Bridge Concrete Superstructure

1. Scope

This section covers furnishing and providing concrete superstructure works for bridges including casting, handling, launching of RCC T-Girders, deck slab casting, bearing fixing, expansion joints, and drainage spouts in accordance with approved drawings and MoRTH Specifications.

2. Material

All materials used in bridge superstructure works shall conform to Section 1000 of MoRTH Specifications.

3. Casting & Handling of Precast RCC T-Girders

3.1 Fixation of Formwork

• Firm and level casting beds shall be prepared at site for girder casting.
• Side shutters shall be erected as per approved girder dimensions.
• Adequate spacing shall be maintained around girders for de-shuttering and handling.
• Shuttering shall be cleaned and coated with approved shuttering oil before concreting.

3.2 Preparation & Placing of Reinforcement Cage

• Bar Bending Schedule (BBS) shall be prepared as per approved drawings.
• Cutting, bending, and tying of reinforcement shall be carried out as per approved BBS.
• Reinforcement details shall be checked and recorded before concreting.
• Approved cover blocks of same grade concrete shall be used.
• Prestressing ducts, inserts, and embedded items shall be fixed as per drawings wherever applicable.

3.3 Pouring of Concrete

• Concrete of approved grade shall be produced at batching plant using approved mix design.
• Concrete shall be transported using transit mixers and poured through chute arrangements.
• Concrete placement shall proceed continuously from one end to another.
• Cold joints shall be avoided during concreting.
• Compaction shall be carried out using 40 mm and 60 mm needle vibrators.
• Wooden mallets shall be used externally on shutters to remove air voids and honeycombing.

4. Identification of Precast RCC T-Girders

Each girder shall be properly marked for identification purposes on both sides.

• Date of Casting
• Length of Girder
• Girder Number

5. Curing & De-positioning of RCC T-Girders

• Girder curing shall be carried out as per MoRTH Specifications.
• Continuous curing shall be maintained for specified duration.
• RCC T-Girders shall be shifted from casting bed after achieving minimum required strength or after 14 days, whichever is applicable.
• Suitable lifting arrangements shall be used during handling and shifting.

6. Tolerances

7. Pedestal Casting & Bearing Fixing

• Bearing centerlines shall be marked accurately over pier/abutment caps.
• Pedestal dimensions shall conform to approved drawings.
• Minimum 150 mm clear offset shall be maintained beyond bearing edges.
• Shuttering shall be erected to required pedestal dimensions.
• Anchor pockets shall be provided during pedestal concreting.
• Pedestals shall be cast approximately 20 mm below finished bearing level.
• Final leveling shall be done using cement epoxy mortar during bearing installation.

8. Launching of Girders

• RCC T-Girders shall be lifted using lifting hooks provided at both ends.
• Two cranes shall operate simultaneously during launching.
• Girders shall be placed directly over bearings in true alignment.
• Level, line, and plumb shall be checked after placement.
• Suitable packing or crib arrangements shall be provided where required.
• Placed girders shall be adequately braced to prevent movement during deck slab construction.

9. Staging for Casting of Deck Slab

9.1 General Arrangement

• End diaphragm reinforcement and shuttering shall be completed before deck slab staging.
• Temporary working platforms shall be erected between girders.
• Staging shall be fabricated using scaffolding pipes and channels.
• Needle vibrators shall be used for compaction of diaphragm concrete.

9.2 Cantilever Portion

• Outer girders shall be provided with holes for insertion of tie rods.
• Cantilever support frames shall be fixed using threaded tie rods and bolts.
• Required formwork shall be erected over support frames.

9.3 Inner Portion

• Deck slab staging shall be supported from girder flanges and not from ground.
• Wooden blocks shall be fixed on girder bottom flange.
• H-frames and ISMC channels shall be installed using screw jacks.
• Proper bracing shall be provided to prevent sliding or instability.
• Shuttering for diaphragm and slab shall be erected as per approved drawings.
• Foam strips shall be provided between shutter joints to prevent leakage.
• Levels shall be checked and adjusted using screw jacks.
• Approved shuttering oil shall be applied before concreting.
• Entire staging and shuttering shall be inspected and approved by AE.

