The combined effects of water pressure and water penetration on the mechanical behavior of concrete under hydraulic loading were investigated. When concrete is subjected to water pressure, a saturated zone forms near the surface and gradually progresses toward the interior over time, resulting in a non-homogeneous hybrid state with a saturated envelope and humid core (hybrid saturated state) during the initial stages of hydraulic loading. However, the mechanical behavior of concrete with a hybrid saturated state has hardly been investigated. This study performed the experiments on concretes with water pressures (~50 MPa). The results show that concrete with a hybrid saturated state exhibits higher peak mechanical stress than unconfined concrete. In contrast, the peak mechanical stress of fully saturated concrete remains comparable to that of unconfined concrete. This indicates that water penetration strongly influences the triaxial strength of concrete under water pressure, especially in the initial stages of hydraulic loading.
{"title":"Mechanical behavior of concrete under high water pressure: Water penetration as a critical factor for mechanical properties","authors":"Atichon Kunawisarut , Yuichiro Kawabata , Mitsuyasu Iwanami","doi":"10.1016/j.cemconres.2025.107820","DOIUrl":"10.1016/j.cemconres.2025.107820","url":null,"abstract":"<div><div>The combined effects of water pressure and water penetration on the mechanical behavior of concrete under hydraulic loading were investigated. When concrete is subjected to water pressure, a saturated zone forms near the surface and gradually progresses toward the interior over time, resulting in a non-homogeneous hybrid state with a saturated envelope and humid core (hybrid saturated state) during the initial stages of hydraulic loading. However, the mechanical behavior of concrete with a hybrid saturated state has hardly been investigated. This study performed the experiments on concretes with water pressures (~50 MPa). The results show that concrete with a hybrid saturated state exhibits higher peak mechanical stress than unconfined concrete. In contrast, the peak mechanical stress of fully saturated concrete remains comparable to that of unconfined concrete. This indicates that water penetration strongly influences the triaxial strength of concrete under water pressure, especially in the initial stages of hydraulic loading.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107820"},"PeriodicalIF":10.9,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350543","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 : 2025-02-06DOI: 10.1016/j.cemconres.2025.107818
Yanrong Zhang , Xuesong Zhang , Zichen Lu , Kai Wu , Xiaopei Cai
Hydrophobic-modified silica fume (HSF) with superior dispersion was synthesized by coating silane onto SF surface. Its influence on cement hydration, microstructure and properties of cement pastes was investigated. Results indicated that the silane on SF surface visibly depressed pozzolanic reaction at early ages. HSF retarded cement hydration by adsorbing on cement surface and more importantly, by interacting with Ca2+ in aqueous phase. For the first time, the accumulation of calcium around HSF was observed, leading to the growth of needle-like C–S–H perpendicular to HSF surface and eventually evolved into loose honeycomb-like gels. These loose gels promoted pozzolanic reaction and cement hydration at late ages. TEM and XRD results revealed that silane incorporated itself into C–S–H and altered structural order. Furthermore, adding HSF increased capillary pore size but refined the inter-hydrate pores at late ages. HSF visibly decreased the compressive strength compared with SF; however, the difference diminished at late ages.
