Cement-based materials are considered for sealing plugs in deep geological disposal of radioactive waste. Ensuring their long-term durability is critical for safety over millennia. The Roman Concrete (RoC) project uses ancient Roman underwater concretes as analogues to validate reactive transport models for long-term ageing. This study focuses on hydration mechanisms in Roman concrete made with Phlegrean pozzolan, slaked lime, and seawater. Various techniques (XRD, SEM-EDS, NMR, nanoindentation, microtomography, ICP-OES, ion chromatography) were used to characterize hydration products. Casting underwater led to aragonite and brucite layers with a 60 GPa Young's modulus, protecting the concrete from further degradation. In the core, pozzolanic reactions produce C-(A)-S-H phases (Ca/Si = 1.2; Al/Si = 0.2) with a modulus of 12 GPa. HYTEC modeling confirmed the mechanism: incongruent pozzolan dissolution releases ions (K+, SiO₄4−, Al3+, Na+), promoting C-(A)-S-H formation and portlandite consumption.
在放射性废物的深部地质处置中，考虑使用水泥基材料作为密封塞。确保它们的长期耐用性对几千年的安全至关重要。罗马混凝土（RoC）项目使用古罗马水下混凝土作为模拟物来验证长期老化的反应传输模型。本研究的重点是罗马混凝土的水化机制，由Phlegrean火山灰，熟石灰和海水制成。采用XRD、SEM-EDS、NMR、纳米压痕、微层析成像、ICP-OES、离子色谱等技术对水化产物进行表征。水下浇筑产生了文石和水镁石层，杨氏模量为60 GPa，保护混凝土免受进一步降解。在岩心中，火山灰反应生成C-(A)- s - h相（Ca/Si = 1.2; Al/Si = 0.2），模量为12 GPa。HYTEC模型证实了其机理：不一致的火山灰溶解释放离子（K+, SiO₄4−,Al3+, Na+），促进C-(A)- s - h的形成和硅酸盐的消耗。
{"title":"Hydration mechanisms in Roman seawater concrete: Archaeological analogue for validation of long-term ageing reactive transport model","authors":"Fructueux Jesugnon Sohounme , Mejdi Neji , Nicolas Seigneur , Katia Schörle , Arnaud Coutelas , T. Charpentier , Mélanie Moskura , Cyrielle Jardin , Alexandre Dauzères","doi":"10.1016/j.cemconres.2025.108114","DOIUrl":"10.1016/j.cemconres.2025.108114","url":null,"abstract":"<div><div>Cement-based materials are considered for sealing plugs in deep geological disposal of radioactive waste. Ensuring their long-term durability is critical for safety over millennia. The Roman Concrete (RoC) project uses ancient Roman underwater concretes as analogues to validate reactive transport models for long-term ageing. This study focuses on hydration mechanisms in Roman concrete made with Phlegrean pozzolan, slaked lime, and seawater. Various techniques (XRD, SEM-EDS, NMR, nanoindentation, microtomography, ICP-OES, ion chromatography) were used to characterize hydration products. Casting underwater led to aragonite and brucite layers with a 60 GPa Young's modulus, protecting the concrete from further degradation. In the core, pozzolanic reactions produce C-(A)-S-H phases (Ca/Si = 1.2; Al/Si = 0.2) with a modulus of 12 GPa. HYTEC modeling confirmed the mechanism: incongruent pozzolan dissolution releases ions (K<sup>+</sup>, SiO₄<sup>4−</sup>, Al<sup>3+</sup>, Na<sup>+</sup>), promoting C-(A)-S-H formation and portlandite consumption.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"201 ","pages":"Article 108114"},"PeriodicalIF":13.1,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748695","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 : 2025-12-09DOI: 10.1016/j.cemconres.2025.108101
Thomas Bernard , William Wilson
The chloride penetration rate in a cementitious system characterizes its ability to resist chloride-induced corrosion. Assessing this property involves determining a diffusion coefficient obtained from diffusion or migration tests, or from models. The evolution of penetration depth can be used to predict the durability of a cementitious system, as it follows a linear relationship with the square root of time, known as the square root law. However, given the many assumptions behind this law, it remains unclear when and how it can be used to predict future penetration depths. This study investigates the applicability of the law for seven binders and shows that it can be used to monitor the evolution of penetration depth before the stabilization of the properties of the specimen, except when glass powder is used. However, predicting future penetration depths is more accurate when both the microstructure and surface content are stable.
