SIST EN 1538:2011+A1:2015
(Main)Execution of special geotechnical work - Diaphragm walls
Execution of special geotechnical work - Diaphragm walls
This European Standard establishes general principles for the execution of diaphragm walls as either retaining walls or cut-off walls.
NOTE 1 This standard covers only structures constructed in a trench excavated with a support fluid or in dry conditions, where soil is removed and replaced by concrete or slurry and with wall thickness B ≥ 40 cm.
NOTE 2 Diaphragm walls can be permanent or temporary structures.
NOTE 3 The following types of structure are considered:
a) retaining walls: usually constructed to support the sides of an excavation in the ground. They include:
1) cast in situ concrete diaphragm walls;
2) precast concrete diaphragm walls;
3) reinforced slurry walls;
b) cut-off walls: usually constructed to prevent migration of groundwater, clear or polluted, or of other contaminants present in the ground. They include:
1) slurry walls (possibly with membranes or sheet piles);
2) plastic concrete walls.
NOTE 4 Walls formed shallow vertical trenches (typically excavations with a ratio of depth over thickness D/B < 5 or D < 5 m) are not covered by this standard.
Ausführung von Arbeiten im Spezialtiefbau - Schlitzwände
Diese Europäische Norm enthält die allgemeinen Grundlagen für die Ausführung von Schlitzwänden als Stützwände und als Dichtwände.
ANMERKUNG 1 Diese Norm gilt nur für solche Schlitzwände, die in einem im Baugrund ausgehobenen Schlitz unter Verwendung einer Stützflüssigkeit oder unter trockenen Bedingungen durch Bodenaushub und Ersatz des Bodens durch Beton oder selbsterhärtende Suspension hergestellt werden sowie eine Dicke B von ≥ 40 cm aufweisen.
ANMERKUNG 2 Schlitzwände können bleibende oder vorübergehende Bauwerke sein.
ANMERKUNG 3 Die folgenden Ausführungsarten werden behandelt:
a) Schlitzwände als Stützwände: diese werden üblicherweise hergestellt, um die seitlichen Wände einer Baugrube zu stützen. Sie umfassen:
1) Ortbetonschlitzwände;
2) Fertigteilschlitzwände;
3) bewehrte Einphasenschlitzwände;
b) Dichtwände: diese werden üblicherweise hergestellt, um die Bewegung von sauberem oder verunreinigtem Grundwasser oder von anderen Kontaminationen im Boden zu verhindern. Sie umfassen:
1) Einphasenschlitzwände (gegebenenfalls mit Dichtungsbahnen oder Spundwänden);
2) Tonbetonschlitzwände.
ANMERKUNG 4 Wände, die in vertikalen Schlitzen geringer Tiefe (typischerweise mit einem Verhältnis Tiefe/Breite D/B < 5 oder einer Tiefe D < 5 m) hergestellt werden, sind nicht Gegenstand dieser Norm.
Exécution des travaux géotechniques spéciaux - Parois moulées
La présente Norme européenne établit les principes généraux pour l'exécution des parois moulées de soutènement ou d'étanchéité.
NOTE 1 Cette norme traite uniquement des structures construites dans une tranchée excavée avec un fluide stabilisateur ou en conditions sèches, dans lesquelles le sol est retiré et remplacé par du béton ou du coulis et ayant une épaisseur de paroi B ≥ 40 cm.
NOTE 2 Les parois moulées peuvent être des ouvrages provisoires ou permanents.
NOTE 3 Les différents types de structures suivants sont examinés :
a) parois de soutènement : ouvrages généralement réalisés pour soutenir les parois d’une excavation dans un site ; elles comprennent :
1) les parois moulées en béton ;
2) les parois préfabriquées en béton ;
3) les parois en coulis armé ;
b) parois d’étanchéité : ouvrages généralement réalisés pour s’opposer au cheminement dans le sol d’eau claire ou polluée, ou de tout autre contaminant présent dans le sol ; elles comprennent :
1) les parois en coulis (avec éventuellement des membranes ou des palplanches) ;
2) les parois en béton plastique.
