Pub Date : 2024-12-05DOI: 10.1016/j.cemconres.2024.107739
Ellina Bernard, Barbara Lothenbach, Rupert J. Myers, Marcus H.N. Yio
This study explores different methods for precipitating carbonated Mg-Fe3+ layered double hydroxides (LDHs) with Mg/Fe3+ ratios ranging from 2 to 2.5. Two synthesis approaches were investigated: a) CO3-Mg-Fe3+-LDH co-precipitated directly from MgO, Fe(NO3)3 and Na2CO3 and b) NO3-Mg-Fe3+-LDH precipitated by adding NaOH to Mg(NO3)2-Fe(NO3)3 solutions, followed by ion exchange with Na2CO3 to form CO3-Mg-Fe3+-LDH. The solids were characterised using TGA, XRD and FTIR. For the co-precipitated samples in the presence of Na2CO3, the formation of carbonate-LDH was accompanied by ~10–30 wt% of hydromagnesite, while CO3-Mg-Fe3+-LDH modified from the NO3-Mg-Fe3+-LDH did not show any other Mg‑carbonates but contained Fe hydroxides, as evidenced by their brown coloration. All samples were re-equilibrated at 7, 20 and 50 °C. The solubility product (log Kso) was calculated from solution analysis, and preliminary thermodynamic data are presented. The findings provide insights into the stability and formation conditions of carbonated Mg-Fe3+ LDH phases in carbonate-rich environments.
{"title":"Pyroaurite-like phases (Mg-Fe3+ LDH) synthesis and solubility","authors":"Ellina Bernard, Barbara Lothenbach, Rupert J. Myers, Marcus H.N. Yio","doi":"10.1016/j.cemconres.2024.107739","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107739","url":null,"abstract":"This study explores different methods for precipitating carbonated Mg-Fe<sup>3+</sup> layered double hydroxides (LDHs) with Mg/Fe<sup>3+</sup> ratios ranging from 2 to 2.5. Two synthesis approaches were investigated: a) CO<sub>3</sub>-Mg-Fe<sup>3+</sup>-LDH co-precipitated directly from MgO, Fe(NO<sub>3</sub>)<sub>3</sub> and Na<sub>2</sub>CO<sub>3</sub> and b) NO<sub>3</sub>-Mg-Fe<sup>3+</sup>-LDH precipitated by adding NaOH to Mg(NO<sub>3</sub>)<sub>2</sub>-Fe(NO<sub>3</sub>)<sub>3</sub> solutions, followed by ion exchange with Na<sub>2</sub>CO<sub>3</sub> to form CO<sub>3</sub>-Mg-Fe<sup>3+</sup>-LDH. The solids were characterised using TGA, XRD and FTIR. For the co-precipitated samples in the presence of Na<sub>2</sub>CO<sub>3</sub>, the formation of carbonate-LDH was accompanied by ~10–30 wt% of hydromagnesite, while CO<sub>3</sub>-Mg-Fe<sup>3+</sup>-LDH modified from the NO<sub>3</sub>-Mg-Fe<sup>3+</sup>-LDH did not show any other Mg‑carbonates but contained Fe hydroxides, as evidenced by their brown coloration. All samples were re-equilibrated at 7, 20 and 50 °C. The solubility product (log Kso) was calculated from solution analysis, and preliminary thermodynamic data are presented. The findings provide insights into the stability and formation conditions of carbonated Mg-Fe<sup>3+</sup> LDH phases in carbonate-rich environments.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"77 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142776419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-05DOI: 10.1016/j.cemconres.2024.107714
Tobias Völker, Friedrich M. Mensing, Sabine Kruschwitz
The cement content in concrete significantly influences critical properties such as durability, permeability, strength, and workability. Traditional methods for estimating the cement content face limitations. These include the need for comprehensive chemical and solubility knowledge, extensive sample preparation, and their time-consuming and destructive nature. This study investigates the application of laser-induced breakdown spectroscopy (LIBS) as an alternative method. It involves probing concrete samples with high spatial resolution and analyzing the resultant spectra. The methodology is first tested on mesoscale concrete models to assess limitations and inherent errors. Subsequently, the methodology is applied to actual concrete samples with varying cement content and aggregate size distributions. The results demonstrate a promising accuracy, with an average relative error of approximately 8%. This paper offers a comprehensive evaluation of the method’s advantages, limitations, and factors influencing its practical applicability in field conditions.
