MODEL CLAUSES FOR CIVIL ENGINEERING WORKS

Transcription

1 MODEL CLAUSES FOR CIVIL ENGINEERING WORKS SECTION 80 STRUCTURAL CONCRETE Contents Page Application of standards and codes of practice Classification of concrete mixes generally Cement for ordinary structural concrete Cement for special structural concrete Cement replacement Aggregate for ordinary structural concrete Aggregate for special structural concrete Water Admixtures Miscellaneous aggregates Concrete grade Minimum cement content and maximum water/cement ratio Maximum chloride content Maximum sulphate content Control of alkali silica reaction Current margin for designed mixes Suitability of proposed mix proportions Trial mixes Concrete production Batching and mixing Ready-mixed concrete Compliance with specified requirements generally Compliance with specified strength requirement Compliance with workability requirements Air content of fresh concrete Tests on concrete for other purposes Records Trial panel Release agents Surface finishes Surface impregnation Construction joints Formwork Additional requirements for controlled permeability formwork Transporting, placing and compacting of concrete Striking formwork Curing Accelerated curing Additional requirements for mass concrete pours Additional requirements for in situ concrete Precast concrete construction Grouting of prestressing tendons Reinforcement materials Bar schedule dimensions Fixing 39 Page 1 of 50

2 Reinforcement laps and joints Welding of reinforcement Prestressing tendons materials Positioning of tendons, sheaths and ducts Tensioning the tendons Protection of tendons Supervision of prestressing operations Steel fibre for reinforced concrete generally Steel fibre for track slabs and hardstandings Steel fibre for sprayed concrete Concrete with steel fibres for track slabs and hardstandings Synthetic fibre reinforcement concrete Requirements for sprayed concrete Floor construction Early age grinding Power floating References British Standards 53 Other publications 50 Model Clauses 50 Page 2 of 50

3 SECTION 80 Application of standards and codes of practice STRUCTURAL CONCRETE Concrete shall be produced and placed in accordance with this Section when it is used for all structural concrete except as identified in Section 85 of the Model Clauses. Concrete and the constituent materials shall comply with BS 5400: Part 7:1978 except where qualified, amended or replaced by the following Clauses. All numbers in parentheses within the heading margin are the relevant clause numbers within BS 5400: Part 7:1978. Classification of concrete mixes generally (3.1.1) Delete BS 5400: Part 7, clause 3.1.1, and the following Structural concrete shall be a designed mix, and shall be either ordinary structural concrete or special structural concrete. (3.7) Delete BS 5400: Part 7, clause 3.7. Each concrete mix shall be in accordance with Schedule 80/A, in Appendix 80/1. Cement for ordinary structural concrete (3.2.1) Delete BS 5400: Part 7, clause 3.2.1, and the following shall apply: Cement for ordinary structural concrete shall be one of the following: (i) Portland cement to BS EN 197-1:2000, (CEM 1), (ii) Portland blast furnace cement to BS EN 197-1:2000 (CEM 111A, CEM 111B), (iii) (iv) (v) (vi) Sulphate resisting Portland cement to BS 4027:1996 (SRPC), Portland pulverised fuel ash (PFA) cement to BS EN 197-1:2000 (CEM 11A, CEM 11B), Portland cement to BS EN 197-1:2000 mixed with PFA in accordance with BS EN A1:2007, subject to the limits specified in BS 5400:Part 7 and Clause (C11B, C1V B), Portland cement to BS EN 197-1:2000 mixed with ground granulated blast furnace slag to BS 6699 subject to the limits specified in BS 5400:Part 7 and Clause (C11, C111A, C111B). Page 3 of 50

4 All Portland cements shall be obtained from a company that has a quality system for product conformity approved in accordance with BS EN ISO 9001 by a body accredited by the United Kingdom Accreditation Service (UKAS) or equivalent. Cement for special structural concrete (3.3.1) Delete BS 5400: Part 7, clause 3.3.1, and the following shall apply: Cement for special structural concrete shall comply with Clause or, subject to the agreement of the Employer s Representative, with the following: (i) high alumina cement to BS EN 14647: High alumina cement shall only be used where early and rapid strength gain is required, and the required strength gain cannot be obtained using the other cements specified in this Clause with, where appropriate, an accelerating admixture to BS EN 934-2:2001, (ii) low heat Portland cement to BS 1370, (iii) high slag blast furnace cement to BS EN 197, (iv) Portland cement to BS EN 197-1:2000 mixed with ground granulated blast furnace slag to BS 6699 subject to the limits specified in Clause , (v) modified Portland cements to BS EN 197-1:2000, (vi) Portland cement to BS EN 197-1:2000 mixed with additional silica fume slurry having a current British Board of Agrément certificate and source accepted by the Employer s Representative, subject to the limits specified in Clause Cement replacement Pulverised fuel ash (PFA) used as a cement replacement shall not be less than 21% or more than 35% by weight of the total cementitious content, except as qualified below. The maximum limit of PFA may be increased to 55% provided that the resultant concrete will have a minimum strength class of C20/25, a maximum water cement ratio of 0.65, a minimum cement content of 260 kg/m³ and the concrete is to be either: (i) (ii) located below final ground level, located permanently underwater, Page 4 of 50

