This paper aims to clarify fiber orientation mechanism in 3D printed ultra-high performance concrete (3DP-UHPC) within a shear flow field. Firstly, the internal flow field characteristics of 3DP-UHPC were examined under various rheological parameters and extrusion speeds. Furthermore, velocity distribution patterns of 3DP-UHPC in nozzle were analyzed by fluid dynamic theory. The fiber orientation in 3DP-UHPC was investigated by X-ray computed tomography technology (X-CT) to validate the prediction model. Results indicate that the flow field in 3DP-UHPC comprises two distinct zones: a low-velocity gradient plug flow region, which minimally impacts fiber rotation, and a high-velocity gradient shear flow region which significantly affects fiber alignment. By reducing the viscosity of UHPC and increasing the extrusion speed, the velocity gradients in both zones are enhanced, optimizing fiber alignment in the printing direction. Based on the Jeffery equation, the velocity gradient coefficient is introduced to establish the relationship between velocity gradient and fiber rotation angle in different nozzle areas, thereby refining the previously proposed fiber orientation prediction model, and effectively controlling the relative error of fiber orientation coefficient to within 6 %.
{"title":"Fiber alignment mechanism in 3D-printed ultra-high performance concrete based on fluid dynamics theory","authors":"Enlai Dong , Zijian Jia , Suduan Rao , Lutao Jia , Kailun Xia , Yifan Gong , Hanquan Yuan , Yu Chen , Wei Wang , Yamei Zhang , Nemkumar Banthia","doi":"10.1016/j.cemconres.2025.108011","DOIUrl":"10.1016/j.cemconres.2025.108011","url":null,"abstract":"<div><div>This paper aims to clarify fiber orientation mechanism in 3D printed ultra-high performance concrete (3DP-UHPC) within a shear flow field. Firstly, the internal flow field characteristics of 3DP-UHPC were examined under various rheological parameters and extrusion speeds. Furthermore, velocity distribution patterns of 3DP-UHPC in nozzle were analyzed by fluid dynamic theory. The fiber orientation in 3DP-UHPC was investigated by X-ray computed tomography technology (X-CT) to validate the prediction model. Results indicate that the flow field in 3DP-UHPC comprises two distinct zones: a low-velocity gradient plug flow region, which minimally impacts fiber rotation, and a high-velocity gradient shear flow region which significantly affects fiber alignment. By reducing the viscosity of UHPC and increasing the extrusion speed, the velocity gradients in both zones are enhanced, optimizing fiber alignment in the printing direction. Based on the Jeffery equation, the velocity gradient coefficient is introduced to establish the relationship between velocity gradient and fiber rotation angle in different nozzle areas, thereby refining the previously proposed fiber orientation prediction model, and effectively controlling the relative error of fiber orientation coefficient to within 6 %.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"198 ","pages":"Article 108011"},"PeriodicalIF":13.1,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144827116","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 : 2025-08-11DOI: 10.1016/j.cemconres.2025.108004
Wena de Nazaré do Rosário Martel , Josée Duchesne , Benoît Fournier
Glass powder (GP) has recently been recognized as a pozzolan by Canadian (CSA) and American standards (ASTM). However, the risk of ASR limits its widespread use in concrete production. This study analyzed a seven-year expansion dataset of GP binary/ternary concrete and correlated it with an accelerated solubility test designed with a synthetic pore solution. Results show that, despite the GP capacity to mitigate ASR, binary blends exceeded the normative expansion threshold. Ternary blends, particularly GP/metakaolin, proved most effective at reducing alkali levels and expansion. Low modified chemical index, reduced Na + K levels, and increased calcium consumption provided lower expansion. The analysis of the dissolution rate and different solution/binder ratios revealed that Na release is controlled by dissolution kinetics, rather than the GP content in the concrete. Early Na release in low GP mixes promotes alkali incorporation into pozzolanic hydrates, while high GP mixes saturate the pore solution, restricting further GP dissolution.
