Ultra-high-performance concrete (UHPC) is susceptible to various forms of abrasion during its service life. This study investigates the abrasion resistance of UHPC by focusing on two primary causes of wear: traffic dynamic loads and hydraulic impacts. To enhance the material's resistance to abrasion, milling steel fibers were utilized, and for comparative purposes, straight steel fibers and hybrid milling-straight steel fibers were also employed. The protective function of the steel fibers primarily comes into effect once the concrete cover has experienced wear. When subjected to traffic and hydraulic loads, UHPC containing milling fibers exhibited superior resistance compared to that containing straight fibers, while maintaining favorable workability. Notably, the UHPC incorporating hybrid steel fibers, which form a composite skeleton due to the presence of two fiber types, demonstrated even greater effectiveness in resisting external abrasion. Furthermore, the abrasion resistances observed under both traffic and hydraulic conditions displayed a positive linear correlation with an R2 value exceeding 0.8. These findings suggest the feasibility of evaluating the material's abrasion resistance under various wearing causes using a single test method. The outcomes of this study hold promise in advancing the development of UHPC and promoting its utilization in conditions characterized by severe abrasion.
{"title":"Abrasion resistance of milling steel fiber-reinforced ultra-high-performance concrete under various wearing conditions","authors":"Hengchang Wang, Baixi Chen, Yibo Yang, Yinggan Xia, Qifeng Xiao, Shaokun Liu, Wenying Guo","doi":"10.1680/jmacr.23.00236","DOIUrl":"https://doi.org/10.1680/jmacr.23.00236","url":null,"abstract":"Ultra-high-performance concrete (UHPC) is susceptible to various forms of abrasion during its service life. This study investigates the abrasion resistance of UHPC by focusing on two primary causes of wear: traffic dynamic loads and hydraulic impacts. To enhance the material's resistance to abrasion, milling steel fibers were utilized, and for comparative purposes, straight steel fibers and hybrid milling-straight steel fibers were also employed. The protective function of the steel fibers primarily comes into effect once the concrete cover has experienced wear. When subjected to traffic and hydraulic loads, UHPC containing milling fibers exhibited superior resistance compared to that containing straight fibers, while maintaining favorable workability. Notably, the UHPC incorporating hybrid steel fibers, which form a composite skeleton due to the presence of two fiber types, demonstrated even greater effectiveness in resisting external abrasion. Furthermore, the abrasion resistances observed under both traffic and hydraulic conditions displayed a positive linear correlation with an R<sup>2</sup> value exceeding 0.8. These findings suggest the feasibility of evaluating the material's abrasion resistance under various wearing causes using a single test method. The outcomes of this study hold promise in advancing the development of UHPC and promoting its utilization in conditions characterized by severe abrasion.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138818307","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}
Zahir Azimi, Moein Mousavi, Habib Akbarzadeh Bengar, Akbar A. Javadi
Along with the rise in construction with 3D printing technology, 3D printed (3DP) structures also require weight reduction similar to conventional reinforcement concrete (RC) structures. In addition, the behaviour of this type of structure against fire needs to be investigated. The number of printed layers and the time gap between layers for the 3DP specimens were among the variables examined in the tests. The test results demonstrated that as the replacement percentage of natural sand (NS) with expanded perlite (EP) increased, at 25% volume of replacement the interlayer bond strength increased on average by 18.6%, while at the highest replacement level of 75%, decreased on average by 5.8%. Additionally, by incorporation of EP the compressive and flexural strengths of 3DP specimens declined averagely from 9% to 29.7%, and 39.3% to 49.3%, respectively. As the replacement level of NS increased, residual compressive and flexural strengths increased after exposure to 800 °C. Furthermore, it was demonstrated that exposure to high temperature had the least effect on interlayer bond strength, whereas it significantly reduced the compressive and flexural strength. The results showed that, increasing the time gap between layers reduced interlayer bond strength and flexural strength while negligibly affected compressive strength.