{"title":"Square-root law prediction of chloride penetration rates in stabilized cement pastes","authors":"Thomas Bernard , William Wilson","doi":"10.1016/j.cemconres.2025.108101","DOIUrl":"10.1016/j.cemconres.2025.108101","url":null,"abstract":"<div><div>The chloride penetration rate in a cementitious system characterizes its ability to resist chloride-induced corrosion. Assessing this property involves determining a diffusion coefficient obtained from diffusion or migration tests, or from models. The evolution of penetration depth can be used to predict the durability of a cementitious system, as it follows a linear relationship with the square root of time, known as the square root law. However, given the many assumptions behind this law, it remains unclear when and how it can be used to predict future penetration depths. This study investigates the applicability of the law for seven binders and shows that it can be used to monitor the evolution of penetration depth before the stabilization of the properties of the specimen, except when glass powder is used. However, predicting future penetration depths is more accurate when both the microstructure and surface content are stable.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"201 ","pages":"Article 108101"},"PeriodicalIF":13.1,"publicationDate":"2025-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748696","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 : 2025-12-05DOI: 10.1016/j.cemconres.2025.108097
Jiaxing Ban , Barbara Lothenbach , John L. Provis , George Dan Miron , Zeyu Zhou , Dengquan Wang , Sergey V. Churakov , Bin Ma
Hydrotalcite-group layered double hydroxide (LDH) phases are important in many technical and geological contexts, and in applications ranging from environmental processes to catalysts to cements. This study systematically investigates the roles of Fe in LDH structures across varying pH conditions relevant to concrete environments, combining laboratory-based characterization, synchrotron-based techniques, and thermodynamic modeling. Elevated pH enhances Fe incorporation into the LDH phase, while suppressing ferrihydrite formation. At pH > 11, partial LDH dissolution is observed. Thermodynamic modeling and diffractometry reveal the transformation mechanism: control of the initial pH increases promotes Al(III) and Fe(III) uptake into LDH structures, while further alkalinization (pH > 11) triggers selective Al(III) dissolution, thereby increasing the M2+/M3+ ratio and altering unit cell parameters. These findings elucidate the dynamics between Fe(III) incorporation in LDH and ferrihydrite precipitation, governed by pH-dependent solubility and charge-balance constraints.
{"title":"Examining the pH dependence of Fe behavior in hydrotalcite-group structures","authors":"Jiaxing Ban , Barbara Lothenbach , John L. Provis , George Dan Miron , Zeyu Zhou , Dengquan Wang , Sergey V. Churakov , Bin Ma","doi":"10.1016/j.cemconres.2025.108097","DOIUrl":"10.1016/j.cemconres.2025.108097","url":null,"abstract":"<div><div>Hydrotalcite-group layered double hydroxide (LDH) phases are important in many technical and geological contexts, and in applications ranging from environmental processes to catalysts to cements. This study systematically investigates the roles of Fe in LDH structures across varying pH conditions relevant to concrete environments, combining laboratory-based characterization, synchrotron-based techniques, and thermodynamic modeling. Elevated pH enhances Fe incorporation into the LDH phase, while suppressing ferrihydrite formation. At pH > 11, partial LDH dissolution is observed. Thermodynamic modeling and diffractometry reveal the transformation mechanism: control of the initial pH increases promotes Al(III) and Fe(III) uptake into LDH structures, while further alkalinization (pH > 11) triggers selective Al(III) dissolution, thereby increasing the M<sup>2+</sup>/M<sup>3+</sup> ratio and altering unit cell parameters. These findings elucidate the dynamics between Fe(III) incorporation in LDH and ferrihydrite precipitation, governed by pH-dependent solubility and charge-balance constraints.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"201 ","pages":"Article 108097"},"PeriodicalIF":13.1,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145689792","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 : 2025-12-03DOI: 10.1016/j.cemconres.2025.108099
Qiaomu Zheng , En-Hua Yang , Chen Li , Qiang Ren , Hongen Zhang , Wenting Li , Sifan Zhang , Zhengwu Jiang
Enhancing the toughness gain of ultra-high performance fiber-reinforced concrete (UHPFRC) through fundamental unit (e.g., nanostructure) optimization remains a challenge. This work explores the multi-scale mechanical behaviors of UHPFRC under four-point flexural loads, incorporating silica fume (SF) and ultra-fine fly ash (UFFA) as the ultra-fine mineral additives. SF and UFFA promote the formation of C(A)SH with high Si/Ca and Al/Ca ratio, altering the structural characteristics of both cement matrix and fiber-matrix interface. At the nanoscale, SF enhances the C(A)SH modulus through higher cohesion force, while UFFA elevates its friction coefficient; although both additives decrease C(A)SH hardness by reduced intrinsic modulus, their synergism improves C(A)SH stiffness. At the micro/macroscale, the stiffness of cement matrix and modulus of fiber-matrix interface dominate the strain-hardening behavior before fiber debonding, whereas the stiffness and friction coefficient of interface control the strain-softening process during fiber pulling-out. These insights highlight the hierarchical pathway to toughness modulation in UHPFRC.
