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The term 'workability' has been replaced by the term 'consistence' and a series of consistence classes has been introduced.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) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Designated concrete |
Designated mix | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Designed concrete |
Designed mix | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Prescribed concrete |
Prescribed mix | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Standardized prescribed concrete |
Standard mix | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Proprietary concrete |
Example specification of Designed Concrete
^^ 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
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