Pub Date : 2024-10-13DOI: 10.1016/j.cemconres.2024.107697
Zihan Ma , Yi Jiang , Jionghuang He , Peiliang Shen , Qinglong Qin , Zhenjiang Gu , Jiangshan Li , Chi Sun Poon
This study aims to establish relationship between carbonation regimes and the early pozzolanic reactivity of carbonated recycled concrete powder (CRCP) by comparing the composition, structure and surface properties of the carbonation products. The surface of dry CRCP was characterized by a silica-rich layer and contains low-polymerized silica phases along with over 18 % of unstable calcium carbonate (Cc). Wet CRCP exhibits a silica-rich surface with the highest degree of silica polymerization and stable calcite in its composition. Semi-dry CRCP has a calcium-rich surface also contains high silica polymerization and over 29 % unstable calcium carbonate, and the highest specific surface area, leading to the fastest silicon dissolution and calcium consumption during pozzolanic reactions. The early pozzolanic reaction kinetics in semi-dry and wet carbonation are limited by the dissolution of carbonation products, whereas dry carbonation does not exhibit this limitation. Understanding this connection is crucial for selecting optimal carbonation techniques to enhance waste concrete utilization.
{"title":"Revealing the connection between carbonation regimes and early pozzolanic reactivity of recycled concrete powder: Impact of composition and microstructure","authors":"Zihan Ma , Yi Jiang , Jionghuang He , Peiliang Shen , Qinglong Qin , Zhenjiang Gu , Jiangshan Li , Chi Sun Poon","doi":"10.1016/j.cemconres.2024.107697","DOIUrl":"10.1016/j.cemconres.2024.107697","url":null,"abstract":"<div><div>This study aims to establish relationship between carbonation regimes and the early pozzolanic reactivity of carbonated recycled concrete powder (CRCP) by comparing the composition, structure and surface properties of the carbonation products. The surface of dry CRCP was characterized by a silica-rich layer and contains low-polymerized silica phases along with over 18 % of unstable calcium carbonate (Cc). Wet CRCP exhibits a silica-rich surface with the highest degree of silica polymerization and stable calcite in its composition. Semi-dry CRCP has a calcium-rich surface also contains high silica polymerization and over 29 % unstable calcium carbonate, and the highest specific surface area, leading to the fastest silicon dissolution and calcium consumption during pozzolanic reactions. The early pozzolanic reaction kinetics in semi-dry and wet carbonation are limited by the dissolution of carbonation products, whereas dry carbonation does not exhibit this limitation. Understanding this connection is crucial for selecting optimal carbonation techniques to enhance waste concrete utilization.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107697"},"PeriodicalIF":10.9,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142431743","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 : 2024-10-12DOI: 10.1016/j.cemconres.2024.107689
Robert J. Flatt
{"title":"The Cement and Concrete Research Le Chatelier Awards","authors":"Robert J. Flatt","doi":"10.1016/j.cemconres.2024.107689","DOIUrl":"10.1016/j.cemconres.2024.107689","url":null,"abstract":"","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107689"},"PeriodicalIF":10.9,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142415772","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 : 2024-10-10DOI: 10.1016/j.cemconres.2024.107695
Qi Liu , Pan Feng , Lijing Shao , Chen Chen , Xin Liu , Yuefeng Ma , Lizhi Zhang , Guoqing Geng
Understanding the interactions between calcium silicate hydrate (C-S-H) and heavy metals is vital for optimizing the use of solid waste in cementitious materials. This paper introduces an innovative approach to elucidate the immobilization mechanism of Cu2+, a representative heavy metal. The roles of Ca2+ and OH− in Cu2+ immobilization were comprehensively investigated through being treated by C-S-H samples with varying interlayer Ca2+ contents via meticulous immersion in ammonium chloride (NH4Cl). Our results indicate that Cu2+ immobilization primarily occurs via complete substitution of interlayer Ca2+ and partial substitution of intralayer Ca2+, with contributions of 40 % and 59 %, respectively, for a Ca/Si ratio of 1.2. Minor mechanisms like OH− complexation and surface adsorption account for the remaining immobilization. The formation of Si-O-Cu complexes was confirmed by X-ray photoelectron (XPS) and Extended X-ray Absorption Fine Structure (EXAFS) analysis. This study provides a quantitative methodology that informs strategies for sustainable cementitious waste utilization.
