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":"10 3","pages":""},"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":"68 13","pages":""},"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":"57 1","pages":""},"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":"11 1","pages":""},"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}
Depending on the type of application, polymer concrete (PC) may be exposed to high temperatures. Therefore, it is important to investigate the influence of exposure to elevated temperatures on the fracture mechanics of PC. For this purpose, the PC composed of epoxy as resin, silica sand and crushed basalt as aggregates, and nanoclay as nanofiller is synthesized. The prepared PC is exposed to temperatures of 24, 40, 60, 80, 100, 120, and 140°C for two hours, and the residual fracture toughness and fracture energy in mode I and mode II are studied. Three-point bending test is conducted on cracked semi-circular bend specimens with the crack angle of 0° (pure mode I) and 41° (pure mode II) to determine the fracture parameters. Subjecting to high temperatures significantly increased the fracture toughness and fracture energy of the PC. The maximum fracture toughness and fracture energy are obtained after exposure to 120°C and 140°C, respectively. Scanning electron microscope (SEM) micrographs are used to investigate the fracture surface of the PC. The results of the present experimental research are useful in understanding the fracture mechanics behavior of PCs in mode I and mode II after being subjected to high temperatures.
{"title":"Influence of elevated temperatures on mode I and mode II fracture toughness and fracture energy of nanoclay reinforced polymer concrete","authors":"Ali Abdi Aghdam, Mostafa Hassani Niaki","doi":"10.1680/jmacr.23.00163","DOIUrl":"https://doi.org/10.1680/jmacr.23.00163","url":null,"abstract":"Depending on the type of application, polymer concrete (PC) may be exposed to high temperatures. Therefore, it is important to investigate the influence of exposure to elevated temperatures on the fracture mechanics of PC. For this purpose, the PC composed of epoxy as resin, silica sand and crushed basalt as aggregates, and nanoclay as nanofiller is synthesized. The prepared PC is exposed to temperatures of 24, 40, 60, 80, 100, 120, and 140°C for two hours, and the residual fracture toughness and fracture energy in mode I and mode II are studied. Three-point bending test is conducted on cracked semi-circular bend specimens with the crack angle of 0° (pure mode I) and 41° (pure mode II) to determine the fracture parameters. Subjecting to high temperatures significantly increased the fracture toughness and fracture energy of the PC. The maximum fracture toughness and fracture energy are obtained after exposure to 120°C and 140°C, respectively. Scanning electron microscope (SEM) micrographs are used to investigate the fracture surface of the PC. The results of the present experimental research are useful in understanding the fracture mechanics behavior of PCs in mode I and mode II after being subjected to high temperatures.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":" 5","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138493759","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}
Zhiyou Jia, José Aguiar, Sandra Cunha, Carlos Jesus, Fernando Castro
As the economy and industrialization have grown, the foundry industry has produced a significant amount of ceramic mold casting waste (CMCW). To promote resource utilization, this study investigates recycling CMCW as a partial replacement for lightweight aggregates in lightweight concrete. This study investigated the durability of lightweight concrete mixes with varying CMCW content, using surface electrical tests, ultrasonic pulse velocity measurements, non-steady state accelerated chloride penetration tests, and carbonation resistance experiments. Then, the results indicate that a lightweight concrete containing 80% CMCW exhibited greater density and uniformity, greater resistance to chloride ion penetration and better resistance to carbonation. These findings suggest that CMCW can be an effective and sustainable replacement for lightweight aggregate in lightweight concrete, improving their durability and environmental performance. This research contributes to the development of sustainable construction materials and provides insights for the use of CMCW in the foundry industry.
{"title":"Durability properties of lightweight concrete with ceramic mold casting waste","authors":"Zhiyou Jia, José Aguiar, Sandra Cunha, Carlos Jesus, Fernando Castro","doi":"10.1680/jmacr.23.00125","DOIUrl":"https://doi.org/10.1680/jmacr.23.00125","url":null,"abstract":"As the economy and industrialization have grown, the foundry industry has produced a significant amount of ceramic mold casting waste (CMCW). To promote resource utilization, this study investigates recycling CMCW as a partial replacement for lightweight aggregates in lightweight concrete. This study investigated the durability of lightweight concrete mixes with varying CMCW content, using surface electrical tests, ultrasonic pulse velocity measurements, non-steady state accelerated chloride penetration tests, and carbonation resistance experiments. Then, the results indicate that a lightweight concrete containing 80% CMCW exhibited greater density and uniformity, greater resistance to chloride ion penetration and better resistance to carbonation. These findings suggest that CMCW can be an effective and sustainable replacement for lightweight aggregate in lightweight concrete, improving their durability and environmental performance. This research contributes to the development of sustainable construction materials and provides insights for the use of CMCW in the foundry industry.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"138 ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138504820","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 amount of industrial waste is increasing along with industrial production. Therefore, reusing or recycling these harmful wastes is quite a significant issue for waste management. Concrete, the most widely used material in the world, is a suitable place to use these wastes. This study used grinding swarf, which had not been used in cementitious composites before, and metal shaving from the CNC milling process. The effects of these wastes on the strength and durability of cement mortars were investigated by using them separately and in hybrid forms. Flowability, fresh unit weight, compressive strength, flexural strength, water absorption, and high-temperature effect tests were conducted on mortar samples. Although the wastes contributed when used alone, they yielded the highest contribution when combined. When the waste materials were used in a hybrid form, they increased compressive strength, flexural strength, and high-temperature resistance by 29%, 12.98%, and 49.50%, respectively. Metal shavings showed fiber effects, and grinding swarfs improved the strength and durability properties owing to their physical and chemical composition.