{"title":"Estimation of cement content in concrete by spatially resolved laser induced breakdown spectroscopy","authors":"Tobias Völker, Friedrich M. Mensing, Sabine Kruschwitz","doi":"10.1016/j.cemconres.2024.107714","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107714","url":null,"abstract":"The cement content in concrete significantly influences critical properties such as durability, permeability, strength, and workability. Traditional methods for estimating the cement content face limitations. These include the need for comprehensive chemical and solubility knowledge, extensive sample preparation, and their time-consuming and destructive nature. This study investigates the application of laser-induced breakdown spectroscopy (LIBS) as an alternative method. It involves probing concrete samples with high spatial resolution and analyzing the resultant spectra. The methodology is first tested on mesoscale concrete models to assess limitations and inherent errors. Subsequently, the methodology is applied to actual concrete samples with varying cement content and aggregate size distributions. The results demonstrate a promising accuracy, with an average relative error of approximately 8%. This paper offers a comprehensive evaluation of the method’s advantages, limitations, and factors influencing its practical applicability in field conditions.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"87 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142776422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-02DOI: 10.1016/j.cemconres.2024.107732
S. Mingione, D. Jansen, F. Winnefeld, S.V. Churakov, B. Lothenbach
Xonotlite forms under hydrothermal conditions and it dehydrates to β-wollastonite between 770 and 800 °C under atmospheric pressure. The solubility of xonotlite is poorly known, as the experimental datasets reported in literature differ by as much as 10 log units. This study investigates the impact of temperature (7, 20, 50 and 80 °C) on the solubility of xonotlite by dissolution experiments from undersaturation. The derived solubility data are comparable to those reported in literature at 25 °C for synthesized xonotlite, while the much higher solubility reported in literature for natural xonotlite seems to describe the solubility of amorphous C-S-H. The solubility of xonotlite increases moderately at lower temperature. At 7 °C, xonotlite was found to co-exist with tobermorite.
硅灰石在水热条件下形成，在770 ~ 800℃大气压下脱水成β-硅灰石。硅钙石的溶解度鲜为人知，因为文献中报道的实验数据集相差多达10个对数单位。通过欠饱和溶解实验，研究了温度（7、20、50和80℃）对硬硅橄榄石溶解度的影响。导出的溶解度数据与文献中报道的合成硬硅钙石在25°C下的溶解度数据相当，而文献中报道的天然硬硅钙石更高的溶解度似乎描述了无定形C- s - h的溶解度。硅钙石的溶解度在较低温度下适度提高。在7℃时，发现硅钙石与托贝莫来石共存。
{"title":"Effect of temperature on the solubility of xonotlite","authors":"S. Mingione, D. Jansen, F. Winnefeld, S.V. Churakov, B. Lothenbach","doi":"10.1016/j.cemconres.2024.107732","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107732","url":null,"abstract":"Xonotlite forms under hydrothermal conditions and it dehydrates to β-wollastonite between 770 and 800 °C under atmospheric pressure. The solubility of xonotlite is poorly known, as the experimental datasets reported in literature differ by as much as 10 log units. This study investigates the impact of temperature (7, 20, 50 and 80 °C) on the solubility of xonotlite by dissolution experiments from undersaturation. The derived solubility data are comparable to those reported in literature at 25 °C for synthesized xonotlite, while the much higher solubility reported in literature for natural xonotlite seems to describe the solubility of amorphous C-S-H. The solubility of xonotlite increases moderately at lower temperature. At 7 °C, xonotlite was found to co-exist with tobermorite.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"116 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142760007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-02DOI: 10.1016/j.cemconres.2024.107730
K. De Weerdt, M. Bagheri, J. Lindgård, H. Lindstad, A. Rodrigues, J. Duchesne, P.-L. Fecteau, M.K. Haugen, T. Danner, B.J. Wigum, N. Oberhardt, K. Aasly, B. Lothenbach
The accelerated mortar bar test (AMBT) for pyrrhotite (Fe1-xS) containing aggregates accelerates expansion using two regimes: Phase I, during which Fe1-xS oxidation to iron hydroxide is accelerated by bleach and storage at 80 °C; Phase II that promotes thaumasite formation with continued bleach soaking and storage at 4 °C. Two bleach concentrations and one aggregate containing 0.5 wt% Fe1-xS are tested. SEM-EDX data indicate that the oxidized iron precipitates as iron hydroxide at the place of the Fe1-xS, leading to significant expansion (0.22%) during Phase I. The released S distributes in the cement paste but leads only to limited amount of additional ettringite and thaumasite and thus only to limited expansion (0.07%). The NaOCl bleach reduced during the test resulting in chloride and thus to Friedel's salt formation and ettringite stabilization at 80 °C. Only during the prolongation of Phase II, the formation of thaumasite and additional expansion was observed.
