1. Concrete repairs, crack sealing
Part 11b)-2
Concrete repairs, crack sealing
and waterproofing using component PU resins
(Part 11b, PP 2007, animation+p/r, compr. : , rev )
Copyright notice Unauthorised copying of this presentation as whole or in parts in any form or by any means, electronic, photocopying, recording or otherwise, without prior written permision is prohibited.
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2. Mechanical packers with HP-pan-head nipple – cont.
HIGH PRESSURE HOSE BETWEEN THE MIXING UNIT AND THE PACKER
SLIDING COUPLER BETWEEN HIGH PRESSURE HOSE AND THE PACKER
Packer for Injection with HP-pan-head nipple (Ø 10÷16 mm)
Fine cracks
Ø10 mm, L = 155 mm (not recommended by the author)
Fine to Medium Cracks
Ø13 mm, L = 110 mm
Medium to large cracks
Ø16 mm, L = 110 mm
For medium large to very large cracks without pan-head nipple
Ø 16 mm, L = 125 mm
Ø 20 mm, L = 125 mm
Author recommendations:
finer crack → larger diameter of packer !!
HP-Pan-Head Nipple Ø 16 mm
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3. Flushing of the joint
It is advised to flush the crack with water before injection with PU resin.
This will flush out dust, debris and prime the crack for the injection resin and improve penetration of the product into the crack.
Water in the crack will activate PU resin, but normally the concrete close to the crack is saturated by flushing water. Otherwise a concrete humidity of 6% is enough to ensure a proper reaction.
The flushing may also reveal hidden cracks and help to understand how the crack spreads, develops and will behave under injection.
Blind holes can be eliminated and cavities or honeycombs can be marked for special attention.
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4. Flushing should be started at the lowest point of the crack or the narrowest part of a horizontal crack. When proceeding from one packer to the next, the water shall escape from the crack.
If flush water will not flow into the packer the hole is probably blind. The packer must be removed and the hole closed up with fast setting cement.
A wide crack will allow more volume at a lower pressure than a narrow crack, but always the volume and pressure levels should be increasing slowly.
The crack should be flushed with the highest possible flow volume practical bearing in mind not to exceed the pressure limits allowed by the age, thickness and condition of the concrete.
Always is recommended using a separate pump for flushing with water. If this is not practical the pump must be sufficiently flushed with the cleaning agent like CarboSolv D in the case of Minova CarboTech grouting system.
The reason is to dry the pump and prevent resin from reacting inside the pump.
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5. