Pub Date : 2025-10-08DOI: 10.1016/j.cemconres.2025.108058
Beifeng Lv , Lizhong Wang , Qiang Zeng , Hengyu Liu , Yujie Li , Zhen Guo
This work seeks to explore the mechanisms of superabsorbent polymers (SAP) in mitigating autogenous shrinkage of an alkali-activated ground granulated blast furnace slag-fly ash (GGBFS-FA) binary binder through elaborate microstructural analysis. The effect patterns of SAP with different dosages (0–0.5 %) and particle sizes (91–631 μm) on the setting time, workability, mechanical strength and autogenous shrinkage were tested. Porosity, pore size distribution, specific surface area, and chemical characteristics were systematically explored. Results revealed that 0.5 % SAP interrupted capillary stress through pore coarsening, thereby reducing autogenous shrinkage by 80 % (3266.57 to 637.89 με). Smaller SAP particle (91 μm) enhanced water release efficiency and promoted calcium silicoaluminate hydrate (C-(A)-S-H) gel formation, while larger SAP particle (631 μm) delayed water release and improved strength with slower shrinkage stabilization. The findings on the water release characteristics and pore coarsening mechanism of SAP deepen our understanding of autogenous shrinkage controls in alkali-activated materials (AAM).
{"title":"Autogenous shrinkage mitigation effect of superabsorbent polymers on alkali-activated GGBFS-FA binary binder without additional water: performance, microstructure and mechanism","authors":"Beifeng Lv , Lizhong Wang , Qiang Zeng , Hengyu Liu , Yujie Li , Zhen Guo","doi":"10.1016/j.cemconres.2025.108058","DOIUrl":"10.1016/j.cemconres.2025.108058","url":null,"abstract":"<div><div>This work seeks to explore the mechanisms of superabsorbent polymers (SAP) in mitigating autogenous shrinkage of an alkali-activated ground granulated blast furnace slag-fly ash (GGBFS-FA) binary binder through elaborate microstructural analysis. The effect patterns of SAP with different dosages (0–0.5 %) and particle sizes (91–631 μm) on the setting time, workability, mechanical strength and autogenous shrinkage were tested. Porosity, pore size distribution, specific surface area, and chemical characteristics were systematically explored. Results revealed that 0.5 % SAP interrupted capillary stress through pore coarsening, thereby reducing autogenous shrinkage by 80 % (3266.57 to 637.89 με). Smaller SAP particle (91 μm) enhanced water release efficiency and promoted calcium silicoaluminate hydrate (C-(A)-S-H) gel formation, while larger SAP particle (631 μm) delayed water release and improved strength with slower shrinkage stabilization. The findings on the water release characteristics and pore coarsening mechanism of SAP deepen our understanding of autogenous shrinkage controls in alkali-activated materials (AAM).</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108058"},"PeriodicalIF":13.1,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145247349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-04DOI: 10.1016/j.cemconres.2025.108053
Tarek Ihaddadene, Jérôme Claverie, François Bignonnet, Ouali Amiri
Calcium silicate hydrate (C-S-H) gel is an amorphous material with a complex, disordered structure that complicates the understanding of its atomic-scale properties. While many studies have investigated ionic diffusion in C-S-H pores, the behavior of sodium ( ) and chloride ( ) ions, particularly in relation to the Ca/Si ratio, is not well understood. In this study, atomistic models of C-S-H were developed with varying Ca/Si ratios, pore sizes, and NaCl concentrations. Molecular dynamics simulations were used to calculate the self-diffusion profiles of and ions. Results indicate that pore size strongly affects diffusivity and adsorption through confinement and electrical double layer effects. The solid surface influences ionic mobility up to approximately 1.2 nm. The Ca/Si ratio has minimal impact on the diffusion profiles of non-adsorbed ions, but its rise enhances mobility near the surface and increases chloride binding capacity, consistent with prior studies.