{"title":"Understanding long-term ASR expansion in glass powder ternary concrete blends through accelerated solubility test","authors":"Wena de Nazaré do Rosário Martel , Josée Duchesne , Benoît Fournier","doi":"10.1016/j.cemconres.2025.108004","DOIUrl":"10.1016/j.cemconres.2025.108004","url":null,"abstract":"<div><div>Glass powder (GP) has recently been recognized as a pozzolan by Canadian (CSA) and American standards (ASTM). However, the risk of ASR limits its widespread use in concrete production. This study analyzed a seven-year expansion dataset of GP binary/ternary concrete and correlated it with an accelerated solubility test designed with a synthetic pore solution. Results show that, despite the GP capacity to mitigate ASR, binary blends exceeded the normative expansion threshold. Ternary blends, particularly GP/metakaolin, proved most effective at reducing alkali levels and expansion. Low modified chemical index, reduced Na + K levels, and increased calcium consumption provided lower expansion. The analysis of the dissolution rate and different solution/binder ratios revealed that Na release is controlled by dissolution kinetics, rather than the GP content in the concrete. Early Na release in low GP mixes promotes alkali incorporation into pozzolanic hydrates, while high GP mixes saturate the pore solution, restricting further GP dissolution.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"198 ","pages":"Article 108004"},"PeriodicalIF":13.1,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144809513","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 : 2025-08-11DOI: 10.1016/j.cemconres.2025.108007
Jin Yang , Xinyun Yi , Xingyang He , Ying Su , Yunpeng Liu , Xiong Qian , Bohumír Strnadel , Fazhou Wang
The early rapid water release from superabsorbent polymer (SAP) and the macro-voids left after water release are the main challenges of SAP for internal curing purpose. Inspired by the water release essence of conventional SAP, a new type of SAP composite with inorganic rigid skeleton (RS@SAP) was designed. The hydrogel was in-situ polymerized and assembled in porous skeleton, and the contact area between hydrogel and cement matrix was thus reduced to slow down the early rapid water release. Different from normal SAP, RS@SAP showed a three-stage water release behavior governed by osmotic pressure, capillary action, and combined humidity gradient/capillary forces. This multi-modal regulation achieved an effective water utilization rate of 72.2 %, exceeding the value of conventional SAP by 68.4 %. Microstructural analysis confirmed the suppression of diffusion pores and macro-voids, while mechanical testings revealed reduced negative impacts on compressive strength due to skeletal reinforcement and enhanced interfacial zone properties.
{"title":"Regulating the early rapid water release and eliminating the macro void of superabsorbent polymer by embedded porous rigid skeleton","authors":"Jin Yang , Xinyun Yi , Xingyang He , Ying Su , Yunpeng Liu , Xiong Qian , Bohumír Strnadel , Fazhou Wang","doi":"10.1016/j.cemconres.2025.108007","DOIUrl":"10.1016/j.cemconres.2025.108007","url":null,"abstract":"<div><div>The early rapid water release from superabsorbent polymer (SAP) and the macro-voids left after water release are the main challenges of SAP for internal curing purpose. Inspired by the water release essence of conventional SAP, a new type of SAP composite with inorganic rigid skeleton (RS@SAP) was designed. The hydrogel was in-situ polymerized and assembled in porous skeleton, and the contact area between hydrogel and cement matrix was thus reduced to slow down the early rapid water release. Different from normal SAP, RS@SAP showed a three-stage water release behavior governed by osmotic pressure, capillary action, and combined humidity gradient/capillary forces. This multi-modal regulation achieved an effective water utilization rate of 72.2 %, exceeding the value of conventional SAP by 68.4 %. Microstructural analysis confirmed the suppression of diffusion pores and macro-voids, while mechanical testings revealed reduced negative impacts on compressive strength due to skeletal reinforcement and enhanced interfacial zone properties.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"198 ","pages":"Article 108007"},"PeriodicalIF":13.1,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144809512","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 : 2025-08-09DOI: 10.1016/j.cemconres.2025.108009
Zixian Su, Zengliang Yue, Alastair T.M. Marsh, Marco Di Michiel, Timothy L. Burnett, John L. Provis, Partha P. Paul, Susan A. Bernal, Philip J. Withers
In situ synchrotron X-ray diffraction computed tomography (XRD-CT) and micro-tomography (μCT) are used to determine the effects of accelerated carbonation on sodium silicate- and carbonate-activated slag cement pastes, focusing on changes in crystalline and semi-crystalline phases, and pore structures. Accelerated carbonation leads to decalcification of the interlayer of aluminium-substituted calcium silicate hydrate (C-(A)-S-H), resulting in reduced interlayer distance, volume shrinkage, and increased porosity with larger pore volumes. The hydrotalcite-like Mg-Al LDH phase acts as a CO2 sink, mitigating the increased concentration of CO32− in pore solution via interlayer anion exchange of OH− for CO32−, playing a more significant role in sodium silicate slag cement paste. Additionally, sodium silicate-activated slag cement is found to have a finer, more tortuous pore distribution and higher carbonation resistance than sodium carbonate-activated slag cement, as evidenced by a smaller degree of carbonation-induced C-(A)-S-H shrinkage, and a smaller increase in porosity volume during carbonation.
