Pub Date : 2024-12-20DOI: 10.1016/j.cemconcomp.2024.105909
T. Neef, M. Kalthoff, S. Müller, C. Morales Cruz, M. Raupach, T. Matschei, V. Mechtcherine
Mineral-impregnated carbon fibers (MCF) introduce an innovative reinforcement approach for creating material-efficient structures. Once cured, MCF display a substantially improved bond with the concrete matrix compared to similar polymer-impregnated textiles. Consequently, these novel composites exhibit increased crack density and more uniform crack distribution under uniaxial tensile load. This article explores the integration of both freshly impregnated and cured MCF into an extrusion process suited for stiff concrete mixtures. It provides insights into the impregnation process of carbon rovings with a mineral suspension and the incorporation of the MCF into the extrusion process. Mechanical characterization of the MCF and the extruded lightweight elements is also detailed, bolstered by visual examinations using computed tomography. Finally, the paper proposes a vision for material-efficient structures composed of extruded and subsequently freely formed MCF-reinforced concrete.
{"title":"Mineral impregnated carbon fibers reinforcement for concrete elements manufactured by extrusion","authors":"T. Neef, M. Kalthoff, S. Müller, C. Morales Cruz, M. Raupach, T. Matschei, V. Mechtcherine","doi":"10.1016/j.cemconcomp.2024.105909","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105909","url":null,"abstract":"Mineral-impregnated carbon fibers (MCF) introduce an innovative reinforcement approach for creating material-efficient structures. Once cured, MCF display a substantially improved bond with the concrete matrix compared to similar polymer-impregnated textiles. Consequently, these novel composites exhibit increased crack density and more uniform crack distribution under uniaxial tensile load. This article explores the integration of both freshly impregnated and cured MCF into an extrusion process suited for stiff concrete mixtures. It provides insights into the impregnation process of carbon rovings with a mineral suspension and the incorporation of the MCF into the extrusion process. Mechanical characterization of the MCF and the extruded lightweight elements is also detailed, bolstered by visual examinations using computed tomography. Finally, the paper proposes a vision for material-efficient structures composed of extruded and subsequently freely formed MCF-reinforced concrete.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"65 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The use of alkaline activator in alkali-activated materials (AAMs) may pose risk of alkali-silica reaction (ASR), and the variations in the mixture design could have great influence on the performance of AAMs system. In this case, this paper investigated the effects of slag fineness (3000 to 8000 cm2/g) and water-to-binder (w/b) ratio (0.5 to 0.8) on ASR behavior of alkali-activated slag (AAS) mortars under accelerated mortar testing conditions as specified in ASTM C1260. The length change, mass gain, microstructure and formation of ASR products were examined to evaluate the degradation caused by ASR. It was found for the first time that slag fineness induces a “pessimum effect” in the ASR expansion of AAS mortars. On the other hand, there is a “pessimum effect” in the influence of w/b ratio on ASR expansion in the early-stage (≤14d), and the induced expansion increased with an increase in w/b ratio in the late-stage (>14d). The mechanism governing the effect of slag fineness and w/b ratio is complicated and cannot be explained solely by the properties of ASR products. This work contributes to the understanding of ASR in AAMs system and could provide a basis for the mixture optimization of AAMs.
