Pub Date : 2024-12-25DOI: 10.1016/j.cemconcomp.2024.105916
Shuai Bai, Lingbo Yu, Xinchun Guan, Hui Li
The current research on the application of nanomaterials in concrete is mainly carried out under positive-temperature curing conditions, while research under negative-temperature curing conditions is very scarce. This paper investigated the effect of nano-SiO2 on long-term strength and chloride diffusivity of cement pastes cured at negative temperature (-5°C). Thermogravimetric analysis (TGA) confirms that the low-dosage nano-SiO2 can still exert the pozzolanic effect within negative-temperature cement paste even after 120 days. The macro results show that low-dosage nano-SiO2 effectively shortens the curing age required for strength and durability development. It is further proved that compared to the promotion effect of nano-SiO2 on hydration, the optimization of internal pore structure by nano-SiO2 plays the dominant role in shortening the curing age required. Furthermore, it is found that the low sensitivity of strength to the microstructure results in the insignificant effect of nano-SiO2 on the long-term strength. In contrast, nano-SiO2 can effectively improve the long-term chloride permeability resistance through increasing the tortuosity of pore structure and decreasing the critical pore diameter and threshold pore diameter.
{"title":"Experimental study on the effect of nano-SiO2 on long-term properties of negative-temperature cement paste","authors":"Shuai Bai, Lingbo Yu, Xinchun Guan, Hui Li","doi":"10.1016/j.cemconcomp.2024.105916","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105916","url":null,"abstract":"The current research on the application of nanomaterials in concrete is mainly carried out under positive-temperature curing conditions, while research under negative-temperature curing conditions is very scarce. This paper investigated the effect of nano-SiO<sub>2</sub> on long-term strength and chloride diffusivity of cement pastes cured at negative temperature (-5°C). Thermogravimetric analysis (TGA) confirms that the low-dosage nano-SiO<sub>2</sub> can still exert the pozzolanic effect within negative-temperature cement paste even after 120 days. The macro results show that low-dosage nano-SiO<sub>2</sub> effectively shortens the curing age required for strength and durability development. It is further proved that compared to the promotion effect of nano-SiO<sub>2</sub> on hydration, the optimization of internal pore structure by nano-SiO<sub>2</sub> plays the dominant role in shortening the curing age required. Furthermore, it is found that the low sensitivity of strength to the microstructure results in the insignificant effect of nano-SiO<sub>2</sub> on the long-term strength. In contrast, nano-SiO<sub>2</sub> can effectively improve the long-term chloride permeability resistance through increasing the tortuosity of pore structure and decreasing the critical pore diameter and threshold pore diameter.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884324","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 : 2024-12-24DOI: 10.1016/j.cemconcomp.2024.105913
Kevin Jia Le Lee, Kang Hai Tan
Presently, significant attention is directed towards utilisation of recycled plastic waste as an environmentally sustainable substitute for natural aggregate in cementitious concrete materials. This is aimed to bolster the greening endeavours of local construction industry and address the pressing need to improve global plastic recycling rates. Despite extensive literature on different mechanisms underlying various fire responses and spalling behaviour of cementitious materials, it remains unclear if these propositions are applicable to the mechanisms behind the fire response of concrete materials incorporated with polymeric aggregate. Therefore, the key focus of this study is to examine the effect of recycled heterogeneous carbonaceous aggregate (RHCA), recovered from municipal solid waste streams, on fire performance of high strength concrete (HSC). A series of analytical and microscopic tests were carried out at 200, 400, 600 and 800 °C on six HSC mixes containing 0, 10, 20, 30, 40, and 50 % RHCA by volume of natural sand as replacement to address the knowledge gaps. The experimental data shows that incorporation of RHCA resulted in a higher mass loss and lower mechanical properties in residual state. It is revealed that thermal expansion of RHCA below its melting temperature was responsible for creation of interconnected crack network within the concrete system that has direct bearing on the residual physical and mechanical properties of the concrete specimens often subjected to fire conditions. Although explosive spalling is avoided under ISO 834 heating, thermochemical mechanisms based on radical reactions and the Bolland-Gee autoxidation scheme were applied to explain the occurrence of ignition at high RHCA content. Finally, fire load density of concrete mixes with varying amounts of RHCA is quantified and recommended for different occupancies under Eurocode 1 EN1991-1-2.