{"title":"Quantifying the immobilization mechanisms of heavy metals by Calcium Silicate Hydrate (C-S-H): The case of Cu2+","authors":"Qi Liu , Pan Feng , Lijing Shao , Chen Chen , Xin Liu , Yuefeng Ma , Lizhi Zhang , Guoqing Geng","doi":"10.1016/j.cemconres.2024.107695","DOIUrl":"10.1016/j.cemconres.2024.107695","url":null,"abstract":"<div><div>Understanding the interactions between calcium silicate hydrate (C-S-H) and heavy metals is vital for optimizing the use of solid waste in cementitious materials. This paper introduces an innovative approach to elucidate the immobilization mechanism of Cu<sup>2+</sup>, a representative heavy metal. The roles of Ca<sup>2+</sup> and OH<sup>−</sup> in Cu<sup>2+</sup> immobilization were comprehensively investigated through being treated by C-S-H samples with varying interlayer Ca<sup>2+</sup> contents via meticulous immersion in ammonium chloride (NH<sub>4</sub>Cl). Our results indicate that Cu<sup>2+</sup> immobilization primarily occurs via complete substitution of interlayer Ca<sup>2+</sup> and partial substitution of intralayer Ca<sup>2+</sup>, with contributions of 40 % and 59 %, respectively, for a Ca/Si ratio of 1.2. Minor mechanisms like OH<sup>−</sup> complexation and surface adsorption account for the remaining immobilization. The formation of Si-O-Cu complexes was confirmed by X-ray photoelectron (XPS) and Extended X-ray Absorption Fine Structure (EXAFS) analysis. This study provides a quantitative methodology that informs strategies for sustainable cementitious waste utilization.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107695"},"PeriodicalIF":10.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142397812","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 cementitious properties of natural Mg-rich olivine when reacted with a phosphoric acid solution are investigated, as a function of acid concentration and liquid/solid mass ratio. The obtained cements are composed of residual olivine crystals and amorphous silica nanoparticles dispersed in a dense and compact newberyite (MgHPO4∙3H2O) matrix. The latter was mostly formed by packed micrometric tabular crystals, although evidence of the presence of a fraction of amorphous MgHPO4 was also found. Water content in the raw mix was observed to play a pivotal role on the reaction pathway, either promoting porosity or hindering the crystallization of the products. Up to 57 % of olivine reactivity, whose dissolution was promoted by the curing temperature (60 °C) and low pH, was achieved. All in all, these results indicate that the industrial mineral olivine may serve a viable source of Mg for the production of phosphate cements.
{"title":"Setting reaction of a olivine-based Mg-phosphate cement","authors":"Davide Bernasconi , Alberto Viani , Lucie Zárybnická , Simone Bordignon , Jose R.A. Godinho , Alexey Maximenko , Cem Celikutku , Sadaf Fatima Jafri , Elisa Borfecchia , Quentin Wehrung , Roberto Gobetto , Alessandro Pavese","doi":"10.1016/j.cemconres.2024.107694","DOIUrl":"10.1016/j.cemconres.2024.107694","url":null,"abstract":"<div><div>The cementitious properties of natural Mg-rich olivine when reacted with a phosphoric acid solution are investigated, as a function of acid concentration and liquid/solid mass ratio. The obtained cements are composed of residual olivine crystals and amorphous silica nanoparticles dispersed in a dense and compact newberyite (MgHPO<sub>4</sub>∙3H<sub>2</sub>O) matrix. The latter was mostly formed by packed micrometric tabular crystals, although evidence of the presence of a fraction of amorphous MgHPO<sub>4</sub> was also found. Water content in the raw mix was observed to play a pivotal role on the reaction pathway, either promoting porosity or hindering the crystallization of the products. Up to 57 % of olivine reactivity, whose dissolution was promoted by the curing temperature (60 °C) and low pH, was achieved. All in all, these results indicate that the industrial mineral olivine may serve a viable source of Mg for the production of phosphate cements.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107694"},"PeriodicalIF":10.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142398535","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 : 2024-10-09DOI: 10.1016/j.cemconres.2024.107692