5 (iii) coated by an approved protective treatment which inhibits the passage of carbon dioxide. Cement replacement in sprayed concrete shall not exceed the limits specified in the 'European Specification for Sprayed Concrete' published by the European Federation of Specialist Construction Chemicals and Concrete Systems (EFNARC). Where PFA is proposed to be used in the concrete mix, the Employer s Representative shall be provided with a certificate to show that the material is in accordance with BS EN 450-1:2005+A1:2007, with the grading and name of the power station. Ground granulated blast furnace slag (ggbs) used as a cement replacement in ordinary structural concrete shall not exceed 65% by weight of the total cement. Ggbs used as a cement replacement in special structural concrete shall not be less than 50% or more than 80% by weight of the total cement. Where ggbs is proposed to be used in a concrete mix, the Employer s Representative shall be provided with a certificate to show that the material complies with BS Silica fume used in special structural concrete shall not exceed 15% by weight of the total cement. Aggregate for ordinary structural concrete (3.2.2) Delete BS 5400: Part 7, clause 3.2.2, and the following Aggregates for ordinary structural concrete shall be one of the following: (i) (ii) aggregates from natural sources to BS EN 12620:2002, as qualified by this Clause, air cooled blast furnace slag to BS EN 12620:2002. When air cooled blast furnace slag is included in the concrete mix, the aggregate shall be sampled and tested at a frequency agreed with the Employer s Representative to confirm its bulk density. Where significant variation from that used in the mix design is found, the mix shall be adjusted to allow for the variation in the bulk density of the aggregate. Page 5 of 50

6 The shell content of the aggregates included as calcium carbonate determined in accordance with BS :1985 shall not exceed the values stated in BS EN 12620:2002. Where no nominal maximum size of aggregate is specified in Schedule 80/A the nominal maximum size of the aggregate shall be as specified below such that the concrete can be placed and compacted around the reinforcement without segregation. The nominal maximum size of the aggregate shall not exceed: (i) (ii) (iii) 0.25 x the smallest dimension of the structural member, the clear distance between reinforcing bars less 5mm, or 0.75 x the clear distance between reinforcing bars, whichever is the less, 0.75 x the concrete cover. The chloride levels of the aggregates shall be determined in accordance with BS :1988 at a frequency agreed with the Employer s Representative. The flakiness index of the coarse aggregate determined in accordance with BS : 1989 shall not exceed 40%, except for natural, uncrushed aggregates included in concrete grade 40 or lower, when the flakiness index shall not exceed 50%. No limit shall apply to concrete grade C12/15 or less. The drying shrinkage determined in accordance with BS :1989 shall not exceed 0.075%. Aggregate for special structural concrete (3.3.2) Delete BS 5400: Part 7, clause 3.3.2, and the following shall apply: Aggregates for special structural concrete shall comply with Clause except that aggregate to BS EN 12620:2002 shall not be used with high alumina cement. Lightweight aggregate shall be in accordance with BS EN :2002. Page 6 of 50

7 Water (3.2.3) Delete BS 5400: Part 7, clause and the following Water for use in the concrete mix shall be clean and free from harmful matter and, where possible, shall be obtained from a water supply company. Should the Contractor wish to use any other source of water, the Employer s Representative shall be advised of the proposed source, and the water shall be tested in accordance with BS EN 1008 at a frequency agreed with the Employer s Representative. Such water shall not be incorporated in the Works without the agreement of the Employer s Representative. If the ph value of such water is less than 4, the water shall not be incorporated in the concrete mix. The sodium oxide and potassium oxide content of such water shall be reported to the Employer s Representative, and shall be taken into account when calculating the total reactive alkali content of the concrete mix in accordance with Clause Admixtures (3.3.4) Delete BS 5400: Part 7, clause , and the following The quantity and method of use of admixtures shall be in accordance with the manufacturer s recommendations and shall be subject to the agreement of the Employer s Representative. Except when used in sprayed concrete, admixtures in a concrete mix shall not exceed 50g/kg of cement nor, unless dispersed in the mixing water, be less than 2g/kg of cement. Liquid admixtures in excess of 3 litres/m 3 shall be taken into account when calculating the water/cement ratio. Accelerating admixtures to be used in sprayed concrete shall not exceed the following: (i) (ii) powder admixtures: 6% of cementitious material by weight, liquid admixtures: 8% of cementitious material by weight. Page 7 of 50

8 When used in a grout mix, the optimum dosage of the admixture shall be determined by trial mixes with the cement to be used in the grout. The dosage shall be within the range recommended by the supplier and shall not exceed 5% by mass of the cement. The method of measuring dosage and checking the weights of pre-packed dry materials shall be agreed with the Employer s Representative. Admixtures shall comply with one of the following: (i) pigments to BS EN 12878:2005, (ii) accelerating, retarding or water reducing admixtures to BS EN 934-2:2001, (iii) air entrainment admixtures to BS EN 934-2:2001, (iv) superplasticizers to BS EN 934-2:2001. Admixtures not included in BS EN or BS EN 934-2:2001 shall be permitted provided that such admixtures comply with the requirements for identification, compatibility, chloride content and alkali content included in this Section and that: (i) (ii) full account of their effect on the finished concrete is taken in determining the concrete mix, there are sufficient data regarding their suitability, including previous use in similar concrete mixes and applications. Admixtures shall not impair the durability of the concrete or grout nor increase the risk of corrosion of reinforcement. Thiocyanate, nitrates, formate and sulphides shall not be included in admixtures. Admixtures shall be manufactured and supplied by a company which has a quality system for product conformity approved in accordance with BS EN ISO 9001 by a body accredited by the United Kingdom Accreditation Service (UKAS) or equivalent. For each proposed admixture the Employer s Representative shall be supplied with the following information: (i) proposed dosage rate per 100 kg of cement, Page 8 of 50