10. Reinforcement

• BBS shall be prepared and approved before commencement of reinforcement work.
• Cutting and bending shall be checked for correct shape and dimensions.
• Reinforcement shall be placed as per approved drawings.
• Drainage spouts and rainwater pipe inserts shall be fixed before concreting.
• Cover blocks and chairs shall be provided to maintain required cover.
• Wooden blocks shall be fixed for expansion joint recesses as per approved details.

11. Concreting

• Concrete shall conform to approved mix design and specified grade.
• Required slump shall be maintained to achieve proper compaction.
• Concrete shall be transported using transit mixers and placed using concrete pump or placer boom.
• Concrete in diaphragm shall be laid in layers not exceeding 500 mm.
• Concreting shall proceed continuously from one expansion joint towards another.
• Concrete pump pipeline arrangement shall minimize dismantling and re-fixing during concreting.
• Proper vibration and compaction shall be ensured throughout concreting operations.

12. De-shuttering of Deck Slab

• Deck slab shuttering shall be removed after achieving specified strength or after 14 days as per MoRTH Specifications.
• Shuttering plates and scaffolding pipes shall be removed carefully using chain pulleys and ropes.
• Temporary working platforms shall be utilized during de-shuttering operations.
• All removed materials shall be safely lowered and stacked.

13. Deployment of Machinery

• Concrete Pump
• Batching Plant
• Transit Mixers
• Concrete Vibrators
• Needle Vibrators
• Cube Moulds
• Bar Bending Machine
• Generator / Electrical Arrangement

14. Installation of Strip Seal Expansion Joint with Sinus Plate

• Expansion joints shall be installed under supervision of manufacturer/supplier engineer.
• Installation manuals shall be followed strictly.
• Joint gap dimensions shall be preset based on installation temperature.
• Recess dimensions, skew, and levels shall conform to approved drawings.
• Recess surfaces shall be cleaned thoroughly before installation.
• Joint assemblies shall be aligned and welded with reinforcement as specified.
• Concrete around joints shall be compacted and cured properly.
• Installation brackets shall be removed after curing.
• Neoprene strip seals and sinus plates shall be fixed as per manufacturer details.
• Surfacing around steel edge sections shall be sealed using approved sealing compound.

15. Drainage Spouts

15.1 General

• Adequate drainage spouts shall be provided along deck slab.
• Drainage spouts shall be fabricated using corrosion resistant galvanized steel.
• Minimum diameter of drainage spouts shall be 100 mm.
• Spacing of drainage spouts shall not exceed 10 m.
• Drainage discharge shall be directed away from bridge structure.

15.2 Fabrication

• Steel components shall conform to IS:226.
• Drainage assemblies shall be seam welded and hot dip galvanized.

15.3 Placement

• Galvanized assemblies shall be coated with two layers of bituminous paint before installation.
• Assemblies shall be fixed accurately in line and level.
• Equivalent reinforcement shall be provided wherever deck reinforcement is cut.
• Shrinkage cracks around assemblies shall be sealed using bituminous sealant.
• Excess sealant shall be trimmed before laying wearing coat.

16. Quality Control

• Reinforcement Inspection
• Formwork & Staging Inspection
• Concrete Slump Test
• Concrete Cube Testing
• Girder Alignment & Level Check
• Bearing Level Verification
• Deck Slab Thickness Check
• Expansion Joint Inspection
• Drainage Spout Inspection

17. Safety

• All personnel shall wear PPE including helmets, safety belts, reflective jackets, gloves, and safety shoes.
• Safe lifting practices shall be followed during girder launching.
• Scaffolding and staging shall be checked before use.
• Barricading and warning signs shall be provided around work areas.
• Working at height shall comply with approved safety procedures.
• Proper illumination shall be provided during night work.
• Electrical and lifting equipment shall be inspected regularly.