This paper investigates the effects of pozzolanic substitutions for ordinary Portland cement (OPC) with silica fume (SF) and metakaolin (MK) on the mechanical and toughness performances of steel fiber reinforced concrete (SFRC). Initially, a reference concrete mix with a water‐to‐binder ratio of 0.4 is blended with different volume fractions of steel fibers with varying geometry: crimped steel (CS) and straight steel (SS), both individually and in combination, to examine their mechanical properties. In the subsequent phase, the study investigates the impact of combining macro‐ and microsteel fibers on flexural toughness, to determine potential synergy for suitable combinations. Also, the possible influence of pozzolans in the variation of flexural toughness of hybrid steel fiber reinforced concrete (Hy‐SFRC) was evaluated. Hybridization of steel fibers was found effective in improving the workability of the concrete mix up to 11%. SFRC mixes containing pozzolans exhibited a significant enhancement in compressive strength, modulus of rupture, and modulus of elasticity compared to non‐pozzolanic SFRC. The hybrid combination of CS 1.5% and SS 0.5% was considered the best in terms of mechanical properties. Additionally, the results of synergy assessment showed that hybridization of steel fibers in the pozzolanic concrete mix was particularly effective in the post‐cracking stages with a positive 14% compared to a negative 8% in the pre‐cracking stage. The pozzolanic addition improved the flexural toughness of Hy‐SFRC to about 10%–20%. Blending of SF and MK in Hy‐SFRC was found effective in enhancing the toughness mechanism of concrete compared to Hy‐SFRC mixes containing binary SF and MK, indicating a stronger bond between the fibers and the matrix resulting from the pore refinement and hydration products developed at the interface. Hy‐SFRC containing a ternary pozzolanic mix of SF 10% and MK 10% gave the best results in flexural toughness, and the corresponding synergy values were found to be the maximum. The results were consistent with the morphology analysis, which revealed an increase in hydration products at the interface between the aggregate and concrete matrix, as well as between the steel fiber and concrete matrix, due to the ternary blending of SF and MK.
本文研究了用硅灰（SF）和偏高岭土（MK）替代普通硅酸盐水泥（OPC）对钢纤维增强混凝土（SFRC）机械性能和韧性的影响。首先，在水胶比为 0.4 的参考混凝土拌合物中掺入不同体积分数的不同几何形状的钢纤维：卷曲钢纤维 (CS) 和直钢纤维 (SS)，既可单独使用，也可混合使用，以检验其力学性能。在随后的阶段，研究将宏观钢纤维和微观钢纤维结合在一起对弯曲韧性的影响，以确定合适组合的潜在协同作用。此外，研究还评估了混合钢纤维增强混凝土（Hy-SFRC）的抗弯韧度变化中可能存在的胶凝剂影响。结果发现，钢纤维杂化可有效改善混凝土拌合物的工作性，最高可达 11%。与不含胶结剂的 SFRC 相比，含胶结剂的 SFRC 混合物在抗压强度、断裂模量和弹性模量方面都有显著提高。CS 1.5% 和 SS 0.5% 的混合组合被认为是力学性能最佳的组合。此外，协同作用评估结果表明，在含毛细管的混凝土拌合物中混合钢纤维在开裂后阶段特别有效，正效应为 14%，而在开裂前阶段则为负 8%。添加水青石后，Hy-SFRC 的弯曲韧性提高了约 10%-20%。与含有二元 SF 和 MK 的 Hy-SFRC 混合物相比，在 Hy-SFRC 中混合 SF 和 MK 能有效增强混凝土的韧性机制，这表明纤维与基体之间的粘结力更强，这是由于孔隙细化和水化产物在界面上形成的结果。含有 10% SF 和 10% MK 的三元水合混合料的 Hy-SFRC 在弯曲韧性方面效果最好，相应的协同值也最大。结果与形态分析一致，形态分析表明，由于 SF 和 MK 的三元混合，骨料与混凝土基体之间以及钢纤维与混凝土基体之间的界面水化产物有所增加。
{"title":"Experimental investigations on mechanical performance, synergy assessment, and microstructure of pozzolanic and non‐pozzolanic hybrid steel fiber reinforced concrete","authors":"Sankar Boomibalan, Haytham F. Isleem, Packirisamy Swaminathan, Deivasigamani Rameshkumar, Arunkumar Kadarkarai","doi":"10.1002/suco.202400693","DOIUrl":"https://doi.org/10.1002/suco.202400693","url":null,"abstract":"This paper investigates the effects of pozzolanic substitutions for ordinary Portland cement (OPC) with silica fume (SF) and