{"title":"New insight into the effects of silane-modified silica fume on the performance of cement pastes","authors":"Yanrong Zhang , Xuesong Zhang , Zichen Lu , Kai Wu , Xiaopei Cai","doi":"10.1016/j.cemconres.2025.107818","DOIUrl":"10.1016/j.cemconres.2025.107818","url":null,"abstract":"<div><div>Hydrophobic-modified silica fume (HSF) with superior dispersion was synthesized by coating silane onto SF surface. Its influence on cement hydration, microstructure and properties of cement pastes was investigated. Results indicated that the silane on SF surface visibly depressed pozzolanic reaction at early ages. HSF retarded cement hydration by adsorbing on cement surface and more importantly, by interacting with Ca<sup>2+</sup> in aqueous phase. For the first time, the accumulation of calcium around HSF was observed, leading to the growth of needle-like C–S–H perpendicular to HSF surface and eventually evolved into loose honeycomb-like gels. These loose gels promoted pozzolanic reaction and cement hydration at late ages. TEM and XRD results revealed that silane incorporated itself into C–S–H and altered structural order. Furthermore, adding HSF increased capillary pore size but refined the inter-hydrate pores at late ages. HSF visibly decreased the compressive strength compared with SF; however, the difference diminished at late ages.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107818"},"PeriodicalIF":10.9,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143191860","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 : 2025-02-04DOI: 10.1016/j.cemconres.2025.107819
Yuefeng Ma , Ming Jin , Fei Wang , Diederik Jacques , Xuyan Shen , Jian Zhang , Chang Gao , Haoyu Zeng , Jingwen Liu , Jiaping Liu
Transformation of C-S-H is crucial in the deterioration of concrete at high temperatures. This study investigates the composition, structure, and morphology of C-S-H from 30 °C to 1000 °C using in-situ heating XRD, TGA/TG-IR, in-situ heating XPS, and in-situ heating TEM combined with image recognition. The results reveal that during heating, C-S-H undergoes weakly and strongly bound water loss, dehydroxylation, and transformation into CaSiO3. During heating, the Si-O-Si bonds within C-S-H silicate chains remain highly stable. The primary change observed is the conversion of Si-OH groups into Si-O-Ca/Na following dehydroxylation. TEM morphology exhibits shrinkage and densification similar to ceramic sintering, with the overall process divided into five stages. The first three stages are dominated by dehydration and dehydroxylation, while the final two stages are governed by phase changes and liquid-phase sintering. The dehydration of C-S-H in the first stage has the greatest impact on shrinkage, while the fourth stage transforms the C-S-H morphology from foil-like to drop-like, having the largest effect on densification. Although the Ca/Si ratio of C-S-H remains constant during the heating, the crystallinity decreases. This study offers new insights into the mechanisms driving the transformation of C-S-H under heating.
{"title":"Heating-induced transformations in calcium silicate hydrate (C-S-H): In-situ investigations of composition, structure, and morphology","authors":"Yuefeng Ma , Ming Jin , Fei Wang , Diederik Jacques , Xuyan Shen , Jian Zhang , Chang Gao , Haoyu Zeng , Jingwen Liu , Jiaping Liu","doi":"10.1016/j.cemconres.2025.107819","DOIUrl":"10.1016/j.cemconres.2025.107819","url":null,"abstract":"<div><div>Transformation of C-S-H is crucial in the deterioration of concrete at high temperatures. This study investigates the composition, structure, and morphology of C-S-H from 30 °C to 1000 °C using in-situ heating XRD, TGA/TG-IR, in-situ heating XPS, and in-situ heating TEM combined with image recognition. The results reveal that during heating, C-S-H undergoes weakly and strongly bound water loss, dehydroxylation, and transformation into CaSiO<sub>3</sub>. During heating, the Si-O-Si bonds within C-S-H silicate chains remain highly stable. The primary change observed is the conversion of Si-OH groups into Si-O-Ca/Na following dehydroxylation. TEM morphology exhibits shrinkage and densification similar to ceramic sintering, with the overall process divided into five stages. The first three stages are dominated by dehydration and dehydroxylation, while the final two stages are governed by phase changes and liquid-phase sintering. The dehydration of C-S-H in the first stage has the greatest impact on shrinkage, while the fourth stage transforms the C-S-H morphology from foil-like to drop-like, having the largest effect on densification. Although the Ca/Si ratio of C-S-H remains constant during the heating, the crystallinity decreases. This study offers new insights into the mechanisms driving the transformation of C-S-H under heating.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107819"},"PeriodicalIF":10.9,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083781","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}
Alkali-Silica Reaction (ASR) is a long-term chemical degradation induced in concrete by the difference in pH between the aggregate and the cement paste. ASR advancement is thus driven by the combination of the ionic species diffusion and the dissolution of reactive silica. In this paper, the reactive transport model is based on the principal sequence of the ASR-mechanisms: hydroxide, alkali and calcium diffusion, silica dissolution and reaction products precipitation. First, the proposed model highlights the impact of the competition between diffusion and dissolution kinetic on the formation of products in the depth of the aggregate particles according to the calcium concentration. Secondly, the numerical study on the size effect of the aggregate particles highlights the efficacy of this approach to reproduce the dependence of the products type formed during precipitation, allowing for the competition between ASR and pozzolanic effect to be reproduced.
