Pub Date : 2025-03-03DOI: 10.1016/j.cemconres.2025.107854
Michael Wenzel, Fabien Georget, Thomas Matschei
This paper reviews the efforts taken towards developing bauxite residue (BR) based blended cements (>30% substitution) contributing to the cement industry's net-zero targets, while utilizing the Bayer-processes by-product. We provide a comprehensive review of physical properties, element composition and mineralogy of Bayer and sintering BR. This defines the main challenges that BR based SCMs have to overcome to be utilized in sustainable blended cements. Several activation treatments and their impact on SCM characteristics and reactivity are introduced and compared to other reactive SCMs.
Furthermore, the review summarizes the impact of BR addition on the engineering performance of blended cements and includes selected durability issues. Our main goal is linking macroscopic observations to microstructural features of the binders and outlining a way towards a complete understanding of these blended cements. We outline specific knowledge gaps, in particular the effect of bauxite residues on the phase assemblage and microstructure of blended cements.
{"title":"From bauxite residue mineralogy to reactivity and properties of blended cements","authors":"Michael Wenzel, Fabien Georget, Thomas Matschei","doi":"10.1016/j.cemconres.2025.107854","DOIUrl":"10.1016/j.cemconres.2025.107854","url":null,"abstract":"<div><div>This paper reviews the efforts taken towards developing bauxite residue (BR) based blended cements (>30% substitution) contributing to the cement industry's net-zero targets, while utilizing the Bayer-processes by-product. We provide a comprehensive review of physical properties, element composition and mineralogy of Bayer and sintering BR. This defines the main challenges that BR based SCMs have to overcome to be utilized in sustainable blended cements. Several activation treatments and their impact on SCM characteristics and reactivity are introduced and compared to other reactive SCMs.</div><div>Furthermore, the review summarizes the impact of BR addition on the engineering performance of blended cements and includes selected durability issues. Our main goal is linking macroscopic observations to microstructural features of the binders and outlining a way towards a complete understanding of these blended cements. We outline specific knowledge gaps, in particular the effect of bauxite residues on the phase assemblage and microstructure of blended cements.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"192 ","pages":"Article 107854"},"PeriodicalIF":10.9,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143532580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-01DOI: 10.1016/j.cemconres.2025.107856
Onur Ozturk, Sriramya Duddukuri Nair
Cracks reduce the strength and service life of concrete structures. Although high-performance crack filling materials are available in market, achieving deep infiltration is often difficult. In this work, we propose the utilization of a magnetic approach for enhanced infiltration and examine the mechanisms governing its effectiveness. Our experiments demonstrate that employing magnetic fields in the milliTesla range can significantly enhance the filling ability of solutions containing <1% by volume of magnetic particles. To facilitate flow observations and gain a deeper understanding of the fundamental mechanisms, we used transparent box samples and guar gum solutions in this study. In line with the objectives of this study, we discuss potential mechanisms relevant to real concrete cracks and crack filling materials. Finally, we provide suggestions for field implementation of the proposed technology, considering the typical characteristics of concrete cracks and structural elements.
{"title":"Mechanisms governing in-depth infiltration of crack filling solutions in concrete using a magnetic approach","authors":"Onur Ozturk, Sriramya Duddukuri Nair","doi":"10.1016/j.cemconres.2025.107856","DOIUrl":"10.1016/j.cemconres.2025.107856","url":null,"abstract":"<div><div>Cracks reduce the strength and service life of concrete structures. Although high-performance crack filling materials are available in market, achieving deep infiltration is often difficult. In this work, we propose the utilization of a magnetic approach for enhanced infiltration and examine the mechanisms governing its effectiveness. Our experiments demonstrate that employing magnetic fields in the milliTesla range can significantly enhance the filling ability of solutions containing <1% by volume of magnetic particles. To facilitate flow observations and gain a deeper understanding of the fundamental mechanisms, we used transparent box samples and guar gum solutions in this study. In line with the objectives of this study, we discuss potential mechanisms relevant to real concrete cracks and crack filling materials. Finally, we provide suggestions for field implementation of the proposed technology, considering the typical characteristics of concrete cracks and structural elements.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"192 ","pages":"Article 107856"},"PeriodicalIF":10.9,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143526500","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 : 2025-03-01DOI: 10.1016/j.cemconres.2025.107841
Songyue Chai , Jianyu Song , Muhan Wang , Yue Zhang , Bo-Tao Huang , Bing Yin , Pan Wang , Dongshuai Hou
Salt-frost damage is a crucial issue affecting the durability of concrete structures, however, the freezing behavior and micro-mechanisms of ionic solutions within cementitious material gel pores remain unclear, which is not conducive to optimizing cold-resistant concrete design from the bottom up. In this study, the models of saturated calcium silicate hydrate (C-S-H) gel pores containing NaCl, Na2SO4, and aqueous solution, respectively, were constructed by molecular dynamics (MD) simulation. We investigated the freezing behavior of ionic solutions within the gel pores at 230 K. The freezing process of models exhibited a distinct periodic pattern. Na+ and Cl− delayed the freezing of pore water, while accumulated near the freezing front, significantly hindering freezing progression. The freezing resulted in two types of nano brine pockets in the NaCl model. This work provides new molecular insights into salt freezing in cementitious materials and informs the design of cold-resistant concrete at the molecular scale.
