Federal Electricity & Water Authority Water Directorate ......BS EN 1997-1 Eurocode 7. Geotechnical design. General rules BS 8007 Code of practice for the structural use of concrete

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Client: FEDERAL ELECTRICITY AND WATER AUTHORITY (FEWA) Project: STANDARD SPECIFICATIONS FOR WATER WORKS

Engineer WATER DIRECTORATE - ASSET MANAGEMENT DEPARTMENT

Title: Technical Terms / Chapter-4 / Engineering Specifications / Civil Engineering Works Specification

CS23-PRE STRESSED CONCRETE WATER TANKS

Office:

DUBAI Order: Document: MWA_PRO_07/WAM-04-CS23 Rev: OCT/2014 sheet: 1 of: 30

Federal Electricity & Water Authority

Water Directorate

Asset Management Department

STANDARD SPECIFICATIONS

FOR WATER WORKS

TECHNICAL TERMS

Chapter – 4

Engineering Specifications

[C-Civil Engineering Works Specifications]

CS23-Pre Stressed Concrete Water Tanks

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CS23-PRE STRESSED CONCRETE WATER TANK

Office: DUBAI Order: Document: MWA_PRO_07/WAM-04-CS23 Rev: OCT/2014 sheet: 2 of: 30

CS23-Pre Stressed Concrete Water Tanks TABLE OF CONTENT

1. INTRODUCTION

2. GENERAL

3. STANDARDS AND CODES

4. GENERAL SCOPE

5. SOIL INVESTIGATION

6. DESIGN

7. DETAILS

8. MATERIALS

8.1 General

8.2 Impervious Membrane

8.3 Cement

8.4 Aggregates

8.5 Water

8.6 Admixtures

9. CONCRETE

9.1 Ready Mixed Concrete

9.2 Workability

9.3 Transportation

9.4 Placing

9.5 Compaction of Concrete:

9.6 Vibrations

9.7 Curing

9.8 Cube Test Work Procedures

9.9 Concrete Cores

9.10 Mix Design

9.10.1 General

9.10.2 Concrete for Water Tank

9.10.3 Concrete for Miscellaneous Works

9.11 The Grades of Concrete

9.12 Quality Assurance of Materials to be Used to Prepare Concrete.

9.12.1 Samples and Testing of Materials

9.12.2 Quality Control on Site

10. REINFORCEMENT

11. POST-TENSION ELEMENTS

12. SHUTTERING/FORM WORK/SCAFFOLDING SYSTEM

13. PROTECTION OF THE CONCRETE

13.1 Blinding or Mudmat Concrete

13.2 Surfaces Below Ground Level

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14. FINISHES

14.1 Foundations

14.2 Internal Finishes

14.3 External finishes

14.3.1 Walls

14.3.2 Roof

15. GROUTING, SEALING AND MISCELLANEOUS

15.1 Grouting Materials

16. WATER BAR

17. JOINTS IN WATER RETAINING STRUCTURES

17. 1 Construction Joints

18. PRECAST CONCRETE

18.1 General

18.2 Marking

18.3 Curing, Maturing and Stacking

18.4 Cement/Sand Mortar

19. PRE-CAST HOLLOW CORE SLAB

20. ELASTOMERIC BEARING PADS (NEOPRENE PAD)

21. MAIN TECHNICAL ELEMENTS TABLE

22. MISCELLANEOUS WORKS

22.1 Ladders , Stairs and Handrails

22.2 Access Covers

22.3 Roof Opening, Hatches, and Ventilators

22.4 Level Indicators and Provision for Level Transmitters

23. HYDROSTATIC TESTING

24. CLEANING AND DISINFECTION

25. EXTERNAL WORKS

26. ASSOCIATED WORKS

26.1 Mechanical

26.2. Electrical Works

26.3 Instrumentation

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CS23-Pre Stressed Concrete Water Tanks ( BY POST TENSION METHOD)

1. INTRODUCTION

The scope of the work comes under this specification describes the current recommended practice for the design, construction, inspection, and testing of reinforced concrete circular, prestressed (horizontal post tensioning) ground level water tanks. The main components of tank structure consist of cast in situ raft slab foundation, cast in situ horrizontal prestressed walls and prestressed precast hollow core roof slab. The peripheral reinforced thrust block to be provided arround the tank wall base after post tensioning activity. Post-Tensioning is a method of pre-stressing reinforcing concrete for structural elements. Pre-stressed concrete has internal stresses (forces) induced into it during the construction phase for the purpose of counteracting the anticipated external loads that it will encounter during its lifecycle. All the works related to RCC Pre-stressed Water Tanks with complete Civil/Electrical/Mechanical/Instrumentation works in all respects including hydrostatic testing, cleaning and sterilization of tank and its piping system shall be in line with quality engineering practices complying with International Standards, High-tech construction methodology and latest technology including complete QA/QC procedures and safety policy. The limits of scope of work shall not be limited to these, but shall include all services and every component required for the completeness of the project and safe and reliable operation. Design of pre-stressed tanks of required capacity shall be carried out by specialist Designer by post-tensioning method including piling system (as per soil investigation report)with latest methodology and technology giving importance to strength, stability and safety, considering the design of the structure with a minimum life of 60 years. The structure shall be designed for adverse loading/stress conditions taking care of wind and earth quake loads. Also, the designer to take care of the safety of the structure during the construction period.Design, supply and install high quality shuttering/form work/scaffolding system for fault free concreting procedure with complete safety features and flexibility for lifting/removal. Guarantee requirements during the 12 months guarantee period in accordance with the conditions of Contract, along with associated external works complete in all respects, including pipe trenches/pipe racks/chambers, drainage system, lighting, markings, etc. in accordance with the conditions of Contract

2. GENERAL

All designs, calculations and execution shall be based on the regulations of these Specifications and the requirements of the applicable standards such as BS, ACI, ASTM or approved equivalent. The recommendation of CIRIA Guide to Concrete Construction in the Gulf region shall also be applicable. The Contractor shall moreover follow the recommendations for concreting in hot weather, as per ACI-305 R77 and the local regulations.

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3. STANDARDS AND CODES

Bs 12 Specification for portalnd cement BSEN 197-1 Cement. Composition, specifications and conformity criteria for common

cements BS 340 Precast concrete kerbs channels, edgings on quadrants BS EN 1339 Concrete paving flags. BS EN 1340 Concrete kerb units. BS 812 Methods of sampling and testing of minerals aggregates, sands and fillers BS EN 932-1 Tests for general properties of aggregates. Methods for sampling BS 882 Coarse and fine aggregates from natural sources. BS EN 12620 Aggregates for concrete BS 1881 Methods of testing concrete BS 3148 Methods of tests for water for making concrete BS EN 1008 Mixing water for concrete. BS 4027 Specification for sulphate resisting Portland cement BS 4449 Specification for hot rolled steel bars for the reinforcement of concrete BS 4461 Specification for cold worked steel bars for the reinforcement of concrete BS 4466 Specification for bending dimensions and scheduling of reinforcement of concrete BS 8666 Scheduling, dimensioning, bending and cutting of steel reinforcement for concrete. BS 4482 Hard drawn mild steel wire for the reinforcement of concrete BS 4483 Steel fabric for the reinforcement of concrete BS 4550 Methods of testing cement BS 5075 Concrete admixtures. Accelerating admixtures, retarding admixtures and water

reducing admixtures. BS EN 934-2 Admixtures for concrete, mortar and grout. BS 5328 Methods of specifying concrete, including ready mixed concrete BS 8500-1 Method of specifying concrete and guidance for the specifier BS 8004 Foundations BS EN 1997-1 Eurocode 7. Geotechnical design. General rules BS 8007 Code of practice for the structural use of concrete for retaining aqueous liquids. BS 8110 Structural use of concrete BS EN 1992-3 Eurocode 2. Design of concrete structures. Liquid retaining and containing

structures C.P. 102 Protection of buildings against water from the ground ASTM A775 Epoxy coated reinforcing steel bars Standards shall include all the latest revisions.

4. GENERAL SCOPE

This specification covers minimum requirements for design and construction of reinforced concrete water storage tanks.

The scope of work shall consist of, but not necessarily limited to, the following: a) Site survey and soil investigation at the proposed location of reinforced concrete reservoir. This shall include cone penetration tests, boreholes etc. complete with report

and recommendations. b) Design of RCC tank complete by specialized designer complete in all respects as per the

requirements in the scope of work. Tanks of capacity more than 0.4MIG shall be designed as pre stessed structure by post tension method.

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c) Excavation for reservoir foundation to remove unsuitable material and to fill the area by suitable structural /road base fill to the level required as per survey/soil investigation recommendations and according to the instructions of FEWA/Engineer.

d) Design, construction and curing of reinforced concrete base slab for reservoir and shear key for construction joints including all excavation dewatering where required, pipe sleeves and built in pipe work, underground protection work etc.

e) Design, construction and curing of reinforced concrete reservoir walls and roof supporting frame including columns,tie beams,roof beams including shuttering, embedded plates for pipe supports, openings for pipes and fittings Provision for level indicators, drain pipe, future service outlets, level indicator pipe, overflow and inlet pipes, , balancing line for future reservoir, manholes control joints etc. including external and internal finishes.

f) Design, supply, and erection of reinforced concrete pre cast hollow core slab for roof of the tank

5. SOIL INVESTIGATION

Specialized geotechnical Company to carryout soil investigations for the site proposed for the construction of tanks. The purpose of these investigations shall be to determine the factors influencing the design and construction such as the type of soil, level of the ground water table, anticipated ground bearing capacity, type of foundations to be adopted and any special measures required to protect the foundations from adverse ground conditions.

6. DESIGN

The Contractor shall employ a specialized designer for the design the water storage tanks in full compliance with all the relevant Standards and Codes of Practice. Detailed designs and working drawings shall be submitted to FEWA and must receive full approval prior to the work commencing on site. It shall be the aim of the Contractor to standardize the dimensions of tank to ensure that the internal capacity is fully utilized and levels are compatible with associated plant.It shall be designed in such a manner that it sustains all loads and deformations of normal construction and use and has adequate durability and resistance. Foundations for the tanks shall be designed to meet the ground bearing conditions prevailing at each of the sites and seismic force. Tank shell/wall shall be designed to meet the adverse stress condition arising from, wind, seismic, pre stressing/ lifting/erection and other complex forces. Roofs of the tanks shall be designed to accommodate thermal and shrinkage effects with pipe support loads and live loads. The grade of concrete shall be based on strength requirements for structures/items. However, the lowest grade of concrete used for structural purposes shall be C40 i.e. concrete having a 28 days cube compressive strength of 40N/mm2.The minimum free board (top water level) shall be 500 mm to roof soffit or beam. The tank’s roof shall be designed for the dead load from the concrete roof, live loads from the roof protection system and an allowance for personnel working on the roof as approved by FEWA/Engineer.Thermal effects due to temperature variations shall also be considered in the design.

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Reinforcement shall be steel reinforcing bars of minimum yield stress = 460 N/mm2 conforming to BS 4449.and high tensile ,low relaxation strands for post tensioning confirming ASTM-A416 with minimum yield stress = 1800 N/mm2 Detailed design calculations shall be provided for the approval of FEWA/Engineer. The tank shall be founded on approved waterproofing membrane laid over 150 mm thick blinding. The blinding in turn shall be laid over approved 1000 gauge polyethylene sheet. Overlap shall be 150 mm and the sheeting shall extend 150 mm beyond the edge of all foundations, floor slabs and paving. The granular sub-base below blinding shall be at least 300 mm thick. Subgrade shall be thoroughly compacted. To avoid possibility of sliding of base slab shall be keyed to the ground below. Joints in reservoirs may be used in conjunction with a corresponding proportion of reinforcement, to control the concrete crack widths arising from shrinkage and thermal changes to within acceptable limits. expansion joints shall be totally eliminated. Calculations showing justification for the provision of joints shall be submitted for approval of FEWA/Engineer.PVC water bars of approved size and make shall be provided at all construction joints.Roof slabs shall be generally designed as hollow core pre-cast slabs for big span tanks and pre-cast solid slab elements for small span tanks.

7. DETAILS

Design, construction, completion, testing, commissioning, and maintenance during guarantee period of Reinforced cement concrete ground level pre-stressed water storage tanks shall be carried out as per the following details . Foundations have to be designed as per soil investigation reports. The tank structure shall be designed for the worst loading / stressing affects. The following are the related works pertaining to RCC water tanks:

Piling system including boring, bentonate protection, concreting with epoxy coated reinforcement caging, pile cutting, related excavation, disposal of cut spoil, backfill and compaction with granular backfill material to the required level including all related tests. The cut off level of pile head shall be decided based on acceptable tank foundation design.

Dewatering/shoring/hoarding for safe construction activities. Structural concrete work of tank in foundation/base slab including washout and

outlet sumps, walls, columns and roof including reinforced concrete surround for outlet and washout lines including blinding concrete.

High quality formwork/shuttering/scaffolding and related works by specialist agency. Post-tensioning works including sheathing, anchor blocks, tendons, tensioning

process, complete test procedures, thrust blocks, etc. by specialist agency. High quality precast hollow core prestressed factory made slabs for roof. Roof topping concrete to slope with polypropylene fiber concrete. Use of construction accessories like water bar, metal water barrier, sealants,

elastomeric neoprene rubber bearing pads, repairing chemicals curing compound, puddle flange, sleeves, groves, rebates, construction joints accessories, sliding joints, swellable water stops, etc.

Application of high quality heavy duty waterproofing membrane with protection layer with to all surfaces of sub-structure concrete in contact with soil.

All civil works related to tank’s GRP piping system as explained elsewhere. All piping shall be minimum GRP Class PN16 unless otherwise specified elsewhere. Construction of washout/outlet sumps, valve chambers, outfall structure for the tank.

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Internal Protective coating as specified to all internal surfaces of the tank including floor, wall, columns and roof as specified.

External painting system to tank wall as specified. Fixing solar reflective water proofing membrane to tank roof. External galvanised steel spiral stair with hand rail including painting. Internal stainless steel (Grade 316L) ladder with cage. Internal stainless steel gratings to washout sump and outlet sump (Grade 316L). Stainless steel (Grade 316L) strainer to outlet Roof access manholes and covers with coating. G.I. Hand rails on tank roof with painting. Air vents on roof with mesh (size and quantity shall be designed). Mechanical Level indicator shall be provided near internal ladder opening. Provision for Level transmitter for SCADA integration by others (50 mm. stainless

steel nozzles (Grade 316L), one on wall at bottom level and one on roof near wall, ends shall be blind flanged. Stainless steel vertical guide pipe supported on the wall, to be provided up to bottom of tank for the roof nozzle).

Stainless steel insert plates (Grade 316L) on wall internally and G.I. insert plates on wall externally for fixing ladder, mechanical level indicator, level transmitter guide pipe supports etc. (Drilling shall be avoided wherever possible on the walls of the tank)

Builder's work related to tank earthing, lightning protection works and lighting. Complete embedded items associated with tanks. Platforms, walkways, cross over, handrails including support system as required for

safe operation and maintenance works. Hydrostatic testing of tank as per standards/specifications. Cleaning, flushing, disinfection and bacteriological testing at approved laboratories,

of tank and its piping. Inlet valves – MOV shall be provided in chamber or in pipe trench/rack either

vertically or horizontally and manual valve shall be either horizontally or vertically on line. Outlet and other valves, flow meter, etc. shall be provided in valve chambers.

Water retaining construction shall comply with this specification and BS 8007. As this specification has been particularly designed to produce an impermeable concrete, it will meet the requirements of BS 8007 for concrete quality.Where construction or Control joints are provided in floors, waterstops shall be used to ensure watertightness under a head of water equal to the height of the tank. In Control joints, an acceptable joint sealant shall be used in addition to the waterstop to prevent entry of foreign material into the joint and to ensure its performance. The slab at the joint may be thickened to allow additional space for the waterstop and reinforcement. For a restrained joint, the reinforcement shall be continuous through the joint. Alternate designs with nonrestrained (unbonded) joints are acceptable, provided the watertightness criteria are met.

8. MATERIALS 8.1 General

The materials used in the construction of the tanks shall conform with those contained in the relevant sections of this Specification and shall be compatible with the storage of potable water. The Contractor shall obtain the Engineers’ approval for all the materials to be used in the construction. If requested by the Engineer the samples of such materials shall be tested. If

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materials are observed to be not suitable and rejected by the Engineer, the Contractor shall remove them from the site. The contractor shall submit representative samples of the materials he proposes to use. Engineer shall approve the sources of such materials and shall supervise the necessary tests conducted on the representative samples, in accordance with the stipulated standard tests for the respective material, in order to ascertain their compliance with the requirements specified herein, prior to use and importation to the Site of the works. All tests shall be performed by the Contractor at his own expense under the directions of Engineer

8.2 Impervious Membrane Concrete shall be cast into approved 1000 gauge polyethylene sheet laid over the blinding concrete. Overlap shall be 150 mm and the sheeting shall extend 150 mm beyond the edge of all foundations, floor slabs and paving.