metakaolin (MK) on the mechanical and toughness performances of steel fiber reinforced concrete (SFRC). Initially, a reference concrete mix with a water‐to‐binder ratio of 0.4 is blended with different volume fractions of steel fibers with varying geometry: crimped steel (CS) and straight steel (SS), both individually and in combination, to examine their mechanical properties. In the subsequent phase, the study investigates the impact of combining macro‐ and microsteel fibers on flexural toughness, to determine potential synergy for suitable combinations. Also, the possible influence of pozzolans in the variation of flexural toughness of hybrid steel fiber reinforced concrete (Hy‐SFRC) was evaluated. Hybridization of steel fibers was found effective in improving the workability of the concrete mix up to 11%. SFRC mixes containing pozzolans exhibited a significant enhancement in compressive strength, modulus of rupture, and modulus of elasticity compared to non‐pozzolanic SFRC. The hybrid combination of CS 1.5% and SS 0.5% was considered the best in terms of mechanical properties. Additionally, the results of synergy assessment showed that hybridization of steel fibers in the pozzolanic concrete mix was particularly effective in the post‐cracking stages with a positive 14% compared to a negative 8% in the pre‐cracking stage. The pozzolanic addition improved the flexural toughness of Hy‐SFRC to about 10%–20%. Blending of SF and MK in Hy‐SFRC was found effective in enhancing the toughness mechanism of concrete compared to Hy‐SFRC mixes containing binary SF and MK, indicating a stronger bond between the fibers and the matrix resulting from the pore refinement and hydration products developed at the interface. Hy‐SFRC containing a ternary pozzolanic mix of SF 10% and MK 10% gave the best results in flexural toughness, and the corresponding synergy values were found to be the maximum. The results were consistent with the morphology analysis, which revealed an increase in hydration products at the interface between the aggregate and concrete matrix, as well as between the steel fiber and concrete matrix, due to the ternary blending of SF and MK.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"352 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141777088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gold tailings is formed as an industrial waste during gold mining and processing. The aim of the current study is to use it to prepare foamed concrete as subgrade filler. The effect of wet density (600, 700 and 800 kg/m3) and tailings content (15, 30, 45 and 60 wt%) on fluidity, compressive strength, elastic modulus, drying shrinkage, freeze–thaw resistance, hydration heat and pore structure were investigated. It was found that incorporating tailings into foamed concrete decreases the compressive strength as tailings adversely affected the pore structure, resulting in increased porosity, enlarged and connected pores, and reduced sphericity. To meet the requirement of subgrade filler, the tailings content was limited to 30 wt% when the designed wet density was 600 kg/m3 and it was 45 wt% when the wet density increased to 700 and 800 kg/m3. Nevertheless, increasing the tailings content effectively reduced the drying shrinkage and early age hydration heat which are favorable for massive foamed concrete construction. Besides, the incorporation of gold tailings is helpful to the freeze–thaw resistance of 600 and 700 kg/m3 foamed concrete for application in seasonal frozen areas.
