Specification

Method of specifying

There are various methods of specifying concrete to BS 8500 (see Table 8). The most popular are designated and designed. BS 8500 also introduces a new method 'proprietary concrete'.

The specifier

Figures 1 and 2 show standard specification forms produced by the Quarry Products Association for designated and designed concretes8. Similar tables are included in the National Structural Concrete Specification9 (NSCS). In BS 8500 the 'specifier' is the person or body responsible for the final compilation of the technical requirements, called the specification, which is passed to the concrete producer. This will generally be the contractor, however, the designer will want to ensure their requirements are incorporated and this will normally be through their own specification for the works (e.g. with the NSCS). Figures 1 and 2 have been annotated to indicate which information is typically provided by the designer and contractor. The designer should require that any reported non-conformities are passed to them for assessment.

Consistence

The term 'workability' has been replaced by the term 'consistence' and a series of consistence classes has been introduced. Table 9 gives the slump and flow classes and the likely target slump/flow.

Chloride Class

Concrete that is to be prestressed, pre-tensioned or heat cured should normally be specified as chloride class Cl0,10. Reinforced concrete should be specified as class Cl0,40 except for concrete made with cement conforming to BS 402710 (SRPC), which should be specified as class Cl0,20. Post-tensioned elements in an internal building environment may also be specifed as class Cl0,10.

Table 6

Guidance on selecting designated concrete for reinforced concrete foundations

DC-Class

Appropriate Designated Concrete

DC-1

RC 25/30

DC-2

FND2

DC-2z

FND2z

DC-3

FND3

DC-3z

FND3z

DC-4

FND4

DC-4z

FND4z

DC-4m

Strength class for all FND concrete is C25/30.

Table 5

Selection of the DC-class and the number of Addition Protection Measures (APMs) where the hydrostatic head of groundwater is not more than five times the section width8, ^ ^ 4 e

ACEC-class

(Aggressive Chemical

DC-class

Intended working life

Environment for Concrete class)

At least 50 years

At least 100 years

AC-1s, AC-1

DC-1

DC-1

AC-2s, AC-Z

DC-2

DC-2

AC-2z

DC-2z

DC-2z

AC-3s

DC-3

DC-3

AC-3z

DC-3z

DC-3z

AC-3

DC-3

Refer to BS 8500

AC-4s

DC-4

DC-4

AC-4z

DC-4z

DC-4z

AC-4

DC-4

Refer to BS 8500

AC-4ms

DC-4m

DC4m

AC-4m

DC-4m

Refer to BS 8500

AC-5

DC-4f

DC-4f

AC-5z

DC-4zf

DC-4z/1 f

AC-5m

DC-4mf

DC-4mf

a Where the hydrostatic head of groundwater is greater than five times the section width, refer to BS 8500. b For guidance on precast products see Special Digest 12. c For structural performance outside these values refer to BS 8500. d For section widths < 140 mm refer to BS 8500.

e Where any surface attack is not acceptable e.g. with friction piles, refer to BS 8500. f This should include APM3 (surface protection), where practicable, as one of the APMs; refer to BS 8500.

Table 7

Factors affecting the abrasion resistance of concrete floors

Table 7

Factors affecting the abrasion resistance of concrete floors

Factor

Effect

Power floating

Power finishing and, in particular, repeated power trowelling is a significant factor in creating abrasion resistance, however, excessive repetitions of the process do not necessarily further enhance performance.

Curing

Prompt and efficient curing is essential in order to retain sufficient water in the surface zone to complete hydration and the development of concrete strength at and close to the surface.

Cement content

Cement content should not be less than 325 kg/m3. Cement contents above 360 kg/m3 are unlikely to enhance abrasion resistance and excessive cement content can impair the power finishing process.

Water/cement ratio

Water/cement ratio is of great importance. It should not exceed 0.55. Reducing to 0.50 is likely to increase abrasion resistance but lowering further is unlikely to give further enhancement.

Aggregates

Coarse aggregate usually has no direct effect on abrasion resistance, except in floors in very aggressive environments where the surface is expected to be worn away. Coarse and fine aggregates should not contain soft or friable materials.

Dry shake finishes

Dry shake finishes can be used to enhance the surface properties in high abrasion locations.

