Tài liệu Guideline2009

Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- Japan Concrete Institute Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- Japan Concrete Institute All rights reserved. No part of this work may be reproduced, transcribed or used in any form of by any means-graphic, electronic, or mechanical, including photocopying, recording, typing, Web distribution, or information storage and/ or systems-without the prior written permission of the Japan Concrete Institute. Preface In spite of numerous efforts to eliminate cracks from concrete structures, there are still many cracked concrete structures. Some cracks are very harmful and should be repaired as soon as possible, while other cracks are almost harmless. Therefore, a good guideline on how to deal with cracks in concrete structures has long been needed. JCI published “Practical Guideline for Investigation and Repair of Concrete Structures” in 1980, a second version followed in 1987, and a third version was followed in 2003. In this third version, English edition was also published. Then in 2009, A fourth version was published in Japanese in 2009. This volume, titled “Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009-“ is the English edition of this latest version. It is believed that this guideline will be much use when cracks are detected in existing concrete structures, both in Japan and overseas. Contents Chapter 1 General ·········································································································· 1 1.1 Scope and Objective ············································································································ 1 1.2 Procedure from Investigation to Repair and Strengthening ·············································· 2 1.3 Terms and Definitions ·········································································································· 11 Chapter 2 Investigation ································································································ 11 2.1 General ································································································································· 11 2.2 Standard Investigation ········································································································ 11 2.3 Detailed Investigation ········································································································· 25 Chapter 3 Cause Estimation······················································································ 44 3.1 General ································································································································ 3.2 Cause of Cracking ··············································································································· 3.3 Cause Estimation Based on Standard Investigation ·························································· 3.4 Cause Estimation Based on Detailed Investigation ···························································· 44 44 45 76 Chapter 4 Evaluation of Cracks ·············································································· 79 4.1 General ································································································································ 4.2 Evaluation-I (Applied for Cracks due to Drying Shrinkage, etc.) ····································· 4.3 Evaluation-II (Applied for Cracks due to Carbonation and Chloride Attack, etc.) ·········· 4.4 Evaluation-III (Applied for Cracks due to Combined Deterioration, etc.) ······················· 79 84 86 94 Chapter 5 Judgment of Necessity of Repair and Strengthening ············ 96 5.1 General ································································································································ 96 5.2 Methods of Judgment ········································································································· 97 Chapter 6 Repair and Strengthening ···································································· 101 6.1 General ································································································································ 101 6.2 Design of Repair and Strengthening ··················································································· 102 6.3 Repair Methods ····················································································································111 6.4 Strengthening Methods ······································································································· 124 6.5 Repair and Strengthening Materials ·················································································· 143 6.6 Repair and Strengthening Works ······················································································· 151 6.7 Inspection ···························································································································· 154 6.8 Records and Interim Observations····················································································· 155 Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- 1 Chapter 1 General 1.1 Scope and Objective (1) This Guideline covers the practicable investigations of cracked concrete members or structures, cause estimation, evaluation, judgment of the necessity of repair or strengthening, selection of the most effective repair and strengthening method, and the case studies. This Guideline applies mainly to cast-in-situ concrete structures. (2) This Guideline covers the cracks generated in a concrete member or structure after casting and during the service life. (3) The main users of this guideline are the owners including managers of the concerned structures as well as engineers who are working for investigation, cause estimation, evaluation, judgment, and repair or strengthening of cracked concrete structures. [Comments] (1) and (2) 1) Targeted concrete members or structures This Guideline mainly covers the common cast-in-situ reinforced concrete and prestressed concrete structures which include buildings, bridges, pavements, concrete dams, etc. This Guideline does not cover the precast reinforced concrete structures. However, it can be used for such structures with certain limitations and restrictions. Engineers assigned to judge such structures must be specially trained and have advanced knowledge in this area. 2) Targeted cracks This Guideline covers the cracks which are developed in concrete members or structures after casting of concrete. The causes of cracking covered by this Guideline are summarized in Table 3.1. Countermeasures can be adopted during the design stage of concrete members or structures. This Guideline does not cover the countermeasures adopted in the design stage. The normally recommended items and methods for cause estimation of cracking, evaluation, judgment on the necessity for repair and strengthening and appropriate technical methods for repair and strengthening are explained in this Guideline. This Guideline does not deal with all conditions such as various types of structures, influences on third party, exposure conditions, etc. This Guideline can be used as a basic tool to judge how to evaluate the condition of structures, how to evaluate the causes of cracking, and what to do if repair and strengthening are necessary. Therefore, when this Guideline is applied, it is necessary to plan practical countermeasures taking into consideration of the various conditions such as its own unique environment, service loads, etc. 3) Technical contents The main users of this Guideline are from a beginner to a middle career engineer who is in-charge of a structure for maintenance and taking actions if there are cracks in the structures or concrete members. Therefore, this Guideline is prepared in a simple way for easy learning and application of the learned knowledge in concerned structures. This Guideline systematically described the process of investigation (Chapter 2), cause estimation (Chapter 3), evaluation (Chapter 4), judgment (Chapter 5) and repair and strengthening (Chapter 6). Moreover, examples are compiled in this Guideline that can be used as useful references by the engineers with a little professional experience in this field. 