Pub Date : 2025-04-05DOI: 10.1016/j.cemconres.2025.107891
Hamideh Mehdizadeh , Tung-Chai Ling
Alkaline solid wastes, such as recycled concrete fines, can integrate with CO2 to produce high-purity vaterite CaCO3 via leaching‑carbonation mineralization. This study aims to examine the stability and nucleation effects of the metastable vaterite relative to stable conventional calcite in cement paste systems. To better elucidate the underlying mechanisms, their influence in the pure C3S/C3A phase systems was also comparatively studied. The results indicate that vaterite accelerates the hydration rate of C3S and C3A phases, resulting in the formation of both crystalline and amorphous calcium silicate hydrates, as well as carbonate-Am phases, within the first 12 h of hydration. The spherical morphology of vaterite facilitates a more uniform distribution of hydration products, leading to particle encapsulation and reduced nucleation effects at later ages (> 7 days). Overall, vaterite blended cement pastes exhibit 40% higher early strength at 7 days and comparable long-term mechanical properties to those made with calcite.
{"title":"Hydration and strength of cement paste containing metastable vaterite derived from recycled concrete fines and CO2","authors":"Hamideh Mehdizadeh , Tung-Chai Ling","doi":"10.1016/j.cemconres.2025.107891","DOIUrl":"10.1016/j.cemconres.2025.107891","url":null,"abstract":"<div><div>Alkaline solid wastes, such as recycled concrete fines, can integrate with CO<sub>2</sub> to produce high-purity vaterite CaCO<sub>3</sub> via leaching‑carbonation mineralization. This study aims to examine the stability and nucleation effects of the metastable vaterite relative to stable conventional calcite in cement paste systems. To better elucidate the underlying mechanisms, their influence in the pure C<sub>3</sub>S/C<sub>3</sub>A phase systems was also comparatively studied. The results indicate that vaterite accelerates the hydration rate of C<sub>3</sub>S and C<sub>3</sub>A phases, resulting in the formation of both crystalline and amorphous calcium silicate hydrates, as well as carbonate-Am phases, within the first 12 h of hydration. The spherical morphology of vaterite facilitates a more uniform distribution of hydration products, leading to particle encapsulation and reduced nucleation effects at later ages (> 7 days). Overall, vaterite blended cement pastes exhibit 40% higher early strength at 7 days and comparable long-term mechanical properties to those made with calcite.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"194 ","pages":"Article 107891"},"PeriodicalIF":10.9,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143777122","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 : 2025-03-31DOI: 10.1016/j.cemconres.2025.107872
Elisabeth John , Cordula Jakob , Ursula Pott , Mona Sando
Isothermal heat flow calorimetry evaluates heat development during binder reactions. It distinguishes between in situ calorimetry, where mixing occurs within the device, and ex situ calorimetry, involving externally mixed samples. Despite ex situ calorimetry being a standard method in binder research, in situ calorimetry is underutilized. This paper aims to promote its adoption by summarizing challenges related to repeatability and reproducibility and offering solutions. The initial section addresses repeatability issues caused by preventable errors, providing a structured guide for experimental design. It was found that water leakage had minimal impact, and sample size is crucial for data robustness. The second section examines operational challenges, revealing that frictional heating, affecting recorded heat, can be minimized with an optimized mixing protocol. The final part highlights that significant errors in measured data stem from signal delay and heat loss, offering methods to correct these issues for improved reproducibility in in situ calorimetric experiments.
