This study proposes the direct pure shear characterisation of steel fibre-reinforced concrete specimens with two grooved shear planes. Initially, the crimped fibre type was used with a rate varying between (0.0 %, 0.5 %, 1.0 %, and 1.5%), a concrete compressive strength of 35 MPa, a maximum aggregate size of 9.5 mm, and eight specimens subjected to the direct shear test. The results showed a significant gain in shear strength with increased fibre consumption, 90% at a rate of 1.5%. Based on these observations, three analytical expressions were formulated to compute the shear stress. The validation of the models was applied to a group of fifteen blocks of the same smaller size geometry and had as additional variables the hooked-end fibre, the concrete compressive strength of 25 MPa, the type and the maximum size of the coarse aggregate (19 mm and 25 mm). Crimped fibre confirmed good performance compared to the hooked-end, with a strength gain of around 100% at a rate of 1.5% with the maximum coarse aggregate particle size of 25 mm, showing variability between 2 and 7% in the proposed analytical models.
{"title":"Characterisation proposal of direct shear strength of steel fibre-reinforced concrete","authors":"Aaron Kadima Lukanu Lwa Nzambi, Dênio Ramam Carvalho de Oliveira, Vander Luiz da Silva Melo, Ronnan Wembles Martins Barreira, Heber Dioney Sousa Moraes","doi":"10.1680/jmacr.23.00335","DOIUrl":"https://doi.org/10.1680/jmacr.23.00335","url":null,"abstract":"This study proposes the direct pure shear characterisation of steel fibre-reinforced concrete specimens with two grooved shear planes. Initially, the crimped fibre type was used with a rate varying between (0.0 %, 0.5 %, 1.0 %, and 1.5%), a concrete compressive strength of 35 MPa, a maximum aggregate size of 9.5 mm, and eight specimens subjected to the direct shear test. The results showed a significant gain in shear strength with increased fibre consumption, 90% at a rate of 1.5%. Based on these observations, three analytical expressions were formulated to compute the shear stress. The validation of the models was applied to a group of fifteen blocks of the same smaller size geometry and had as additional variables the hooked-end fibre, the concrete compressive strength of 25 MPa, the type and the maximum size of the coarse aggregate (19 mm and 25 mm). Crimped fibre confirmed good performance compared to the hooked-end, with a strength gain of around 100% at a rate of 1.5% with the maximum coarse aggregate particle size of 25 mm, showing variability between 2 and 7% in the proposed analytical models.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"116 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140886907","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}
Reinforced concrete (RC) flat slab structure may suffer progressive collapse, which is usually caused by the punching shear failure of slab-column joints. Existing research has shown that the utilization of shear reinforcements or ultra-high toughness cementitious composite (UHTCC) in slab-column joints is efficient in improving their punching shear performance. In this study, shear reinforcement was introduced into UHTCC-enhanced RC slab-column joints. Specimens of UHTCC-enhanced slab-column joints considering the effect of shear reinforcements were tested. The cracking development process, bearing capacity, and ductility were analyzed. Yield line theory and critical shear crack theory were adopted to predict flexural and punching shear capacities, respectively. Finally, the failure patterns of the specimens were discriminated by comparing the predicted punching shear and flexural capacities, taking the ductile coefficient into account. The theoretical results combined with test results show the effect of shear reinforcement on the behavior of UHTCC-enhanced joints. Significant improvement in the bearing capacity and ductility of joints is achieved by applying shear reinforcement. The failure pattern of a joint varies from premature punching shear failure to flexural-triggered punching shear failure with the application of UHTCC, and this transform is more pronounced with shear reinforcement applied into the UHTCC-enhanced joint.