{"title":"Multi-scale mechanical behaviors of ultra-high performance fiber-reinforced concrete influenced by ultra-fine mineral additives: A hierarchical perspective on toughness gain modulation","authors":"Qiaomu Zheng , En-Hua Yang , Chen Li , Qiang Ren , Hongen Zhang , Wenting Li , Sifan Zhang , Zhengwu Jiang","doi":"10.1016/j.cemconres.2025.108099","DOIUrl":"10.1016/j.cemconres.2025.108099","url":null,"abstract":"<div><div>Enhancing the toughness gain of ultra-high performance fiber-reinforced concrete (UHPFRC) through fundamental unit (e.g., nanostructure) optimization remains a challenge. This work explores the multi-scale mechanical behaviors of UHPFRC under four-point flexural loads, incorporating silica fume (SF) and ultra-fine fly ash (UFFA) as the ultra-fine mineral additives. SF and UFFA promote the formation of C(<em>A</em>)SH with high Si/Ca and Al/Ca ratio, altering the structural characteristics of both cement matrix and fiber-matrix interface. At the nanoscale, SF enhances the C(<em>A</em>)SH modulus through higher cohesion force, while UFFA elevates its friction coefficient; although both additives decrease C(<em>A</em>)SH hardness by reduced intrinsic modulus, their synergism improves C(<em>A</em>)SH stiffness. At the micro/macroscale, the stiffness of cement matrix and modulus of fiber-matrix interface dominate the strain-hardening behavior before fiber debonding, whereas the stiffness and friction coefficient of interface control the strain-softening process during fiber pulling-out. These insights highlight the hierarchical pathway to toughness modulation in UHPFRC.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"201 ","pages":"Article 108099"},"PeriodicalIF":13.1,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145673801","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 : 2025-12-02DOI: 10.1016/j.cemconres.2025.108098
Charlotte Dewitte , Mateusz Wyrzykowski , Ellina Bernard
MgO-based cements represent a promising, low-CO2 alternative to traditional Portland cement. In magnesium silicate cements, M-S-H is the main phase. Although the thermodynamic properties and hydration mechanisms of this phase have been investigated, studies on its mechanical behaviour remain limited. This study aimed to determine the factors influencing the micro-mechanical properties of the MgO-SiO2 pastes. Detailed chemical (X-ray diffraction, Thermogravimetric analysis, Energy-dispersive spectrometry analysis), microstructural (water porosity), and mechanical (indentation) analyses were conducted. The source of raw materials and the production protocol (mortar mixer, ball mill, pressing) influence the mineralogy of pastes and silicon distribution. Additives have a moderate impact on the mineralogy of pastes. Samples with the lowest porosity exhibit the highest elastic properties. Once the effect of porosity is accounted for, a higher brucite content correlates with increased elastic properties.