{"title":"Repeatability and reproducibility challenges of isothermal heat flow calorimetry with in situ mixing","authors":"Elisabeth John , Cordula Jakob , Ursula Pott , Mona Sando","doi":"10.1016/j.cemconres.2025.107872","DOIUrl":"10.1016/j.cemconres.2025.107872","url":null,"abstract":"<div><div>Isothermal heat flow calorimetry evaluates heat development during binder reactions. It distinguishes between in situ calorimetry, where mixing occurs within the device, and ex situ calorimetry, involving externally mixed samples. Despite ex situ calorimetry being a standard method in binder research, in situ calorimetry is underutilized. This paper aims to promote its adoption by summarizing challenges related to repeatability and reproducibility and offering solutions. The initial section addresses repeatability issues caused by preventable errors, providing a structured guide for experimental design. It was found that water leakage had minimal impact, and sample size is crucial for data robustness. The second section examines operational challenges, revealing that frictional heating, affecting recorded heat, can be minimized with an optimized mixing protocol. The final part highlights that significant errors in measured data stem from signal delay and heat loss, offering methods to correct these issues for improved reproducibility in in situ calorimetric experiments.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"194 ","pages":"Article 107872"},"PeriodicalIF":10.9,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143737214","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 : 2025-03-31DOI: 10.1016/j.cemconres.2025.107883
Antonela Di Salvo Barsi, Mónica A. Trezza, Edgardo F. Irassar
This study examines the stability of dolomitic filler (DF), both in isolation and in interaction with supplementary cementitious materials (SCMs), when immersed in water media at different pH at 40 °C. Additionally, the interaction of DF with Portland cement (PC) is analyzed. In the presence of SCMs or PC, results reveal that DF undergoes dedolomitization in alkaline environments, which confirms the absence of brucite in this process. As corroboration, the volumetric stability of mortar bars containing 20 wt% DF is demonstrated and the compressive strength remained after immersion in pore water at 40 °C for 5 years.
{"title":"Dedolomitization of dolostone filler: Modifying the course of Mg with SCM","authors":"Antonela Di Salvo Barsi, Mónica A. Trezza, Edgardo F. Irassar","doi":"10.1016/j.cemconres.2025.107883","DOIUrl":"10.1016/j.cemconres.2025.107883","url":null,"abstract":"<div><div>This study examines the stability of dolomitic filler (DF), both in isolation and in interaction with supplementary cementitious materials (SCMs), when immersed in water media at different pH at 40 °C. Additionally, the interaction of DF with Portland cement (PC) is analyzed. In the presence of SCMs or PC, results reveal that DF undergoes dedolomitization in alkaline environments, which confirms the absence of brucite in this process. As corroboration, the volumetric stability of mortar bars containing 20 wt% DF is demonstrated and the compressive strength remained after immersion in pore water at 40 °C for 5 years.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"194 ","pages":"Article 107883"},"PeriodicalIF":10.9,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143737215","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 : 2025-03-29DOI: 10.1016/j.cemconres.2025.107882
Piumika W. Ariyadasa , Allan C. Manalo , Weena Lokuge , Vasantha Aravienthan , Andreas Gerdes , Jonas Kaltenbach
Alkali-activated geopolymers are increasingly studied as alternatives to Ordinary Portland Cement (OPC) concrete for use in challenging service environments. Low-calcium geopolymers have been advocated to mitigate Microbial-Induced Concrete Corrosion (MICC) in sewer pipes; however, their broader acceptance as a repair material for sewer rehabilitation remains to be established. This study evaluated the degradation mechanism of low-calcium fly ash-based geopolymer (FAGP) repair mortar under laboratory-simulated sewer conditions by exposing it to varying concentrations of sulphuric acid (pH 0.5, 1, and 4) for extended durations. The corrosion of the mortar samples was assessed based on visual changes, mass loss, residual mechanical strength, pore evolution, and ion transport over three exposure durations. Comparative analysis with OPC counterparts served as a benchmark. The degradation of FAGP and OPC due to acid exposure appears to escalate with both acid concentration and exposure. However, FAGP displayed superior performance by maintaining their shape and retaining approximately 30% of mechanical strength even after 3000 h of exposure under highly aggressive sewer conditions at pH 0.5. In contrast, OPC fails to endure acid exposure beyond 2000 h. The loss of matrix integrity primarily stems from ion leaching, supported by Scanning Electron Microscopy and Mercury Intrusion Porosimetry analysis, which revealed the creation of intrinsic pores facilitating the ingress of sulphate ions into the matrix. X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy patterns indicate no significant phase alterations, confirming this phenomenon. In conclusion, this study demonstrated that FAGP mortar is more resilient and durable in mild to aggressive sewer conditions than OPC.
