Study on the effects of bonded stress between concrete and corroded rebar

Study on the effects of bonded stress between concrete and corroded rebar Study on the effects of bonded stress between concrete and corroded rebar Study on the effects of bonded stress between concrete and corroded rebar

CONTENTS CHAPTER GENERAL INTRODUCTION 1.1 INTRODUCTIONS 1.2 LITERATURE REVIEW 1.2.1 Foreign researches 1.2.2 Domestic researches 11 1.3 RESEARCH OBJECTIVES 16 1.4 RESEARCH CONTENT 16 1.5 APPROACH, RESEARCH METHOD 17 1.6 RESEARCH NOVELTY 18 CHAPTER 19 THEORETICAL BASIS OF THE STUDY 19 2.1 CORROSION PROCESS OF REINFORCEMENT IN CONCRETE 19 2.1.1 Environmental Severity Factors Influencing Corrosion 20 2.1.2 Identifying And Recognizing Common Forms Of Corrosion 21 2.1.3 Electrochemical cell and corrosion in concrete 23 2.1.4 Theoretical and practical corrosion levels 27 2.2 BOND STRESS OF CONCRETE AND REINFORCEMENT 28 2.2.1 Bonding between concrete and reinforcement 29 Non corroded: 29 2.2.2 Factors that contribute to bonded – stress 29 2.2.3 Factors affecting bonded – stress 30 2.2.4 Determine bonded – stress 30 2.2.5 The purpose of the experiment is to determine the properties of concrete and reinforcement when it is corroded 32 vi 2.3 SIMULATE THE PULL OUT EXPERIMENT BY THE FINITE ELEMENT METHOD 33 2.3.1 Research purpose and object 33 2.3.2 Introduction to ANSYS software 34 2.3.4 Finite element simulation 34 2.3.5 Modeling geometry and meshing 38 2.3.6 Material declaration 38 CHAPTER 40 PROCESS AND EVALUATION OF EXPERIMENTAL RESULTS 40 3.1 MATERIALS 40 3.1.1 Cement 40 3.1.2 Large aggregate 40 3.1.3 Small aggregate 42 3.1.4 Water 43 3.1.5 Steel bars 43 3.1.6 Electrolyte solution 44 3.2 SAMPLE MANUFACTURING 44 3.2.2 Number of specimens tested 45 3.3 EXPERIMENTAL METHOD 46 3.3.3 Electrolymification corrosion time calculation 48 3.4 CONCRETE MIX DESIGN 49 3.5 THE EXPERIMENT TO DETERMINE BOND STRESS OF REINFORCEMENT TO CONCRETE WHEN CORRODED 54 3.5.1 Experimental sequence 54 3.5.2 Results and discussion 55 3.5.2.1 Results of bond strength with further corroded specimens .56 3.5.2.2 Crack opening after artificial corrosion 59 3.5.2.3 Bond stress-slip relationships .63 vii 3.6 THE EXPERIMENT TO EVALUATE THE CHARACTERISTICS AND TENSILE STRENGTH OF REINFORCEMENT WHEN BEING CORRODED 68 3.6.1 Type Corrosive 68 3.6.2 Corrosion level 69 3.6.2.1 Coefficient of corrosion grade rating is based on d and r 69 3.6.2.2 Coefficient of corrosion mass rating is based on w 74 3.6.3 Bearing capacity of reinforcement when corrosive 80 CHAPTER 83 SIMULATE ANALYSIS OF EXPERIMENT RESULTS BY ANSYS 83 4.1 SIMULATION OF TENSILE TEST 83 4.1.1 FE bond-slip model using Cohesive Zone Model (CZM) 83 4.1.2 Modeling of concrete 84 4.1.2.1 Concrete element .84 4.1.2.2 Material model 84 4.1.3 Reinforcing bar model 88 4.1.3.1 Reinforcing bar element .88 4.1.3.2 Material model 88 4.1.4 Cohesive Zone Model (CZM) 89 4.1.4.1 Deriving Basic FEM Equations .89 4.1.4.2 Discretisation of the Variational Statements of the Interface 91 4.1.4.3 Deriving the Cohesive Element Stiffness Matrix 92 4.1.5 ANSYS model 93 4.1.5.1 Boundary condition 93 4.1.5.2 Preliminary results .95 4.2 SIMULATION RESULTS 97 4.2.1 Results of simulation of the Stress – Strain relationship of M1 group specimens 97 viii 4.2.2 Results of simulation of the Stress – Strain relationship of M2 group specimens 99 4.2.3 Results of simulation of the Stress – Strain relationship of M3 group specimens 101 4.2.4 Results of simulation of bond stress when