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":null,"pages":null},"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}
Mohamed O. Mohsen, Mervat O. Aburumman, Malak M. Al-diseet, Mu'tasim Abdel-Jaber, Ramzi Taha, Mohamed S. Al Ansari, Ahmed Senouci, A. A. Taqa
This paper investigates the effect of Graphene Nanoplatelets’ (GNPs) content on sustainable concrete mechanical properties and microstructure. Aqueous solutions were prepared using a wet-dispersion technique to disperse GNPs in the mixing water. Concrete batches were prepared using GNPs-to-cement ratios of 0.05, 0.1, 0.25, 0.5, 1 and 2 %. The 28 day compressive, flexural, and tensile strengths of the prepared specimens were then determined. Moreover, specimen qualitative microstructural analyses were performed using a Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX). The results obtained were then analyzed using ANOVA method that demonstrated improvements in all strength properties when using GNPs’ filaments regardless of their weight fraction. The batch containing 0.5 % GNPs had the largest strength improvements where the mix of compressive, flexural, and tensile strength properties could be improved by 22.6%, 23.9% and 255.4 %, respectively. The microstructure analysis showed a good dispersion of nanofilaments inside the concrete matrix using the dispersion technique utilized in this study. Finally, the ANOVA analysis reveals statistically significant relationships between the GNPs’ content ratio and compressive, flexural, and tensile strengths in the concrete samples. The results highlight the importance of the GNPs’ content ratio in influencing the concrete's mechanical properties.
{"title":"The influence of graphene nanoplatelets’ content on sustainable concrete mechanical properties and microstructure","authors":"Mohamed O. Mohsen, Mervat O. Aburumman, Malak M. Al-diseet, Mu'tasim Abdel-Jaber, Ramzi Taha, Mohamed S. Al Ansari, Ahmed Senouci, A. A. Taqa","doi":"10.1680/jmacr.23.00238","DOIUrl":"https://doi.org/10.1680/jmacr.23.00238","url":null,"abstract":"This paper investigates the effect of Graphene Nanoplatelets’ (GNPs) content on sustainable concrete mechanical properties and microstructure. Aqueous solutions were prepared using a wet-dispersion technique to disperse GNPs in the mixing water. Concrete batches were prepared using GNPs-to-cement ratios of 0.05, 0.1, 0.25, 0.5, 1 and 2 %. The 28 day compressive, flexural, and tensile strengths of the prepared specimens were then determined. Moreover, specimen qualitative microstructural analyses were performed using a Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX). The results obtained were then analyzed using ANOVA method that demonstrated improvements in all strength properties when using GNPs’ filaments regardless of their weight fraction. The batch containing 0.5 % GNPs had the largest strength improvements where the mix of compressive, flexural, and tensile strength properties could be improved by 22.6%, 23.9% and 255.4 %, respectively. The microstructure analysis showed a good dispersion of nanofilaments inside the concrete matrix using the dispersion technique utilized in this study. Finally, the ANOVA analysis reveals statistically significant relationships between the GNPs’ content ratio and compressive, flexural, and tensile strengths in the concrete samples. The results highlight the importance of the GNPs’ content ratio in influencing the concrete's mechanical properties.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140210967","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":null,"pages":null},"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}
Xuan'ang Jiang, Liu Jin, Peng Qin, Maoxin Xia, X. Du
CFRP (Carbon Fiber Reinforced Plastics) debonding jeopardizes structural reinforcement in engineering projects. Anchoring CFRP paste is crucial for efficient shear strengthening. This study investigates the anchoring effect on shear resistance in nine CFRP U-wrapped concrete beams, varying shear span-to-depth ratios (1.0, 1.5, 2.0), and depths from 300 mm to 900 mm. Concurrently, nine unanchored beams and nine plain concrete beams were included in the comparison, considering the influence of beam depth and shear span ratio, referencing the prior research of Jiang et al. (2022). The evaluation of the shear contribution of CFRP with different sizes, particularly in scenarios involving large dimensions and diverse shear span ratios, was conducted. The test results revealed that the anchoring effect is most pronounced in small-scale beams with a large shear span ratio, demonstrating an improvement of over 60% compared to the CFRP shear-strengthened beam without anchoring. In contrast to beams without CFRP wrapping, the shear performance was enhanced by approximately 90%. Additionally, the study analyzed and compared the calculation formulas of shear capacity from different national specifications. Ultimately, a calculation method for CFRP shear resistance was established and its accuracy was verified.
