portland high performance concretes 非硅酸盐高性能混凝土中多年形成的水泥基水合物产品

CEMENT

Pub Date : 2024-09-05 DOI: 10.1016/j.cement.2024.100111

Daniel A. Geddes , Brant Walkley , Taku Matsuda , John L. Provis

This paper describes the hydration products and microstructural formation processes that yield excellent mechanical properties in “zero-cement concretes” (ZCC) produced by chemical activation of a blend of silica fume, blast furnace slag, and fly ash, using a CaO-rich additive (commercially supplied as an expansive agent but taking a chemical activation role here), a high superplasticizer dose, and a very low water content. These concretes reach 70 MPa at 28 days and then continue to gain strength beyond 150 MPa after 5 years, either under sealed conditions or exposed on a rooftop in the climate of Tokyo, Japan. The reaction products of ZCC are dominated by C-A-S-H gel, accompanied by aluminate hydrates of different layered double hydroxide forms; this unconventional cementitious blend yields reaction products that are familiar from Portland cement and blended binder systems. The ferronickel slag used as fine aggregate in these mixes makes an important contribution to the balance of fresh-state and hardened-state properties by modifying hydration chemistry.

本文介绍了硅灰、高炉矿渣和粉煤灰混合物经化学活化后产生的 "零水泥混凝土"（ZCC）中产生优异力学性能的水化产物和微结构形成过程，该过程中使用了富含氧化钙的添加剂（商业上作为膨胀剂供应，但在本文中起化学活化作用）、高剂量的超塑化剂和极低的含水量。这些混凝土在 28 天时强度达到 70 兆帕，5 年后强度继续增加，超过 150 兆帕，无论是在密封条件下还是暴露在日本东京气候条件下的屋顶上。ZCC 的反应产物以 C-A-S-H 凝胶为主，并伴有不同层状双氢氧化物形式的铝酸盐水合物；这种非常规的水泥基掺合料产生了波特兰水泥和混合粘结剂系统中常见的反应产物。在这些混合料中作为细骨料使用的镍铁矿渣通过改变水化化学反应，对新态性和硬化态性的平衡做出了重要贡献。

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引用次数: 0

Estimation of cement paste stiffness and UHPC elastic modulus through measured phase-property upscaling 通过测量的相位特性放大估算水泥浆刚度和超高强度混凝土弹性模量

CEMENT

Pub Date : 2024-08-09 DOI: 10.1016/j.cement.2024.100110

Charissa Puttbach, Gary S. Prinz, Cameron D. Murray

The elastic stiffness of bulk concrete materials results from the complex interaction of aggregates, voids, and hydrated cement (which can have multiple hardened phases at multiple length scales). Given the complexities associated with understanding the arrangement of these particles within bulk concrete volumes, estimations for elastic modulus often rely on empirical correlations with unit weight and compressive strength. Such estimations are inherently scale-dependent and fail to capture variability in mix designs, particularly the variability found in specialty concrete mixes. To develop a scale-independent method for estimating elastic modulus from mix-design volume fraction information, this study explores a novel bottom-up approach using cement paste phase stiffness values determined through micro-mechanical experimentation and randomized Monte-Carlo spring arrangement simulations. Statistical representations of cement paste phase stiffness distributions and bulk volume fraction data are combined to provide estimations for elastic stiffness in both the composite cement paste and bulk concrete containing fine aggregate and fibers. Resulting a priori estimations of UHPC cement paste stiffness from the micro-mechanical upscaling simulations were within 4% of measured values (based on mix-design and void volume fraction information alone) for a selected sample of mix proportions. When applied to the two UHPC mixes containing fibers and fine aggregate, upscaling simulations consistently overpredicted the measured elastic modulus, likely due to the aggregate-cement interfacial transition zone (ITZ) properties that were not captured in the micro-mechanical testing.

大体积混凝土材料的弹性刚度是由骨料、空隙和水化水泥（在多个长度尺度上可能有多个硬化阶段）的复杂相互作用产生的。由于了解这些颗粒在大体积混凝土中的排列很复杂，弹性模量的估算通常依赖于与单位重量和抗压强度的经验相关性。这种估算方法本质上依赖于规模，无法捕捉混合设计中的变化，特别是特种混凝土混合料中的变化。为了开发一种与规模无关的方法，从混合设计体积分数信息中估算弹性模量，本研究探索了一种自下而上的新方法，使用通过微机械实验和随机蒙特卡洛弹簧布置模拟确定的水泥浆相刚度值。水泥浆相刚度分布的统计表示法与大体积分数数据相结合，对复合水泥浆和含有细骨料和纤维的大体积混凝土的弹性刚度进行了估算。在选定的混合比例样本中，通过微观机械放大模拟对超高强度混凝土水泥浆刚度的先验估算结果与测量值（仅基于混合设计和空隙体积分数信息）的误差在 4% 以内。当应用于含有纤维和细集料的两种 UHPC 混合料时，升级模拟始终高估了测量弹性模量，这可能是由于集料-水泥界面过渡区 (ITZ) 的特性未在微观力学测试中捕捉到。

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引用次数: 0