BRITISH STANDARD
Grout for prestressing tendons Ð Grouting procedures
The European Standard EN 446 : 1996 has the status of a British Standard
ICS 91.100.10;91.100.30
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BS EN 446 : 1997
BS EN 446 : 1997
Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee B/525, Building and civil engineering structures, to Subcommittee B/525/2, Structural use of concrete, upon which the following bodies were represented:
Association of Consulting Engineers British Cement Association British Precast Concrete Federation Ltd. Concrete Society Department of the Environment (Building Research Establishment) Department of the Environment (Construction Sponsorship Directorate) Department of Transport (Highways Agency) Institution of Civil Engineers Institution of Structural Engineers Steel Reinforcement Commission
This British Standard, having been prepared under the direction of the Sector Board for Building and Civil Engineering, was published under the authority of the Standards Board and comes into effect on 15 November 1997 ©
BSI 1997
Amendments issued since publication
Amd. No.
The following BSI references relate to the work on this standard: Committee reference B/525/2 Draft for comment 91/10646 DC ISBN 0 580 28316 X
Date
Text affected
BS EN 446 : 1997
National foreword
This British Standard has been prepared by Subcommittee B/525/2 and is the English language version of EN 446 : 1996 Grout for prestressing tendons Ð Grouting procedures published by the European Committee for Standardization (CEN). EN 446 was produced as a result of European discussions in which the UK took an active part. The UK voted against this standard at the CEN Formal Vote stage because UK industry considered the standard to be insufficient in providing suitable specification requirements for grouting materials and procedures, particularly for highway bridges. The UK conducted significant development work and subsequently published Concrete Society Technical Report No. 47 Durable Bonded Post Tensioned Concrete Bridges , prepared by a Concrete Society Working Party in collaboration with the Concrete Bridge Development Group (September 1996), to which reference may be made. At the CEN Formal Vote stage, however, the analysis of voting resulted in a positive vote and in accordance with CEN/CENELEC Internal Regulations Part 2 : Common rules for standards work EN 446 was accepted as a European Standard. Cross-reference Publication referred to
Corresponding British Standard
ENV 1992-1-1 : 1991
DD ENV 1992 Eurocode 2: Design of concrete structures Part 1-1 : 1992 General rules and rules for buildings (together with United Kingdom National Application Document)
Compliance with a British Standard does not of itself confer immunity from legal obligations .
Summary of pages
This document comprises a front cover, an inside front cover, pages i and ii, an EN title page, pages 2 to 6, an inside back cover and a back cover.
©
BSI 1997
i
ii
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EN 446
EUROPEAN STANDARD NORME EUROPEÂ ENNE È ISCHE NORM EUROPA
March 1996
ICS 91.100.30 Descriptors: Cables, ropes, prestressed concrete, grouting, tests, injection, quality control
English version
Grout for prestressing tendons Ð Grouting procedures
Coulis pour ca à ble de pre contraintes РProce dures d'injection de coulis
Einpreûmo È rtel fu È r Spannglieder Ð Einpreûverfahren
This European Standard was approved by CEN on 1994-10-28. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CEN European Committee for Standardization Comite EuropeÂen de Normalisation Europa È isches Komitee fu È r Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels
©
1996 Copyright reserved to CEN members Ref. No. EN 446 : 1996 E
Page 2 EN 446 : 1996
Foreword This European Standard has been prepared by Technical Committee CEN/TC 104, Concrete Ð Performance, production, placing and compliance criteria, the Secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 1996, and conflicting national standards shall be withdrawn at the latest by September 1996. According to the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom
Contents Page Foreword
2
0
Introduction
3
1
Scope
3
2
Normative references
3
3
Definitions
3
3.1
Grouting
3
3.2
Post injection
3
3.3
Post grouting
3
4
Preliminary assessment
3
5
Suitability assessment
3
5.1
General
3
5.2
Materials assessment
3
6
Equipment
3
6.1
General
3
6.2
Screen
3
6.3
Storage reservoir
4
6.4
Pump
4
6.5
Hoses
4
6.6
Inlet connections
4
6.7
Standby equipment
4
7
Grouting procedure
4
7.1
General
4
7.2
Personnel
4
7.3
Inlets and outlets
4
7.4
Precautions before grouting
5
7.5
Temperature at grouting
5
7.6
Grouting operations
5
7.7
Precautions after grouting
5
7.8
Post injection
5
7.9
Post grouting
5
8
Quality control
6
8.1
General
6
8.2
Materials
6
8.3
Equipment
6
8.4
Grout
6
8.5
Grouting
6
© BSI
1997
Page 3 EN 446 : 1996
0 Introduction
4 Preliminary assessment
In post-tensioned prestressed concrete construction, the grouting of tendons is an important operation. The intention of this European Standard is to provide a specification for grouting, compliance with which will satisfy the recommendations in ENV 1992-1-1. The main function of grouting is to fill the sheaths or cable ducts as fully as possible with grout in order to provide protection to the tendons against corrosion and to provide bond between the tendons and the sheaths.