{"title":"Understanding the influence of slag fineness and water-to-binder ratio on the alkali-silica reaction in alkali-activated slag mortars","authors":"Wei Wang, Shizhe Zhang, Yamei Zhang, Takafumi Noguchi, Ippei Maruyama","doi":"10.1016/j.cemconcomp.2024.105907","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105907","url":null,"abstract":"The use of alkaline activator in alkali-activated materials (AAMs) may pose risk of alkali-silica reaction (ASR), and the variations in the mixture design could have great influence on the performance of AAMs system. In this case, this paper investigated the effects of slag fineness (3000 to 8000 cm<sup>2</sup>/g) and water-to-binder (w/b) ratio (0.5 to 0.8) on ASR behavior of alkali-activated slag (AAS) mortars under accelerated mortar testing conditions as specified in ASTM C1260. The length change, mass gain, microstructure and formation of ASR products were examined to evaluate the degradation caused by ASR. It was found for the first time that slag fineness induces a “pessimum effect” in the ASR expansion of AAS mortars. On the other hand, there is a “pessimum effect” in the influence of w/b ratio on ASR expansion in the early-stage (≤14d), and the induced expansion increased with an increase in w/b ratio in the late-stage (>14d). The mechanism governing the effect of slag fineness and w/b ratio is complicated and cannot be explained solely by the properties of ASR products. This work contributes to the understanding of ASR in AAMs system and could provide a basis for the mixture optimization of AAMs.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-18DOI: 10.1016/j.cemconcomp.2024.105894
Chandrasekhar Bhojaraju, Claudiane M. Ouellet-Plamondon
In recent years, there has been a growing interest in the use of nanomaterials as additives in various industries, including cement production. Among these materials, carbon-based nanomaterials, such as graphene and graphene oxide, have been extensively studied for their potential applications in cementitious materials. However, recent research has shown that boron nitride nanotubes (BNNT) can offer superior properties compared to their carbon-based counterparts. This study compared the properties of BNNT with those of graphene and graphene oxide when used as additives in cementitious materials. The hydration process of the nanomodified cementitious composite was studied using in situ calorimetry measurements over a period of seven days, and thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and Field Emission Scanning Electron Microscopy (FESEM) over a period of 28 days. These techniques provide insights into the mechanisms of cement hydration and the impact of boron nitride nanotubes on cementitious composites. The results demonstrate that the addition of BNNT significantly reduced the induction period during cement hydration, indicating that BNNT can enhance the reactivity of cement. Furthermore, BNNT accelerate the hydration process because of their high surface area. Phase identification by XRD peaks showed that the BNNT reinforcement could regulate the microstructure of the cementitious composites. These findings suggest that BNNT has the potential to be a more effective and efficient additive in cementitious materials than graphene and graphene oxide. The use of BNNT in cement production can lead to the development of high-performance, durable, and sustainable materials for various construction applications.
{"title":"Boosting cement hydration with boron nitride nanotubes","authors":"Chandrasekhar Bhojaraju, Claudiane M. Ouellet-Plamondon","doi":"10.1016/j.cemconcomp.2024.105894","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105894","url":null,"abstract":"In recent years, there has been a growing interest in the use of nanomaterials as additives in various industries, including cement production. Among these materials, carbon-based nanomaterials, such as graphene and graphene oxide, have been extensively studied for their potential applications in cementitious materials. However, recent research has shown that boron nitride nanotubes (BNNT) can offer superior properties compared to their carbon-based counterparts. This study compared the properties of BNNT with those of graphene and graphene oxide when used as additives in cementitious materials. The hydration process of the nanomodified cementitious composite was studied using in situ calorimetry measurements over a period of seven days, and thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and Field Emission Scanning Electron Microscopy (FESEM) over a period of 28 days. These techniques provide insights into the mechanisms of cement hydration and the impact of boron nitride nanotubes on cementitious composites. The results demonstrate that the addition of BNNT significantly reduced the induction period during cement hydration, indicating that BNNT can enhance the reactivity of cement. Furthermore, BNNT accelerate the hydration process because of their high surface area. Phase identification by XRD peaks showed that the BNNT reinforcement could regulate the microstructure of the cementitious composites. These findings suggest that BNNT has the potential to be a more effective and efficient additive in cementitious materials than graphene and graphene oxide. The use of BNNT in cement production can lead to the development of high-performance, durable, and sustainable materials for various construction applications.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"91 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-18DOI: 10.1016/j.cemconcomp.2024.105902
Yi Jiang, Zihan Ma, Yining Gao, Peiliang Shen, Chi Sun Poon
The construction industry has been facing significant challenges in reducing CO2 emissions. As such, accelerated carbonation has attracted explosive attention in view of its ability to bind CO2 back to construction materials while improving their performance. Water is a decisive factor in carbonation because it bridges the reaction between gaseous CO2 and solid precursors, and three distinct approaches of carbonation have been developed depending on the amount of water present at carbonation. In this paper, specific roles of water in several parallel mechanisms of carbonation are revealed and then a holistic understanding on the impact of water is established by reviewing and comparing the efficiency, mineralogy and microstructure changes of cementitious materials and calcium-based solid wastes after dry, semi-wet, and wet carbonation. The differences in solid phase dissolution, calcium carbonate precipitation and re-crystallization, aluminosilicate polymerization, microstructure rebuilding, pore structure evolution, specific surface area development, etc. at different water availability are highlighted. Additionally, modified carbonation techniques based on different water content are also summarized and discussed. Overall, awareness of water’s impact on carbonation facilitates the efficient and effective production of sustainable construction materials and maximizes the reduction in CO2 emission.
