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Saleem MA, Liaquat F, Saleem MM, Aziz M, Aslam F, Mohamed A. Development and characterization of non-proprietary ultra high performance concrete. Heliyon 2024; 10:e24260. [PMID: 38298661 PMCID: PMC10828644 DOI: 10.1016/j.heliyon.2024.e24260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 01/02/2024] [Accepted: 01/05/2024] [Indexed: 02/02/2024] Open
Abstract
This paper presents the developmental process of ultra-high performance concrete (UHPC), the most advanced form of concrete. The entire process exclusively utilized locally available materials. The mixes were prepared without using any specialized mixer or treatments, such as elevated pressure, etc. The primary objective of the research was to develop low-cost non-proprietary version of UHPC by optimizing both cementitious and non-cementitious materials to attain the highest levels of workability, compressive strength, flexural strength and durability. The research utilizes a trial-and-error approach, subjecting specimens to curing in both regular and heated water. The findings validate the viability of producing self-compacting UHPC with compressive strength ranging from 120 to 160 MPa, employing local materials and manufacturing methods. Raw materials and mixing sequence had a significant influence on the fresh and hardened properties of UHPC. The inclusion of steel fibers and the application of heat treatment remarkably enhanced the compressive strength. Furthermore, cost analysis revealed that this particular UHPC is only slightly over four times more expensive than conventional concrete, in contrast to commercially available UHPC, which is approximately 10 times expensive than traditional concrete.
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Affiliation(s)
- Muhammad Azhar Saleem
- Department of Civil Engineering, University of Engineering and Technology Lahore, Lahore, Pakistan
| | - Faizan Liaquat
- Department of Civil Engineering, University of Engineering and Technology Lahore, Lahore, Pakistan
| | - Muhammad Mazhar Saleem
- Department of Civil Engineering, University of Engineering and Technology Lahore, Lahore, Pakistan
| | - Mubashir Aziz
- Department of Civil and Environmental Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia
- Interdisciplinary Research Centre for Construction and Building Materials, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia
| | - Fahid Aslam
- Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam bin Abdulaziz University, Al Kharj, 11942, Saudi Arabia
| | - Abdullah Mohamed
- Abdullah Mohamed Research Centre, Future University in Egypt, New Cairo, 11835, Egypt
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Ullah R, Qiang Y, Ahmad J, Vatin NI, El-Shorbagy MA. Ultra-High-Performance Concrete (UHPC): A State-of-the-Art Review. MATERIALS 2022; 15:ma15124131. [PMID: 35744190 PMCID: PMC9228538 DOI: 10.3390/ma15124131] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/14/2022] [Accepted: 04/26/2022] [Indexed: 12/10/2022]
Abstract
The interest of researchers in UHPC has increased over the past decade. It is crucial to understand the structural behavior of reinforced UHPC (R/UHPC) components under various loading conditions before they can be used as a replacement for conventional concrete. Although several studies on ultra-high-performance concrete (UHPC) have been conducted, the knowledge is scattered, and no one can easily judge the performance and methodology of UPHC. Therefore, the purpose of this study was to review the research studies already carried out on UHPC. The review focuses on the materials’ physical and chemical composition, mechanical and durability characteristics, fire resistance, and environmental benefits of UHPC. Design considerations for effectively utilizing UHPC in structural elements are also presented. The best UHPFRC mixture is obtainable with a steel fiber content of 2–3% and a water-to-cement ratio of 0.2–0.3. The review also discusses the essentials recommendation for future research on UHPC.
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Affiliation(s)
- Rahat Ullah
- School of Civil Engineering, Central South University, Changsha 410075, China;
- National Engineering Research Center of High-Speed Railway Construction Technology, Changsha 410075, China
| | - Yuan Qiang
- School of Civil Engineering, Central South University, Changsha 410075, China;
- National Engineering Research Center of High-Speed Railway Construction Technology, Changsha 410075, China
- Correspondence: (Y.Q.); (J.A.)
| | - Jawad Ahmad
- Department of Civil Engineering, Swedish College of Engineering and Technology, Wah Cantt 47040, Pakistan
- Correspondence: (Y.Q.); (J.A.)