{"title":"Diffusion and physicochemical behavior of chloride and sodium ions in C-S-H gel pores : A molecular dynamics investigation","authors":"Tarek Ihaddadene, Jérôme Claverie, François Bignonnet, Ouali Amiri","doi":"10.1016/j.cemconres.2025.108053","DOIUrl":"10.1016/j.cemconres.2025.108053","url":null,"abstract":"<div><div>Calcium silicate hydrate (C-S-H) gel is an amorphous material with a complex, disordered structure that complicates the understanding of its atomic-scale properties. While many studies have investigated ionic diffusion in C-S-H pores, the behavior of sodium ( <figure><img></figure> ) and chloride ( <figure><img></figure> ) ions, particularly in relation to the Ca/Si ratio, is not well understood. In this study, atomistic models of C-S-H were developed with varying Ca/Si ratios, pore sizes, and NaCl concentrations. Molecular dynamics simulations were used to calculate the self-diffusion profiles of <figure><img></figure> and <figure><img></figure> ions. Results indicate that pore size strongly affects diffusivity and adsorption through confinement and electrical double layer effects. The solid surface influences ionic mobility up to approximately 1.2 nm. The Ca/Si ratio has minimal impact on the diffusion profiles of non-adsorbed ions, but its rise enhances <figure><img></figure> mobility near the surface and increases chloride binding capacity, consistent with prior studies.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108053"},"PeriodicalIF":13.1,"publicationDate":"2025-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The addition of Bauxite residue in the raw mix introduces Na+ and Ti4+ into the crystalline phases of calcium-sulfoaluminate (CSA) clinkers. To mimic such a system, Na-Fe-ye'elimite (C₃.₉N₀.₁A₂.₈F₀.₂Ŝ) and Ti-ferrite (C₂F₀.₇₆A₀.₂₄T₀.₁) were synthesized at 1285 °C, 2 h, and 1320 °C, 3 h, respectively. Quantitative X-ray diffraction (QXRD) revealed solid solutions with minor Ca-aluminates phases, whereas electron backscattered diffraction-energy dispersive spectroscopy (EBSD-EDS) could distinguish Na-rich orthorhombic and Fe-rich cubic ye'elimite polymorphs. Isothermal calorimetry showed the Na-Fe-ye'elimite phase drives early heat evolution, whereas higher ferrite and gypsum (M > 0) prolong induction and attenuate the main hydration peak. In ferrite-free mixes, the cubic-ye'elimite polymorph dissolves fastest, but when ferrite exceeds 33 wt%, its Fe3+ release accelerates orthorhombic-ye'elimite dissolution, as confirmed by pore-solution analysis. After 28d, Na-Fe-ye'elimite is fully consumed at M (sulfate to ye'elimite molar ratio) ≥ 2 for ye'elimite-ferrite mixes, while ferrite remains partly inert, possibly from Ca2+/SO₄2− adsorb onto its FeAl surface. Limiting ferrite to ≤33 wt% is recommended to achieve more densification of the microstructure for better performance.
{"title":"Exploring the hydration potential and kinetics of Na-Ye'elimite and Ti-Ferrite solid solutions","authors":"Rahul Roy , Tobias Hertel , Christiane Rößler , Yiannis Pontikes","doi":"10.1016/j.cemconres.2025.108046","DOIUrl":"10.1016/j.cemconres.2025.108046","url":null,"abstract":"<div><div>The addition of Bauxite residue in the raw mix introduces Na<sup>+</sup> and Ti<sup>4+</sup> into the crystalline phases of calcium-sulfoaluminate (CSA) clinkers. To mimic such a system, Na-Fe-ye'elimite (C₃.₉N₀.₁A₂.₈F₀.₂Ŝ) and Ti-ferrite (C₂F₀.₇₆A₀.₂₄T₀.₁) were synthesized at 1285 °C, 2 h, and 1320 °C, 3 h, respectively. Quantitative X-ray diffraction (QXRD) revealed solid solutions with minor Ca-aluminates phases, whereas electron backscattered diffraction-energy dispersive spectroscopy (EBSD-EDS) could distinguish Na-rich orthorhombic and Fe-rich cubic ye'elimite polymorphs. Isothermal calorimetry showed the Na-Fe-ye'elimite phase drives early heat evolution, whereas higher ferrite and gypsum (M > 0) prolong induction and attenuate the main hydration peak. In ferrite-free mixes, the cubic-ye'elimite polymorph dissolves fastest, but when ferrite exceeds 33 wt%, its Fe<sup>3+</sup> release accelerates orthorhombic-ye'elimite dissolution, as confirmed by pore-solution analysis. After 28d, Na-Fe-ye'elimite is fully consumed at M (sulfate to ye'elimite molar ratio) ≥ 2 for ye'elimite-ferrite mixes, while ferrite remains partly inert, possibly from Ca<sup>2+</sup>/SO₄<sup>2−</sup> adsorb onto its Fe<img>Al surface. Limiting ferrite to ≤33 wt% is recommended to achieve more densification of the microstructure for better performance.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108046"},"PeriodicalIF":13.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145194949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-30DOI: 10.1016/j.cemconres.2025.108047