随着 3D 打印技术在建筑领域的应用，3D 打印（3DP）结构也需要与传统钢筋混凝土（RC）结构一样减轻重量。此外，还需要研究这类结构的防火性能。3DP 试样的打印层数和层与层之间的时间间隔是测试中的变量之一。试验结果表明，随着膨胀珍珠岩（EP）对天然砂（NS）替代比例的增加，在替代量为 25% 时，层间粘结强度平均增加了 18.6%，而在最高替代水平 75% 时，平均降低了 5.8%。此外，加入 EP 后，3DP 试样的抗压和抗弯强度平均分别从 9% 下降到 29.7%，从 39.3% 下降到 49.3%。随着 NS 替代水平的提高，暴露于 800 °C 后的残余抗压强度和抗折强度也有所提高。此外，高温暴露对层间结合强度的影响最小，但会显著降低抗压和抗折强度。结果表明，增加层间时间间隔会降低层间结合强度和抗折强度，而对抗压强度的影响可以忽略不计。
{"title":"Study on the post-fire mechanical properties of lightweight 3D printed concrete containing expanded perlite as partial replacement of natural sand","authors":"Zahir Azimi, Moein Mousavi, Habib Akbarzadeh Bengar, Akbar A. Javadi","doi":"10.1680/jmacr.23.00159","DOIUrl":"https://doi.org/10.1680/jmacr.23.00159","url":null,"abstract":"Along with the rise in construction with 3D printing technology, 3D printed (3DP) structures also require weight reduction similar to conventional reinforcement concrete (RC) structures. In addition, the behaviour of this type of structure against fire needs to be investigated. The number of printed layers and the time gap between layers for the 3DP specimens were among the variables examined in the tests. The test results demonstrated that as the replacement percentage of natural sand (NS) with expanded perlite (EP) increased, at 25% volume of replacement the interlayer bond strength increased on average by 18.6%, while at the highest replacement level of 75%, decreased on average by 5.8%. Additionally, by incorporation of EP the compressive and flexural strengths of 3DP specimens declined averagely from 9% to 29.7%, and 39.3% to 49.3%, respectively. As the replacement level of NS increased, residual compressive and flexural strengths increased after exposure to 800 °C. Furthermore, it was demonstrated that exposure to high temperature had the least effect on interlayer bond strength, whereas it significantly reduced the compressive and flexural strength. The results showed that, increasing the time gap between layers reduced interlayer bond strength and flexural strength while negligibly affected compressive strength.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138818538","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 innovative Arc Pressure Testing Method (APTM) is adopted in this study to obtain the strength of in-situ concrete and reduce damage to the concrete structure. This method is related to the double shear plane of the concrete core. A specific APTM apparatus is used to apply loads for obtaining the approximate pure shear stress and shear strength of the concrete core. Factors affecting the strength of concrete, such as aggregate type and concrete moisture, were excluded through experiments. The compressive strength range of the tested cube concrete samples is 20-60MPa. The reliability and repeatability of APTM are superior to in-situ testing techniques such as Schmidt Hammer (SRH) and pull-out testing methods. The experimental results indicate that APTM is suitable for in-situ testing of concrete compressive strength of prefabricated buildings, beam-column joints other dense steel structures. Compared with other testing methods, its accuracy is much higher, and the damage to the structure is minimized.