{"title":"Properties of lightweight foamed concrete containing gold tailings as subgrade filler","authors":"Quping Liang, Shengtao Zhang, Ning Zhang, Zhi Ge, Leyang Lv, Yifeng Ling, Hongzhi Zhang","doi":"10.1002/suco.202300580","DOIUrl":"https://doi.org/10.1002/suco.202300580","url":null,"abstract":"Gold tailings is formed as an industrial waste during gold mining and processing. The aim of the current study is to use it to prepare foamed concrete as subgrade filler. The effect of wet density (600, 700 and 800 kg/m<jats:sup>3</jats:sup>) and tailings content (15, 30, 45 and 60 wt%) on fluidity, compressive strength, elastic modulus, drying shrinkage, freeze–thaw resistance, hydration heat and pore structure were investigated. It was found that incorporating tailings into foamed concrete decreases the compressive strength as tailings adversely affected the pore structure, resulting in increased porosity, enlarged and connected pores, and reduced sphericity. To meet the requirement of subgrade filler, the tailings content was limited to 30 wt% when the designed wet density was 600 kg/m<jats:sup>3</jats:sup> and it was 45 wt% when the wet density increased to 700 and 800 kg/m<jats:sup>3</jats:sup>. Nevertheless, increasing the tailings content effectively reduced the drying shrinkage and early age hydration heat which are favorable for massive foamed concrete construction. Besides, the incorporation of gold tailings is helpful to the freeze–thaw resistance of 600 and 700 kg/m<jats:sup>3</jats:sup> foamed concrete for application in seasonal frozen areas.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"12 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141777089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thamer Alomayri, Ali Raza, Khaled Mohamed Elhadi, Faiz Shaikh
Cement production is responsible for 5%–7% of global CO2 emissions, highlighting the need for sustainable alternatives like geopolymer composite (GCOMP) to meet the growing demand for concrete. This study investigates the mechanical, microstructural, and thermal properties of GCOMP by incorporating nano‐alumina (n‐alumina) and MSF (MSF). The n‐alumina content was varied at 1%, 2%, and 3% by weight of the mix, while the MSF content remained fixed at 0.5% by weight. Thermal characterization was conducted up to 800°C. The performance of GCOMP blends with n‐alumina was compared to a control blend consisting of only 0.5% MSF. Various mechanical properties were evaluated for all GCOMP blends. Microstructural and mineralogical characteristics were analyzed using scanning electron microscopy (SEM), X‐ray diffraction (XRD), and Fourier‐transform infrared spectroscopy (FTIR). Thermogravimetric and differential thermal analysis were performed up to 800°C for the thermal analysis of the GCOMP mix. The results indicate that the optimal mechanical properties were achieved with 2% n‐alumina (compressive and flexural strength increased by 35.65% and 77.7%, respectively). Additionally, the incorporation of n‐alumina improves the interfacial zones and results in a denser structure. GCOMP mortars portrayed a mass loss between 25°C and 250°C, with a marginal mass loss occurring between 250°C and 715°C. No mass loss was observed between 715°C and 800°C. The MSF‐reinforced GCOMP mortars experienced an ultimate mass loss of approximately 12%, with the MSF showing negligible influence. The addition of n‐alumina particles to MSF‐reinforced GCOMP resulted in the development of stronger samples characterized by the presence of C–S–H, calcium aluminate oxide hydroxide, and quartz.
{"title":"Mechanical, microstructural, and thermal characterization of geopolymer composites with nano‐alumina particles and micro steel fibers","authors":"Thamer Alomayri, Ali Raza, Khaled Mohamed Elhadi, Faiz Shaikh","doi":"10.1002/suco.202400477","DOIUrl":"https://doi.org/10.1002/suco.202400477","url":null,"abstract":"Cement production is responsible for 5%–7% of global CO<jats:sub>2</jats:sub> emissions, highlighting the need for sustainable alternatives like geopolymer composite (GCOMP) to meet the growing demand for concrete. This study investigates the mechanical, microstructural, and thermal properties of GCOMP by incorporating nano‐alumina (<jats:italic>n</jats:italic>‐alumina) and MSF (MSF). The <jats:italic>n</jats:italic>‐alumina content was varied at 1%, 2%, and 3% by weight of the mix, while the MSF content remained fixed at 0.5% by weight. Thermal characterization was conducted up to 800°C. The performance of GCOMP blends with <jats:italic>n</jats:italic>‐alumina was compared to a control blend consisting of only 0.5% MSF. Various mechanical properties were evaluated for all GCOMP blends. Microstructural and mineralogical characteristics were analyzed using scanning electron microscopy (SEM), X‐ray diffraction (XRD), and Fourier‐transform infrared spectroscopy (FTIR). Thermogravimetric and differential thermal analysis were performed up to 800°C for the thermal analysis of the GCOMP mix. The results indicate that the optimal mechanical properties were achieved with 2% <jats:italic>n</jats:italic>‐alumina (compressive and flexural strength increased by 35.65% and 77.7%, respectively). Additionally, the incorporation of <jats:italic>n</jats:italic>‐alumina improves the interfacial zones and results in a denser structure. GCOMP mortars portrayed a mass loss between 25°C and 250°C, with a marginal mass loss occurring between 250°C and 715°C. No mass loss was observed between 715°C and 800°C. The MSF‐reinforced GCOMP mortars experienced an ultimate mass loss of approximately 12%, with the MSF showing negligible influence. The addition of <jats:italic>n</jats:italic>‐alumina particles to MSF‐reinforced GCOMP resulted in the development of stronger samples characterized by the presence of C–S–H, calcium aluminate oxide hydroxide, and quartz.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"63 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jacob Yager, Evan C. Bentz, Joshua E. Woods, Neil A. Hoult
Distributed fiber optic sensors (DFOS) allow for the measurement of distributed strains on concrete surfaces and along steel reinforcement in reinforced concrete (RC) members, and these measurements can quantify reinforcement and concrete behavior. In this investigation, concrete surface and reinforcement strains from DFOS were used to quantify and compare the structural behavior of lightly and moderately reinforced one‐way slabs strips to better characterize localized strain behavior of lightly reinforced RC members with small diameter bars (10 M). By quantifying the entire compression region and reinforcement strain behavior, various structural parameters, such as curvature, strain profiles over the height at various locations, and neutral axis depth were calculated. From the distributed properties, it was determined that significant differences in behavior existed between moderately and lightly reinforced specimens with small diameter bars, with the lightly reinforced specimen displaying non‐uniform behavior along its length. Differences observed in the lightly reinforced member with small diameter bars include local curvature differences both at a crack and between cracks, local evidence of plane sections not remaining plane, possible different internal cracking mechanisms, amongst other local strain behavior differences, which could have implications for future modeling and design of lightly reinforced RC members with small diameter bars.