{"title":"Degradation mechanisms of low-calcium fly ash-based geopolymer mortar in simulated aggressive sewer conditions","authors":"Piumika W. Ariyadasa , Allan C. Manalo , Weena Lokuge , Vasantha Aravienthan , Andreas Gerdes , Jonas Kaltenbach","doi":"10.1016/j.cemconres.2025.107882","DOIUrl":"10.1016/j.cemconres.2025.107882","url":null,"abstract":"<div><div>Alkali-activated geopolymers are increasingly studied as alternatives to Ordinary Portland Cement (OPC) concrete for use in challenging service environments. Low-calcium geopolymers have been advocated to mitigate Microbial-Induced Concrete Corrosion (MICC) in sewer pipes; however, their broader acceptance as a repair material for sewer rehabilitation remains to be established. This study evaluated the degradation mechanism of low-calcium fly ash-based geopolymer (FAGP) repair mortar under laboratory-simulated sewer conditions by exposing it to varying concentrations of sulphuric acid (pH 0.5, 1, and 4) for extended durations. The corrosion of the mortar samples was assessed based on visual changes, mass loss, residual mechanical strength, pore evolution, and ion transport over three exposure durations. Comparative analysis with OPC counterparts served as a benchmark. The degradation of FAGP and OPC due to acid exposure appears to escalate with both acid concentration and exposure. However, FAGP displayed superior performance by maintaining their shape and retaining approximately 30% of mechanical strength even after 3000 h of exposure under highly aggressive sewer conditions at pH 0.5. In contrast, OPC fails to endure acid exposure beyond 2000 h. The loss of matrix integrity primarily stems from ion leaching, supported by Scanning Electron Microscopy and Mercury Intrusion Porosimetry analysis, which revealed the creation of intrinsic pores facilitating the ingress of sulphate ions into the matrix. X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy patterns indicate no significant phase alterations, confirming this phenomenon. In conclusion, this study demonstrated that FAGP mortar is more resilient and durable in mild to aggressive sewer conditions than OPC.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"194 ","pages":"Article 107882"},"PeriodicalIF":10.9,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143725578","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 : 2025-03-25DOI: 10.1016/j.cemconres.2025.107879
Ziyu Chen , Tian Zhang , Yuxiang Wu , Ian Madsen , Jisheng Ma , Kwesi Sagoe-Crentsil , Adrian Neild , Wenhui Duan
The carbonation of cementitious calcium silicates, specifically tricalcium silicate (C₃S) and dicalcium silicate (C₂S), is crucial for Carbon Capture and Utilization (CCU) in reducing CO₂ emissions in the cement and concrete industry. Controlling these reactions, including the rate and phase evolution necessary for producing desirable carbonated products, poses significant challenges. A lack of continuous kinetic data has impeded the understanding of the mechanisms behind carbonation and its optimization to enhance efficiency. This study explores the effects of four amino acids—glycine, L-arginine, sarcosine, and l-serine—on the carbonation of calcium silicate using in-situ XRD for real-time data collection. It identified a three-stage carbonation process starting with an induction period. The presence of specific amino acids encouraged the formation of stable vaterite and denser microstructures, indicating their potential to enhance the mechanical properties and durability of cementitious materials.