{"title":"Factors influencing the micro-mechanical properties of MgO-SiO2 pastes","authors":"Charlotte Dewitte , Mateusz Wyrzykowski , Ellina Bernard","doi":"10.1016/j.cemconres.2025.108098","DOIUrl":"10.1016/j.cemconres.2025.108098","url":null,"abstract":"<div><div>MgO-based cements represent a promising, low-CO<sub>2</sub> alternative to traditional Portland cement. In magnesium silicate cements, M-S-H is the main phase. Although the thermodynamic properties and hydration mechanisms of this phase have been investigated, studies on its mechanical behaviour remain limited. This study aimed to determine the factors influencing the micro-mechanical properties of the MgO-SiO<sub>2</sub> pastes. Detailed chemical (X-ray diffraction, Thermogravimetric analysis, Energy-dispersive spectrometry analysis), microstructural (water porosity), and mechanical (indentation) analyses were conducted. The source of raw materials and the production protocol (mortar mixer, ball mill, pressing) influence the mineralogy of pastes and silicon distribution. Additives have a moderate impact on the mineralogy of pastes. Samples with the lowest porosity exhibit the highest elastic properties. Once the effect of porosity is accounted for, a higher brucite content correlates with increased elastic properties.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"201 ","pages":"Article 108098"},"PeriodicalIF":13.1,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645794","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 : 2025-12-01DOI: 10.1016/j.cemconres.2025.108094
Jiaxin Liao , Jian Liu , Haocheng Zhao , Xiangming Kong , Zhongzhou Xu , Puyu Zhou
Shotcrete often exhibits lower strength after several days despite its rapid setting, primarily because accelerators interfere with cement hydration and microstructure development. This study investigates the effects of two typical accelerators—aluminium sulphate (AS) and sodium aluminate (NA)—on setting behaviour and early strength of cementitious materials. Isothermal calorimetry, XRD, and TGA were employed to characterize the hydration process, while low-field NMR (LF-NMR) was used to monitor pore structure evolution. The results show that increasing dosages of AS and NA proportionally reduces setting time while increasing the 12-h strength of cement mortars. At equivalent aluminium contents, NA is more effective than AS in setting acceleration. Within 3 days of curing, the mortars with AS exhibit consistently higher strength than the reference, whereas those with NA demonstrate the opposite comparison, although both AS and NA visibly accelerate C₃S hydration. AS promotes ettringite formation, while NA favours AFm and calcium aluminate hydrates. Based on the influence of porosity on strength, the pores measured by LF-NMR in hardened cement pastes (HCPs) are categorized as harmless pores including interlayer and gel pores of C–S–H, and harmful pores including interhydrate and capillary pores. AS decreases both total and harmful porosity in HCPs while increasing harmless porosity. In contrast, NA shows opposite trend, with total porosity remaining approximately unchanged. A semi-empirical model correlating mortar strength with harmless and harmful porosity is proposed to account for the effects of pore filling, interparticle binding of hydration products, and pore size distribution of HCPs on strength development.
{"title":"Quantitative correlation of cement hydration, pore structure evolution and strength development of cement pastes with accelerators","authors":"Jiaxin Liao , Jian Liu , Haocheng Zhao , Xiangming Kong , Zhongzhou Xu , Puyu Zhou","doi":"10.1016/j.cemconres.2025.108094","DOIUrl":"10.1016/j.cemconres.2025.108094","url":null,"abstract":"<div><div>Shotcrete often exhibits lower strength after several days despite its rapid setting, primarily because accelerators interfere with cement hydration and microstructure development. This study investigates the effects of two typical accelerators—aluminium sulphate (AS) and sodium aluminate (NA)—on setting behaviour and early strength of cementitious materials. Isothermal calorimetry, XRD, and TGA were employed to characterize the hydration process, while low-field NMR (LF-NMR) was used to monitor pore structure evolution. The results show that increasing dosages of AS and NA proportionally reduces setting time while increasing the 12-h strength of cement mortars. At equivalent aluminium contents, NA is more effective than AS in setting acceleration. Within 3 days of curing, the mortars with AS exhibit consistently higher strength than the reference, whereas those with NA demonstrate the opposite comparison, although both AS and NA visibly accelerate C₃S hydration. AS promotes ettringite formation, while NA favours AFm and calcium aluminate hydrates. Based on the influence of porosity on strength, the pores measured by LF-NMR in hardened cement pastes (HCPs) are categorized as harmless pores including interlayer and gel pores of C–S–H, and harmful pores including interhydrate and capillary pores. AS decreases both total and harmful porosity in HCPs while increasing harmless porosity. In contrast, NA shows opposite trend, with total porosity remaining approximately unchanged. A semi-empirical model correlating mortar strength with harmless and harmful porosity is proposed to account for the effects of pore filling, interparticle binding of hydration products, and pore size distribution of HCPs on strength development.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"200 ","pages":"Article 108094"},"PeriodicalIF":13.1,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645310","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 : 2025-11-30DOI: 10.1016/j.cemconres.2025.108100