NOTE 4 Les parois formées par des tranchées verticales peu profondes (généralement des excavations avec un rapport profondeur/épaisseur D/B < 5 ou D < 5 m) ne sont pas couvertes par la présente norme.
Izvedba posebnih geotehničnih del - Diafragme
Ta evropski standard določa splošna načela za izvedbo diafragem kot opornih ali ločevalnih zidov.
OPOMBA 1 Ta standard zajema samo strukture, zgrajene v jarku, izkopanem s podporno tekočino ali pri suhih pogojih, kjer je zemlja odstranjena in zamenjana z betonom ali brozgo, ter z debelino zidu B ≥ 40 cm.
OPOMBA 2 Stena diafragme je lahko stalna ali začasna struktura.
OPOMBA 3 Upoštevani so naslednji tipi struktur:
a) oporni zidovi: običajno zgrajeni za oporo strani izkopa v tleh. Zajemajo:
1) na kraju vlite betonske diafragme;
2) montažne betonske diafragme;
3) armirane zidove iz brozge;
b) ločevalne zidove: običajno zgrajeni za preprečevanje pretoka podtalnice, čiste ali onesnažene, ali drugih onesnaževal, prisotnih v tleh. Zajemajo:
1) zidove iz brozge (morebiti z membranami ali zagatnimi piloti);
2) zidove iz plastičnega betona;
OPOMBA 4 Zidovi, ki tvorijo plitve navpične jarke (običajno izkope z razmerjem med globino in debelino D/B < 5 ali D < 5 m) niso zajeti v tem standardu.
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Ausführung von Arbeiten im Spezialtiefbau - SchlitzwändeExécution des travaux géotechniques spéciaux - Parois mouléesExecution of special geotechnical work - Diaphragm walls93.020Zemeljska dela. Izkopavanja. Gradnja temeljev. Dela pod zemljoEarthworks. Excavations. Foundation construction. Underground worksICS:Ta slovenski standard je istoveten z:EN 1538:2010+A1:2015SIST EN 1538:2011+A1:2015en,fr,de01-september-2015SIST EN 1538:2011+A1:2015SLOVENSKI
STANDARDSIST EN 1538:20111DGRPHãþD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 1538:2010+A1
June 2015 ICS 93.020 Supersedes EN 1538:2010English Version
Execution of special geotechnical work - Diaphragm walls
Exécution des travaux géotechniques spéciaux - Parois moulées
Ausführung von Arbeiten im Spezialtiefbau - SchlitzwändeThis European Standard was approved by CEN on 2 July 2010 and includes Amendment 1 approved by CEN on 17 April 2015.
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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2015 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 1538:2010+A1:2015 ESIST EN 1538:2011+A1:2015
Glossary . 34 Annex B (informative)
Control schedules during the execution . 36 Annex C (informative)
Sample concreting record forms for diaphragm walls . 42 Annex D (informative)
Degree of obligation of the provisions . 43 Bibliography . 47
Bored piles. The design, planning and execution of retaining and cut-off diaphragm walls call for experience and knowledge in this specialised field. The execution phase requires skilled and qualified personnel and the present standard cannot replace the expertise of specialist contractors. The document has been prepared to stand alongside EN 1997-1, Eurocode 7: Geotechnical design
Part 1: General rules and EN 1997-2, Eurocode 7: Geotechnical design
Part 2: Ground investigation and testing. This standard expands on design only where necessary (e.g. the detailing of reinforcement) and provides full coverage of the construction and supervision requirements. #The amendment became necessary to accord the Standard EN 1538:2010 with EN 206:2013, Concrete – Specification, performance, production and conformity. EN 206:2013 has been revised to contain also the specific requirements for concrete for applications for special geotechnical works, making redundant respective provisions in EN 1538 (e.g. 6.1, 6.3 and 8.8). Full according with EN 13670, Execution of concrete structures is however still pending. EN 1538:2010+A1:2015 therefore still contains specific requirements for bored piles as a concrete structure, such as the detailing of the reinforcement, the concrete placement and the supervision of concreting process which are complementing the provisions of EN 13670.
In addition, some editorial corrections were made in this amended Standard." According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
NOTE 1 This standard covers only structures constructed in a trench excavated with a support fluid or in dry conditions, where soil is removed and replaced by concrete or slurry and with wall thickness B ≥ 40 cm.