{"title":"A review on the impact of water in accelerated carbonation: implications for producing sustainable construction materials","authors":"Yi Jiang, Zihan Ma, Yining Gao, Peiliang Shen, Chi Sun Poon","doi":"10.1016/j.cemconcomp.2024.105902","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105902","url":null,"abstract":"The construction industry has been facing significant challenges in reducing CO<sub>2</sub> emissions. As such, accelerated carbonation has attracted explosive attention in view of its ability to bind CO<sub>2</sub> back to construction materials while improving their performance. Water is a decisive factor in carbonation because it bridges the reaction between gaseous CO<sub>2</sub> and solid precursors, and three distinct approaches of carbonation have been developed depending on the amount of water present at carbonation. In this paper, specific roles of water in several parallel mechanisms of carbonation are revealed and then a holistic understanding on the impact of water is established by reviewing and comparing the efficiency, mineralogy and microstructure changes of cementitious materials and calcium-based solid wastes after dry, semi-wet, and wet carbonation. The differences in solid phase dissolution, calcium carbonate precipitation and re-crystallization, aluminosilicate polymerization, microstructure rebuilding, pore structure evolution, specific surface area development, etc. at different water availability are highlighted. Additionally, modified carbonation techniques based on different water content are also summarized and discussed. Overall, awareness of water’s impact on carbonation facilitates the efficient and effective production of sustainable construction materials and maximizes the reduction in CO<sub>2</sub> emission.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"74 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-18DOI: 10.1016/j.cemconcomp.2024.105904
Maciej Zajac, Raoul Bremeier, Jan Deja, Magdalena Król, Mohsen Ben Haha
This study investigated composite cements with recycled concrete pastes (RCP) and the carbonated analogue, comparing them to Portland and limestone cements. The carbonation curing resulted in a carbonation degree of around 30%. The presence of supplementary cementitious materials had little impact on the carbonation degree and phase assemblage. Cement pastes consisted of ettringite, calcium carbonate, C-S-H phase and silica gel. This phase assemblage transformed upon further hydration. The alumina-silica gel from cRCP did not contribute significantly to the reactions but modified porosity. The hydrates from RCP carbonated, however did not contributed to the strength evolution. Still, replacing limestone with RCP positively contributes to environmental sustainability by increasing CO2 sequestration. Composite cements had lower strength, but those with carbonated RCP showed higher compressive strength and faster strength evolution. This effect was related to the appreciable porosity distribution compensating for the clinker dilution impact and a fast clinker hydration during the post carbonation curing.
{"title":"Carbonation hardening of Portland cement with recycled supplementary cementitious materials","authors":"Maciej Zajac, Raoul Bremeier, Jan Deja, Magdalena Król, Mohsen Ben Haha","doi":"10.1016/j.cemconcomp.2024.105904","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105904","url":null,"abstract":"This study investigated composite cements with recycled concrete pastes (RCP) and the carbonated analogue, comparing them to Portland and limestone cements. The carbonation curing resulted in a carbonation degree of around 30%. The presence of supplementary cementitious materials had little impact on the carbonation degree and phase assemblage. Cement pastes consisted of ettringite, calcium carbonate, C-S-H phase and silica gel. This phase assemblage transformed upon further hydration. The alumina-silica gel from cRCP did not contribute significantly to the reactions but modified porosity. The hydrates from RCP carbonated, however did not contributed to the strength evolution. Still, replacing limestone with RCP positively contributes to environmental sustainability by increasing CO<sub>2</sub> sequestration. Composite cements had lower strength, but those with carbonated RCP showed higher compressive strength and faster strength evolution. This effect was related to the appreciable porosity distribution compensating for the clinker dilution impact and a fast clinker hydration during the post carbonation curing.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-18DOI: 10.1016/j.cemconcomp.2024.105901
Qinglong Qin, Boyang Su, Zihan Ma, Kai Cui, Weiwei Chen, Peiliang Shen, Qi Zhao, Chi Sun Poon
CO2 curing cementitious materials shows promise as a method to both reduce and sequestrate CO2, nonetheless, it results in the formation of a gradient structure in them. In this study, the mechanical behavior, damage mode and inhomogeneity of carbonated cement pastes are investigated, aiming to establish the intrinsic link between their damage and inhomogeneity. The results indicated that carbonated cement pastes exhibit pronounced stress instability and brittle damage at low strengths, closely linked to their inhomogeneity. Moreover, carbonated cement paste is an inhomogeneous mass with a gradient structure. It displays a three-layer structure comprising an outermost, intermediate, and innermost layer. The outermost layer primarily comprises calcite, with minor amounts of aragonite and silica gel. Furthermore, its porosity, average micro-hardness, and elastic modulus are 26.81%, 58.62 HV, and 84.66 GPa, respectively. The intermediate layer consists mainly of calcite, aragonite, calcium hydroxide, C-S-H gel, and silica gel, with porosity, average micro-hardness, and elastic modulus of 28.46%, 37.21 HV, and 53.74 GPa, respectively. The innermost layer is composed of C-S-H gel, calcium hydroxide, calcite, aragonite, calcium hydroxide, and silica gel, with porosity, average micro-hardness, and elastic modulus values of 29.29%, 25.73 HV, and 58.87 GPa, respectively. The damage in cement pastes with a low degree of carbonation primarily arises from mixed shear-tensile cracks, whereas in cement pastes with a high degree of carbonation, tensile cracks are the predominant cause of damage.
