CRACK REPAIR
CONCRETE REPAIR GUIDE
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1. Mark out all suspect areas indicated by cracking to the concrete and/or corrosion stains.
2. "Hammer test" all concrete suspected of being included in 1 above.
3. Limit the area of individual repairs by cutting regular shapes at the perimeter of the repair using a small diamond bladed cutter. To avoid feather edging the minimum depth of cut should be 10mm into sound concrete.
4. Break out all loose and friable material, only use mechanical tools where absolutely necessary. In the case of narrow sections such as posts and columns it is essential that mechanical tools are not used as these may cause damage to hitherto sound concrete.
5. After all loose material has been broken out inspect, in detail, both the underlying surface of the concrete and the exposed steel that is revealed.
6. In areas where extensive rusting has occurred then it may be necessary to continue breaking out existing concrete around the remainder of the diameter of the steel in order to expose any areas containing active rust. Any removal of concrete should be carried out using hand tools.
7. In areas where extra cutting has been carried out reform the edge of the repair using the diamond disc technique identified in 3 above.
8. In the event that corroded tie wires may be revealed, these may be cut out completely. In the event that extensive corrosion and loss of section has occurred in the reinforcing steel, cut out the damaged steel.
9. Make provision for replacing the cut out steel by drilling the concrete and reinstating new sections of steel with ZEROSET ANCHOR GROUT. Where low cover is anticipated it may be advisable to carry out the replacement with stainless steel.
10. Clean the whole of the repair area, particularly that steel which remains and has surface rust. The ideal method is grit blasting, alternatively a needle gun may be used. Grinding of the steel and mechanical wire brushing are not ideal.
11. Prime the exposed steel with 1 good coat of HR Slurry Primer, allowing 1 hour to dry. Ensure that the steel protective coating is applied to the steel only and not to the concrete.
12. Mix P12 2 part epoxy primer and apply to the total repair area, including the previously coated steel. Application of P12 should be consistent with the minimum quantity required conducive with overall wetting of the entire surface within the repair area.
13. Mix RENDACRETE LW with the correct amount of water as per the data sheet. Alternatively if RM20 epoxy mortar is being used, mix the 3 components as per the data sheet. In both cases the data sheets are provided with the packs of material.
14. Apply the RENDACRETE LW using a combination of trowels and floats, do not over trowel. Finish with a wood float DO NOT spray or brush on extra water. When RM20 epoxy mortar is being used, use either S200 PC Solvent or detergent and water to clean the trowel prior to finishing. Use a steel float, do not apply solvent or water to the RM20 surface.
15. In the event that there is reinforcing steel within the repair area it may be necessary to use a gloved hand to compact the RM20 or the RENDACRETE LW around the full circumference of any steel. This is then followed by the trowel technique described above.
16. Due to position, i.e. overhead or complexity of shape it may be necessary to use shuttering to support the RENDACRETE LW or RM20 during its cure period. Ensure that the shuttering is treated with a suitable release agent such as ROTAFIX RELEASE WAX.
17. Ensure that any shuttering is firmly fixed to the sound concrete surround in order that the profile is accurately maintained and that the RENDACRETE LW/RM20 may be firmly compacted between the shuttering and the concrete.
18. If there is any doubt about supporting the repair in one application, I.e. if slump is likely to occur during the application process or the cure time, then the repair mortar should be installed in 2 or more operations.
19. All mortars should be applied whilst the primer is still tacky.
20. In the event that the primer cures before the application of the RENDACRETE LW or RM20, or the primed surface has been left overnight, then a further application of P12 PRIMER must be made prior to application of the mortar.
21. If the RENDACRETE LW or the RM20 is applied in 2 or more layers, (see 18 above), then an interim primer coat of P12 must be applied, it must be tacky when the new layer of mortar is applied.
22. The completed repair is now part of the total concrete structure and is now ready for a protective treatment of either VINACHEM or AQUACHEM anti carbonation coating.
© 2006 Rotafix Ltd
Rotafix, Aquachem, Rendacrete, Resiwood, Timberset, Vinachem and Zeroset are all registered trade marks of Rotafix Ltd.
