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Mohammad Shekarchi - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on the bond strength between ultra high strength fiber reinforced Cementitious Mortar conventional concrete
Construction and Building Materials, 2019Co-Authors: Soheil Jafarinejad, Amirmahdi Rabiee, Mohammad ShekarchiAbstract:Abstract Nowadays, there is an increasing desire to use Ultra High Strength Fiber Reinforced Cementitious Mortar (UHSFRCM) in the rehabilitation of existing concrete structures. Although excellent mechanical improvements are reported in literature, the performance of the bond to provide a monolithic composite structure is still open to question. In this study, the bond has been investigated using three pull off, slant shear, and direct shear tests. The substrate surface of corresponding specimens had been prepared by sandblasting, grooving, wire brushing, and as-cast methods. Sandblasting indicates the best results, satisfying specified limits presented by ACI.
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Experimental investigation on the bond strength between Ultra high strength Fiber Reinforced Cementitious Mortar & conventional concrete
Construction and Building Materials, 2019Co-Authors: Soheil Jafarinejad, Amirmahdi Rabiee, Mohammad ShekarchiAbstract:Abstract Nowadays, there is an increasing desire to use Ultra High Strength Fiber Reinforced Cementitious Mortar (UHSFRCM) in the rehabilitation of existing concrete structures. Although excellent mechanical improvements are reported in literature, the performance of the bond to provide a monolithic composite structure is still open to question. In this study, the bond has been investigated using three pull off, slant shear, and direct shear tests. The substrate surface of corresponding specimens had been prepared by sandblasting, grooving, wire brushing, and as-cast methods. Sandblasting indicates the best results, satisfying specified limits presented by ACI.
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DURABILITY AND DIMENSIONAL STABILITY OF STEEL FIBER REINFORCED Cementitious Mortar IN COMPARISON TO HIGH PERFORMANCE CONCRETE
2016Co-Authors: Masoud Moradian, Mohammad ShekarchiAbstract:This paper presents a study on durability and dimensional stability of a Steel Fiber Reinforced Cementitious Mortar (SFRCM), and the results are compared with those of a common High Performance Concrete (HPC) mix. Common mechanical, durability, and dimensional stability properties of the hardened Mortars and concrete are investigated by testing water absorption, water penetration, resistance to elevated temperature, thermal expansion coefficient, and drying shrinkage. The results reveal superior mechanical and durability performance of SFRCM in comparison to those of the HPC. However, there were some concerns about the performance of SFRCM exposed to elevated temperatures because of the low porosity and permeation. In addition, the higher thermal expansion coefficient and different shrinkage behavior of SFRCM should be considered in the design of structural elements.
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Behavior of Steel Fiber-Reinforced Cementitious Mortar and High-Performance Concrete in Triaxial Loading
ACI Materials Journal, 2015Co-Authors: Afshin Noori, Mohammad Shekarchi, Masoud Moradian, MoosaviAbstract:A study on the behavior of a steel fiber-reinforced Cementitious Mortar (SFRCM) in a triaxial compression condition and a comparison of results with those of a common high-performance concrete (HPC) is presented. SFRCM with a high compressive strength seems to be a promising material in civil engineering applications. A series of cylindrical specimens of two types of SFRCM with 1% and 2% volume fraction of steel fiber and one type of HPC were prepared and tested under various confining pressures: 0, 5, 10, 15, and 20 MPa (0.72, 1.45, 2.18, and 2.90 ksi). In general, raising the confinement level increases the peak axial stress and the corresponding strain, while on the other hand this causes the specimens to behave more ductile. According to the results, the addition of steel fiber has meaningfully helped increase energy absorption capacity of the specimens. Finally, empirical equations were derived to predict the peak axial stress and the corresponding strain of the tested materials as a function of confining pressure for tested materials.
Kyoung-kyu Choi - One of the best experts on this subject based on the ideXlab platform.