Mohammed Krameche , William Wilson , Arezki Tagnit-Hamou
Investigating the microstructure of ordinary Portland cement (OPC) paste using X-ray micro-computed tomography (μ-CT) requires optimized acquisition and precise image segmentation to reliably differentiate phases. μ-CT image segmentation is challenged by the heterogeneous microstructure and limited contrast between microstructure phases in the X-ray linear attenuation coefficient. Conventional gray scale value thresholding often misclassifies phases, while previous machine learning (ML) approaches have relied on manually labeled training leading to subjectivity and replicability issues. This study proposes an innovative μ-CT image segmentation method for OPC paste, leveraging chemical information from quantitative energy dispersive spectroscopy (QEDS) mapping. The method workflow involves five steps: (1) μ-CT imaging to capture the 3D microstructure, (2) scanning electron microscopy backscattered electron (SEM-BSE) imaging and QEDS mapping to generate 2D phase maps, (3) image registration to align QEDS phase maps with μ-CT images, (4) phase separability optimization using denoising and sharpening of the μ-CT images, and (5) ML-based segmentation using the random forest approach and training labels from QEDS-derived phase maps. The proposed method effectively differentiates portlandite from hydrates matrix, as well as ferrite from clinker phases. This paper further details two main applications of the method: (1) quantification of phase assemblage, hydration degree, and particle size distribution (PSD) of residual anhydrous phases, with results compared to thermodynamic modeling, and (2) the first-ever comprehensive quantitative microstructural characterization of a grid of 32 microcube samples, revealing spatial heterogeneity in phase fractions, porosity, particle counts, and microcube volumes. These results provide critical input for calibrating and validating micromechanical upscaling models.
{"title":"Coupling EDS hypermaps and X-ray microtomography for advanced 3D microstructure characterization of cement paste: A step forward in multiscale modeling","authors":"Mohammed Krameche , William Wilson , Arezki Tagnit-Hamou","doi":"10.1016/j.cemconres.2025.108047","DOIUrl":"10.1016/j.cemconres.2025.108047","url":null,"abstract":"<div><div>Investigating the microstructure of ordinary Portland cement (OPC) paste using X-ray micro-computed tomography (μ-CT) requires optimized acquisition and precise image segmentation to reliably differentiate phases. μ-CT image segmentation is challenged by the heterogeneous microstructure and limited contrast between microstructure phases in the X-ray linear attenuation coefficient. Conventional gray scale value thresholding often misclassifies phases, while previous machine learning (ML) approaches have relied on manually labeled training leading to subjectivity and replicability issues. This study proposes an innovative μ-CT image segmentation method for OPC paste, leveraging chemical information from quantitative energy dispersive spectroscopy (QEDS) mapping. The method workflow involves five steps: (1) μ-CT imaging to capture the 3D microstructure, (2) scanning electron microscopy backscattered electron (SEM-BSE) imaging and QEDS mapping to generate 2D phase maps, (3) image registration to align QEDS phase maps with μ-CT images, (4) phase separability optimization using denoising and sharpening of the μ-CT images, and (5) ML-based segmentation using the random forest approach and training labels from QEDS-derived phase maps. The proposed method effectively differentiates portlandite from hydrates matrix, as well as ferrite from clinker phases. This paper further details two main applications of the method: (1) quantification of phase assemblage, hydration degree, and particle size distribution (PSD) of residual anhydrous phases, with results compared to thermodynamic modeling, and (2) the first-ever comprehensive quantitative microstructural characterization of a grid of 32 microcube samples, revealing spatial heterogeneity in phase fractions, porosity, particle counts, and microcube volumes. These results provide critical input for calibrating and validating micromechanical upscaling models.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108047"},"PeriodicalIF":13.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-30DOI: 10.1016/j.cemconres.2025.108043
Maxime Ranger , Andreas Leemann , Benoit Fournier
Concrete specimens containing two aggregates susceptible to alkali-silica reaction (ASR) and various supplementary cementitious materials (SCMs) have been exposed outdoors since 1992. After 30 years of expansion monitoring, some specimens were cored to conduct an in-depth analysis of their condition.