{"title":"Experimental study on compressive strength of in-situ concrete tested with arc pressure method","authors":"Suhang Yang, Chen Hu, Zhifeng Xu","doi":"10.1680/jmacr.23.00177","DOIUrl":"https://doi.org/10.1680/jmacr.23.00177","url":null,"abstract":"The innovative Arc Pressure Testing Method (APTM) is adopted in this study to obtain the strength of in-situ concrete and reduce damage to the concrete structure. This method is related to the double shear plane of the concrete core. A specific APTM apparatus is used to apply loads for obtaining the approximate pure shear stress and shear strength of the concrete core. Factors affecting the strength of concrete, such as aggregate type and concrete moisture, were excluded through experiments. The compressive strength range of the tested cube concrete samples is 20-60MPa. The reliability and repeatability of APTM are superior to in-situ testing techniques such as Schmidt Hammer (SRH) and pull-out testing methods. The experimental results indicate that APTM is suitable for in-situ testing of concrete compressive strength of prefabricated buildings, beam-column joints other dense steel structures. Compared with other testing methods, its accuracy is much higher, and the damage to the structure is minimized.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138821749","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 paper presents a comparative evaluation of the single and combined effect of nanoparticles on the static and impact properties of concrete. Nano-SiO2, nano-Al2O3 and nano-Fe2O3 were used separately and in combined forms as partial replacements of cement by 1% and 2% by weight. The impact of nanoparticles on the unit weight, compressive strength, split tensile strength, flexural strength, toughness, fracture energy, impact performance of concrete was experimentally examined. In addition, the effect of these nanoparticles on the microstructure of concrete was investigated using SEM analysis. Moreover, to evaluate the commercial production of such concretes, the cost effectiveness of use of nanoparticles in concrete was also discussed. Desirability function analysis was also conducted to compare the overall performance of the tested concretes. The results revealed that use of nano materials in concrete had a positive effect on improving their mechanical performance. Nanoparticles increased the compressive strength, split tensile strength, flexural strength, and energy absorption capacity of concrete. Use of nanoparticles didn't show any significant influence on the unit weight of concrete. Moreover, the results also showed that nano materials didn't have a good influence on the impact performance of concrete. SEM analysis showed that use of nanoparticles improved the microstructure of concrete.
{"title":"Experimental study on static and impact properties of concrete incorporating nano-SiO2, nano-Al2O3 and Fe2O3 in single and combined forms","authors":"Mohammed Gamal Al-Hagri, Mahmud Sami Döndüren","doi":"10.1680/jmacr.23.00156","DOIUrl":"https://doi.org/10.1680/jmacr.23.00156","url":null,"abstract":"This paper presents a comparative evaluation of the single and combined effect of nanoparticles on the static and impact properties of concrete. Nano-SiO<sub>2</sub>, nano-Al<sub>2</sub>O<sub>3</sub> and nano-Fe<sub>2</sub>O<sub>3</sub> were used separately and in combined forms as partial replacements of cement by 1% and 2% by weight. The impact of nanoparticles on the unit weight, compressive strength, split tensile strength, flexural strength, toughness, fracture energy, impact performance of concrete was experimentally examined. In addition, the effect of these nanoparticles on the microstructure of concrete was investigated using SEM analysis. Moreover, to evaluate the commercial production of such concretes, the cost effectiveness of use of nanoparticles in concrete was also discussed. Desirability function analysis was also conducted to compare the overall performance of the tested concretes. The results revealed that use of nano materials in concrete had a positive effect on improving their mechanical performance. Nanoparticles increased the compressive strength, split tensile strength, flexural strength, and energy absorption capacity of concrete. Use of nanoparticles didn't show any significant influence on the unit weight of concrete. Moreover, the results also showed that nano materials didn't have a good influence on the impact performance of concrete. SEM analysis showed that use of nanoparticles improved the microstructure of concrete.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138818590","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 systematically investigates the superplasticizer (SP) addition methods and optimum SP dosage with various water binder (w/b) ratios for mixing 3D printable concrete (3DPC). In the present study, five distinct strategies were adopted to arrive at the optimum Method of Addition (MoA). The first strategy applied the random mixing approach to identify the methods for adding SP with varying time patterns through visual observation. Secondly, a constant time pattern was adopted from the random approach for mixing and the optimal SP dosage was determined. The third strategy examined different addition methods with the optimum SP dosage. In the fourth strategy, the batching effect of the material with the optimum SP dosage was assessed, and finally, the printable region with different w/b ratios and SP dosages were correlated. The observations illustrated that the optimum SP dosage in the range of 0.10 to 0.21% of binder with a w/b ratio of 0.21 to 0.25 achieved adequate printability parameters by full addition of SP following a constant wet mixing time as the optimal application. However, after applying the optimum SP dosage, a supplemental SP dosage is required at appropriate intervals to retain the workability for higher batches.