9 (ii) (iii) (iv) (v) details of the effects of underdosage and overdosage, generic type of the active constituents in the admixture, whether or not for the proposed dosage the admixture leads to entrainment of air, where two or more admixtures are to be used in the same concrete mix, information on the interaction and compatibility of the admixtures, including confirmation obtained from each respective admixture manufacturer on the compatibility of the admixtures to be used. Where practicable, admixtures for inclusion in a concrete mix shall be added at the batching plant. Admixtures for inclusion in grout may be added at Site. Admixtures shall not be used with high alumina cement. Miscellaneous aggregates (3.4) In BS 5400: Part 7, clause 3.4.1, delete reference to BS 877, and amend reference to BS 882 (coarse 3 and 4) to BS 882, table 4, Zones M or F. Delete BS 5400: Part 7, clause and the following Aggregate for use as a concrete wearing surface shall be in accordance with the Manual of Contract Documents for Highway Works, Volume 1, Specification for Highway Works, Series Concrete grade (3.5.1) Delete BS 5400: Part 7, clause and the following The compressive strength grade of the concrete shall be in accordance with the design assumptions as detailed in Schedule 80/A of Appendix 80/1 and also with BS :2002 Clause A7. The minimum strength grade shall be in accordance with BS :2002 clause A5. The class of concrete shall be specified by the grade and nominal maximum aggregate size. Page 9 of 50

10 Minimum cement content and maximum water/cement ratio (3.5.2) The minimum cement content shall be not less than the minimum stated in BS :2002 clause A5 appropriate to the condition exposure, sulphate class of the surrounding soil or water, and cement type, as modified by BS :2002 clause A5 according to the nominal maximum aggregate size. For reinforced concrete below ground level, the minimum cement content shall be 300 kg/m 3. Where concrete is to be placed under water or is to support fluid, the minimum cement content shall be 380 kg/m 3. Concrete that will be exposed to sea water shall have a minimum cement content not less than 400 kg/m 3. The maximum water/cement ratio shall be in accordance with BS :2002 Clause A5 appropriate to the condition exposure and sulphate class of the surrounding soil or ground water. The minimum cement content when high alumina cement to BS EN 14647:2005 is used shall be 400 kg/m³, and the maximum water/cement ratio mix shall be For the limits specified in this Clause, the minimum converted strength should not be less than 32/40 N/mm². (3.9.3, 3.9.5) Delete BS 5400: Part 7, clauses and Maximum chloride content Maximum sulphate content Control of alkalisilica reaction The total chloride content of a concrete mix from the cement, aggregate and any other source shall not exceed the relevant limit stated in BS :2002 Clause A9 determined in accordance with BS : The maximum sulphate content of a concrete mix expressed as sulphuric anhydride (SO 3 ) shall not exceed 4 % by weight of cement. The sulphate content shall be calculated from the sulphate content of the concrete mix constituents in accordance with the relevant British Standard for the constituent Except where all the aggregates to be used in the concrete mix have been certified by a qualified chemist competent in concrete chemistry as having normal or low reactivity as defined in clauses 19.2(a) to 19.2(c) of the Concrete Society s Technical Report No. 30, the reactive alkali content of the concrete mix shall not exceed 3 kg/m³. Page 10 of 50

11 The reactive alkali content of the concrete mix, in terms of sodium oxide equivalent (Na 2 O), shall be expressed as specified in BS :2002 Annex C, using the guaranteed alkali limits of the constituents of the concrete mix. The Employer s Representative shall be provided with copies of test certificates showing the average value of the acid soluble alkali content determined in accordance with BS EN 196-2:2005 for: (i) (ii) cement during the period of manufacture, any pulverised fuel ash or ground granulated blast furnace slag for the preceding 25 week period. The equivalent sodium oxide content of the aggregate shall be calculated from the quality of chloride ion present measured in accordance with BS :1988. Current margin for designed mixes (3.6.1) In addition to BS 5400: Part 7, clause 3.6.1, for concrete up to grade C12/15, the current margin for a designed mix shall be determined by the Contractor and shall be taken as the lesser of: (a) (b) 1.64 times the standard deviation of cube compressive strength test results on at least 100 separate batches of concrete of nominally similar proportions of similar materials and produced over a period not exceeding 12 months, by the same plant under similar supervision, but not less than one sixth of the characteristic strength for concrete up to grade 12/15 or 3.0/3.75 N/mm 2 for concrete of grade 16/20 or above times the standard deviation of cube compressive strength test results on at least 40 separate batches of concrete of nominally similar proportions of similar materials and produced over a period not less than 5 days but not exceeding 6 months, by the same plant under similar supervision, but not less than one third of the characteristic strength for concrete up to grade 12/15 or 6.0/7.5 N/mm 2 for concrete of grade 16/20 or above. Page 11 of 50