{"title":"Revealing fundamental flexural behavior of reinforced concrete slabs using distributed fiber optic sensors","authors":"Jacob Yager, Evan C. Bentz, Joshua E. Woods, Neil A. Hoult","doi":"10.1002/suco.202400063","DOIUrl":"https://doi.org/10.1002/suco.202400063","url":null,"abstract":"Distributed fiber optic sensors (DFOS) allow for the measurement of distributed strains on concrete surfaces and along steel reinforcement in reinforced concrete (RC) members, and these measurements can quantify reinforcement and concrete behavior. In this investigation, concrete surface and reinforcement strains from DFOS were used to quantify and compare the structural behavior of lightly and moderately reinforced one‐way slabs strips to better characterize localized strain behavior of lightly reinforced RC members with small diameter bars (10 M). By quantifying the entire compression region and reinforcement strain behavior, various structural parameters, such as curvature, strain profiles over the height at various locations, and neutral axis depth were calculated. From the distributed properties, it was determined that significant differences in behavior existed between moderately and lightly reinforced specimens with small diameter bars, with the lightly reinforced specimen displaying non‐uniform behavior along its length. Differences observed in the lightly reinforced member with small diameter bars include local curvature differences both at a crack and between cracks, local evidence of plane sections not remaining plane, possible different internal cracking mechanisms, amongst other local strain behavior differences, which could have implications for future modeling and design of lightly reinforced RC members with small diameter bars.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"37 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141740610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Robert Haigh, Malindu Sandanayake, Paul Joseph, Ehsan Yaghoubi, Zora Vrcelj
Waste fiber reinforced concrete is gaining recognition as a high‐performance construction material, offering notable load‐bearing capacity, corrosion resistance, and enhanced durability features. As the building and construction industry focuses on sustainable practices, fibers derived from waste materials create an opportunity to be utilized further in composite designs. This study explores the tensile, compressive, and flexural behaviors of cardboard fibers (kraft fibers) and textile polyester fibers in concrete materials. The composite microstructure is also investigated using a scanning electron microscope (SEM) to measure the bonding performance of the fibers within the cementitious matrix. Four mix designs were created using 2.5% textile fibers as a reinforcement agent and 5% silica fume modified kraft fibers (SFKFs) as a partial cement replacement. The combination of fibers achieved 44 MPa compressive strength, equaling the control. Tensile strength was enhanced by 5% when using the combination of the two fibers, achieving 3.58 MPa in comparison to 3.41 MPa. However, flexural strength was reduced among all fibrous concrete materials. SEM images distinguished the natural and synthetic characteristics associated with the two fibers within the cementitious matrix. Namely, demonstrating the chemical bonding of SFKFs in comparison with the physical bonding properties of the textile fibers. This study serves as a valuable resource for future investigations and the broader adoption of binary waste fiber composite designs in cementitious composite applications.
