Surface Preparation

All damaged, deteriorated, loosened, or unbonded portions of existing concrete shall first be removed by manual / mechanical means using electrically operated / pneumatic chisels, after which the surfaces of existing concrete shall be cleaned by high pressure water jetting. The surfaces shall then be cleaned and allowed to dry thoroughly, unless the specific repair technique requires application of materials to a saturated surface. Concrete removal processes involving the use of jack hammers in excess of 30 pounds, dry sandblasting, or scrabblers shall not be used without approval by the Engineer-in charge. The use of acids for cleaning or preparing concrete surfaces for repair will not be permitted.

Saw Cut Edges

The perimeters of repairs to concrete that involve concrete removal and subsequent materials replacement shall be saw cut perpendicular to the repair surface to a minimum depth of 10 mm. Feather edge repairs to concrete shall not be used

Surface preparation of steel

Cleaning of Reinforcement

Methods for removing rust and corrosion scale from the reinforcement exposed after cutting back and preparing the concrete shall be subject to acceptance by the Engineering-charge. The steel shall be cleaned manually with emery paper or by sand blasting (wherever permissible) to a bright steel finish. Methods based on wire brushing and chemical rust removers will not be permitted. Clean all exposed reinforcement, which is to remain in the completed Works to a bright finish including behind the bars. Do not leave the bars exposed for more than three hours after cleaning.

Defective Reinforcement

Unless otherwise directed by the Engineer-in-charge, replace all reinforcing bars, which have corroded to the extent of 1/3 of original bar diameter or more, as these shall be deemed defective over the affected length. Either cut out the defective portion or clean it as specified. For links, binders or stirrups, leave not less than 12 diameters or 120mm, whichever is the greater, of unaffected reinforcement projecting from sound concrete. Unless otherwise directed by the Engineer-in-charge or shown in the Drawings, expose longitudinal bars to leave an unaffected length of bar projecting from sound concrete, either side of the defective portion, in accordance with the lap length requirement.

Replacement Reinforcement

Unless otherwise directed by the Engineer-in-charge, replace or supplement all defective reinforcing bars with bars of the same type and diameter exposed from the original construction. Lap the replacement bars to the existing reinforcement for the projecting lengths in accordance with the lap length requirement. All replacement reinforcement shall be adequately fixed and tied in position such that it will not be displaced during subsequent repair works. Do not weld the reinforcement unless otherwise agreed. Unless otherwise directed by the engineer-in-charge or shown on the drawings the cover to the replacement or supplementary reinforcing bars shall be the same as the cover provided in the original construction.

Reinforcement Priming

The exposed and cleaned reinforcing bar shall be provided with anti corrosive coat of Dr.Fixit Zinc Epoxy 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 presents on the surface of the bars. It is important that the rear portion of the bars should not be left over without coating. A second coat if needed may be provided to achieve a uniform and continuous film

Preparation of polymer modified mortar

The concrete substrate must be saturated with water till saturated surface dry condition is achieved. Any excess water may be removed by cloth or oil free compressed air. No bonding agent is necessary for application of this repair mortar up to 40 mm thickness in a single layer.

Mixing

Polymer Mortar HB must be mixed mechanically. For this, heavy-duty slow speed drill with spiral mixing paddle or forced action mixer can be used. Add 3.5 litres of water into the mixer. Start the mixer and add the Polymer Mortar HB powder rapidly and continuously. Mix for 3 minutes until homogeneous and lump free mix is obtained. Add water, if necessary, to get the desired consistency. Mix further for 1-2 minutes. Under no circumstances excess water should be added. Little extra water may be required in hot climatic conditions. If ambient temperature is >300C, use chilled water for mixing and store unused product in the shed. For better results maintain the mixed temperature of product at 35 degree C.

After mixing Polymer Mortar HB can be sprayed or trowel applied. When applying by hand Polymer Mortar HB must be forced tightly into the substrate to ensure complete contact with the pre-wetted substrate. In situations where reinforcement steel is countered, the mixed material should be placed behind the bars tightly and then subsequent thickness should be built. Thickness of 40 mm can be built in a single layer where heavy reinforcement is not encountered. For more thickness allow first layer to dry sufficiently before applying next layer. Leveling and initial finishing should be carried using a wooden or plastic float. Final finishing should be carried out using a steel float.

Curing

Good curing is essential. Particular care is required in hot and / or windy conditions. Curing can either be done with a single coat of Dr. Fixit Curing Compound or by covering the repaired area with plastic sheet fixed over wet hessian