12 Where there is insufficient data to satisfy sub-clauses (a) or (b) above, the margin for the initial mix design shall be taken as two thirds of the characteristic strength for concrete up to grade 12/15 or 12/15 N/mm 2 for concrete of grade 16/20 or above. This margin shall be used as the "current margin" only until sufficient data are available to satisfy sub-clauses (a) or (b) above. However, when the specified characteristic strength approaches the maximum possible strength of concrete made with a particular aggregate, a smaller margin (not less than one third of the characteristic strength for concrete up to grade 12/15 or 6.0/7.5 N/mm 2 for concrete of grade 16/20 or above) may be used for the initial mix design. Suitability of proposed mix proportions (3.6.2) Delete the alternative specified in BS 5400: Part 7, clause 3.6.2(b)(3), and the last paragraph of BS 5400: Part 7, clause The following paragraphs shall apply. The types and sources of cement, aggregates, pulverised fuel ash, and ground granulated blast furnace slag to be included in the concrete mix shall be agreed by the Employer s Representative. The cement type used in the concrete mix shall be suitable for the application of the concrete (plain, reinforced, post-tensioned or prestressed), the heat development in the concrete mass, the dimensions of the structure, and the sulphate class listed in BS :2002 Clause A5. In addition the concrete mix shall be selected to satisfy all the performance criteria for fresh and hardened concrete, and to give a workability consistent with the proposed method of construction. The concrete mix shall minimise segregation, permeability, bleeding, plastic settlement, shrinkage and thermal cracking, and shall produce the surface finishes specified on the Contract Drawings and in accordance with Clause Where practicable, plastic settlement, shrinkage and thermal cracking shall be minimised by the use of pulverised fuel ash or ground granulated blast furnace slag in accordance with Clause and provided the use of such materials has no deleterious effects. Synthetic fibres included in the mix to limit plastic settlement, plastic shrinkage, thermal cracking, or as an alternative to air entrainment for freeze/ thaw resistance, shall comply with Clause Page 12 of 50

13 Where the proposed concrete mix is to be pumped, the Employer s Representative shall be provided with evidence that the mix can be pumped without segregation, bleeding or persistent blockages. For a concrete mix specified to be suitable for water impermeable concrete, the resistance to water penetration when tested according to BS EN :2000 shall have a maximum penetration of less than 50 mm, and mean average values of penetration less than 20 mm. The water/cement ratio shall not exceed Any change in the source of the concrete mix constituent material or in mix proportions, shall be agreed by the Employer s Representative, except changes in total cementitious material content of not more than 20 kg/m³, and where included changes in the content of pulverised fuel ash or ground granulated blast furnace slag of not more than 10 kg/m³. Trial mixes (3.6.3) Further to BS 5400: Part 7, clause 3.6.3, trial mixes are not required for concrete where the concrete supplier can demonstrate to the Employer s Representative that, for the proposed concrete mix, 40 recent test and sampling results for a related mix (including admixtures, where applicable), confirm the attainment of the specified strength, including early high strength where applicable, within the current margin in accordance with the Clause Where trial mixes are not proposed to be carried out, the following information shall be provided to the Employer s Representative: (i) (ii) (iii) (iv) confirmation that the relationship for the family of mixes exists and is current, the 40 most recent results for the materials at the reference mix level that exist to justify the reference mix cement content (results at the reference mix or transformed to the reference mix), the difference in the cement content of the reference mix, and the specified mix, confirmation that the data has been produced in accordance with the Quality Scheme for Ready- Mixed Concrete Regulations. Where the above information for a concrete mix cannot be provided, trial mixes shall be carried out. Page 13 of 50

14 Where trial mixes are carried out to demonstrate high early strength, for each mix a set of nine test cubes shall be made from each of three consecutive batches. Test cubes shall be tested at the following ages: (i) 8 hours, or as specified in Appendix 80/2, (ii) (iii) 24 hours, 28 days. For any trial mix the average strength of the nine cubes tested at 28 days shall exceed the specified characteristic strength by the lesser of: (i) (ii) 11.5 N/mm², or, the current margin less 3.5 N/mm². Where high alumina cement to BS EN 14647:2005 is used in the mix, three additional cubes shall be taken, and shall be subjected to an agreed accelerated curing regime, and tested to determine the converted strength. Trial mixes of proposed concrete mixes shall demonstrate the workability of the concrete mix and the action of admixtures and/or silica fume slurry, and shall prove the ability of the proposed concrete mix to attain the specified characteristic strength. Trial mixes shall be carried out a minimum of six weeks before the concrete is programmed to be incorporated in the Works. The workability of each batch of the concrete mix shall be tested three times at equal intervals within one hour of mixing using one of the methods appropriate to the workability of the concrete mix specified in Clause Concrete production (3.8.2) Delete BS 5400: Part 7, clause 3.8.2, and the following Cement, pulverised fuel ash, and ground granulated blast furnace slag shall be stored and used in accordance with BS :2002 clause 11. The Employer s Representative shall be provided with a certificate confirming that the cement complies with the relevant British Standard, and including results of tests carried out to verify such compliance. Page 14 of 50