The chemical compositions of the hydrates and the ASR products were quantified with SEM-EDS. All SCMs increased the Si/Ca of the C-(A)-S-H, but the extent varied depending on their composition, amount and degree of reaction. Larger amounts of SCMs resulted in lower degrees of reaction.
The ASR products inside aggregate particles of non-boosted concrete mixtures were crystalline. Their Ca/Si was in the range 0.21–0.24, independent of the binder and the aggregate types. The (Na + K)/Ca was usually in the range 0.31–0.35. The Na/K varied more, correlating with the respective ratios in the binder. The Al content of the ASR products inside aggregate particles was not influenced by the presence of Al-rich SCMs.
{"title":"An ASR exposure site after 30 years – Chemical composition of hydrates and ASR products","authors":"Maxime Ranger , Andreas Leemann , Benoit Fournier","doi":"10.1016/j.cemconres.2025.108043","DOIUrl":"10.1016/j.cemconres.2025.108043","url":null,"abstract":"<div><div>Concrete specimens containing two aggregates susceptible to alkali-silica reaction (ASR) and various supplementary cementitious materials (SCMs) have been exposed outdoors since 1992. After 30 years of expansion monitoring, some specimens were cored to conduct an in-depth analysis of their condition.</div><div>The chemical compositions of the hydrates and the ASR products were quantified with SEM-EDS. All SCMs increased the Si/Ca of the C-(A)-S-H, but the extent varied depending on their composition, amount and degree of reaction. Larger amounts of SCMs resulted in lower degrees of reaction.</div><div>The ASR products inside aggregate particles of non-boosted concrete mixtures were crystalline. Their Ca/Si was in the range 0.21–0.24, independent of the binder and the aggregate types. The (Na + K)/Ca was usually in the range 0.31–0.35. The Na/K varied more, correlating with the respective ratios in the binder. The Al content of the ASR products inside aggregate particles was not influenced by the presence of Al-rich SCMs.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108043"},"PeriodicalIF":13.1,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145189517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-29DOI: 10.1016/j.cemconres.2025.108052
Xin Liu , Dining Li , Hui Xie , Jiachen Yao , Xuyan Shen , Haochuan Wang , Zhengyao Qu , Zuhua Zhang , Pan Feng
Alkali-free aluminum sulfate (AS)-based accelerators have become a widely adopted and indispensable admixture for shotcrete applications. However, their effects on the formation kinetics and properties of calcium silicate hydrate (C-S-H) – the primary hydrate in shotcrete – remain insufficiently understood. To bridge this knowledge gap, a combination of isothermal calorimetry, QXRD, and TGA was employed to uncover the temporal evolution of C-S-H. In addition, the chemical compositions and silicate chain structure were comprehensively examined using BSE-EDS, 27Al NMR, coupled with 29Si NMR techniques. Our results demonstrate that AS addition accelerated C3S hydration, promoting the C-S-H nucleation and growth rate. This acceleration effect can be ascribed to (1) the accelerated dissolution of silicate phases at early stages, and (2) the formation of divergent C-S-H needles, providing more nucleation sites while mitigating impingement between adjacent C-(A)-S-H needles. Multiple characterizations confirmed the enhanced incorporation of aluminum into C-S-H, predominately at the bridging site. Notably, increasing AS content decreased the Si/Ca of the C-(A)-S-H and concurrently enhanced the aluminum incorporation. This compositional shift led to the formation of longer aluminosilicate chains and concomitant improvements in the hardness and elastic modulus of C-(A)-S-H. These findings offer valuable insights into AS-induced alterations in C-(A)-S-H within accelerated cement pastes, facilitating the deeper understanding of the role of C-(A)-S-H in strength development and long-term durability of shotcrete.