{"title":"Numerical investigation of mechanisms affecting alkali-silica reaction advancement by reactive transport simulations","authors":"Lucie Gomez , Frédéric Perales , Stéphane Multon , Adrien Socié , Benoit Fournier , Matthieu Argouges","doi":"10.1016/j.cemconres.2025.107791","DOIUrl":"10.1016/j.cemconres.2025.107791","url":null,"abstract":"<div><div>Alkali-Silica Reaction (ASR) is a long-term chemical degradation induced in concrete by the difference in pH between the aggregate and the cement paste. ASR advancement is thus driven by the combination of the ionic species diffusion and the dissolution of reactive silica. In this paper, the reactive transport model is based on the principal sequence of the ASR-mechanisms: hydroxide, alkali and calcium diffusion, silica dissolution and reaction products precipitation. First, the proposed model highlights the impact of the competition between diffusion and dissolution kinetic on the formation of products in the depth of the aggregate particles according to the calcium concentration. Secondly, the numerical study on the size effect of the aggregate particles highlights the efficacy of this approach to reproduce the dependence of the products type formed during precipitation, allowing for the competition between ASR and pozzolanic effect to be reproduced.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107791"},"PeriodicalIF":10.9,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143077298","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 : 2025-02-03DOI: 10.1016/j.cemconres.2025.107813
Zirui Fan , Dujian Zou , Ming Zhang , Shanshan Qin , Tiejun Liu
Severe scaling and spalling are commonly observed on tunnel lining surfaces in sulfate-rich environments. Due to humidity gradients, sulfate solution in rock fissures migrates through capillary action to the concrete exposed face, leading to physical crystallization precipitation at free-face zone and chemical sulfate attack at soil-facing zone, resulting in concrete expansion and crack. Existing models focus on full immersion or wet-dry cycles, which have obvious errors in predicting concrete damage under similar partial immersion. Considering the time-varying characteristics of saturation, porosity, calcium leaching and crack, a transport-reaction-expansion model for lining concrete under dual sulfate attacks and water evaporation was established. The spatiotemporal distribution of phase composition and the influence of modeling parameters on concrete expansion were revealed. The expansion strain caused by dual sulfate attacks and changes in the water evaporation zone was discussed. These findings provide a theoretical foundation for the durability design of lining concrete in sulfate-rich environment.