15 (3.8.3) Further to BS 5400: Part 7, clause 3.8.3, for each aggregate type proposed to be used, the Employer s Representative shall be provided with all the information listed in BS EN 12620:2002 Annex A, and a copy of the relevant test results. For concrete with exposed faces, surface-marring aggregates such as pyrites shall not be used. Concrete to be placed in situ or to form precast concrete units to be constructed at the Site shall be produced only from a batching plant holding current Quality Scheme for Ready-Mixed Concrete certification for product conformity except as follows: (i) (ii) dry process sprayed concrete, concrete pours less than 3 m³, (iii) as specified in Appendix 80/3. For concrete produced by an on-site batching plant, prior to any concrete being placed in the Works, the Employer s Representative shall be provided with confirmation of the concrete supplier s quality assurance certification in accordance with BS :2002 clause A5 and a copy of the certification for product conformity for the site batching plant. Concrete for precast concrete units to be constructed offsite shall be produced either by a batching plant holding current Quality Scheme for Ready-Mixed Concrete certification for product conformity, or at the precast concrete manufacturer s works where the Contractor can demonstrate that concrete production is included in the quality system for product conformity specified in Clause Lightweight concrete such as foamed concrete shall be produced under controlled conditions by blending cement in accordance with Clause , sand, and water with a foaming admixture to produce a free flowing, self levelling, non combustible lightweight concrete with a density not exceeding 1200 kg/m 3. Page 15 of 50

16 Batching and mixing (3.8.4) References to cement in BS 5400: Part 7, clause shall be deemed to include all the cementitious materials listed in Clauses and In addition to BS 5400: Part 7, clause 3.8.4, the following All concrete mix constituents shall be thoroughly mixed together to produce a concrete mix with a homogeneous consistency. Admixtures and steel or synthetic fibres included in the concrete mix shall be distributed evenly throughout each batch. No concrete mix shall be altered after the concrete has left the mixer. Where water with a temperature in excess of 60 C is used, the water shall be mixed with the aggregate before coming into contact with the cement. Water in excess of 80 C shall not be used. Where lightweight aggregate is specified, the density of the concrete shall not exceed 1850 kg/m 3. The requirements of BS 5400: Part 7, clause shall be amended as follows. The quality of water in the mix, and the batch weight of the aggregate shall be adjusted to allow for the free moisture content of the aggregate. Delete references to BS 1305 (Batch type concrete mixers), and BS 4251 (Truck type concrete mixers). Mixers shall be capable of uniformly distributing the constituent materials to obtain a uniform workability within the mixing time and at the mixing capacity. Ready-mixed concrete (3.8.6) In addition to BS 5400: Part 7, clause 3.8.6, the following Ready-mixed concrete shall only be supplied from a batching plant holding current Quality Scheme for Ready- Mixed Concrete certification for product conformity. The Employer s Representative shall be provided with confirmation of the concrete supplier s quality assurance certification in accordance with BS :2002 and a copy of the certification for product conformity for the batching plant. Verification of the certification shall be obtained from: Page 16 of 50

17 Quality Scheme for Ready-Mixed Concrete 1 Mount Mews High Street Hampton Middlesex TW12 2SH Tel: Fax: Delete reference to BS 4251 in BS 5400: Part 7, clause Truck mixers shall be capable of delivering the concrete in a homogenous mixed state. Water and admixtures shall be added under supervision either at the Site or at the batching plant. No water shall be added in transit or on site if the water was originally added at the batching plant. Truck mixers shall be equipped with appropriate measuring and dispensing equipment. Compliance with specified requirements generally (3.9.1) Compliance with specified strength requirement (3.9.2) In addition to BS 5400: Part 7, clause 3.9.1, the following Testing of fresh and hardened concrete and constituent materials shall be carried out by an organisation accredited by the United Kingdom Accreditation Service (UKAS) for the relevant tests. All details of the company proposed to be used shall be submitted to the Employer s Representative for acceptance Delete BS 5400: Part 7, clause , and the following Where the Contractor is able to demonstrate in accordance with Clause that a trial mix for the proposed mix is not required, compliance testing for specified strength requirements in accordance with BS :2002 shall be carried out only for concrete of compressive strength grade C25/30 or greater. For all grades of concrete, where the Contractor is able to demonstrate in accordance with Clause that a trial mix for the proposed mix is not required, the Employer s Representative shall be provided with a mix design certificate detailing the concrete mix constituents and their quantities, mix density, and confirming that for the proposed mix, the specified strength will be obtained within the current margin. Page 17 of 50

18 The mix design certificate shall also confirm: (i) (ii) (iii) (iv) that the relationship for the family of mixes exists and is current, that 40 results exist to justify the reference mix cement content, the difference in the cement content of the reference mix and the proposed mix, that the data has been produced in accordance with the Quality Scheme for Ready-Mixed Concrete Regulations. Where a mix design certificate for a concrete compressive strength grade C25/30 and above is provided, the minimum rate of sampling for compliance testing for specified strength requirements for each concrete mix shall be 100m³ or 100 batches with not less than one sample taken on each day that the concrete mix is used. Where a mix design certificate for a concrete compressive strength grade C25/30 and above cannot be provided, compliance testing for specified strength requirements shall be carried out at the rate of sampling in accordance with Table 80/1, with not less than one sample taken on each day that the concrete mix is used. Table 80/1 Type of concrete Sample from one batch selected to represent an average volume of not more than the lesser of: Prestressed or post-tensioned 10 m³ or 10 batches concrete, and reinforced concrete cantilevers Highly stressed parts of the 10 m³ or 10 batches works as specified in Appendix 80/4 All other reinforced concrete 20 m³ or 20 batches Mass concrete 50 m³ or 50 batches Sampling, curing and testing of fresh and hardened concrete shall be carried out in accordance with the requirements of BS EN Parts 1 to 7 and BS EN Parts 1, 2, 3 and 7. Conformity testing and conformity criteria shall be carried out in accordance with BS8500-2:2002 clause 10 and the relevant requirements of BS EN 206-1:2000. Page 18 of 50