4) Necessity for re-investigation Crack widths generally fluctuate with service loads, seasonal change and age of the structure. Therefore, judgment may differ based on the time of evaluation. Even if a structure is judged not to do repair based on the result of investigation of the present condition of the structure, re-investigation is necessary in the future and appropriate measures may be adopted based on the future investigation. Therefore, a periodical investigation is to be suggested for the important concrete members or structures even though any repair actions are not necessary at the present condition. In such a case, it is wise to suggest 2 Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- re-investigation, evaluation, judgment and selection of a repair and a strengthening method based on the evaluation and the judgment in future. (3) 1) The main users of this Guideline The intended users of this Guideline are owners, managers, and beginner to mid-level engineers who are assigned for examining the structure or concrete members. Therefore, this Guideline is prepared in a simple way so that the users can gain the knowledge of the subject and apply the learned knowledge in practice. If a user cannot understand some parts or has some doubts, he/she should ask expert engineers for help. This Guideline assumes that the beginner is a person who does not have practical experiences regarding crack-related problems of concrete, such as a resident who discovers cracks in concrete members in his/her apartment building and a municipality official who is just nominated as a maintenance engineer of concrete structures. 2) Limit of this Guideline As stated earlier, this Guideline is prepared in a simple and understandable way for a series of acts from the investigation to the selection of the repair and strengthening of a crack so that the beginner to the mid-level engineers who are engaged with the maintenance of concrete structures can easily use it. But, when it is not possible to deal only by this Guideline, the judgment of an expert engineer who has advanced knowledge and the experience in investigation, repair, and strengthening of concrete structures is needed. 1.2 Procedure from Investigation to Repair and Strengthening A flow diagram of the general procedure from investigation to repair and strengthening of concrete structures with cracks is shown in Fig. 1.2.1. Identification of crack Standard inves tigation for caus e es timation (2.2) Detailed inves tigation for caus e es timation (2.3) Can it be es timated the caus e of cracking? No Yes The caus e es timation (3.3) ［W hen detailed inves tigation was conducted (3.4）］ Selection of type of es timation (4.1) Inves tigation for evaluation （W hen it is neces s ary） Evaluation (4.2)(4.3)(4.4)* Judgement (5)* Repair and s trengthening (6) Additional inves tigation for repair and s trengthening （6.2.3） （Mainly, inves tigation s uch as cons truction environment, amount and range, etc.） Note1) A parenthes is ( ) in the flow means number of chapter or s ection. Note2) An as teris k * in the flow means that the evaluation and judgment method are different by the s election of Evaluation-I, Evaluation-II and Evaluation-III. Fig. 1.2.1 Procedure from the investigation of cracks to the application of repair or strengthening Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- 3 [Comments] The procedure from investigation to repair and strengthening in this Guideline is shown in Fig. 1.2.1. Strictly, this procedure could not correspond to some cracks while this flow diagram shows a standard procedure that can correspond to most of the cracks. When cause estimation, evaluation, judgment and selection of repair and strengthening methods are difficult, it is preferable to receive advice from professional engineers who have advanced knowledge and experiences. 1) Identification of the crack A series of repair and strengthening begins upon identification of cracks in a structure. Thus, the identification of crack shown in Fig. 1.2.1 is defined when some actions are intended to consider against the crack. 2) Standard investigation and detailed investigation The investigation is classified into “a. investigation for cause estimation” as a principal objective of investigation and “b. additional investigation for evaluation and repair/strengthening design.” The methods and the principles of standard investigation and detailed investigation are described in 2.2 and 2.3, respectively. a. Investigation for cause estimation After crack identification, standard investigation for cause estimation of the crack is executed first. Sometimes the cause estimation might be possible only by the result of standard investigation. However, when the information obtained from standard investigation is insufficient, detailed investigation including nondestructive tests, minor destructive tests, coring, destructive tests, laboratory test, etc. is required. When a crack is estimated to be caused by alkali aggregate reaction, frost damage and chemical attack, detailed investigation for evaluation might become necessary in order to obtain further information on degradation of a concrete member or structure. b. Investigation for evaluation and repair/strengthening design Sometimes all the information necessary for repair/strengthening design might be able to be covered by a. However, additional investigation is often needed to specify the environment at site and amounts of the repair/strengthening. 3) Cause estimation In this Guideline, first of all, the cause of cracking is estimated from the result of standard investigation. When it is judged that the information collected by standard investigation is insufficient for cause estimation, detailed investigation is carried out for adding further information for precise estimation. When the causes are still unclear, advice from expert engineers may support the estimation. 4) Evaluation After completing the cause estimation, the influence of cracking on structural performance of a concrete member or structure is evaluated. That is, the evaluation in this Guideline is objectively conducted based on the result of investigation and the estimated causes. For this purpose, the evaluation should be done taking into account the influences of cracks on required performance of a member or structure at present and in the future. Therefore, in this Guideline, proper methods of evaluation should be selected based on the estimated causes of cracking. The classification of the evaluation methods is described in 4.1. 