When undertaking this assessment care shall be taken to ensure that the materials used shall be those which are proposed for use. The materials shall be assessed in a laboratory both separately and in the combinations proposed for use. NOTE. The combination for cement and admixture(s) is sensitive and requires to be verified by preliminary assessment.
5 Suitability assessment 5.1 General
1 Scope This European Standard gives the procedures to be used in grouting of post-tensioned prestressed concrete with common grout. Other more specialized grouts may require additional specification to that given herein. This standard also covers preliminary assessment, suitability assessment and quality control procedures for grouts and their component materials. In this standard some values are specified which are marked (+). These values may be varied depending upon circumstances on site, provided that all the other requirements of this standard are met.
2 Normative references
Prior to the start of a job a proposal covering materials, equipment, grouting procedures and quality control shall be assessed by the competent authority. In certain circumstances, grouting trials on sheaths in representative forms of a construction may be required, e.g. when there is doubt about the ability to grout a particular sheath successfully. The properties of the grout, made with the materials, and using the plant and personnel proposed for use on site, shall be assessed for suitability for the intended purpose sufficiently in advance of grouting operations, to enable adjustments to be made in the use of the materials or plant or personnel. 5.2 Materials assessment
The materials assessment shall consist of the This European Standard incorporates by dated or preparation of the grout, made with the materials, and undated reference, provisions from other publications. using the plant and personnel proposed for use on site, These normative references are cited at the and the testing of it in accordance with clause 5 of appropriate places in the text and the publications are EN 447 and EN 445. The preparation shall be carried listed hereafter. For dated references, subsequent out under the conditions of temperature given in 7.5 of amendments to or revisions of any of these this standard or expected on site. publications apply to this European Standard only when incorporated in it by amendment or revision. For The above requirement may be waived where the results of earlier tests on grout made with materials undated references the latest edition of the publication and on plant sensibly identical to that proposed for referred to applies. use, are satisfactory. These test results shall date from EN 445 Grout for prestressing tendons Ð not more than two months before grouting. Test methods EN 447
Grout for prestressing tendons Ð Specification for common grout
ENV 1992-1-1 : 1991
Eurocode 2: Design of concrete structures Ð Part 1: General rules and rules for buildings
3 Definitions 3.1 grouting The injection into sheaths or tendon ducts with grout in a continuous operation. 3.2 post injection Complementary operation to grouting in order to replace air or water voids by grout in the ducts before the stiffening of the original grout. 3.3 post grouting Complementary operation to grouting in order to replace air or water voids by grout in the ducts after the stiffening of the original grout. © BSI
1997
6 Equipment 6.1 General
Grouting equipment shall consist of a mixer, a storage reservoir and a pump with all the necessary connection hoses, valves, measuring devices for water, cement and admixtures and testing equipment. The mixing equipment shall be capable of producing grout which possesses an even distribution of cement, an even dispersal of admixtures and a minimum presence of cement lumps and accords with the requirements of clause 5 of EN 447. 6.2 Screen
The grouting equipment shall contain a screen the openings of which shall be 2 mm maximum, through which the grout passes prior to its introduction into the storage reservoir.
Page 4 EN 446 : 1996
6.3 Storage reservoir
The mixer shall have an additional storage reservoir with an agitator to keep the grout moving continually before it is pumped into the duct. During interruptions in pumping, the grout shall be recirculated. The capacity of the mixer and the storage reservoir shall be such that the duct can be filled without interruption and at the required speed. 6.4 Pump
7 Grouting procedure 7.1 General
Prior to the start of grouting operations a proposal concerning grouting procedure shall be provided by the contractor and be assessed by the competent authority. The procedure shall ensure that the sheaths are properly filled with grout. In certain circumstances grouting trials on sheaths in representative forms of construction may be required, e.g. when there is a doubt about the ability to grout a particular sheath successfully.