{"title":"Changes in cement paste during accelerated mortar bar testing for pyrrhotite containing aggregate","authors":"K. De Weerdt, M. Bagheri, J. Lindgård, H. Lindstad, A. Rodrigues, J. Duchesne, P.-L. Fecteau, M.K. Haugen, T. Danner, B.J. Wigum, N. Oberhardt, K. Aasly, B. Lothenbach","doi":"10.1016/j.cemconres.2024.107730","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107730","url":null,"abstract":"The accelerated mortar bar test (AMBT) for pyrrhotite (Fe<sub>1-x</sub>S) containing aggregates accelerates expansion using two regimes: Phase I, during which Fe<sub>1-x</sub>S oxidation to iron hydroxide is accelerated by bleach and storage at 80 °C; Phase II that promotes thaumasite formation with continued bleach soaking and storage at 4 °C. Two bleach concentrations and one aggregate containing 0.5 wt% Fe<sub>1-x</sub>S are tested. SEM-EDX data indicate that the oxidized iron precipitates as iron hydroxide at the place of the Fe<sub>1-x</sub>S, leading to significant expansion (0.22%) during Phase I. The released S distributes in the cement paste but leads only to limited amount of additional ettringite and thaumasite and thus only to limited expansion (0.07%). The NaOCl bleach reduced during the test resulting in chloride and thus to Friedel's salt formation and ettringite stabilization at 80 °C. Only during the prolongation of Phase II, the formation of thaumasite and additional expansion was observed.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"12 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142760591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-30DOI: 10.1016/j.cemconres.2024.107741
Alexandra Bertron , Cyrill Grengg , Matthieu Peyre Lavigne , Holger Wack , Gregor J.G. Gluth , Amr Aboulela , Vanessa Sonois , Tilman Gehrke , Florian Mittermayr
The biodeterioration of concrete elements in sewer systems and their repair is of significant economic and societal concern. However, the available test methods to assess the performance of cementitious materials under the relevant conditions are insufficiently validated. In the present study, two biological test methods and a standardised chemical test were applied to two sewer repair mortars and a reference mortar, and the performances of these materials were compared in a severely deteriorating sewer environment. In both biological tests, the induction period was considerably shorter than that of the field, and time-resolved recording of durability indicators enabled to determine deterioration rates in the steady-state regime, which compared reasonably well with each other and with the behaviour in the sewer environment. The chemical test does not allow to obtain a deterioration rate, and the observed relative performance differences of the mortars deviated from the results of the biological tests.
{"title":"Comparative evaluation of laboratory methods for performance assessment of cementitious materials in wastewater networks: Biological and chemical tests versus field exposure","authors":"Alexandra Bertron , Cyrill Grengg , Matthieu Peyre Lavigne , Holger Wack , Gregor J.G. Gluth , Amr Aboulela , Vanessa Sonois , Tilman Gehrke , Florian Mittermayr","doi":"10.1016/j.cemconres.2024.107741","DOIUrl":"10.1016/j.cemconres.2024.107741","url":null,"abstract":"<div><div>The biodeterioration of concrete elements in sewer systems and their repair is of significant economic and societal concern. However, the available test methods to assess the performance of cementitious materials under the relevant conditions are insufficiently validated. In the present study, two biological test methods and a standardised chemical test were applied to two sewer repair mortars and a reference mortar, and the performances of these materials were compared in a severely deteriorating sewer environment. In both biological tests, the induction period was considerably shorter than that of the field, and time-resolved recording of durability indicators enabled to determine deterioration rates in the steady-state regime, which compared reasonably well with each other and with the behaviour in the sewer environment. The chemical test does not allow to obtain a deterioration rate, and the observed relative performance differences of the mortars deviated from the results of the biological tests.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"188 ","pages":"Article 107741"},"PeriodicalIF":10.9,"publicationDate":"2024-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142753009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-28DOI: 10.1016/j.cemconres.2024.107734
Fujian Yang , Zhihao Zhao , Yuan Liu , Man Li , Jinliang Song , Dawei Hu , Hui Zhou
Flowing effect on concrete deterioration caused by sulfate attack at varying flow rates was studied. It was found that an increased flow rate can expedite the weakening of the concrete's elastic modulus in the short term, thus causing an earlier onset of this weakening. However, the long-term deterioration of the elastic modulus remains unaffected by the flow rate due to the limited amount of products responsible for concrete deterioration. Notably, the deterioration depth or rate of the elastic modulus increases with higher flow rates due to the scouring effect of sulfate flow. To quantify this acceleration effect, an acceleration coefficient was defined, representing the impact of flow rate on the weakening process of concrete. It is approximately 1.20 for every 0.5 m/s increase in flow rate within the tested range. This coefficient provides a useful metric to assess the durability of concrete to sulfate attack under varying flow conditions.