19 Compliance with workability requirements (3.9.4) Delete BS 5400: Part 7, clause 3.9.4, and the following The workability of the fresh concrete shall be such that the concrete is suitable for the conditions of handling and placing, so that after compaction, the concrete surrounds all reinforcement, prestressing tendons, ducts and steelwork without segregation and completely fills the formwork. Workability shall be measured for each batch of concrete or as directed by the Employer s Representative using one of the tests appropriate to the designed workability specified in BS EN 12350: Parts 2, 3, 4 or 5. Workability shall be within the tolerances stated in BS :2002 Annex B of the design value. Air content of fresh concrete (3.9.6) Delete BS 5400: Part 7, clause 3.9.6, and the following Concrete shall have a composition such that after compaction it has a closed structure, i.e. the air content by volume (entrained air and aggregate pores excepted) shall, when tested in accordance with BS EN clause 5.4.3, be not more than: (i) (ii) 3% for aggregates 16 mm nominal size, 4% for aggregates <16 mm nominal size. Where air entrainment admixtures are included in the concrete mix, the mean air content of the fresh concrete by volume at the moment of delivery into the Works shall be: (i) (ii) (iii) (iv) 7.5% for natural aggregates 10 mm nominal size, 6.5% for natural aggregates 14 mm nominal size, 5.5% for natural aggregates 20 mm nominal size, 4.5% for natural aggregates 40 mm nominal size. For concrete required in accordance with Clause to be tested for compliance with specified strength requirements, the air content shall be checked as described in BS EN 12350: Part 7 at the rate of sampling specified in Clause The tolerance on the specified mean total air content shall be in accordance with BS :2002 Annex B. Page 19 of 50

20 Tests on concrete for other purposes (3.9.7) Further to BS 5400: Part 7, clause 3.9.7, for precast prestressed beams, test cubes shall be made equally from the concrete batches used in the first and last cast beam in each line of a pretensioning bed and tested in accordance with BS EN 12390: Parts 1 & 3 to confirm attainment of the concrete strength specified for transfer. For post-tensioned concrete, test cubes shall be made and tested in accordance with BS EN 12390: Parts 1 & 3 to confirm attainment of the concrete strength specified for stressing. The concrete shall be sampled at a rate sufficient to demonstrate that the required strength of the concrete at transfer has been reached, subject to a minimum of six test cubes. The test cubes shall be cured under conditions agreed by the Employer s Representative which shall simulate the conditions of the concrete member. Should the Contractor wish to take additional cubes for determining when formwork may be struck, such cubes shall be taken at no additional cost to Network Rail. Records Records shall be kept of the positions in the Works of all batches of concrete from which samples for testing have been taken. Each test cube or cylinder shall have an identification placed upon it which shall be recorded together with the date of casting and the date at which the cube or cylinder was despatched to the laboratory for testing. The laboratory test report shall include all information specified to be provided in BS EN :2002. All the information reported by the laboratory shall be added to the records kept by the Contractor and written confirmation of the test results provided to the Employer s Representative within 24 hours of completion of the tests. Trial panel (3.10.1) Delete BS 5400: Part 7, clause , and the following When required in Appendix 80/5 and before commencing concreting the Contractor shall prepare a trial panel of a size stated that will demonstrate that the required surface finish can be achieved by the methods proposed. The panel shall contain representative reinforcement and shall be filled with the proposed concrete compacted by the method to be used in the Works. Page 20 of 50

21 As soon as practicable after compaction, the forms shall be removed to check that the required surface finish and compaction has been achieved. Release agents (3.10.3) Delete BS 5400: Part 7, clause and the following Release agents for the formwork shall enable the formwork to be removed without damage to the concrete surface. There shall be no adverse residual effect from the release agent on the concrete surface. Where the concrete surface is to be permanently exposed, only one agent shall be used throughout the entire area. Release agents shall be applied evenly and shall not be permitted to come into contact with reinforcement, prestressing tendons and anchorages. Any such contact shall be washed free of contamination. In addition, release agents shall not be permitted to come into contact with steel beams either internal or external to the concrete. Where concrete is to receive an applied finish, or surface impregnation, release agents shall be compatible with the particular process. Surface finishes (3.10.4) Formed surfaces Delete BS 5400: Part 7, clause and the following Formed finishes shall produce the following classes of finishes using formwork specified in Clauses and Class F1 The surface finish shall be as struck and free from voids, honeycombing or other large blemishes with no extra requirement. Class F2 The irregularities in the finish shall be no greater than those obtained from the use of wrought thickened square edged boards arranged in a uniform pattern. The finish is intended to be left as struck but shall be free from all but minor holes, fins, minor blemishes and surface discolourations. Formed surfaces that are to receive a waterproofing system shall be Class F2 finish with holes, fins, sharp irregularities in excess of 2 mm and other blemishes made good. The surface shall be prepared in accordance with the waterproofing manufacturer s specification. Page 21 of 50