{"title":"In-situ XRD study of the effects of amino acids on the carbonation kinetics of cementitious calcium silicates","authors":"Ziyu Chen , Tian Zhang , Yuxiang Wu , Ian Madsen , Jisheng Ma , Kwesi Sagoe-Crentsil , Adrian Neild , Wenhui Duan","doi":"10.1016/j.cemconres.2025.107879","DOIUrl":"10.1016/j.cemconres.2025.107879","url":null,"abstract":"<div><div>The carbonation of cementitious calcium silicates, specifically tricalcium silicate (C₃S) and dicalcium silicate (C₂S), is crucial for Carbon Capture and Utilization (CCU) in reducing CO₂ emissions in the cement and concrete industry. Controlling these reactions, including the rate and phase evolution necessary for producing desirable carbonated products, poses significant challenges. A lack of continuous kinetic data has impeded the understanding of the mechanisms behind carbonation and its optimization to enhance efficiency. This study explores the effects of four amino acids—glycine, L-arginine, sarcosine, and <span>l</span>-serine—on the carbonation of calcium silicate using in-situ XRD for real-time data collection. It identified a three-stage carbonation process starting with an induction period. The presence of specific amino acids encouraged the formation of stable vaterite and denser microstructures, indicating their potential to enhance the mechanical properties and durability of cementitious materials.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107879"},"PeriodicalIF":10.9,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143688027","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 : 2025-03-25DOI: 10.1016/j.cemconres.2025.107875
Lei Wu , Jin Zhong , Zhe Sun , Yan Cao
This study explores the regulatory mechanisms of trace calcium phosphate (CaP) in the hydration of Portland cement. The results indicate that incorporating 0.001 wt% CaP extends the induction period by forming a passivation film while simultaneously accelerating the hydration rate during the acceleration phase as a nucleation agent, thereby improving hydration efficiency and uniformity. CaP enhances the polymerization degree and homogeneity of C-S-H gel. It modulates the formation and distribution of Ca(OH)₂, facilitating a controlled transition of the crystal structure from a chain-like configuration to layered or network-like forms, thereby enhancing stability. Furthermore, this study highlights the distinct roles of CaP in fresh and aged cement systems and proposes a multi-scale mechanism for complex hydration processes. These findings offer valuable theoretical insights and practical guidance for applying CaP in cementitious materials.
{"title":"Dual dynamic regulation mechanism of trace calcium phosphate on hydration of cementitious materials and optimization of pore structure","authors":"Lei Wu , Jin Zhong , Zhe Sun , Yan Cao","doi":"10.1016/j.cemconres.2025.107875","DOIUrl":"10.1016/j.cemconres.2025.107875","url":null,"abstract":"<div><div>This study explores the regulatory mechanisms of trace calcium phosphate (CaP) in the hydration of Portland cement. The results indicate that incorporating 0.001 wt% CaP extends the induction period by forming a passivation film while simultaneously accelerating the hydration rate during the acceleration phase as a nucleation agent, thereby improving hydration efficiency and uniformity. CaP enhances the polymerization degree and homogeneity of C-S-H gel. It modulates the formation and distribution of Ca(OH)₂, facilitating a controlled transition of the crystal structure from a chain-like configuration to layered or network-like forms, thereby enhancing stability. Furthermore, this study highlights the distinct roles of CaP in fresh and aged cement systems and proposes a multi-scale mechanism for complex hydration processes. These findings offer valuable theoretical insights and practical guidance for applying CaP in cementitious materials.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107875"},"PeriodicalIF":10.9,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143687951","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 : 2025-03-25DOI: 10.1016/j.cemconres.2025.107880
Hui Xie , Xin Liu , Haochuan Wang , Zhenqi Yu , Lijing Shao , Wei Wang , Jinxiang Hong , Chong Wang , Pan Feng
The use of aluminum sulfate (Al2(SO4)3)-based alkali-free accelerators in shotcrete often impeded tricalcium silicate (C3S) hydration, leading to poor ultra-early strength development. To address this, a novel stage-wise kinetic control strategy was proposed to regulate the sequential formation of ettringite and C-S-H gel through the delayed addition of C-S-H nano seeds. The dosage of C-S-H nano seeds, delayed time, addition sequence of Al2(SO4)3 and C-S-H nano seeds were carefully examined in this study, and the effects of addition sequence on the hydration kinetic, hydration products, and pore structure of cement pastes were systematically investigated. Results demonstrated a significant enhancement in 6 h compressive strength, achieving a 35% increase when C-S-H nano seeds (4% dosage) were added 1 h after initial mixing compared to simultaneous addition. Hydration heat, XRD, TG, SEM, and BSE-EDS analyses revealed that the delayed addition promoted C3S hydration at later stages by staggering intensive ettringite formation and C-S-H gel precipitation, mitigating competition for calcium ions. This stage-wise approach facilitated C-S-H gel integration into the pre-constructed porous ettringite skeleton, refining the pore structure and enhancing ultra-early mechanical performance. These findings highlight an effective strategy to optimize hydration kinetics and strength development in shotcrete applications.