{"title":"Freezing behavior of ionic solutions within calcium silicate hydrate gel pores","authors":"Songyue Chai , Jianyu Song , Muhan Wang , Yue Zhang , Bo-Tao Huang , Bing Yin , Pan Wang , Dongshuai Hou","doi":"10.1016/j.cemconres.2025.107841","DOIUrl":"10.1016/j.cemconres.2025.107841","url":null,"abstract":"<div><div>Salt-frost damage is a crucial issue affecting the durability of concrete structures, however, the freezing behavior and micro-mechanisms of ionic solutions within cementitious material gel pores remain unclear, which is not conducive to optimizing cold-resistant concrete design from the bottom up. In this study, the models of saturated calcium silicate hydrate (C-S-H) gel pores containing NaCl, Na<sub>2</sub>SO<sub>4</sub>, and aqueous solution, respectively, were constructed by molecular dynamics (MD) simulation. We investigated the freezing behavior of ionic solutions within the gel pores at 230 K. The freezing process of models exhibited a distinct periodic pattern. Na<sup>+</sup> and Cl<sup>−</sup> delayed the freezing of pore water, while <span><math><msubsup><mi>SO</mi><mn>4</mn><mrow><mn>2</mn><mo>−</mo></mrow></msubsup></math></span> accumulated near the freezing front, significantly hindering freezing progression. The freezing resulted in two types of nano brine pockets in the NaCl model. This work provides new molecular insights into salt freezing in cementitious materials and informs the design of cold-resistant concrete at the molecular scale.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"192 ","pages":"Article 107841"},"PeriodicalIF":10.9,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143518892","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 : 2025-02-27DOI: 10.1016/j.cemconres.2025.107851
Paulina Guzmán García Lascurain , Carlos Rodriguez-Navarro , Lucia Toniolo , Sara Goidanich
Air lime-based mortars and plasters are preferred for the restoration of historic masonry due to their high compatibility, and for modern constructions given their lower environmental impact. However, their slow setting (via carbonation) and their limited strength hinder their widespread use. This study explores the influence of nano- and micro-cellulose additives dosed during lime slaking on the formation and textural/structural features of calcium hydroxide. The alkaline degradation of the additives, along with their interaction and adsorption/occlusion during heterogeneous and homogeneous precipitation of calcium hydroxide was studied. Both additives foster the non-classical crystallization of portlandite via amorphous phases, resulting in plate-like crystals in the case of nano-cellulose, whereas more reactive micro-cellulose promotes the stabilization of a dense liquid precursor, and upon its dehydration, the stabilization of amorphous calcium hydroxide. Ultimately both additives lead to the formation of potentially more reactive nano and mesostructured Ca(OH)2 particles.
