Renan P. Salvador, R. Serafini, D. Rambo, Alessandra S. Sant'Anna, V. A. Quarcioni, Antonio D. Figueiredo
This paper presents an investigation on the effect of external sulfate attack (ESA) on the mechanical and microstructural properties of steel fiber-reinforced sprayed concrete (SFRSC). Crimped carbon steel fibers, 40 mm-long, were used as reinforcement in three different mixtures with specified fiber contents of 30 kg/m³, 60 kg/m³ and 90 kg/m³. Cylindrical specimens, drilled from SFRSC panels, were subjected to sulfate attack for up to 270 days. Double-punch tests (DPT) were used to determine the matrix crack strength and the post-crack tensile strength of the SFRSC. The effective fiber content of each specimen was determined by inductive tests and subsequently correlated with the mechanical results. Scanning electron microscopy (SEM) was used to evaluate the phases formed in the concrete pores during the sulfate attack. Results indicated that fiber reinforcement may reduce cracking due to ESA.
{"title":"Effect of external sulfate attack on the tensile properties of fiber-reinforced sprayed concrete","authors":"Renan P. Salvador, R. Serafini, D. Rambo, Alessandra S. Sant'Anna, V. A. Quarcioni, Antonio D. Figueiredo","doi":"10.1680/jmacr.23.00251","DOIUrl":"https://doi.org/10.1680/jmacr.23.00251","url":null,"abstract":"This paper presents an investigation on the effect of external sulfate attack (ESA) on the mechanical and microstructural properties of steel fiber-reinforced sprayed concrete (SFRSC). Crimped carbon steel fibers, 40 mm-long, were used as reinforcement in three different mixtures with specified fiber contents of 30 kg/m³, 60 kg/m³ and 90 kg/m³. Cylindrical specimens, drilled from SFRSC panels, were subjected to sulfate attack for up to 270 days. Double-punch tests (DPT) were used to determine the matrix crack strength and the post-crack tensile strength of the SFRSC. The effective fiber content of each specimen was determined by inductive tests and subsequently correlated with the mechanical results. Scanning electron microscopy (SEM) was used to evaluate the phases formed in the concrete pores during the sulfate attack. Results indicated that fiber reinforcement may reduce cracking due to ESA.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139960415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reactive Powder Concrete (RPC) is used to create high-rise buildings, thermal power plants, nuclear power plants, and footbridges worldwide. RPC performance at high temperatures and retention periods must be assessed. In the present study, RPC (110 MPa) samples were prepared with different fiber verities at an optimum fiber dosage of 0.5% by weight of cement. The fibers used in the present study are polypropylene fibers, polyester fibers, and a combination of polypropylene and polyester fibers with 0.5% fiber dosage. The fiber-reinforced RPC was exposed to elevated temperatures ranging from 200°C to 800°C with different retention periods such as 30, 60, 90 and 120 minutes. The evaluation includes determining remaining physical characteristics like color change, fracture formation, weight loss, and residual mechanical strength like reduced compressive strength. Also used for non-destructive testing was ultrasonic pulse velocity. Water absorption of Reactive Powder Concrete (RPC) samples after different exposure durations has been compared to diverse RPC mixes with different fiber kinds. Scanning Electron Microscopes were used to observe microstructure and assess deuteriation of hydrated substances at extreme temperatures with varying retention times. Results demonstrate increased strength for all fiber-reinforced RPC varieties at 200°C for up to 120 minutes. The strength was raised at 400°C for 30 minutes under retention. All retention durations showed a decrease in strength for fiber-reinforced RPC at 600°C and 800°C. RPC with polyester fiber has 10-15% greater residual strength than other fibers during 600-800°C retention durations. Polypropelene fiber reinforced RPC absorbs 6-12% more water than polyester and mixed fibers after 120 minutes at 800°C.