Figure 1

Example specification of Designated Concrete

Schedule for the specification requirements of designated concretes for use on contract Contract Title: New Office Contract period: June - Dec '04

BS 8500-1 reference

Requirement

Schedule

4.2.2a)

The concretes below shall be supplied as Designated Concretes in accordance with this specification and the relevant clauses of BS 8500-2A

4.2.2b) ©

Concrete designation

FND2z

RC25/30

RC32/40

©

Maximum aggregate size when other than 20 mm

10

(Ring the class required when other than the default classes of S3 for the GEN, FND and RC series and S2 for the PAV series. Use a separate column for different consistence with the same designated concrete) Other (specify)

S1, S2, S3, S4 F2, F3, F4, F5

S1,(S^S3, S4 F2, F3, F4, F5

S1,S2, S3, S4 F2, F3, F4, F5

S1, S2, S3, S4 F2, F3, F4, F5

4.2.3 QO

Additional requirements

-

-

-

Exchange of information

BS EN 206-1, 7.1

Total volume required Anticipated peak delivery rate Any access limitations

48 m3 6 m3/day

1200 m3 18 m3/hr

72 m3 6 m3/day

5.1a)

Intended method of placing, e.g. pumping, and finishing, e.g. power floating, the concrete

Skip + tamped

Pumping + float

Skip + tamped

5.1b)

Where identity testing is routine: Type of test

Volume of concrete in assessment Number of tests on this volume Whether a non-accredited laboratory will be used

N/A

N/A

N/A

©

Other information from the specifier to the producer

©

Information required from the producer

A There is no need to cite BS EN 206-1 as BS 8500-2 has a clause that requires conformity to BS EN 206-1.

Contractor specifies ^^ consistence, any additional requirements and completes exchange of information section

Red text

Example specification

Designer specifies concrete designation, maximum aggregate size and any additional requirements

Contractor specifies ^^ consistence, any additional requirements and completes exchange of information section

Red text

Example specification

Table 8

Methods of specifying concrete

Table 8

Methods of specifying concrete

BS 8500

BS 5328 (superseded by BS 8500 1 Dec 2003)

Designated concrete

Designated mix

Designed concrete

Designed mix

Prescribed concrete

Prescribed mix

Standardized prescribed concrete

Standard mix

Proprietary concrete

Example specification of Designed Concrete

Schedule for the specification requirements of designed concretes for use on contract Contract Title: New Office

Contract period: June - Dec '04

BS 8500-1 reference

Requirement

Schedule

4.3.2a)

The concretes below shall be supplied as designed concretes in accordance with this specification and the relevant clauses of BS 8500-2A

^^KDJ

Concrete reference, if any

Pads

Slab

Cols

4.3.2b) ©

Compressive strength class

C28/35

C25/30

C32/40

^HD]

432C) ©

For sulfate resisting concrete, design chemical class

DC-2z

DC-

DC-

DC-

KD

For other concretes, limiting values of composition: Maximum w/c ratio

Minimum cement/combination content, kg/m3

0.70 240

0.55 300

(delete those not permitted)

Other special property, e.g. white, low heat, +SR

(specify)

CEM 1, SRPC, IIA, IIB IIIA, IIIB, IVB

CEM 1, SRPC, IIA, IIB IIIA, x X

CEM 1, SRPC, IIA, IIB IIIA, Ix Ix

mump]

4.3.2e) ©

Maximum aggregate size, mm

20

20

10

^Hd]

4.3.2f)

Chloride class (ring the one required)

Prestressed or heat cured reinforced concrete Reinforced B

Unreinforced with no embedded metal

Cl 1,0

H

4.3.2g) & h) mmuD

For lightweight and heavyweight concrete, target density

4.3.2i)

Consistence (Ring the class required. Use separate columns for the same basic concretes with different consistence) Other (specify)

Slj^S3, S4 F2, F3, F4, F5

S1, S2(S^S4 F2, F3, F4, F5

SlfeS, S4 F2, F3, F4, F5

Note 2 ©

UKAS or equivalent accredited third party product conformity certification (delete if not required)

Yes

Yes

Yes

Yes

to n) 0©

Additional requirements

K3D

Exchange of information

BS EN

HHKC

Volume required Anticipated peak delivery rate Any access limitations

48 m3 6 m3/day

1200 m3 18 m3/hr

72 m3 6 m3/day

51a) ©

Intended method of placing, e.g. pumping, and finishing, e.g. power floating, the concrete

Skip + tamped

Pumping + float

Skip + tamped

5.1b)

Where identity testing is routine: Type of test

Volume of concrete in assessment

Number of tests on this volume

Whether a non-accredited laboratory will be used

N/A

N/A

N/A

5.1 & BS EN _ 206-1,7.1 ©

Other information from the specifier to the producer

5.2 & BS EN Ä 206-1,7.2 ©

Information required from the producer

A There is no need to cite BS EN 206-1 as BS 8500-2 has a clause that requires conformity to BS EN 206-1. B Where RC is ringed, the chloride class shall be Cl 0.40 except where SRPC is used. In this case the chloride class shall be Cl 0,20.