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Direct shear behavior of Cementitious Mortar reinforced by carbon fiber textile
Construction and Building Materials, 2020Co-Authors: Ngoc Hieu Dinh, Hai Van Tran, Kyoung-kyu ChoiAbstract:Abstract This study experimentally investigated the characteristics of carbon fiber textile-reinforced Mortar (TRM) under direct shear. The main test parameters of this study include the fiber reinforcement ratio of carbon fiber textile, the surface treatment used between Mortar matrix and the fiber textile, and the inclination angle of the fiber filaments. Three fiber reinforcement ratio of carbon fiber textile of (0.17, 0.35, and 0.53) % in the Mortar matrix were investigated. Two different surface treatment methods were employed to improve the bond performance of carbon fiber textiles in the Mortar matrix: epoxy impregnation only, and sand coating after epoxy impregnation. Two inclination angles of fiber filaments of 0°/90° and –45°/45° were investigated. The test results showed that the textile reinforcement within Cementitious Mortar matrix affected the failure modes and the shear performance of test specimens in terms of cracking and ultimate shear stress, crack deformation, and residual shear stress in the pre- and post-peak stages. Moreover, a crack-shear slip model for Cementitious Mortar reinforced by carbon fiber textile was developed considering the material characteristics of the Mortar and the fiber textile, and its prediction showed good agreement with the experimental results.
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Effect of dispersed micro-fibers on tensile behavior of uncoated carbon textile-reinforced Cementitious Mortar after high-temperature exposure
Cement and Concrete Composites, 1Co-Authors: Ngoc Hieu Dinh, Sang Hyun Park, Kyoung-kyu ChoiAbstract:Abstract The mechanical and structural behavior of infrastructure and buildings under high-temperature environment is one of the major concerns in retrofit technologies. The present study aims to experimentally investigate the effectiveness of dispersed micro-fibers on the tensile behavior of uncoated carbon textile-reinforced Mortar (TRM) after exposure to high temperatures. The main experimental parameters include the micro-fiber type, fiber volume fraction, and high-temperature level. Micro-steel fibers and amorphous metallic fibers with lengths of 13 and 15 mm, respectively, were utilized in this study to ameliorate the Cementitious Mortar matrix with a volume fraction in the range of (0.4–0.8) %. Three investigated temperature levels were 25 °C (ambient condition), 200 °C, and 400 °C. The tensile tests were carried out based on RILEM TC 232-TDT after specimens cooled down to ambient temperature. The experimental results indicate that the inclusion of micro-steel and amorphous metallic fibers within the Mortar matrix significantly ameliorated the tensile characteristics of TRM specimens at both ambient and high temperatures. In addition, micro-amorphous metallic fibers exhibited significant advantages compared with steel fibers to improve the crack stress after exposure to 200 °C. Based on the experimental results and material characteristics, this study proposed an analytical model to predict the tensile strength after exposure to high temperatures and the idealized tensile stress-strain curves at the ambient temperature, of TRM composites incorporating dispersed micro-fibers, and the model prediction showed a good correlation with the experimental results.
Luciano Ombres - One of the best experts on this subject based on the ideXlab platform.
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Analysis of the bond between Fabric Reinforced Cementitious Mortar (FRCM) strengthening systems and concrete
Composites Part B-engineering, 2015Co-Authors: Luciano OmbresAbstract:Abstract The paper is devoted to the analysis, both experimental and theoretically, of the bond between a cement based fiber reinforced strengthening material and the concrete substrate. Results of tests on concrete specimens strengthened with the PBO-FRCM system, made by PBO (short of Polypara-phenilene-benzo-bisthiazole) fiber meshes embedded into a Cementitious Mortar (FRCM, Fabric Reinforced Cementitious Mortar), are presented and discussed. Tests were carried out varying both the bond length, the amount of the strengthening system and the service temperature. Obtained results furnish useful information (i) to determine the loss of bond between the PBO-FRCM system and the concrete, (ii) to define the failure modes and (iii) to evaluate both the influence of environmental conditions (service temperature) and mechanical and geometrical parameters on the loss of bond PBO-FRCM-to-concrete. Test results were, then, utilized to calibrate a local bond-slip relation. A comparison between experimental results and theoretical predictions of the bond-slip law PBO-FRCM-to-concrete is, finally, presented and discussed.