无碱硫酸铝（AS）基促进剂已成为喷射混凝土应用中广泛采用的不可缺少的掺合料。然而，它们对水合硅酸钙（C-S-H）的形成动力学和性质的影响（水合硅酸钙是喷射混凝土中的主要水合物）仍然没有得到充分的了解。为了弥补这一知识差距，采用等温量热法、QXRD和TGA相结合的方法揭示了C-S-H的时间演化。此外，利用BSE-EDS、27Al核磁共振和29Si核磁共振技术对化合物的化学成分和硅酸盐链结构进行了全面分析。结果表明，AS的加入加速了C3S的水化，促进了C-S-H的成核和生长速度。这种加速效应可以归结为：(1)早期硅酸盐相的加速溶解；(2)分散的C- s - h针的形成，提供了更多的成核位点，同时减轻了相邻C-(A)- s - h针之间的碰撞。多种表征证实了铝在C-S-H中的增强结合，主要是在桥接部位。AS含量的增加降低了C-(A)- s - h的Si/Ca，同时增加了铝的掺入。这种成分的转变导致形成了更长的铝硅酸盐链，并随之提高了C-(A)- s - h的硬度和弹性模量。这些发现为加速水泥浆中as诱导的C-(A)- s - h的变化提供了有价值的见解，有助于更深入地了解C-(A)- s - h在喷射混凝土强度发展和长期耐久性中的作用。
{"title":"How does aluminum sulfate-based alkali-free accelerator affect calcium silicate hydrate (C-S-H) formation in accelerated cement pastes?","authors":"Xin Liu , Dining Li , Hui Xie , Jiachen Yao , Xuyan Shen , Haochuan Wang , Zhengyao Qu , Zuhua Zhang , Pan Feng","doi":"10.1016/j.cemconres.2025.108052","DOIUrl":"10.1016/j.cemconres.2025.108052","url":null,"abstract":"<div><div>Alkali-free aluminum sulfate (AS)-based accelerators have become a widely adopted and indispensable admixture for shotcrete applications. However, their effects on the formation kinetics and properties of calcium silicate hydrate (C-S-H) – the primary hydrate in shotcrete – remain insufficiently understood. To bridge this knowledge gap, a combination of isothermal calorimetry, QXRD, and TGA was employed to uncover the temporal evolution of C-S-H. In addition, the chemical compositions and silicate chain structure were comprehensively examined using BSE-EDS, <sup>27</sup>Al NMR, coupled with <sup>29</sup>Si NMR techniques. Our results demonstrate that AS addition accelerated C<sub>3</sub>S hydration, promoting the C-S-H nucleation and growth rate. This acceleration effect can be ascribed to (1) the accelerated dissolution of silicate phases at early stages, and (2) the formation of divergent C-S-H needles, providing more nucleation sites while mitigating impingement between adjacent C-(A)-S-H needles. Multiple characterizations confirmed the enhanced incorporation of aluminum into C-S-H, predominately at the bridging site. Notably, increasing AS content decreased the Si/Ca of the C-(A)-S-H and concurrently enhanced the aluminum incorporation. This compositional shift led to the formation of longer aluminosilicate chains and concomitant improvements in the hardness and elastic modulus of C-(A)-S-H. These findings offer valuable insights into AS-induced alterations in C-(A)-S-H within accelerated cement pastes, facilitating the deeper understanding of the role of C-(A)-S-H in strength development and long-term durability of shotcrete.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108052"},"PeriodicalIF":13.1,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145183117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-29DOI: 10.1016/j.cemconres.2025.108049
Yanxin Hao , Xing Yin , Qinghua Li , Shilang Xu
High-strength ultra-high toughness cementitious composites (HS-UHTCC) are advanced materials characterized by a combination of high compressive strength and remarkable tensile ductility. In this study, the triaxial compressive behavior of HS-UHTCC reinforced with hybrid steel-polyethylene fibers was experimentally investigated under confining pressures up to 120 MPa. The results demonstrated that HS-UHTCC specimens predominantly exhibited oblique shear failure under triaxial loading. With increasing confining pressure, the deviatoric strength, axial/ lateral strain at peak load all increased. Peak stress increased by 244.54 % and 276.20 % as confining pressure increased up to 120 MPa for various fiber hybridizations. Notably, when the confining pressure exceeded 100 MPa, the material ceased to soften and instead exhibited ductile behavior. Among the classical failure criteria studied, both the Power-Law and Willam-Warnke criteria successfully captured the triaxial strength envelope of HS-UHTCC. Finally, a pressure-dependent constitutive model was proposed to characterize the pre-peak hardening, post-peak softening, and brittle-to-ductile transition of HS-UHTCC.