{"title":"Effects of nano- and micro-cellulose on Ca(OH)2 formation: Implications for lime-based binders","authors":"Paulina Guzmán García Lascurain , Carlos Rodriguez-Navarro , Lucia Toniolo , Sara Goidanich","doi":"10.1016/j.cemconres.2025.107851","DOIUrl":"10.1016/j.cemconres.2025.107851","url":null,"abstract":"<div><div>Air lime-based mortars and plasters are preferred for the restoration of historic masonry due to their high compatibility, and for modern constructions given their lower environmental impact. However, their slow setting (via carbonation) and their limited strength hinder their widespread use. This study explores the influence of nano- and micro-cellulose additives dosed during lime slaking on the formation and textural/structural features of calcium hydroxide. The alkaline degradation of the additives, along with their interaction and adsorption/occlusion during heterogeneous and homogeneous precipitation of calcium hydroxide was studied. Both additives foster the non-classical crystallization of portlandite via amorphous phases, resulting in plate-like crystals in the case of nano-cellulose, whereas more reactive micro-cellulose promotes the stabilization of a dense liquid precursor, and upon its dehydration, the stabilization of amorphous calcium hydroxide. Ultimately both additives lead to the formation of potentially more reactive nano and mesostructured Ca(OH)<sub>2</sub> particles.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"192 ","pages":"Article 107851"},"PeriodicalIF":10.9,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143509904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-26DOI: 10.1016/j.cemconres.2025.107842
Gen Li , Yong Tao , Yining Gao , Peiliang Shen , Xiong Qian , Binbin Yin , Roland J.-M. Pellenq , Chi Sun Poon
While carbon sequestration with dicalcium silicate (C2S) offers a promising approach, the underlying mechanisms governing the contrasting carbonation efficiencies of different polymorphs remain poorly understood. Taking three C2S polymorphs as a paradigm, this study uses Grand Canonical Monte Carlo simulations to investigate CO2 physisorption within αL-, β-, and γ-C2S mesopores under dry, unhydrated, and hydrated conditions. Our findings show that in dry scenarios, solid-gas interactions dominate, with γ-C2S exhibiting the lowest CO2 intake due to its high surface charge density. A nanometer-thick water film in humid environments significantly enhances CO2 adsorption due to the liquid-gas interactions, which are mediated by surface charges via the polarization of water molecules. Surface hydroxylation increases surface charge density in hydrated αL- and β-C2S and reduces their CO2 adsorption capacity. The slower hydration of γ-C2S leads to a comparatively higher CO2 adsorption capacity, suggesting a larger CO2 reservoir within its mesopores. This enhanced CO2 availability potentially explains the experimentally observed superior carbonation efficiency of γ-C2S and demonstrates a vivid example of the competing effect of hydration and carbonation for cement minerals. These molecular-level insights provide a profound understanding of the complex interplay between surface properties, hydration, and CO2 physisorption in the carbonation of C2S and other carbonatable materials.
{"title":"Water's grip on CO2 intake in mesopores of dicalcium silicate","authors":"Gen Li , Yong Tao , Yining Gao , Peiliang Shen , Xiong Qian , Binbin Yin , Roland J.-M. Pellenq , Chi Sun Poon","doi":"10.1016/j.cemconres.2025.107842","DOIUrl":"10.1016/j.cemconres.2025.107842","url":null,"abstract":"<div><div>While carbon sequestration with dicalcium silicate (C<sub>2</sub>S) offers a promising approach, the underlying mechanisms governing the contrasting carbonation efficiencies of different polymorphs remain poorly understood. Taking three C<sub>2</sub>S polymorphs as a paradigm, this study uses Grand Canonical Monte Carlo simulations to investigate CO<sub>2</sub> physisorption within α<sub>L</sub>-, β-, and γ-C<sub>2</sub>S mesopores under dry, unhydrated, and hydrated conditions. Our findings show that in dry scenarios, solid-gas interactions dominate, with γ-C<sub>2</sub>S exhibiting the lowest CO<sub>2</sub> intake due to its high surface charge density. A nanometer-thick water film in humid environments significantly enhances CO<sub>2</sub> adsorption due to the liquid-gas interactions, which are mediated by surface charges via the polarization of water molecules. Surface hydroxylation increases surface charge density in hydrated α<sub>L</sub>- and β-C<sub>2</sub>S and reduces their CO<sub>2</sub> adsorption capacity. The slower hydration of γ-C<sub>2</sub>S leads to a comparatively higher CO<sub>2</sub> adsorption capacity, suggesting a larger CO<sub>2</sub> reservoir within its mesopores. This enhanced CO<sub>2</sub> availability potentially explains the experimentally observed superior carbonation efficiency of γ-C<sub>2</sub>S and demonstrates a vivid example of the competing effect of hydration and carbonation for cement minerals. These molecular-level insights provide a profound understanding of the complex interplay between surface properties, hydration, and CO<sub>2</sub> physisorption in the carbonation of C<sub>2</sub>S and other carbonatable materials.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"192 ","pages":"Article 107842"},"PeriodicalIF":10.9,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488500","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 : 2025-02-24DOI: 10.1016/j.cemconres.2025.107849
Xingyu Gan , Haiming Zhang , Zeyu Lu , Kai Ma , Xiaowen Chen , Lingchao Lu , Laibo Li
Incorporating aluminum dihydrogen phosphate into magnesium phosphate cement (MPC), including magnesium ammonium phosphate cement (AMAPC) and magnesium potassium phosphate cement (AMKPC), significantly enhances both compressive strength and water resistance. The results show that AMAPC-3 exhibited a remarkable increase in compressive strength, maintaining a compressive strength retention ratio of 0.83 after 60 days. The addition of aluminum dihydrogen phosphate introduced extra phosphate ions that facilitated the hydration of unreacted MgO, resulting in an increased formation of hydration products such as struvite and k-struvite. Furthermore, it participated in independent hydration reactions, generating new phase Al(OH)3 gel and Al(PO4)·2H2O gel, which contributed to a denser microstructure. Microstructural analysis confirmed a refined pore structure and reduced porosity in the modified cements. These findings position aluminum dihydrogen phosphate as an effective modifier for enhancing the water resistance and mechanical properties of MPCs.