{"title":"Shear contribution of beams having different structural sizes strengthened in shear with anchored CFRP strips","authors":"Xuan'ang Jiang, Liu Jin, Peng Qin, Maoxin Xia, X. Du","doi":"10.1680/jmacr.23.00287","DOIUrl":"https://doi.org/10.1680/jmacr.23.00287","url":null,"abstract":"CFRP (Carbon Fiber Reinforced Plastics) debonding jeopardizes structural reinforcement in engineering projects. Anchoring CFRP paste is crucial for efficient shear strengthening. This study investigates the anchoring effect on shear resistance in nine CFRP U-wrapped concrete beams, varying shear span-to-depth ratios (1.0, 1.5, 2.0), and depths from 300 mm to 900 mm. Concurrently, nine unanchored beams and nine plain concrete beams were included in the comparison, considering the influence of beam depth and shear span ratio, referencing the prior research of Jiang et al. (2022). The evaluation of the shear contribution of CFRP with different sizes, particularly in scenarios involving large dimensions and diverse shear span ratios, was conducted. The test results revealed that the anchoring effect is most pronounced in small-scale beams with a large shear span ratio, demonstrating an improvement of over 60% compared to the CFRP shear-strengthened beam without anchoring. In contrast to beams without CFRP wrapping, the shear performance was enhanced by approximately 90%. Additionally, the study analyzed and compared the calculation formulas of shear capacity from different national specifications. Ultimately, a calculation method for CFRP shear resistance was established and its accuracy was verified.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140254418","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 performance of repair materials is greatly enhanced by the integrity of the rehabilitation system, which depends on the behaviour of the boundary or interface bond between the repair material and the concrete substrate. The current study investigated the effect of implementation method of repair materials (cast or spray method), spraying direction, and concrete substrate roughness on the interfacial bond behaviour experimentally by using the four-point bending test on prism samples with dimensions of 300×76.2×40 mm. At first, the concrete substrate was made with a thickness of 2 cm, and its surface was considered proportional to the five surfaces. After 28 days curing, the repair material was poured into specific molds and sprayed. The repair material used herein was a high-performance (high ductility) fibre-reinforced cementitious composite (HPFRCC) developed with local materials and a tensile strain capacity of 3.7%. The results demonstrated that spraying direction and surface roughness of the concrete substrate significantly impact the ultimate deflection rate; upward spraying had the lowest and downward spraying the highest deflection rate. Furthermore, because beams are often repaired from the lower part, and the spraying is upward, the cast method must be used because of the negative effect of gravity on the interfacial bonding between the concrete substrate and the repair material.
{"title":"Impacts of interfacial bonding between concrete substrate and cast/sprayable HPFRCC on flexural behaviour","authors":"Sajjad Mirzamohammadi, Masoud Soltani","doi":"10.1680/jmacr.23.00249","DOIUrl":"https://doi.org/10.1680/jmacr.23.00249","url":null,"abstract":"The performance of repair materials is greatly enhanced by the integrity of the rehabilitation system, which depends on the behaviour of the boundary or interface bond between the repair material and the concrete substrate. The current study investigated the effect of implementation method of repair materials (cast or spray method), spraying direction, and concrete substrate roughness on the interfacial bond behaviour experimentally by using the four-point bending test on prism samples with dimensions of 300×76.2×40 mm. At first, the concrete substrate was made with a thickness of 2 cm, and its surface was considered proportional to the five surfaces. After 28 days curing, the repair material was poured into specific molds and sprayed. The repair material used herein was a high-performance (high ductility) fibre-reinforced cementitious composite (HPFRCC) developed with local materials and a tensile strain capacity of 3.7%. The results demonstrated that spraying direction and surface roughness of the concrete substrate significantly impact the ultimate deflection rate; upward spraying had the lowest and downward spraying the highest deflection rate. Furthermore, because beams are often repaired from the lower part, and the spraying is upward, the cast method must be used because of the negative effect of gravity on the interfacial bonding between the concrete substrate and the repair material.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140253650","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}
To study the influence of hydraulic pressure on pore structure evolution and chloride transport behavior in concrete, the mass transport depth, chloride concentration, and pore characteristics of specimens with different water-cement ratios were investigated using silver nitrate spraying, potentiometric titration, the mercury intrusion porosimetry (MIP) method, N2 adsorption method, and laser confocal microscopy. The results showed that chloride concentration increases as the hydraulic pressure and the water-cement ratio increase. As this hydraulic pressure increases, the difference between water and chloride ion transport distinctive characteristics becomes conspicuously pronounced, extending from 5.2 mm to 25.4 mm in distance. The hydraulic pressure changes the pore structure of the concrete, leading to a surge in the specific surface area, larger porosity, and average pore diameters. Notably, ink-bottle-type pores emerge prominently and the proportion of fine mesopores and capillary pores markedly rises after the application of hydraulic pressure. Furthermore, a relationship between chloride diffusion coefficient and hydraulic pressure is suggested. A relationship between the modified permeability coefficient and hydraulic pressure is constructed based on the mesoporous contribution β to express the hysteresis effect of chloride.