NOTE 2 Diaphragm walls can be permanent or temporary structures.
NOTE 3 The following types of structure are considered: a) retaining walls: usually constructed to support the sides of an excavation in the ground. They include: 1) cast in situ concrete diaphragm walls; 2) precast concrete diaphragm walls; 3) reinforced slurry walls; b) cut-off walls: usually constructed to prevent migration of groundwater, clear or polluted, or of other contaminants present in the ground. They include:
1) slurry walls (possibly with membranes or sheet piles); 2) plastic concrete walls. NOTE 4 Walls formed shallow vertical trenches (typically excavations with a ratio of depth over thickness D/B < 5 or D < 5 m) are not covered by this standard.
Key
1 Wall thickness (B) 7 Guide-wall 2 Horizontal length of reinforcement cage 8 Cut off level 3 Cage width 9 Vertical length of reinforcement cage 4 Length of panel 10 Reinforcement cage 5 !Working platform level" 11 Depth of excavation (D) 6 Casting level 12 Concave portion of curved joints Figure 1 — Geometry of a panel SIST EN 1538:2011+A1:2015
! " Key
P Primary S Secondary 1 Starter 2 Intermediate 3 Closure Figure 2 — Schematic examples of different types of panels and joints (plan view) 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
!deleted text" !EN 206:2013, Concrete
Specification, performance, production and conformity" EN 791, Drill rigs
Safety !deleted text" EN 1990, Eurocode
Basis of structural design EN 1991 (all parts), Eurocode 1: Actions on structures EN 1992 (all parts), Eurocode 2: Design of concrete structures EN 1997-1, Eurocode 7: Geotechnical design
Part 1: General rules EN 1997-2, Eurocode 7
Geotechnical design
Part 2: Ground investigation and testing EN 1998 (all parts), Eurocode 8: Design of structures for earthquake resistance SIST EN 1538:2011+A1:2015
Part 2: Technical delivery conditions for non-alloy structural steels EN 10080, Steel for the reinforcement of concrete
Weldable reinforcing steel
General EN 10210 (all parts), Hot finished structural hollow sections of non-alloy and fine grain steels EN 10219 (all parts), Cold formed welded structural hollow sections of non-alloy and fine grain steels EN 10248 (all parts), Hot rolled sheet piling of non alloy steels EN 10249 (all parts), Cold formed sheet piling of non alloy steels !deleted text" EN 13670, Execution of concrete structures 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1
cast in situ concrete diaphragm wall fr paroi moulée en béton de Ortbetonschlitzwand wall made of plain or reinforced concrete, which is constructed in a trench excavated in the ground
NOTE The excavation is carried out in discrete length to form panels and the concrete is placed through tremie pipes immersed in the fresh concrete. In some cases the excavation and the concreting may be carried out in dry conditions. 3.2
plastic concrete wall fr paroi moulée en béton plastique de Tonbetonschlitzwand wall made of plastic concrete, which is constructed in a trench in the ground
NOTE The excavation is carried out in panels and the concrete is placed through tremie pipes most of the time immersed in a support fluid. In some cases the excavation and the concreting may be carried out in dry conditions. 3.3
precast concrete diaphragm wall fr paroi préfabriquée en béton de Fertigteilschlitzwand wall made of precast elements which are lowered into a trench excavated in the ground containing a hardening slurry 3.4
reinforced slurry wall fr paroi moulée en coulis armé de bewehrte Einphasenschlitzwand wall made from a hardening slurry reinforced by steel beams, steel mesh or other suitable elements 3.5
slurry wall fr paroi moulée en coulis de Einphasenschlitzwand wall made from a hardening slurry
NOTE In most cases, the excavation is carried out using a hardening slurry as the support fluid. Sealing elements such as membranes or sheetpiles may be inserted. SIST EN 1538:2011+A1:2015
plastic concrete fr béton plastique de Tonbeton low strength, low Young's modulus concrete capable of sustaining larger strains than normal concrete NOTE It usually consists of low cement content concrete mixed at a high water cement ratio. It may include bentonite and/or other clay materials and/or other materials such as pulverized fuel ash (PFA) and admixtures. 3.7
hardening slurry fr coulis autodurcissant de selbsterhärtende Suspension slurry which hardens with time
NOTE The slurry is a suspension which contains cement or another binder, and additional materials such as clay (bentonite), ground granulated blast furnace slag (GGBFS) or pulverized fuel ash (PFA), fillers, sand and admixtures. Hardening slurries are generally used in the precast concrete diaphragm wall technique and for slurry walls. They serve as support fluid during excavation, and, together with the fines from the natural ground, form the final, hardened material.