8.3 Cement OPC/MSRPC type cement shall be used. The ordinary Portland and sulphate resisting cement shall comply with all the requirements of BS 12 and BS 4027.All cement shall be certified by the manufacturer as complying with the requirements of the appropriate specification. The Contractor shall, obtain the manufacturer's certificate for any consignment as soon as possible after delivery.

8.4 Aggregates The fine and coarse aggregate shall be durable hard material, free from excessive chlorides and sulphates. The coarse aggregate shall be of crushed stone or Natural River aggregate and shall be graded to fulfill the conditions of standard table of percentage by weight passing through B.S. sizes. The sand shall contain no salts. It deemed necessary by the Engineer, it shall be washed before use. The sand shall be graded to confirm with the Fuller curve or any other internationally recognized standard curve guaranteeing optimum concrete quality. The aggregates shall be brought from approved sources.

8.5 Water

The water used for making concrete, curing of concrete mortar, grout, or similar purposes shall be clean, fresh and free from injurious amounts of oil, acid vegetable or organic matter or any other deleterious substances in suspension or solution.

8.6 Admixtures Calcium Nitrite shall be added to the concrete in order to provide resistance to chloride attack and additional protection to the reinforcement. A waterproofing admixture shall be used for water retaining structures and buildings with basement below ground water table. Admixtures shall not be used without the approval of the Engineer.

9.CONCRETE

The strength requirements for each grade of concrete proposed in the design shall be proven by means of preliminary trial tests as specified. The minimum cement content shall be 450kg/cu.m The maximum free water cement ratio shall be 0.35. These figures shall be revised, if the sulphate content of the soil is greater than 0.5% (test SO3), and also, as per the prescribed mix design.

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9.1 Ready Mixed Concrete

Ready mixed concrete may only be used with prior approval of Engineer, who shall be given the opportunity to inspect the suppliers plant before giving acceptance. The concrete shall meet all the requirements of the Specifications, including trial and on Site testing.

Concrete shall be delivered from the ready mixed plant to the Site in truck mixer units complying with BS 4251, ‘Truck type concrete mixers'. Delivery trucks will not be permitted to discharge concrete not later than 60 minutes after batching at the plant. Agitation of the concrete shall continue from the batching plant to and during the time of discharge.Ready-mixed concrete as defined in BS 5328, batched off the Site, may be used only with due written approval of the Engineer and shall comply fully with all requirements of the Contract. The concrete shall be carried in purpose made agitators, operating continuously or truck mixers. The concrete shall be compacted and in its final position within 2 hours of the introduction of cement to the aggregates, unless otherwise approved by the Engineer. The time of such introduction shall be recorded on the delivery note together with the weight of the constituents of each mix. When truck-mixed concrete is used, water/super plastiziser shall be added under supervision, either at the site or at the central batching plant, with due approval of the Engineer, but in no circumstances shall water be added during the transport.

Unless otherwise approved by the Engineer, truck mixer units and their mixing and discharge performance shall comply with the requirements of BS.4251. Mixing shall continue for the number and rate of revolutions recommended in accordance with item 9 in Appendix B of BS.4251 or, in the absence of the manufacturer's instructions, mixing shall continue for not less than 100 revolutions at a rate of 7 revolutions per minute.

9.2 Workability The concrete shall be of such consistency that it can be readily worked into the corners and angles of the formwork and around reinforcement without segregation of the materials or bleeding of free water at the surface. On striking the formwork it shall present a face, which shall be superior to the standards laid down in later clauses of this section.

9.3 Transportation

The concrete shall be discharged from the mixer and transported to the works site. The Contactor shall place suitable measures to prevent adulteration, segregation or loss of ingredients and ensure that the concrete is of the required workability at the point and time of placing.

9.4 Placing

The concrete shall be placed in the positions and sequence indicated on the drawings, in the specification or as directed by the Engineer within two minutes of mixing. Except where otherwise directed, concrete shall not be placed unless the Engineer or his representative is present and has previously examined and approved the positioning, fixing and condition of the reinforcement and of any other items to be embedded, the cleanliness, alignment and suitability of the containing surfaces, and the adequacy and position of plant. The concrete shall be deposited as nearly as possible in its final position and in such a manner as to avoid segregation, displacement of the reinforcement, formwork or other embedded items. Placing shall be continuous between specified or approved construction joints. Works shall be brought up to full thickness in 500mm maximum compacted layers as the work proceeds.

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Where chutes are used to convey the concrete, their slopes shall not be such as to cause segregation and suitable spouts or baffles shall be provided to avoid segregation during discharge. Concrete shall not be allowed to fall freely from more than 1.5 meters except with the approval of the Engineer. Where pneumatic placers are used suitable baffles or hoppers shall regulate the velocity of discharge where necessary to prevent segregation or damage and distortion of the reinforcement, other embedded items and formwork caused by impact.Concrete shall not be placed in standing or running water unless so specified or approved.

9.5 Compaction of Concrete: The concrete shall be fully compacted throughout the full extent of the layer. It shall be thoroughly worked against the formwork and around reinforcement and other embedded items, without displacing them. Successive layers of the same lift shall be thoroughly worked together.

9.6 Vibrations Unless otherwise directed by the Engineer, approved power driven vibrators of the immersion type shall be used. They shall be inserted at such distances apart or applied in such a manner as will ensure that the concrete is satisfactorily and uniformly compacted. The Contractor shall ensure that a sufficient number of vibrators are on hand at all times including allowance for breakdown of vibrators.Vibrators shall penetrate the full depth of the layer and where the underlying layer is of fresh concrete, shall enter and re-vibrate that layer to ensure that successive layers are well knitted together. Over-vibration, causing segregation, surface laitance or leakage through formwork, shall be avoided; immersion vibrators shall be withdrawn slowly to prevent the formation of voids. Vibrators shall not be used to work the concrete along the forms, or in such a way as to damage formwork or other parts of the structure, or displace the reinforcement or other embedded items.

9.7 Curing Concrete shall be protected during the first stage of hardening from the harmful effects of sunshine drying winds, cold, rain or running water. The protection shall be applied as soon as practicable after completion of placing by one or more of the following methods, as approved. The concrete shall be covered by a layer of sacks or canvas or Hessian or straw mats, or similar absorbent material, or a layer of sand and are constantly kept wet.Alternatively after thoroughly wetting, the concrete shall be covered with a layer of approved waterproof paper of plastic membrane kept in contact with the concrete. Except in case of surface to which concrete has subsequently to be bonded, the concrete may be the application of an approved liquid curing membrane. Application shall be made by low-pressure spray in accordance with the manufacturer's instructions. On vertical surfaces, the curing membrane shall be applied immediately after removing the formwork. The curing of the concrete shall be maintained for at least one week.

9.8 Cube Test Work Procedures

Samples of concrete for tests shall be taken and cubes made to the agreed frequency. Normally for each grade of concrete, 6 cubes shall be made for each 20 cubic meters of concrete or part thereof, in each day's work. The Engineer may reduce this number of cubes to be tested, if consistently satisfactory results are obtained, or increased up to a maximum of 12 when consistency is not satisfactory and additional tests are required. The procedure for making and testing the cubes shall

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be the same as that approved for the preliminary test cubes. The laboratory shall submit the reports of all tests made to the Engineer directly within 24 hours of the cubes being tested.

9.9 Concrete Cores Where requested by the Engineer, cylindrical core specimens shall be cut from the hardened concrete in the works for the purposes of examination and testing. The cutting equipment and the method of doing the work shall be approved. Prior to preparation for testing, the Contractor shall provide specimens for examination by the Engineer.Testing of the core shall be in accordance with approved standards. The results of such tests shall not nullify the fact of non-compliance with the specification.

9.10 Mix Design 9.10.1 General

The mix proportions shall be determined after carrying out trial mixes at Site (Readymix Plant Laboratory). Trial mixes shall be carried out for each grade of concrete and all testing shall be in accordance with the relevant part of BS 1881. The proposed mix design shall achieve the required strength and durability and shall comply with the recommendations of BS 5328. The concrete shall have maximum compaction, and the water/cement ratio shall not exceed 0.35 for all water retaining structure works and 0.40 for other structural works.