Arkabrata Sinha, Jianqiang Wei
Alkali-silica reaction (ASR), a detrimental process causing volume expansion and cracking in concrete by forming hygroscopic and swellable gel-like products, has been a long-standing challenge faced by concrete structures across the world. Understanding the underlying mechanisms of formation, moisture uptake and swelling of ASR gels requires thorough characterizations, where an appropriate drying method to remove free water and stop the reactions in the samples is essential. This study aims to elucidate the effect of freeze-drying, an emerging drying technique increasingly employed in sample preparations, on the phase, molecular structure, and moisture absorption behavior of ASR gels. Towards this end, six ASR gels with three calcium-to-silica (Ca/Si) ratios (0.1, 0.3, and 0.5) and two alkali-to-silica [(Na + K)/Si] ratios of 0.3 (low-alkali gels) and 1.0 (high-alkali gels) were studied. The results indicate that the chemical bonds and mineral components of ASR gels can be maintained during the removal of free and loosely bound water in freeze drying, while slight changes in crystallization and relative contents of alkali-silicate hydrate and calcium silicate hydrate phases were observed, in particular, for the high-alkali ASR gels. Although slight decreases in Q1, Q2, and Q3 silica polymerization sites and increases in the mean chain length and degree of polymerization were observed from the nuclear magnetic resonance (NMR) spectroscopy, the intrinsic layered silicate structure of ASR gels remains. The moisture absorption of low-alkali and high-alkali ASR gels was found to be governed by gel pores and mesopores, respectively. After freeze-drying, slight increases in moisture sorption (a 6.8 % increase in absorption and a 2.2 % decrease in desorption) and enhanced hysteresis were observed from the low-alkali gels. The high-alkali gels, however, showed a slight decrease in hygroscopicity along with a 16.6 % reduction of mesopores.
碱硅反应（ASR）是通过形成吸湿性和膨胀性凝胶状产物而导致混凝土体积膨胀和开裂的有害过程，是全球混凝土结构长期面临的挑战。要想了解 ASR 凝胶的形成、吸湿和膨胀的基本机制，就必须对其进行全面的表征，其中必须采用适当的干燥方法去除游离水并停止样品中的反应。冷冻干燥是一种新兴的干燥技术，在样品制备过程中被越来越多地采用，本研究旨在阐明冷冻干燥对 ASR 凝胶的相位、分子结构和吸湿行为的影响。为此，研究人员研究了六种 ASR 凝胶，它们的钙硅比（Ca/Si）分别为 0.1、0.3 和 0.5，碱硅比（(Na + K)/Si] 分别为 0.3（低碱凝胶）和 1.0（高碱凝胶）。结果表明，ASR 凝胶的化学键和矿物成分可在冷冻干燥过程中去除自由水和松散结合水的过程中保持不变，同时观察到结晶和碱硅酸盐水合物及硅酸钙水合物相的相对含量发生了轻微变化，尤其是在高碱 ASR 凝胶中。虽然从核磁共振（NMR）光谱中观察到 Q1、Q2 和 Q3 硅聚合位点略有减少，平均链长和聚合度有所增加，但 ASR 凝胶的固有层状硅酸盐结构依然存在。研究发现，低碱和高碱 ASR 凝胶的吸湿性分别受凝胶孔隙和中孔的支配。冷冻干燥后，低碱凝胶的吸湿性略有提高（吸湿性提高 6.8%，解吸性降低 2.2%），滞后性也有所增强。然而，高碱凝胶的吸湿性略有下降，中孔减少了 16.6%。
{"title":"Phase, structure, and hygroscopic property evolutions of alkali-silica reaction gels under freeze drying","authors":"Arkabrata Sinha, Jianqiang Wei","doi":"10.1016/j.cemconres.2024.107692","DOIUrl":"10.1016/j.cemconres.2024.107692","url":null,"abstract":"<div><div>Alkali-silica reaction (ASR), a detrimental process causing volume expansion and cracking in concrete by forming hygroscopic and swellable gel-like products, has been a long-standing challenge faced by concrete structures across the world. Understanding the underlying mechanisms of formation, moisture uptake and swelling of ASR gels requires thorough characterizations, where an appropriate drying method to remove free water and stop the reactions in the samples is essential. This study aims to elucidate the effect of freeze-drying, an emerging drying technique increasingly employed in sample preparations, on the phase, molecular structure, and moisture absorption behavior of ASR gels. Towards this end, six ASR gels with three calcium-to-silica (Ca/Si) ratios (0.1, 0.3, and 0.5) and two alkali-to-silica [(Na + K)/Si] ratios of 0.3 (low-alkali gels) and 1.0 (high-alkali gels) were studied. The results indicate that the chemical bonds and mineral components of ASR gels can be maintained during the removal of free and loosely bound water in freeze drying, while slight changes in crystallization and relative contents of alkali-silicate hydrate and calcium silicate hydrate phases were observed, in particular, for the high-alkali ASR gels. Although slight decreases in Q<sup>1</sup>, Q<sup>2,</sup> and Q<sup>3</sup> silica polymerization sites and increases in the mean chain length and degree of polymerization were observed from the nuclear magnetic resonance (NMR) spectroscopy, the intrinsic layered silicate structure of ASR gels remains. The moisture absorption of low-alkali and high-alkali ASR gels was found to be governed by gel pores and mesopores, respectively. After freeze-drying, slight increases in moisture sorption (a 6.8 % increase in absorption and a 2.2 % decrease in desorption) and enhanced hysteresis were observed from the low-alkali gels. The high-alkali gels, however, showed a slight decrease in hygroscopicity along with a 16.6 % reduction of mesopores.