3.8
guide-walls fr murettes-guides de Leitwände shallow depth, parallel temporary walls which are used to provide a guide for the excavating tool, to secure the sides of the trench against collapse at the trench top close to platform level, and to support and to facilitate the positioning of the reinforcement 3.9
panel
fr panneau de Schlitzwandelement !/ Schlitzwandlamelle" section of a diaphragm wall which is concreted as a single unit
NOTE A diaphragm panel may be linear, T-shaped, L-shaped, or of other configuration. 3.10
support fluid fr fluide stabilisateur de Stützflüssigkeit fluid used during excavation to support the sides of the trench
NOTE It is usually a bentonite suspension, a polymer solution or a hardening slurry. 3.11 concreting pipe fr colonne de bétonnage de Betonierrohr
metal pipe comprising several joined lengths, surmounted by a hopper or chute for concreting under dry conditions
3.12 tremie pipe fr tube plongeur de Kontraktorrohr concreting pipe, with watertight joints for submerged concrete placement SIST EN 1538:2011+A1:2015
cover fr enrobage de Betonüberdeckung distance between the outside of the reinforcement cage and the nearest concrete surface NOTE The nearest concrete surface considered is the nearest excavated face as formed by the excavation tool. 3.14
execution specification
fr specifications d'exécution de bautechnische Unterlagen set of documents covering all drawings, technical data and requirements necessary for the execution of a particular project NOTE The execution specification is not one document but signifies the total sum of documents required for the execution of the work as provided by the designer to the constructor. It includes the project specification prepared to supplement and qualify the requirements of this European Standard, as well as referring the national provisions relevant in the place of use. 3.15
project specification
fr spécifications de l'ouvrage de Projektspezifikationen project specific document describing the requirements applicable for the particular project 4 Information needed for the execution of the work 4.1 General 4.1.1 Prior to the execution of the work, all necessary information shall be provided.
4.1.2 This information should include: any legal or statutory restrictions; the location of main grid lines for setting out; the conditions of structures, roads, services, etc. adjacent to the work, including any necessary surveys;
a suitable quality management system, including supervision, monitoring and testing. 4.1.3 The information regarding the site conditions shall cover, where relevant: the geometry of the site (boundary conditions, topography, access, slopes, headroom restrictions, etc.); the existing underground structures, services, known contaminations, and archeological constraints; the environmental restrictions, including noise, vibration, pollution; the future or ongoing activities such as dewatering, tunnelling, deep excavations. 4.2 Special features 4.2.1 The special features shall cover, where relevant: execution specifications (see 3.14); previous use of the site; SIST EN 1538:2011+A1:2015
presence of headroom restrictions; presence of archeological remains; presence of natural and/or man made cavities (mines, etc.); !presence of contaminated ground;" any specific requirements for the diaphragm wall, in particular those pertaining to tolerances, quality of materials, watertightness, and type of joints; where available, previous experience with diaphragm walls or underground works on or adjacent to the site; for slurry walls, permeability, strength and deformation properties of the wall material; proposed adjacent enabling or advance works such as underpinning, pre-treatment of soil, dewatering; diaphragm wall function (i.e. end bearing, retaining wall, cut off wall, environmental barrier, etc.). 4.2.2 Necessity, extent, procedure and content for any survey of the conditions of structures, roads, services, etc. adjacent to the works area shall be established.