9.10.2 Concrete for Water Tank The mix design requirement for the water tank concrete shall be as follows to achieve a low water absorption and minimize the water penetration. The water absorption shall not exceed 1.5% and water penetration shall be less than 08 mm and Rapid Chloride Penetration shall not exceed 1000 Coulombs.

A] Mix Design for Water Tank [Raft, Wall, Columns, Beams, Thrust block]:

Grade of concrete : 50 N/mm2 Maximum W/C ratio : 0.35

Mix Proportion / M3

OPC/MSRPC } 210 Kg.

GGBS } Triple blend 210 Kg

Micro Silica } 30 Kg.

20 mm Fully crushed Based on all In grading 10 mm Fully crushed

5 mm Washed sand

Dune Sand

Super Plasticizer 10 Lit

Calcium Nitrate 5 Lit

Durability Parameters Water absorption : Less than 1.5% Water penetration : Less than 08mm RCP : Less than 1000 coulombs Required slump : 150 +/- 25mm at site Max. Temp. at site : 30oC at site.

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B] ALTERNATE MIX DESIGN FOR WATER TANK

Mix Design for Water Tank (Raft, Wall, Columns, Beams & Thrust block) Triple Blend Concrete with Crystalline Water Proofing Compound.

Grade of Concrete – 50N/mm2 Max. W/C Ratio – 0.35

MIX PROPORTIONS / M3

OPC/MSRPC 330 KG

GGBS 100 KG

Micro Silica 20 KG

Water Proofing Powder Pudlo or equivalent 8 to 10 KG

10mm Fully Crushed

Based on all in grading

5mm Washed Sand

20mm Fully Crushed

Dune Sand

Crystalline Water Proofing Compound As Required

Super Plastisiser 8 to 10 Ltr.

Durability Parameters Water Absorption [ WA ]– Less than 1.2% Water Permabilities [ WP ]– Less than 8mm RCP – Less than 1000 coulombs

Note:

1. For each raft segment and each wall lift concrete, one set of durability test shall be conducted.

2. 7 days and 28 days compressive strength test shall be conducted. 3. If required, cement content and calcium nitrate content test shall be conducted.

9.10.3 Concrete for Miscellaneous Works

A] Mix Design for Blinding Concrete

Grade of Concrete : 20 N/mm2 Max. W/C Ratio : 0.50

Mix Proportion / M3

SRC 280 Kg.

20 mm Fully crushed Based

on all in grading

10 mm Fully crushed

5 mm Fully crushed

Dune Sand

Super Plasticizer 4.5 Lit

Note: 1. For sub-structure and super structure, one set of durability test shall be

conducted. 2. 7 days and 28 days compressive strength test shall be conducted. 3. If required, cement content and calcium nitrate content test shall be conducted.

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B] Mix Design for Valve Chamber/Pre-cast RCC Slab:


Mix Proportion / M3

SRC / MSRPC } 375 KG.

Micro Silica } Double blend 25 Kg.

20 mm Fully crushed Based

on all in grading

10 mm Fully crushed

5 mm Washed sand

Dune Sand


Calcium Nitrate 5 Lit

Durability Parameters

Water absorption : Less than 2% Water penetration : Less than 10mm RCP : Less than 2000 coulombs Required slump : 150 +/- 25mm at site Max. Temp. at site : 30oC at site.

Note: 1. 7 days and 28 days compressive strength test shall be conducted. 2. If required, cement content and calcium nitrate content test shall be conducted.

C] Mix Design for Screed Concrete:


Mix Proportion / M3

OPC/MSRPC 320 Kg.

Polypropylene fiber 0.90 Kg

10 mm Fully crushed

Based on all in

grading 5 mm Fully crushed

Dune Sand


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9.11 The Grades of Concrete

Characteristic Compressive Location cube strength N/ mm2

All water retaining structure concrete above and below ground including 50 foundation raft, columns, wall and any related cast in situ concrete

All other superstructure works above ground including columns, beams and 40 slabs All other sub structure works 40 including foundations, pits, trenches and piles Blinding and mass concrete fill 20 Precast and Post-tensioned hollow core slab 60 Maximum size of aggregate shall be 20 mm.

The Contractor shall carry out at his own expenses all the necessary tests (strength, durability and cement content) according to the code or standards accepted by Engineer in an approved testing laboratory.Engineer may decide to perform control tests in order to check the of any concrete works, such as core tests, etc. (destructive and non-destructive). In this case, the Contractor shall provide all material necessary to perform the tests, and the samples will be tested at the Contractor's expense in the laboratory specified by Engineer.

Note:Mix design given are to be checked by the contractor for consistency of particular grades.

Based on the given guideline, contractor to arrange trial mix test with concrete supplier before the execution of work. The proportions shown are not to be taken as final and the basic materials to be used shall not be changed. For getting maximum workability and slump specified for specialist concrete works, super plasticizer shall be used at site with the approval of Engineer.

9.12 Quality Assurance of Materials to be Used to Prepare Concrete. The main guarantee for a durable concrete of good quality, is the setting up of an effective quality assurance and control programme during construction. This programme falls within the scope of the Contractor's duties. The minimum requirements of this quality assurance programme will include : the search for good quality aggregate (sand as well as crushed stone), assurance of good quality clean potable water, low in chloride and sulphate content, and an investigation into the possible reactivity between the aggregates and the cement (alkali-aggregate reaction) which can lead to irreversible and irreparable concrete damage ("concrete cancer") notwithstanding all other measures detailed below. This quality assurance must be guaranteed with supporting documentation from suitably qualified testing laboratories.

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9.12.1 Samples and Testing of Materials Prior to commencement of concrete work, submit samples of materials to Engineer before sending them to the laboratories for testing in order to establish the probability of the materials passing tests for specified requirements. Such samples shall be in sufficient amounts to enable tests to be carried out and shall be not less than the quantities stated below:

Cement: A mixed sample of equal quantities taken from at least one bag in every twenty, totalling 50 Kgs or 112 pounds, for every batch of cement delivered to the Site.

Fine aggregate and sand for mortar: 1 cubic foot for each mix of concrete or for each size of aggregate.

Coarse aggregate: 1 cubic foot minimum for each mix of concrete or for each size of aggregate.

Reinforcing steel: Sufficient for 3 tensile tests and 3 cold-bend tests per 20 tonnes of bars or portions thereof, and for each different size or quality.

Water: Sufficient samples of water used for washing aggregates, mixing of concrete, washing out forms, and curing of concrete. Tests shall be determined by the A.A.S.H.T.O. Specification T-26 “Method of Test for quality of Water to be used in Concrete”.

Accessories: Submit one sample for each type of the following items proposed for use: Form ties, support accessories for reinforcement, binding wire, tie-hole plugs, water bars, and dovetail anchor slots.

After Engineer is satisfied that the samples with their sources are truly representative samples and sufficient quantities of these materials are readily available for the completion or all concrete work, then they shall be sent to the laboratories for testing.The Contractor shall supply and deliver to the laboratory all samples and have all laboratory tests made at his own expense. During construction, sample and test all concrete, aggregates, cement, and water as frequently as deemed necessary by Engineer. Obtain samples in accordance with BS 1881:Part 1:1970. Before concrete is placed, supply Engineer with details of concrete mixes, aggregates, additives, and sources of supply. State where each concrete mix is to be used.

9.12.2 Quality Control on Site Make all required field measurements.Employ a competent technician to establish and maintain lines and levels. Report immediately to Engineer any field dimension, which does not agree with drawings dimensions.Formwork: Do not close deep forms until reinforcement has been reviewed. Check elevations, camber, and plumbness of formwork continuously, during concreting and after, until initial set occurs using pre-installed tell-tale devices. When necessary make appropriate adjustments promptly. Report to Engineer all adjustments made after initial set. Reinforcement: Ensure that reinforcement is kept free from dirt, grease, loose mill scale, and rust. Ensure that reinforcement is complete, adequately tied, and properly positioned for cover in advance of the time scheduled for casting concrete. Strength tests: Make test cubes for standard concrete strength tests. One test is required for each 50 cubic meters, but not less than one test, for each class of concrete placed each day. Store cubes in metal lined curing boxes maintained protected from the sun until shipped to the nominated testing laboratory. Slump tests: Make slump tests with each standard strength test, each concrete truck delivery and when so directed by Engineer.