^^ Contractor specifies consistence, any additional requirements and completes exchange of information section

Red text

Example Specification

Designer specifies compressive strength class, design chemical class, maximum water/cement ratio, minimum cement content, cement or combination types (unless design chemical class is specified), maximum aggregate size, chloride class, target density (excluding normal weight concrete), requirement for third party product conformity certification (recommended) and any additional requirements

^^ Contractor specifies consistence, any additional requirements and completes exchange of information section

Red text

Example Specification

Table 9a

Consistence slump classes and likely target values

Table 9a

Consistence slump classes and likely target values

Slump class

Target slump (mm)

S1

20

S2

70

S3

130

S4

190

Table 9b

Consistence flow classes and likely target values

Flow class

Target flow (mm)

F2

380

F3

450

F4

520

F5

Under BS 8500, the concrete producer is now required to follow a formal procedure called 'conformity' to verify that the concrete is in accordance with the specification. It is, therefore, recommended that the concrete supplier should have third party certification. Where this is not adopted, the specifier is advised to adopt adequate identity testing to ensure the concrete is as specified.

Identity testing

The specifier is responsible for organising any identity testing, which is in all but in name acceptance testing. Identity testing can include strength, consistence and air content. There are a number of situations where it is recommended:

■ where the producer does not hold third party certification

■ for critical elements, e.g. high strength columns

■ for spot checks on the producer.

Exchange of information

To enable the concrete producer to design and produce a suitable concrete, certain information must be provided in addition to the specification, e.g. where the concrete needs to be pumped or a high quality finish is required.

References

1 BRITISH STANDARDS INSTITUTION. BS 8500: Concrete - Complementary British Standard to BS EN 206-1. BS1, 2006.

2 BUILDING RESEARCH ESTABLISHMENT. BRESpecial Digest 1 - Concrete in aggressive ground (3rd edition). BRE, 2005.

3 BRITISH STANDARDS INSTITUTION. BS 5328: Concrete, BSI. (Withdrawn by BSI on 1 December 2003).

4 BRITISH STANDARDS INSTITUTION. BS EN 1992, Eerocode 2: Design of concrete structures. BSI (4 parts).

5 BRITISH STANDARDS INSTITUTION. BS 8110-1: The structural use of concrete - Part 1:Code of practice for design and construction. BSI, 1997.

6 BRITISH STANDARDS INSTITUTION. BS 8204-2: Screeds, bases and in-situ floorings, Part 2: Concrete wearing surfaces - Code of practice. BSI, 1999.

7 THE CONCRETE SOCIETY. Technical report 34: Concrete industrial ground floors. The Concrete Society, 2003.

8 QUARRY PRODUCTS ASSOCIATION. Visit the Webpage www.qpa.ors/pro_rea.

9 CONSTRUCT. National structural concrete specification for building construction. Construct, 2004.

10 BRITISH STANDARDS INSTITUTION. BS 4027: Specification for sulfate-resisting Portland cement. BSI, 1996.

For more information on Eurocode 2 visit www.eurocode2.info.

For further questions relating to Eurocode 2 or the design, use and performance of concrete, contact the free National Helpline 0845 812 0000 [email protected]

Published by The Concrete Centre

Riverside House, 4 Meadows Business Park,

Station Approach, Blackwater, Camberley,

Surrey GU17 9AB

www.concretecentre.com

The Concrete Centre™

Ref: TCC/03/30 ISBN 1-904818-50-1

Published April 2007. Reprinted December 2007 First published as How to use BS 8500 with BS 8110, March 2005

© The Concrete Centre-

All advice or information from The Concrete Centre is intended for use in the UK only by those who will evaluate the significance and limitations of its contents and take responsibility for its use and application. No liability (including that for negligence) for any loss resulting from such advice or information is accepted by The Concrete Centre or its subcontractors, suppliers or advisors. Readers should note that publications from The Concrete Centre are subject to revision from time to time and they should therefore ensure that they are in possession of the latest version. This publication has been produced following a contract placed by the Department for Trade and Industry (DTI); the views expressed are not necessarily those of the DTI.

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Responses

  • kieron
    What replaces class f2 surface finish in eurocode?
    6 years ago
  • timo kokkonen
    What is DC2z sulfate resisting concrete?
    6 years ago
  • allison
    What strength is FND3 concrete?
    6 years ago
  • Toni
    What is DC3Z CONCRETE?
    1 year ago
  • leon
    What are designated concrete?
    8 months ago
  • Christina
    What is the eurocode specification for eurocode?
    8 days ago

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