{"title":"Mixing approach for 3D printable concrete: method of addition and optimization of superplasticizer dosage","authors":"P.S. Ambily, Senthil Kumar Kaliyavaradhan, Shilpa Sebastian, Deepadharshan Shekar","doi":"10.1680/jmacr.23.00165","DOIUrl":"https://doi.org/10.1680/jmacr.23.00165","url":null,"abstract":"This study systematically investigates the superplasticizer (SP) addition methods and optimum SP dosage with various water binder (w/b) ratios for mixing 3D printable concrete (3DPC). In the present study, five distinct strategies were adopted to arrive at the optimum Method of Addition (MoA). The first strategy applied the random mixing approach to identify the methods for adding SP with varying time patterns through visual observation. Secondly, a constant time pattern was adopted from the random approach for mixing and the optimal SP dosage was determined. The third strategy examined different addition methods with the optimum SP dosage. In the fourth strategy, the batching effect of the material with the optimum SP dosage was assessed, and finally, the printable region with different w/b ratios and SP dosages were correlated. The observations illustrated that the optimum SP dosage in the range of 0.10 to 0.21% of binder with a w/b ratio of 0.21 to 0.25 achieved adequate printability parameters by full addition of SP following a constant wet mixing time as the optimal application. However, after applying the optimum SP dosage, a supplemental SP dosage is required at appropriate intervals to retain the workability for higher batches.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138688045","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}
Dongyun Liu, Chao Wang, Tong Guo, Jaime Gonzalez-Libreros, Yuanfei Ge, Yongming Tu, Lennart Elfgren, Gabriel Sas
Chloride attack severely impacts the performance of reinforced concrete. The total and free chloride ion concentrations (CICs) of self-compacting concrete (SCC) prepared with three supplementary cementitious materials (SCMs) - fly ash (FA), blast furnace slag (BS), and silica fume (SF) – were measured through the accelerated salt immersion tests. The apparent chloride diffusion coefficients (CDCs) at any exposure time and erosion depth were calculated using the Boltzmann-Matano method. The influence of the type and content of SCMs, the water-binder ratio (W/B), and the type of salt solution on CICs and CDCs were investigated. Both introducing SCMs and reducing W/B effectively reduced the CIC. The SCM that most effectively reduced CIC was SF, followed by BS and then FA. Free CICs were reduced to a greater degree than total CICs in FA and BS concrete, but the opposite was true for SF concrete. Presence of calcium chloride in salt solution increased total CICs while reducing free CICs. Apparent free CDC dropped over exposure time and initially increased with erosion depth but eventually stabilized. A model of apparent free CDC considering the time-depth dependence was created, which shows that time reduction factors of CDC is larger in SCM-containing SCC than in control SCC.