{"title":"Performance of reactive powder concrete with different fiber varieties at higher temperatures and retention periods","authors":"Parameshwar Hiremath","doi":"10.1680/jmacr.23.00191","DOIUrl":"https://doi.org/10.1680/jmacr.23.00191","url":null,"abstract":"Reactive Powder Concrete (RPC) is used to create high-rise buildings, thermal power plants, nuclear power plants, and footbridges worldwide. RPC performance at high temperatures and retention periods must be assessed. In the present study, RPC (110 MPa) samples were prepared with different fiber verities at an optimum fiber dosage of 0.5% by weight of cement. The fibers used in the present study are polypropylene fibers, polyester fibers, and a combination of polypropylene and polyester fibers with 0.5% fiber dosage. The fiber-reinforced RPC was exposed to elevated temperatures ranging from 200°C to 800°C with different retention periods such as 30, 60, 90 and 120 minutes. The evaluation includes determining remaining physical characteristics like color change, fracture formation, weight loss, and residual mechanical strength like reduced compressive strength. Also used for non-destructive testing was ultrasonic pulse velocity. Water absorption of Reactive Powder Concrete (RPC) samples after different exposure durations has been compared to diverse RPC mixes with different fiber kinds. Scanning Electron Microscopes were used to observe microstructure and assess deuteriation of hydrated substances at extreme temperatures with varying retention times. Results demonstrate increased strength for all fiber-reinforced RPC varieties at 200°C for up to 120 minutes. The strength was raised at 400°C for 30 minutes under retention. All retention durations showed a decrease in strength for fiber-reinforced RPC at 600°C and 800°C. RPC with polyester fiber has 10-15% greater residual strength than other fibers during 600-800°C retention durations. Polypropelene fiber reinforced RPC absorbs 6-12% more water than polyester and mixed fibers after 120 minutes at 800°C.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139863322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reactive Powder Concrete (RPC) is used to create high-rise buildings, thermal power plants, nuclear power plants, and footbridges worldwide. RPC performance at high temperatures and retention periods must be assessed. In the present study, RPC (110 MPa) samples were prepared with different fiber verities at an optimum fiber dosage of 0.5% by weight of cement. The fibers used in the present study are polypropylene fibers, polyester fibers, and a combination of polypropylene and polyester fibers with 0.5% fiber dosage. The fiber-reinforced RPC was exposed to elevated temperatures ranging from 200°C to 800°C with different retention periods such as 30, 60, 90 and 120 minutes. The evaluation includes determining remaining physical characteristics like color change, fracture formation, weight loss, and residual mechanical strength like reduced compressive strength. Also used for non-destructive testing was ultrasonic pulse velocity. Water absorption of Reactive Powder Concrete (RPC) samples after different exposure durations has been compared to diverse RPC mixes with different fiber kinds. Scanning Electron Microscopes were used to observe microstructure and assess deuteriation of hydrated substances at extreme temperatures with varying retention times. Results demonstrate increased strength for all fiber-reinforced RPC varieties at 200°C for up to 120 minutes. The strength was raised at 400°C for 30 minutes under retention. All retention durations showed a decrease in strength for fiber-reinforced RPC at 600°C and 800°C. RPC with polyester fiber has 10-15% greater residual strength than other fibers during 600-800°C retention durations. Polypropelene fiber reinforced RPC absorbs 6-12% more water than polyester and mixed fibers after 120 minutes at 800°C.