{"title":"Novel strategies for ultra-early strengthening of shotcrete: Stage-wise kinetic control of hydration products","authors":"Hui Xie , Xin Liu , Haochuan Wang , Zhenqi Yu , Lijing Shao , Wei Wang , Jinxiang Hong , Chong Wang , Pan Feng","doi":"10.1016/j.cemconres.2025.107880","DOIUrl":"10.1016/j.cemconres.2025.107880","url":null,"abstract":"<div><div>The use of aluminum sulfate (Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>)-based alkali-free accelerators in shotcrete often impeded tricalcium silicate (C<sub>3</sub>S) hydration, leading to poor ultra-early strength development. To address this, a novel stage-wise kinetic control strategy was proposed to regulate the sequential formation of ettringite and C-S-H gel through the delayed addition of C-S-H nano seeds. The dosage of C-S-H nano seeds, delayed time, addition sequence of Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> and C-S-H nano seeds were carefully examined in this study, and the effects of addition sequence on the hydration kinetic, hydration products, and pore structure of cement pastes were systematically investigated. Results demonstrated a significant enhancement in 6 h compressive strength, achieving a 35% increase when C-S-H nano seeds (4% dosage) were added 1 h after initial mixing compared to simultaneous addition. Hydration heat, XRD, TG, SEM, and BSE-EDS analyses revealed that the delayed addition promoted C<sub>3</sub>S hydration at later stages by staggering intensive ettringite formation and C-S-H gel precipitation, mitigating competition for calcium ions. This stage-wise approach facilitated C-S-H gel integration into the pre-constructed porous ettringite skeleton, refining the pore structure and enhancing ultra-early mechanical performance. These findings highlight an effective strategy to optimize hydration kinetics and strength development in shotcrete applications.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107880"},"PeriodicalIF":10.9,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697332","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 : 2025-03-23DOI: 10.1016/j.cemconres.2025.107878
Syrine Razki , Farid Benboudjema , Alexandra Bourdot , Sylvain Langlois , Amélie Fau , Fikri Hafid , Tulio Honorio
Establishing direct relations between alkali-silica reaction (ASR) expansion, crystallization pressure build-up, and phase assemblage changes is a critical step towards predictive modeling of ASR damage. To address this, we propose a strategy that combines thermodynamic modeling with micromechanics. First, we complete the thermodynamic database for ASR products, including nanocrystalline ASR-P1 data and improving the previous data for crystalline products. Phase assemblage is determined by accounting for cement hydration and amorphous silica dissolution kinetics. Crystallization pressure estimates are provided based on pore solution supersaturation with respect to ASR products. These phase assemblage and crystallization pressure estimates are then used as input for analytical micromechanical estimates of elastic properties degradation and macroscopic expansion. The model strategy that integrates damage considerations and the gel-like nature of ASR-P1 provides a better comparison with experimental results.