{"title":"Punching shear tests and design of UHTCC-enhanced RC slab-column joints with shear reinforcements","authors":"Zhe-Xin Yu, Gen-Shu Tong, Jing-Zhong Tong, Xiao-Ning Huang, Qing-Hua Li, Shi-Lang Xu","doi":"10.1680/jmacr.23.00362","DOIUrl":"https://doi.org/10.1680/jmacr.23.00362","url":null,"abstract":"Reinforced concrete (RC) flat slab structure may suffer progressive collapse, which is usually caused by the punching shear failure of slab-column joints. Existing research has shown that the utilization of shear reinforcements or ultra-high toughness cementitious composite (UHTCC) in slab-column joints is efficient in improving their punching shear performance. In this study, shear reinforcement was introduced into UHTCC-enhanced RC slab-column joints. Specimens of UHTCC-enhanced slab-column joints considering the effect of shear reinforcements were tested. The cracking development process, bearing capacity, and ductility were analyzed. Yield line theory and critical shear crack theory were adopted to predict flexural and punching shear capacities, respectively. Finally, the failure patterns of the specimens were discriminated by comparing the predicted punching shear and flexural capacities, taking the ductile coefficient into account. The theoretical results combined with test results show the effect of shear reinforcement on the behavior of UHTCC-enhanced joints. Significant improvement in the bearing capacity and ductility of joints is achieved by applying shear reinforcement. The failure pattern of a joint varies from premature punching shear failure to flexural-triggered punching shear failure with the application of UHTCC, and this transform is more pronounced with shear reinforcement applied into the UHTCC-enhanced joint.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"7 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140812997","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}
In this paper, the possibility of utilizing coarse recycled concrete (CRCA) aggregate obtained from a Construction and Demolition Waste (CDW) Plant in Delhi for making a 60 MPa Self compacted concrete (SCC) was evaluated. The CRCA was used in as-collected condition and was not processed any further. Aggregate Packing (bulk) Density (APD) method was adopted to obtain an aggregate mixture exhibiting maximum bulk density/least void content (45%) with which the SCC-CRCA mixture was prepared. In addition, SCC was also made using aggregate mixtures in which the NCA was replaced with CRCA at 0%, 20%, and 100 % (of the total coarse aggregate content) by weight. The cement, fly ash, silica fume, and water were kept constant for all SCC mixtures. The effect of CRCA on the flow behavior, mechanical strength, shrinkage characteristics, and microstructure properties of SCC mixtures were evaluated. The test results indicated that the SCC mixtures made with CRCA up to 45% replacement can be used for structural concrete which is higher than that recommended in Indian (20 %) and International specifications (35 %) for traditionally vibrated (conventional) concrete.
{"title":"Engineering and microstructural properties of self-compacting concrete containing coarse recycled concrete aggregate","authors":"Dinesh Kumar, Kanta Rao, P. Lakshmy","doi":"10.1680/jmacr.23.00338","DOIUrl":"https://doi.org/10.1680/jmacr.23.00338","url":null,"abstract":"In this paper, the possibility of utilizing coarse recycled concrete (CRCA) aggregate obtained from a Construction and Demolition Waste (CDW) Plant in Delhi for making a 60 MPa Self compacted concrete (SCC) was evaluated. The CRCA was used in as-collected condition and was not processed any further. Aggregate Packing (bulk) Density (APD) method was adopted to obtain an aggregate mixture exhibiting maximum bulk density/least void content (45%) with which the SCC-CRCA mixture was prepared. In addition, SCC was also made using aggregate mixtures in which the NCA was replaced with CRCA at 0%, 20%, and 100 % (of the total coarse aggregate content) by weight. The cement, fly ash, silica fume, and water were kept constant for all SCC mixtures. The effect of CRCA on the flow behavior, mechanical strength, shrinkage characteristics, and microstructure properties of SCC mixtures were evaluated. The test results indicated that the SCC mixtures made with CRCA up to 45% replacement can be used for structural concrete which is higher than that recommended in Indian (20 %) and International specifications (35 %) for traditionally vibrated (conventional) concrete.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"16 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140615948","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}
Due to the demand for carbon neutrality, concrete carbonation has been reconsidered as an interesting topic because of its potential for capturing CO2 from the atmosphere. Concrete carbonation can significantly modify the chemical and microstructure properties of concrete and thus will have important effects on chloride diffusion. This paper presents a chloride diffusion model in which the concrete cover is divided into three different zones, each with their own defined porosity and chloride binding isotherm. One is the fully carbonated concrete near the surface, where the porosity and chloride binding isotherm can be obtained from the experimental data of fully carbonated concrete. One is the uncarbonated concrete near the reinforcement, where the porosity and chloride binding isotherm can be obtained from the experimental data of normal concrete. One is the transition zone between the fully carbonated and uncarbonated concretes, where the porosity and chloride binding isotherm can be assumed to vary continuously from the carbonated concrete to uncarbonated concrete. To validate the present model, the comparison of the present model with published experimental results is also provided, which demonstrates the importance of considering different zones in chloride diffusion model when the concrete has a carbonated layer near the surface.