4.2.3 The survey shall be carried out and be available prior to the commencement of the works and its conclusions shall be used to define the threshold values for any movement which may affect adjacent structures by the works area constructions. 4.2.4 Any additional or deviating requirements falling within the permissions given in this European Standard shall be established and agreed before the commencement of the works and the quality control system shall be suitably amended. NOTE Such additional or deviating requirements can be: — reduced or increased geometrical construction deviations; — application of different or varying construction materials; — precast concrete elements; — special anchorage or doweling of diaphragm walls to underlying rock; — special reinforcement as the use of steel tubes or sections or of steel fibres; — grouting of diaphragm walls shafts or bases; — trimming of diaphragm walls heads by mechanical equipment. 5 Geotechnical investigation
5.1 General
5.1.1 The geotechnical investigation shall fulfil the requirements of EN 1997 (all parts). SIST EN 1538:2011+A1:2015
NOTE 2 Relevant experience of the execution of comparable foundation works under similar conditions and/or in the vicinity of the site has to be taken into account when determining the extent of site investigation (reference to relevant experience is permitted if appropriate means of verification are taken e.g. by penetration, pressuremeter or other tests).
NOTE 3 Guidance is given in EN 1997-2 on the depth and the contents of investigations. 5.1.2 The geotechnical investigation report shall be available in time, to allow for reliable design and execution of the diaphragm walls (e.g. the choice of method of execution). 5.1.3 The geotechnical investigation shall be checked to see whether if it is sufficient for the design and execution of the diaphragm walls.
5.1.4 If the geotechnical investigations are not sufficient, a supplementary investigation shall be conducted. 5.2 Specific requirements 5.2.1 Particular attention shall be paid to the following aspects, which are relevant to the execution of diaphragm walls:
the ground level at any point of investigation or testing relative to the recognised national datum or to a fixed reference chart datum; piezometric levels of all water-tables and permeability of the soils; presence of coarse, highly permeable soils or cavities (natural or artificial), which can cause sudden losses of support fluid and instability of the trench, and thus can require special measures; presence, strength and deformation characteristics of soft soils, such as very soft clay or peat, which can cause difficulties during excavation or concreting (deformation or instability); presence of boulders or obstructions which can cause difficulties during excavation and, an assessment of their size and frequency, when applicable; presence, position, strength of hard rock or other hard materials which can cause difficulties during excavation and may require the use of special tools; detrimental chemistry of groundwater, soil and rock, and water temperatures if required; detrimental chemistry of waste materials; presence of pretreated soil, which can have an adverse effect during excavation; mining beneath the site;
site stability problems (slope stability for instance). 5.2.2 The piezometric levels of the various water-tables existing on the site shall be monitored separately and over a sufficient period of time to estimate the highest piezometric levels which can occur during construction of the diaphragm wall.
5.2.3 Particular attention shall be paid to artesian conditions. 5.2.4 The strength of the soils and rocks shall be determined by laboratory tests and/or in situ tests over the full depth of the diaphragm wall and to a certain depth below the base depending on the nature of the ground and the function of the wall. SIST EN 1538:2011+A1:2015
5.2.6 When diaphragm walls are required to reach or penetrate into rock, the properties of the rock, including the degree of weathering and the extent and direction of fissuring, shall be determined. 6 Materials and products
6.1 Constituents 6.1.1 General 6.1.1.1 The constituents shall meet the requirements set in the respective European Standards, the provisions valid in the place of use and the provisions given in the project specification.
6.1.1.2
The sources of supply of constituents shall be documented and shall not be changed without prior notification. 6.1.2 Bentonite 6.1.2.1 A distinction should be made between calcium bentonite, natural sodium bentonite and activated bentonite, which is a sodium bentonite produced from natural calcium bentonite by ion exchange. NOTE 1 Bentonite is a clay containing mainly the mineral montmorillonite.
NOTE 2 Bentonite is used in support fluids, either as a pure bentonite suspension or as an addition to polymer solutions. It is also used as a constituent part of hardening slurries and of plastic concrete.
6.1.2.2 Bentonite used in bentonite suspensions shall not contain harmful constituents in such quantities as can be detrimental to reinforcement or concrete. 6.1.2.3 The chemical and mineralogical composition of the bentonite shall be supplied. 6.1.3 Polymers Polymers can be used as sole constituent in supporting fluids or as additives to enhance rheological effectiveness.
NOTE 1 Polymers are materials formed of molecules from chained monomeric units.
