Concrete Repair

Concrete preparation

The surface of the concrete to be repaired should be sound, clean and uncontaminated. The boundary of the repair area should be cut using a concrete saw to provide a neat edge to the repair with no feather edging and to provide a square edge.

Repairs using BETOCRETE REPAIR should be generally at least 50 mm as a minimum depth with a maximum of 500 mm in single coat.

Oil and grease deposits should be removed by stiff brushing, detergent scrubbing with a heavy duty cleaner/degreaser or steam cleaning.

Prepare the formwork to be rigid and tight to prevent loss of material. The formwork should include drainage outlets for presoaking.

Steel preparation

Any corroded steel in the repair area must be fully exposed. All exposed reinforcement shall be cleaned of corrosion products by wet grit blasting or other approved means to achieve a clean and bright finish.

In case that reinforcing bars section is reduced due to oxidization, integrate them with additional bar reinforcement.

Priming

Steel Priming

The cleaned steel should be coated within 3 hours. Apply one coat of BETOFER, a corrosion proof cementitious based primer or EPOZINC, a two component zinc rich epoxy primer, continuously with brush onto the cleaned bar reinforcement ensuring that the whole steel surface area is completely covered. Allow to dry before continuing.

BETOCRETE REPAIR must be applied before the bonding agent dries while it’s still tacky to achieve a better bond between the fresh and cured section.

Mixing

To prepare the mortar, it is recommended to have a forced-mixer of spiral paddle in a slow speed (300/400 rpm) heavy duty drill or mixer. It is essential that machine mixing capacity and labour availability is adequate to enable the placing operation to be carried out continuously.

Add 3.3 – 3.5 liters of water in the mixing drum then add the full bag of BETOCRETE REPAIR and mix for at least 4 – 5 minutes till obtaining a fluid, uniform lump free consistency mix.

Do not part mix the bags, nor use additional water than specified. Note that powder must always be added to water.

To obtain the full benefit of the fluidity provided, apply BETOCRETE REPAIR immediately after mixing.

Application
Conventional wet-process shotcreting equipment (preferably low pressure machine) should be used. Apply the BETOCRETE REPAIR mortar by low pressure spray or by trowelling for repairing overhead or vertical surfaces. The shotcrete must be shot perpendicular to the surface in order to minimize rebound, have a smooth pattern and to properly encase the rebars. After application of the shotcrete, the mortar should be allowed to stiffen, prior to the removal of lumps or bumpy areas using a trowel. Next layer is to be applied only after the first layer has reached the initial setting point (from 1 to 3 hours, depending on site and climatic conditions, mix consistently).

Curing
The repaired area shall be cured in accordance with good concrete curing practice and protected from drying winds, sun or excessive heat.  Curing shall be done with non-degradable curing compound BETOCURE AR. Alternatively; a wet hessian cloth covered with polyethylene sheet can also be employed.  Curing should begin as soon as final finish is achieved.

Cleaning
BETOCRETE REPAIR should be removed from tools and equipment, mixers with clean water immediately after use. Cured material should be removed mechanically.

Recommendations

• Do not apply the product at temperature less than +5°C.
• Do not add water once the mix has begun to set BETOCRETE REPAIR should not be exposed to running water either during application or prior to final set.
• Do not mix the bags partially.
• In warm weather, store the material in cool place. Make sure to use cool water to keep the mixed mortar temperature below +30°C.