{"title":"Damage characterization of carbonated cement pastes with a gradient structure","authors":"Qinglong Qin, Boyang Su, Zihan Ma, Kai Cui, Weiwei Chen, Peiliang Shen, Qi Zhao, Chi Sun Poon","doi":"10.1016/j.cemconcomp.2024.105901","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105901","url":null,"abstract":"CO<sub>2</sub> curing cementitious materials shows promise as a method to both reduce and sequestrate CO<sub>2</sub>, nonetheless, it results in the formation of a gradient structure in them. In this study, the mechanical behavior, damage mode and inhomogeneity of carbonated cement pastes are investigated, aiming to establish the intrinsic link between their damage and inhomogeneity. The results indicated that carbonated cement pastes exhibit pronounced stress instability and brittle damage at low strengths, closely linked to their inhomogeneity. Moreover, carbonated cement paste is an inhomogeneous mass with a gradient structure. It displays a three-layer structure comprising an outermost, intermediate, and innermost layer. The outermost layer primarily comprises calcite, with minor amounts of aragonite and silica gel. Furthermore, its porosity, average micro-hardness, and elastic modulus are 26.81%, 58.62 HV, and 84.66 GPa, respectively. The intermediate layer consists mainly of calcite, aragonite, calcium hydroxide, C-S-H gel, and silica gel, with porosity, average micro-hardness, and elastic modulus of 28.46%, 37.21 HV, and 53.74 GPa, respectively. The innermost layer is composed of C-S-H gel, calcium hydroxide, calcite, aragonite, calcium hydroxide, and silica gel, with porosity, average micro-hardness, and elastic modulus values of 29.29%, 25.73 HV, and 58.87 GPa, respectively. The damage in cement pastes with a low degree of carbonation primarily arises from mixed shear-tensile cracks, whereas in cement pastes with a high degree of carbonation, tensile cracks are the predominant cause of damage.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"147 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To promote the application of carbonated recycled concrete powder (CRP), it is vital to thoroughly understand the performance of recycled concrete powder (RP) during the carbonation process. This paper presents an experimental study on the multiscale microstructure evolution of CRP and its chemical reactivity development during gas-solid carbonation. The phase transformation, nanostructure and reactivity evolution were investigated using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), 29Si nuclear magnetic resonance (NMR) and zeta potential test. Scanning electron microscope and energy-dispersive spectroscopy (SEM-EDS), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) were employed to study the microstructural characteristics. Results indicate that portlandite, ettringite, and unhydrated clinker were carbonated into CaCO3 and alumina gel within 1d, while the C-S-H subsequently underwent decalcification, yielding silica gel and nano CaCO3. Regarding microstructure, calcium redistributes during carbonation, and silica phase undergoes polymerization from a nanoscale point of view. The CaCO3 derived from portlandite firstly formed and refine the pores, followed by the outward distribution of later-generated silica gel and nano calcium carbonate from C-S-H due to space limitations within the particle. The initially formed CaCO3 can chemically absorb Ca2+ in cement paste to facilitate the nucleation and growth of C-S-H, while the highly reactive silica gel obtained in later stage can further promote the formation of C-S-H. This study provides theoretical and technological support to improve the efficiency of carbonation processes and advance their engineering applications.