NOTE 2
There are different types of polymers ranging from natural gums to specially tailored blends of synthetic products. 6.1.4 Cement ! 6.1.4.1 Cements for diaphragm walls are listed in EN 206:2013, Annex D.
6.1.4.2 The use of CEM II or CEM III cement or the partial replacement of CEM I cement by type II additions is recommended because they have been shown to have beneficial effects on concrete, such as:
improved workability;
reduced heat generation during setting;
improved durability; and SIST EN 1538:2011+A1:2015
NOTE 2 Bleeding is less likely to be significant with cements with fineness of grind (Blaine) of 3 800 cm2/g or more." ! 6.1.5 Aggregates Aggregates shall comply with EN 206:2013, Annex D. 6.1.6 Water Mixing water shall comply with EN 206:2013.
6.1.7 Additions The use of additions shall comply with EN 206:2013. 6.1.8 Admixtures Admixtures shall comply with EN 206:2013." 6.2 Support fluids 6.2.1 Bentonite suspensions 6.2.1.1
A bentonite suspension shall be prepared with either natural or activated sodium bentonite. 6.2.1.2 In certain cases, e.g. when the density of the suspension has to be increased, suitable inert materials may be added. 6.2.1.3
Other than in exceptional circumstances, (see notes) the fresh bentonite suspension shall meet the conditions shown in Table 1 and the "re-use" or "before-concreting" bentonite suspension shall meet the conditions shown in Table 2. NOTE 1 Special circumstances are for example: — soils or rock with high permeability or cavities where loss of bentonite can occur; — high piezometric ground water levels (confined or artesian conditions); — very loose sand or soft soils (typically with qc < 300 kPa or Cu < 15 kPa); — salt water conditions. NOTE 2 A bentonite suspension with sufficient shear strength can be required, e.g. in order to reduce penetration into the ground. 6.2.1.4 At the stage "before concreting", an upper limit value between 4 % and 6 % for sand content may be used in special cases (e.g. unreinforced walls).
Values Density in g/cm3 < 1,10 Marsh valueb in s 32 to 50 Fluid lossc in cm3 < 30 pH 7 to 11 Filter cake in mm < 3 a See Table 2 , Footnotes a to c for the test procedures. b The Marsh value is the time required for a volume of 946 ml to flow through the orifice of the cone. A volume of 1 000 ml may be used, but in this case, the Marsh value should be adjusted. c The duration of the fluid loss test may be reduced to 7,5 min for routine control tests. However, in this case, the values for fluid loss and filter cake shall be adjusted. The fluid loss for the 7,5 min test will be approximately half of the value obtained in the 30 min test.
Table 2 — Characteristics for bentonite suspensions Propertya
Stages re-use
before concreting Density in g/cm3 < 1,25 < 1,15 Marsh valueb in s 32 to 60 32 to 50 Fluid lossc in cm3 < 50 not applicable pHd
7 to 12 not applicable Sand content in % volume
not applicable < 4 Filter cake in mm < 6 not applicable a The Marsh value, the fluid loss, the sand content and the filter cake can be measured, for example, using the tests described in EN ISO 13500. b The Marsh value is the time required for a volume of 946 ml to flow through the orifice of the cone. A volume of 1 000 ml may be used, but in this case, the Marsh value should be adjusted. c The duration of the fluid loss test may be reduced to 7,5 min for routine control tests. However, in this case, the values for fluid loss and filter cake shall be adjusted. The fluid loss for the 7,5 min test will be approximately half of the value obtained in the 30 min test. d Indicative values. 6.2.2 Polymer solutions 6.2.2.1 Polymers may be designed to work in conjunction with bentonite or used as stand alone support fluids.
6.2.2.2 Polymer use shall be based on full-scale trial trenches on the site or on the basis of comparable experience in similar geotechnical conditions.
Where respective European Standards are not available the suspensions shall be prepared, maintained and controlled in accordance with respective national standards or requirements, or where these do not apply, to the manufacturer’s instructions. 6.2.3 Fresh hardening slurries 6.2.3.1 Fresh hardening slurries as supporting fluids shall be suitable to ensure the support of the excavated trench during excavation process. 6.2.3.2 A hardening slurry may be prepared with calcium bentonite or activated sodium bentonite as well as cementitious binders. 6.2.3.3 Admixtures may be used to adjust the setting time of the slurry and its consistency during excavation and during any subsequent insertion of elements.