{"title":"Time-depth dependent chloride diffusion coefficients of self-compacting concrete","authors":"Dongyun Liu, Chao Wang, Tong Guo, Jaime Gonzalez-Libreros, Yuanfei Ge, Yongming Tu, Lennart Elfgren, Gabriel Sas","doi":"10.1680/jmacr.23.00237","DOIUrl":"https://doi.org/10.1680/jmacr.23.00237","url":null,"abstract":"Chloride attack severely impacts the performance of reinforced concrete. The total and free chloride ion concentrations (CICs) of self-compacting concrete (SCC) prepared with three supplementary cementitious materials (SCMs) - fly ash (FA), blast furnace slag (BS), and silica fume (SF) – were measured through the accelerated salt immersion tests. The apparent chloride diffusion coefficients (CDCs) at any exposure time and erosion depth were calculated using the Boltzmann-Matano method. The influence of the type and content of SCMs, the water-binder ratio (W/B), and the type of salt solution on CICs and CDCs were investigated. Both introducing SCMs and reducing W/B effectively reduced the CIC. The SCM that most effectively reduced CIC was SF, followed by BS and then FA. Free CICs were reduced to a greater degree than total CICs in FA and BS concrete, but the opposite was true for SF concrete. Presence of calcium chloride in salt solution increased total CICs while reducing free CICs. Apparent free CDC dropped over exposure time and initially increased with erosion depth but eventually stabilized. A model of apparent free CDC considering the time-depth dependence was created, which shows that time reduction factors of CDC is larger in SCM-containing SCC than in control SCC.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138576822","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}
Aocheng Zhong, M. Sofi, E. Lumantarna, Zhiyuan Zhou, P. Mendis
The issue of early age concrete cracking is challenging and relies on the state of concrete soon after it is placed in the formwork. The concrete state is a function of the strains associated with thermal and other dilatations and the level of in-situ strength. Both strain and strength primarily require information on the temperature-time history of the concrete element. For larger elements, the thermal history varies significantly across the thickness and the concrete material itself acts as a confinement for discrete elements. Due to complexity of the issue, designers currently rely on mock tests and/or finite element modelling mostly for structures that are deemed ‘important’. Both approaches are costly and time consuming. It is, therefore, important to have a robust yet simple model to estimate the temperature variation experienced by the concrete elements. The proposed spreadsheet-based model reported in this paper aims to provide a rapid estimate of the temperature profiles within a hydrating concrete element. The model uses the concept of effective thickness and the revised heat compensation technique. It is validated based on measured temperature development of a rectangular section concrete block. Further, the proposed model is successfully compared with output from finite element software TNO Diana.
{"title":"Effects a simplified numerical model for temperature profiles of early age concrete","authors":"Aocheng Zhong, M. Sofi, E. Lumantarna, Zhiyuan Zhou, P. Mendis","doi":"10.1680/jmacr.21.00139","DOIUrl":"https://doi.org/10.1680/jmacr.21.00139","url":null,"abstract":"The issue of early age concrete cracking is challenging and relies on the state of concrete soon after it is placed in the formwork. The concrete state is a function of the strains associated with thermal and other dilatations and the level of in-situ strength. Both strain and strength primarily require information on the temperature-time history of the concrete element. For larger elements, the thermal history varies significantly across the thickness and the concrete material itself acts as a confinement for discrete elements. Due to complexity of the issue, designers currently rely on mock tests and/or finite element modelling mostly for structures that are deemed ‘important’. Both approaches are costly and time consuming. It is, therefore, important to have a robust yet simple model to estimate the temperature variation experienced by the concrete elements. The proposed spreadsheet-based model reported in this paper aims to provide a rapid estimate of the temperature profiles within a hydrating concrete element. The model uses the concept of effective thickness and the revised heat compensation technique. It is validated based on measured temperature development of a rectangular section concrete block. Further, the proposed model is successfully compared with output from finite element software TNO Diana.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138589880","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 paper proposes a novel confined concrete constitutive model for steel reinforced concrete (SRC) columns with cross-shaped steel (CSS) sections based on the similar characteristics of descending branches in stress-strain curves of confined and unconfined concrete, by considering confinement degradation caused by the buckling of steel section or longitudinal reinforcement. The confined region of SRC columns with CSS sections was divided into four parts: highly steel-confined concrete (HSC), partially steel-confined concrete (PSC), stirrup confined concrete (SCC), and unconfined concrete (UCC). Additionally, relevant effective confinement coefficient expressions were presented. Simulation results of existing tests showed that (1) load-strain curves obtained by using the modified stress-strain constitutive model agreed well with the experimental results, with the error in the descending branch smaller than 5%; (2) the HSC region for SRC columns with CSS sections in the finite element model (FEM) was in a good agreement with that in the proposed region division; (3) concrete confined region boundaries simulation for SRC columns with CSS sections were determined by using plumb lines for improving the calculation efficiency.