{"title":"Performance of reactive powder concrete with different fiber varieties at higher temperatures and retention periods","authors":"Parameshwar Hiremath","doi":"10.1680/jmacr.23.00191","DOIUrl":"https://doi.org/10.1680/jmacr.23.00191","url":null,"abstract":"Reactive Powder Concrete (RPC) is used to create high-rise buildings, thermal power plants, nuclear power plants, and footbridges worldwide. RPC performance at high temperatures and retention periods must be assessed. In the present study, RPC (110 MPa) samples were prepared with different fiber verities at an optimum fiber dosage of 0.5% by weight of cement. The fibers used in the present study are polypropylene fibers, polyester fibers, and a combination of polypropylene and polyester fibers with 0.5% fiber dosage. The fiber-reinforced RPC was exposed to elevated temperatures ranging from 200°C to 800°C with different retention periods such as 30, 60, 90 and 120 minutes. The evaluation includes determining remaining physical characteristics like color change, fracture formation, weight loss, and residual mechanical strength like reduced compressive strength. Also used for non-destructive testing was ultrasonic pulse velocity. Water absorption of Reactive Powder Concrete (RPC) samples after different exposure durations has been compared to diverse RPC mixes with different fiber kinds. Scanning Electron Microscopes were used to observe microstructure and assess deuteriation of hydrated substances at extreme temperatures with varying retention times. Results demonstrate increased strength for all fiber-reinforced RPC varieties at 200°C for up to 120 minutes. The strength was raised at 400°C for 30 minutes under retention. All retention durations showed a decrease in strength for fiber-reinforced RPC at 600°C and 800°C. RPC with polyester fiber has 10-15% greater residual strength than other fibers during 600-800°C retention durations. Polypropelene fiber reinforced RPC absorbs 6-12% more water than polyester and mixed fibers after 120 minutes at 800°C.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139803114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The influence of the volume fraction of steel fibers, polyvinyl alcohol (PVA) fibers and their hybrid fibers on the mechanical and fracture mechanical properties of ultra-high performance concrete (UHPC) was studied in this paper. To analyze the synergistic effect of steel fibers and PVA fibers on the deformation properties of UHPC, the gain ratio of mechanical parameters of hybrid fibers reinforced UHPC to steel fibers reinforced UHPC, obtained by two ways, equal total fibers volume fraction and equal steel fibers volume fraction. The results show that steel fibers and PVA fibers reduce the compressive strength of UHPC to some extent, and with the increasing of fibers volume fraction, the flexural-compressive ratio and tension-compression ratio increase gradually. The fracture mechanical properties of fibers reinforced UHPC were significantly is improved by the participation of steel fibers and PVA fibers, and the latter are superior to former in improving the deformation properties of UHPC. Except compressive strength, the mechanical parameters gain ratio of hybrid fibers UHPC to steel fibers UHPC calculated with equal steel fibers volume fraction is higher than the corresponding results of the equal total fibers volume fraction, which indicates that 0.25 v% PVA fibers as the modified component is mixed with steel fibers reinforced UHPC, can further improve its bending tensile and fracture mechanical properties.
{"title":"Synergism of steel fibers and polyvinyl alcohol fibers on the fracture and mechanical properties of ultra-high performance concrete","authors":"Junxia Liu, Shujie Zang, Fei Yang","doi":"10.1680/jmacr.23.00130","DOIUrl":"https://doi.org/10.1680/jmacr.23.00130","url":null,"abstract":"The influence of the volume fraction of steel fibers, polyvinyl alcohol (PVA) fibers and their hybrid fibers on the mechanical and fracture mechanical properties of ultra-high performance concrete (UHPC) was studied in this paper. To analyze the synergistic effect of steel fibers and PVA fibers on the deformation properties of UHPC, the gain ratio of mechanical parameters of hybrid fibers reinforced UHPC to steel fibers reinforced UHPC, obtained by two ways, equal total fibers volume fraction and equal steel fibers volume fraction. The results show that steel fibers and PVA fibers reduce the compressive strength of UHPC to some extent, and with the increasing of fibers volume fraction, the flexural-compressive ratio and tension-compression ratio increase gradually. The fracture mechanical properties of fibers reinforced UHPC were significantly is improved by the participation of steel fibers and PVA fibers, and the latter are superior to former in improving the deformation properties of UHPC. Except compressive strength, the mechanical parameters gain ratio of hybrid fibers UHPC to steel fibers UHPC calculated with equal steel fibers volume fraction is higher than the corresponding results of the equal total fibers volume fraction, which indicates that 0.25 v% PVA fibers as the modified component is mixed with steel fibers reinforced UHPC, can further improve its bending tensile and fracture mechanical properties.