采用原位同步加速器x射线衍射计算机断层扫描（XRD-CT）和微断层扫描（μCT）研究了加速碳化对水玻璃和碳酸盐活化矿渣水泥浆体的影响，重点研究了矿渣水泥浆体的晶相、半晶相和孔隙结构的变化。碳化加速导致铝取代水合硅酸钙（C-(A)- s - h）夹层脱钙，导致层间距离减小，体积收缩，孔隙率增大，孔隙体积增大。类水滑石Mg-Al LDH相作为CO2汇，通过层间OH -阴离子交换CO32 -，减缓孔溶液中CO32 -浓度的增加，在水玻璃渣水泥浆中发挥更大的作用。与碳酸钠活化矿渣水泥相比，硅酸钠活化矿渣水泥具有更细、更弯曲的孔隙分布和更高的抗碳化能力，表现为碳化引起的C-(a)- s - h收缩程度更小，碳化过程中孔隙体积的增加也更小。
{"title":"4D quantification of C-(A)-S-H and Mg-Al LDH phase alterations and microstructural evolution during accelerated carbonation of alkali-activated slag pastes","authors":"Zixian Su, Zengliang Yue, Alastair T.M. Marsh, Marco Di Michiel, Timothy L. Burnett, John L. Provis, Partha P. Paul, Susan A. Bernal, Philip J. Withers","doi":"10.1016/j.cemconres.2025.108009","DOIUrl":"https://doi.org/10.1016/j.cemconres.2025.108009","url":null,"abstract":"In situ synchrotron X-ray diffraction computed tomography (XRD-CT) and micro-tomography (μCT) are used to determine the effects of accelerated carbonation on sodium silicate- and carbonate-activated slag cement pastes, focusing on changes in crystalline and semi-crystalline phases, and pore structures. Accelerated carbonation leads to decalcification of the interlayer of aluminium-substituted calcium silicate hydrate (C-(A)-S-H), resulting in reduced interlayer distance, volume shrinkage, and increased porosity with larger pore volumes. The hydrotalcite-like Mg-Al LDH phase acts as a CO<sub>2</sub> sink, mitigating the increased concentration of CO<sub>3</sub><sup>2−</sup> in pore solution via interlayer anion exchange of OH<sup>−</sup> for CO<sub>3</sub><sup>2−</sup>, playing a more significant role in sodium silicate slag cement paste. Additionally, sodium silicate-activated slag cement is found to have a finer, more tortuous pore distribution and higher carbonation resistance than sodium carbonate-activated slag cement, as evidenced by a smaller degree of carbonation-induced C-(A)-S-H shrinkage, and a smaller increase in porosity volume during carbonation.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"20 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144802858","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}
Dicalcium silicate is a key carbonatable mineral in Portland cement. Typically, pure C2S is synthesized through high-temperature solid-phase reactions above 1400 °C, but such temperatures can negatively affect its carbonation behavior, with the underlying mechanisms remaining unclear. This study investigated the effect of calcination temperatures (600 °C to 1400 °C) on C2S carbonation. Results show that high calcination temperatures significantly reduce carbonation reactivity and CO2 uptake. This is primarily due to the increase in particle size, the transformation from fibers to particles, and a decrease in specific surface area. Additionally, the internal crystal defects in low-temperature calcined C2S contribute to its high reactivity. However, the temperature-induced reduction in mesoporosity, increase in crystal size, decrease in defects, and phase transition from β-C2S to γ-C2S also affect carbonation reactivity. These factors also influence the polymorphs and morphology of CaCO3. This study offers guidance for developing low-temperature synthesis methods for low-calcium cement.