{"title":"Effect of aluminum dihydrogen phosphate in enhancing mechanical properties and water resistance of magnesium phosphate cement","authors":"Xingyu Gan , Haiming Zhang , Zeyu Lu , Kai Ma , Xiaowen Chen , Lingchao Lu , Laibo Li","doi":"10.1016/j.cemconres.2025.107849","DOIUrl":"10.1016/j.cemconres.2025.107849","url":null,"abstract":"<div><div>Incorporating aluminum dihydrogen phosphate into magnesium phosphate cement (MPC), including magnesium ammonium phosphate cement (AMAPC) and magnesium potassium phosphate cement (AMKPC), significantly enhances both compressive strength and water resistance. The results show that AMAPC-3 exhibited a remarkable increase in compressive strength, maintaining a compressive strength retention ratio of 0.83 after 60 days. The addition of aluminum dihydrogen phosphate introduced extra phosphate ions that facilitated the hydration of unreacted MgO, resulting in an increased formation of hydration products such as struvite and k-struvite. Furthermore, it participated in independent hydration reactions, generating new phase Al(OH)<sub>3</sub> gel and Al(PO<sub>4</sub>)·2H<sub>2</sub>O gel, which contributed to a denser microstructure. Microstructural analysis confirmed a refined pore structure and reduced porosity in the modified cements. These findings position aluminum dihydrogen phosphate as an effective modifier for enhancing the water resistance and mechanical properties of MPCs.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"192 ","pages":"Article 107849"},"PeriodicalIF":10.9,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479782","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 : 2025-02-24DOI: 10.1016/j.cemconres.2025.107840
Chengyao Liang , Qi Zheng , Roya Maboudian , Paulo J.M. Monteiro , Shaofan Li
Calcium silicate hydrate (C-S-H) is a crucial cement hydration product for the strength and durability of concrete. While previous studies have extensively investigated the structural and compositional characteristics of C-S-H, they mostly focused on average properties within ensemble systems. In this work, we use electron energy loss spectroscopy (EELS), electron nano-tomography, and other spectroscopies to study the local structure of C-S-H at an unprecedented spatial resolution of 5 nm. The chemical environments of silicon (Si) and calcium (Ca) elements, thickness, and dielectric properties are scrutinized. Statistical analysis of over 10,000 data points reveals significant heterogeneity in the silicate chemical environment, including different polymerization degrees and tetrahedral distortions. In contrast, the local Ca environment exhibits more homogeneity with a coordination number ranging from 7 to 9, indicating a weak octahedral-like symmetry for C-S-H. Additionally, our findings show that the local thickness of C-S-H predominantly hovers around ∼15 nm consisting of 13–14 layers, validated through electron tomography. This work provides insights into the local structural features of C-S-H from the single colloid perspective and thus facilitates the future development of more realistic C-S-H models.