{"title":"The mechanical and microstructural performance of waste textile and cardboard materials in concrete","authors":"Robert Haigh, Malindu Sandanayake, Paul Joseph, Ehsan Yaghoubi, Zora Vrcelj","doi":"10.1002/suco.202301148","DOIUrl":"https://doi.org/10.1002/suco.202301148","url":null,"abstract":"Waste fiber reinforced concrete is gaining recognition as a high‐performance construction material, offering notable load‐bearing capacity, corrosion resistance, and enhanced durability features. As the building and construction industry focuses on sustainable practices, fibers derived from waste materials create an opportunity to be utilized further in composite designs. This study explores the tensile, compressive, and flexural behaviors of cardboard fibers (kraft fibers) and textile polyester fibers in concrete materials. The composite microstructure is also investigated using a scanning electron microscope (SEM) to measure the bonding performance of the fibers within the cementitious matrix. Four mix designs were created using 2.5% textile fibers as a reinforcement agent and 5% silica fume modified kraft fibers (SFKFs) as a partial cement replacement. The combination of fibers achieved 44 MPa compressive strength, equaling the control. Tensile strength was enhanced by 5% when using the combination of the two fibers, achieving 3.58 MPa in comparison to 3.41 MPa. However, flexural strength was reduced among all fibrous concrete materials. SEM images distinguished the natural and synthetic characteristics associated with the two fibers within the cementitious matrix. Namely, demonstrating the chemical bonding of SFKFs in comparison with the physical bonding properties of the textile fibers. This study serves as a valuable resource for future investigations and the broader adoption of binary waste fiber composite designs in cementitious composite applications.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"36 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141740609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With the increasing utilization of reinforced concrete (RC) beams in eco‐friendly and fast‐paced construction practices, evaluating their impact performance becomes imperative. These beams are susceptible to unforeseen impact loads resulting from accidents or terrorist incidents throughout their service lifespan. Five groups of RC beams, each subjected to different curing periods, stirrup reinforcement, and drop hammer heights, were fabricated. Among these groups, one underwent static load testing, while the remaining groups were subjected to impact load testing utilizing the drop hammer test system. The failure modes, static response, dynamic response, and energy dissipation of RC beams were analyzed. Static tests revealed that RC beams exhibited a flexure‐governed failure mode with top surface concrete crushing, aligning with expectations. With increased stirrup reinforcement ratios, shear and flexural‐shear cracks during impact tests decreased, with high impact loads causing diagonal shear failure, severe concrete crushing, additional diagonal shear cracks, and a broader crack distribution. Higher drop hammer heights were found to increase overall energy dissipation, whereas increased stirrup reinforcement ratios resulted in moderate decrease. Specifically, the overall energy dissipation increased with higher drop hammer heights. Conversely, an increase in the stirrup reinforcement ratio was linked to a certain degree of decrease in overall energy dissipation.
{"title":"Experimental study on the reinforced concrete beams with varied stirrup reinforcement ratio under static and impact loads","authors":"Jianxiao Gu, Liancheng Li, Xin Huang, Hui Chen","doi":"10.1002/suco.202400266","DOIUrl":"https://doi.org/10.1002/suco.202400266","url":null,"abstract":"With the increasing utilization of reinforced concrete (RC) beams in eco‐friendly and fast‐paced construction practices, evaluating their impact performance becomes imperative. These beams are susceptible to unforeseen impact loads resulting from accidents or terrorist incidents throughout their service lifespan. Five groups of RC beams, each subjected to different curing periods, stirrup reinforcement, and drop hammer heights, were fabricated. Among these groups, one underwent static load testing, while the remaining groups were subjected to impact load testing utilizing the drop hammer test system. The failure modes, static response, dynamic response, and energy dissipation of RC beams were analyzed. Static tests revealed that RC beams exhibited a flexure‐governed failure mode with top surface concrete crushing, aligning with expectations. With increased stirrup reinforcement ratios, shear and flexural‐shear cracks during impact tests decreased, with high impact loads causing diagonal shear failure, severe concrete crushing, additional diagonal shear cracks, and a broader crack distribution. Higher drop hammer heights were found to increase overall energy dissipation, whereas increased stirrup reinforcement ratios resulted in moderate decrease. Specifically, the overall energy dissipation increased with higher drop hammer heights. Conversely, an increase in the stirrup reinforcement ratio was linked to a certain degree of decrease in overall energy dissipation.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"69 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141740392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As a sustainable solution, employing recycled tire rubber aggregates in the production of concrete is of considerable interest. However, the applicability of rubberized concretes in construction is restricted due to their relatively low mechanical performance. Using rubberized concrete as a filling material in a steel tube provides a suitable solution for overcoming this issue and for using it effectively as a load‐bearing element. The objective of this study is to examine the impact of the material characteristics of the sustainable rubberized concrete‐filled steel tube (Ru‐CFST) and develop a design model based on ultimate strength prediction for the axially loaded Ru‐CFST stub columns with varying contents of tire rubber aggregate. The model was developed through the gene expression programming (GEP) technique by employing the experimental test results to determine the ultimate compressive strength of Ru‐CFST columns. Based on the principal component analysis, the sectional properties of the load‐bearing element (such as outer diameter, thickness, and length), material strengths (such as rubberized concrete and steel tube strengths), and rubber content were determined as statistically significant parameters affecting the ultimate axial strength of Ru‐CFST stub columns and thus, they were considered in the stage of the model generation. Furthermore, the proposed model's performance was compared to that of available models suggested for traditional CFST columns by commonly employed design codes, namely, ACI, AIJ, AISC, CSA, EC4, and GB. Based on the statistical analysis of the results, it can be concluded that the existing formulations have a relatively acceptable randomness and scatter of observations within the distribution, while the proposed design model gives a more accurate prediction for the ultimate bearing capacity of axially loaded Ru‐CFST columns with the highest R‐squared value of about 0.99 and the comparatively lowest mean absolute percent error of 7.54. It can be stated that the proposed GEP‐based design model will encourage engineers to use such sustainable structural members in their designs and constructions.