{"title":"Insights into the carbonation behavior of polymorphs of Ca2SiO4 (C2S): the role of calcination temperature","authors":"Miao Ren, Peiliang Shen, Yi Jiang, Jionghuang He, Qinglong Qin, Chi-sun Poon","doi":"10.1016/j.cemconres.2025.108005","DOIUrl":"https://doi.org/10.1016/j.cemconres.2025.108005","url":null,"abstract":"Dicalcium silicate is a key carbonatable mineral in Portland cement. Typically, pure C<sub>2</sub>S is synthesized through high-temperature solid-phase reactions above 1400 °C, but such temperatures can negatively affect its carbonation behavior, with the underlying mechanisms remaining unclear. This study investigated the effect of calcination temperatures (600 °C to 1400 °C) on C<sub>2</sub>S carbonation. Results show that high calcination temperatures significantly reduce carbonation reactivity and CO<sub>2</sub> uptake. This is primarily due to the increase in particle size, the transformation from fibers to particles, and a decrease in specific surface area. Additionally, the internal crystal defects in low-temperature calcined C<sub>2</sub>S contribute to its high reactivity. However, the temperature-induced reduction in mesoporosity, increase in crystal size, decrease in defects, and phase transition from β-C<sub>2</sub>S to γ-C<sub>2</sub>S also affect carbonation reactivity. These factors also influence the polymorphs and morphology of CaCO<sub>3</sub>. This study offers guidance for developing low-temperature synthesis methods for low-calcium cement.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"173 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144802857","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}
Elucidating the impact of nitrate anions on sulfate balance mechanism of cement is essential for optimizing the hydration performance of cementitious systems. This knowledge provides fundamental insights into regulating cementitious systems under varying service conditions. This study investigated how varying SO₃ content and nitrate anions affect sulfate balance in C3S/C3A pastes and the impact of these alterations on the hydration process. The influence of nitrate anions from Mg(NO₃)₂ on sulfate balance was determined by calorimetry, ICP-OES, TG, XRD and SEM. It was found that nitrate anions counteract Mg2+ inhibition of C3S and C3A hydration by enhancing mineral dissolution, liberating Ca2+ into pore solutions to accelerate hydration. Accelerating the formation process of ettringite (AFt) increased demand for sulfate. This Ca2+ enrichment promotes portlandite supersaturation, which shortens the hydration induction period and accelerates C-S-H growth. The sulfate content significantly influences C-S-H growth kinetics at fixed nitrate concentrations.
{"title":"Effect of nitrate anions on sulfate balance and hydration kinetics in C3S/C3A systems","authors":"Lei Lu, Xiao Liu, Jian Wang, Simai Wang, Yuhan Yao, Yurui Xu, Minghui Jiang, Yanzhen Xiao, Yanxi Li, Ziming Wang, Suping Cui","doi":"10.1016/j.cemconres.2025.108008","DOIUrl":"https://doi.org/10.1016/j.cemconres.2025.108008","url":null,"abstract":"Elucidating the impact of nitrate anions on sulfate balance mechanism of cement is essential for optimizing the hydration performance of cementitious systems. This knowledge provides fundamental insights into regulating cementitious systems under varying service conditions. This study investigated how varying SO₃ content and nitrate anions affect sulfate balance in C<sub>3</sub>S/C<sub>3</sub>A pastes and the impact of these alterations on the hydration process. The influence of nitrate anions from Mg(NO₃)₂ on sulfate balance was determined by calorimetry, ICP-OES, TG, XRD and SEM. It was found that nitrate anions counteract Mg<sup>2+</sup> inhibition of C<sub>3</sub>S and C<sub>3</sub>A hydration by enhancing mineral dissolution, liberating Ca<sup>2+</sup> into pore solutions to accelerate hydration. Accelerating the formation process of ettringite (AFt) increased demand for sulfate. This Ca<sup>2+</sup> enrichment promotes portlandite supersaturation, which shortens the hydration induction period and accelerates C-S-H growth. The sulfate content significantly influences C-S-H growth kinetics at fixed nitrate concentrations.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"290 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144802870","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 : 2025-08-06DOI: 10.1016/j.cemconres.2025.108006
Lupesh Dudi, Shashank Bishnoi