{"title":"Modelling chloride diffusion in concrete with carbonated surface layer","authors":"Ping Li, Chuanfei Li, Dawang Li, Runhao Chen, Jinghong Chen","doi":"10.1680/jmacr.23.00202","DOIUrl":"https://doi.org/10.1680/jmacr.23.00202","url":null,"abstract":"Due to the demand for carbon neutrality, concrete carbonation has been reconsidered as an interesting topic because of its potential for capturing CO<sub>2</sub> from the atmosphere. Concrete carbonation can significantly modify the chemical and microstructure properties of concrete and thus will have important effects on chloride diffusion. This paper presents a chloride diffusion model in which the concrete cover is divided into three different zones, each with their own defined porosity and chloride binding isotherm. One is the fully carbonated concrete near the surface, where the porosity and chloride binding isotherm can be obtained from the experimental data of fully carbonated concrete. One is the uncarbonated concrete near the reinforcement, where the porosity and chloride binding isotherm can be obtained from the experimental data of normal concrete. One is the transition zone between the fully carbonated and uncarbonated concretes, where the porosity and chloride binding isotherm can be assumed to vary continuously from the carbonated concrete to uncarbonated concrete. To validate the present model, the comparison of the present model with published experimental results is also provided, which demonstrates the importance of considering different zones in chloride diffusion model when the concrete has a carbonated layer near the surface.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"69 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140582430","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}
Yeon-Back Jung, Ju-Hyun Mun, Sanghee Kim, Seung-Hyeon Hwang, Jae-Il Sim
This study examined the shear friction capacity of a monolithic concrete interface reinforced with newly developed self-prestressed reinforcing steel bars (SPRBs). Twelve push-off specimens with SPRBs were prepared according to the different compressive strengths of concrete (f′c) by applying compressive stresses (σx) on a monolithic concrete interface. To compare the shear friction capacities of monolithic concrete interfaces reinforced with conventional reinforcing bars, four companion specimens were prepared. The test results showed that the shear cracking and shear friction capacities were high for specimens with high f′c and σx values, resulting in the highest values for specimens with f′c = 40 MPa and σx = 0.5fy, where fy is the yield strength of the reinforcing steel bar. The test results confirmed that at a similar (ρvffy+σx)/f′c, a σx of more than 0.35fy is required for the SPRBs to achieve a λn value comparable to that of the specimens reinforced with conventional reinforcing bars, where ρvf is the transverse reinforcement ratio and λn is the shear friction capacity. The prediction models ACI 318-19 and AASHTO significantly underestimated the shear friction capacity with low accuracies. In particular, the difference between the experimental and underpredicted values became large as the (ρvffy+σx)/f′c value increased. However, the Mattock's model well-estimated the measured shear friction capacities of all the specimens tested in this study, irrespective of ρvffy and σx. Thus, the mean and standard deviation values of the measured-to-predicted shear friction capacity ratio were 1.07 and 0.13, respectively.