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139885413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Four concrete types were experimentally investigated using different fine aggregates as follows: natural river sand (M20RS), artificial crushed sand (M20CS), artificial gravel sand (M20GS), and hybrid sand (M20HS) containing 50% river sand and 50% gravel sand by mass. First, there were little differences in both compressive strength and elastic modulus of the concretes (less than 6.4%). Second, compared to M20RS using river sand, the concretes using artificial sands positively demonstrated their higher flexural strengths (3.5-11.1%) and splitting strengths (4.4-12.8%) at 28-day age. In contrast, they negatively revealed their lower workabilities (21.4-35.7%), water permeation resistance (34.3-53.7%), and abrasion resistance (2.9-20.6%). Third, the compressive, flexural, and splitting strength of the concretes increased with time under water curing. Under sulfate attack, the compressive strengths of the concretes were observed to enhance at 56-day age but reduced at 90-day age. The reductions in compressive strengths owing to sulfate attack were 2.6-7.7% at 56-day age and 11.8-24.4% at 90-day age, in comparison to water curing. Finally, the Weibull distribution analysis was performed to explore the the effect of fine aggregate types on concrete strength sensitivity.
{"title":"Comparative fresh and hardened performances of concrete in using various artificial and natural sands","authors":"D. Nguyen, Duy-Liem Nguyen","doi":"10.1680/jmacr.23.00051","DOIUrl":"https://doi.org/10.1680/jmacr.23.00051","url":null,"abstract":"Four concrete types were experimentally investigated using different fine aggregates as follows: natural river sand (M20RS), artificial crushed sand (M20CS), artificial gravel sand (M20GS), and hybrid sand (M20HS) containing 50% river sand and 50% gravel sand by mass. First, there were little differences in both compressive strength and elastic modulus of the concretes (less than 6.4%). Second, compared to M20RS using river sand, the concretes using artificial sands positively demonstrated their higher flexural strengths (3.5-11.1%) and splitting strengths (4.4-12.8%) at 28-day age. In contrast, they negatively revealed their lower workabilities (21.4-35.7%), water permeation resistance (34.3-53.7%), and abrasion resistance (2.9-20.6%). Third, the compressive, flexural, and splitting strength of the concretes increased with time under water curing. Under sulfate attack, the compressive strengths of the concretes were observed to enhance at 56-day age but reduced at 90-day age. The reductions in compressive strengths owing to sulfate attack were 2.6-7.7% at 56-day age and 11.8-24.4% at 90-day age, in comparison to water curing. Finally, the Weibull distribution analysis was performed to explore the the effect of fine aggregate types on concrete strength sensitivity.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139821890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The influence of the volume fraction of steel fibers, polyvinyl alcohol (PVA) fibers and their hybrid fibers on the mechanical and fracture mechanical properties of ultra-high performance concrete (UHPC) was studied in this paper. To analyze the synergistic effect of steel fibers and PVA fibers on the deformation properties of UHPC, the gain ratio of mechanical parameters of hybrid fibers reinforced UHPC to steel fibers reinforced UHPC, obtained by two ways, equal total fibers volume fraction and equal steel fibers volume fraction. The results show that steel fibers and PVA fibers reduce the compressive strength of UHPC to some extent, and with the increasing of fibers volume fraction, the flexural-compressive ratio and tension-compression ratio increase gradually. The fracture mechanical properties of fibers reinforced UHPC were significantly is improved by the participation of steel fibers and PVA fibers, and the latter are superior to former in improving the deformation properties of UHPC. Except compressive strength, the mechanical parameters gain ratio of hybrid fibers UHPC to steel fibers UHPC calculated with equal steel fibers volume fraction is higher than the corresponding results of the equal total fibers volume fraction, which indicates that 0.25 v% PVA fibers as the modified component is mixed with steel fibers reinforced UHPC, can further improve its bending tensile and fracture mechanical properties.