22 Class F3 The surface shall be smooth and of uniform texture and appearance. The formwork lining shall leave no stain on the concrete and shall be so joined and fixed to its backing that it imparts no blemishes. It shall be the same type and obtained from only one source throughout any one structure. The Contractor shall make good any imperfections in the finish. Internal ties and embedded metal parts shall not be used. Class F4 The requirements for Class F4 are as for Class F3 except that internal ties and embedded metal parts shall be permitted. The ties shall be positioned only in rebates or in other positions as described in Appendix 80/6. Class F5 The requirements for Class F5 are as for Class F3 except that provision for the embedment of metal parts in the Permanent Works on a regular spacing, shall be allowed. For formed finishes providing a special featured finish including pronounced marking, the use of absorbent form liners, coarse aggregate finish or other treatment, a trial panel in accordance with Clause shall be provided. Special featured formed finishes shall be constructed as described in Appendix 80/6 Where an exposed aggregate finish is specified the formwork shall be treated with a retarding agent acceptable to the Employer s Representative. Following the removal of the side forms the laitance shall be removed to a depth described in Appendix 80/6. A construction joint finish obtained in accordance with Clause shall be provided to the sides of precast beams to form shear connected joints. Where an unformed surface of a bridge deck abuts the web of a steel girder, a trapezoidal rebate 20 mm deep, with base dimension 15 mm and upper dimension 35 mm, shall be provided to accommodate a movement joint seal in accordance with Sections : Waterproofing. Page 22 of 50

23 Unformed surfaces The following classification for unformed finishes shall apply. Class U1 The concrete shall be levelled and screeded to produce a uniform surface to the profile shown on the Contract Drawings. No further work shall be applied to the surface unless it is used as a first stage for another class of finish. Class U2 After the concrete has hardened sufficiently, the Class U1 finish shall be floated by hand or machine, sufficient only to produce a uniform surface free from screed marks. Class U3 When the moisture has disappeared and the concrete has hardened sufficiently to prevent laitance from being worked to the surface, a Class U1 finish shall be steel-trowelled under firm pressure to produce a dense, smooth uniform surface free from trowel marks. Class U4 The concrete shall be levelled and screeded to produce a uniform surface. When the concrete has hardened sufficiently and the bleed water evaporated, the surface shall be trowelled to produce a hard dense surface free from screed marks and exposed aggregate. Finally the surface shall be lightly textured with a wooden float or equivalent. Alternatively the concrete shall be levelled, screeded and floated to produce a uniform surface and immediately before the waterproofing operation this surface shall be prepared in accordance with the waterproofing manufacturer s specification. A Class U4 finish shall be used for a bridge deck which is to receive a sprayed waterproofing system. The finished surface shall not deviate from the required level by more than 10 mm over a 3.0 metre gauge length, or have any abrupt irregularities greater than 3 mm. Page 23 of 50

24 Class U5 The concrete shall be levelled and screeded to produce a uniform finish. When the concrete has hardened sufficiently to prevent laitance from being worked to the surface it shall be floated to produce a surface free from screed marks and exposed aggregate. Finally the surface shall be textured to suit the requirements of the particular waterproofing and surfacing system. The accuracy of the finished surface shall be such that it does not deviate from the required profile by more than 5 mm over a 3.0 metre gauge length, or have any abrupt irregularities. Other classes. The finishes shall comply with the specific requirements described in Appendix 80/6. Surface impregnation Material The impregnation of reinforced, prestressed and posttensioned concrete structures using hydrophobic porelining impregnants (silane surface impregnation) shall be applied to the surfaces specified on the Contract Drawings in accordance with the manufacturer's instructions unless otherwise directed by Contract Documents or agreed by the Employer's Representative. The works shall, in addition, be carried out in accordance with Health and Safety requirements, COSHH requirements and Waste Disposal Authority requirements. The material for impregnation shall be monomeric alkyl (isobutyl)-trialkoxy-silane with a minimum active content of 92% delivered to the Site in sealed containers. Other materials shall only be used on the instruction of the Employer s Representative. Page 24 of 50

25 The refractive index of the material shall comply with the value stated in the manufacturer's product specification, within a limit of units. The refractive index shall be checked as follows: 1) Collect samples of the material from a newly opened container and from the spraying nozzle. 2) Measure the refractive index of three samples from both the container and spray nozzle using a portable refractometer. 3) Measure the temperature of the samples (portable refractometers have temperature measuring capability). 4) Correct the refractive index measurements for the temperature stated in the manufacturer's product specification. 5) If the temperature corrected measured value of the refractive index exceeds the manufacturer's specified value by more than units then a laboratory check shall be undertaken to confirm compliance. For each delivery, the Contractor shall provide a certificate confirming that the material complies with the material specification above. No material shall be used in the works until the Certificate of Compliance has been accepted by the Employer's Representative. The material shall be stored in a secure facility that has a dry, frost-free environment protected from direct heat. The containers shall remain sealed until their contents are required for use. The contents of any opened container shall be used within 48 hours or else disposed of safely as described later in this Clause. Materials offering a performance in respect of the protection of concrete and long term durability equivalent to that of monomeric alkyl (isobutyl)-trialkoxy-silane will be accepted. The assessment of the durability of an alternative surface applied hydrophobic pore lining impregnating material will be based on the provision of evidence that it has, in practice, provided an effective water repellent but vapour-permeable layer at the concrete surface for a period of not less than 15 years after application. Page 25 of 50