{"title":"Effect of flow rate on spatio-temporal deterioration of concrete under flowing sulfate attack","authors":"Fujian Yang , Zhihao Zhao , Yuan Liu , Man Li , Jinliang Song , Dawei Hu , Hui Zhou","doi":"10.1016/j.cemconres.2024.107734","DOIUrl":"10.1016/j.cemconres.2024.107734","url":null,"abstract":"<div><div>Flowing effect on concrete deterioration caused by sulfate attack at varying flow rates was studied. It was found that an increased flow rate can expedite the weakening of the concrete's elastic modulus in the short term, thus causing an earlier onset of this weakening. However, the long-term deterioration of the elastic modulus remains unaffected by the flow rate due to the limited amount of products responsible for concrete deterioration. Notably, the deterioration depth or rate of the elastic modulus increases with higher flow rates due to the scouring effect of sulfate flow. To quantify this acceleration effect, an acceleration coefficient was defined, representing the impact of flow rate on the weakening process of concrete. It is approximately 1.20 for every 0.5 m/s increase in flow rate within the tested range. This coefficient provides a useful metric to assess the durability of concrete to sulfate attack under varying flow conditions.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"188 ","pages":"Article 107734"},"PeriodicalIF":10.9,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142735673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The evolution of early mechanical properties of 3D-printed concrete (3DPC) plays a crucial role in early constructability, while current methods face challenges on the tradeoff between the accuracy and feasibility of mechanical properties characterization. In this paper, we designed a sheet-like indenter configuration to quantitatively obtain the yield stress of fresh 3DPC. First, we show the typical force-depth curve of sheet-like indenters obtained during the penetration test and analyze the main factors affecting the penetration resistance at various regimes. Then, we derive the quantitative correlation between the yield stress and the force-depth curve based on numerical simulation. Our results show that the slipping phenomenon between the indenter side and the material leads to an underestimation of the yield stress compared to the standard compression test and cone-shaped indenter. We moreover propose a sheet-like indenter with surface roughness modification to obtain the accurate yield stress value, together with a formula for the yield stress calculation based on the force-depth curve. Finally, we assess the feasibility of the proposed approach, which can robustly predict fresh 3DPC with yield stresses in the range of 1–100 kPa.
