REHABILITATION OF CONCRETE STRUCTURES OF CHIMNEY-4 AND 5 AT CPP

Scaffolding/ Platform : The platform system for the entire work which will assist in repair, rehabilitation and inspection of the entire external surface area shall be designed suiting the job requirement including the wind velocity etc. with all safety requirements, and arranged by the agency. The system may consist of scaffolding, suspended platform system, cradles, temporary lifts or combination of such systems meant to give Safe access for inspection and Safe repair working of the entire surface area throughout all heights of Chimney(From Zero mtr to 220 mtr). The rate is inclusive of providing design and drawing after getting approval from government agencies (like IIT, NIT, Universities etc,). The rate is also inclusive of providing and removal of the moving platforms after completion of work. 90% of the rate shall be paid upon installation and testing of the system by competent person/agency. 10% of the rate shall be paid after removing the moving platforms upon completion of work. (Payment shall be made against the 90% amount, on pro rate basis for installation of the system partly as per the requirement of the site for repair/painting at/up to any particular height).

Chipping/Removing of concrete :Removing/ chipping upto average 40mm depth, 500mm on either side of horizontal & vertical cracks of chimney stack and cleaning of existing loose concrete carefully by manual or low impact frequency hammer without damaging the existing concrete including cleaning the surfaces by compressed air jet, wire brushes etc complete. The debris will be disposed upto lead of 500m. The entire surface will be checked by light hammering (using 1 Kg hammer) for detection of loose concrete. Edges of chipped patch will bear vertical/reverse cut with minimum depth at edges as 10 mm. (Prepared patches to be got checked before applying bond coat). All loose/unsound concrete has to be removed to prepare well defined patch, all complete as per specifications and direction of Manager-In-Charge

Nipples for Grouting : Providing and fixing/ inserting 12mm dia NRV galvanized steel injection nipple upto 150 mm long in honeycomb area and along crack line including drilling of holes of required diameter (upto 25 mm) up to a depth of 80mm at required spacing and making the hole & crack dust free by blowing compressed air, sealing the distance between injection nipple with adhesive epoxy chemical of approved make & allow it to cure and subsequent cutting & removal of the same after grouting is completed, all complete as per specifications and direction of Manager-In-Charge. Epoxy putty : Nitocote VF (Fosroc) or equivalent#

Epoxy Injection Grouting : Providing and injecting two component Low viscosity Epoxy grout (<350 centipoise (cps)) of approved make in proportion recommended by the manufacturer into cracks/ honey-comb area of concrete by suitable gun/ pump at required pressure all complete as per manufacturer's specifications and direction of Manager-In-Charge. (The payment shall be made on the basis of actual weight of approved epoxy grout injected) Epoxy Injection Grout : Nitofill EP LV (Fosroc) or equivalent

Derusting/Cleaning of Reinforcement : Providing and Cleaning of rust from reinforcement bars including from behind the bars to give it totally rust free finished steel surface as per requirement, by using chemical rust remover of approve make with paint brush and removing loose particles after 24 hours of its application with wire brush and thoroughly washing with water and allowing it to dry, all complete as per the manufacturer's specifications and direction of Manager-In-Charge. For measurement, surface area of repair work will be taken.Chemical rust remover: Reebaklens RR (Fosroc) or equivalent

Anticorrosive treatment : Providing and applying two coats Anticorrosive treatment to exposed reinforcing bars using anticorrosive product of approved make after cleaning the corroded steel bars (manually/ with rust remover) and drying, all complete as per manufacturer's specifications and direction of Manager-In-Charge. For measurement, surface area of concrete repair work will be taken. Anticorrosive treatment: Nitozinc Primer (Fosroc) or equivalent

Corrosion Inhibitor : Providing and applying Corrosion Inhibitor of approved make including necessary surface preparation as per manufacturer's specification on areas demarked by Manager in Charge. For measurement, patch area of repair work will be taken.Corrosion Inhibitor: FerroGard-903 (Sika) or equivalent

Steel Reinforcement : Steel reinforcement for RCC repair work including transportation from Nalco store, straightening, cutting, bending, placing in position, fixing into the concrete surface by drilling holes by suitable means & anchoring by injecting with suitable epoxy resin hardening system, binding etc. all complete at all heights, as per specifications and direction of Manager-In-Charge.(Reinforcement steel will be issued free of cost at NALCO stores.)

Epoxy Bond Coat : Providing and applying structural grade two component epoxy bond coat of approved make prior to application of any type of mortar to ensure bond between old and new concrete by brush application including necessary surface preparation such as cleaning, air blowing etc. all complete as per manufacturer's specifications and direction of Manager-In-Charge.(For measurement, patch area of repair work will be taken.) Epoxy resin Bond : Nitobond EPstandard (Fosroc)or equivalent

Polymer Modified Mortar : Building up the profile of structural members to required level, providing & applying ready mixed chemically modified fibre reinforced polymer mortar of 40mm average thickness in 2-3 layers of 10-15 mm thick layers each, applying bond coat between successive/ each layers including levelling & profiling complete as per manufacturer's specification and directions of Manager-In-Charge. Proper curing shall be done for the repair work. Gunny bags may be used for effective curing. Glass fibres @ 1Kg/cum of (Gujcon/Osnar or Equivalent) may be added to reduce shrinkage and to achieve homogeneity in PMM mix as per requirement. 70.2x70.2x70.2 mm cube shall be taken as representative samples to achieve 28 days compressive strength of minimum 40 MPa at 28 days of curing in water, all complete as per manufacturer's specifications and direction of Manager-In-Charge. Polymer Modified Mortar: Renderoc SP40 (Fosroc)or equivalent