5) Judgment Judgment is conducted in consideration of the result of evaluation, economical conditions, social importance of structure, etc. When judgment is made according to this Guideline, the owner or the manager of the structure is required in advance to specify required performance of the structure or member at present and in the future, an expected remaining service life by the owner, social importance, budget allocation for repair and strengthening, etc. For instance, repair or strengthening is not necessary if the cause of cracking is clearly estimated and the evaluation results indicate that structural performance might not be degraded over a long period of time (compared with the expected remaining service life). Conversely, if evaluation results conclude that 4 Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- structural performance would be degraded below the required levels within a short term (in the near future from the identification of the crack), repair or strengthening is necessary. In case of budget restriction, some countermeasures might be selected, such as an increase in frequencies of investigation, repair for aesthetic purposes, limitation of services, change in use, demolition/removal, etc. 6) Repair and strengthening Design and execution of repair and strengthening are done in consideration of the estimated cause of cracking, the evaluation and judgment results, etc. Repair and strengthening methods are preferably selected based on the life-cycle assessment, asset management as well as the prediction of future deterioration of concrete member or structure. 1.3 Terms and Definitions The technical terms used in this Guideline are defined as follows: (1) Investigation: action to grasp the current state of concrete members (structures) and to collect the definite data on concrete members (structures) and cracks. (2) Evaluation: action to objectively grasp the influence of the targeted cracks on the performance of concrete members (structures) at the present and in the future. (3) Judgment: action to decide the necessity of repair and strengthening according to the influence of the targeted cracks on the performance of concrete members (structures) as well as special limitation, such as importance of structure, which is obtained as the results of evaluation. (4) Repair: action taken for recovering the performance of degraded (deteriorated and/or damaged) structures by cracks. The main objectives of repair are to reduce water and air permeability, to control the rate of corrosion, to improve the aesthetic view, etc. Strengthening of concrete or structural members is not covered in repair. (5) Strengthening: improvement of structural performance such as the load carrying capacity etc. to a desired safe level. (6) Crack width: opening width on the surface of the structure normal to the direction of the crack. (7) Initial defect: cracks, honeycomb, cold joint, etc. generated during construction. These are the construction defects. (8) Deterioration: changes in material performance with time after hardening of concrete due to the some changes in concrete itself or by cracks due to corrosion of steel in concrete. (9) Damage: cracks or spalling generated on the surface of concrete caused by an earthquake or impact for a short period of time. (10) Degradation: a term that covers initial defect, damage and deterioration. (11) Expert engineer: An engineer having advanced knowledge and experience on concrete technology and diagnosis of damaged concrete structure. In Japan, “concrete inspectors” and “professional concrete engineers” are certified by the Japan Concrete Institute (JCI). (12) Owner: owner or manager of the structure. (13) Residual period: residual period that the concrete member or structure could satisfy the required performance from the time of investigation of the crack, evaluation, judgment, repair and strengthening. (14) Remaining service life: residual life to reach the design service life from the time of investigation of the crack, evaluation, judgment, and repair and strengthening. (15) Expected remaining service life: residual life which is expected by the owner to use the concrete member or structure from the time of investigation of the crack, evaluation, judgment or repair and strengthening. (16) Minor destructive test: an examination to measure the strength of concrete using the collected samples by partially destroying the structure. [Comments] In this Guideline, the following technical terms are defined. The other technical terms used in a particular section are defined there accordingly. Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- 5 (1) In this Guideline, “investigation” is defined as a technical and objective action and “inspection” as an administrative and subjective action. That is, investigation includes technical contents, such as what tests should be performed and what should be measured, etc, while inspection includes administrative and businesslike contents, such as who is the person in charge and what items should be inspected, etc. Since the inspection of this Guideline is defined as the action to grasp the current state of concrete members or structures and generic term of the action to investigate whether there are some defects or not in the targeted structure, sometimes investigation is included in inspection. (2) In this Guideline, “evaluation” is defined as an objective action to grasp the influence of cracking on the performance of concrete members or structures at the present and in the future by using the results of investigation and cause estimation in order to perform the technical judgment from the cause estimation of cracking to the judgment of the necessity of repair and strengthening. Moreover, the evaluation methods can be classified into the following three types: 1) Evaluation-I (applied for cracks due to drying-shrinkage, etc.) Evaluation-I is applicable to the cracks that stop spreading within several years after casting, such as drying-shrinkage cracks and thermal cracks etc. The evaluation can be conducted by investigating the documents and also investigating the current state of concrete members or structures. In general, this evaluation is applicable to a case when the structural performance is able to keep over requirements by repair during the remaining service life or the expected remaining service life by the owner. When Evaluation-I is applied, a crack width at the time of investigation or repair can be evaluated taking into account durability against corrosion of steel bar, water tightness and environmental conditions, etc. The criteria of the crack width for Evaluation-I are specified in 4.2. 