Structural Rectification works at Elamkulam Metro station.

Surface Preparation of Concrete including sand blasting, application of Anti-corrosion primer and rust converter coating on exposed rebars, Cleaning and Disposal: Surface preparation of damaged/deteriorated concrete areas prior to structural repair works of damaged concrete elements such as beams, columns, slabs, or pedestals on Road,Inside station and Link bridge. This work includes sand blasting for removing the existing paint and apply two component epoxy based anti-corrosive coating and rust converter. The scope includes identification and marking of defective concrete zones using spray paint or chalk based on visual inspection/Hammering and structural drawings; chipping and removal of all loose, weak, and spalled concrete using suitable tools (manual or mechanical) up to sound substrate without damaging reinforcement;And upto aggregate size + 5 mm or 25 mm whichever is more behind the corroded steel. inspection and ensuring adequate surface profile for bonding (medium-grit sandpaper finish); followed by thorough cleaning of the surface using air blower or water jet to remove dust, laitance, and debris. All loosened materials and debris to be collected and disposed of away from the working area as per site engineer’s instructions. Rate to include all tools, labour, materials, cleaning, and safe disposal.

Supplementary Reinforcement Steel (If Corrosion > 15%) – Supply, Cutting, Bending & Placement: Supply, cutting, bending, and placement of supplementary reinforcement steel in damaged structural elements where the existing rebar has corroded beyond 15% of its cross-section. Reinforcement steel shall conform to IS:1786 (Fe500/Fe500D grade or as specified) and shall be lapped or anchored as per structural drawings and engineer’s instructions. Includes measurement of corroded bars, removal of severely deteriorated sections, preparation of lap joints, fixing with binding wire, and placement in the repair zone. Rate includes all tools, labour, binding wire, and associated accessories for reinforcement works.

Injection of Epoxy Resin into Structural Cracks: The item includes identification and marking of cracks in RCC members such as beams, slabs, columns, or pedestals through visual inspection. Drilling of holes at 45° inclination along the crack line at regular intervals (typically 300 to 500 mm), ensuring intersection with the crack path. Supply and fixing of injection packers (grouting nipples) into drilled holes and sealing of the surface crack length using epoxy putty to prevent leakage. After surface seal curing, injection of two-component epoxy resin (mixed as per manufacturer’s specification) shall be carried out using a hand-operated or electric pump, starting from the lowest packer and progressing upwards to ensure complete filling. Injection pressure shall be controlled (not exceeding 4–5 bar) to prevent blowouts. After injection, allow curing of the epoxy for 24 to 48 hours. Once cured, packers shall be removed and drilled holes sealed with epoxy mortar or non-shrink filler. Rate includes cost of all labour, materials (epoxy resin, putty, nipples, fillers), tools, equipment, cleaning, and all incidental works complete in all respects.

Cutting and Forming Reinforcement-Based Shear Keys in Existing Concrete Including Drilling, Bonding Agent, Grouting, and Reinforcement Steel: The item includes identification and marking of shear key locations on existing RCC surfaces based on structural drawings. Drill holes using a rotary hammer drill to the required depth and diameter to receive reinforcement bars acting as shear keys. Clean drilled holes thoroughly using wire brush and air blower to ensure dust-free bonding surfaces. Supply and insertion of high-yield deformed reinforcement bars (Fe500/Fe500D) of specified diameter and length into the holes shall be carried out. Rebars shall be fixed using approved epoxy-based adhesive (e.g., Hilti RE500, Fosroc Lokfix) or non-shrink grout to ensure firm anchorage and effective load transfer. Maintain verticality and proper alignment of dowels as per drawing. All reinforcement bars shall be cut, bent, and placed to provide mechanical interlock with the repair section and additional mesh reinforcement. Includes all labour, materials (including reinforcement steel, epoxy/grout), tools, and equipment required for completing the shear key installation

Supply and fixing of of Vapor/Volatile Corrosion Inhibitor (VCI) Capsules as per the Methodology and as per the directions of the Engineer

Supply and mixing of Traversing Type Corrossion Inhibitor -Concentrated powder additive for micro concreting