Zihan Ma , Yi Jiang , Shunmin Xiao , Xiao Zhang , Qinglong Qin , Jiangshan Li , Peiliang Shen , Chi-Sun Poon
This study systematically investigates the enforced carbonation behavior of tricalcium aluminate (C3A) across a precisely controlled pH range of 5.8–12.5. The results indicate that C3A carbonation is thermodynamically spontaneous; its overall rate, reaction pathway, and phase assemblage are significantly influenced by solution pH. The accumulation rate of calcium carbonate (Cc) increases sharply below pH 11.0 and peaks at pH 9.5–10.0, where only 4.1 wt% of the initial C3A remains after 10 min of carbonation. Phase analysis reveals a distinct pH-dependent transition: CO32−-AFm dominates when pH > 11.0, whereas Cc is the primary product when pH < 11.0. Mechanistically, pH governs C3A carbonation via three coupled effects: (i) by modulating Al dissolution, it alters the aqueous Ca/Al ratio, thereby adjusting the relative supersaturation of Cc and CO32−-AFm; (ii) it determines the precipitation threshold of Al(OH)3, enabling dissolved Al(OH)4− to react with nascent Cc and form CO32−-AFm; and (iii) at pH < 6, an Al-rich amorphous film rapidly forms on the surface, effectively halting further carbonation. These findings enhance our understanding of aluminate carbonation mechanisms in cementitious systems and provide insights into tailoring pH to optimize CO2 uptake in cement.
{"title":"pH-Dependent carbonation behavior of tricalcium aluminate","authors":"Zihan Ma , Yi Jiang , Shunmin Xiao , Xiao Zhang , Qinglong Qin , Jiangshan Li , Peiliang Shen , Chi-Sun Poon","doi":"10.1016/j.cemconres.2025.108100","DOIUrl":"10.1016/j.cemconres.2025.108100","url":null,"abstract":"<div><div>This study systematically investigates the enforced carbonation behavior of tricalcium aluminate (C<sub>3</sub>A) across a precisely controlled pH range of 5.8–12.5. The results indicate that C<sub>3</sub>A carbonation is thermodynamically spontaneous; its overall rate, reaction pathway, and phase assemblage are significantly influenced by solution pH. The accumulation rate of calcium carbonate (Cc) increases sharply below pH 11.0 and peaks at pH 9.5–10.0, where only 4.1 wt% of the initial C<sub>3</sub>A remains after 10 min of carbonation. Phase analysis reveals a distinct pH-dependent transition: CO<sub>3</sub><sup>2−</sup>-AFm dominates when pH > 11.0, whereas Cc is the primary product when pH < 11.0. Mechanistically, pH governs C<sub>3</sub>A carbonation via three coupled effects: (i) by modulating Al dissolution, it alters the aqueous Ca/Al ratio, thereby adjusting the relative supersaturation of Cc and CO<sub>3</sub><sup>2−</sup>-AFm; (ii) it determines the precipitation threshold of Al(OH)<sub>3</sub>, enabling dissolved Al(OH)<sub>4</sub><sup>−</sup> to react with nascent Cc and form CO<sub>3</sub><sup>2−</sup>-AFm; and (iii) at pH < 6, an Al-rich amorphous film rapidly forms on the surface, effectively halting further carbonation. These findings enhance our understanding of aluminate carbonation mechanisms in cementitious systems and provide insights into tailoring pH to optimize CO<sub>2</sub> uptake in cement.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"200 ","pages":"Article 108100"},"PeriodicalIF":13.1,"publicationDate":"2025-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145619725","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 : 2025-11-29DOI: 10.1016/j.cemconres.2025.108095
Huawei Liu , Yaxin Tao , Chao Zhu , Chao Liu , Yifei Wang , Jiao Yun , Yukun Zhang
3D printed concrete exhibits significant durability issues under freeze–thaw (F–T) conditions due to its unique pore structure, restricting its widespread application in cold regions. In this study, the frost resistance of 3D printed recycled aggregate concrete (3DPRAC) was systematically evaluated at different recycled coarse aggregate (RCA) replacement ratios (0 %, 50 %, and 100 %), and the underlying damage mechanisms induced by F–T cycles were elucidated. Results indicated that the frost resistance of 3DPRAC was notably inferior to cast concrete and further deteriorated nonlinearly with increasing RCA replacement ratios. Ellipsoidal pores within 3DPRAC facilitated ice crystal formation, accelerating crack initiation and propagation. Damage originated from the porous old mortar in RCA and dual interfacial transition zones, while ultimate failure was dominated by a multi-interface and pore structure defect system jointly formed by RCA and printed structure. This research provides theoretical insights for durability design of 3D printed concrete structures in cold-region applications.