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concrete confinement with a cement based high strength composite material
Composite Structures, 2014Co-Authors: Luciano OmbresAbstract:Abstract The performances of plain concrete elements wrapped with PBO (short of Polypara-phenylene-benzo-bisthiazole) fiber meshes embedded into an inorganic stabilized Cementitious matrix (Fiber Reinforced Cementitious Mortar, FRCM) are analyzed, both theoretically and experimentally, in the paper. The aims of the paper are (i) to evaluate the effectiveness of the confinement of the concrete strengthened with the PBO-FRCM system, and, (ii) to define analytical relationships able to characterize the stress–strain response of the PBO-FRCM confined concrete. An experimental investigation, carried out on cylindrical specimens confined with the PBO-FRCM system, varying the fibers reinforcement ratio, the fibers orientation and the compressive concrete strength, is described. Results of tests are, then, utilized to compare experimental results against predictions both of some guidelines and theoretical models proposed for the analysis of confined concrete elements. Results of the comparison were presented and discussed in the paper. A simple semi-empirical model to predict axial peak strength and associated axial strain in PBO-FRCM confined concrete is also proposed.
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debonding analysis of reinforced concrete beams strengthened with fibre reinforced Cementitious Mortar
Engineering Fracture Mechanics, 2012Co-Authors: Luciano OmbresAbstract:Abstract The paper concerns with the debonding analysis of reinforced concrete beams strengthened by a fibre Reinforced Cementitious Mortar system made with fabric meshes of PBO (short of Polypara-phenylene-benzo-bisthiazole) fibres disposed along two orthogonal directions externally bonded to concrete surfaces with a cement based Mortar. Some PBO-FRCM strengthened reinforced concrete beams were tested varying the strengthening configuration. Experimental results were considered for a comparison with predictions of a non-linear numerical model developed for the debonding analysis of strengthened concrete structures. Obtained results give evidence of the influence of the PBO-FRCM configuration on the occurrence of debonding failure modes.
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flexural analysis of reinforced concrete beams strengthened with a cement based high strength composite material
Composite Structures, 2011Co-Authors: Luciano OmbresAbstract:Abstract The structural behaviour of reinforced concrete beams strengthened with a system made by fibre nets embedded into an inorganic stabilized Cementitious matrix named Fibre Reinforced Cementitious Mortars (FRCM), was investigated in this paper. The main issues focussed in the paper are: (i) the strengthening effect of the FRCM system on the flexural behaviour of reinforced concrete beams in terms of both ultimate capacity, deflections and ductility and (ii) the influence of the fibre reinforcement ratio on the occurrence of premature failure modes. The analysis refers to a FRCM system made by ultra-high strength fibre meshes such as the Polypara-phenylene-benzo-bisthiazole (PBO) fibres; PBO fibres have, in fact, great impact tolerance, energy absorption capacity superior than the other kind of fibres and chemical compatibility with the Cementitious Mortar. A total of 12 reinforced concrete beams strengthened in flexure with the PBO-FRCM system have been tested. The influence of some mechanical and geometrical parameters on the structural behaviour of strengthened beams, is analysed both at serviceability and the ultimate conditions. Results of a comparison between experimental results and theoretical predictions, obtained by models usually adopted for the analysis of FRP strengthened concrete structures, are, also, presented and discussed.
Soheil Jafarinejad - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on the bond strength between ultra high strength fiber reinforced Cementitious Mortar conventional concrete
Construction and Building Materials, 2019Co-Authors: Soheil Jafarinejad, Amirmahdi Rabiee, Mohammad ShekarchiAbstract:Abstract Nowadays, there is an increasing desire to use Ultra High Strength Fiber Reinforced Cementitious Mortar (UHSFRCM) in the rehabilitation of existing concrete structures. Although excellent mechanical improvements are reported in literature, the performance of the bond to provide a monolithic composite structure is still open to question. In this study, the bond has been investigated using three pull off, slant shear, and direct shear tests. The substrate surface of corresponding specimens had been prepared by sandblasting, grooving, wire brushing, and as-cast methods. Sandblasting indicates the best results, satisfying specified limits presented by ACI.