{"title":"Effects of recycled heterogeneous carbonaceous aggregate on fire performance of high strength concrete","authors":"Kevin Jia Le Lee, Kang Hai Tan","doi":"10.1016/j.cemconcomp.2024.105913","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105913","url":null,"abstract":"Presently, significant attention is directed towards utilisation of recycled plastic waste as an environmentally sustainable substitute for natural aggregate in cementitious concrete materials. This is aimed to bolster the greening endeavours of local construction industry and address the pressing need to improve global plastic recycling rates. Despite extensive literature on different mechanisms underlying various fire responses and spalling behaviour of cementitious materials, it remains unclear if these propositions are applicable to the mechanisms behind the fire response of concrete materials incorporated with polymeric aggregate. Therefore, the key focus of this study is to examine the effect of recycled heterogeneous carbonaceous aggregate (RHCA), recovered from municipal solid waste streams, on fire performance of high strength concrete (HSC). A series of analytical and microscopic tests were carried out at 200, 400, 600 and 800 °C on six HSC mixes containing 0, 10, 20, 30, 40, and 50 % RHCA by volume of natural sand as replacement to address the knowledge gaps. The experimental data shows that incorporation of RHCA resulted in a higher mass loss and lower mechanical properties in residual state. It is revealed that thermal expansion of RHCA below its melting temperature was responsible for creation of interconnected crack network within the concrete system that has direct bearing on the residual physical and mechanical properties of the concrete specimens often subjected to fire conditions. Although explosive spalling is avoided under ISO 834 heating, thermochemical mechanisms based on radical reactions and the Bolland-Gee autoxidation scheme were applied to explain the occurrence of ignition at high RHCA content. Finally, fire load density of concrete mixes with varying amounts of RHCA is quantified and recommended for different occupancies under Eurocode 1 EN1991-1-2.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884326","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 : 2024-12-22DOI: 10.1016/j.cemconcomp.2024.105906
Yu Cui, Zanqun Liu, Ju Huang, Wei Zhang, Yi Wang, Jiahui Zhu, Dehua Deng
The free CaO (FC) in light-burnt MgO due to the impurity of magnesite ores cannot be avoided, and causes the declination of properties of magnesium oxychloride cement (MOC). In order to clearly explain the declination mechanism of MOC properties due to FC, the effect of FC contents on the formation of phase compositions and the compressive strength of MOC pastes were studied in detail. The findings revealed that the addition of FC sharply increased the pH value of MOC pastes, and changed the final compositions of the hardened MOC pastes. Specifically, FC contents more than 4% could cause the formation of phase 5 by the phase 3 transformation at MgO/MgCl2/H2O molar ratio of 3:1:11, and FC contents more than 2% could lead to the formation of phase Mg(OH)2 by phase 5 transformation at MgO/MgCl2/H2O molar ratio of 5:1:13. Consequently, the transformation of phase compositions caused the remarkable declination of compressive strength of MOC pastes. The content of FC should be given attention in the MgO/MgCl2/H2O molar ratio, and the permissible contents of FC should be limited to less than 4% and 2% relevant to the MgO/MgCl2/H2O molar ratios at 3:1:11 and 5:1:13, respectively.