{"title":"Shear friction capacity of monolithic construction joints reinforced with self-prestressing reinforcing steel bars","authors":"Yeon-Back Jung, Ju-Hyun Mun, Sanghee Kim, Seung-Hyeon Hwang, Jae-Il Sim","doi":"10.1680/jmacr.23.00317","DOIUrl":"https://doi.org/10.1680/jmacr.23.00317","url":null,"abstract":"This study examined the shear friction capacity of a monolithic concrete interface reinforced with newly developed self-prestressed reinforcing steel bars (SPRBs). Twelve push-off specimens with SPRBs were prepared according to the different compressive strengths of concrete (<i>f</i>′<i><sub>c</sub></i>) by applying compressive stresses (<i>σ<sub>x</sub></i>) on a monolithic concrete interface. To compare the shear friction capacities of monolithic concrete interfaces reinforced with conventional reinforcing bars, four companion specimens were prepared. The test results showed that the shear cracking and shear friction capacities were high for specimens with high <i>f</i>′<i><sub>c</sub></i> and <i>σ<sub>x</sub></i> values, resulting in the highest values for specimens with <i>f</i>′<i><sub>c</sub></i> = 40 MPa and <i>σ<sub>x</sub></i> = 0.5<i>f<sub>y</sub></i>, where <i>f<sub>y</sub></i> is the yield strength of the reinforcing steel bar. The test results confirmed that at a similar (<i>ρ<sub>vf</sub>f<sub>y</sub></i>+<i>σ<sub>x</sub></i>)/<i>f</i>′<i><sub>c</sub></i>, a <i>σ<sub>x</sub></i> of more than 0.35<i>f<sub>y</sub></i> is required for the SPRBs to achieve a <i>λ<sub>n</sub></i> value comparable to that of the specimens reinforced with conventional reinforcing bars, where <i>ρ<sub>vf</sub></i> is the transverse reinforcement ratio and <i>λ<sub>n</sub></i> is the shear friction capacity. The prediction models ACI 318-19 and AASHTO significantly underestimated the shear friction capacity with low accuracies. In particular, the difference between the experimental and underpredicted values became large as the (<i>ρ<sub>vf</sub>f<sub>y</sub></i>+<i>σ<sub>x</sub></i>)/<i>f</i>′<i><sub>c</sub></i> value increased. However, the Mattock's model well-estimated the measured shear friction capacities of all the specimens tested in this study, irrespective of <i>ρ<sub>vf</sub>f<sub>y</sub></i> and <i>σ<sub>x</sub></i>. Thus, the mean and standard deviation values of the measured-to-predicted shear friction capacity ratio were 1.07 and 0.13, respectively.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"23 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140317005","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}
Across the world, the acceptance criterion for concrete made with non-potable water (SA) is stipulated for mean strength with reference to similar concrete made with potable water (SP). The basis for the strength design of concrete is the characteristic strength. The effect of the acceptance criteria on the characteristic strength of SA and SP was examined using statistical simulations, for the first time. It was found that, compared with a two-sample set, using a three-sample set would improve the characteristic strength of SA. A higher allowable ratio between the means of SA and SP and a lower deviation of individual samples from the mean would improve the characteristic strength of SA. The effect of the coefficient of variation (CoV) of the original population on the characteristic strength of SA varied. On the one hand, a higher CoV reduced the characteristic strength of SP, thereby increasing the probability of SA strength being higher than SP strength. On the other, a higher CoV of SP meant a wider spread of the samples and that could increase the CoV of SA, thereby reducing the characteristic strength of SA. Probabilistic charts were developed for the characteristic strengths of SA and SP for different combinations of the aforementioned variables, with guidance for practical application.
在世界各地，使用非饮用水（SA）制成的混凝土的验收标准是参照使用饮用水（SP）制成的类似混凝土的平均强度。混凝土强度设计的基础是特性强度。验收标准对 SA 和 SP 特性强度的影响首次通过统计模拟进行了研究。结果发现，与两组样本相比，三组样本可提高 SA 的特征强度。SA 和 SP 平均值之间的允许比率越高，单个样本与平均值的偏差越小，SA 的特征强度就越高。原始样本群的变异系数（CoV）对 SA 特征强度的影响各不相同。一方面，较高的 CoV 会降低 SP 的特征强度，从而增加 SA 强度高于 SP 强度的概率。另一方面，SP 的 CoV 越高，意味着样本的分布范围越广，这可能会增加 SA 的 CoV，从而降低 SA 的特征强度。针对上述变量的不同组合，为 SA 和 SP 的特征强度绘制了概率图，并为实际应用提供了指导。
{"title":"Probabilistic effect of non-potable mixing water on characteristic strength of concrete","authors":"Saha Dauji","doi":"10.1680/jmacr.23.00133","DOIUrl":"https://doi.org/10.1680/jmacr.23.00133","url":null,"abstract":"Across the world, the acceptance criterion for concrete made with non-potable water (SA) is stipulated for mean strength with reference to similar concrete made with potable water (SP). The basis for the strength design of concrete is the characteristic strength. The effect of the acceptance criteria on the characteristic strength of SA and SP was examined using statistical simulations, for the first time. It was found that, compared with a two-sample set, using a three-sample set would improve the characteristic strength of SA. A higher allowable ratio between the means of SA and SP and a lower deviation of individual samples from the mean would improve the characteristic strength of SA. The effect of the coefficient of variation (CoV) of the original population on the characteristic strength of SA varied. On the one hand, a higher CoV reduced the characteristic strength of SP, thereby increasing the probability of SA strength being higher than SP strength. On the other, a higher CoV of SP meant a wider spread of the samples and that could increase the CoV of SA, thereby reducing the characteristic strength of SA. Probabilistic charts were developed for the characteristic strengths of SA and SP for different combinations of the aforementioned variables, with guidance for practical application.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"10 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140311990","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}