{"title":"Influence of hydraulic pressure on pore structure evolution and chloride transport in concrete","authors":"Jie Chen, Jin Xia, Renjie Wu, Yu Peng","doi":"10.1680/jmacr.23.00283","DOIUrl":"https://doi.org/10.1680/jmacr.23.00283","url":null,"abstract":"To study the influence of hydraulic pressure on pore structure evolution and chloride transport behavior in concrete, the mass transport depth, chloride concentration, and pore characteristics of specimens with different water-cement ratios were investigated using silver nitrate spraying, potentiometric titration, the mercury intrusion porosimetry (MIP) method, N2 adsorption method, and laser confocal microscopy. The results showed that chloride concentration increases as the hydraulic pressure and the water-cement ratio increase. As this hydraulic pressure increases, the difference between water and chloride ion transport distinctive characteristics becomes conspicuously pronounced, extending from 5.2 mm to 25.4 mm in distance. The hydraulic pressure changes the pore structure of the concrete, leading to a surge in the specific surface area, larger porosity, and average pore diameters. Notably, ink-bottle-type pores emerge prominently and the proportion of fine mesopores and capillary pores markedly rises after the application of hydraulic pressure. Furthermore, a relationship between chloride diffusion coefficient and hydraulic pressure is suggested. A relationship between the modified permeability coefficient and hydraulic pressure is constructed based on the mesoporous contribution β to express the hysteresis effect of chloride.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140254525","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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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}
To reduce the environmental pollution and conserve the natural resources, this study utilized the calcined oyster shell ash (COSA), Class F fly ash (FFA), and flue gas desulphurization (FGD) gypsum to improve the engineering properties of alkali-activated ternary cementitious paste. The COSA was obtained by calcining the crushed oyster shell at 800°C for three hours and then ground to pass through sieved No. 100, which was used to substitute FFA with 2.5, 5, and 7.5 mass(%). The alkali solution was composed of 10M sodium hydroxide (NaOH) and sodium silicate (SS) with modulus 2.5. The hardened paste with 7.5% of COSA, 1.0% of FGD gypsum, and the mass of added water to dry binder (Waw/WB) of 0.09 at age of 56 days had the highest compressive strength of 62 MPa. The microstructural analyses of SEM and EDS showed that the resulting calcium alumino-silicates hydrates (C-A-S-H) gel was found to have compact microstructure and improve the compressive strength of specimens. This indicates that the COSA has successfully replaced the natural limestone as CaO activator to manufacture the alkali-activated ternary cementitious paste together with the FFA and FGD gypsum.
{"title":"Improvement on engineering properties of alkali activated ternary cementitious paste with calcined oyster shell ash and flue gas desulfurization gypsum","authors":"Stella Patricia Angdiarto, Chun-Tao Chen, Ta-Peng Chang, Jeng-Ywan Shih","doi":"10.1680/jmacr.23.00106","DOIUrl":"https://doi.org/10.1680/jmacr.23.00106","url":null,"abstract":"To reduce the environmental pollution and conserve the natural resources, this study utilized the calcined oyster shell ash (COSA), Class F fly ash (FFA), and flue gas desulphurization (FGD) gypsum to improve the engineering properties of alkali-activated ternary cementitious paste. The COSA was obtained by calcining the crushed oyster shell at 800°C for three hours and then ground to pass through sieved No. 100, which was used to substitute FFA with 2.5, 5, and 7.5 mass(%). The alkali solution was composed of 10M sodium hydroxide (NaOH) and sodium silicate (SS) with modulus 2.5. The hardened paste with 7.5% of COSA, 1.0% of FGD gypsum, and the mass of added water to dry binder (Waw/WB) of 0.09 at age of 56 days had the highest compressive strength of 62 MPa. The microstructural analyses of SEM and EDS showed that the resulting calcium alumino-silicates hydrates (C-A-S-H) gel was found to have compact microstructure and improve the compressive strength of specimens. This indicates that the COSA has successfully replaced the natural limestone as CaO activator to manufacture the alkali-activated ternary cementitious paste together with the FFA and FGD gypsum.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139960190","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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