{"title":"Synergism of steel fibers and polyvinyl alcohol fibers on the fracture and mechanical properties of ultra-high performance concrete","authors":"Junxia Liu, Shujie Zang, Fei Yang","doi":"10.1680/jmacr.23.00130","DOIUrl":"https://doi.org/10.1680/jmacr.23.00130","url":null,"abstract":"The influence of the volume fraction of steel fibers, polyvinyl alcohol (PVA) fibers and their hybrid fibers on the mechanical and fracture mechanical properties of ultra-high performance concrete (UHPC) was studied in this paper. To analyze the synergistic effect of steel fibers and PVA fibers on the deformation properties of UHPC, the gain ratio of mechanical parameters of hybrid fibers reinforced UHPC to steel fibers reinforced UHPC, obtained by two ways, equal total fibers volume fraction and equal steel fibers volume fraction. The results show that steel fibers and PVA fibers reduce the compressive strength of UHPC to some extent, and with the increasing of fibers volume fraction, the flexural-compressive ratio and tension-compression ratio increase gradually. The fracture mechanical properties of fibers reinforced UHPC were significantly is improved by the participation of steel fibers and PVA fibers, and the latter are superior to former in improving the deformation properties of UHPC. Except compressive strength, the mechanical parameters gain ratio of hybrid fibers UHPC to steel fibers UHPC calculated with equal steel fibers volume fraction is higher than the corresponding results of the equal total fibers volume fraction, which indicates that 0.25 v% PVA fibers as the modified component is mixed with steel fibers reinforced UHPC, can further improve its bending tensile and fracture mechanical properties.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139825447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Four concrete types were experimentally investigated using different fine aggregates as follows: natural river sand (M20RS), artificial crushed sand (M20CS), artificial gravel sand (M20GS), and hybrid sand (M20HS) containing 50% river sand and 50% gravel sand by mass. First, there were little differences in both compressive strength and elastic modulus of the concretes (less than 6.4%). Second, compared to M20RS using river sand, the concretes using artificial sands positively demonstrated their higher flexural strengths (3.5-11.1%) and splitting strengths (4.4-12.8%) at 28-day age. In contrast, they negatively revealed their lower workabilities (21.4-35.7%), water permeation resistance (34.3-53.7%), and abrasion resistance (2.9-20.6%). Third, the compressive, flexural, and splitting strength of the concretes increased with time under water curing. Under sulfate attack, the compressive strengths of the concretes were observed to enhance at 56-day age but reduced at 90-day age. The reductions in compressive strengths owing to sulfate attack were 2.6-7.7% at 56-day age and 11.8-24.4% at 90-day age, in comparison to water curing. Finally, the Weibull distribution analysis was performed to explore the the effect of fine aggregate types on concrete strength sensitivity.