{"title":"Confinement mechanism and constitutive model of SRC columns with cross-shaped steel sections","authors":"Hong Xiang, Fuyu Mao, Chen Wu, Shenglan Ma","doi":"10.1680/jmacr.23.00186","DOIUrl":"https://doi.org/10.1680/jmacr.23.00186","url":null,"abstract":"This paper proposes a novel confined concrete constitutive model for steel reinforced concrete (SRC) columns with cross-shaped steel (CSS) sections based on the similar characteristics of descending branches in stress-strain curves of confined and unconfined concrete, by considering confinement degradation caused by the buckling of steel section or longitudinal reinforcement. The confined region of SRC columns with CSS sections was divided into four parts: highly steel-confined concrete (HSC), partially steel-confined concrete (PSC), stirrup confined concrete (SCC), and unconfined concrete (UCC). Additionally, relevant effective confinement coefficient expressions were presented. Simulation results of existing tests showed that (1) load-strain curves obtained by using the modified stress-strain constitutive model agreed well with the experimental results, with the error in the descending branch smaller than 5%; (2) the HSC region for SRC columns with CSS sections in the finite element model (FEM) was in a good agreement with that in the proposed region division; (3) concrete confined region boundaries simulation for SRC columns with CSS sections were determined by using plumb lines for improving the calculation efficiency.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138587199","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}
Mohammad Omidi Manesh, V. Sarfarazi, N. Babanouri, Amir Rezaei, Arsham Moayedi Far
Fracture toughness (first mode) of shotcrete samples was obtained employing Edge Notched Partial Disc (ENPD) type specimens. Notched Brazilian Discs (NBD) were also used in order to validate the results of the conducted ENPD experiments. Moreover, a numerical analysis was conducted on the ENPD tests to verify the correctness of the measured fracture toughness values compared to numerically obtain ones. Notch lengths in ENPD were set to 15, 30, 45 and 60 mm. However, the lengths of Notches in NBD were set to 10, 20, 30, 40, 50 and 60 mm. The findings reveal that the flat joint model could accurately determine the potential crack growth path and crack initiation stress compared to experimentally obtained results. It was also deduced that the fracture toughness remained roughly the same by enlarging the length of the notch. Moreover, tensile strength and fracture toughness of shotcrete samples are meaningfully correlated (σt =7.92 KIC). ENPD test yields the lowest fracture toughness because of pure tensile stress distribution on failure surface. It also was also determined that the derived fracture extension patterns from the laboratory investigations are in an acceptable agreement with the numerical simulations’ outputs.