{"title":"3D printed concrete with recycled coarse aggregate: Freeze–thaw resistance assessment and damage mechanisms","authors":"Huawei Liu , Yaxin Tao , Chao Zhu , Chao Liu , Yifei Wang , Jiao Yun , Yukun Zhang","doi":"10.1016/j.cemconres.2025.108095","DOIUrl":"10.1016/j.cemconres.2025.108095","url":null,"abstract":"<div><div>3D printed concrete exhibits significant durability issues under freeze–thaw (F–T) conditions due to its unique pore structure, restricting its widespread application in cold regions. In this study, the frost resistance of 3D printed recycled aggregate concrete (3DPRAC) was systematically evaluated at different recycled coarse aggregate (RCA) replacement ratios (0 %, 50 %, and 100 %), and the underlying damage mechanisms induced by F–T cycles were elucidated. Results indicated that the frost resistance of 3DPRAC was notably inferior to cast concrete and further deteriorated nonlinearly with increasing RCA replacement ratios. Ellipsoidal pores within 3DPRAC facilitated ice crystal formation, accelerating crack initiation and propagation. Damage originated from the porous old mortar in RCA and dual interfacial transition zones, while ultimate failure was dominated by a multi-interface and pore structure defect system jointly formed by RCA and printed structure. This research provides theoretical insights for durability design of 3D printed concrete structures in cold-region applications.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"200 ","pages":"Article 108095"},"PeriodicalIF":13.1,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145613721","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 : 2025-11-27DOI: 10.1016/j.cemconres.2025.108096
Xiaobo Niu , Yogarajah Elakneswaran , Ryosuke Kikuchi , Ang Li , Sivasubramaniam Seralathan , Yoshihisa Hiraki , Junya Sato , Takeshi Osugi , Takashi Kamiyama , Brant Walkley
The incorporation of boron (B) as a neutron absorber into metakaolin-based geopolymers for the remediation of radioactive debris following nuclear accidents has attracted considerable attention. In this study, boron carbide (B4C) was employed as a functional filler, while cetyltrimethylammonium bromide (CTAB) acted as both a dispersant and a stabiliser to enhance the neutron shielding properties of metakaolin-based geopolymers. Although the addition of B4C improved processability via a “roller-ball” effect and had no discernible impact on the geopolymerisation process, its weakly polar, negatively charged surface led to the formation of a loose, weak-shell interfacial transition zone (ITZ) between the filler and the matrix, thereby reducing mechanical strength and chemical stability. In contrast, CTAB self-assembled into an interdigitated monolayer on the B4C surface, reversing its surface charge to positive and promoting its uniform dispersion within the matrix. While CTAB slightly inhibited the dissolution of metakaolin, it preferentially interacted with B4C, thereby mitigating the adverse effects on the geopolymerisation process. Moreover, CTAB promoted gelation within the ITZ surrounding B4C, facilitating the development of a dense, potassium-deficient, yet electrostatically stabilised microstructure. This synergistic interaction enhanced interfacial bonding between the filler and the matrix, enabled efficient stress transfer, and significantly improved mechanical performance and chemical stability. Furthermore, the B4C–CTAB-modified geopolymers demonstrated enhanced neutron shielding performance. Overall, this work offers a promising approach for engineering high-performance, multifunctional geopolymer composites for nuclear and environmental applications.