This study investigates why mass transport properties differ between Portland cement (PC) and low-clinker binders before and after carbonation by examining their underlying microstructural characteristics. Mass transport parameters (sorption rate, oxygen permeability, and chloride migration) were evaluated for non‑carbonated and carbonated mortars made with PC and low-clinker binders (fly ash, slag, limestone-calcined clay, and fly ash–slag composites) at water-to-binder ratios of 0.4, 0.5, and 0.6. Complementary microstructural analyses included mercury intrusion porosimetry (MIP), N₂ adsorption, saturation degree, pore-connectivity factor, and water-accessible porosity. For non‑carbonated mortars, no generalized correlation was found between transport properties and microstructure due to the varying effects of different SCMs on critical/threshold pore diameter, pore-connectivity, and pore surface/solution interaction with transporting media. However, incorporating material coefficients (based on transport mechanism) alongside porosity resulted in a strong correlation across different mixes. After carbonation, low-clinker binders exhibited increased transport due to coarsened pore structures, higher connectivity, and reduced interaction of transporting media with pore surface/solution. Furthermore, a generalized correlation was found between mass transport properties and microstructural parameters in carbonated mortars across all mass transport mechanisms, indicating that microstructural differences from SCMs addition diminish after carbonation. Carbonation results in homogenizing key features such as hygroscopicity and pore surface/solution interaction with transporting media. Additionally, in carbonated mortars, pore-connectivity, bulk conductivity, and critical/threshold pore diameter can be treated as functions of total porosity, enabling the development of cement-independent mass transport models.
{"title":"Revealing the relationships between transport properties and microstructure characteristics in low-clinker binders before and after carbonation","authors":"Lupesh Dudi, Shashank Bishnoi","doi":"10.1016/j.cemconres.2025.108006","DOIUrl":"10.1016/j.cemconres.2025.108006","url":null,"abstract":"<div><div>This study investigates why mass transport properties differ between Portland cement (PC) and low-clinker binders before and after carbonation by examining their underlying microstructural characteristics. Mass transport parameters (sorption rate, oxygen permeability, and chloride migration) were evaluated for non‑carbonated and carbonated mortars made with PC and low-clinker binders (fly ash, slag, limestone-calcined clay, and fly ash–slag composites) at water-to-binder ratios of 0.4, 0.5, and 0.6. Complementary microstructural analyses included mercury intrusion porosimetry (MIP), N₂ adsorption, saturation degree, pore-connectivity factor, and water-accessible porosity. For non‑carbonated mortars, no generalized correlation was found between transport properties and microstructure due to the varying effects of different SCMs on critical/threshold pore diameter, pore-connectivity, and pore surface/solution interaction with transporting media. However, incorporating material coefficients (based on transport mechanism) alongside porosity resulted in a strong correlation across different mixes. After carbonation, low-clinker binders exhibited increased transport due to coarsened pore structures, higher connectivity, and reduced interaction of transporting media with pore surface/solution. Furthermore, a generalized correlation was found between mass transport properties and microstructural parameters in carbonated mortars across all mass transport mechanisms, indicating that microstructural differences from SCMs addition diminish after carbonation. Carbonation results in homogenizing key features such as hygroscopicity and pore surface/solution interaction with transporting media. Additionally, in carbonated mortars, pore-connectivity, bulk conductivity, and critical/threshold pore diameter can be treated as functions of total porosity, enabling the development of cement-independent mass transport models.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"198 ","pages":"Article 108006"},"PeriodicalIF":13.1,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144780386","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 : 2025-08-01DOI: 10.1016/j.cemconres.2025.108003
Fei Meng , Kaidong Han , Tengfei Guo , Xin Shu , Yandong Guo , Lei Dong , Jingshun Cai , Qianping Ran
The bulk modification of cementitious materials by hydrophobic agents is an effective strategy to reduce the water absorption. However, the decrease in compressive strength has been one of the most significant problems. We reported in this paper the synthesis of a sustained-release capsule (OTES@SC) with n-octyltriethoxy silane (OTES) as core material and silica shell. The capsule (containing 70.0 % of OTES) enabled the continuous release of OTES within days. The addition of OTES@SC reduced the water absorption while improved the compressive strength of hardened cement paste. Both the effects would be more pronounced at higher capsule dosages (~70.6 % water absorption reducing and 17.4 % increase of compressive strength at 0.5 wt% capsule dosage). The sustained release of OTES from OTES@SC enabled the continuous surface modification by OTES both already in cement paste and newly formed. Compared with the direct addition of OTES (average thickness of the hydrophobic layer decreased from ~10 nm to ~0 nm during hydration), the hydrophobic layer had reached a thickness of a few molecules layer at 28 d, exhibiting significantly improved uniformity on cement paste particle surfaces. The thinner layer and the normal hydration of part of reactive sites of clinkers greatly reduced the inhibition effect of OTES on hydration. Additionally, the pozzolanic effect and nano-size of silica further promoted hydration. Thus, OTES@SC improved hydration degree and refined pore structure of paste.