{"title":"Effects of hybrid metallic wastes on the strength and durability properties of cementitious mortars","authors":"Musa Yildirim, Hacer Bilir Özhan","doi":"10.1680/jmacr.23.00122","DOIUrl":"https://doi.org/10.1680/jmacr.23.00122","url":null,"abstract":"The amount of industrial waste is increasing along with industrial production. Therefore, reusing or recycling these harmful wastes is quite a significant issue for waste management. Concrete, the most widely used material in the world, is a suitable place to use these wastes. This study used grinding swarf, which had not been used in cementitious composites before, and metal shaving from the CNC milling process. The effects of these wastes on the strength and durability of cement mortars were investigated by using them separately and in hybrid forms. Flowability, fresh unit weight, compressive strength, flexural strength, water absorption, and high-temperature effect tests were conducted on mortar samples. Although the wastes contributed when used alone, they yielded the highest contribution when combined. When the waste materials were used in a hybrid form, they increased compressive strength, flexural strength, and high-temperature resistance by 29%, 12.98%, and 49.50%, respectively. Metal shavings showed fiber effects, and grinding swarfs improved the strength and durability properties owing to their physical and chemical composition.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"141 ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138504817","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}
Recycled aggregate concrete (RAC) often shows different strength and deformation properties to natural aggregate concrete (NAC) and may therefore have an impact on the connections between precast concrete elements. In this work, three simple connections between precast concrete columns were considered, including a wet connection with bedding mortar, a dry connection without bedding mortar and a monolithic joint with plain concrete. An industrially produced coarse recycled concrete aggregate (RCA) was used to replace partially or fully a coarse natural aggregate in the concrete. A total of twenty-two 200 mm × 200 mm × 500 mm reinforced concrete columns were prepared and tested under axial monotonic loading through displacement control. The results showed that regardless of RCA content, the equation specified in ACI 318 (2019) and the one proposed by Vambersky (1990) provided safe estimates of the load-bearing capacity of wet connections between reinforced RAC columns.
再生骨料混凝土(RAC)往往表现出与天然骨料混凝土(NAC)不同的强度和变形特性，因此可能对预制混凝土构件之间的连接产生影响。在这项工作中，考虑了预制混凝土柱之间的三种简单连接，包括带衬垫砂浆的湿连接，不带衬垫砂浆的干连接以及与素混凝土的整体连接。采用工业生产的粗再生混凝土骨料(RCA)部分或全部替代混凝土中的粗天然骨料。通过位移控制，制备了22根200 mm × 200 mm × 500 mm钢筋混凝土柱，并进行了轴向单调加载试验。结果表明，无论RCA含量如何，ACI 318(2019)中规定的方程和Vambersky(1990)提出的方程都提供了钢筋RAC柱间湿连接承载能力的安全估计。
{"title":"Load-bearing capacity of precast high-strength self-compacting recycled aggregate concrete column-to-column connections","authors":"Xiaoguang Chen, Zeger Sierens, Jiabin Li","doi":"10.1680/jmacr.23.00109","DOIUrl":"https://doi.org/10.1680/jmacr.23.00109","url":null,"abstract":"Recycled aggregate concrete (RAC) often shows different strength and deformation properties to natural aggregate concrete (NAC) and may therefore have an impact on the connections between precast concrete elements. In this work, three simple connections between precast concrete columns were considered, including a wet connection with bedding mortar, a dry connection without bedding mortar and a monolithic joint with plain concrete. An industrially produced coarse recycled concrete aggregate (RCA) was used to replace partially or fully a coarse natural aggregate in the concrete. A total of twenty-two 200 mm × 200 mm × 500 mm reinforced concrete columns were prepared and tested under axial monotonic loading through displacement control. The results showed that regardless of RCA content, the equation specified in ACI 318 (2019) and the one proposed by Vambersky (1990) provided safe estimates of the load-bearing capacity of wet connections between reinforced RAC columns.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"140 ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138504818","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}
Improving the flexural strength of a chopped-carbon fibre-reinforced cement-based composite while promoting good workability is highly attractive for building high-rise large-span structures. This study utilized a sulphoaluminate-based expansive agent to optimize the mechanical properties of chopped-carbon fibre-reinforced cement-based composites by improving the fibre–matrix interfacial properties. The results of a single-fibre pull-out test showed that the interfacial frictional bond strength improved up to 51% owing to the addition of the expansive agent, whereas the chemical debonding energy remained nearly unchanged. The study then investigated the effects of various concentrations of the expansive agent on the strength of the cement paste containing various lengths and volume fractions of the carbon fibre. The results indicated that benefited from the expansive agent induced high interfacial bond strength, the flexural strength and fluidity of the carbon fibre reinforced cement paste could be further optimized. For example, by utilizing expansive agent, the flexural strength could be further improved by 28% for cement paste containing 0.5% carbon fibre with length of 15mm.