{"title":"Comparative fresh and hardened performances of concrete in using various artificial and natural sands","authors":"D. Nguyen, Duy-Liem Nguyen","doi":"10.1680/jmacr.23.00051","DOIUrl":"https://doi.org/10.1680/jmacr.23.00051","url":null,"abstract":"Four concrete types were experimentally investigated using different fine aggregates as follows: natural river sand (M20RS), artificial crushed sand (M20CS), artificial gravel sand (M20GS), and hybrid sand (M20HS) containing 50% river sand and 50% gravel sand by mass. First, there were little differences in both compressive strength and elastic modulus of the concretes (less than 6.4%). Second, compared to M20RS using river sand, the concretes using artificial sands positively demonstrated their higher flexural strengths (3.5-11.1%) and splitting strengths (4.4-12.8%) at 28-day age. In contrast, they negatively revealed their lower workabilities (21.4-35.7%), water permeation resistance (34.3-53.7%), and abrasion resistance (2.9-20.6%). Third, the compressive, flexural, and splitting strength of the concretes increased with time under water curing. Under sulfate attack, the compressive strengths of the concretes were observed to enhance at 56-day age but reduced at 90-day age. The reductions in compressive strengths owing to sulfate attack were 2.6-7.7% at 56-day age and 11.8-24.4% at 90-day age, in comparison to water curing. Finally, the Weibull distribution analysis was performed to explore the the effect of fine aggregate types on concrete strength sensitivity.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139881791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wan Zhang, Zhihong Wu, Wang Huang, Jiawei Wang, Yuexin Pan, Zhishun Li, Shufang Ren, Hongjin Xu
The alkali-free liquid accelerator (ALSF) was prepared with aluminum sulfate and aluminum formate as the main components. The effects of ALSF on the setting of paste and the mechanical strength of mortar were studied, and the impact of ALSF on the early hydration behavior and hydration products of paste were investigated by isothermal calorimeter analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The results show that ALSF is excellent for the rapid setting and hardening of the cement. When the content of ALSF was 8 wt%, the initial setting time and final setting time of paste were 85 s and 180 s, respectively, and the 1 d and 28 d strengths of mortar were 9.52 MPa and 44.42 MPa, respectively. ALSF can accelerate the dissolution and hydration of C3A and C3S and promote the formation of 3CaO·Al2O3·3CaSO4·32H2O (ettringite), AFt formate, and portlandite.
{"title":"Accelerating strength development of cementitious mixtures using aluminum sulfate liquid accelerator with aluminium formate","authors":"Wan Zhang, Zhihong Wu, Wang Huang, Jiawei Wang, Yuexin Pan, Zhishun Li, Shufang Ren, Hongjin Xu","doi":"10.1680/jmacr.23.00170","DOIUrl":"https://doi.org/10.1680/jmacr.23.00170","url":null,"abstract":"The alkali-free liquid accelerator (ALSF) was prepared with aluminum sulfate and aluminum formate as the main components. The effects of ALSF on the setting of paste and the mechanical strength of mortar were studied, and the impact of ALSF on the early hydration behavior and hydration products of paste were investigated by isothermal calorimeter analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The results show that ALSF is excellent for the rapid setting and hardening of the cement. When the content of ALSF was 8 wt%, the initial setting time and final setting time of paste were 85 s and 180 s, respectively, and the 1 d and 28 d strengths of mortar were 9.52 MPa and 44.42 MPa, respectively. ALSF can accelerate the dissolution and hydration of C3A and C3S and promote the formation of 3CaO·Al2O3·3CaSO4·32H2O (ettringite), AFt formate, and portlandite.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139603617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 aims to investigate and predict the compressive strength of geopolymer concrete (GPC). The effects of curing method, curing time and concrete age on the compressive strength of GPC, were evaluated experimentally. Four curing methods, namely room temperature (25oC), mobile dryer (50oC), heating cabinet type 1 (80oC), and heating cabinet type 2 (100oC) were adopted. Additionally, three curing times of 8h, 16h and 24h, as well as three concrete ages of 7 days, 14 days, and 28 days, were considered. To predict the compressive strength of GPC, 679 test results were collected to develop various machine learning models. The test results indicated that increasing the curing temperature, curing time and concrete age all led to the improvements in the compressive strength of GPC. The mobile dryer showed promise as a curing method for cast in place GPC. The proposed machine learning models demonstrated good predictive capacity for the compressive strength of GPC with relatively high accuracy. Through sensitivity analysis, the concrete age was identified as the most influential variable affecting the final compressive strength of GPC.