{"title":"Tailoring neutron-shielding boron-metakaolin geopolymers with B4C filler: Surfactant-driven interfacial and microstructural control","authors":"Xiaobo Niu , Yogarajah Elakneswaran , Ryosuke Kikuchi , Ang Li , Sivasubramaniam Seralathan , Yoshihisa Hiraki , Junya Sato , Takeshi Osugi , Takashi Kamiyama , Brant Walkley","doi":"10.1016/j.cemconres.2025.108096","DOIUrl":"10.1016/j.cemconres.2025.108096","url":null,"abstract":"<div><div>The incorporation of boron (B) as a neutron absorber into metakaolin-based geopolymers for the remediation of radioactive debris following nuclear accidents has attracted considerable attention. In this study, boron carbide (B<sub>4</sub>C) was employed as a functional filler, while cetyltrimethylammonium bromide (CTAB) acted as both a dispersant and a stabiliser to enhance the neutron shielding properties of metakaolin-based geopolymers. Although the addition of B<sub>4</sub>C improved processability via a “roller-ball” effect and had no discernible impact on the geopolymerisation process, its weakly polar, negatively charged surface led to the formation of a loose, weak-shell interfacial transition zone (ITZ) between the filler and the matrix, thereby reducing mechanical strength and chemical stability. In contrast, CTAB self-assembled into an interdigitated monolayer on the B<sub>4</sub>C surface, reversing its surface charge to positive and promoting its uniform dispersion within the matrix. While CTAB slightly inhibited the dissolution of metakaolin, it preferentially interacted with B<sub>4</sub>C, thereby mitigating the adverse effects on the geopolymerisation process. Moreover, CTAB promoted gelation within the ITZ surrounding B<sub>4</sub>C, facilitating the development of a dense, potassium-deficient, yet electrostatically stabilised microstructure. This synergistic interaction enhanced interfacial bonding between the filler and the matrix, enabled efficient stress transfer, and significantly improved mechanical performance and chemical stability. Furthermore, the B<sub>4</sub>C–CTAB-modified geopolymers demonstrated enhanced neutron shielding performance. Overall, this work offers a promising approach for engineering high-performance, multifunctional geopolymer composites for nuclear and environmental applications.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"200 ","pages":"Article 108096"},"PeriodicalIF":13.1,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609236","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 : 2025-11-26DOI: 10.1016/j.cemconres.2025.108092
Barbara Lothenbach , Ellina Bernard , Zeyu Zhou , Alexander German , Paula Montserrat-Torres , Frank Winnefeld
MgO can be sourced from magnesium silicates or desalination brines with no direct CO2 emissions from the raw materials. This paper critically reviews available literature on magnesium carbonate cements prepared from MgO, water and magnesium carbonates such as nesquehonite or hydromagnesite. Such MgO - magnesium carbonate cements develop high early strength due to the formation of hydrous carbonate-containing brucite (HCB), which incorporates both carbonate and H2O into its structure. Hydrated magnesium carbonate cements have a high potential to bind additional CO2. In the presence of SiO2, magnesium silicate hydrates (M-S-H) also form, which exhibit a high resistance to carbonation. The Mg/Si ratio governs the phase assemblage, as silica can react with HCB to form M-S-H. Magnesium carbonate and silicate hydrate cements have a pH value ranging from 10 to 11, demonstrate a high resistance to leaching, while the corrosion rate of steel rebars is comparable to PC.
{"title":"Critical review of the properties of MgO - magnesium carbonate cements","authors":"Barbara Lothenbach , Ellina Bernard , Zeyu Zhou , Alexander German , Paula Montserrat-Torres , Frank Winnefeld","doi":"10.1016/j.cemconres.2025.108092","DOIUrl":"10.1016/j.cemconres.2025.108092","url":null,"abstract":"<div><div>MgO can be sourced from magnesium silicates or desalination brines with no direct CO<sub>2</sub> emissions from the raw materials. This paper critically reviews available literature on magnesium carbonate cements prepared from MgO, water and magnesium carbonates such as nesquehonite or hydromagnesite. Such MgO - magnesium carbonate cements develop high early strength due to the formation of hydrous carbonate-containing brucite (HCB), which incorporates both carbonate and H<sub>2</sub>O into its structure. Hydrated magnesium carbonate cements have a high potential to bind additional CO<sub>2</sub>. In the presence of SiO<sub>2</sub>, magnesium silicate hydrates (M-S-H) also form, which exhibit a high resistance to carbonation. The Mg/Si ratio governs the phase assemblage, as silica can react with HCB to form M-S-H. Magnesium carbonate and silicate hydrate cements have a pH value ranging from 10 to 11, demonstrate a high resistance to leaching, while the corrosion rate of steel rebars is comparable to PC.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"200 ","pages":"Article 108092"},"PeriodicalIF":13.1,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145598629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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