A novel type of fiber, the double-helix macro BFRP (Basalt Fiber Reinforced Polymer) fiber, has been proposed to effectively increase the cracking, tensile strength, and ductility of concrete. BFRP material offers high tensile strength, good corrosion resistance, and low costs, while the double-helix geometry provides excellent bond-slip performance for the fiber and concrete matrix. This study conducted a series of three-point bending tests to measure the fracture energy of concrete reinforced with double-helix BFRP fibers and analyzed the influences of fiber orientation (aligned fibers and random fibers) on cracking loads, peak loads, flexural strengths, and fracture energy. The test results revealed a significant improvement in the fracture energy of concrete reinforced with double-helix macro BFRP fibers, with aligned fibers showing a 26.4% higher fracture energy compared to random fibers. Additionally, the flexural strength of concrete reinforced with aligned fibers increased by 29.7% compared to random fibers. Finite element models of the three-point bending tests were established using LS-DYNA software, and the concrete model developed by Karagozian & Case, Inc.(K&C) was calibrated based on the fracture energy results to obtain the material model of the fiber-reinforced concrete considering fiber orientation. The errors between the simulated and tested maximum load values for three-point bending tests of plain concrete, FRC, and FRCSS were 8.3%, 4.0%, and 11.4%, respectively, which indicates that the simulation results were found to be in good agreement with the test results. This study provides theoretical foundations and technical support for the practical engineering applications of double-helix BFRP fibers.
{"title":"Experimental and numerical investigations on fracture energy of double-helix macro BFRP fiber-reinforced concrete","authors":"Chunlei Zhang, Xuejie Zhang","doi":"10.1680/jmacr.23.00172","DOIUrl":"https://doi.org/10.1680/jmacr.23.00172","url":null,"abstract":"A novel type of fiber, the double-helix macro BFRP (Basalt Fiber Reinforced Polymer) fiber, has been proposed to effectively increase the cracking, tensile strength, and ductility of concrete. BFRP material offers high tensile strength, good corrosion resistance, and low costs, while the double-helix geometry provides excellent bond-slip performance for the fiber and concrete matrix. This study conducted a series of three-point bending tests to measure the fracture energy of concrete reinforced with double-helix BFRP fibers and analyzed the influences of fiber orientation (aligned fibers and random fibers) on cracking loads, peak loads, flexural strengths, and fracture energy. The test results revealed a significant improvement in the fracture energy of concrete reinforced with double-helix macro BFRP fibers, with aligned fibers showing a 26.4% higher fracture energy compared to random fibers. Additionally, the flexural strength of concrete reinforced with aligned fibers increased by 29.7% compared to random fibers. Finite element models of the three-point bending tests were established using LS-DYNA software, and the concrete model developed by Karagozian & Case, Inc.(K&C) was calibrated based on the fracture energy results to obtain the material model of the fiber-reinforced concrete considering fiber orientation. The errors between the simulated and tested maximum load values for three-point bending tests of plain concrete, FRC, and FRCSS were 8.3%, 4.0%, and 11.4%, respectively, which indicates that the simulation results were found to be in good agreement with the test results. This study provides theoretical foundations and technical support for the practical engineering applications of double-helix BFRP fibers.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"26 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140312441","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}
Xiao-Jun Ke, Zheng-Ren Chen, Chun-Ying Ye, Wan-Nian Xiang
Rubber concrete is a kind of light green building material, which is prepared by mixing rubber powder or rubber crumb into ordinary concrete in a certain proportion and then introducing rubber concrete through vibration-free technology to prepare self-compacting rubber concrete. Uniaxial compression tests were carried out on self-compacting rubber concrete with two particle sizes at different strain rates, and the effects of strain rate and rubber content on the dynamic mechanical properties of self-compacting rubber concrete were studied. The microstructure of self-compacting rubber concrete before and after damage was analyzed. Compared with ordinary concrete, the self-compacting rubber concrete is capable of maintaining good integrity during damage, when the rubber powder content exceeds 10% and the rubber crumb content exceeds 15%. The results indicate that as the strain rate increases, both the peak stress and the elastic modulus increase, indicating the strain rate enhancement effect, while the strain rate effect of the peak strain is not evident. Moreover, the model equations of peak stress and elastic modulus strain rate effect were established, the dynamic damage constitutive model was proposed, the damage evolution was analyzed, and the stress intervals were assigned to the various stages of damage evolution.