2) Evaluation-II (applied for cracks due to chloride attack, carbonation, etc.) Evaluation-II should be applied for the cracks which progress with time, such as the cracks due to chloride attack and carbonation. Furthermore, evaluation for these cracks can be conducted with the results of detailed investigation as well as the investigation of documents and visual observation of the concrete members or structures. These kinds of cracks are often discovered at several years or decades after construction. Therefore, it may possible that the performance degradation has already been induced at the time of investigation or repair. Moreover, since the mechanisms and the factors of the cracks are different depending on the causes, these kinds of cracks should be evaluated by understanding the performance degradation at the time of investigation, repair or strengthening, and considering the remaining service life or the expected remaining service life by the owner. The standard evaluation criteria are specified in 4.3 according to the causes of cracking. 3) Evaluation-III (applied for cracks due to combined deterioration, etc.) Evaluation-III is applied for the cracks when Evaluation-I or Evaluation-II is not applicable because the cause of crack is due to the combined deterioration or when the verification of structural performance of concrete member or structures is needed. This evaluation should be conducted by an expert engineer who has the license for concrete inspection. This evaluation is applied when a long-term (more than 20 years) remaining service life or a long-term expected remaining service life by the owner is required. Moreover a crack caused by the mechanical reasons such as changes in support or loading condition should be evaluated by Evaluation-III. (3) In this Guideline, judgment is conducted by considering the restrictions, such as social importance of concrete member or structure, budget of the owner and the scenario of maintenance including the remaining service life or the expected remaining service life, life cycle assessment and asset management. Therefore, the judgment includes the increase in frequencies of inspection, repair for aesthetic purpose, limitation of service, change of use, demolition etc. (4) Cracks in concrete will degrade structural performance such as safety, influences on the third party, serviceability, durability, etc. Repair is defined as an action to recover and improve the performance except the load carrying capacity to their required levels (generally at least the level of the performance 6 Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- without any cracks). (5) Repair is performed against a crack itself in order to improve the performance such as waterproofness, while strengthening is performed against the concrete members or the structures. In this Guideline, strengthening is defined as an action to recover and improve degraded structural performance caused by the cross-sectional loss of steel bar and degradation of bond between steel bar and concrete due to corrosion. Structural performance after strengthening should definitely satisfy the required performance; for example either load carrying capacity against current load actions or load carrying capacity due to more loads in future. Furthermore, strengthening may enhance structural performance compared to the originally designed level. There are two types of members in a concrete structure. One is a member to support loads acting on the structure, which is called as a structural member, while the other is that to satisfy the non-mechanical performance, such as fire resistance, heat insulation, water tightness, air tightness, sound insulation, etc., which is called as a non-structural member. Since an unexpected crack may cause performance degradation of a concrete member or structure, examination for repair is necessary for both structural and non-structural members. Moreover, examination for strengthening is sometimes necessary for a structural member in addition to that for repair. When strengthening is judged to be necessary, a repair work may be added depending on the cause of crack and the applied strengthening method. In this Guideline, when a crack is initiated in structurally unimportant directions even in a structural member, the same treatment as for a non-structural member may be applied. (6) A crack width is defined as the surface opening perpendicular to the crack path. Generally, rapid degradation is observed for a wider crack. Contrary, degradation may not be so significant during the service life of structure for a narrower crack. Therefore, the width of crack is an important factor for judgment on the necessity of repair and strengthening as well as selection of a suitable repair and strengthening method. Additional notes related to the crack width are given below: (i) The surface crack width generally varies with the depth inside concrete. A larger width is observed on the surface and it gradually reduces with depth. The surface crack width also greatly depends on the location of steel bar in concrete. A larger cover depth will lead to increase the crack width on the surface. Therefore, degradation rate cannot be generalized with respect to the crack width. (ii) Dimensional change such as shrinkage and expansion of concrete structures occurs with the variation of temperature as well as moisture content and imposed service load over the structure. It indicates that the crack width is not necessarily a constant value. (iii) Multidirectional cracks can be generated on the concrete surface, therefore it may be difficult to fix a particular direction for measuring the crack width. (iv) The crack width may vary along the crack path. For these reasons, it is necessary to specify the time of measurement, position, and the method of measurement of crack width, which will be utilized to judge the present condition of the structure, causes of cracking, and possible necessary countermeasures. In addition, the crack width for Evaluation-I related to steel bar corrosion is the maximum on the surface of concrete at the position of steel bar. (7) Defects are generated in a structure during construction as well as after construction of a structure. Defects that are generated during construction, such as cracks, honeycomb, cold joint, etc. are particularly called as “initial defect”. In addition, a crack caused by "A9: drying shrinkage" presented in Table 3.1 occurs after the removal of formwork or during curing. There is a case that this kind of crack occurs during construction (several days to several months) or several years after the start of service. Therefore, in this Guideline, the former are classified as “initial defect” because a crack due to drying shrinkage based on the former tends to generate due to the early removal of formwork and the insufficient curing period. Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- 7 (8) In this Guideline, “deterioration” is defined as a process which adversely affects the structural performance, such as steel corrosion due to chloride attack and carbonation and change in properties of concrete itself due to alkali aggregate reaction, frost damage, etc. Moreover, as mentioned in comment (7), the cracks that occur several years after the start of service by “A9: drying shrinkage” are classified as “deterioration” because it tends to generate when the concrete member or structure is always exposed to drying condition and when the relative humidity around the structure drastically decreases by weather change. (9) In this Guideline, degradation that occurs in a short term and does not change with time, such as a crack or peeling of concrete generated by earthquake, impact, etc. is defined as “damage”. (10) Degradation is defined as a general term including initial defect, damage and deterioration. (11) Judgment on the necessity of repair is comparatively easy when the cause of crack is clear and the degradation of the structure can be observed with the naked eye, such as water leakage, deformation, and spoiled appearance. However, a crack generated in a real structure may come in different form and it may be difficult to find out the exact causes of cracking even after detailed investigation. In some cases, judgment on the necessity for repair and strengthening is difficult even though degradation is clearly observed over the surface. Therefore, in this case, judgment as to the cause of crack, the necessity for repair/strengthening, and repair/strengthening methods, if required, must be made by an engineer who is familiar with the subject matter and has extensive experiences in this area. In Japan, a “concrete inspector” and a “professional concrete engineers” have been certified by the Japan Concrete Institute since 2001 and 1971, respectively. Both categories are registered as concrete experts. The concrete inspector is certified as having advanced engineering ability for investigation, diagnosis, and selection of repair and strengthening strategies for the deteriorated concrete structures. A professional concrete engineer is mainly certified as having advanced knowledge in concrete technology and the ability to supervise the construction by ready-mix concrete and in-situ casting of concrete. Here, the term “expert engineer” as used in this Guideline also includes persons with advanced knowledge of concrete technology. A first-class architect and a building engineer are also included in this category. A person with engineering knowledge and experience equal to or greater than that of concrete inspector or professional concrete engineer can also be considered as an “expert engineer”. An engineer is always responsible for all his/her judgments related to repair and strengthening, and must keep him/herself up to date with the present state of the art. (12) The owner in this Guideline is an owner or a manager of a concerned concrete structure. It is indicated the person who can actually decide the importance of structure, budget, and necessity of repair and strengthening. For instance, it corresponds to the management society of an apartment house or the municipality that manages buildings, RC bridges, and so on. Here, a consulting engineer who is given the authority of judgment and decision of technical point by the owner is also called as the owner for descriptive purposes. (13) Generally, the durable period of a concrete structure is set as the period that maintains the required performance during the design service life at the planning and design stages. Therefore, it is common that the design and construction of concrete structure are executed in such a way so that the durable period is longer than the design service life. However, when a crack occurs due to some causes that were not considered in the design stage and the performance of the concrete member or structure is degraded, there is a case that is compelled to evaluate as the durable period shorter than the design service life even if repair and strengthening is performed. Therefore, in this Guideline, the technical term as the “residual period” is defined as the period during which the required performance of structure can be maintained after the execution of investigation, evaluation, judgment, and repair and strengthening. (14) There are three concepts about the service life; one is the “design service life” that is set based on how many years the owner wants to use the structure in consideration of the amortization period of the 8 Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- structure and social importance. The second is the “elapsed service life” that is the period for which a structure has been actually used after construction. The third is the “remaining service life” that is the period from the present to the design service life. In this Guideline, the remaining service life is defined based on the judgment of the necessity of repair or strengthening and the execution of repair or strengthening design considering the “residual period” after investigation, evaluation, judgment, and repair and strengthening. (15) In the other guidelines, the technical terms, such as the design service life and the residual period are often used. Moreover, there are many descriptions assuming that the service life and the residual period can be determined easily. However, in many cases, the inhabitants of an apartment or the owner of a structure which was constructed a long time ago do not know the design service life at the design stage and therefore cannot set the remaining service life. In addition, there are also cases that an owner wants to use the structure over a design service life or make an alternation to the structure for a shorter period than that set at design by the change of the social importance of the structure and economic circumstances. In other words, it can be concluded that judgment and design of repair and strengthening are performed based on the owners’ intention how long he/she wants to use the structure in the future. Therefore, in this Guideline, the expected remaining service life is newly introduced as the period when an owner expects to use the structure after investigation of crack, evaluation, judgment, repair or strengthening (it is included neither the repair nor the strengthening work). It is described to perform the judgment of necessity of repair and strengthening and the repair and strengthening based on the expected remaining service life by the owner. When the remaining service life can be set by using the design service life at the design stage, in the judgment and the designing of repair and strengthening, it is necessary to choose either of the expected remaining service life by the owner or the remaining service life. In this case, it is decided to conduct the judgment and the design of repair and strengthening based on a period by the judgment of the owner. The concepts of repair and strengthening designs are shown in Figs. C.1.3.1 and C.1.3.2, respectively. It is very important for design of repair and strengthening to define the level of performance, such as safety, serviceability and durability necessary for the structure, to grasp the performance of the structure at the time of investigation of crack and adequately to decide the level of performance to recover by repair and strengthening and the duration of the effects of repair and strengthening. In addition, considering the lifecycle of the structure, it is important to conduct sufficient examination considering that it is possible to conduct the reasonable maintenance not only by one time of repair but also by multiple repair. (16) A minor destructive test is an examination to perform to get information, such as compressive strength, carbonation depth, chloride content in concrete, residual expansion by alkali aggregate reaction, etc. by destroying a part of the structure and by using the collected samples from the structure. Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- 9 The Investigation, evaluation, judgment or execution of repair Service start Design service life Remaining service life Elapsed service life Expected remaining service life Residual period on serviceability etc. when a repair is executed. Repair* Serviceability etc. When a repair is executed one time When crack occurs and repair is not executed. Required level of performance Residual period on serviceability etc. when a repair is not executed. Elapsed year Residual period on the safety performance when repair is executed. Safety performance Required level of performance Repair* When a repair is executed one time When crack occurs and repair is not executed. Residual period on the safety performance when a repair is not executed. Elapsed year * When repair is executed, the performance such as waterproof or the aesthetic can be recovered or improved, while the safety performance such as the load carrying capacity cannot be recovered or improved. However, the period that the concrete member could satisfy the various performances can be extended (the durability is recovered or improved). Fig. C.1.3.1 Concepts of design for repair (only one repair during a life time) 10 Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- Service start The Investigation, evaluation, judgment or execution of strengthening (repair) Design service life Remaining service life Elapsed service life Expected remaining service life Residual period on serviceability etc. when a strengthening (including repair) is executed. Strengthening* Serviceability etc. Required level of performance When crack occurs and strengthening (or repair) is not executed. When a strengthening (including repair) is executed. Residual period on serviceability, etc when a strengthening (or repair) is not executed. Elapsed year Residual period on the safety performance when strengthening (including repair) is executed. Strengthening* Safety performance Required level of performance When crack occurs and strengthening (or repair) is not executed. When a strengthening (including repair) is executed. Residual period on the safety performance when a strengthening (or repair) is not executed. Elapsed year * When strengthening is executed, the mechanical performance such as load carrying capacity can be recovered or improved, and the performance such as water tightness, the aesthetic can be also recovered or improved by a combination with suitable repair. Besides, the period which the concrete member could satisfy the various performances can be extended (the durability can be recovered or improved). Fig. C.1.3.2 Concepts of design for strengthening Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures -2009- 11 Chapter 2 Investigation 2.1 General (1) The main objective of investigation is to collect data for the estimation of the causes of cracking of a structure or its members. These data are also necessary for subsequent evaluation of cracks, judgment of the necessity of repair and strengthening. (2) There are two types of investigation, such as standard investigation and detailed investigation. [Comments] (1) Investigation described in this chapter is the beginning step for cause estimation, evaluation of cracks and a selection of repair and strengthening. Information based on the appropriate investigation enables not only to predict the causes of cracking but also to select suitable methods of repair and strengthening. This Guideline recommends identifying the causes of cracking before selection of a repair and strengthening method. Hence, cause estimation of cracking plays a significant role in this Guideline. Furthermore, the investigations proposed in this chapter are useful for evaluation of cause of cracks, repair and strengthening. (2) In this chapter, "investigation" is divided into two steps, such as "standard investigation" and "detailed investigation." Standard investigation must be carried out as the preliminary investigation. The detailed investigation should be carried out in the case that cause estimation of cracking, repair and strengthening cannot be performed based on the standard investigation. Table C.2.1.1 shows a list of investigation methods proposed in this Guideline. The applicable grades of each testing method are classified as ~, { and U for the cause estimation, evaluation of cracks, repair and strengthening. 2.2 Standard Investigation (1) Standard investigation is carried out by investigating the documents and visual inspection of structures. (2) Investigations of documents and observation of structures should include the following items: 1) Investigation of documents a. Engineering drawings, design reports and specifications (drawings, steel bar arrangement, structural calculation results, etc.) b. Construction record such as materials used, mixture proportion, placing, curing method, construction schedule, sub-soil investigation report, formwork, weather condition during placement of concrete c. History of the past investigation, repair and strengthening (maintenance record of structure, records of repair and strengthening, renovation, claim, etc.) d. Service load condition (conditions at design and at present) e. Climate condition (temperature, relative humidity, wind velocity, wind direction, height of wave, direction of wave, air pressure, etc.) f. Geological condition (distance from the sea, existence of harmful agents, such as de-icing agents, snow melting agents, etc.) g. Ground condition (vertical distance to the adjacent structures, conditions of retaining wall, foundation, etc.) 2) Visual observation of structures a. Investigation of the condition of the cracks (such as crack width, crack length, crack area, crack pattern, existence of penetrating crack, etc.) b. Investigation of other phenomena occurred due to the cracks (peeling of concrete cover and finishing materials, honeycomb, pop out, efflorescence, etc.) c. Investigation of inconveniences due to cracks (moisture leakage, corrosion of steel bars, deflection of structural members, appearance, etc.) d. Investigation of unusual vibration (at driving and at walking) a Chapter e Ite s Chap 2 ,nYestLgatLon or investigation art Items of inspection Type of investigation S t a n d a r d I n v e s t i g a t i o n D o c u m e n t r e s e a r c h Engineering drawings Collection of records, confirmation of site and hearing Drwings, re-bar arrangement, structural calculation, test results of materials used, specifications, etc. Document to be researched Drying shrinkage Way to use of results（※2） Repair and strengthnening EvaluationII EvaluationIII (Carbonation, salt damage, ASR frost damage, chemical corrosion etc. (Stractural crack),(extre me defect, composite deterioration etc.） Cause estimation, evaluation ○ ○ ○ ○ Data of materials (cement, aggregate, mineral and chemical additives mixing Construction water），mixture proportions，casting, curing, plan, quality control data, Cinfirmation of ducument records condition of soiul, environmental condition at casting, weather condition, etc ○ ○ ○ ○ Investigation, history of repair and strengthening ○ ○ ○ Cinfirmation of ducument, visual inspection, hearing ○ ○ ○ Cinfirmation of ducument, map, visual inspection, feeling, hearing ○ ○ ○ Past investigation, repair and strengthening, renovation, dakage, claim, Cinfirmation of ducument records at finding of crack Confirmation that present load condition