Pub Date : 2025-03-11DOI: 10.1016/j.cemconres.2025.107857
Takeru Kanazawa , John E. Bolander
Understanding of the load-rate dependence of fiber pull-out from concrete has been hindered by the large scatter of test data. Relatively little attention has been given to the statistical nature of single-fiber pull-out under different loading rates. The present study is based on a probabilistic interpretation of the pull-out phenomenon, assessing the statistical fluctuations observed in the common finding that complete pull-out occurs at greater load levels under higher loading rates. Since progressive debonding along the fiber–matrix interface affects the pull-out behavior, interfacial crack growth is modeled using a fracture mechanics approach. Based on a theoretical justification, the transition probability to debonding is devised and implemented within a Markov chain model. The Markov model accounts for debonding propagation with each stress increment until complete pull-out. The results demonstrate that the probability distributions of stress at complete pull-out differ from a normal distribution. The coefficient of variation is also independent of the loading rates. These findings show reasonable agreement with statistical variations observed from test data.
{"title":"Rate effect on the pull-out load of individual fibers in concrete: A probabilistic modeling approach","authors":"Takeru Kanazawa , John E. Bolander","doi":"10.1016/j.cemconres.2025.107857","DOIUrl":"10.1016/j.cemconres.2025.107857","url":null,"abstract":"<div><div>Understanding of the load-rate dependence of fiber pull-out from concrete has been hindered by the large scatter of test data. Relatively little attention has been given to the statistical nature of single-fiber pull-out under different loading rates. The present study is based on a probabilistic interpretation of the pull-out phenomenon, assessing the statistical fluctuations observed in the common finding that complete pull-out occurs at greater load levels under higher loading rates. Since progressive debonding along the fiber–matrix interface affects the pull-out behavior, interfacial crack growth is modeled using a fracture mechanics approach. Based on a theoretical justification, the transition probability to debonding is devised and implemented within a Markov chain model. The Markov model accounts for debonding propagation with each stress increment until complete pull-out. The results demonstrate that the probability distributions of stress at complete pull-out differ from a normal distribution. The coefficient of variation is also independent of the loading rates. These findings show reasonable agreement with statistical variations observed from test data.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107857"},"PeriodicalIF":10.9,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143590118","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 : 2025-03-10DOI: 10.1016/j.cemconres.2025.107855
R. Besselink , A. Poulain , M. la Bella , A.-L. Auzende , S. Goberna-Ferron , M.P. Asta , V. Magnin , S. Bureau , L. Fernández-Carrasco , A.E.S. Van Driessche , A. Fernandez-Martinez
The heterogeneous nature of the cement clinker, its complex coupled dissolution/re-precipitation process and the complex defect chemistry of the hydrates formed during cement hydration, make that the nucleation and growth mechanisms of cement hydrates are not fully understood. Recent studies have suggested the existence of a disordered precursor prior to the crystallization of C-S-H. Here, a combination of X-ray scattering and electron microscopy experiments are used to study the structure and crystallization kinetics of this amorphous intermediate. Our results suggest that proto-C-S-H is predominantly composed of 6-fold oxygen-to-calcium coordinated CaOx polyhedra, in contrast to the 7-fold coordinated polyhedra in C-S-H with a tobermorite-like structure. The addition of gluconate, a widely used additive, resulted in an increased kinetic persistence of proto-C-S-H. Overall, our study provides new insights into the formation and structure of proto-C-S-H, and suggests that it plays an important role in the crystallization mechanism of C-S-H.
{"title":"High energy X-ray scattering reveals the short-range order of proto-C-S-H: Implications for the nucleation of cement hydrates","authors":"R. Besselink , A. Poulain , M. la Bella , A.-L. Auzende , S. Goberna-Ferron , M.P. Asta , V. Magnin , S. Bureau , L. Fernández-Carrasco , A.E.S. Van Driessche , A. Fernandez-Martinez","doi":"10.1016/j.cemconres.2025.107855","DOIUrl":"10.1016/j.cemconres.2025.107855","url":null,"abstract":"<div><div>The heterogeneous nature of the cement clinker, its complex coupled dissolution/re-precipitation process and the complex defect chemistry of the hydrates formed during cement hydration, make that the nucleation and growth mechanisms of cement hydrates are not fully understood. Recent studies have suggested the existence of a disordered precursor prior to the crystallization of C-S-H. Here, a combination of X-ray scattering and electron microscopy experiments are used to study the structure and crystallization kinetics of this amorphous intermediate. Our results suggest that proto-C-S-H is predominantly composed of 6-fold oxygen-to-calcium coordinated CaO<sub>x</sub> polyhedra, in contrast to the 7-fold coordinated polyhedra in C-S-H with a tobermorite-like structure. The addition of gluconate, a widely used additive, resulted in an increased kinetic persistence of proto-C-S-H. Overall, our study provides new insights into the formation and structure of proto-C-S-H, and suggests that it plays an important role in the crystallization mechanism of C-S-H.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107855"},"PeriodicalIF":10.9,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143590050","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 : 2025-03-09DOI: 10.1016/j.cemconres.2025.107867
Yikai Liu , Maria Chiara Dalconi , Maurizio Pietro Bellotto , Luca Valentini , Simone Molinari , Xinyi Yuan , Daolin Wang , Wei Hu , Qiusong Chen , Alejandro Fernandez-Martinez , Gilberto Artioli
Using industrial by-products as substitutes for Ordinary Portland Cement (OPC) is a promising strategy to reduce its environmental impact. However, heavy metals like Pb strongly interfere with initial kinetics. The dynamic physicochemical environment makes it challenging to identify the key factors. Here, we employed in-situ XRD as a time-dependent method, alongside conventional characterization techniques and geochemical modeling, to investigate the Pb-induced retardation in CEMI 42.5R and 52.5R. The results show that Pb-hydroxides and Pb-O-Si clusters are expected to be the primary mechanisms for this inhibition. Among clinker phases, C3A dissolution is less affected and serves as the primary source of alkalinity in early hydration, promoting hydration products precipitation and gypsum dissolution. Geochemical modeling suggests that Pb species concentration in the solution regulates the precipitation of hydration products, especially portlandite. The comparison of hydration kinetics of 2 types of OPC highlights optimizing particle size as a solution to mitigate retardation impact.
