Supports

The R C members shall be properly supported before chipping the spalled / loose concrete. The props provided shall be adequate to provide sufficient structural support to the load carrying members.

Surface Preparation of concrete

All the spalled cracked concrete or any other pre-applied mortar shall be removed by chipping to expose the reinforcing bars. The concrete shall be chipped to a minimum depth of 10mm behind the reinforcing bars. The areas to be repaired shall be profiled to get rectangular or square shape with an inward tapering edges

Surface preparation of reinforcement

The exposed reinforcing bars shall be cleaned thoroughly to remove all traces of rust, scales, etc., by using wire brush, emery paper etc. The lateral ties/stirrups shall also be cleaned in the same way. After removal of corroded portion, the diameter of the reinforcement shall be checked and compared with the drawings.

Provision of additional reinforcement

As the diameter of reinforcing bars is reduced substantially (say >20%) additional bars shall be provided as per the design. This additional reinforcement shall be properly anchored to the existing concrete by providing adequate shear connectors. Weld mesh may also be provided if found necessary depending on the recommendation of Structural / Design Engineer.

Provision of shear connectors

Shear connectors of 8mm dia shall be provided in holes of 14mm dia and 75 mm deep. These shall be provided at every 500 mm c/c on all the faces of the beams in staggered form. The holes shall be cleaned with compressed air or water jet to remove all the dust etc. and then the shear connectors shall be fixed in the holes using polyester resin anchor grout Dr. Fixit Anchorfix P

Priming of reinforcement bars

The exposed and cleaned reinforcing bar shall be provided with a coat of DR.Fixit Epoxy Zinc Primer such that the coated film will have a dft of 40 microns. The film shall be continuous especially in the regions where pitting, imperfections etc., are present on the surface of the bars. It is important that the rear portion of the bars should not be left without coating. A second coat if needed may be provided to achieve a uniform and continuous film. The additional reinforcement provided and also the shear connectors shall be coated with DR.Fixit Epoxy Zinc Primer. The weld mesh if provided shall also be coated with DR.Fixit Epoxy Zinc Primer.

Provision of Epoxy based bonding agent (Dr. Fixit Epoxy Bonding Agent)

The base and hardener component of epoxy resin based bonding agent must be mixed well to get a uniform grey coloured mix. Apply the material to properly cleaned and dry concrete substrate using stiff nylon brush by scrubbing it well into the substrate. The coat should be uniform and well spread on the entire surface area of the repair patch. The mixed material must be applied before the elapse of its pot life and the new repair mortar must be applied before the elapse of overlay time. As a fully dried epoxy resin coat acts as debonding layer, the repair material should be applied whilst the bonding coat is tacky. In case the applied epoxy bond coat gets dry, an extra coat should be applied before application of repair mortar.

Formwork and shuttering

Slurry tight and strong form work shall be provided. The shuttering for encasement shall be kept ready such that the formwork shall be placed in position and fixed such that the Microconcrete can be poured into the formwork within the overlay time of the bonding agent (5 hours). Adequate supports shall be provided for the formwork. Care should be taken to ensure leak proof shuttering. Under no circumstance the slurry shall flow out of the shuttering during pouring of microconcrete.

Mixing of microconcrete

Dr. Fixit Microconcrete, a cementitious, non-shrink microconcrete shall be mixed using the appropriate water powder ratio as mentioned in the product data sheet. The mixing shall be done mechanically and under no circumstance hand mixing shall be done. Mixing shall be carried out for 3 to 5minutes to ensure that homogeneous mix is obtained without any bleeding or segregation. In hot climate ice cooled water shall be used to maintain the temperature of mixed material. If the encasing thickness is more than 75 mm, add stone aggregates up to 50 % by weight of microconcrete to the mixed microconcrete directly into the mixer hopper. The stone aggregates must be 12 mm and down and shall be clean, washed and dried. Mix first microconcrete with recommended dose of water for about 3 minutes in mixer and then pre weighed stone aggregates into the mixer. Mix further for about 2 minutes till lump free mix is obtained. Do not add extra water than mentioned in the product data sheet.

Pouring of microconcrete

The mixed Dr. Fixit Microconcrete shall be poured into the formwork using a suitable funnel or through a hose pipe. It must be poured from one end only. A suitable hopper / funnel arrangement shall be made at site to facilitate the pouring operations. The pouring operation shall be continuous and it shall not be stopped unless the job is completed. To achieve this sufficient mixers / drilling machines and wok force shall be arranged at site.

Deshuttering

The shuttering from the sides of the R C members shall be removed after a period of 24 hours. However, the formwork of the soffit shall be retained and removed after 3 days.

Curing

All the repaired and encased area shall be fully cured as per standard concrete practices. Curing compound shall be used for effective curing of sides and soffits of beams. Note : If a curing compound is applied, care shall be taken to ensure that proper surface preparation is carried out so as to remove any traces of curing compound on the surface. If this is not done, it may lead to debonding of any protective coating applied on top.