Condition of does ont exeed the load condition at service load design Weather, condition of sea, environment and foundation Temperature, himidity, CO2 consentration, swoop salinity, chemical component, distance from sea, existence of de-icing agent, snow melting agent, cold area nor not, spring area or not, vibration,soft ground or not Type of investigation Items of inspection State of ctacks peeling and flaking Visual inspection of structure Hunycomb Water leakage Test methods, equipments Drying shrinkage Width Visual inspection, scale, crack scale and microscope Length, total length Visual inspection, scale, digital camera Position, area Visual inspection, scale, digital camera Pattern Visual inspection, digital camera Difference in level Visual inspection, scale Penetration Visual inspection, scale Position and area of peeling of concrete coverand finishing Visual inspection, test hammmer, scale Position and area Visual inspection, scale ○ Position and area Visual inspection, scale ○ Visual inspection, scale ○ Visual inspection ○ Change of Position and area color, Depositionio Color Popout Visual inspection, scale n cold joint Position and area Unusual sound, inconvenience, vibration at driving and walking, inconvenience of Feeling,phone,visual inspection, scale Unusual fittings feeling Position Feeling,phone,visual inspection, scale ○ (Carbonation, salt damage, ASR frost damage, chemical corrosion etc. ○ ○ － ○ － Way to use of results（※2） Repair and strengthnening Cause estimation, evaluation Estimation ning ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Note Selection Judgment for Examination of repair of material necessity of of execution and repair and and date strengthne strengthening method ○ ○ － － ○ EvaluationIII (Stractural crack),(extre me defect, composite deterioration etc.） ○ － Type of evaluation（※1） EvaluationII Note ning Cinfirmation of ducument Evaluation I n s p e c t i o n Estimation Judgment for Examination Selection of repair necessity of of material of execution and repair and and date strengthne strengthening method ○ ○ ○ ○ ○ ○ ○ ○ Classification based on fihure of crack pattern Rekation to environmental condition and ground condition Comarison with crack width limit Criteria of judgement for necesstity of repai and strengthening Classification based o ○ ○ Judgement for necesstity of repai and strengthening Rekation to environmental condition and ground condition ○ ○ Judgement for necesstity of repai and strengthening Rekation to environmental condition, servicebility performance and ground condition 1：○Special needs for investigation. In the case of extreme deterioration and composite deterioration in Evaluation III,there will be needs for investigation. 2： ，○， in order of importance for investigation. 12 Type of evaluation（※1） Evaluation Chap 3 Cause estLmatLon of cracks Chap 4 (YaOuatLon Chap 5 Judgment for necessLty of repaLr and strengthenLng Chap 5 Judgment for necessLty of repaLr and strengthenLng Chap 6 5 e p a L r a n d stregnthenLng Chap 3 Cause estLmatLon of cracks Chap 4 (YaOuatLon a le investigation Chapter te s a t Chap 2 ,nYestLgatLon o Chap 3 Cause estLmatLon of cracks Chap 4 (YaOuatLon Way to use of results（※2） Type of evaluation（※1） Evaluation Type of investigation Items of inspection Crack progress Visual inspection, crack scale, microscope, π-type dispacement gauge, contact type gauge, degital camera, acoustic emission, laser method Position, depth and area of peeling and flaking of concrete cover and finishings Sampling of core and thermographic method Estimation of strength Concrete D e t a i l e d i n v e s t i g a t i o n Nondestructive , minor destructive test and test with core specimen O n s i t e i n v e s t i g a t i o n Steel bar Investigat ion of innrr part/quali ty of structure Degree of quality Homogeneity foundation condition of Foundation structure Investigation of vibration of structure Structure, member ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Crack depth Sampling of core and ultra sonic method ○ Cover thickness ○ ○ ○ Radar method, impact elastic wave method and ultrasonic method ○ ○ Position of steel bar, bar arrangement and bar diameter Radar method, electro magnetic reasonance method, ulutrasonic method,X-ray transmission method ○ ○ Corrosion rate half-cell potential ○ polarization resistance X-ray transmission method, impact elastic wave method, CCD camera Tracer method,thermographic method (visual inspection is impossible） ○ ○ Visual inspection and phenolphthalein method Crack depth Deposition Visual inspection and scale Visual inspection ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Confirmation of existence ○ ○ ○ ○ Comparison to cover thickness Comparison to engineering drawings and construction record. Comparison to carbonation depth Comparison to engineering drawings and construction record. ○ ○ ○ Classfiying with corrosion rate, judgment for necessity of repair and strengthening ○ ○ ○ ○ ○ ○ Position and amount of insufficient grouting ○ ○ Exisitence, amount and route of leakage ○ ○ ○ ○ ○ Comparison to engineering drawings and construction record. ○ ○ ○ Classification to corrosion rate, judgment for necessity of repair and strengthening ○ ○ ○ record. ○ Comparison to cover thickness, estimation carbonation progress and confirmation of consentration of chloride ion in concrete Comparison to cover thickness Confirmation of existence of Deposition ○ ○ record. Comparison to engineering drawings and construction Comparison to engineering drawing and carbonation depth ○ ○ Comparison to engineering drawings and construction Comparison to specified value, comparison of crack and failure ○ ○ ○ Comparison to cover thickness，comparison between member thickness of sound area and design thickness ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Classfiying on corrosion velocity ○ ○ Comparison to construction record. ○ Sign of ASR ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Measurement of temperature and R.H., consentration of CO2,swoop salinity and other chemical component Settlement of foundation, differential settlement Visual inspection by excavation, surveying, surface wave, electro magnetic wave method and elastic wave method Eccentric earth pressure Visual inspection by excavation, surveying, surface wave, electro magnetic wave method and elastic wave method Side displacement isual inspection by excavation and surveying Inveswtigation of live load, traffic, cargo handling, load test(oil pressure jack and actual live load), stress frequency ○ Stiffness ○ Test by actual dynamic vibration Vibration with shaking machine and with impact load using falling weight Vibration with shaking machine and with impact load using falling weight ○ ○ Degree of reduction of stiffness of structure Comparison to standard criteria Relation to immerging velocity of aggressive component Comparison to design value Judgment for necessity of repair and strengthening ○ Environmental condition which affect deterioration around structure Influence of load at driving and usage of vehicle Influence of earthquqke ○ ○ ○ Visual inspection and phenolphthalein method Type of aggregate (river stone, crushed Visual inspection stone etc.） exsistence of shell(exsistence of sea sand） Visual inspection Maximum size Visual inspection and scale Existence of reaction rim