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107692"},"PeriodicalIF":10.9,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142385993","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}
This study investigates the influence of CO2 concentration on the carbonation process in cementitious paste, focusing on water content distribution in ordinary Portlandite cement and limestone-calcined clay cement (LC3). Employing single-sided nuclear magnetic resonance spectroscopy for water profiling, we revealed that under accelerated carbonation of 5 % and 1 %, the water content in fine pores (interlayer space and gel pores) kept constant at the carbonation front, demonstrating the plugging effect where fine pore water removal governs carbonation progress. This effect was absent under natural carbonation conditions because evaporation precedes the carbonation process. This study emphasizes that to accurately characterize cementitious materials under natural carbonation conditions, CO2 concentrations in accelerated methods should be constrained to prevent the plugging effect.
{"title":"Plugging effect of fine pore water in OPC and LC3 paste during accelerated carbonation monitored via single-sided nuclear magnetic resonance spectroscopy","authors":"Luge Cheng , Ryo Kurihara , Takahiro Ohkubo , Ryoma Kitagaki , Atsushi Teramoto , Yuya Suda , Ippei Maruyama","doi":"10.1016/j.cemconres.2024.107688","DOIUrl":"10.1016/j.cemconres.2024.107688","url":null,"abstract":"<div><div>This study investigates the influence of CO<sub>2</sub> concentration on the carbonation process in cementitious paste, focusing on water content distribution in ordinary Portlandite cement and limestone-calcined clay cement (LC<sup>3</sup>). Employing single-sided nuclear magnetic resonance spectroscopy for water profiling, we revealed that under accelerated carbonation of 5 % and 1 %, the water content in fine pores (interlayer space and gel pores) kept constant at the carbonation front, demonstrating the <em>plugging effect</em> where fine pore water removal governs carbonation progress. This effect was absent under natural carbonation conditions because evaporation precedes the carbonation process. This study emphasizes that to accurately characterize cementitious materials under natural carbonation conditions, CO<sub>2</sub> concentrations in accelerated methods should be constrained to prevent the plugging effect.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107688"},"PeriodicalIF":10.9,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142384416","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 : 2024-10-08DOI: 10.1016/j.cemconres.2024.107691
Han Gao , Igor Shikhov , Ehab Hamed , Ailar Hajimohammadi , Iman Al-Damad , Christoph Arns , Stephen J. Foster
In this paper, basic creep mechanism of ambient cured one-part alkali activated slag-fly ash (AASF) paste is examined at the microscopic level. A special mini creep rig is constructed enabling in-situ monitoring of water redistribution over time between high- and low-density (HD, LD) gel pores within the loaded paste specimens using 1H NMR relaxometry. The results suggest that the contraction of C-(N)-A-S-H particles is accompanied by the reduction of water content in HD gel for loaded AASF paste. In contrast, in the loaded OPC paste a noticeable decrease of water residing in LD rather than HD C-S-H gel was observed, implying the presence of a distinct creep mechanism. In addition to the different water environment, the more crosslinked bonding structure of AASF could partially account for its lower creep response supported by 29Si NMR measurement. The findings of this study provide evidence in understanding underlying basic creep mechanism of AASF.