{"title":"Penetration test of sheet-like indenter for yield stress assessment of 3D-printed concrete","authors":"Haoyu Lu, Lizhi Zhang, Junkai Wang, Zhaoxin Shi, Wei She, Wenqiang Zuo","doi":"10.1016/j.cemconres.2024.107728","DOIUrl":"10.1016/j.cemconres.2024.107728","url":null,"abstract":"<div><div>The evolution of early mechanical properties of 3D-printed concrete (3DPC) plays a crucial role in early constructability, while current methods face challenges on the tradeoff between the accuracy and feasibility of mechanical properties characterization. In this paper, we designed a sheet-like indenter configuration to quantitatively obtain the yield stress of fresh 3DPC. First, we show the typical force-depth curve of sheet-like indenters obtained during the penetration test and analyze the main factors affecting the penetration resistance at various regimes. Then, we derive the quantitative correlation between the yield stress and the force-depth curve based on numerical simulation. Our results show that the slipping phenomenon between the indenter side and the material leads to an underestimation of the yield stress compared to the standard compression test and cone-shaped indenter. We moreover propose a sheet-like indenter with surface roughness modification to obtain the accurate yield stress value, together with a formula for the yield stress calculation based on the force-depth curve. Finally, we assess the feasibility of the proposed approach, which can robustly predict fresh 3DPC with yield stresses in the range of 1–100 kPa.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"188 ","pages":"Article 107728"},"PeriodicalIF":10.9,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142706203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study focuses on the numerical modeling of the reaction and microstructure development of a one-part granite-based geopolymer, which is often used for carbon capture and storage (CCS) applications. This work extends the capabilities of GeoMicro3D to model one-part geopolymers containing different precursors and activators (solid and in solution). The model considers the particle size distribution of different solids and the real shape of particles to prepare the initial simulation domain. Further, the dissolution rates of different solids estimated from the experiments were used to model the dissolution of different elements in the pore solution. Subsequently, the model utilizes classical nucleation probability modeling coupled with thermodynamic modeling to estimate the precipitation of products in the microstructure. Experiments were performed to study the pore solution, reaction degree, and amount of products in the microstructure, which were further compared with the simulation results to check the rationality of the model.
{"title":"Reaction and microstructure development of one-part geopolymer for wellbore applications – An experimental and numerical study","authors":"Mayank Gupta , Xiujiao Qiu , Mohamed Omran , Yun Chen , Mahmoud Khalifeh , Guang Ye","doi":"10.1016/j.cemconres.2024.107738","DOIUrl":"10.1016/j.cemconres.2024.107738","url":null,"abstract":"<div><div>This study focuses on the numerical modeling of the reaction and microstructure development of a one-part granite-based geopolymer, which is often used for carbon capture and storage (CCS) applications. This work extends the capabilities of GeoMicro3D to model one-part geopolymers containing different precursors and activators (solid and in solution). The model considers the particle size distribution of different solids and the real shape of particles to prepare the initial simulation domain. Further, the dissolution rates of different solids estimated from the experiments were used to model the dissolution of different elements in the pore solution. Subsequently, the model utilizes classical nucleation probability modeling coupled with thermodynamic modeling to estimate the precipitation of products in the microstructure. Experiments were performed to study the pore solution, reaction degree, and amount of products in the microstructure, which were further compared with the simulation results to check the rationality of the model.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"188 ","pages":"Article 107738"},"PeriodicalIF":10.9,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142718565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-25DOI: 10.1016/j.cemconres.2024.107736
Zushi Tian, Xiaojuan Kang, Haodong Ji, Hailong Ye
While extensive evidence indicates that the porous microstructure of the steel-concrete interface (SCI) is the key factor contributing to early depassivation and expedited corrosion propagation of steel rebar, there remains a lack of quantitative relationship between the SCI microstructural parameters and corrosion rate of steel, particularly under unsaturated conditions. In this work, the effects of rebar arrangement direction (i.e., horizontal and vertical orientations), binder type (i.e., ordinary Portland cement and alkali-activated slag), presence of aggregate, and chloride content, on both the SCI and chloride-induced corrosion rate of steel were systematically investigated and quantified at different relative humidity levels. The results indicated that in comparison with Portland cement counterparts, the reaction products of alkali-activated slag fill the gap under the horizontally oriented steel rebars, favoring more densified SCI microstructure and better corrosion protection. Quantitative analysis reveals that in the unsaturated state, the corrosion rate of steel decreases more slowly in more porous SCI microstructure. An image-based model is proposed to quantitatively link SCI microstructure and corrosion rate of steel, which is applicable to both Portland cement and alkali-activated slag systems in saturated and unsaturated conditions.
