I Specification ©curtins.

consuiting

Structural Concrete

Grenfell Tower

LO1212-SPEC-003

25 t h October 2013

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Contents (Ricurtins consulting

SECTION 1 General

SECTION 2 Materials

Cement 2.2 Aggregates Z.o Additives 2.4 Reinforcement

SECTION 3 Concrete and Concrete Finish

SECTION 4 Testing

SECTION 5 Precast and/or Pre-stressed Concrete Floors, Stairs & Roofs

5.1 Definitions 5.2 Design of Units 5.3 Trimming Brackets to Openings 5.4 Information Required 5.5 Detailing of Units 5.6 Erection

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1.0 General © g f f l b n g

1.1 All concrete work shall be constructed strictly in accordance with the drawings and schedules provided by the Engineer and the Architect, with this Specification and with Part 1 of the National Structural Concrete Specification for Building Construction (NSCS). Where there is conflict between the NSCS and Curtins drawings or Specification, Curtins drawings or Specification shall take precedence.

1.2 Unless specifically instructed otherwise, either in this Specification or on the drawings, concrete work shall be strictly in accordance with:

BS 8000-2.2 Workmanship on Building Sites. Code of Practice for Concrete Work. Site Work With In Situ and Precast Concrete.

Eurocode 2 Design of Concrete Structures - ail relevant parts.

UK NA to United Kingdom National Annex to Eurocode 2; Design of Concrete Structures. Eurocode 2

BS 8500-1 Concrete - Complimentary British Standard to BS EN 206-1. Part 1; Method of Specifying and Guidance for the Specifier.

BS 8500-2 Concrete - Complimentary British Standard to BS EN 206-1. Part 2: Specification for Constituent Materials and Concrete.

BS EN 206-1 Concrete - Part 1: Specification, Performance, Production and Conformity.

1.3 The General Contractor shall be fully responsible for the cost, design and safety of all falsework, formwork, scaffolding and other temporary works.

1.4 Tolerances to be in accordance with the NSCS unless noted otherwise. It is the Contractor's responsibility to check that these tolerances are sufficient to accommodate fittings, pre-fabricated items, window frames, lifts, joints etc and he shall work to reduced tolerances where required for these items.

1.5 The Contractor shall make provision for the safe storage and handling of all material constituents of the concrete mix including cement replacements, additives and curing agents, with particular regard to the Health and Safety of personnel involved in the production, placing and testing of the concrete.

1.6 Nothing in this Specification should be taken as an instruction to adopt working methods which contravene the CDM Regulations, and all Contractors/Sub-Contractors etc are responsible for ensuring safe procedures which comply with the Regulations.

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I 2.0 Materials ©curtins wconsult ing

2.1 Cement

a) All cement to be used in the works shall be Portland Cement complying with BS 8500-2 unless specified or agreed otherwise in writing by the Engineer.

b) The use of Pulverised Fuel Ash to BS 8500-2 or Ground Granulated Blast Furnace Slag to BS 8500-2 in combination with Portland Cement, as part of the concrete mix, may be permitted subject to the written approval of the Engineer.

2.2 Aggregates

a) The nominal size of aggregate shall be as noted on the Engineer's drawings, or if not noted, 20mm. The use of other nominal sizes of graded aggregate shall be permitted only by the prior written agreement of the Engineer.

b) The Contractor shall ensure that the aggregate he proposes to use on the contract complies with the recommendations of BS 8500-1 and BS EN 1367-4:2008 with regard to the drying shrinkage of the concrete relative to its position in the works.

c) The Contractor shall ensure that the aggregate he proposes to use in concrete acting as a waterproof barrier, for example in retaining walls and basement construction, shall have an absorption value of less than 3% when tested in accordance with BS 812-2.

2.3 Additives

Concrete shall be mixed from cement, fine and coarse aggregate and water only. The use of any additive or admixture shall not be permitted except with the prior written consent of the Engineer.

2.4 Reinforcement

Bar bending schedules will be issued by the Engineer for all bar reinforcement. Coding of reinforcement on drawings and schedules will be in accordance with the recommendations of BS 8666.

The Contractor shall calculate quantities of mesh reinforcement from the drawings, making adequate allowance for laps and off cut wastage.