{"title":"New insights on the basic creep mechanism of one-part alkali activated slag and fly ash paste","authors":"Han Gao , Igor Shikhov , Ehab Hamed , Ailar Hajimohammadi , Iman Al-Damad , Christoph Arns , Stephen J. Foster","doi":"10.1016/j.cemconres.2024.107691","DOIUrl":"10.1016/j.cemconres.2024.107691","url":null,"abstract":"<div><div>In this paper, basic creep mechanism of ambient cured one-part alkali activated slag-fly ash (AASF) paste is examined at the microscopic level. A special mini creep rig is constructed enabling in-situ monitoring of water redistribution over time between high- and low-density (HD, LD) gel pores within the loaded paste specimens using <sup>1</sup>H NMR relaxometry. The results suggest that the contraction of C-(N)-A-S-H particles is accompanied by the reduction of water content in HD gel for loaded AASF paste. In contrast, in the loaded OPC paste a noticeable decrease of water residing in LD rather than HD C-S-H gel was observed, implying the presence of a distinct creep mechanism. In addition to the different water environment, the more crosslinked bonding structure of AASF could partially account for its lower creep response supported by <sup>29</sup>Si NMR measurement. The findings of this study provide evidence in understanding underlying basic creep mechanism of AASF.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107691"},"PeriodicalIF":10.9,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142384423","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 : 2024-10-02DOI: 10.1016/j.cemconres.2024.107690
Weihuan Li , Chenchen Xiong , Yang Zhou , Wentao Chen , Yangzezhi Zheng , Wei Lin , Jiarui Xing
The molecular-scale mechanical properties of calcium silicate hydrates are crucial to the macro performance of cementitious materials, while achieving coincidence between accuracy and efficiency in computational simulations still remains a challenge. This study utilizes a deep-learning potential, specifically developed for calcium silicate hydrates based on artificial neural network, to achieve molecular dynamics simulations with accuracy comparable to first-principle methods. With this potential, the elastic properties and uniaxial mechanical behaviors are explored, wherein the anisotropy and impact mechanism of calcium ratios are analyzed. The results add to evidence that the deep-learning potential possess a higher accuracy than common force fields. The anisotropy of elastic modulus is mainly attributed to different atomic interactions in various directions, while the anisotropy of strength is additionally affected by the form of failure. This study may advance the accurate molecular-scale simulation and deepen the understanding of the strength source and cohesion mechanism of cement-based materials.