26 Spraying Equipment Protective Measures A power driven continuously circulating pumped system operating at a low nozzle pressure shall be used to apply the material in such a way as to avoid atomisation. Water shall be prevented from entering any part of the equipment. A pressure gauge shall be installed between the trigger valve and spray lance to enable the pressure to be monitored. A 'kill' switch shall be provided so that the pumping system may be stopped immediately should this be required. Use and handling of the silanes shall be in strict accordance with the manufacturer's recommendations, and in full compliance with all current Health and Safety legislation. The Contractor shall ensure that only fully trained operatives undertake impregnation operations, and where necessary carry out trials to verify procedures. Measures shall be taken to ensure that no impregnation material enters into any drainage system or watercourse. The Contractor shall obtain all necessary written permissions and licences from the appropriate authorities, prior to any silane operations above or adjacent to any watercourse. Measures shall be taken to ensure that no impregnation material comes into contact with any humans, animals, vegetation or vehicular traffic by providing suitable and adequate protection and traffic management. The Contractor shall obtain approval from the Employer's Representative and all other authorities' licenses, agreements and permissions associated with traffic safety, management and protective measures in advance of the commencement of impregnation operations. Elastomeric bearings, painted steel surfaces, exposed bituminous materials, and joint sealants adjacent to structural elements to be impregnated shall be masked off or covered before and during impregnation operations. In the case of spillage, action shall be taken immediately to limit the extent of the spillage and the Employer's Representative and other relevant authorities shall be informed at once. Surface Condition Areas to be treated shall be protected from any adverse effects of the weather and shall be surface dry for a minimum of 24 hours before application commences. Artificial drying of surfaces shall not be permitted. Page 26 of 50

27 Surfaces shall be free from loose or deleterious matter and residues of curing membranes, release agents, graffiti and graffiti removal agents (including any harmful residual effects from the application of curing membranes) before impregnation commences. Existing structures shall be hand brushed with a stiff bristle brush to remove surface deposits. Where deleterious surface deposits cannot be removed using a stiff bristle brush they shall be removed by light grit blasting. Water jetting or steam cleaning shall not in general be used as a means of surface preparation. Application The Contractor shall submit a method statement to the Employer's Representative and shall obtain the Employer's Representative's written approval before commencing impregnation operations. Impregnation of the face of a structural element shall be carried out in a single continuous operation for each application. Impregnation shall not be carried out within 7 days of the placing of the concrete, or 3 days after concrete repairs have been completed on a structural element. Particular attention is drawn to compliance with the requirements of surface condition. The material shall be applied by continuous spray technique giving saturation flooding, working from the lowest level upwards. Two applications shall be made, each at a coverage of 300 ml/m 2 with an interval between each of at least six hours. Impregnation shall not be carried out in the following conditions: (a) when the shade temperature is below 5 o C, (b) (c) when the temperature of the concrete surface is greater than 25 o C, when the wind speed is in excess of 8 km/hr unless the working area is fully encapsulated. Members shall be protected from rain and spray during application and for at least six hours after completion. Page 27 of 50

28 Disposal Disposal of impregnation material, any contaminated materials and protective sheeting or masking, shall be in strict accordance with the requirements of the Waste Disposal Authority. Whilst on site, all such materials must be retained in a safe and secure facility. The Contractor shall obtain all necessary certificates of approval for the disposal of the materials. Where required in the Contract, the Contractor shall carry out impregnation on trial panels 2m x 2m or equivalent area, one on a vertical and one on a horizontal surface. The Contractor shall then demonstrate on these panels, that the proposed method of working will meet the appropriate requirements of this Clause. The treatment applied shall be certified as effective for at least 15 years. Construction joints (3.11.1) In addition to BS 5400: Part 7, clause , the following Construction joints shall not be formed in concrete completely or partly encasing a steel or concrete beam, except where shown on the Contract Drawings. The location of construction joints shall be selected to minimise plastic shrinkage and plastic settlement. Further to BS 5400: Part 7, clause , a fine water jet shall not be used where the spray is directed at, or may be blown towards, electrified line traction supply conductors. Formwork (3.11.2) In addition to BS 5400: Part 7, clause , the following Formwork to produce the formed finishes in accordance with Clause shall consist of: Class F1 closely jointed sawn boards, plywood sheet metal or other acceptable form material. Class F2 closely jointed prepared boards, smooth sanded plywood, sheet metal or other similar acceptable material arranged in a uniform pattern. Class F3 closely jointed prepared boards that have subsequently been machine sanded, plastic or vinyl faced plywood, polished sheet metal or other similar acceptable material, in panels not less than 2.4 metres by 1.2 metres. Page 28 of 50