{"title":"Compressive behavior of sustainable rubberized concrete‐filled steel tube columns having various recycled tire rubber aggregate contents and developing a predictive design model","authors":"Esra Mete Güneyisi, Süleyman İpek, Erhan Güneyisi","doi":"10.1002/suco.202400111","DOIUrl":"https://doi.org/10.1002/suco.202400111","url":null,"abstract":"As a sustainable solution, employing recycled tire rubber aggregates in the production of concrete is of considerable interest. However, the applicability of rubberized concretes in construction is restricted due to their relatively low mechanical performance. Using rubberized concrete as a filling material in a steel tube provides a suitable solution for overcoming this issue and for using it effectively as a load‐bearing element. The objective of this study is to examine the impact of the material characteristics of the sustainable rubberized concrete‐filled steel tube (Ru‐CFST) and develop a design model based on ultimate strength prediction for the axially loaded Ru‐CFST stub columns with varying contents of tire rubber aggregate. The model was developed through the gene expression programming (GEP) technique by employing the experimental test results to determine the ultimate compressive strength of Ru‐CFST columns. Based on the principal component analysis, the sectional properties of the load‐bearing element (such as outer diameter, thickness, and length), material strengths (such as rubberized concrete and steel tube strengths), and rubber content were determined as statistically significant parameters affecting the ultimate axial strength of Ru‐CFST stub columns and thus, they were considered in the stage of the model generation. Furthermore, the proposed model's performance was compared to that of available models suggested for traditional CFST columns by commonly employed design codes, namely, ACI, AIJ, AISC, CSA, EC4, and GB. Based on the statistical analysis of the results, it can be concluded that the existing formulations have a relatively acceptable randomness and scatter of observations within the distribution, while the proposed design model gives a more accurate prediction for the ultimate bearing capacity of axially loaded Ru‐CFST columns with the highest R‐squared value of about 0.99 and the comparatively lowest mean absolute percent error of 7.54. It can be stated that the proposed GEP‐based design model will encourage engineers to use such sustainable structural members in their designs and constructions.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"92 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141740608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The alkali‐silica reaction (ASR) is one of the durability issues that affect the safety of concrete structures. Numerical simulation is useful for monitoring the internal condition of a reinforced concrete (RC) structure with ASR damage and predicting its long‐term behavior. Since discrete methods of simulation suit situations where concrete undergoes durability issues associated with expansion and cracking, a mesoscale discrete analysis method known as the three‐dimensional Rigid Body Spring Model (3D RBSM), as already used to simulate concrete ASR damage at the material scale, has been further developed to simulate ASR damage at the structural scale. In this development, the aggregate is not separately modeled and expansive elements are included to simulate ASR expansion, allowing a larger element size (1–2 cm). The number of elements and computation time are reduced to less than 1%. This proposed model is used to simulate ASR damage in a RC beam and the beam's residual flexural capacity. The simulation allows the internal stress and cracking condition to be visualized, leading to an explanation as to why the loading capacity of a RC beam is not affected by ASR damage: first, almost no cracks form at the core of the beam section due to the stirrup confinement, so the effective depth of the cross section is maintained after ASR damage; second, the tensile reinforcements have already yielded although ASR damage exists. Besides, the inhibited development of shear cracks may be one of the reasons for the slight improvement of flexural capacity of the damaged‐RC beam in experiment and simulation.