{"title":"Multiscale microstructure and reactivity evolution of recycled concrete fines under gas-solid carbonation","authors":"Xiaowei Ouyang, Xiaofeng Li, Jiaming Li, Yuwei Ma, Mingzhong Zhang, Zongjin Li, Jiyang Fu","doi":"10.1016/j.cemconcomp.2024.105903","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105903","url":null,"abstract":"To promote the application of carbonated recycled concrete powder (CRP), it is vital to thoroughly understand the performance of recycled concrete powder (RP) during the carbonation process. This paper presents an experimental study on the multiscale microstructure evolution of CRP and its chemical reactivity development during gas-solid carbonation. The phase transformation, nanostructure and reactivity evolution were investigated using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), <sup>29</sup>Si nuclear magnetic resonance (NMR) and zeta potential test. Scanning electron microscope and energy-dispersive spectroscopy (SEM-EDS), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) were employed to study the microstructural characteristics. Results indicate that portlandite, ettringite, and unhydrated clinker were carbonated into CaCO<sub>3</sub> and alumina gel within 1d, while the C-S-H subsequently underwent decalcification, yielding silica gel and nano CaCO<sub>3</sub>. Regarding microstructure, calcium redistributes during carbonation, and silica phase undergoes polymerization from a nanoscale point of view. The CaCO<sub>3</sub> derived from portlandite firstly formed and refine the pores, followed by the outward distribution of later-generated silica gel and nano calcium carbonate from C-S-H due to space limitations within the particle. The initially formed CaCO<sub>3</sub> can chemically absorb Ca<sup>2+</sup> in cement paste to facilitate the nucleation and growth of C-S-H, while the highly reactive silica gel obtained in later stage can further promote the formation of C-S-H. This study provides theoretical and technological support to improve the efficiency of carbonation processes and advance their engineering applications.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Assessing the permeability of concrete is crucial as it governs the transport of aggressive agents, such as chlorides and carbon dioxide, which are key factors in the degradation mechanisms. Moreover, concrete’s permeability constitutes an essential input parameter for durability models. Concrete’s permeability can be measured directly (by experimental methods) or indirectly by fitting a transport model to saturation degree profiles. In this paper, we introduce a novel indirect method for estimating the permeability by monitoring the saturation degree profiles with embedded resistivity sensors. These embedded resistivity sensors are used for the evaluation of the saturation degree profiles over time during two experiments: drying and imbibition with tap water. Firstly, measured resistivity profiles are converted to saturation degree profiles, using a calibration curve established on concrete cores of the same formulation. Concrete’s permeability is then estimated by fitting a hydric transport model to the experimental saturation degree profiles. Permeability values estimated using the embedded sensor are compared to those obtained by two reference methods: assessing the mass loss of a non-monitored specimen subjected to drying and saturation degree profiles obtained by gammadensimetry measurements. The permeability values obtained with the monitoring method are consistent for drying and imbibition experiments and fall within the range of values found in the literature. This is very promising for the continuous monitoring of concrete by embedded resistivity sensors.
{"title":"Monitoring of drying and imbibition of concrete using embedded resistivity sensors for the estimation of permeability","authors":"Marie-Ange Eid, Nicolas Reuge, Géraldine Villain, Stéphanie Bonnet, Sérgio Palma Lopes","doi":"10.1016/j.cemconcomp.2024.105900","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105900","url":null,"abstract":"Assessing the permeability of concrete is crucial as it governs the transport of aggressive agents, such as chlorides and carbon dioxide, which are key factors in the degradation mechanisms. Moreover, concrete’s permeability constitutes an essential input parameter for durability models. Concrete’s permeability can be measured directly (by experimental methods) or indirectly by fitting a transport model to saturation degree profiles. In this paper, we introduce a novel indirect method for estimating the permeability by monitoring the saturation degree profiles with embedded resistivity sensors. These embedded resistivity sensors are used for the evaluation of the saturation degree profiles over time during two experiments: drying and imbibition with tap water. Firstly, measured resistivity profiles are converted to saturation degree profiles, using a calibration curve established on concrete cores of the same formulation. Concrete’s permeability is then estimated by fitting a hydric transport model to the experimental saturation degree profiles. Permeability values estimated using the embedded sensor are compared to those obtained by two reference methods: assessing the mass loss of a non-monitored specimen subjected to drying and saturation degree profiles obtained by gammadensimetry measurements. The permeability values obtained with the monitoring method are consistent for drying and imbibition experiments and fall within the range of values found in the literature. This is very promising for the continuous monitoring of concrete by embedded resistivity sensors.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-17DOI: 10.1016/j.cemconcomp.2024.105896
Rashed Alarrak, Alexander S. Brand
This research investigated the mechanical performance of Functionally Graded Fiber-Reinforced Concrete (FG-FRC) produced via extrusion with a targeted fiber injection. Flexural toughness was assessed using a modified ASTM C1609, and fracture properties were analyzed through implementation of the two-parameter fracture model. The study introduced an innovative targeted fiber injection technique using a conveyor system, tailored for the integration of high-stiffness steel fibers into the mortar prior to extrusion. This method permits the use of fibers in more extrusion systems, since the fibers cannot jam in the pump. The research utilized digital image correlation to observe the full displacement field, allowing for an in-depth examination of crack propagation and strain localization. Additionally, X-ray computed tomography was employed to analyze fiber dosage and distribution within the FG-FRC layers. Results indicated that the targeted fiber injection method facilitated effective fiber distribution within FG-FRC layers, leading to enhanced mechanical performance through fiber dosage’s optimization.