{"title":"Crystallization pressure in ASR expansion quantified by thermodynamic modeling and micromechanics","authors":"Syrine Razki , Farid Benboudjema , Alexandra Bourdot , Sylvain Langlois , Amélie Fau , Fikri Hafid , Tulio Honorio","doi":"10.1016/j.cemconres.2025.107878","DOIUrl":"10.1016/j.cemconres.2025.107878","url":null,"abstract":"<div><div>Establishing direct relations between alkali-silica reaction (ASR) expansion, crystallization pressure build-up, and phase assemblage changes is a critical step towards predictive modeling of ASR damage. To address this, we propose a strategy that combines thermodynamic modeling with micromechanics. First, we complete the thermodynamic database for ASR products, including nanocrystalline ASR-P1 data and improving the previous data for crystalline products. Phase assemblage is determined by accounting for cement hydration and amorphous silica dissolution kinetics. Crystallization pressure estimates are provided based on pore solution supersaturation with respect to ASR products. These phase assemblage and crystallization pressure estimates are then used as input for analytical micromechanical estimates of elastic properties degradation and macroscopic expansion. The model strategy that integrates damage considerations and the gel-like nature of ASR-P1 provides a better comparison with experimental results.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107878"},"PeriodicalIF":10.9,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143675499","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 : 2025-03-21DOI: 10.1016/j.cemconres.2025.107869
Michal Hlobil, Luca Michel, Mohit Pundir, David S. Kammer
Cold joints in extruded concrete structures form once the exposed surface of a deposited filament dries prematurely and gets sequentially covered by a layer of fresh concrete. This creates a material heterogeneity which lowers the structural durability and shortens the designed service life. Many factors concurrently affect cold joint formation, yet a suitable tool for their categorization is missing. Here, we present a computational model that simulates the drying kinetics at the exposed structural surface, accounting for cement hydration and the resulting microstructural development. The model provides a time estimate for cold joint formation as a result. It allows us to assess the drying severity for a given geometry of the structure, its interaction with the environment, and ambient conditions. We evaluate the assessed factors and provide generalized recommendations for cold joint mitigation.
{"title":"A thermo-hygro model to determine the factors dictating cold joint formation in 3D printed concrete","authors":"Michal Hlobil, Luca Michel, Mohit Pundir, David S. Kammer","doi":"10.1016/j.cemconres.2025.107869","DOIUrl":"10.1016/j.cemconres.2025.107869","url":null,"abstract":"<div><div>Cold joints in extruded concrete structures form once the exposed surface of a deposited filament dries prematurely and gets sequentially covered by a layer of fresh concrete. This creates a material heterogeneity which lowers the structural durability and shortens the designed service life. Many factors concurrently affect cold joint formation, yet a suitable tool for their categorization is missing. Here, we present a computational model that simulates the drying kinetics at the exposed structural surface, accounting for cement hydration and the resulting microstructural development. The model provides a time estimate for cold joint formation as a result. It allows us to assess the drying severity for a given geometry of the structure, its interaction with the environment, and ambient conditions. We evaluate the assessed factors and provide generalized recommendations for cold joint mitigation.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107869"},"PeriodicalIF":10.9,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143666463","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}
Ettringite forms directly after Portland cement is mixed with water. Polycarboxylate ether-type superplasticizers can stabilize nano-ettringite particles in the pore solution and modify ettringite formation. It was previously impossible to isolate the nano-ettringite from the cement pore solution at commonly used water-to-cement (w/c) ratios of 0.5 and lower. Therefore, the exact morphology of ettringite in the pore solution has not been systematically studied. This paper presents a novel method for obtaining nano-ettringite from cement paste by centrifugation with a high-density liquid. Ettringite was isolated at three different water-to-cement ratios (0.3, 0.4, and 0.5) and four dosages of a polycarboxylate ether-type superplasticizer (0.05%, 0.1%, 0.25%, and 0.4%). The size and morphology of the obtained ettringite particles were analyzed using transmission electron microscopy (TEM). The chemical composition and structure of ettringite were confirmed using electron energy loss spectroscopy, high-resolution TEM imaging, and X-ray diffraction. The ettringite particle size decreases as the superplasticizer dosage increases. As a result, the specific surface area at higher superplasticizer dosages increases from 39 m2 g−1 to 58 m2 g−1. In-situ calorimetry was used to measure the initial heat release and estimate the amount of ettringite formed. Since the initial heat did not change significantly with varying superplasticizer dosages, it suggests that the studied superplasticizer has a minor influence on the amount of ettringite at the considered concentrations. In summary, cement paste centrifugation using a high-density fluid allows the isolation of superplasticizer-stabilized nano-ettringite from cement paste. The method could be valuable for other studies dealing with the impact of ettringite morphology.