| | | | - Mohammed A. El-Shorbagy
- Department of Mathematics, College of Science and Humanities in Al-Kharj, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia;
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Shahid MA, Rashid MU, Ali N, Chaiyasarn K, Joyklad P, Hussain Q. Mechanical Experiments on Concrete with Hybrid Fiber Reinforcement for Structural Rehabilitation. MATERIALS 2022; 15:ma15082828. [PMID: 35454521 PMCID: PMC9032813 DOI: 10.3390/ma15082828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 04/01/2022] [Accepted: 04/07/2022] [Indexed: 11/16/2022]
Abstract
Reinforced concrete is used in the construction of bridges, buildings, retaining walls, roads, and other engineered structures. Due to seismic activities, a lot of structures develop seismic cracks. The rehabilitation of such structures is necessary for public safety. The overall aim of this research study was to produce a high-performance hybrid fiber-reinforced concrete (HPHFRC) with enhanced properties as compared to plain high-performance concrete and high-performance fiber-reinforced concrete (HPFRC) for the rehabilitation of bridges and buildings. Kevlar fibers (KF) and glass fibers (GF) with lengths of 35 mm and 25 mm, respectively, were added and hybridized to 1.5% by mass of cement to create hybrid fiber-reinforced concrete mixes. Eight mixes were cast in total. The compressive strength (f′c), flexural strength (fr), splitting tensile strength (fs), and other mechanical properties, i.e., energy absorption and toughness index values, were enhanced in HPHFRC as compared to CM and HPFRC. It was found that the concrete hybridized with 0.75% KF and 0.75% GF (HF-G 0.75 K 0.75) had the most enhanced overall mechanical properties, illustrating its potential to be utilized in the rehabilitation of bridges and structures.
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Affiliation(s)
- Muhammad Asharib Shahid
- Civil Engineering Department, University of Management and Technology, Lahore 54770, Pakistan; (M.A.S.); (M.U.R.); (N.A.)
| | - Muhammad Usman Rashid
- Civil Engineering Department, University of Management and Technology, Lahore 54770, Pakistan; (M.A.S.); (M.U.R.); (N.A.)
| | - Nazam Ali
- Civil Engineering Department, University of Management and Technology, Lahore 54770, Pakistan; (M.A.S.); (M.U.R.); (N.A.)
| | - Krisada Chaiyasarn
- Thammasat Research Unit in Infrastructure Inspection and Monitoring, Repair and Strengthening (IIMRS), Thammasat School of Engineering, Faculty of Engineering, Thammasat University Rangsit, Pathum Thani 12000, Thailand;
| | - Panuwat Joyklad
- Department of Civil and Environmental Engineering, Faculty of Engineering, Srinakharinwirot University, Nakhonnayok 26120, Thailand
- Correspondence:
| | - Qudeer Hussain
- Center of Excellence in Earthquake Engineering and Vibration, Department of Civil Engineering, Chulalongkorn University, Bangkok 10330, Thailand;
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Evaluation of Compressive Strength of Ultra-High-Performance Fiber-Reinforced Concrete Using Non-Destructive Tests. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2022. [DOI: 10.1007/s13369-021-06448-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Han J, Xi Z, Yu R, Guan J, Lv Y, Li G. Preparation and Comprehensive Properties of a High-Radiation-Shielding UHPC by Using Magnetite Fine Aggregate. MATERIALS 2022; 15:ma15030978. [PMID: 35160924 PMCID: PMC8838137 DOI: 10.3390/ma15030978] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/09/2022] [Accepted: 01/18/2022] [Indexed: 02/04/2023]
Abstract
Nuclear technology benefits humans, but it also produces nuclear radiation that harms human health and the environment. Based on the modified Andreasen and Andersen particle packing model for achieving a densely compacted cementitious matrix, a new magnetite ultra-high-performance concrete (MUHPC) was designed using magnetite fine aggregate as a substitute for river sands with 0%, 20%, 40%, 60%, 80%, and 100% replacement ratios. The comprehensive properties of the developed MUHPC were tested and evaluated. These properties were fluidity, static and dynamic compressive strengths, high-temperature performance, antiradiation behaviors, hydration products, and micropore structures. Experimental results indicate that the developed MUHPC has high work performance and static and dynamic mechanical properties. The gamma ray shielding performance of MUHPC substantially improves with increased magnetite fine aggregate. Corresponding with 100% magnetite fine aggregate substitution, the linear attenuation coefficient of MUHPC is enhanced by 56.8% compared with that of ordinary concrete. Magnetite addition does not change the type of cement hydration products but improves the micropore structures of MUHPC and effectively reduces its total porosity and average pore diameter, thereby contributing to its mechanical and radiation shielding properties. The compressive strength and linear attenuation coefficient of the MUHPC can reach 150 MPa and 0.2 cm−1, respectively. In addition, the MUHPC also exhibits superior mechanical and radiation shielding performance at elevated temperatures (<400 °C). Finally, high strength and antiradiation performance support the use of MUHPC in radiation protection materials in the future.