Providing and Fixing of GI Wire Mesh (62*62*2.5 mm Opening) for Guniting Work: The item includes cutting and trimming of welded galvanized iron (GI) wire mesh of 62*62*2.5 mm mesh size to the required shapes and dimensions to suit the prepared repair area.The steel wire mesh has to be placed in position keeping the mesh within 10-15 mm from the surface.The mesh shall be positioned properly over the substrate and securely tied to previously fixed reinforcement or shear keys to provide proper reinforcement and surface bonding support for gunite (shotcrete) application. All overlaps between adjoining mesh sheets shall be a minimum of 50 mm and shall be tied with GI binding wire to prevent displacement. Mesh shall be fixed to ensure adequate cover, prevent sagging or bulging during guniting, and maintain proper alignment with the structural profile. A thorough inspection shall be conducted before gunite application to verify mesh fixing, spacing, and stability. Rate includes supply of GI mesh, binding wire, cutting, placing, tying, fixing, labour, tools, and all materials required to complete the work in all respects.

Providing and Fixing Formwork for Repair Works Including Application of Release Agent, Removal, and Reconditioning of Reusable Forms: The item includes providing, fixing, and aligning rigid and leak-proof formwork to define the boundaries of micro-concrete or shotcrete (gunite) repairs in columns, beams, pedestals, or soffits. Formwork shall be properly supported and sealed to avoid leakage or deformation during placement. Apply a suitable form release agent (mould oil) on contact surfaces prior to placing the repair material to prevent adhesion. After casting, remove non-load-bearing formwork after at least 24 hours if the concrete has gained sufficient initial strength. Load-bearing formwork shall be removed only after achieving specified compressive strength, as certified by the engineer. Reusable formwork shall be cleaned, repaired (if damaged), and recoated with release agent before reuse. Rate includes all materials, labour, tools, release compound, fixing, removal, and preparation for reuse, complete in all respects.

Providing and Applying Bonding Agent (SBR-Modified Slurry or Two-Component Epoxy) on Prepared Surface Prior to Guniting: This item includes surface preparation to Saturated Surface Dry (SSD) condition followed by uniform application of an approved bonding agent—either SBR-modified cement slurry or a two-component epoxy bonding system—over the entire area to be repaired. The bonding agent shall be prepared and applied as per manufacturer’s specifications using a brush or roller, ensuring even coverage. The substrate shall be tacky (not dry) at the time of performing guniting to achieve effective monolithic bonding between the new and old concrete surfaces. Timing of repair material placement must be carefully controlled to prevent bond failure. The rate includes all labour, materials, tools, and equipment for surface cleaning, preparation of bonding coat, and application complete in all respects.

Gunite (Shotcreting) Work : Providing and applying Gunite (shotcrete) to damaged RCC structural members such as columns, soffits, girders, pier areas, etc., using a dry or semi-dry shotcreting process with approved mix design. The dry mix shall be prepared with Cementitious material, 6mm downsize aggregate, fine aggregates (M-sand, Zone II/III conforming to IS 383-1970), and approved mineral admixtures such as fly ash, GGBS, or micro-silica. The mix shall be conveyed through a calibrated gunite machine and sprayed onto the substrate using compressed air at proper pressure. Water shall be added at the nozzle to achieve a water-cement ratio between 0.35 and 0.50. Concrete shall be applied in multiple layers in circular motion to avoid rebound and overbuild. Surface shall be immediately trowelled after application, with layer thickness monitored using depth gauges and edges trimmed along straight form lines.Thickness of guniting is 50mm. Curing shall begin after the initial set by spraying water or as per specification. Rate includes labour, all materials (cement, sand, admixtures), use of equipment, air compressors, nozzleman operation, application in layers, surface finishing, and initial water curing

Fibre Reinforced Polymer Plastering: Labour, material and supervision charges for providing upto 15-20mm thick fibre reinforced polymer modified plastering added with latex, over the shortcreted and micro concreted area in order to make an even surface.