The pump shall provide a continuous flow of grout and shall maintain a pressure of at least 1 MPa; it shall be NOTE. In some countries there are special requirements based on equipped with a pressure gauge. the current knowledge and experience gained with particular A pressure relief valve shall be incorporated to prevent grouts, equipment and grouting procedures. pressures above 2 MPa, or above any other value 7.2 Personnel determined by the chosen grouting procedure. Grouting operations shall be under the charge of a Limiting the grout pressure serves to: person with appropriate knowledge, training and ± prevent blow-outs of hoses, inlets and outlets; experience in production, testing and control systems ± prevent damage to the concrete structure; who shall be responsible for the production and injection of the grout. That person, or an appropriately ± protect the equipment and valves from damage; trained representative, shall be present during all ± protect the operators; grouting procedures and shall be responsible for all ± prevent segregation; safety precautions relating to the preparatory and ± control the grout flow. grouting operations. NOTE. In some countries there are special requirements regarding The use of compressed air for pumping shall not be standards of knowledge, training and experience for the different allowed. The pump shall be constructed in such a way tasks. as to prevent introduction of air, oil or other foreign substances into the grout. The capacity of the pump 7.3 Inlets and outlets shall be such that the duct can be adequately grouted. The position of the inlets and outlets is related to the The use of a pump with a variable output gives the type and geometry of the tendons as well as to the advantage that it can be adapted to the requirements of procedure for grouting and post grouting the ducts. ducts of different diameters. Inlets and outlets are normally placed at the following 6.5 Hoses locations: The diameter and rated pressure capacity of the grout ± inlets or outlets at the anchorages and couplers; hoses shall be compatible with the pump output, the ± outlets at or near the high points of the duct if the assumed maximum pressure and the length needed. difference between the highest and lowest point is Hose connectors shall normally not reduce the inside more than 0,5 m ((+) see clause 1); clear diameter available in the hoses. ± inlets at the lowest points of strongly inclined, 6.6 Inlet connections vertical or loop tendons and at specific points when grouting is to be carried out in stages. The grout hoses shall be tightly connected to the inlets of the duct. Clamps, bayonet or similar connections are recommended. Narrow openings, through which the grout must pass, shall be avoided, as the resulting pressure build-up can lead to danger of blockage. A pressure gauge shall normally be mounted at the grout inlet. NOTE. This should apply only where the hose length is greater than 30 m ((+) see clause 1).
In the event of sudden and abnormal pressure increases, an additional pressure gauge located at the grout inlet will indicate whether the reason for the pressure build-up lies within the tendon duct or in the grout hoses. 6.7 Stand-by equipment
The arrangements for the provision of stand-by equipment shall be decided in each case.
© BSI
1997
Page 5 EN 446 : 1996
7.4 Precautions before grouting
7.6 Grouting operations
NOTE. Sheaths should be grouted as soon as possible after the steel is tensioned. If the delay between inserting the tendons and grouting the sheaths is likely to permit corrosion of the tendons, consideration should be given to the possible use of protective soluble oils on the steel or dry air in the sheath. These operations should only proceed in accordance with the recommendations of the supplier of the system and it should be verified that their use will not have an adverse effect upon the tendons or the properties of the grout or its bond with the tendons. Some countries require the permission of authority for the use of some of these procedures.
Non-retarded grout shall be used within 30 min after mixing. The time limit is particularly important when the grout includes an expanding admixture.