本研究调查了通过定向纤维注入挤压法生产的功能级配纤维增强混凝土（FG-FRC）的机械性能。采用修改后的 ASTM C1609 评估了挠曲韧性，并通过实施双参数断裂模型分析了断裂性能。研究采用了一种创新的定向纤维注射技术，该技术使用输送系统，专门用于在挤压之前将高刚度钢纤维整合到砂浆中。这种方法允许在更多的挤压系统中使用纤维，因为纤维不会卡在泵中。该研究利用数字图像相关技术观察整个位移场，从而深入研究裂纹扩展和应变定位。此外，还采用了 X 射线计算机断层扫描技术来分析 FG-FRC 层内的纤维用量和分布情况。结果表明，有针对性的纤维注入方法促进了纤维在 FG-FRC 层内的有效分布，通过优化纤维用量提高了机械性能。
{"title":"Mechanical Performance of Extruded Functionally Graded Fiber-Reinforced Mortar with Targeted Fiber Injection","authors":"Rashed Alarrak, Alexander S. Brand","doi":"10.1016/j.cemconcomp.2024.105896","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105896","url":null,"abstract":"This research investigated the mechanical performance of Functionally Graded Fiber-Reinforced Concrete (FG-FRC) produced <em>via</em> extrusion with a targeted fiber injection. Flexural toughness was assessed using a modified ASTM C1609, and fracture properties were analyzed through implementation of the two-parameter fracture model. The study introduced an innovative targeted fiber injection technique using a conveyor system, tailored for the integration of high-stiffness steel fibers into the mortar prior to extrusion. This method permits the use of fibers in more extrusion systems, since the fibers cannot jam in the pump. The research utilized digital image correlation to observe the full displacement field, allowing for an in-depth examination of crack propagation and strain localization. Additionally, X-ray computed tomography was employed to analyze fiber dosage and distribution within the FG-FRC layers. Results indicated that the targeted fiber injection method facilitated effective fiber distribution within FG-FRC layers, leading to enhanced mechanical performance through fiber dosage’s optimization.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"97 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Colloidal nano silica (CNS) demonstrated positive effects in enhancing the water stability of magnesium phosphate cement (MPC), and the underlying mechanism was investigated systematically in this paper. The experimental results showed that the nucleation effect of CNS accelerated the intermediate phase transition process and significantly enhanced the struvite early formation rate of MPC. Moreover, the addition of CNS led to a shift from macropore to gel pores observed from pore size distribution. Notably, the filling effect of CNS and the formation of novel hydration products were identified as critical factors in enhancing water stability and optimizing pore structure. Simulation experiments provided further validation that CNS could directly react with dead-burnt magnesium oxide to generate a novel gel phase-magnesium silicate hydrate (M-S-H) which confirmed a possible hydration reaction of silica in MPC.
{"title":"Water stability improvement and mechanism of magnesium phosphate cement modified by colloidal nano silica","authors":"Xingyu Gan, Chao Li, Haiming Zhang, Yali Li, Laibo Li, Lingchao Lu","doi":"10.1016/j.cemconcomp.2024.105898","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105898","url":null,"abstract":"Colloidal nano silica (CNS) demonstrated positive effects in enhancing the water stability of magnesium phosphate cement (MPC), and the underlying mechanism was investigated systematically in this paper. The experimental results showed that the nucleation effect of CNS accelerated the intermediate phase transition process and significantly enhanced the struvite early formation rate of MPC. Moreover, the addition of CNS led to a shift from macropore to gel pores observed from pore size distribution. Notably, the filling effect of CNS and the formation of novel hydration products were identified as critical factors in enhancing water stability and optimizing pore structure. Simulation experiments provided further validation that CNS could directly react with dead-burnt magnesium oxide to generate a novel gel phase-magnesium silicate hydrate (M-S-H) which confirmed a possible hydration reaction of silica in MPC.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142832347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：