碱硅反应（ASR）是影响混凝土结构安全的耐久性问题之一。数值模拟有助于监测存在 ASR 损伤的钢筋混凝土（RC）结构的内部状况，并预测其长期行为。由于离散模拟方法适用于混凝土出现与膨胀和开裂相关的耐久性问题的情况，因此我们进一步开发了一种称为三维刚体弹簧模型（3D RBSM）的中尺度离散分析方法，该方法已用于模拟材料尺度上的混凝土 ASR 损伤，以模拟结构尺度上的 ASR 损伤。在这次开发中，骨料没有单独建模，而是加入了膨胀元素来模拟 ASR 的膨胀，从而允许更大的元素尺寸（1-2 厘米）。元素数量和计算时间减少到 1%以下。该建议模型用于模拟 RC 梁的 ASR 损伤和梁的残余抗弯能力。通过模拟可以直观地看到内部应力和开裂情况，从而解释了 RC 梁的承载能力不受 ASR 损伤影响的原因：首先，由于箍筋的约束作用，梁截面的核心部分几乎没有裂缝形成，因此 ASR 损伤后横截面的有效深度得以保持；其次，虽然存在 ASR 损伤，但受拉钢筋已经屈服。此外，剪切裂缝的发展受到抑制也可能是实验和模拟中受损 RC 梁的抗弯能力略有提高的原因之一。
{"title":"Investigating the flexural behavior of ASR‐damaged RC beam through internal stress and cracking development using 3D Rigid Body Spring Model","authors":"Jie Luo, Kohei Nagai","doi":"10.1002/suco.202400255","DOIUrl":"https://doi.org/10.1002/suco.202400255","url":null,"abstract":"The alkali‐silica reaction (ASR) is one of the durability issues that affect the safety of concrete structures. Numerical simulation is useful for monitoring the internal condition of a reinforced concrete (RC) structure with ASR damage and predicting its long‐term behavior. Since discrete methods of simulation suit situations where concrete undergoes durability issues associated with expansion and cracking, a mesoscale discrete analysis method known as the three‐dimensional Rigid Body Spring Model (3D RBSM), as already used to simulate concrete ASR damage at the material scale, has been further developed to simulate ASR damage at the structural scale. In this development, the aggregate is not separately modeled and expansive elements are included to simulate ASR expansion, allowing a larger element size (1–2 cm). The number of elements and computation time are reduced to less than 1%. This proposed model is used to simulate ASR damage in a RC beam and the beam's residual flexural capacity. The simulation allows the internal stress and cracking condition to be visualized, leading to an explanation as to why the loading capacity of a RC beam is not affected by ASR damage: first, almost no cracks form at the core of the beam section due to the stirrup confinement, so the effective depth of the cross section is maintained after ASR damage; second, the tensile reinforcements have already yielded although ASR damage exists. Besides, the inhibited development of shear cracks may be one of the reasons for the slight improvement of flexural capacity of the damaged‐RC beam in experiment and simulation.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"83 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141740611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Concrete sustainability and performance under extreme conditions are of growing interest in construction engineering. This study delves into the influence of recycled coarse aggregate (RCA) content and elevated temperatures on normal‐strength concrete containing RCA. Five different concrete compositions, featuring varying content of RCA (ranging from 0% to 100%), were examined. The heating and subsequent cooling followed the ISO‐834 temperature–time graph up to 800°C. The primary objective was to evaluate residual properties, including the stress–strain behavior, compressive and tensile strength, secant elastic modulus, peak strain, and bond strength of RCA concrete. The findings reveal a consistent decrease in both strength and stiffness parameters of RCA concrete with rising temperatures, while peak strain exhibits a rapid increase at elevated temperatures. Interestingly, RCA content had a negligible impact on the relative deterioration of high‐temperature exposed RCA concrete compared to that at ambient conditions. Moreover, the bond behavior closely resembled that of natural aggregate concrete when used in moderate proportions. Degradation models based on regression analysis of the data were used to quantify the bond strength reduction for RCA‐based concrete and the slip of rebar concerning various temperatures. Importantly, these models demonstrated consistency with those applicable to conventional concrete.