{"title":"Triaxial compressive behavior of high-strength strain-hardening fiber-reinforced cementitious composites: Fiber hybridization effect and constitutive relations","authors":"Yanxin Hao , Xing Yin , Qinghua Li , Shilang Xu","doi":"10.1016/j.cemconres.2025.108049","DOIUrl":"10.1016/j.cemconres.2025.108049","url":null,"abstract":"<div><div>High-strength ultra-high toughness cementitious composites (HS-UHTCC) are advanced materials characterized by a combination of high compressive strength and remarkable tensile ductility. In this study, the triaxial compressive behavior of HS-UHTCC reinforced with hybrid steel-polyethylene fibers was experimentally investigated under confining pressures up to 120 MPa. The results demonstrated that HS-UHTCC specimens predominantly exhibited oblique shear failure under triaxial loading. With increasing confining pressure, the deviatoric strength, axial/ lateral strain at peak load all increased. Peak stress increased by 244.54 % and 276.20 % as confining pressure increased up to 120 MPa for various fiber hybridizations. Notably, when the confining pressure exceeded 100 MPa, the material ceased to soften and instead exhibited ductile behavior. Among the classical failure criteria studied, both the Power-Law and Willam-Warnke criteria successfully captured the triaxial strength envelope of HS-UHTCC. Finally, a pressure-dependent constitutive model was proposed to characterize the pre-peak hardening, post-peak softening, and brittle-to-ductile transition of HS-UHTCC.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108049"},"PeriodicalIF":13.1,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145183118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-27DOI: 10.1016/j.cemconres.2025.108048
Kaidong Han , Tengfei Guo , Fei Meng , Yandong Guo , Xin Shu , Qianping Ran
The much-complicated physical and chemical modification effects induced by PCE pose significant challenges in elucidating the role of C3A hydration in structural build-up. The research reveals a two-stage structural build-up in C3A-gypsum-CaCO₃ pastes, wherein varying dosages of PCE significantly influence the dynamics. The dominant driving force of structural build-up is the enhancement of colloidal interparticle bonds among bare surfaces. PCE weakens these bonds strength through steric hindrance and reduces the increment of number of these bonds due to its preferential adsorption on surfaces of ettringite formed in the solution. We identify two distinct structural build-up rates: a logarithmic growth rate (GAFt) associated with the number of bonds between bare surfaces, and a linear growth rate (Gthix) linked to bond strength. As PCE preferentially adsorbs onto C3A particles, the reduction in GAFt occurs more rapidly than that of Gthix with increasing surface coverage, which causes the dominant driving force during the first stage to shift from bond number to bond strength. Consequently, the strengthening of these bonds remains the predominant factor throughout the structural development with escalating PCE dosages, explaining why, at higher PCE levels, a coherent developmental pattern is observable across both stages.