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Experimental investigation on the bond strength between Ultra high strength Fiber Reinforced Cementitious Mortar & conventional concrete
Construction and Building Materials, 2019Co-Authors: Soheil Jafarinejad, Amirmahdi Rabiee, Mohammad ShekarchiAbstract:Abstract Nowadays, there is an increasing desire to use Ultra High Strength Fiber Reinforced Cementitious Mortar (UHSFRCM) in the rehabilitation of existing concrete structures. Although excellent mechanical improvements are reported in literature, the performance of the bond to provide a monolithic composite structure is still open to question. In this study, the bond has been investigated using three pull off, slant shear, and direct shear tests. The substrate surface of corresponding specimens had been prepared by sandblasting, grooving, wire brushing, and as-cast methods. Sandblasting indicates the best results, satisfying specified limits presented by ACI.
Ngoc Hieu Dinh - One of the best experts on this subject based on the ideXlab platform.
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Direct shear behavior of Cementitious Mortar reinforced by carbon fiber textile
Construction and Building Materials, 2020Co-Authors: Ngoc Hieu Dinh, Hai Van Tran, Kyoung-kyu ChoiAbstract:Abstract This study experimentally investigated the characteristics of carbon fiber textile-reinforced Mortar (TRM) under direct shear. The main test parameters of this study include the fiber reinforcement ratio of carbon fiber textile, the surface treatment used between Mortar matrix and the fiber textile, and the inclination angle of the fiber filaments. Three fiber reinforcement ratio of carbon fiber textile of (0.17, 0.35, and 0.53) % in the Mortar matrix were investigated. Two different surface treatment methods were employed to improve the bond performance of carbon fiber textiles in the Mortar matrix: epoxy impregnation only, and sand coating after epoxy impregnation. Two inclination angles of fiber filaments of 0°/90° and –45°/45° were investigated. The test results showed that the textile reinforcement within Cementitious Mortar matrix affected the failure modes and the shear performance of test specimens in terms of cracking and ultimate shear stress, crack deformation, and residual shear stress in the pre- and post-peak stages. Moreover, a crack-shear slip model for Cementitious Mortar reinforced by carbon fiber textile was developed considering the material characteristics of the Mortar and the fiber textile, and its prediction showed good agreement with the experimental results.
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Effect of dispersed micro-fibers on tensile behavior of uncoated carbon textile-reinforced Cementitious Mortar after high-temperature exposure
Cement and Concrete Composites, 1Co-Authors: Ngoc Hieu Dinh, Sang Hyun Park, Kyoung-kyu ChoiAbstract:Abstract The mechanical and structural behavior of infrastructure and buildings under high-temperature environment is one of the major concerns in retrofit technologies. The present study aims to experimentally investigate the effectiveness of dispersed micro-fibers on the tensile behavior of uncoated carbon textile-reinforced Mortar (TRM) after exposure to high temperatures. The main experimental parameters include the micro-fiber type, fiber volume fraction, and high-temperature level. Micro-steel fibers and amorphous metallic fibers with lengths of 13 and 15 mm, respectively, were utilized in this study to ameliorate the Cementitious Mortar matrix with a volume fraction in the range of (0.4–0.8) %. Three investigated temperature levels were 25 °C (ambient condition), 200 °C, and 400 °C. The tensile tests were carried out based on RILEM TC 232-TDT after specimens cooled down to ambient temperature. The experimental results indicate that the inclusion of micro-steel and amorphous metallic fibers within the Mortar matrix significantly ameliorated the tensile characteristics of TRM specimens at both ambient and high temperatures. In addition, micro-amorphous metallic fibers exhibited significant advantages compared with steel fibers to improve the crack stress after exposure to 200 °C. Based on the experimental results and material characteristics, this study proposed an analytical model to predict the tensile strength after exposure to high temperatures and the idealized tensile stress-strain curves at the ambient temperature, of TRM composites incorporating dispersed micro-fibers, and the model prediction showed a good correlation with the experimental results.