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Affiliation(s)
- Jianjun Han
- School of Civil Engineering, Henan University of Technology, Zhengzhou 450001, China; (J.H.); (Z.X.)
| | - Zhuangmin Xi
- School of Civil Engineering, Henan University of Technology, Zhengzhou 450001, China; (J.H.); (Z.X.)
| | - Rui Yu
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China;
| | - Junfeng Guan
- School of Architecture, North China University of Water Resources and Electric Power, Zhengzhou 450045, China;
| | - Yajun Lv
- School of Architecture, North China University of Water Resources and Electric Power, Zhengzhou 450045, China;
- Structural Research Institute, China Institute of Water Resources and Hydropower, Beijing 100038, China
- Correspondence: (Y.L.); (G.L.)
| | - Guo Li
- School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, China
- Correspondence: (Y.L.); (G.L.)
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Chen HJ, Chen CC, Lin HS, Lin SK, Tang CW. Flexural Behavior of Ultra-High-Performance Fiber-Reinforced Concrete Beams after Exposure to High Temperatures. MATERIALS 2021; 14:ma14185400. [PMID: 34576623 PMCID: PMC8471932 DOI: 10.3390/ma14185400] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 11/16/2022]
Abstract
Due to the dense structure of ultra-high-performance concrete (UHPC), it is prone to explosive spalling at high temperatures. In this paper, flexural testing of UHPC and high-strength concrete (HSC) beams was carried out at room temperature and after being subjected to different levels of thermal exposure (300-500 °C). The cross-section of the beam specimen was 150 (width) × 200 (depth) mm, and its length was 1500 mm. The flexural and shear design of the beam specimens were carried out in accordance with the ACI 318M-14 code. All of the beams were singly reinforced with two #4 rebars (minimum reinforcement ratio) as a longitudinal tensile reinforcement at the bottom of the specimen and at an effective depth of 165 mm. The flexural load was applied using the three-point load method. The results show that, at room temperature and after being subjected to different thermal exposures, compared with the HSC specimens, the stiffness of the UHPC specimens in the post-cracking stage was relatively larger and the deflection under a given load was smaller. Moreover, whether at room temperature or after exposure to different thermal exposures, the ductility of the UHPC specimens was better than that of the HSC specimens.
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Affiliation(s)
- How-Ji Chen
- Department of Civil Engineering, National Chung-Hsing University, No. 250, Kuo Kuang Rd., Taichung 40227, Taiwan; (H.-J.C.); (C.-C.C.); (H.-S.L.); (S.-K.L.)
| | - Chien-Chuan Chen
- Department of Civil Engineering, National Chung-Hsing University, No. 250, Kuo Kuang Rd., Taichung 40227, Taiwan; (H.-J.C.); (C.-C.C.); (H.-S.L.); (S.-K.L.)
| | - Hung-Shan Lin
- Department of Civil Engineering, National Chung-Hsing University, No. 250, Kuo Kuang Rd., Taichung 40227, Taiwan; (H.-J.C.); (C.-C.C.); (H.-S.L.); (S.-K.L.)
| | - Shu-Ken Lin
- Department of Civil Engineering, National Chung-Hsing University, No. 250, Kuo Kuang Rd., Taichung 40227, Taiwan; (H.-J.C.); (C.-C.C.); (H.-S.L.); (S.-K.L.)