波特兰水泥与水混合后会直接形成闪长岩。聚羧酸醚类超塑化剂可以稳定孔隙溶液中的纳米闪长岩颗粒，并改变闪长岩的形成。以前，当常用的水灰比（w/c）为 0.5 或更低时，无法从水泥孔隙溶液中分离出纳米铁素体。因此，孔隙溶液中埃特林岩的确切形态尚未得到系统研究。本文介绍了一种通过高密度液体离心从水泥浆中获得纳米埃曲沸石的新方法。在三种不同的水灰比（0.3、0.4 和 0.5）和四种聚羧酸醚型超塑化剂用量（0.05%、0.1%、0.25% 和 0.4%）条件下分离出了埃丁石。利用透射电子显微镜（TEM）分析了所获得的乙曲石颗粒的尺寸和形态。利用电子能量损失光谱、高分辨率 TEM 成像和 X 射线衍射确认了埃曲沸石的化学成分和结构。随着超塑化剂用量的增加，埃曲沸石的粒径减小。因此，在较高的超塑化剂用量下，比表面积从 39 m2 g-1 增加到 58 m2 g-1。采用原位量热法测量初始放热量，并估算形成的乙丁睛石量。由于初始热量并没有随着超塑化剂用量的变化而发生显著变化，这表明所研究的超塑化剂在所考虑的浓度下对乙曲石的数量影响较小。总之，使用高密度流体对水泥浆进行离心分离，可以从水泥浆中分离出超塑化剂稳定的纳米乙丁睛石。这种方法对于其他涉及乙丁睛石形态影响的研究很有价值。
{"title":"Revealing the morphology of nano-ettringite in cement paste: A TEM study on the influence of polycarboxylate ether superplasticizers","authors":"Olivia Rindle , Florian Sixt , Liam Spillane , Elena Willinger , Torben Gädt","doi":"10.1016/j.cemconres.2025.107853","DOIUrl":"10.1016/j.cemconres.2025.107853","url":null,"abstract":"<div><div>Ettringite forms directly after Portland cement is mixed with water. Polycarboxylate ether-type superplasticizers can stabilize nano-ettringite particles in the pore solution and modify ettringite formation. It was previously impossible to isolate the nano-ettringite from the cement pore solution at commonly used water-to-cement (w/c) ratios of 0.5 and lower. Therefore, the exact morphology of ettringite in the pore solution has not been systematically studied. This paper presents a novel method for obtaining nano-ettringite from cement paste by centrifugation with a high-density liquid. Ettringite was isolated at three different water-to-cement ratios (0.3, 0.4, and 0.5) and four dosages of a polycarboxylate ether-type superplasticizer (0.05%, 0.1%, 0.25%, and 0.4%). The size and morphology of the obtained ettringite particles were analyzed using transmission electron microscopy (TEM). The chemical composition and structure of ettringite were confirmed using electron energy loss spectroscopy, high-resolution TEM imaging, and X-ray diffraction. The ettringite particle size decreases as the superplasticizer dosage increases. As a result, the specific surface area at higher superplasticizer dosages increases from 39<!--> <!-->m<sup>2</sup> <!-->g<sup>−1</sup> to 58<!--> <!-->m<sup>2</sup> <!-->g<sup>−1</sup>. In-situ calorimetry was used to measure the initial heat release and estimate the amount of ettringite formed. Since the initial heat did not change significantly with varying superplasticizer dosages, it suggests that the studied superplasticizer has a minor influence on the amount of ettringite at the considered concentrations. In summary, cement paste centrifugation using a high-density fluid allows the isolation of superplasticizer-stabilized nano-ettringite from cement paste. The method could be valuable for other studies dealing with the impact of ettringite morphology.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"193 ","pages":"Article 107853"},"PeriodicalIF":10.9,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号