{"title":"Dynamic uniaxial compression mechanical properties of self-compacting rubber concrete subjected to different strain rates","authors":"Xiao-Jun Ke, Zheng-Ren Chen, Chun-Ying Ye, Wan-Nian Xiang","doi":"10.1680/jmacr.23.00274","DOIUrl":"https://doi.org/10.1680/jmacr.23.00274","url":null,"abstract":"Rubber concrete is a kind of light green building material, which is prepared by mixing rubber powder or rubber crumb into ordinary concrete in a certain proportion and then introducing rubber concrete through vibration-free technology to prepare self-compacting rubber concrete. Uniaxial compression tests were carried out on self-compacting rubber concrete with two particle sizes at different strain rates, and the effects of strain rate and rubber content on the dynamic mechanical properties of self-compacting rubber concrete were studied. The microstructure of self-compacting rubber concrete before and after damage was analyzed. Compared with ordinary concrete, the self-compacting rubber concrete is capable of maintaining good integrity during damage, when the rubber powder content exceeds 10% and the rubber crumb content exceeds 15%. The results indicate that as the strain rate increases, both the peak stress and the elastic modulus increase, indicating the strain rate enhancement effect, while the strain rate effect of the peak strain is not evident. Moreover, the model equations of peak stress and elastic modulus strain rate effect were established, the dynamic damage constitutive model was proposed, the damage evolution was analyzed, and the stress intervals were assigned to the various stages of damage evolution.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"47 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140311988","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 developed a novel ultra-high-performance concrete using calcium oxide-activated materials (UHPC-CAM) and modified synthetic macro and glass fibers. The mechanical and durability properties of the UHPC-CAM samples with different fiber types were tested and compared. The microstructure of the samples was examined by scanning electron microscopy (SEM). The environmental impacts of the mix designs were assessed by the IMPACT 2002+ method, a life cycle assessment (LCA) tool. The results showed that the UHPC-CAM had a high compressive strength of over 110 MPa and improved ductility when glass and synthetic macro fibers were used. The samples also had low water absorption and high electrical resistance, indicating low corrosion risk. The SEM analyses showed that the synthetic macro fibers created a denser geopolymer matrix than the glass fibers. The UHPC-CAM had lower environmental impacts than conventional UHPC in terms of human health, ecosystem quality, carbon footprint, and resources. Synthetic macro fibers were the most eco-friendly fibers for UHPC-CAM production.