{"title":"Insights on the mechanical properties and failure mechanisms of calcium silicate hydrates based on deep-learning potential molecular dynamics","authors":"Weihuan Li , Chenchen Xiong , Yang Zhou , Wentao Chen , Yangzezhi Zheng , Wei Lin , Jiarui Xing","doi":"10.1016/j.cemconres.2024.107690","DOIUrl":"10.1016/j.cemconres.2024.107690","url":null,"abstract":"<div><div>The molecular-scale mechanical properties of calcium silicate hydrates are crucial to the macro performance of cementitious materials, while achieving coincidence between accuracy and efficiency in computational simulations still remains a challenge. This study utilizes a deep-learning potential, specifically developed for calcium silicate hydrates based on artificial neural network, to achieve molecular dynamics simulations with accuracy comparable to first-principle methods. With this potential, the elastic properties and uniaxial mechanical behaviors are explored, wherein the anisotropy and impact mechanism of calcium ratios are analyzed. The results add to evidence that the deep-learning potential possess a higher accuracy than common force fields. The anisotropy of elastic modulus is mainly attributed to different atomic interactions in various directions, while the anisotropy of strength is additionally affected by the form of failure. This study may advance the accurate molecular-scale simulation and deepen the understanding of the strength source and cohesion mechanism of cement-based materials.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107690"},"PeriodicalIF":10.9,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142369632","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 : 2024-10-02DOI: 10.1016/j.cemconres.2024.107686
Guitao Luo , Muyu Liu , Hua Li , Yang Liu , Hongbo Tan , Qimin Liu
Adsorption effect on particle surfaces and complexation effect with free Ca2+ mostly determine the retarding performance of organic admixtures on cement hydration. However, it is difficult to identify which effect plays a more important role in retarding hydration by experimental methods. Here, a theoretical model was developed to investigate the retarding mechanisms of sodium gluconate (SG) on hydration of tricalcium silicate (C3S). Based on obstruction theory and complexation reaction kinetics, effects of adsorption and complexation were simulated to examine the retarding performance of C3S hydration with addition of SG. The proposed model well predicted the effect of additional dosing of SG on the retarding performance of C3S hydration. Theoretical parameter studies demonstrated that adsorption ratio contributed much largely to the delays in C3S hydration, compared with rate constant of complex generation. Therefore, it is confirmed that adsorption plays a more important role in regulating the retarding mechanism of C3S hydration.
{"title":"Importance of adsorption compared with complexation for retarding C3S hydration via adding sodium gluconate","authors":"Guitao Luo , Muyu Liu , Hua Li , Yang Liu , Hongbo Tan , Qimin Liu","doi":"10.1016/j.cemconres.2024.107686","DOIUrl":"10.1016/j.cemconres.2024.107686","url":null,"abstract":"<div><div>Adsorption effect on particle surfaces and complexation effect with free Ca<sup>2+</sup> mostly determine the retarding performance of organic admixtures on cement hydration. However, it is difficult to identify which effect plays a more important role in retarding hydration by experimental methods. Here, a theoretical model was developed to investigate the retarding mechanisms of sodium gluconate (SG) on hydration of tricalcium silicate (C<sub>3</sub>S). Based on obstruction theory and complexation reaction kinetics, effects of adsorption and complexation were simulated to examine the retarding performance of C<sub>3</sub>S hydration with addition of SG. The proposed model well predicted the effect of additional dosing of SG on the retarding performance of C<sub>3</sub>S hydration. Theoretical parameter studies demonstrated that adsorption ratio contributed much largely to the delays in C<sub>3</sub>S hydration, compared with rate constant of complex generation. Therefore, it is confirmed that adsorption plays a more important role in regulating the retarding mechanism of C<sub>3</sub>S hydration.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107686"},"PeriodicalIF":10.9,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142369637","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 : 2024-09-28DOI: 10.1016/j.cemconres.2024.107685
Hela Bessaies-Bey , Xiaohan Yu , Wenqiang Zuo , Oumayma Ahmadah , Janine Deou , Laura Caneda-Martínez , Nicolas Roussel
This paper introduces three major recommendations for the assessment of the maximum packing fraction of mineral powders through compressive rheology. First, our results show that a minimum compressive stress is required for the measured solid volume fraction to tend towards a constant jamming fraction. Second, we show that the modification of the particles surface properties, especially their friction coefficient, by polymer adsorption, allows for this jamming fraction to get closer to the particle maximum packing fraction. Finally, we show that a minimal value of the initial solid volume fraction of a sample is necessary to prevent particle size separation during testing. We moreover show that the measured jamming fraction depends on the initial solid volume fraction of cement-based samples. We suggest that such a peculiar behavior finds its origin in the dependency of early hydrates volume or morphology on the initial supersaturation.
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