{"title":"Stress–strain characteristics of fire‐exposed recycled coarse aggregate concrete","authors":"Faraz Tariq, Hamza Hasan, Pradeep Bhargava","doi":"10.1002/suco.202301060","DOIUrl":"https://doi.org/10.1002/suco.202301060","url":null,"abstract":"Concrete sustainability and performance under extreme conditions are of growing interest in construction engineering. This study delves into the influence of recycled coarse aggregate (RCA) content and elevated temperatures on normal‐strength concrete containing RCA. Five different concrete compositions, featuring varying content of RCA (ranging from 0% to 100%), were examined. The heating and subsequent cooling followed the ISO‐834 temperature–time graph up to 800°C. The primary objective was to evaluate residual properties, including the stress–strain behavior, compressive and tensile strength, secant elastic modulus, peak strain, and bond strength of RCA concrete. The findings reveal a consistent decrease in both strength and stiffness parameters of RCA concrete with rising temperatures, while peak strain exhibits a rapid increase at elevated temperatures. Interestingly, RCA content had a negligible impact on the relative deterioration of high‐temperature exposed RCA concrete compared to that at ambient conditions. Moreover, the bond behavior closely resembled that of natural aggregate concrete when used in moderate proportions. Degradation models based on regression analysis of the data were used to quantify the bond strength reduction for RCA‐based concrete and the slip of rebar concerning various temperatures. Importantly, these models demonstrated consistency with those applicable to conventional concrete.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"70 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141608204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qing Jiang, Wenji Su, Yulong Feng, Jie Shen, Yonglong Fan, Dianchun Xuan
In this paper, seven half‐scale specimens are used to investigate the effects of the beam–column width ratio, concrete strength, and axial load on the seismic performance of wide exterior beam–column joints. The test results show that all the specimens undergo bending damage at the beam end. The concrete damage in the core column is not significant, meeting the seismic requirements of strong column–weak beams and strong joint–weak members. For specimens with small beam widths, the increase in axial load can effectively reduce the damage to the concrete in the outer joint and increase the strength of the specimen. Increasing the beam width and concrete strength reduces the ductility of the specimen while increasing the strength of the specimen. The bonding performance of the longitudinal bars anchored outside the core column is poor, as bond–slip with the concrete is observed during the test. In addition, compared with ACI 318‐19, GB 50011‐2010 is more conservative for calculating the shear strength of exterior wide beam–column joints. Finally, a corresponding finite element model is established by MSC Marc and verified based on the experimental results.
本文使用七个半比例试件研究了梁柱宽度比、混凝土强度和轴向荷载对宽外墙梁柱连接抗震性能的影响。试验结果表明，所有试件的梁端都出现了弯曲破坏。核心柱的混凝土破坏并不严重，满足强柱弱梁和强连接弱构件的抗震要求。对于梁宽较小的试件，增加轴向荷载可有效减少外接缝处混凝土的破坏，提高试件强度。增加梁宽和混凝土强度在提高试件强度的同时，也降低了试件的延性。锚固在核心柱外的纵向杆件的粘结性能较差，因为在试验过程中观察到与混凝土的粘结滑移。此外，与 ACI 318-19 相比，GB 50011-2010 在计算外部宽梁柱连接处的抗剪强度时更为保守。最后，通过 MSC Marc 建立了相应的有限元模型，并根据试验结果进行了验证。
{"title":"Seismic performance of RC exterior wide beam–column joints","authors":"Qing Jiang, Wenji Su, Yulong Feng, Jie Shen, Yonglong Fan, Dianchun Xuan","doi":"10.1002/suco.202300830","DOIUrl":"https://doi.org/10.1002/suco.202300830","url":null,"abstract":"In this paper, seven half‐scale specimens are used to investigate the effects of the beam–column width ratio, concrete strength, and axial load on the seismic performance of wide exterior beam–column joints. The test results show that all the specimens undergo bending damage at the beam end. The concrete damage in the core column is not significant, meeting the seismic requirements of strong column–weak beams and strong joint–weak members. For specimens with small beam widths, the increase in axial load can effectively reduce the damage to the concrete in the outer joint and increase the strength of the specimen. Increasing the beam width and concrete strength reduces the ductility of the specimen while increasing the strength of the specimen. The bonding performance of the longitudinal bars anchored outside the core column is poor, as bond–slip with the concrete is observed during the test. In addition, compared with ACI 318‐19, GB 50011‐2010 is more conservative for calculating the shear strength of exterior wide beam–column joints. Finally, a corresponding finite element model is established by MSC Marc and verified based on the experimental results.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"36 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141608205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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