| | - Chao-Wei Tang
- Department of Civil Engineering and Geomatics, Cheng Shiu University, No. 840, Chengching Rd., Niaosong District, Kaohsiung 83347, Taiwan
- Center for Environmental Toxin and Emerging-Contaminant Research, Cheng Shiu University, No. 840, Chengching Rd., Niaosong District, Kaohsiung 83347, Taiwan
- Super Micro Mass Research and Technology Center, Cheng Shiu University, No. 840, Chengching Rd., Niaosong District, Kaohsiung 83347, Taiwan
- Correspondence: ; Tel.: +886-7-735-8800
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Kalthoff M, Raupach M, Matschei T. Influence of High Temperature Curing and Surface Humidity on the Tensile Strength of UHPC. MATERIALS 2021; 14:ma14154260. [PMID: 34361453 PMCID: PMC8347523 DOI: 10.3390/ma14154260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/23/2021] [Accepted: 07/26/2021] [Indexed: 01/01/2023]
Abstract
The objective of this study is an investigation of the different parameters that influence the tensile strength of ultra-high performance concrete (UHPC). Apart from the shrinkage and stiffness, the tensile strength is an important parameter for the design of crack-free concrete elements, e.g., in machine tool construction. One focus of our work is the influence of concrete curing and the great impact of the mechanical and physical characteristics of hydrated UHPC. For this reason, different curing regimes were investigated. The results show that even after heat treatment or autoclaving, the centric tensile strength of UHPC specimens is strongly influenced by the surrounding ambient humidity. Test specimens that were stored under water after a heat treatment or autoclaving and were still wet during the test had the highest tensile strengths. Storage at 20 °C and 65% relative humidity (rH), however, results in a 25% reduction in tensile strength. Alternating storage between water storage at 20 °C water and storage at 65% rH can also reduce the tensile strength dramatically by up to 70%. In particular, samples that were stored at 65% rH right before testing had very low tensile strengths. Surprisingly, the initially low tensile strength of previously dry stored UHPC can be restored by subsequent water storage. In the absence of any microstructural defects, e.g., microcracks, a possible explanation for this phenomenon can be the stress differences due to a humidity gradient between the core and surfaces and shrinkage combined with a continued reaction of the unhydrated binders of the UHPC.
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Insight into the Mechanical Performance of the UHPC Repaired Cementitious Composite System after Exposure to High Temperatures. MATERIALS 2021; 14:ma14154095. [PMID: 34361287 PMCID: PMC8347582 DOI: 10.3390/ma14154095] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 07/17/2021] [Accepted: 07/20/2021] [Indexed: 11/16/2022]
Abstract
In this paper, the mechanical performance of an ultra-high-performance concrete (UHPC) repaired cementitious composite system, including the old matrix and the new reinforcement (UHPC), under various high temperature levels (20 °C, 100 °C, 300 °C, and 500 °C) was studied. In this system, UHPC reinforced with different contents of steel fibers and polypropylene (PP) fibers was utilized. Moreover, the physical, compressive, bonding, and flexural behaviors of the UHPC repaired system after being exposed to different high temperatures were investigated. Meanwhile, X-ray diffraction (XRD), baseline evaluation test (BET), and scanning electron microscope (SEM) tests were conducted to analyze the effect of high temperature on the microstructural changes in a UHPC repaired cementitious composite system. Results indicate that the appearance of the bonded system changed, and its mass decreased slightly. The average percentage of residual mass of the system was 99.5%, 96%, and 94–95% at 100 °C, 300 °C, and 500 °C, respectively. The residual compressive strength, bonding strength, and flexural performance improved first and then deteriorated with the increase of temperature. When the temperature reached 500 °C, the compressive strength, bonding strength, and flexural strength decreased by about 20%, 30%, and 15% for the UHPC bonded system, respectively. Under high temperature, the original components of UHPC decreased and the pore structure deteriorated. The cumulative pore volume at 500 °C could reach more than three times that at room temperature (about 20 °C). The bonding showed obvious deterioration, and the interfacial structure became looser after exposure to high temperature.