{"title":"Quantitative relationship between microstructure of steel-concrete interface and chloride-induced corrosion rate of steel in unsaturated cementitious materials","authors":"Zushi Tian, Xiaojuan Kang, Haodong Ji, Hailong Ye","doi":"10.1016/j.cemconres.2024.107736","DOIUrl":"10.1016/j.cemconres.2024.107736","url":null,"abstract":"<div><div>While extensive evidence indicates that the porous microstructure of the steel-concrete interface (SCI) is the key factor contributing to early depassivation and expedited corrosion propagation of steel rebar, there remains a lack of quantitative relationship between the SCI microstructural parameters and corrosion rate of steel, particularly under unsaturated conditions. In this work, the effects of rebar arrangement direction (i.e., horizontal and vertical orientations), binder type (i.e., ordinary Portland cement and alkali-activated slag), presence of aggregate, and chloride content, on both the SCI and chloride-induced corrosion rate of steel were systematically investigated and quantified at different relative humidity levels. The results indicated that in comparison with Portland cement counterparts, the reaction products of alkali-activated slag fill the gap under the horizontally oriented steel rebars, favoring more densified SCI microstructure and better corrosion protection. Quantitative analysis reveals that in the unsaturated state, the corrosion rate of steel decreases more slowly in more porous SCI microstructure. An image-based model is proposed to quantitatively link SCI microstructure and corrosion rate of steel, which is applicable to both Portland cement and alkali-activated slag systems in saturated and unsaturated conditions.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"188 ","pages":"Article 107736"},"PeriodicalIF":10.9,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142696506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-25DOI: 10.1016/j.cemconres.2024.107737
Dingqiang Fan , Chunpeng Zhang , Jian-Xin Lu , Ligang Peng , Rui Yu , Chi Sun Poon
Foam concrete encounters a fundamental challenge in balancing lightweight and high strength. Pore optimization is the key to address this problem. This study starts with rheology control to optimize the pore structure of foam concretes, thereby designing high-performance foam concrete (HPFC). X-ray computed tomography was employed to explore the relationship between rheology and pore characteristics, revealing the corresponding control mechanisms. The findings indicated that rheological parameters, particularly viscosity, significantly influenced pore size, uniformity, sphericity, fractal dimension and connectivity. Therefore, there was an optimal viscosity range (1.30 ± 0.15 Pa·s) for achieving the desirable pore structure. Mechanical analysis demonstrated that the viscosity could impact the balance of the added foams under dynamic and static conditions via drag force, resulting in changes to the pore structure. After pore optimization, the HPFCs exhibited high compressive strength (2–3 times higher than normal foam concrete at an equal density) and excellent durability comparable to high-performance concrete.
泡沫混凝土在兼顾轻质和高强度方面遇到了根本性的挑战。孔隙优化是解决这一问题的关键。本研究从流变控制入手，优化泡沫混凝土的孔隙结构，从而设计出高性能泡沫混凝土（HPFC）。研究采用 X 射线计算机断层扫描技术探讨了流变学与孔隙特征之间的关系，揭示了相应的控制机制。研究结果表明，流变参数，尤其是粘度，对孔隙大小、均匀性、球形度、分形维度和连通性有显著影响。因此，有一个最佳粘度范围（1.30 ± 0.15 Pa-s）可实现理想的孔隙结构。机械分析表明，在动态和静态条件下，粘度会通过阻力影响添加泡沫的平衡，从而导致孔隙结构发生变化。孔隙优化后，HPFCs 表现出很高的抗压强度（在密度相同的情况下比普通泡沫混凝土高 2-3 倍）和与高性能混凝土相当的优异耐久性。
{"title":"Rheology dependent pore structure optimization of high-performance foam concrete","authors":"Dingqiang Fan , Chunpeng Zhang , Jian-Xin Lu , Ligang Peng , Rui Yu , Chi Sun Poon","doi":"10.1016/j.cemconres.2024.107737","DOIUrl":"10.1016/j.cemconres.2024.107737","url":null,"abstract":"<div><div>Foam concrete encounters a fundamental challenge in balancing lightweight and high strength. Pore optimization is the key to address this problem. This study starts with rheology control to optimize the pore structure of foam concretes, thereby designing high-performance foam concrete (HPFC). X-ray computed tomography was employed to explore the relationship between rheology and pore characteristics, revealing the corresponding control mechanisms. The findings indicated that rheological parameters, particularly viscosity, significantly influenced pore size, uniformity, sphericity, fractal dimension and connectivity. Therefore, there was an optimal viscosity range (1.30 ± 0.15 Pa·s) for achieving the desirable pore structure. Mechanical analysis demonstrated that the viscosity could impact the balance of the added foams under dynamic and static conditions via drag force, resulting in changes to the pore structure. After pore optimization, the HPFCs exhibited high compressive strength (2–3 times higher than normal foam concrete at an equal density) and excellent durability comparable to high-performance concrete.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"188 ","pages":"Article 107737"},"PeriodicalIF":10.9,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142696507","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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