{"title":"Effect of an expansive agent on the interfacial bond and mechanical properties of carbon fibre-reinforced cement-based composites","authors":"Jinghui Dai, Jun Wang, Huigang Xiao","doi":"10.1680/jmacr.23.00098","DOIUrl":"https://doi.org/10.1680/jmacr.23.00098","url":null,"abstract":"Improving the flexural strength of a chopped-carbon fibre-reinforced cement-based composite while promoting good workability is highly attractive for building high-rise large-span structures. This study utilized a sulphoaluminate-based expansive agent to optimize the mechanical properties of chopped-carbon fibre-reinforced cement-based composites by improving the fibre–matrix interfacial properties. The results of a single-fibre pull-out test showed that the interfacial frictional bond strength improved up to 51% owing to the addition of the expansive agent, whereas the chemical debonding energy remained nearly unchanged. The study then investigated the effects of various concentrations of the expansive agent on the strength of the cement paste containing various lengths and volume fractions of the carbon fibre. The results indicated that benefited from the expansive agent induced high interfacial bond strength, the flexural strength and fluidity of the carbon fibre reinforced cement paste could be further optimized. For example, by utilizing expansive agent, the flexural strength could be further improved by 28% for cement paste containing 0.5% carbon fibre with length of 15mm.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"139 ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138504819","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}
During pumping of concrete, the lubrication layer (LL) formed at the interface of the concrete and the pipe plays a crucial role in facilitating the process. Shear thickening in this layer affects the concrete pumping significantly. However, very few studies are available in understanding the onset and intensity of shear thickening behavior of the lubrication layer. In this study, the effect of solid volume fraction (SVF), superplasticizer (SP) dosage, supplementary cementitious materials (SCMs) and hydration on the shear thickening (Continuous and discontinuous) behavior of cementitious suspensions are investigated. Results show that an increase in SVF, reduces the shear thickening intensity in case of cement (OPC) systems whereas the intensity is amplified for systems with fly ash (FA) and ground granulated blast furnace slag (GGBS). An increment in the SP dosage results in an early onset and increases the shear thickening intensity, regardless of the binder used. GGBS based systems show the highest shear thickening intensity, followed by OPC and FA based systems. Based on the results, it is evident that the optimization of SP dosage for OPC based systems needs to be carried out based on the structural build-up, while for FA or GGBS based systems, the SP optimization needs to be carried out based on shear thickening behavior with respect to hydration.
{"title":"Shear thickening of cementitious suspensions: effect of high solid volume fraction and hydration","authors":"P. V. P. Moorthi, Prakash Nanthagopalan","doi":"10.1680/jmacr.23.00126","DOIUrl":"https://doi.org/10.1680/jmacr.23.00126","url":null,"abstract":"During pumping of concrete, the lubrication layer (LL) formed at the interface of the concrete and the pipe plays a crucial role in facilitating the process. Shear thickening in this layer affects the concrete pumping significantly. However, very few studies are available in understanding the onset and intensity of shear thickening behavior of the lubrication layer. In this study, the effect of solid volume fraction (SVF), superplasticizer (SP) dosage, supplementary cementitious materials (SCMs) and hydration on the shear thickening (Continuous and discontinuous) behavior of cementitious suspensions are investigated. Results show that an increase in SVF, reduces the shear thickening intensity in case of cement (OPC) systems whereas the intensity is amplified for systems with fly ash (FA) and ground granulated blast furnace slag (GGBS). An increment in the SP dosage results in an early onset and increases the shear thickening intensity, regardless of the binder used. GGBS based systems show the highest shear thickening intensity, followed by OPC and FA based systems. Based on the results, it is evident that the optimization of SP dosage for OPC based systems needs to be carried out based on the structural build-up, while for FA or GGBS based systems, the SP optimization needs to be carried out based on shear thickening behavior with respect to hydration.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"142 ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138504816","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：