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Research on Cracking Mechanism of Early-Age Restrained Concrete under High-Temperature and Low-Humidity Environment. MATERIALS 2021; 14:ma14154084. [PMID: 34361280 PMCID: PMC8347269 DOI: 10.3390/ma14154084] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 07/17/2021] [Accepted: 07/20/2021] [Indexed: 11/17/2022]
Abstract
How to prevent the cracking of tunnel lining concrete under a high-temperature and low-humidity environment has gradually become a challenge faced by the engineering community. Actually, the concrete structure will be restrained, which easily leads to cracking. Aiming at this problem, a self-restraint device of concrete specimens was designed in this paper, which aims to more realistically simulate the restrained state of concrete structures during construction. SEM, EDS and XRD detection methods were used to study the macroscopic and microscopic properties of an early-age restrained concrete specimen under a high-temperature and low-humidity environment, and the results were compared with those of a non-restrained concrete specimen. The results show that the change in the internal relative humidity of the concrete was an extremely slow process, and the response rate of the internal humidity of the concrete was much slower than that of the temperature. A cubic curve model was used to fit the measured concrete damage degree with the loading age, and the fitting effect was good. Under the environment of high temperature and low humidity, the loading age from the 0.6th day to the 1st day was the period of a relatively large fluctuation in the concrete temperature and humidity, and the restraint would aggravate the damage of the concrete. The damage degree increased with the increase in the loading age, the microcracks gradually increased and, finally, macrocracks were formed. The restraint effect was to intensify the formation of microcracks, affect the hydration of the cement at the micro level and, finally, increase the risk of concrete cracking perpendicular to the restrained direction at the macro level. The research results may provide guidance for research on the cracking mechanism of tunnel lining concrete constructed under a high-temperature and low-humidity environment.
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10
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Fire Resistance and Elevated Temperature in Reinforced Concrete Members: Research Needs for India. ACTA ACUST UNITED AC 2021. [DOI: 10.1007/s40030-021-00513-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Seismic Resistant Bridge Columns with NiTi Shape Memory Alloy and Ultra-High-Performance Concrete. INFRASTRUCTURES 2020. [DOI: 10.3390/infrastructures5120105] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Reinforced concrete bridge columns often endure significant damages during earthquakes due to the inherent deficiencies of conventional materials. Superior properties of the new materials such as shape memory alloy (SMA) and ultra-high-performance concrete (UHPC), compared to the reinforcing steel and the normal concrete, respectively, are needed to build a new generation of seismic resistant columns. Application of SMA or UHPC in columns has been separately studied, but this paper aims to combine the superelastic behavior of NiTi SMA and the high strength of UHPC, in order to produce a column design with minimum permanent deformation and high load tolerance subjected to strong ground motions. Additionally, the excellent corrosion resistance of NiTi SMA and the dense and impermeable microstructure of UHPC ensure the long-term durability of the proposed earthquake resistant column design. The seismic performance of four columns, defined as steel reinforced concrete (S-C), SMA reinforced concrete (SMA-C), SMA reinforced UHPC (SMA-UHPC), and reduced SMA reinforced UHPC (R-SMA-UHPC) is analyzed through a loading protocol with up to 4% drift cycles. The use of NiTi SMA bars for the SMA reinforced columns is limited to the plastic hinge region where permanent deformations happen. All the columns have 2.0% reinforcement ratio, except the R-SMA-UHPC column that has a 1.33% reinforcement ratio to optimize the use of SMA bars. Unlike the S-C column that showed up to 68% residual deformation compared to peak displacement during the last loading cycle the SMA reinforced columns did not experience permanent deformation. The SMA-C and R-SMA-UHPC columns showed similar strengths to the S-C column, but with about 5.0- and 6.5-times larger ductility, respectively. The SMA-UHPC column showed 30% higher strength and 7.5 times larger ductility compared to the S-C column.
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Numerical Modeling and Analysis of Concrete Slabs in Interaction with Subsoil. SUSTAINABILITY 2020. [DOI: 10.3390/su12239868] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This article focuses on the analysis and numerical modeling of a concrete slab interacting with subsoil. This is a complex task for which a number of factors enter into the calculation, including the scope or dimension of the model, the non-linear solution approach, the choice of input parameters, and so forth. The aim of this article is to present one possible approach, which is based on a non-linear analysis and a three-dimensional computational model. Five slabs were chosen for modeling and analysis. The experiments involved slabs of 2000 × 2000 mm and a thickness of 150 mm, which were tested using specialized equipment. The slabs included a reinforced concrete slab, a standard concrete slab, and three fiber-reinforced concrete slabs. The fiber-reinforced slabs had fiber volume fractions of 0.32%, 0.64%, and 0.96%, which corresponded to fiber dosages of 25, 50, and 75 kg/m3. A reinforced concrete slab was chosen for the calibration model and the initial parametric study. The numerical modeling itself was based on a detailed evaluation of experiments, tests, and recommendations. The finite element method was used to solve the three-dimensional numerical model, where the fracture-plastic material of the model was used for concrete and fiber-reinforced concrete. In this paper, the performed numerical analyses are compared and evaluated, and recommendations are made for solving this problem.