{"title":"New method for determining the Mode-I fracture toughness of shotcrete: edge notched partial disc test","authors":"Mohammad Omidi Manesh, V. Sarfarazi, N. Babanouri, Amir Rezaei, Arsham Moayedi Far","doi":"10.1680/jmacr.23.00004","DOIUrl":"https://doi.org/10.1680/jmacr.23.00004","url":null,"abstract":"Fracture toughness (first mode) of shotcrete samples was obtained employing Edge Notched Partial Disc (ENPD) type specimens. Notched Brazilian Discs (NBD) were also used in order to validate the results of the conducted ENPD experiments. Moreover, a numerical analysis was conducted on the ENPD tests to verify the correctness of the measured fracture toughness values compared to numerically obtain ones. Notch lengths in ENPD were set to 15, 30, 45 and 60 mm. However, the lengths of Notches in NBD were set to 10, 20, 30, 40, 50 and 60 mm. The findings reveal that the flat joint model could accurately determine the potential crack growth path and crack initiation stress compared to experimentally obtained results. It was also deduced that the fracture toughness remained roughly the same by enlarging the length of the notch. Moreover, tensile strength and fracture toughness of shotcrete samples are meaningfully correlated (σt =7.92 KIC). ENPD test yields the lowest fracture toughness because of pure tensile stress distribution on failure surface. It also was also determined that the derived fracture extension patterns from the laboratory investigations are in an acceptable agreement with the numerical simulations’ outputs.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138588056","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}
Adding polypropylene fiber into recycled aggregate concrete (RAC) can not only improve the performance, but also increase economic benefits. To study the single-blend and double-blend polypropylene micro and macro fibers and their effect on the compressive strength of RAC specimens, polypropylene micro fibers of two sizes and polypropylene macro fibers of two sizes were selected to design and produced 30 groups of polypropylene fiber reinforced RAC test specimens with 0%, 25% and 50% coarse aggregate substitution rates by controlling the fiber mixing proportion and the stress-strain curves, elastic modulus, peak strength, peak strain and acoustic emission amplitude-frequency extremum of each group of test specimen were obtained. According to the test results, the elastic modulus and peak stress of test specimens without polypropylene fibers decrease gradually with the increase of the coarse aggregate substitution rate. However, there is a certain increase in elastic modulus and peak stress after polypropylene fibers are added. A damage constitutive model for polypropylene fiber reinforced RAC was established, and by fitting with this model, it is found that although the elastic modulus and peak stress of RAC test specimens are increased by a certain extent, the fitting parameters αc of RAC are greater than those of ordinary concrete, and its post-peak strength is lower than that of ordinary concrete. The evolution law of acoustic emission amplitude-frequency extremum of polypropylene fiber reinforced RAC was studied, and it is found that the cumulative amplitude-frequency extremum Np of RAC is larger than that of the test specimens without polypropylene fibers, indicating that the addition of polypropylene fibers limits the crack propagation and increases the cumulative amplitude-frequency extremum representing fracture energy.
{"title":"A damage constitutive model of polypropylene fiber reinforced recycled aggregate concrete based on AE amplitude-frequency extremum","authors":"Yu Yu, Xin Yang, Yu Tang","doi":"10.1680/jmacr.23.00028","DOIUrl":"https://doi.org/10.1680/jmacr.23.00028","url":null,"abstract":"Adding polypropylene fiber into recycled aggregate concrete (RAC) can not only improve the performance, but also increase economic benefits. To study the single-blend and double-blend polypropylene micro and macro fibers and their effect on the compressive strength of RAC specimens, polypropylene micro fibers of two sizes and polypropylene macro fibers of two sizes were selected to design and produced 30 groups of polypropylene fiber reinforced RAC test specimens with 0%, 25% and 50% coarse aggregate substitution rates by controlling the fiber mixing proportion and the stress-strain curves, elastic modulus, peak strength, peak strain and acoustic emission amplitude-frequency extremum of each group of test specimen were obtained. According to the test results, the elastic modulus and peak stress of test specimens without polypropylene fibers decrease gradually with the increase of the coarse aggregate substitution rate. However, there is a certain increase in elastic modulus and peak stress after polypropylene fibers are added. A damage constitutive model for polypropylene fiber reinforced RAC was established, and by fitting with this model, it is found that although the elastic modulus and peak stress of RAC test specimens are increased by a certain extent, the fitting parameters <i>α<sub>c</sub></i> of RAC are greater than those of ordinary concrete, and its post-peak strength is lower than that of ordinary concrete. The evolution law of acoustic emission amplitude-frequency extremum of polypropylene fiber reinforced RAC was studied, and it is found that the cumulative amplitude-frequency extremum <i>N<sub>p</sub></i> of RAC is larger than that of the test specimens without polypropylene fibers, indicating that the addition of polypropylene fibers limits the crack propagation and increases the cumulative amplitude-frequency extremum representing fracture energy.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2023-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138547533","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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