{"title":"Numerical modeling of unidirectional sulfate attack on tunnel lining concrete considering water evaporation at free face","authors":"Zirui Fan , Dujian Zou , Ming Zhang , Shanshan Qin , Tiejun Liu","doi":"10.1016/j.cemconres.2025.107813","DOIUrl":"10.1016/j.cemconres.2025.107813","url":null,"abstract":"<div><div>Severe scaling and spalling are commonly observed on tunnel lining surfaces in sulfate-rich environments. Due to humidity gradients, sulfate solution in rock fissures migrates through capillary action to the concrete exposed face, leading to physical crystallization precipitation at free-face zone and chemical sulfate attack at soil-facing zone, resulting in concrete expansion and crack. Existing models focus on full immersion or wet-dry cycles, which have obvious errors in predicting concrete damage under similar partial immersion. Considering the time-varying characteristics of saturation, porosity, calcium leaching and crack, a transport-reaction-expansion model for lining concrete under dual sulfate attacks and water evaporation was established. The spatiotemporal distribution of phase composition and the influence of modeling parameters on concrete expansion were revealed. The expansion strain caused by dual sulfate attacks and changes in the water evaporation zone was discussed. These findings provide a theoretical foundation for the durability design of lining concrete in sulfate-rich environment.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107813"},"PeriodicalIF":10.9,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143077299","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 : 2025-02-03DOI: 10.1016/j.cemconres.2025.107815
Suhui Zhang , Min Liu , Keren Zheng , Lou Chen , Caijun Shi , Qiang Yuan
A new insight into self-antifoaming effect of CO2 bubble was proposed by exploring the evolution of entrained CO2 bubbles in fresh cement paste. The disappearance process of CO2 bubbles was observed, resulting in the reduction of air content. The evolution of CO2 bubbles eventually formed two kinds of pore structures: hollow spherical shell structure (HSS) and interior filled spherical shell structure (IFSS). It was evidenced by the rich area of CaCO3 at the outline of CO2 bubble and the interior formation of hydration products. Meanwhile, self-antifoaming effect of CO2 bubble promoted the microstructural build-up of fresh cement paste and enhanced the mechanical property of hardened cement paste. Fresh cement paste with CO2 bubbles had stronger elasticity and higher volume resistance, corresponding to the faster rise of storage modulus. The compressive strength of hardened cement paste was increased from 29.6 MPa to 37.3 MPa with a porosity reduction of 6%.
{"title":"New insight into self-antifoaming effect of entrained CO2 bubbles in fresh cement paste","authors":"Suhui Zhang , Min Liu , Keren Zheng , Lou Chen , Caijun Shi , Qiang Yuan","doi":"10.1016/j.cemconres.2025.107815","DOIUrl":"10.1016/j.cemconres.2025.107815","url":null,"abstract":"<div><div>A new insight into self-antifoaming effect of CO<sub>2</sub> bubble was proposed by exploring the evolution of entrained CO<sub>2</sub> bubbles in fresh cement paste. The disappearance process of CO<sub>2</sub> bubbles was observed, resulting in the reduction of air content. The evolution of CO<sub>2</sub> bubbles eventually formed two kinds of pore structures: hollow spherical shell structure (HSS) and interior filled spherical shell structure (IFSS). It was evidenced by the rich area of CaCO<sub>3</sub> at the outline of CO<sub>2</sub> bubble and the interior formation of hydration products. Meanwhile, self-antifoaming effect of CO<sub>2</sub> bubble promoted the microstructural build-up of fresh cement paste and enhanced the mechanical property of hardened cement paste. Fresh cement paste with CO<sub>2</sub> bubbles had stronger elasticity and higher volume resistance, corresponding to the faster rise of storage modulus. The compressive strength of hardened cement paste was increased from 29.6 MPa to 37.3 MPa with a porosity reduction of 6%.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107815"},"PeriodicalIF":10.9,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143077300","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 : 2025-02-01DOI: 10.1016/j.cemconres.2025.107814
Xiaobo Niu , Yogarajah Elakneswaran , Ang Li , Sivasubramaniam Seralathan , Ryosuke Kikuchi , Yoshihisa Hiraki , Junya Sato , Takeshi Osugi , Brant Walkley
Metakaolin-based geopolymers have attracted significant interest in decontaminating radioactive debris from the Fukushima nuclear accident. This study explored the incorporation of boron (B) into geopolymers using boric acid as the source, with the goal of developing B-enriched geopolymers for enhanced radionuclide immobilisation and neutron capture potential. The addition of boric acid lowered the pH of the alkali activator, reducing metakaolin solubility and impeding alkali-activated geopolymerisation. B formed an unstable BO4(xB, 4-xSi) structure with extra short-range Si tetrahedra in low-temperature curing conditions, making it prone to be leached out. High-temperature curing facilitated alkali-activated geopolymerisation, mitigating some negative effects of boric acid. It also promoted partial incorporation of BO4 into the framework, reducing leaching. Additionally, in acid-activated geopolymers, boric acid absorbed substantial reaction heat during the initial dealumination phase by reacting with PO4, thereby enhancing the overall geopolymerisation degree and increasing the relative content of near-Si terminal P and Al6 units. B could be incorporated into the framework by bonding with numerous Al-unsaturated Si tetrahedra to form a stable BO4(0B, 4Si) structure. Although B introduction slightly reduced the positive charge of the acid-activated geopolymer's structure, decreasing its capacity to immobilise anionic SeO32− through electrostatic adsorption, the decrease was negligible. Conversely, B introduction increased structural compactness, which improved Cs+ immobilisation through physical entrapment. Overall, the B-containing acid-activated geopolymer effectively incorporated B into the main matrix while maintaining radionuclide immobilisation capacity. This study provides valuable insights into the selection and incorporation mechanisms of the B-containing geopolymer matrix, contributing to effective strategies for radioactive waste disposal.