corroded and ultra – high perfomance concrete (UHPC) 103 CHAPTER 105 CONCLUSION AND FUTURE PLAN 105 5.1 CONCLUSIONS 105 5.2 FUTURE PLAN .106 REFERENCES 107 ix LIST OF ABBREVIATIONS Abbreviations English meaning RC Reinforced concrete GPC Geopolymer concrete TCVN Vietnam Standards TCN Construction industry standards FEM Finite Element Method AI Artificial intelligence CFRP Carbon fiber reinforced polymer ANSYS FEM Software x LIST OF FIGURES Fig 1 Current status of reinforcement corrosion on some real projects [4] Fig The bond sections displaying the reduction in observed cross section [6] Fig Relationship between bond stress and displacement in the experiment [6] Fig Specimens test details; (a) Ø 12mm, ld= 60 mm; (b) Ø 12mm, ld = 167 mm; (c) Ø 20mm, ld = 100 mm [7] .5 Fig Comparison of the corroded and non-corroded tensile bars [14] .7 Fig Compare the strength of steel when corroded by experiment simulation [14] .8 Fig Experimental model [15] Fig Postrepair Performance of Specimens in Accelerated Corrosion Conditions: (a) Radial Expansion Strains versus Time; (b) Estimated Cumulative Steel Loss versus Time [26] .11 Fig Diagnosing analysis results for the RC beam in CBS program [31] 12 Fig 10 The relationship between load and mid-point displacement of beam [31] .12 Fig 11 Types of destructive samples [34] 13 Fig 12 The ABAQUS model [34] 13 Fig 13 Model of bond - bonding elements in reinforcement and concrete in simulation ABAQUS [35] 14 Fig 14 Value of plastic deformation of concrete and distribution of tensile stress in simulation [35] .14 Fig 15 Diagram of determining the relationship of the reinforcement bond force with the compressive strength of the concrete block [36] 15 Fig 16 Research program 18 Fig Cracking development and spalling of concrete cover due to oxidation of steel reinforcement [40] .20 Fig 2 Common Depictions of Corrosion [44] .21 xi Fig Additional images of corrosion forms [44] 23 Fig Basic Corrosion Cell 24 Fig Process Carbonation corrosive in reinforced concrete [45] 24 Fig Ion intrusion Cl − [45] 25 Fig Model bond – stress and slip displacement relationship of rebar used CEBFIP MC2010 [51] .31 Fig Relationship of bond stress and slip displacement steel bar [52] .32 Fig Stress-deformation relationship of reinforcement and concrete [55] 35 Fig 10 The destructive side of concrete follows Willam and Warnke model [56]35 Fig 11 SOLID65 Geometry 37 Fig 12 Model of steel material .38 Fig 13 LINK180 Geometry 38 Fig 14 Experimental model in ANSYS software 38 Fig 15 Destructive patterns of concrete 39 Fig 16 Equivalent stress distribution .39 Fig Cement is used in experiment [57] .40 Fig Material: sand, crushed stone after sieving based on ASTM C136-01 [58] .41 Fig 3 Graph of grain distribution of coarse aggregate 41 Fig Graph of grain distribution of fine aggregate .42 Fig Steel used in the experiment 43 Fig Geometry of pull-out test specimen 44 Fig Diagram illustrating electrode corrosion acceleration experiment 46 Fig Use DC power supply to electrolysis speed up corrosion 46 Fig Experiment process for reinforced concrete structure 48 Fig 10 Sample compression test 50 Fig 11 Prepare experimental concrete casting with different steel bars 51 Fig 12 Manufacturing experimental samples 52 xii Fig 13 Experimental samples 52 Fig 14 : Test Samples when corrosive with salt electrolyses NaCl 3,5% 53 Fig 15 Layout of test samples on tractors and support device 54 Fig 16 Data Logger TDS630 digital measurement .55 Fig 17 Bond stress relationship model - steel