Visual inspection Existence of crack of coarse aggregate Visual inspection Existence of water leakage Visual inspection Existence of impurities Visual inspection ○ ○ Scale and micro scale Visual inspection Scale Visual inspection, inspection mirror, R-type gauge Visual inspection and scale ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Carbonation depths and Margin from cover depth to carbonation depth ○ ○ ○ Judgment for necessity of repair and strengthening Relation with environmental and ground conditions Comparison to design strength ○ ○ ○ Visual inspection, scale Note ○ Confirmation of existence, amount and route Comfirmation of existence and impurities Comparison between design value and estimated value ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Relation between the differential settlement,eccentric earth pressure and side displacement and the foundation Stability of structure as a whole Comparison between design value and estimated value, deflection and deformation of member, strain of concrete and steel, settlement and slant and displacement of foundation Confirmation of stress frequency and Judgment based onspecific frequency anddecay constant 1：○Special needs for investigation. In the case of extreme deterioration and composite deterioration in Evaluation III,there will be needs for investigation. 2： ，○， in order of importance for investigation. 13 Investigation of Structure, structural capacity and member deformation ○ ○ Diameter of steel bar Types of steel bar (round type, deformed type) Spoacing of steel bar Condition of bended zone Cover thickness Estimation Judgment for Examination Selection of repair necessity of of material of execution and repair and and date strengthne strengthening method ning ○ Chemical corrosion Environment Cause estimation, evaluation ○ Corrosion rate of steel Environmental condition of structure (Stractural crack),(extre me defect, composite deterioration etc.） ○ ○ Water leakage Others (Carbonation, salt damage, ASR frost damage, chemical corrosion etc. ○ ultrasonic method, impact elastic wave method, thermographic method, test hammmer Others Aggregate Repair and strengthnening EvaluationII EvaluationIII ○ Internal crack and voids Insufficient grouting Concrete ○ Size and thickness of member Corosion velocity Destruct ive test Strength test by rebound hammmer method, ultrasonic method, pull-out method, impact elastic wave method and with small core ultrasonic method, impact elastic wave method Thermographic method and ultra sonic method Drying shrinkage impact elastic wave method , radar method and ultra sonic method PC tendon Steel bar Document to be researched Chap 3 Cause estLmatLon of cracks Chap 4 (YaOuatLon Chap 5 Judgment for necessLty of repaLr and strengthenLng Chap 5 Judgment for necessLty of repaLr and strengthenLng Chap 6 5 e p a L r a n d stregnthenLng a le Chapter te s Chap 2 ,nYestLgatLon o investigation a t Chap 3 Cause estLmatLon of cracks Chap 4 (YaOuatLon Evaluation Type of investigation Items of inspection Compressive strength i n v e s t i g a t i o n Phisical test t e s t c l a s s i f i c a t i o n Analysis of chemical composition t e s t m e t h o d s (Stractural crack),(extre me defect, composite deterioration etc.） ○ ○ ○ Elastic modulus Strain measurement with wire strain gauge and diplacement meter meted(JIS A 1149) ○ ○ ○ Poisson's ratio Strain measurement with wire strain gauge and diplacement meter meted ○ ○ ○ Carbonation depth Phenolphthalein methodJIS A 1152)，differential thermal analysis，a Powder X-ray Diffractometer and EPMA ○ ○ ○ Migration of chloride ion due to carbonation Potential difference titrationwith electro node of silver chloride, Mercury( ) thiocyanate absorptiometry, silver nitrate titrationmethod, ion chromatographmethod(JIS A 1154,JCI-SC4,JCI-SC5) andEPMA ○ Chemical corrosion depth EPMA ○ Content of chloride Potential difference titrationwith electro node of silver chloride, Mercury( ) thiocyanate absorptiometry, silver nitrate titrationmethod, ion chromatographmethod(JIS A 1154,JCI-SC4,JCI-SC5) ○ Cause estimation, evaluation Estimation Note Judgment for Examination Selection of repair necessity of of material of execution and repair and and date strengthne strengthening method ning Comparison to design strength Comparison to value of sound concrete and standard value ○ Comparison to value of sound concrete and standard value ○ Comparison to cover thickness Comparison to estimated value of carbonation progress ○ Migration of chloride ion due to carbonation Chloride consentration at steel bar ○ ○ Comparison to cover thickness Regulation of JIS A 5308, comparison to steel corrosion criteria Potential difference titrationwith electro node of silver chloride, Mercury( ) thiocyanate Migration of chloride Judgment based in chloride consentration at concrete cover and distribution absorptiometry, silver nitra chromatographmethod(JIS andEPMA Alkaline content Atomic spectrophotometry ○ ○ ○ ○ Possibility of expansion due to ASR Chemical composition analysis, a Powder X-ray diffractometer, SEM-EDX, method, differential therma uranyl fluorescent method( Analysis of Deposition a c c o r d i n g t o Way to use of results（※2） Repair and strengthnening EvaluationII EvaluationIII (Carbonation, salt damage, ASR frost damage, chemical corrosion etc. Compressive strength test(JIS A 1107,1108) ( D e t a i l e d L a b o r a t o r y Document to be researched Drying shrinkage 14 Type of evaluation（※1） Chap 3 Cause estLmatLon of cracks Chap 4 (YaOuatLon Chap 5 Judgment for necessLty of repaLr and strengthenLng Chap 5 Judgment for necessLty of repaLr and strengthenLng Chap 6 5 e p a L r a n d stregnthenLng Estimation of mixture proportion （water, w/c, unit content of cement, content of additive, unit content of aggregate and impurities） Microstructural analysis ○ Quantification of OH in co ○ ○ ○ Judgment based on OH consentration in pore solution Method by J proportion of herdened concrete(F18）」 ○ ○ ○ Air-void spacing factors ○ ○ ○ Air content Linear traver ○ ○ ○ Pore size distribution Mercury intru ○ ○ ○ ○ Erosion depth from surface Visual inspec ○ ○ Carbonation progress velosity Accelerated ○ Rapid chlorid ○ Immerging velosity of chloride ) Remaining expansion ratio（ASR） Storage method at more than 40 andR.H.95％ (JCI-DD2)，Immerging method at 80 ，1mol/l NaOH（Canadamethod），Immerging method at 50 andsaturated NaCl（Denmark method） ○ Investigation of used aggregate type and reactive mineral Visual inspection, polarized light microscopy,a Powder X-ray diffractometer(JCI-DD3) ○ Comparison to engineering drawings and construction record ○ 「Test of ce Sodium gluco 2002） Linear traver Acceleration test Petrology test - - Estimation of expansion due to ASR Detection of composition of Deposition ○ Judgment based on content, spacing and diameter of air void ○ ○ ○ ○ ○ ○ Classification of corrosion rate Comparison to estimated value of carbonation progress Comparison to estimated value of chloride percolation Comparison between remaining expasive ratio and criteria Comfirmation of exisitence of risk of reactive minaral 1：○Special needs for investigation. In the case of extreme deterioration and composite deterioration in Evaluation III,there will be needs for investigation. 2： ，○， in order of importance for investigation. 3：acetic acid uranyl fluorescent method tre