{"title":"Electron energy loss spectroscopy of nanoscale local structures in calcium silicate hydrate","authors":"Chengyao Liang , Qi Zheng , Roya Maboudian , Paulo J.M. Monteiro , Shaofan Li","doi":"10.1016/j.cemconres.2025.107840","DOIUrl":"10.1016/j.cemconres.2025.107840","url":null,"abstract":"<div><div>Calcium silicate hydrate (C-S-H) is a crucial cement hydration product for the strength and durability of concrete. While previous studies have extensively investigated the structural and compositional characteristics of C-S-H, they mostly focused on average properties within ensemble systems. In this work, we use electron energy loss spectroscopy (EELS), electron nano-tomography, and other spectroscopies to study the local structure of C-S-H at an unprecedented spatial resolution of 5 nm. The chemical environments of silicon (Si) and calcium (Ca) elements, thickness, and dielectric properties are scrutinized. Statistical analysis of over 10,000 data points reveals significant heterogeneity in the silicate chemical environment, including different polymerization degrees and tetrahedral distortions. In contrast, the local Ca environment exhibits more homogeneity with a coordination number ranging from 7 to 9, indicating a weak octahedral-like symmetry for C-S-H. Additionally, our findings show that the local thickness of C-S-H predominantly hovers around ∼15 nm consisting of 13–14 layers, validated through electron tomography. This work provides insights into the local structural features of C-S-H from the single colloid perspective and thus facilitates the future development of more realistic C-S-H models.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"192 ","pages":"Article 107840"},"PeriodicalIF":10.9,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474758","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 : 2025-02-20DOI: 10.1016/j.cemconres.2025.107817
John Temitope Kolawole , Richard Buswell , Sultan Mahmood , Muhammad Nura Isa , Sergio Cavalaro , Simon Austin , Dirk Engelberg , James Dobrzanski , Jerry Xu , Philip J. Withers
One of the most significant challenges facing extrusion-based 3D concrete printing (3DCP) is the anisotropy present in the printed material: under load, the observed performance is typically lower than a cast equivalent and significantly so in certain directions. In addition, the performance is also more variable than cast material. These observations are, in part, due to surface moisture evaporation and air entrapment. Here, we investigate the hypothesis that the printed concrete comprises of agglomerated filament core and skin having distinct properties as a necessary consequence of the printing process. Through novel X-ray computed tomography measurements, we show that printed concrete comprises the core and Filament Interfacial Zone Network (FIZN) and that, in contrast to the cores, the FIZN is found to be free from pores except at boundaries where there is incomplete bonding. Through morphological, chemical and mechanical analysis, the FIZN is also found to contain 20% less sand and 60% more anhydrous cement than the filament cores, while the FIZ material was inferred to have 11% higher compressive strength, 28% lower flexural strength and 22% lower elastic modulus than the core. The findings from this work suggest that anisotropy will always exist and that care should be devoted to the material rheology, printing system and the filaments arrangement in order to produce consistent and predictable hardened material properties.
{"title":"On the origins of anisotropy of extrusion-based 3D printed concrete: The roles of filament skin and agglomeration","authors":"John Temitope Kolawole , Richard Buswell , Sultan Mahmood , Muhammad Nura Isa , Sergio Cavalaro , Simon Austin , Dirk Engelberg , James Dobrzanski , Jerry Xu , Philip J. Withers","doi":"10.1016/j.cemconres.2025.107817","DOIUrl":"10.1016/j.cemconres.2025.107817","url":null,"abstract":"<div><div>One of the most significant challenges facing extrusion-based 3D concrete printing (3DCP) is the anisotropy present in the printed material: under load, the observed performance is typically lower than a cast equivalent and significantly so in certain directions. In addition, the performance is also more variable than cast material. These observations are, in part, due to surface moisture evaporation and air entrapment. Here, we investigate the hypothesis that the printed concrete comprises of agglomerated filament core and skin having distinct properties as a necessary consequence of the printing process. Through novel X-ray computed tomography measurements, we show that printed concrete comprises the core and Filament Interfacial Zone Network (FIZN) and that, in contrast to the cores, the FIZN is found to be free from pores except at boundaries where there is incomplete bonding. Through morphological, chemical and mechanical analysis, the FIZN is also found to contain 20% less sand and 60% more anhydrous cement than the filament cores, while the FIZ material was inferred to have 11% higher compressive strength, 28% lower flexural strength and 22% lower elastic modulus than the core. The findings from this work suggest that anisotropy will always exist and that care should be devoted to the material rheology, printing system and the filaments arrangement in order to produce consistent and predictable hardened material properties.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"192 ","pages":"Article 107817"},"PeriodicalIF":10.9,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-18DOI: 10.1016/j.cemconres.2025.107837
Xuerun Li , Karen L. Scrivener
X-ray powder diffraction (XRD) was used to characterize and quantify nano-crystalline C-S-H in hydrated tricalcium silicate (C3S), Portland cement, and siliceous fly ash blended cement using Rietveld analysis with partial or no known crystal structure (PONKCS) coupled with thermalgravimetric analysis (TGA). Calibration of the C-S-H profile was carried out by minimizing bound water content detected by TGA and XRD using least square minimization. Validation of the results was achieved by independent methods such as TGA and mass balance calculation. The PONKCS analysis provided acceptable accuracy of the C-S-H content. H2O content in C-S-H was derived based on the C-S-H content and bound water. Comparison of the extracted profile showed that the C-S-H crystallinity increased with an increase in Ca/Si atomic ratio. The full phase assemblage of the hydrated samples was obtained. Challenges in applying PONKCS method in C-S-H determination were discussed.