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10. REINFORCEMENT

Reinforcing steel shall be high yield steel of specified characteristic strength fy 460 N/mm2 following BS 4449 or BS 4461 or ASTM A615 M for all diameters unless otherwise noted.Reinforcement shall be obtained from an approved source. It shall comply with the following standards or approved equivalent BS 4449 or ASTM A615 M, latest edition.In case the steel reinforcement is subject to welding, the steel shall strictly comply with BS 4449 or 4461 or approved equivalent relevant to weldable reinforcement steel. Moreover, the Contractor shall submit the procedure for welding, type of electrodes, welder qualifications, etc. for Engineer’s approval.

11. POST-TENSION ELEMENTS

Tendons Reinforcing tendons shall be made up of strand types, nominally 13 mm or 15 mm, conforming to BS 5896:1980 or ASTM A416-85. Tendons shall be used within ducts and shall be pressure grouted after tensioning. Properties: Common sizes: 12.7mm, 15.24mm, 9.53mm, 12.5mm, 15.7mm & 9.3mm. Uncoated low relaxation 7 ply strand for pre-stressed concrete is governed by ASTM or BS Standards. The advantages of Low Relaxation Stranded Wires are as follows:

Low stress loss due to a low relaxation property. Low relaxation loss under an elevated and ambient temperature. High elasticity and yield strength because of stress-relieving process. Straightness resulting ease of handling. Cost saving. Anchors

Stressing anchors shall be comply with BS 4447 requirements or its equivalents. Anchor blocks shall be made of cast iron and galvanized. The size and type of the blocks shall depend on the number of strands used. Extra reinforcement shall be provided to take local stress within the concrete.Equipment used in the stressing works shall be supplied by the manufacturer, supplying the anchorages.Stressing jacks shall be calibrated and test certificates shall be issued by the post-tensioning system manufacturer. The test certificates shall remain valid during the entire period of the works.

Tendon installation Tendon shall be placed within the walls in ducts to form circular bands of reinforcement. The ends of the tendons shall be anchored into pilasters (or buttresses) located at regular intervals around the perimeter of the wall. The ends of each tendons shall be anchored into alternate pilasters and shall be just over one quarter or one third of the circumference of the tank in length.

Stressing Alternate pairs of opposing pilasters shall be fully stressed progressing from the bottom of the pilaster to the top. On completion of stressing all tendons shall be trimmed close to the anchor, and the pocket filled with non-shrink mortar.

All tendon installation and stressing work must be supervised by the system manufacturer's engineer.

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Post Tensioning Ducts (Sheathing) Requirements: Duct must withstand the loads during transportation, storage, lifting, installation,

casting. Duct cast into concrete should withstand at least 3.0m of concrete fluid pressure. Duct must avoid the leakage of the grout or concrete in and out. Duct must have a limit for deflection; duct with a diameter greater than 50mm shall

not deflect more than 75mm when a 6.0m length is supported at its ends. Ducts shall not dent more than 3mm under a concentrated force of 0.45KN applied

using a 13mm diameter reinforcing bar. Duct shall be corrugated for better bonding with concrete and for reducing the

contact area with the Post-Tension steel and subsequently reducing the friction losses.

The inside diameter of the duct to be filled with portland-cement grout shall be a minimum of 3/8 in. (9.5 mm) greater than the nominal diameter of the bar tendon, or the inside area of the duct shall be twice the area of the prestressed strand tendon.

Duct Material:

Duct material for fully bonded tendons shall be semiflexible steel or corrugated polyvinyl duct.

In addition to the requirements the duct shall be capable of transferring the stress from the tendon by bond or shear through the duct to the concrete along its full length.

Duct material for grouted tendons shall be flexible or semiflexible spiral-wound corrugated sheet metal steel or polyvinyl chloride pipe or tubing and shall be sufficiently strong to retain its shape and location during placement and vibration of the concrete.

If the duct is to be filled with pumped epoxy, the annular space around the tendon may be reduced to the minimum size that will permit easy insertion of the tendon.

Ducts shall be so constructed and sealed as to positively prevent the entrance of cement paste from the concrete and shall be equipped with suitable fittings and tubing at both ends for flushing and pumping the grout or epoxy.

Norms Requirements: ACI-99 318M/318RM-280 section 18.17 BS EN 523, EN 524 Acceptance standards

for post tensioning systems section 5.1 and 6.1.8 Sheets as per ASTM A527/653 G90 The design shall consider the pre-eminent seam design which provide leak

tightness and extra rigidity to the duct. The corrugation design guarantees extra rigidity, in addition to extra bondage with

concrete. The duct dimension shall be minimum 75mm, fits to all major Post Tensioning

Systems. The duct shall produced in lock forming quality galvanized steel. The galvanization shall be of high quality. The coupler size and shape perfectly fit with the duct; the gap between the duct and

the coupler is uniform and does not exceed 2mm. The duct will go through the different required tests (lateral load resistance test,

flexural behaviour test, water tightness test..) a mill certificate and tests results shall be submitted along with the supply.

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The semi-rigid grout-tight sheathing is manufactured from 36mm steel strip. 0.2-0.4mm thickness without any welding. It shall be very rugged, lightweight, of standard length of 5m and provided with screw-type couplers. The couplers are usually cut from sheath which is 5mm greater in diameter and the joints between anchorage/sheath and sheath/sheath must be waterproofed by using sealing tape. When installing the duct, adequate support must be provided to prevent displacement during concreting operations.

Fixing Tips: The coupler shall be centered. The edges shall be cut in V shape to fit in small anchors Always to move in bundles of minimum 3 ducts To cover the stock to avoid the intrusion of sand inside the ducts To use reinforced duct tape for sealing the duct at connections Sealed duct shall not be exposed to the sun for more than 24 hours, depending on

the duct tape quality and the weather conditions. Always to apply duct tape on clean duct. Perforate for vent pipe with a sharp piece of stele only when the duct is full. Spacing of tendon supports: 0.8 to 1.2m conventional steel ducts. Minimum curvature radius: 2.5m (vertical profile) 8m (horizontal profile) Minimum straight length at anchorage: 0.8m Friction losses can vary fairly widely from one tendon to another and from one

structure to another. This depends on factors such as surface condition of strands, duct types and surface condition, material properties, installation methods and on-site workmanship.

Duct Grouting: Grout shall be injected under pressure in tendon ducts from the duct terminal. Openings or voids in the anchorages shall be plugged to prevent grout leakage and

the ensuing loss of pressure during the grouting operation. Grout shall be injected into the tendon duct immediately after the tendon has been

stressed. When epoxy is used as encasement for the tendons, the application will be similar

and shall be as recommended by the manufacturer.

12. SHUTTERING/FORM WORK/SCAFFOLDING SYSTEM

Shuttering system shall be made of high quality material with hi tech methodology from well reputed firms. The shuttering system shall be either of slip form or of lifting type based on the tank design and requirement of FEWA. Forms shall be designed and so constructed that the concrete can be properly placed and thoroughly compacted and that the hardened concrete shall conform accurately to the required shape, position and level, subject to the tolerance and to the standards of finish specified. When concrete is to be vibrated, special care shall be taken to maintain the stability of the formwork and the tightness of the joints during vibrating operations. Due allowance shall be made for any deflection which will occur during the placing of concrete within the forms.

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Design calculations for form work and its supporting arrangement both for the walls and the roof of the storage tank shall be submitted by the Contractor for approval for details of the methods and materials proposed for the formwork to each section of the work. Details of formwork to produce special finishes are to be submitted for approval in writing before any materials are brought on to the site.Forms shall be constructed from sound material of sufficient strength, properly braced,strutted and shored to ensure rigidity throughout the placing and compaction of the concrete without visible deflection. Forms shall be so constructed that they can be removed without shock or vibration to the concrete.FEWA/Engineer shall approve the material and position of any ties passing through the concrete. The whole or part of the tie shall be capable of being removed so that no part remaining embedded in the concrete shall be nearer than the surface of the concrete than the specified thickness of cover to reinforcement. Any holes left after the removal of ties shall be filled with concrete or mortar of approved composition. All joints shall be close fitting to prevent leakage of grout and cement water and at construction joints the formwork shall be tightly secured against previously cast or hardened concrete to prevent stepping or ridges to exposed surfaces. Panels shall have true edges to permit accurate alignment and provide a neat line with adjacent panels and at all construction joints. All panels shall be fixed with their joints either vertical or horizontal, unless otherwise specified or approved. When chamfers are to be formed the fillets shall be accurately cut to size to provide a smooth and continuous chamfer.The category of formwork to be used for each concrete item will be indicated on the drawings.If no mention is made, it is assumed that category 1 formwork will be used. All shuttering and moulds with supporting false work and staging shall be of metal or wood, and shall be of sufficient strength and rigidity. It shall be jointed and shall not be liable to get out of shape. The shuttering shall be so designed as to permit its removal for re-uses without damage to the concrete. The surfaces in contact with the concrete shall be perfectly flat. The shuttering and moulds for forming the face of exposed concrete shall be of especially smooth construction.Smooth, oiled, nailed on plates shall be used. All shuttering shall be perfectly cleaned out before concreting. A shutter release compound shall be applied on the wood to prevent the concrete from adhering to the shuttering.All shuttering shall exhibit a smooth facing finish. The cavities in front of jointing shall not exceed 2 mm. Excessive protrusions shall be ground off. All external edges of exposed concrete (walls, beams, girders, columns, foundations, etc.) shall be chamfered and formed with 20mm chamfer strips.