{"title":"Pb-induced retardation of early hydration of Portland cement: Insights from in-situ XRD and implications for substitution with industrial by-products","authors":"Yikai Liu , Maria Chiara Dalconi , Maurizio Pietro Bellotto , Luca Valentini , Simone Molinari , Xinyi Yuan , Daolin Wang , Wei Hu , Qiusong Chen , Alejandro Fernandez-Martinez , Gilberto Artioli","doi":"10.1016/j.cemconres.2025.107867","DOIUrl":"10.1016/j.cemconres.2025.107867","url":null,"abstract":"<div><div>Using industrial by-products as substitutes for Ordinary Portland Cement (OPC) is a promising strategy to reduce its environmental impact. However, heavy metals like Pb strongly interfere with initial kinetics. The dynamic physicochemical environment makes it challenging to identify the key factors. Here, we employed <em>in-situ</em> XRD as a time-dependent method, alongside conventional characterization techniques and geochemical modeling, to investigate the Pb-induced retardation in CEMI 42.5R and 52.5R. The results show that Pb-hydroxides and Pb-O-Si clusters are expected to be the primary mechanisms for this inhibition. Among clinker phases, C<sub>3</sub>A dissolution is less affected and serves as the primary source of alkalinity in early hydration, promoting hydration products precipitation and gypsum dissolution. Geochemical modeling suggests that Pb species concentration in the solution regulates the precipitation of hydration products, especially portlandite. The comparison of hydration kinetics of 2 types of OPC highlights optimizing particle size as a solution to mitigate retardation impact.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107867"},"PeriodicalIF":10.9,"publicationDate":"2025-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143576380","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 : 2025-03-05DOI: 10.1016/j.cemconres.2025.107859
Jialiang Wang, Min Wu
Effective, low-cost and simplistic self-healing strategies for cement-based systems are attractive. This work proposed a concept where coarse clinker particles were used to replace cement and acted as the healing agent, and the effectiveness was validated by comprehensive studies. The results showed the high potential of the clinker sizes (40–60 μm, 60–90 μm, 0.5–1 mm) and replacement ratios (20–40%) under the studied conditions. For the clinker sized 40–60 μm, the 28d tensile and compressive strength recovery rates achieved 1.12 and 0.91, and the 56d crack sealing width and area reached 300–400 μm and 83.4%–94.4%, which even exceeds conventional autonomous self-healing strategies. The microscopic analyses indicated that larger clinker particles affected reaction kinetics of hydrating particles and improved spatial distribution of the hydration products. By retaining abundant unhdyrated parts and leading to more uniform distribution of the hydration products, the coarse clinker particles significantly improved self-healing properties of the cement mixes.
{"title":"A preliminary study on an effective and simplistic self-healing concept for cement using coarse clinker particles as the healing agent","authors":"Jialiang Wang, Min Wu","doi":"10.1016/j.cemconres.2025.107859","DOIUrl":"10.1016/j.cemconres.2025.107859","url":null,"abstract":"<div><div>Effective, low-cost and simplistic self-healing strategies for cement-based systems are attractive. This work proposed a concept where coarse clinker particles were used to replace cement and acted as the healing agent, and the effectiveness was validated by comprehensive studies. The results showed the high potential of the clinker sizes (40–60 μm, 60–90 μm, 0.5–1 mm) and replacement ratios (20–40%) under the studied conditions. For the clinker sized 40–60 μm, the 28d tensile and compressive strength recovery rates achieved 1.12 and 0.91, and the 56d crack sealing width and area reached 300–400 μm and 83.4%–94.4%, which even exceeds conventional autonomous self-healing strategies. The microscopic analyses indicated that larger clinker particles affected reaction kinetics of hydrating particles and improved spatial distribution of the hydration products. By retaining abundant unhdyrated parts and leading to more uniform distribution of the hydration products, the coarse clinker particles significantly improved self-healing properties of the cement mixes.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107859"},"PeriodicalIF":10.9,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143546521","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 : 2025-03-03DOI: 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}
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