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Siwiński J, Szcześniak A, Stolarski A. Modified Formula for Designing Ultra-High-Performance Concrete with Experimental Verification. MATERIALS 2020; 13:ma13204518. [PMID: 33053869 PMCID: PMC7599911 DOI: 10.3390/ma13204518] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/02/2020] [Accepted: 10/10/2020] [Indexed: 11/24/2022]
Abstract
The main purpose of the study was to propose a modification of Larrard’s formula for both the design and compressive-strength evaluation of ultra-high-performance concrete. The proposed modification consisted of the introduction of new parameters into the original formula that allowed it to consider the amount of binders and fine-grained aggregates, the amount of reinforcing fibers, the specimen shape and size, the curing time, and a reinterpretation of the water/cement ratio. The proposed modification was verified based on comparative analysis with the results of our own experimental studies and results taken from the literature. A very good convergence of these results was demonstrated, indicating the validity of the proposed modification.
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Sucharda O. Identification of Fracture Mechanic Properties of Concrete and Analysis of Shear Capacity of Reinforced Concrete Beams without Transverse Reinforcement. MATERIALS (BASEL, SWITZERLAND) 2020; 13:E2788. [PMID: 32575726 PMCID: PMC7344630 DOI: 10.3390/ma13122788] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 04/29/2020] [Accepted: 05/25/2020] [Indexed: 12/19/2022]
Abstract
The study of new and innovative quasi-brittle materials offers new possibilities for use in construction, but detailed knowledge of their behavior and mechanical properties is required. The use of new materials in the design solution of a structure is usually associated with numerical methods, which has a number of both advantages and disadvantages. Sophisticated numerical methods, without a sufficiently detailed input knowledge, can provide highly variable results with little informative value. The main goal of this article is to present the procedure for the identification of fracture mechanical parameters for a specific concrete with the use of developed inverse analysis combining multi-criteria decision analysis, stochastic modelling and nonlinear analysis. Subsequently, the identified mechanical parameters of concrete are used for the parametric study of shear resistance of structural beams without shear reinforcement, as an alternative or generalized approach to the study of damage to concrete and concrete structures. This research includes an experimental program using 24 reinforced concrete beams and a detailed determination of basic and specific mechanical properties during laboratory tests. The process of inverse analysis is illustrated in detail for the solved task. The use of nonlinear analysis for detailed failure modelling is based on a 3D computational model and a fracture plastic material model for concrete. Finally, the results of the experimental program and numerical modelling are discussed, leading to a number of conclusions.
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Affiliation(s)
- Oldrich Sucharda
- Department of Building Materials and Diagnostics of Structures, Faculty of Civil Engineering, VSB-Technical University of Ostrava, Ludvíka Podéště 1875/17, 708 00 Ostrava-Poruba, Czech Republic
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15
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Residual Mechanical Properties of Fiber-Reinforced Lightweight Aggregate Concrete after Exposure to Elevated Temperatures. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10103519] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this study, the effects of individual and mixed fiber on the mechanical properties of lightweight aggregate concrete (LWC) after exposure to elevated temperatures were examined. Concrete specimens were divided into a control group (ordinary LWC) and an experimental group (fiber-reinforced LWC), and their compressive strength, elastic modulus, and flexural strength after heating to high temperatures of 400–800 °C were investigated. The four test parameters included concrete type, concrete strength, fiber type, and targeted temperature. The test results show that after exposure to 400–800 °C, the variation in mechanical properties of each group of LWC showed a trend of increasing first and then decreasing. After exposure to 400 °C, the residual mechanical properties of all specimens did not attenuate due to the drying effect of the high temperature and the more sufficient cement hydration reaction. However, after exposure to 800 °C, the residual mechanical properties significantly reduced. Overall, the mixed fiber-reinforced LWC showed a better ability to resist the loss of mechanical properties caused by high temperature. Compared with the loss of compressive strength, the flexural strength was relatively lost.
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