13. PROTECTION OF THE CONCRETE

13.1 Blinding or Mudmat Concrete Unless otherwise shown on facility design drawings, all foundations shall be placed on 50 mm thick blinding or mudmat concrete. Prior to placing this concrete, the subsoil shall be well consolidated compacted and be free from loose material in accordance with the Engineering Group Specification entitled ‘’Earthworks, Materials and Construction’’ (Number 015-SH-1002).

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13.2 Surfaces Below Ground Level Water Proofing, tanking for Structural RCC Works

All structural concrete for tanks and buildings in contact with the soil shall be covered by waterproofing membrane with protection layer Waterproofing membrane shall be self adhesive, cold applied, approximately 4 mm thick polyester fabric reinforced. The membrane shall incorporate a selvedge to provide a bitumen to bitumen seal. Performance and testing of characteristics shall be as follows:

Property Test Method Typical Results

Elongation at yield ASTM D638 59%

Adhesion to primed concrete ASTM D1000 7.0 N/mm to self (handling coating) ASTM D1000 6.0 N/mm to self (selvedge) ASTM D1000 7.0 N/mm Moisture vapour ASTM E96 hrs. 0.32 g/m2/24 transmission rate

Prior to application of the tanking membrane to concrete, a compatible primer will be used, coming from the same manufacturer as the membrane. The membrane will be applied on a concrete support, being structural or blinding concrete. The waterproofing membrane will also be protected from damage arising from any cause. The protective measures to suit the various exposure conditions of the concrete shall be submitted for Engineer’s approval.

14. FINISHES

14.1 Foundations The Surfaces of the tank foundations shall be protected by the application of a bituminous waterproof membrane meeting the requirements contained in section waterproofing. 14.2 Internal finishes:

All the internal surfaces including the floor, walls, columns and soffit of roof shall be completely coated with a cement based two-component polymer modified waterproofing coating of total thickness of minimum 2000 microns of certified (WRC or equivalent) potable water compatible quality.

Complete details of the coating system to be used by the Contractor shall be submitted to FEWA for approval. The coating shall be applied strictly in accordance with the manufacturer's instructions and complying with section CS11, Painting/Glazing/Tiling and as per GS 01, painting and protective coating. The first coat shall be applied in vertical direction either by brush/roller or by pressure spray gun and the second coat shall be applied after curing period of the first coat in horizontal direction either by brush/roller or by pressure spray gun .The protective coating shall be guaranteed for a period of 5 years from date of provisional taking over.

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14.2A Internal Finishes [ Alternate Method ] For water retaining structures where a continuous waterproofing is required a waterproofing admixture shall be added with the approval of the engineer. In this case internal coating system is not required as leak proof surface can be maintained with the addition of this admixture.

The protection of concrete from disintegration/deterioration due to salt attack/withering shall be eliminated and water tightness shall be ensured permanently by water proofing system of advanced induced crystalline waterproofing cement based additive in the concrete mix. The crystalline water proofing system shall work in any situation irrespective of positive action or negative action and thereby eliminating the membrane/coating method. Crystallization technology in concrete shall not affect the strength and durability of concrete.

The crystalline waterproofing additive shall be non stearate, non silicate, sodium free, hydrophilic, self sealing in powder form with warranty of minimum 15 years of water proofing quality . The rate of addition of admixture shall be 2% by mass of the cementatious content so that the it shall promote chemically the total hydration through a catalyst form of water bearing crystals in hardened concrete. 14.3 External finishes:

14.3.1 Walls The external surfaces of the walls shall be finished with a plastoelastic one component protective

coating of total thickness of minimum 400 microns based on ethylene co-polymer dispersion which allows passage of water vapour, complying with section CS11, Painting/Glazing/Tiling and as per GS 01, painting and protective coating.Complete details of the coating system to be used by the Contractor shall be submitted to FEWA for approval. The coating shall be applied strictly in accordance with the manufacturer's instructions and the requirements of Painting and Protective coatings. The first coat shall be applied in vertical direction either by brush/roller or by pressure spray gun and the second coat shall be applied after curing period of the first coat in horizontal direction either by brush/roller or by pressure spray gun .The protective coating shall be guaranteed for a period of 5 years from date of provisional taking over.

14.3.2 Roof The external surface of the roofs shall be made waterproof by the application of a high performance

rubber/ bitumen membrane which shall be solar reflective and resistant to aggressive environmental and ozone attack.

The roofing membrane shall be applied according to the manufacturer's instructions by a specialist

Contractor, who shall provide a written guarantee covering the satisfactory performance of the roofing membrane for a period of 10 years. All roof collar flashings of roof penetrations for pipes, ventilators, etc. shall be installed at the same time as the waterproofing membrane.

15. GROUTING, SEALING AND MISCELLANEOUS

Non-shrinkage grouting of a type approved for its particular application i.e., static or dynamic loadings under steel base plates and bearing plates and as required to fill in pockets left in concrete walls or slabs. It shall be ready to use non-metallic aggregate product requiring only the addition of water at the Job Site and shall have the following qualities.

Capable of producing a fluid grouting material;

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Compressive strength of grout (50 mm cubes) shall not be less than 28 N/mm2 at 7 days and 42 N/mm2 at 28 days. Store, mix and place as specified and in strict accordance with the manufacturer’s instructions.

Polysulfide sealant shall be a two- (or more) component elastomeric compound of the appropriate type meeting the requirements of ASTM C920, type M, and shall have permanent characteristics of bond-to-metal or concrete surfaces, flexibility, and resistance to extrusion caused by hydrostatic pressure. Air-cured sealants shall not be used. The grade and class shall be appropriate for the intended use as recommended by the manufacturer.

15.1 Grouting Materials Non- shrink grout of expansion coefficient 4-5% shall be used.

Advantages: Expansion system compensates for shrinkage and settlement in plastic state. Develops high early strength without the use of chlorides. High ultimate strength and low permeability ensure the durability of the hardened

grout Compatible with ordinary Portland Cements complying to BS 12 and ASTM C150.

Cable Grout shall contain admixture containing expansive cement which impart controlled expansion in the plastic state whilst minimizing water demand. The material is designed to allow uniform mixing, and eliminates unwanted segregation and bleeding.

16. WATER BAR

Waterstops shall be extruded from a high grade PVC compound, and shall have a minimum width of 24 cm. For Water retaining structures the minimum width shall be 30 cms. The type and manufacturer shall be submitted for Engineer’s approval.All intersection pieces shall be prefabricated by the manufacturer and only welding of butt joints in running lengths will be allowed to be carried out on the Site.The Site welding of butt joints shall be executed by using the manufacturer’s material and work shall be done by competent and trained personnel only. The manufacturer’s instructions shall be strictly adhered to.The wings of the water stops shall be formed with corrugations or bulbs to achieve a good bond. Moreover, the water stops shall conform to the following requirements:

The tensile strength shall be 13.7 N/mm2 when tested in accordance with ASTM D 412. The ultimate elongation shall not be less than 250% when tested in accordance with

ASTM D 412. The tear resistance shall not be less than 2 N/mm2 when tested in accordance with

ASTM D 624. The material shall not crack when tested in accordance with ASTM D 746. Under accelerated extraction, the tensile strength shall not be less than 8 N/mm2 and

the ultimate elongation shall not be less than 200%.