Depending upon the tendon installation method, it may be necessary to ensure that the sheath, vents, inlets and outlets are capable of accepting injection of the grout. This shall be done by blowing through the system with dry air. Where there is water in the duct it shall be removed. Outlets at the lowest points and compressed air may be used for this purpose. The consequences of water remaining in the duct must be considered in order to choose the appropriate grouting procedure. The injection procedure shall ensure that sheaths are completely filled. Sheaths shall be grouted at a continuous and steady rate which shall be slow enough to prevent the segregation of the water from the grout at points where flow is restricted. Undulating ducts shall be grouted from the lowest point if the maximum deflection is more than 1,5 m ((+) see clause 1). 7.5 Temperature at grouting
Records shall be kept of the maximum and minimum air temperatures and the temperatures of the members to be grouted. Grout shall normally be injected when the air temperature and the temperature of the members to be grouted and the grout are within the ranges given in table 1. Table 1. Temperatures at grouting Temperature Ai r ÊC
Member
Grout
Minimum
5
5
10
Maximum
30
25
25
When any of the temperatures are less than the minimum or greater than the maximum given in table 1 special precautions valid in the place of grouting may be necessary which ensure that the sheaths can be grouted successfully. Tendons shall not be heated unless the general temperature of the members to be grouted is also raised by heating. Materials and equipment shall be completely free of snow, frost and ice. Notwithstanding the above requirements the temperature of freshly mixed grout shall not exceed 35 ÊC.
© BSI
1997
NOTE 1. The maximum length grouted in one operation should be not more than 50 m ((+) see clause 1) unless additional injection points are provided.
Normally the rate of grouting will vary from 5 to 15 m/min ((+) see clause 1). In general the ducts shall be grouted from the lowest inlet. Grouting shall continue until the fluidity of the grout flowing from the outlets is the same as the grout being injected to within the limits specified in 5.2 of EN 447. The outlets shall be successively closed as the filling of the duct progresses. After completion of grouting the unintended loss of grout from the duct shall be prevented. NOTE 2. This may be facilitated by maintaining a pressure of 0,5 MPa for 1 min.
The outlets at high points shall be opened shortly after grouting to allow bleed water to be displaced from the ducts. Vertical ducts shall be grouted from the lowest point using appropriate procedures. Attention shall be given to anchorages, couplers and high points especially in undulating tendons with difference in level more than 0,5 m ((+) see clause 1) and in strongly inclined or vertical tendons. 7.7 Precautions after grouting
Anchorages, vents and other metallic items that are to remain permanently in place shall be protected against corrosion and the ingress of water or other aggressive agents prevented. 7.8 Post injection
Post injection shall normally be carried out with freshly mixed grout. NOTE. If tendons consist of prestressing strands, pressure grouting may be applied. Directly after grouting, the post injection of grout into the duct should be continued at gradually increasing pressure to a maximum of not greater than 1 MPa. The anchorages should be sealed in such a way that the ends of strands protrude from the anchorages. If tendons consist of prestressing bars, wires or strands the post injection of grout may be carried out when most of the bleed water is separated in the duct and just before the grout stiffens. Pumping grout through inlets at various points may be needed in order to expel bleed water through outlets.
7.9 Post grouting
When the grout in ducts is already stiffened and control procedures at inlets and outlets show that water or air voids are formed, post grouting shall be carried out. These voids shall be filled with freshly mixed grout. In some cases vacuum grouting may be required.
Page 6 EN 446 : 1996
8 Quality control 8.1 General
Quality control consists of: ± internal control conducted by the contractor according to rules established by the client or by the competent authority; ± external control carried out by an independent organization to verify the results of internal control. Additional checking procedures may be required by the client or the competent authority.
8.4 Grout
Compliance shall be established when the grout complies with requirements given in clause 5 of EN 447. Consideration shall be given to the environmental conditions on site. The testing of the grout shall be carried out at least: ± prior to the start of a job (a minimum of 24 h); ± at the following minimum frequency of testing in the course of the grouting. Bleeding
It has to be checked that only constituent materials are used which comply with European Standards (see EN 447, clause 4) or with European Technical Approvals.
two tests per day. One sample is to be taken at the mixer and one sample at the duct outlet when the grout there has a satisfactory fluidity value.
Volume change
one test per day.
8.3 Equipment
Strength
one test per seven days or a minimum of two tests per job, whichever is greater.
Fluidity
three tests per 8 h.
8.2 Materials
The equipment shall be assessed as follows: ± checking and approving grouting equipment and qualifications of personnel by the competent authority; ± inspecting and approving grouting installations by the competent authority.
± when a significant change in the source of supply of materials occurs. 8.5 Grouting
The effectiveness of grouting shall be checked by appropriate means. At anchorages as well as at intermediate inlets and outlets visual control shall be carried out. In some cases a non-destructive examination of ducts may be required.
© BSI
1997
BS EN 446 : 1997
List of references
See national foreword.
© BSI
1997
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