{"title":"Elucidating the effects and mechanisms of OTES@silica nano capsules on water resistance and compressive strength of cement paste","authors":"Fei Meng , Kaidong Han , Tengfei Guo , Xin Shu , Yandong Guo , Lei Dong , Jingshun Cai , Qianping Ran","doi":"10.1016/j.cemconres.2025.108003","DOIUrl":"10.1016/j.cemconres.2025.108003","url":null,"abstract":"<div><div>The bulk modification of cementitious materials by hydrophobic agents is an effective strategy to reduce the water absorption. However, the decrease in compressive strength has been one of the most significant problems. We reported in this paper the synthesis of a sustained-release capsule (OTES@SC) with n-octyltriethoxy silane (OTES) as core material and silica shell. The capsule (containing 70.0 % of OTES) enabled the continuous release of OTES within days. The addition of OTES@SC reduced the water absorption while improved the compressive strength of hardened cement paste. Both the effects would be more pronounced at higher capsule dosages (~70.6 % water absorption reducing and 17.4 % increase of compressive strength at 0.5 wt% capsule dosage). The sustained release of OTES from OTES@SC enabled the continuous surface modification by OTES both already in cement paste and newly formed. Compared with the direct addition of OTES (average thickness of the hydrophobic layer decreased from ~10 nm to ~0 nm during hydration), the hydrophobic layer had reached a thickness of a few molecules layer at 28 d, exhibiting significantly improved uniformity on cement paste particle surfaces. The thinner layer and the normal hydration of part of reactive sites of clinkers greatly reduced the inhibition effect of OTES on hydration. Additionally, the pozzolanic effect and nano-size of silica further promoted hydration. Thus, OTES@SC improved hydration degree and refined pore structure of paste.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"198 ","pages":"Article 108003"},"PeriodicalIF":13.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144750250","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 : 2025-07-24DOI: 10.1016/j.cemconres.2025.108002
Zuobang Yao , Ram Pal , Haemin Song , Arthur Van de Keere , Ali Kashani , Elke Gruyaert , Taehwan Kim
This paper presented the experimental results of investigating chloride resistance and the microstructure of alkali-activated concrete (AAC). To show the reliable and efficient chloride transport analyses for AAC, a modified rapid chloride penetration test using 10 V was validated, and the conventional chloride profile methods were compared with the newly developed micro X-ray fluorescence (μXRF) profile method. Six AAC mixtures incorporating different precursors were evaluated for mechanical strength, water absorption, chloride diffusion, and binding. At the same content of ground granulated blast furnace slag in mixtures, the precursor incorporating calcined bauxite tailings and rice husk ash increased porosity and reduced chloride resistance compared to that containing fly ash. This study revealed that chloride binding in all AAC used in this study was predominantly physical and reversible, contrasting with Portland cement systems. μXRF technique provided reliable and spatially resolved chloride profile data for AAC. This study provides valuable insights into AAC performance and testing, emphasising the importance of precursor selection for sustainable AAC.