6.2.3.4 The possible effects of temperature and chemical components of the soil and groundwater on the setting time shall be taken into account when admixtures are selected.
6.3 Concrete ! 6.3.1 General 6.3.1.1 Concrete shall comply with EN 206:2013. 6.3.1.2 Cast in situ concrete shall be composed to minimize segregation during placing, to flow easily around the reinforcement, and when set, to provide a dense and low permeability material.
6.3.1.3 The concrete shall comply with the requirements related to strength and durability in the hardened state as well as with the requirements related to consistency in the fresh state. 6.3.2 Aggregates Aggregates shall comply with EN 206:2013. 6.3.3 Cement contents The minimum cement contents shall conform with EN 206:2013, Table D.2. 6.3.4 Water/cement ratio The water/cement ratio shall comply with EN 206:2013. 6.3.5 Admixtures Admixtures used shall comply with EN 206:2013. NOTE 1 The admixtures commonly used for concreting are:
— water reducing/plasticizing; — high range water reducing/super-plasticizing; and — set retarding. NOTE 2 Admixtures are used:
— to minimize bleeding and avoid honeycombing or segregation that might otherwise result from a high water content; — to prolong the workability as required for the duration of the placement to cater for any interruptions in the placement process. NOTE 3 Inappropriate application of admixtures can result into damages.
6.3.6 Fresh concrete Concrete shall comply with EN 206:2013, Annex D." !deleted text" 6.3.7 Sampling and testing on site
6.3.7.1 All sampling and testing of fresh concrete on site shall comply with EN 13670 and the execution specification.
NOTE 1 Conformity testing to confirm that the properties of the concrete comply with the specification is part of producers obligations (see !EN 206:2013"). NOTE 2 Additional sampling can be specified in special cases at the point of delivery, just before placing, to check the properties of the concrete (e.g. in case of high stresses or when the concrete is not produced in a certified quality assurance system).
6.3.7.2 The minimum number of cylinder or cube specimens in a sample is three. 6.3.7.3 When the concrete is not produced in a certified quality assurance system, sampling and compressive strength testing shall be carried out.
6.3.7.4
Where the concrete is produced in a continuous and certified quality assurance system, deviating requirements from those of non certified quality assurance system for concrete sampling on site may be specified. 6.3.7.5 The frequency of testing of consistence, concrete temperature and workability time shall comply with the execution specifications. NOTE
Guidance is given in Annex B in Tables B.1 to B.5.
6.3.7.6 A full record of all tests carried out on the concrete shall be kept and results shall be noted in the concreting record. 6.4 Plastic concrete
Plastic concrete shall be produced in accordance with the execution specification in order to obtain the specified deformability and permeability, together with adequate workability and strength.
NOTE 1 Plastic concrete is used for cut-off walls when, in addition to low permeability, high deformability is required.
NOTE 2 Their constituent parts are: — fine grain material (e.g. silt, clay or bentonite); — cement or another binder; — well-graded aggregates; SIST EN 1538:2011+A1:2015
For plastic concrete it can be more suitable to specify the compressive strength not at 28 days but at a later age more representative of the long-term performance of the structure (see EN 206:2013, 5.5.1.2(3)). Knowledge of the long term strength and deformability can be necessary." 6.5 Hardening slurry 6.5.1 Hardening slurry shall be produced in accordance with the execution specification in order to obtain the specified deformability and permeability, together with adequate workability and strength.
NOTE 1 Hardening slurries are used for precast concrete diaphragm walls and for cut-off walls when, in addition to low permeability, high deformability is required.
NOTE 2 Their constituent parts are: — fine grain material (e.g. silt, clay or bentonite); — cement or another binder; — water; — and possibly additions and admixtures. NOTE 3
These constituents can be delivered as pre-mix products. !NOTE 4
For hardening slurry it can be more suitable to specify the compressive strength not at 28 days but at an earlier or later age more represen
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