{"title":"Incorporation of boron into metakaolin-based geopolymers for radionuclide immobilisation and neutron capture potential","authors":"Xiaobo Niu , Yogarajah Elakneswaran , Ang Li , Sivasubramaniam Seralathan , Ryosuke Kikuchi , Yoshihisa Hiraki , Junya Sato , Takeshi Osugi , Brant Walkley","doi":"10.1016/j.cemconres.2025.107814","DOIUrl":"10.1016/j.cemconres.2025.107814","url":null,"abstract":"<div><div>Metakaolin-based geopolymers have attracted significant interest in decontaminating radioactive debris from the Fukushima nuclear accident. This study explored the incorporation of boron (B) into geopolymers using boric acid as the source, with the goal of developing B-enriched geopolymers for enhanced radionuclide immobilisation and neutron capture potential. The addition of boric acid lowered the pH of the alkali activator, reducing metakaolin solubility and impeding alkali-activated geopolymerisation. B formed an unstable BO<sub>4</sub>(xB, 4-xSi) structure with extra short-range Si tetrahedra in low-temperature curing conditions, making it prone to be leached out. High-temperature curing facilitated alkali-activated geopolymerisation, mitigating some negative effects of boric acid. It also promoted partial incorporation of BO<sub>4</sub> into the framework, reducing leaching. Additionally, in acid-activated geopolymers, boric acid absorbed substantial reaction heat during the initial dealumination phase by reacting with PO<sub>4</sub>, thereby enhancing the overall geopolymerisation degree and increasing the relative content of near-Si terminal P and Al<sub>6</sub> units. B could be incorporated into the framework by bonding with numerous Al-unsaturated Si tetrahedra to form a stable BO<sub>4</sub>(0B, 4Si) structure. Although B introduction slightly reduced the positive charge of the acid-activated geopolymer's structure, decreasing its capacity to immobilise anionic SeO<sub>3</sub><sup>2−</sup> through electrostatic adsorption, the decrease was negligible. Conversely, B introduction increased structural compactness, which improved Cs<sup>+</sup> immobilisation through physical entrapment. Overall, the B-containing acid-activated geopolymer effectively incorporated B into the main matrix while maintaining radionuclide immobilisation capacity. This study provides valuable insights into the selection and incorporation mechanisms of the B-containing geopolymer matrix, contributing to effective strategies for radioactive waste disposal.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107814"},"PeriodicalIF":10.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143072463","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 : 2025-02-01DOI: 10.1016/j.cemconres.2024.107732
S. Mingione , D. Jansen , F. Winnefeld , S.V. Churakov , B. Lothenbach
Xonotlite forms under hydrothermal conditions and it dehydrates to β-wollastonite between 770 and 800 °C under atmospheric pressure. The solubility of xonotlite is poorly known, as the experimental datasets reported in literature differ by as much as 10 log units. This study investigates the impact of temperature (7, 20, 50 and 80 °C) on the solubility of xonotlite by dissolution experiments from undersaturation. The derived solubility data are comparable to those reported in literature at 25 °C for synthesized xonotlite, while the much higher solubility reported in literature for natural xonotlite seems to describe the solubility of amorphous C-S-H. The solubility of xonotlite increases moderately at lower temperature. At 7 °C, xonotlite was found to co-exist with tobermorite.