Supply and Placement of Non-Shrink Micro-Concrete for Structural Repairs (inside the station building area): Supplying and placing ready-to-use, non-shrink, free-flowing micro-concrete (such as Renderoc RG, Sika Rep Microcrete-4, or equivalent approved make) for structural repair for additional upto 50mm thick in damaged RCC members like columns, beams, pedestals, and pier caps. Micro-concrete shall be mixed using a mechanical paddle mixer or tilting drum mixer with clean potable water as per manufacturer’s recommended ratio (e.g., approximately 4.0 litres per 25 kg bag) to achieve a flowable, non-segregating consistency. Mixing shall be carried out for 3–5 minutes until a homogeneous mix is obtained. The prepared mix shall be poured via gravity using funnel, chute, or tremie into the shuttered repair zone. Pouring shall commence from the lowest point to ensure smooth flow and air displacement through vent holes. No needle vibrators shall be used; instead, light tapping of the formwork or use of rods may be adopted to assist in flow. Placement must be done in a continuous operation to prevent formation of cold joints. The rate shall include the cost of all labour, materials, tools, mixing water, machinery, transportation, handling, and placing of micro-concrete in position as per specification and directions of the Engineer-in-Charge.( Additional thickness will be charged proportionately)

Application of Curing Compound: Providing and applying approved resin-based or acrylic curing compound over freshly applied Polymer Modified Mortar (PMM), Gunited or micro concreted surfaces to retain moisture and ensure proper curing. The surface shall be free from standing water, laitance, and dust before application. The curing compound shall be applied uniformly using a low-pressure spray, roller, or brush immediately after initial setting of the plaster to prevent premature drying, shrinkage, or surface cracks. Regular monitoring shall be carried out to ensure curing is maintained for the required duration and that no surface is left untreated. Rate includes all labour, materials, equipment, and tools for application, handling, and daily observation during the curing period, complete in all respects.

Providing and Applying Anti-Carbonation Coating: Providing and applying anti-carbonation protective coating on exposed and repaired concrete surfaces to enhance durability and protect against ingress of CO₂, moisture, and environmental pollutants. The work includes cleaning the fully cured surface using a dry cloth or air blower to ensure it is dust-free and dry. Apply one coat of approved primer compatible with the anti-carbonation system and allow it to dry as per manufacturer's specification. Subsequently, apply the first coat of anti-carbonation coating using a roller or brush in a uniform manner across the surface. Allow a drying time of 4–6 hours (or as per product requirement) before applying the second coat in a cross-directional pattern to ensure uniform film coverage. The coating shall be protected from rain or dust until fully dry. Measure the final dry film thickness (DFT) using a thickness gauge to ensure compliance with specifications (typically ≥100 microns in two coats). Perform touch-up work in any missed or uneven areas. Rate includes supply of material, primer, surface preparation, application, equipment, DFT checking, and all labour complete in all respects.

Pedastal repair of link bridge at Platform level-Labour, material and equipment charges for providing barricading to prevent public hinderance while doing the job, scaffolding with working platform prior to start the work. Providing load relieving back propping using screw jacks, support through props and crib from the ground level and hydraulic jack with necessary wooden cut blocks with proper level and alignment to be done before starting the repairing work.Removing the existing cracked concrete from the pedestal using electrically chipping machine, fabricating the reinforcement mat with 12mm rod in the size of 100*100mm and position the bolt and weld as per site conditions and one side bole must ensure slotted. Chipping the cover concrete from the top surface corbel and expose the reinforcement to facilitate welding of mat or 8mm sheasr key to be fix using polyester resins grout and weld the prepared mat to shear key, leak proof shutter to be provide using plywood prior to pour epoxy concrete . Mixing and pouring high early strength ( more than 80N/mm2 after 24 Hrs time) free flow epoxy grout as per manufactures specifications. Size 480*480*100mm or nearest size as per site condition. Remove shutter after 2 days, Realigning girder after providing 10mm Neoprene pad with slotted holes. After completeing the work, remove all scaffolding and clean the site as per department requirements.

Unforseen items which are not covered in the above which shall be paid as per the latest PRICE /DSR rates (Bidder can quote only Rs. 1,00,000 for this item)