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I 3.0 Concrete & Concrete Finish ©curtins wconsult ing

3.1 Concrete mixes shall be as specified on the drawings and shall conform to the appropriate clauses of BS EN 206-1 and BS 8500-2. Under normal circumstances, unless noted otherwise, concrete mixes will be specified as either:

- Designated Concrete (e.g. RC35), or - Designed Concrete (e.g. C28/35).

Where appropriate Prescribed, Standardised Prescribed or Proprietary Concretes will be specified.

3.2 Formwork shall be designed to give the required finish as specified by the Architect or noted on the Engineer's drawings, if no specific finish is required, refer to the NSCS.

3.3 Where a concrete finish specified requires stricter tolerances than those specified in the NSCS, then those stricter tolerances shall apply.

3.4 For concrete slabs where no levelling finish is specified, then the required tolerances will be noted on the drawings.

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I 3.0 Concrete & Concrete Finish ©curtins wconsult ing

3.5 The Contractor is to strike formwork without disturbing, damaging or overloading structure, and without disturbing props. Notwithstanding other clauses in this specification and any checking or approvals by the CDM Co-ordinator, the responsibility for safe removal of any part of the formwork and any supports without damaging the structure rests with the contractor.

MINIMUM PERIODS: The following periods (in days) for retaining formwork in position before striking apply to class 42.5 or sulphate-resisting Portland cement concrete with no cement replacement materials or admixtures:

Type of Average mean of daily minimum and maximum air formwork temperatures during the period

160C 7 0C 3 0C

Vertical formwork to columns, %A % 1 walls and beams

Soffit forms to slabs 4 6 8

Props to slabs and soffit forms 10 15 20 to beams

Props to beams 14 21 28

Details of proposed periods for mixes using admixtures or other types of cement are to be submitted to the engineer.

MINIMUM PERIODS: Alternative methods of determining minimum periods for retaining formwork in position may be submitted for approval. The Contractor is to accept responsibility for cost of checking of alternative proposals by the CDM Co-ordinator and for any testing which may be required.

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I 4.0 Testing ©curtins wconsult ing

4.1 The Contractor shall include for all tests specifically required in this Specification.

4.2 The Contractor wiil not be paid for any tests required as a consequence of any failure by the Contractor to comply with this Specification.

4.3 At the commencement of the Works, each type of aggregate to be used in the structural concrete shall be tested for compliance with the Specification. At the same time 5kg samples of the same aggregates shall be made available for inspection by the Engineer.

4.4 Concrete test cubes shall be made, cured and tested in accordance with the recommendations of BS 1881.

A set of three concrete test cubes shall be prepared for each sample and shall be taken at the point of discharge into the works.

One shall be tested at seven days as a guide to the crushing strength of the cubes at twenty-eight days. The remaining two shall be tested at twenty-eight days.

4.5 Compliance with the specified characteristic strength of the concrete shall be based upon the twenty-eight day results, in accordance with BS EN 206-1.

If the test results fail to comply, that area which the cube represents shall be classed as defective.

4.6 Sets of cubes shall be taken at the following maximum intervals, or as directed by the Engineer:

a) Structural elements up to 0.2m 2 cross sectional area per 4m 3 or less b) All other reinforced concrete elements per 12m 3 or less c) Floating ground slabs per 20m 3 or less d) Mass concrete per 50m 3 or less.

4.7 Slump tests of the mixed concrete shall be carried out in accordance with BS EN 12350-2 for every batch of concrete, or as directed by the Engineer. The results shall be kept by the Contractor for inspection by the Engineer.

Compliance shall be assessed in accordance with BS EN 206-1.

4.8 The cement content and water cement ratio of any batch of concrete shall comply with BS EN 206-1 and BS 8500-2. The Engineer may request random tests in accordance with BS EN 206-1 to check the cement content and/or the water/cement ratio of any batch of concrete.

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4.0 Testing ©curtins wconsult ing

4.9 The Engineer reserves the right to class as defective any concrete which is suspect due to lack of information or test results.

4.10 Load tests of complete parts of the structure may be called for by the Engineer at any time if the structural condition of that part of the work is in doubt. Where the results of such tests indicate that any member or part of the structure does not comply with this Specification that part of the structure shail be classed as defective work.

4.11 Achievement ofthe specified characteristic strength shall not be the sole criterion for acceptance. Cement content, apparent water content, slump, compactability, colour and other properties of the concrete, if not suitable for the proposed end use, shall be the basis of rejection without consideration of the test results.

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