硅灰石在水热条件下形成，在770 ~ 800℃大气压下脱水成β-硅灰石。硅钙石的溶解度鲜为人知，因为文献中报道的实验数据集相差多达10个对数单位。通过欠饱和溶解实验，研究了温度（7、20、50和80℃）对硬硅橄榄石溶解度的影响。导出的溶解度数据与文献中报道的合成硬硅钙石在25°C下的溶解度数据相当，而文献中报道的天然硬硅钙石更高的溶解度似乎描述了无定形C- s - h的溶解度。硅钙石的溶解度在较低温度下适度提高。在7℃时，发现硅钙石与托贝莫来石共存。
{"title":"Effect of temperature on the solubility of xonotlite","authors":"S. Mingione , D. Jansen , F. Winnefeld , S.V. Churakov , B. Lothenbach","doi":"10.1016/j.cemconres.2024.107732","DOIUrl":"10.1016/j.cemconres.2024.107732","url":null,"abstract":"<div><div>Xonotlite forms under hydrothermal conditions and it dehydrates to β-wollastonite between 770 and 800 °C under atmospheric pressure. The solubility of xonotlite is poorly known, as the experimental datasets reported in literature differ by as much as 10 log units. This study investigates the impact of temperature (7, 20, 50 and 80 °C) on the solubility of xonotlite by dissolution experiments from undersaturation. The derived solubility data are comparable to those reported in literature at 25 °C for synthesized xonotlite, while the much higher solubility reported in literature for natural xonotlite seems to describe the solubility of amorphous C-S-H. The solubility of xonotlite increases moderately at lower temperature. At 7 °C, xonotlite was found to co-exist with tobermorite.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"188 ","pages":"Article 107732"},"PeriodicalIF":10.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142760007","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 : 2025-02-01DOI: 10.1016/j.cemconres.2025.107816
Xiaohan Yu , Le Teng , Xin Shu , Xin Liu , Xiaoxian Wang , Jiang Zhu , Jiaping Liu
Recent findings indicate that the effect of superplasticizers on decreasing the yield stress of cementitious suspensions is attributed to the modification of percolation threshold in addition to interparticle force. These dual effects complicate the assessment of yield stress dependence on the superplasticizer type and dosage, as yield stress can no longer be expressed as a separable function of interparticle forces and the number of interacting particles. To address this challenge, our study proposed scaling laws that directly linked yield stress to the surface coverage of superplasticizer by incorporating the percolation threshold into the interparticle force function. The scaling relation between surface coverage and viscosity was moreover established. At low surface coverages, the combined contributions of interparticle force and percolation threshold to the yield stress were characterized using the square of polymer devoid contact frequency. Furthermore, the viscosity varied linearly with the square root of this frequency, scaling with the quarter power of yield stress. In the high surface coverage regime, the yield stress was linearly dependent on the polymer devoid contact frequency given the limited variation of interparticle force. The proposed scaling laws can account well for the rheological property dependences on superplasticizer adsorption over a wide range of cement suspensions, holding significant values for controlling the yield stress and viscosity of cement-based materials in industrial practice.