{"title":"Quantification of nano-crystalline C-S-H in hydrated tricalcium silicate, Portland cement and fly ash cement using PONKCS method","authors":"Xuerun Li , Karen L. Scrivener","doi":"10.1016/j.cemconres.2025.107837","DOIUrl":"10.1016/j.cemconres.2025.107837","url":null,"abstract":"<div><div>X-ray powder diffraction (XRD) was used to characterize and quantify nano-crystalline C-S-H in hydrated tricalcium silicate (C<sub>3</sub>S), Portland cement, and siliceous fly ash blended cement using Rietveld analysis with partial or no known crystal structure (PONKCS) coupled with thermalgravimetric analysis (TGA). Calibration of the C-S-H profile was carried out by minimizing bound water content detected by TGA and XRD using least square minimization. Validation of the results was achieved by independent methods such as TGA and mass balance calculation. The PONKCS analysis provided acceptable accuracy of the C-S-H content. H<sub>2</sub>O content in C-S-H was derived based on the C-S-H content and bound water. Comparison of the extracted profile showed that the C-S-H crystallinity increased with an increase in Ca/Si atomic ratio. The full phase assemblage of the hydrated samples was obtained. Challenges in applying PONKCS method in C-S-H determination were discussed.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107837"},"PeriodicalIF":10.9,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-16DOI: 10.1016/j.cemconres.2025.107809
Rodrigo Díaz Flores, Christian Hellmich, Bernhard Pichler
With the aim to identify the mechanisms governing nonlinear basic creep of concrete under uniaxial compression, a micromechanics model is presented. Extending the affinity concept for nonlinear creep, it describes that every microcrack incrementally increases the damage of concrete, leading to a step-wise increase of its compliance. Experimental data are taken from the literature. Strain and acoustic emission measurements from a multi-stage creep test are used to develop the model. This includes identification of microcrack evolution laws for both short-term load application and sustained loading. Strain measurements from four single-stage creep tests are used for model validation. It is concluded that nonlinear creep of concrete is governed by two mechanisms: (i) stress-induced stick–slip transition of viscous interfaces at the nanostructure of cement paste, which is phenomenologically accounted for by the affinity concept, and (ii) microcracking-induced damage, which is of major importance once the stress exceeds some 70% of the strength.
{"title":"Nonlinear creep of concrete: Stress-activated stick–slip transition of viscous interfaces and microcracking-induced damage","authors":"Rodrigo Díaz Flores, Christian Hellmich, Bernhard Pichler","doi":"10.1016/j.cemconres.2025.107809","DOIUrl":"10.1016/j.cemconres.2025.107809","url":null,"abstract":"<div><div>With the aim to identify the mechanisms governing nonlinear basic creep of concrete under uniaxial compression, a micromechanics model is presented. Extending the affinity concept for nonlinear creep, it describes that every microcrack incrementally increases the damage of concrete, leading to a step-wise increase of its compliance. Experimental data are taken from the literature. Strain and acoustic emission measurements from a multi-stage creep test are used to develop the model. This includes identification of microcrack evolution laws for both short-term load application and sustained loading. Strain measurements from four single-stage creep tests are used for model validation. It is concluded that nonlinear creep of concrete is governed by two mechanisms: (i) stress-induced stick–slip transition of viscous interfaces at the nanostructure of cement paste, which is phenomenologically accounted for by the affinity concept, and (ii) microcracking-induced damage, which is of major importance once the stress exceeds some 70% of the strength.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107809"},"PeriodicalIF":10.9,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号