{"title":"Chloride transport, binding, and microstructure in alkali-activated concrete with different types of precursor combinations","authors":"Zuobang Yao , Ram Pal , Haemin Song , Arthur Van de Keere , Ali Kashani , Elke Gruyaert , Taehwan Kim","doi":"10.1016/j.cemconres.2025.108002","DOIUrl":"10.1016/j.cemconres.2025.108002","url":null,"abstract":"<div><div>This paper presented the experimental results of investigating chloride resistance and the microstructure of alkali-activated concrete (AAC). To show the reliable and efficient chloride transport analyses for AAC, a modified rapid chloride penetration test using 10 V was validated, and the conventional chloride profile methods were compared with the newly developed micro X-ray fluorescence (μXRF) profile method. Six AAC mixtures incorporating different precursors were evaluated for mechanical strength, water absorption, chloride diffusion, and binding. At the same content of ground granulated blast furnace slag in mixtures, the precursor incorporating calcined bauxite tailings and rice husk ash increased porosity and reduced chloride resistance compared to that containing fly ash. This study revealed that chloride binding in all AAC used in this study was predominantly physical and reversible, contrasting with Portland cement systems. μXRF technique provided reliable and spatially resolved chloride profile data for AAC. This study provides valuable insights into AAC performance and testing, emphasising the importance of precursor selection for sustainable AAC.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"198 ","pages":"Article 108002"},"PeriodicalIF":10.9,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144694944","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 : 2025-07-22DOI: 10.1016/j.cemconres.2025.107999
Yun Chen , Jiayi Chen , Mayank Gupta , Xuhui Liang , Luiz Miranda de Lima , Zhiyuan Xu , Yibing Zuo , Suhong Yin , Qijun Yu , Guang Ye
This study presents an extended numerical approach based on GeoMicro3D to simulate the reaction kinetics and three-dimensional (3D) microstructure evolution of alkali-activated fly ash (AAFA). Dissolution experiments were conducted under varying NaOH concentrations and temperatures to formulate predictive rate functions for Si and Al release. These experimentally derived kinetic functions, alongside a thermodynamic dataset for N-(C-)A-S-H gels, were incorporated into the GeoMicro3D model to capture the chemical reactions and 3D microstructure evolution of AAFA. The model well captured reaction degree of fly ash, formation of solid products, evolution of pore solution compositions, and porosity over time. Notably, it is the first to predict the time-dependent spatial distribution of phases within the 3D AAFA microstructure by integrating kinetic and microstructural modeling. Dual validation using both dissolution data and microstructural metrics demonstrates the model's reliability and robustness. This integrated framework provides new insights into the coupled chemical–microstructural evolution of alkali-activated materials.
本文提出了一种基于GeoMicro3D的扩展数值方法来模拟碱活化粉煤灰（AAFA）的反应动力学和三维（3D）微观结构演化。在不同的NaOH浓度和温度下进行了溶解实验，以建立Si和Al释放的预测速率函数。这些实验导出的动力学函数，以及N-(C-) a - s - h凝胶的热力学数据集，被整合到GeoMicro3D模型中，以捕捉AAFA的化学反应和3D微观结构演变。该模型较好地捕捉了粉煤灰的反应程度、固体产物的形成、孔隙溶液组成的演变以及孔隙度随时间的变化。值得注意的是，这是第一个通过整合动力学和微观结构建模来预测三维AAFA微观结构中相的时空分布的研究。使用溶解数据和微观结构指标的双重验证证明了模型的可靠性和稳健性。这一综合框架为碱活化材料的化学-微观结构耦合演化提供了新的见解。
{"title":"An experimental and numerical study of alkali-activated fly ash paste – from dissolution kinetics to microstructure formation","authors":"Yun Chen , Jiayi Chen , Mayank Gupta , Xuhui Liang , Luiz Miranda de Lima , Zhiyuan Xu , Yibing Zuo , Suhong Yin , Qijun Yu , Guang Ye","doi":"10.1016/j.cemconres.2025.107999","DOIUrl":"10.1016/j.cemconres.2025.107999","url":null,"abstract":"<div><div>This study presents an extended numerical approach based on GeoMicro3D to simulate the reaction kinetics and three-dimensional (3D) microstructure evolution of alkali-activated fly ash (AAFA). Dissolution experiments were conducted under varying NaOH concentrations and temperatures to formulate predictive rate functions for Si and Al release. These experimentally derived kinetic functions, alongside a thermodynamic dataset for N-(C-)A-S-H gels, were incorporated into the GeoMicro3D model to capture the chemical reactions and 3D microstructure evolution of AAFA. The model well captured reaction degree of fly ash, formation of solid products, evolution of pore solution compositions, and porosity over time. Notably, it is the first to predict the time-dependent spatial distribution of phases within the 3D AAFA microstructure by integrating kinetic and microstructural modeling. Dual validation using both dissolution data and microstructural metrics demonstrates the model's reliability and robustness. This integrated framework provides new insights into the coupled chemical–microstructural evolution of alkali-activated materials.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"198 ","pages":"Article 107999"},"PeriodicalIF":10.9,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144678281","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}
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