Waterstops shall be centered in the joints and secured by split forms or other acceptable means to ensure positive positioning. Horizontal waterstops that are accessible during concreting shall be secured in a manner that allows them to be bent up while concrete is placed and compacted underneath, after which the waterstop shall be allowed to return to position and concrete immediately placed over the waterstop. Waterstops that are not accessible during concreting shall be positively tied in such a manner that bending in either direction is prevented. Judicious use of

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nails or “hog-ties” driven through the edges of waterstops to facilitate placing and tying may be permitted. All waterstops shall be spliced by heat welding in a manner that ensures complete continuity as a water barrier.The water stops shall be installed so that they are securely held in position during the placing of concrete, which shall be fully and properly compacted around the water stops to prevent voids or porous areas and to obtain proper bond between the water stops and the concrete.Adequate clearance between the reinforcement and all the water stops shall be kept to permit proper compaction of concrete. Supports shall be provided and suitable precaution be taken to protect the water stops during the progress of the work. If, after placing concrete, water stops are out of position or shape, the surrounding concrete shall be removed, the water stop reset, and the concrete replaced, all at the Contractor’s expense.No holes or nailing shall be made through any water stop for fixing purposes. Jointing by lapping two pieces of water stops shall not be permitted.The free edges of water stops shall at all times be protected from direct sunlight.

17. JOINTS IN WATER RETAINING STRUCTURES 17. 1 Construction Joints: Concreting shall be carried out continuously up to construction joints, the position and arrangement of which shall be indicated on the drawings and approved by the FEWA/Engineer. All construction joints are to be formed square to the work. Key ways are to be formed in all horizontal and vertical construction joints except where ordered to be omitted by FEWA/Engineer.The joint shall be sealed at the liquid face(s) where no special seal coating of that face is specified by a water proof sealant. Pipe support pedestals on slabs shall have reinforcement firmly anchored into the supporting slab and shall have carefully prepared construction joints to assure adequate bond and connection. When work is resumed on a surface which has set the whole surface shall be thoroughly roughened or scabbled with suitable tools so that no smooth skin of concrete that may be left from the previous work is visible and that all aggregates and solid matrix around them are exposed. It shall be cleaned of all loose and foreign matter and laitance and washed with water immediately before placing the fresh concrete, which shall be well compacted against the joint. The contractor shall obtain approval of FEWA/Engineer, prior to the commencement of concreting, upon the sequence of placing concrete and the positions of vertical and horizontal joints whether shown or not in the drawings. In general, slabs in excess of 12 meters in length or width and walls exceeding 3 meters in height shall not be poured in one operation and subsequent adjacent bays shall not be concreted within 7 days. As an alternative to alternate bay construction for blinding, shrinkage gaps of up to 1 meter in width may be left at 6 meters intervals; the shrinkage gaps shall not be concreted until concrete on all sides is at least seven days only. If any deleterious materials have come into contact with the concrete of the construction joint the concrete shall be cut back to such depth shall order by FEWA/Engineer and the roughened surfaces shall be thoroughly cleaned by compressed air and water jets or other approved means and brushed and watered immediately before depositing concrete. If so ordered the roughened surface shall be coated with a layer of stiff neat cement grout or special bonding agent of adequate thickness prior to placing the new concrete.

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Immediately after striking the formwork the construction joint shall be examined to ensure that the integrity of structure has been maintained. If doubt exists over the soundness of the joint, then the Contractor shall take all steps considered necessary to investigate and remedy any honey combs/ defects, to the approval of FEWA/Engineer. No construction joint shall be formed between a slab or beam and a wall on the plane of wall face but shall be set into the wall to a depth of a fifth of the overall wall thickness. Special care shall be taken to ensure that the concrete is well worked against the embedded parts of the strips and is free from honeycombing. Precautions are to be taken to protect any projecting portions of the strips from damage during the progress of the Works and in the case of rubber and plastic from light and heat.

18. PRECAST CONCRETE

18.1 General The requirements of this specification and BS 8110 shall be observed for precast concrete, in addition to those indicated on the contractors drawing and the following relating to precast work in particular. However, removal times for formwork may be reduced by agreement between the approved manufacturer and the company. The exposed surfaces of precast concrete units shall be in accordance with requirements

18.2 Marking All units shall have marked on a face which will not be exposed in the permanent works, the date of manufacture and such distinguishing letters or numbers as are required to identify the work.

18.3 Curing, Maturing and Stacking The production schedule shall allow for curing precast concrete in accordance with this specification. Slinging, transporting, stacking and installation shall only take place when concrete strengths designed for these purposes have been attained. Steam curing may be permitted. The contractor shall submit the steam curing cycle for company approval.

18.4 Cement/Sand Mortar Cement/sand mortar for bedding and jointing precast members shall be of equivalent strength, quality and colour to that of the concrete member being bedded or jointed. Cement/sand mortar shall be mixed in small quantities and used immediately. Attention shall be paid to compacting the cement/sand mortar to prevent the formation of voids and air pockets.

19. PRE-CAST HOLLOW CORE SLAB

Pre cast hollow core slabs for roof shall be in accordance with the design for the particular span required.For circular tanks it shall be designed for the maximum span. Hollow core slab shall be from standard manufacturer with high quality finish and strength. The hollow core slabs shall be pre-cast, pre-stressed, factory finished products without cracks and honeycomb. The minimum strength required for pre-cast hollow core slab shall be 60 N/mm2. The tendons used shall be of high tensile strength with single strand pattern. The end of the hollow core slab shall be wire cut and shall be filled with thermo-cool material.

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Slab post-tensioning enables deflections and cracks under service conditions to be kept under control. Post tensioning increases the concrete durability due to the presence of the concrete always under compression stresses. The structural simplification giving also an increase of free space, leads to an overall reduction of cost. This also comes from the reduction of steel placed inside slab and time needed for construction.

The main advantages of the System are as follows:

Reduction in slab thickness Larger spans with reduction of columns Reduction in slab weight High limitation of crack widths High deflection limitation Reduction of steel reinforcement and arrangement simplification High deflection limitation due to concrete shrinkage and creep The hollow-core slab shall meet BS-5896 requirement LRPC standards.

Mix properties:

W/C ratio 0.32 (max.) Compressive strength : 60N/mm2

Total cement content 405 kg

390 kg OPC 15kg Microsilica

Durability Parameters. Water absorption : 2% max. Water penetration: 15mm max.

RCP : 1000 columns max.

20. ELASTOMERIC BEARING PADS (NEOPRENE PAD)

The neoprene pad shall be provided over the tank wall in order to provide seating for pre cast hollow core slab/solid slab roofing. The Neoprene Pad shall be made of high quality, high strength, heavy duty rubber compound. Tensile strength Min. : 15.5 Mpa Thickness : 20mm a minimum elongation of 500 percent, a maximum compressive set of 50 percent, and a hardness of 40 to 50 durometer according to ASTM D2240. Neoprene bearing pads shall contain only virgin crystallization-resistant polychloroprene as the raw polymer and the physical properties shall comply with ASTM D2000, line call-out M 2 BC 410 A1 4 B14 for 40 durometer material. Bearing pads shall be positively positioned prior to roof slab placement and secured with an approved adhesive. Nailing of pads shall not be permitted unless the pads are specifically designed for such anchorage and nailing does not restrict lateral deformation. Where bearing pads are used, the tank wall shall be free of all obstructions that would prevent free radial movement at the joint.

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21. MAIN TECHNICAL ELEMENTS TABLE Technical Specifications for Cast in Situ Pre stressed Circular RCC Water Tanks (Horrizontal Post Tension Wall)

Item Specification

Concrete (Raft/Wall/Column/Beam)

Grade-50 N/mm2, W.C.ratio-0.35 - GGBS/micro silica con with calcium nitrate

Reinforcement Steel Type-2 - 460 N/mm2

Hollow Core precast roof slab HC-260 -320

Formwork Curved - Vertical Lifting/SLIP FORM

Sheathing Corrugated Galvanized 50-75mm /or PVC pipe

Anchor blocks Galvanized Mild steel

Tendons 12.7 mm 7 ply - Low relaxation strands.

Grout 5% expansive grout + chilled water or 2 part water insensitive epoxy

Roof Screed Cement concrete with polypropylene fibers.

Water barrier (Tie rod) Mild steel (Galvanized)

Water bar PVC 13.7 N/mm2 (Tensile)

Neoprene pad PVC 20mm.

Internal Cementatious coating 2 Component Polymer - 2000 microns.

External Cementatious coating Plasto-elastic - 1 Component - 1000 microns.