{"title":"New insight into structural build-up modification by PCE superplasticizers during early C3A hydration","authors":"Kaidong Han , Tengfei Guo , Fei Meng , Yandong Guo , Xin Shu , Qianping Ran","doi":"10.1016/j.cemconres.2025.108048","DOIUrl":"10.1016/j.cemconres.2025.108048","url":null,"abstract":"<div><div>The much-complicated physical and chemical modification effects induced by PCE pose significant challenges in elucidating the role of C<sub>3</sub>A hydration in structural build-up. The research reveals a two-stage structural build-up in C<sub>3</sub>A-gypsum-CaCO₃ pastes, wherein varying dosages of PCE significantly influence the dynamics. The dominant driving force of structural build-up is the enhancement of colloidal interparticle bonds among bare surfaces. PCE weakens these bonds strength through steric hindrance and reduces the increment of number of these bonds due to its preferential adsorption on surfaces of ettringite formed in the solution. We identify two distinct structural build-up rates: a logarithmic growth rate (<em>G</em><sub>AFt</sub>) associated with the number of bonds between bare surfaces, and a linear growth rate (<em>G</em><sub>thix</sub>) linked to bond strength. As PCE preferentially adsorbs onto C<sub>3</sub>A particles, the reduction in <em>G</em><sub>AFt</sub> occurs more rapidly than that of <em>G</em><sub>thix</sub> with increasing surface coverage, which causes the dominant driving force during the first stage to shift from bond number to bond strength. Consequently, the strengthening of these bonds remains the predominant factor throughout the structural development with escalating PCE dosages, explaining why, at higher PCE levels, a coherent developmental pattern is observable across both stages.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108048"},"PeriodicalIF":13.1,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145181259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-24DOI: 10.1016/j.cemconres.2025.108036
Diego Vallina , Isabel Santacruz , Alejandro Morales-Cantero , María Dolores Rodríguez-Ruiz , Ana Cuesta , Angeles G. De la Torre , Alessandro Dalla-Libera , Pere Borralleras , Sébastien Dhers , Peter Schwesig , Oliver Mazanec , Miguel A.G. Aranda
This study seeks to push the limits of LC3-50 binders by utilising low-grade kaolinite clays and C-S-H gel nucleation seeding. Four commercially-available kaolinite clays (i.e. kaolinite contents ~20 wt%) have been studied by X-ray fluorescence, X-ray powder diffraction and thermal analysis. The clays were thermally activated and milled to Dv,50 = 11 ± 2 μm. The activated clays showed low pozzolanic performances, as determined by ASTM C1897-20 standard. The heat flows ranged 200–230 J/g calcined clay and the bound waters 4.3–5.7 %. The LC3-50 pastes were characterised by calorimetry, X-ray powder diffraction and the Rietveld method, thermal analysis, and porosimetry to evaluate pozzolanic reactivity and the seeding effect.
LC3 mortars, w/b = 0.40, have relatively low compressive strengths, especially at one day, but these values were increased by 64 % on average at one day by seeding. At 1 day, three LC3 mortars showed 11 MPa which increased to 18–20 MPa by seeding. A fourth mortar showed a much higher compressive strength, 16 MPa, that increased to 23 MPa, by seeding. A tested concrete, w/b = 0.50, also showed a high increase of 37 % at 1 day. The improvements at 28 days were maintained but quantitatively lower, 12 and 14 % for the mortars and the concrete, respectively. Insights into the pozzolanic reactions and C-S-H seeding are obtained from the quantitative study of the pastes. For instance, it is proven the pozzolanic reaction at 1 day from the portlandite consumption. Also shown is the enhanced formation of carboaluminates when the strength enhancing admixture is added.