{"title":"Experimental study and machine learning based prediction of the compressive strength of geopolymer concrete","authors":"Ngoc-Thanh Tran, Duy Hung Nguyen, Quang Thanh Tran, Huy Viet Le, Duy-Liem Nguyen","doi":"10.1680/jmacr.23.00144","DOIUrl":"https://doi.org/10.1680/jmacr.23.00144","url":null,"abstract":"This study aims to investigate and predict the compressive strength of geopolymer concrete (GPC). The effects of curing method, curing time and concrete age on the compressive strength of GPC, were evaluated experimentally. Four curing methods, namely room temperature (25oC), mobile dryer (50oC), heating cabinet type 1 (80oC), and heating cabinet type 2 (100oC) were adopted. Additionally, three curing times of 8h, 16h and 24h, as well as three concrete ages of 7 days, 14 days, and 28 days, were considered. To predict the compressive strength of GPC, 679 test results were collected to develop various machine learning models. The test results indicated that increasing the curing temperature, curing time and concrete age all led to the improvements in the compressive strength of GPC. The mobile dryer showed promise as a curing method for cast in place GPC. The proposed machine learning models demonstrated good predictive capacity for the compressive strength of GPC with relatively high accuracy. Through sensitivity analysis, the concrete age was identified as the most influential variable affecting the final compressive strength of GPC.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139604547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chandrashekhar Lakavath, S. S. Prakash, Srinivas Allena
This study presents an experimental evaluation of ultra-high-performance fiber-reinforced concrete specimens with and without longitudinal reinforcement under direct tensile loading. The study variables are (i) volume fraction of fibers (1.0% and 2.0%), (ii) type of steel fibers (straight and hooked end), and (iii) longitudinal steel reinforcement ratio of 0.0% and 1.2%. All the specimens are tested using a servo-controlled fatigue testing machine in a displacement control mode. The changes in displacement were monitored using a linear variable displacement transducer and a digital image correlation technique. The strain profile at different loading stages is presented to identify the crack evolution process. Test results show that the average localized strain ranges from 0.2% to 0.36%, with corresponding crack widths of 0.3 mm to 0.6 mm. A uniaxial tensile stress-strain model is proposed based on the test results and literature database. The longitudinal steel reinforced specimens show both stiffening and strengthening effects. Tension-stiffened specimens with 1.0% fibers failed at a higher strain due to the formation of multiple macro cracks. In the specimens with 2.0% fibers, the rebar fractured in a brittle manner due to crack localization. A higher longitudinal reinforcement ratio is needed to effectively utilize UHPFRC under tension-dominant loads.
{"title":"Tensile characteristics of ultra-high performance fiber reinforced concrete with and without longitudinal steel rebars","authors":"Chandrashekhar Lakavath, S. S. Prakash, Srinivas Allena","doi":"10.1680/jmacr.23.00181","DOIUrl":"https://doi.org/10.1680/jmacr.23.00181","url":null,"abstract":"This study presents an experimental evaluation of ultra-high-performance fiber-reinforced concrete specimens with and without longitudinal reinforcement under direct tensile loading. The study variables are (i) volume fraction of fibers (1.0% and 2.0%), (ii) type of steel fibers (straight and hooked end), and (iii) longitudinal steel reinforcement ratio of 0.0% and 1.2%. All the specimens are tested using a servo-controlled fatigue testing machine in a displacement control mode. The changes in displacement were monitored using a linear variable displacement transducer and a digital image correlation technique. The strain profile at different loading stages is presented to identify the crack evolution process. Test results show that the average localized strain ranges from 0.2% to 0.36%, with corresponding crack widths of 0.3 mm to 0.6 mm. A uniaxial tensile stress-strain model is proposed based on the test results and literature database. The longitudinal steel reinforced specimens show both stiffening and strengthening effects. Tension-stiffened specimens with 1.0% fibers failed at a higher strain due to the formation of multiple macro cracks. In the specimens with 2.0% fibers, the rebar fractured in a brittle manner due to crack localization. A higher longitudinal reinforcement ratio is needed to effectively utilize UHPFRC under tension-dominant loads.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139603346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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