{"title":"A novel development of ultra-high-performance concrete with calcium oxide-activated materials and fibers: engineering properties and sustainability evaluation","authors":"Hadi Bahmani, Davood Mostofinejad","doi":"10.1680/jmacr.23.00234","DOIUrl":"https://doi.org/10.1680/jmacr.23.00234","url":null,"abstract":"This study developed a novel ultra-high-performance concrete using calcium oxide-activated materials (UHPC-CAM) and modified synthetic macro and glass fibers. The mechanical and durability properties of the UHPC-CAM samples with different fiber types were tested and compared. The microstructure of the samples was examined by scanning electron microscopy (SEM). The environmental impacts of the mix designs were assessed by the IMPACT 2002+ method, a life cycle assessment (LCA) tool. The results showed that the UHPC-CAM had a high compressive strength of over 110 MPa and improved ductility when glass and synthetic macro fibers were used. The samples also had low water absorption and high electrical resistance, indicating low corrosion risk. The SEM analyses showed that the synthetic macro fibers created a denser geopolymer matrix than the glass fibers. The UHPC-CAM had lower environmental impacts than conventional UHPC in terms of human health, ecosystem quality, carbon footprint, and resources. Synthetic macro fibers were the most eco-friendly fibers for UHPC-CAM production.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"143 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140311986","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}
Senthil Kumar Kaliyavaradhan, P. S. Ambily, Deepadharshan Shekar, Shilpa Sebastian
Sand is frequently used as a fine aggregate in concrete mixtures, however, the performance of concrete can be considerably impacted by regional variations in sand gradation. This study systematically investigated the effect of sand gradations on fresh properties of 3D printable concrete (3DPC) mixtures. The binder combinations, including cement, fly ash, silica fume, limestone powder, ground granulated blast furnace slag, and the water-to-binder ratio, were constant throughout the trials. The mini-slump height and flow values of optimal packing of binary and ternary combinations of standard Ennore sand (Grade I, Grade II, Grade III) compared to locally available river sand and the unary packing of Ennore sand and river sand. In addition, the correlation between the fineness modulus of different sand gradations and printable flow time were determined. The influence of sand gradations and fineness modulus on buildability, shape retention, open time and extrudability were evaluated. The findings demonstrated that the performance of the fresh 3DPC is influenced by the aggregate's gradation and grain size in addition to its fineness. In conclusion, different fine aggregate specifications must be chosen depending on the various 3D printing building conditions and design requirements.
砂通常用作混凝土混合物中的细骨料，然而，砂级配的地区差异会对混凝土的性能产生很大影响。本研究系统地研究了砂子级配对三维可打印混凝土（3DPC）混合物新拌性能的影响。在整个试验过程中，水泥、粉煤灰、硅灰、石灰石粉、磨细高炉矿渣等粘结剂组合以及水与粘结剂的比例保持不变。将标准恩诺尔砂（一级、二级、三级）的二元和三元组合的最佳填料与当地可用的河砂以及恩诺尔砂和河砂的单元填料进行比较，得出了小坍落度高度和流动值。此外，还测定了不同砂级配的细度模数与可印刷流动时间之间的相关性。评估了砂的级配和细度模数对施工性、形状保持性、开放时间和挤出性的影响。研究结果表明，除细度外，新鲜 3DPC 的性能还受到骨料级配和粒度的影响。总之，必须根据不同的 3D 打印建筑条件和设计要求选择不同的细骨料规格。
{"title":"Effect of sand gradations on the fresh properties of 3D printable concrete","authors":"Senthil Kumar Kaliyavaradhan, P. S. Ambily, Deepadharshan Shekar, Shilpa Sebastian","doi":"10.1680/jmacr.23.00166","DOIUrl":"https://doi.org/10.1680/jmacr.23.00166","url":null,"abstract":"Sand is frequently used as a fine aggregate in concrete mixtures, however, the performance of concrete can be considerably impacted by regional variations in sand gradation. This study systematically investigated the effect of sand gradations on fresh properties of 3D printable concrete (3DPC) mixtures. The binder combinations, including cement, fly ash, silica fume, limestone powder, ground granulated blast furnace slag, and the water-to-binder ratio, were constant throughout the trials. The mini-slump height and flow values of optimal packing of binary and ternary combinations of standard Ennore sand (Grade I, Grade II, Grade III) compared to locally available river sand and the unary packing of Ennore sand and river sand. In addition, the correlation between the fineness modulus of different sand gradations and printable flow time were determined. The influence of sand gradations and fineness modulus on buildability, shape retention, open time and extrudability were evaluated. The findings demonstrated that the performance of the fresh 3DPC is influenced by the aggregate's gradation and grain size in addition to its fineness. In conclusion, different fine aggregate specifications must be chosen depending on the various 3D printing building conditions and design requirements.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":"29 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140312268","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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