W/P membrane (foundation) 4mm bitumen self adhesive membrane with built in protection

W/P membrane (roof) 3mm Asphaltic membrane + Solar reflective sheet 1.5mm

Sealant for Construction joints Polysulphide two component elastomeric compound

22. MISCELLANEOUS WORKS 22.1 Ladders , Stairs and Handrails

Tanks shall be fitted with internal and external access ladders with safety hoops and safety handrails at the roof perimeter. Internal ladders shall be fabricated from stainless steel and

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external ladders shall be galvanized mild steel with a painted finish. For major tanks, provide spiral stair . The ladders/ stair shall be fixed on embedded plates at pre determined positions

Ladders shall meet the requirements of B.S. 4211 regarding the provision of safety cages, platforms, handrails, etc.Galvanized or painted steel may be suitable for exterior ladder construction, but more corrosion-resistant structural materials, such as aluminum, stainless steel, and fiberglass-reinforced plastic, are recommended for interior ladder construction. Flat bar stock, pipe, and tubing have been commonly used for ladder stringers.Normal rung spacing is 12 in. (300 mm), and the distance from the floor or landing to the bottom rung of interior ladders should be the same as the rung spacing. Exterior ladders should be provided with hinged plate covers or other devices, extending far enough aboveground to discourage unauthorized climbers. The cover or other device would be unlocked and swung aside for entry by authorizedpersonnel.Exterior stairs should be fitted with handrails and landings at intervals specified by OSHA.

22.2 Access Covers Access to the internal ladder shall be provided by means of an access cover set into the roof. Grip bars shall be provided on roof to facilitate smooth entry into the tank. Three further removable covers shall be set into the roof to provide additional ventilation during maintenance operations. The size of the covers shall be 800 x 800 mm. minimum tanks shall have minimum three access covers. The access cover shall be of sliding type with jacks.

22.3.Roof Opening, Hatches, and Ventilators All roof openings should be atop curbs at least 4 in. (100 mm) high. All covers should turn down at least 2 in. (50 mm) over the curbs or contain a gutter system to carry water away from the roof opening. All frames and covers should be galvanized steel, fiberglass, or aluminum at least 3/16 in. (5 mm) thick. Personnel hatches shall be at least 21/2 ft (0.76 m) square and provided with protective handrails conforming to OSHA specifications, if required.Hatch sealing and security. All roof openings, including personnel and equipment hatches, sampling points, and ventilators should be constructed so as to prevent leakage into the tank and locked to resist unauthorized entry and vandalism. Air ventilators in the roof of the tanks shall be designed to suit both the anticipated outflow and inflow conditions during tank filling and emptying. Insect net shall be provided to cover its opening GRP Air ventilators in the roof of the tanks shall be designed to suit both the anticipated outflow and inflow conditions during tank filling and emptying. Insect net shall be provided to cover its opening. Roof ventilators should be provided to admit air at a flow rate equal to the maximum tank outflow rate at pressure differentials notexceeding 2.0 in. (50 mm) of water column (equivalent to 10 lb/ft2 [4.79 kPa] of loading on the roof or dome). The exhaust capacity of the ventilator must be at least equal to the design fill rate of the tank.Ventilator screens should be protected from vandalism but must be accessible for inspection and cleaning to remove insects or airborne lint, pollen, or dust.

22.4 Level Indicators and Provision for Level Transmitters The Contractor shall submit details of mechanical indicators, which shall be fitted on the outside wall of the tanks. The indicators shall give a clear and accurate reading of the level of water in

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each tank. In addition to the mechanical indicators, the Contractor shall also provide provision for level transmitters (to be installed by others) by providing 1 no. 50 mm. stainless steel flanged pipes on wall at bottom level of tank, and 1 no. from roof fixed on the wall, up to the bottom level of tank to act as a guide pipe. The level indicator shall be placed close to the internal ladder to facilitate maintenance. Provide sampling points either on tank or between tank and inlet valve.

23. HYDROSTATIC TESTING

The Contractor shall measure and record the base level of tank before it is filled with water for hydrostatic testing. A settlement survey shall be carried out by the Contractor prior to filling for hydro testing during the filling at 25%, 50%, 75% and 100% capacity of the tank and when emptied. At the end of the tests the level of the tank base shall be re measured and the amount of settlement experienced by the tank shall be determined. After obtaining the agreement of FEWA, the Contractor shall fill the tank with potable water, to its full height at a rate not exceeding 2 meters depth per 24 hours. The level in the tank shall be maintained for a 7 days period and the level of water shall be recorded by a Hook Gauge every 6 hours in the last 72 hours. During this time the tank and pipe work shall be regularly checked for leaks. The tank will only be considered to be watertight if no leakage occurs for a 72-hour period and the water level remains constant for the last 24 hours.

If the tests fail, the source of all leakages shall be traced and remedial measures approved by FEWA shall immediately be carried out. The hydrostatic test shall be repeated until the test requirements are satisfied. The cost of water for the hydrostatic test shall be included in the tender. All costs associated with the remedial works and retesting shall be at the contractor’s expense.

24. CLEANING AND DISINFECTION

After the construction of the tank and hydrostatic test the contractor shall remove all dirt and foreign materials from inside the reservoir. On completion of the cleaning, the tank shall be emptied and dried out. The internal surface shall be prepared for protective coating as per manufacturer’s recommendations. Upon completion of application of the protective coating the reservoir shall be inspected by FEWA.

The tank shall be filled to a depth of 500 mm with potable water (to World Health Organization Standards). Sufficient calcium hypo chlorite shall then be added to give a solution containing approximately 500 ppm of available chlorine and this solution shall be thoroughly mixed by stirring. This chlorinated water shall be used to carefully wash down the complete tank including roof, columns and walls and bacteriological tests shall be carried out on the contents at FEWA Laboratory, Sharjah or other approved laboratories. If the results are not satisfactory the contaminated water shall be disposed off. Rewash down all the internal surfaces with fresh chlorine solution. This process shall be repeated until results of bacteriological tests prove to be satisfactory. After disinfection, the chlorine solution shall be drained to waste and storage tank shall be sealed. During cleaning and disinfection of the reservoirs and thereafter all persons entering the reservoir shall be first washed and cleaned with a 50mg/l Chlorine solution and strict hygiene discipline shall be enforced. Contractor’s workers shall enter the tank only with complete protective rubber clothing, chorine gas masks, use of safety lines, etc. and other necessary safety precautions including forced ventilation shall be complied with. The cost for the supply of water for disinfection and laboratory tests shall be included in the Tender.

WAM






25. EXTERNAL WORKS

Walkways with interlocking paving blocks and gravel bed shall be provided around the storage tanks.

26. ASSOCIATED WORKS 26.1 Mechanical

General Design, supply, installation and testing of inlet and outlet piping of proposed storage tanks according to battery limit mentioned in tender drawing including valves, fittings, etc. Design, supply, installation and testing of waste water system consists of overflow, washout system for the proposed tanks including valves, fittings upto battery limit .

Tanks Piping System: Piping for inlet, outlet, overflow, washout and waste water upto battery limit / terminal points. The final route, level at tie-points with incoming and outgoing line, etc. shall be as per the final investigation and design. As a minimum, the tank pipe work shall include, but not limited to the following:

Pipe supports, brackets, anchors, sleeves, clamps, insert plates (including future inlets) and associated accessories.

Sampling points, drying and vent pipes Valves and Accessories: Design, supply, inspection, testing, installation and commissioning of complete valves and accessories related to tank piping are as follows:

All the valves shall be provided with related meters, gauges, accessories as per the

detail engineering design required for the successful commissioning of work. On line integration of valves with equipments and piping shall be provided as per final design. Motor operated valves shall be supplied as per valve schedule complete with actuator and positioner.

Inlet motorized valves shall be provided vertically on line and manual valves shall be provided horizontally within chamber or vertically as per site condition.

Outlet and other valves shall be provided horizontally in valve chamber / pipe trench.

Surface boxes shall be provided for valve chamber, the valve in the chamber to be equipped with an extension spindle/gear system to enable valve operation from outside wherever applicable.

Dismantling joint shall be provided for each valve and meter.

26.2. Electrical Works In addition to the provision of electrical works required for the tank valve operation, the Contractor shall include Design, Engineering, supply, installation, testing and commissioning of complete LV cables, lighting and small power, lightning protection, earthing system etc. for tanks.

26.3 Instrumentation All instrumentation and control for storage tanks The detailed requirements for instrumentation works shall be as described in the instrumentation section of the Specifications.

Documents

Federal Electricity & Water Authority Water Directorate ......BS EN 1997-1 Eurocode 7. Geotechnical design. General rules BS 8007 Code of practice for the structural use of concrete