shear displacement CEB-FIP MC2020 [51] 56 Fig 18 Photograph of steel bar after artificial corrosion and pull-out test 56 Fig 19 (a) Photograph of steel bar after artificial corrosion and pull-out test; 59 Fig 20 Corrosion-induced cracks of reinforcement D12 60 Fig 21 Corrosion-induced cracks of reinforcement D16 61 Fig 22 Corrosion-induced cracks of reinforcement D20 62 Fig 23 Relation of bond stress - sliping displacement with reinforcement D12 64 Fig 24 Relation of bond stress - sliping displacement with reinforcement D16 65 Fig 25 Relation of bond stress - sliping displacement with reinforcement D20 66 Fig 26 Shape of reinforcement when corroded over time .68 Fig 27 Electrochemical corrosion products of reinforcing bars 69 Fig 28 a) steel bar has been cleaned rust; b) Measure the diameter of reinforcing steel that is corroded 69 Fig 29 The figure depicts the parameters of the corroded reinforcement hole 70 Fig 30 Cross section of the reinforcement section linked to the concrete 70 Fig 31 Calculations d max .70 Fig 32 Relationship between steel bar diameter and bond stress 72 Fig 33 The steel bar section is electronically balanced 74 Fig 34 The law of current variation in reinforcing bars .77 Fig 35 Normalised bond stress versus corresponding corrosion level for different concrete types 78 Fig 36 Tensile test of corroded reinforcing bar 80 Fig SOLID65 Element model 84 xiii Fig 3-D failure surface in principal stress space .85 Fig LINK180 Element model 88 Fig 4 Cohesive zone model to model interface behavior between rebar and concrete [67] 89 Fig Boundary condition .94 Fig Load condition 94 Fig UY displacement 95 Fig Third principal stress 95 Fig Equivalent stress 96 Fig 10 Equivalent strain .96 Fig 11 The Bond stress – Slip relationship between Experiment and FEM Modeling of M11 group specimens 97 Fig 12 The Bond stress – Slip relationship between Experiment and FEM Modeling of M12 group specimens 97 Fig 13 The Bond stress – Slip relationship between Experiment and FEM Modeling of M13 specimen 98 Fig 14 The Bond stress – Slip relationship between Experiment and FEM Modeling of M21 specimen 99 Fig 15 The Bond stress – Slip relationship between Experiment and FEM Modeling of M22 specimen 99 Fig 16 The Bond stress – Slip relationship between Experiment and FEM Modeling of M23 specimen 100 Fig 17 The Bond stress – Slip relationship between Experiment and FEM Modeling of M31 specimen 101 Fig 18 The Bond stress – Slip relationship between Experiment and FEM Modeling of M32 specimen 101 Fig 19 The Bond stress – Slip relationship between Experiment and FEM Modeling of M33 specimen 102 xiv Fig 20 Cementitious matrix (a), steel fibers reinforcement (b) and mixing procedure (c) of UHPC 103 Fig 21 The Bond stress – Slip relationship between Experiment and FEM Modeling of M11 specimen with UHPC concrete 104 xv 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 ... corrosion rate, and then significantly decreased as the corrosion time further increased, similar to that of conventional concrete However, the rate of bond degradation between RCA concrete and corroded. .. strength of concrete, width of cracks and coefficient of friction between weathered concrete and corroded steel Fang et al [16] studied the bond force of reinforcement and concrete when corroded. .. different concrete strength levels with steel anchor lengths Thereby, consider the influence of adhesion stress between concrete and the reinforcement Continuing to evaluate the adhesion of concrete and