{"title":"Low-grade kaolinitic clays as SCMs for low-carbon cements and strength improvement by C-S-H gel nucleation seeding","authors":"Diego Vallina , Isabel Santacruz , Alejandro Morales-Cantero , María Dolores Rodríguez-Ruiz , Ana Cuesta , Angeles G. De la Torre , Alessandro Dalla-Libera , Pere Borralleras , Sébastien Dhers , Peter Schwesig , Oliver Mazanec , Miguel A.G. Aranda","doi":"10.1016/j.cemconres.2025.108036","DOIUrl":"10.1016/j.cemconres.2025.108036","url":null,"abstract":"<div><div>This study seeks to push the limits of LC<sup>3</sup>-50 binders by utilising low-grade kaolinite clays and C-S-H gel nucleation seeding. Four commercially-available kaolinite clays (i.e. kaolinite contents ~20 wt%) have been studied by X-ray fluorescence, X-ray powder diffraction and thermal analysis. The clays were thermally activated and milled to D<sub>v,50</sub> = 11 ± 2 μm. The activated clays showed low pozzolanic performances, as determined by ASTM C1897-20 standard. The heat flows ranged 200–230 J/g calcined clay and the bound waters 4.3–5.7 %. The LC<sup>3</sup>-50 pastes were characterised by calorimetry, X-ray powder diffraction and the Rietveld method, thermal analysis, and porosimetry to evaluate pozzolanic reactivity and the seeding effect.</div><div>LC<sup>3</sup> mortars, w/b = 0.40, have relatively low compressive strengths, especially at one day, but these values were increased by 64 % on average at one day by seeding. At 1 day, three LC<sup>3</sup> mortars showed 11 MPa which increased to 18–20 MPa by seeding. A fourth mortar showed a much higher compressive strength, 16 MPa, that increased to 23 MPa, by seeding. A tested concrete, w/b = 0.50, also showed a high increase of 37 % at 1 day. The improvements at 28 days were maintained but quantitatively lower, 12 and 14 % for the mortars and the concrete, respectively. Insights into the pozzolanic reactions and C-S-H seeding are obtained from the quantitative study of the pastes. For instance, it is proven the pozzolanic reaction at 1 day from the portlandite consumption. Also shown is the enhanced formation of carboaluminates when the strength enhancing admixture is added.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108036"},"PeriodicalIF":13.1,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145118032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The influence of sodium hydroxide and citric acid on the hydration of a calcium aluminate cement – calcite mixture was investigated. Both the effect of the two additives individually and in combination were analysed. Sodium hydroxide accelerates the reaction, leads to dominant monocarbonate formation and higher inner strength. However, the workability is reduced. Citric acid retards the reaction, lowers the inner strength but has a positive influence on the workability. Furthermore, the main reaction with citric acid only begins when the concentration of citric acid in the pore solution drops below 125–115 mmol/l. In combination of both additives, NaOH improves the inner strength, whereas higher doses of citric acid improve the workability, whereby the dominant hydrate phase composition changes from monocarbonate to CAH10. In addition, it was observed that a higher degree of hydration within the first 24 h is associated with increased inner strength after 28 d.
{"title":"Optimization of hydration kinetics, phase development and mechanical properties of CAC in mix with calcite by addition of sodium hydroxide and citric acid","authors":"Pauline Rost , Christiane Rößler , Jürgen Neubauer , Friedlinde Goetz-Neunhoeffer","doi":"10.1016/j.cemconres.2025.108045","DOIUrl":"10.1016/j.cemconres.2025.108045","url":null,"abstract":"<div><div>The influence of sodium hydroxide and citric acid on the hydration of a calcium aluminate cement – calcite mixture was investigated. Both the effect of the two additives individually and in combination were analysed. Sodium hydroxide accelerates the reaction, leads to dominant monocarbonate formation and higher inner strength. However, the workability is reduced. Citric acid retards the reaction, lowers the inner strength but has a positive influence on the workability. Furthermore, the main reaction with citric acid only begins when the concentration of citric acid in the pore solution drops below 125–115 mmol/l. In combination of both additives, NaOH improves the inner strength, whereas higher doses of citric acid improve the workability, whereby the dominant hydrate phase composition changes from monocarbonate to CAH<sub>10</sub>. In addition, it was observed that a higher degree of hydration within the first 24 h is associated with increased inner strength after 28 d.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"199 ","pages":"Article 108045"},"PeriodicalIF":13.1,"publicationDate":"2025-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145089157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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