{"title":"Effect of free CaO content on the phase compositions of magnesium oxychloride cement","authors":"Yu Cui, Zanqun Liu, Ju Huang, Wei Zhang, Yi Wang, Jiahui Zhu, Dehua Deng","doi":"10.1016/j.cemconcomp.2024.105906","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105906","url":null,"abstract":"The free CaO (FC) in light-burnt MgO due to the impurity of magnesite ores cannot be avoided, and causes the declination of properties of magnesium oxychloride cement (MOC). In order to clearly explain the declination mechanism of MOC properties due to FC, the effect of FC contents on the formation of phase compositions and the compressive strength of MOC pastes were studied in detail. The findings revealed that the addition of FC sharply increased the pH value of MOC pastes, and changed the final compositions of the hardened MOC pastes. Specifically, FC contents more than 4% could cause the formation of phase 5 by the phase 3 transformation at MgO/MgCl<sub>2</sub>/H<sub>2</sub>O molar ratio of 3:1:11, and FC contents more than 2% could lead to the formation of phase Mg(OH)<sub>2</sub> by phase 5 transformation at MgO/MgCl<sub>2</sub>/H<sub>2</sub>O molar ratio of 5:1:13. Consequently, the transformation of phase compositions caused the remarkable declination of compressive strength of MOC pastes. The content of FC should be given attention in the MgO/MgCl<sub>2</sub>/H<sub>2</sub>O molar ratio, and the permissible contents of FC should be limited to less than 4% and 2% relevant to the MgO/MgCl<sub>2</sub>/H<sub>2</sub>O molar ratios at 3:1:11 and 5:1:13, respectively.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"120 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142870015","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 : 2024-12-20DOI: 10.1016/j.cemconcomp.2024.105908
Xinming Wang, Yufei Yang, Jing Zhong
Internal curing and self-compensation are two different approaches to mitigate autogenous shrinkage, with their own pros and cons. In this study, strategies of internal curing and self-compensation are combined in a single material by pre-absorbing hydrophilic carbon nanotube sponge with L-Serine based carbamate (H-CNTSP@C-Ser). In contrast to the detrimental effects of C-Ser when directly mixed with cement, the autogenous shrinkage and compressive strength of cement can be reduced and enhanced by 81.8% and 44.4%, respectively, with the addition of 0.05 wt.% H-CNTSP@C-Ser, as compared to the control sample. This comparison strongly confirms the importance of the controlled release of C-Ser. After setting, the hydrolysis of the released C-Ser solution pre-absorbed within H-CNTSP promotes the precipitation of CaCO3, which can not only induce expansion for self-compensation of shrinkage, but also promote the formation of C-S-H with a higher modulus, thereby leading to an enhanced compressive strength of cement paste.
{"title":"Novel Strategy for Autogenous Shrinkage Mitigation by combining Internal Curing and Self-compensation: Carbon Nanotube Sponge with Carbamate Solution Absorbed","authors":"Xinming Wang, Yufei Yang, Jing Zhong","doi":"10.1016/j.cemconcomp.2024.105908","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105908","url":null,"abstract":"Internal curing and self-compensation are two different approaches to mitigate autogenous shrinkage, with their own pros and cons. In this study, strategies of internal curing and self-compensation are combined in a single material by pre-absorbing hydrophilic carbon nanotube sponge with L-Serine based carbamate (H-CNTSP@C-Ser). In contrast to the detrimental effects of C-Ser when directly mixed with cement, the autogenous shrinkage and compressive strength of cement can be reduced and enhanced by 81.8% and 44.4%, respectively, with the addition of 0.05 <em>wt.</em>% H-CNTSP@C-Ser, as compared to the control sample. This comparison strongly confirms the importance of the controlled release of C-Ser. After setting, the hydrolysis of the released C-Ser solution pre-absorbed within H-CNTSP promotes the precipitation of CaCO<sub>3</sub>, which can not only induce expansion for self-compensation of shrinkage, but also promote the formation of C-S-H with a higher modulus, thereby leading to an enhanced compressive strength of cement paste.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867104","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 : 2024-12-20DOI: 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}
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