{"title":"New insights into the surface coverage dependences of rheological properties of cement paste: Measurement and scaling analysis","authors":"Xiaohan Yu , Le Teng , Xin Shu , Xin Liu , Xiaoxian Wang , Jiang Zhu , Jiaping Liu","doi":"10.1016/j.cemconres.2025.107816","DOIUrl":"10.1016/j.cemconres.2025.107816","url":null,"abstract":"<div><div>Recent findings indicate that the effect of superplasticizers on decreasing the yield stress of cementitious suspensions is attributed to the modification of percolation threshold in addition to interparticle force. These dual effects complicate the assessment of yield stress dependence on the superplasticizer type and dosage, as yield stress can no longer be expressed as a separable function of interparticle forces and the number of interacting particles. To address this challenge, our study proposed scaling laws that directly linked yield stress to the surface coverage of superplasticizer by incorporating the percolation threshold into the interparticle force function. The scaling relation between surface coverage and viscosity was moreover established. At low surface coverages, the combined contributions of interparticle force and percolation threshold to the yield stress were characterized using the square of polymer devoid contact frequency. Furthermore, the viscosity varied linearly with the square root of this frequency, scaling with the quarter power of yield stress. In the high surface coverage regime, the yield stress was linearly dependent on the polymer devoid contact frequency given the limited variation of interparticle force. The proposed scaling laws can account well for the rheological property dependences on superplasticizer adsorption over a wide range of cement suspensions, holding significant values for controlling the yield stress and viscosity of cement-based materials in industrial practice.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107816"},"PeriodicalIF":10.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143072508","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 : 2025-02-01DOI: 10.1016/j.cemconres.2024.107730
K. De Weerdt , M. Bagheri , J. Lindgård , H. Lindstad , A. Rodrigues , J. Duchesne , P.-L. Fecteau , M.K. Haugen , T. Danner , B.J. Wigum , N. Oberhardt , K. Aasly , B. Lothenbach
The accelerated mortar bar test (AMBT) for pyrrhotite (Fe1-xS) containing aggregates accelerates expansion using two regimes: Phase I, during which Fe1-xS oxidation to iron hydroxide is accelerated by bleach and storage at 80 °C; Phase II that promotes thaumasite formation with continued bleach soaking and storage at 4 °C. Two bleach concentrations and one aggregate containing 0.5 wt% Fe1-xS are tested. SEM-EDX data indicate that the oxidized iron precipitates as iron hydroxide at the place of the Fe1-xS, leading to significant expansion (0.22%) during Phase I. The released S distributes in the cement paste but leads only to limited amount of additional ettringite and thaumasite and thus only to limited expansion (0.07%). The NaOCl bleach reduced during the test resulting in chloride and thus to Friedel's salt formation and ettringite stabilization at 80 °C. Only during the prolongation of Phase II, the formation of thaumasite and additional expansion was observed.
{"title":"Changes in cement paste during accelerated mortar bar testing for pyrrhotite containing aggregate","authors":"K. De Weerdt , M. Bagheri , J. Lindgård , H. Lindstad , A. Rodrigues , J. Duchesne , P.-L. Fecteau , M.K. Haugen , T. Danner , B.J. Wigum , N. Oberhardt , K. Aasly , B. Lothenbach","doi":"10.1016/j.cemconres.2024.107730","DOIUrl":"10.1016/j.cemconres.2024.107730","url":null,"abstract":"<div><div>The accelerated mortar bar test (AMBT) for pyrrhotite (Fe<sub>1-x</sub>S) containing aggregates accelerates expansion using two regimes: Phase I, during which Fe<sub>1-x</sub>S oxidation to iron hydroxide is accelerated by bleach and storage at 80 °C; Phase II that promotes thaumasite formation with continued bleach soaking and storage at 4 °C. Two bleach concentrations and one aggregate containing 0.5 wt% Fe<sub>1-x</sub>S are tested. SEM-EDX data indicate that the oxidized iron precipitates as iron hydroxide at the place of the Fe<sub>1-x</sub>S, leading to significant expansion (0.22%) during Phase I. The released S distributes in the cement paste but leads only to limited amount of additional ettringite and thaumasite and thus only to limited expansion (0.07%). The NaOCl bleach reduced during the test resulting in chloride and thus to Friedel's salt formation and ettringite stabilization at 80 °C. Only during the prolongation of Phase II, the formation of thaumasite and additional expansion was observed.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"188 ","pages":"Article 107730"},"PeriodicalIF":10.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142760591","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}
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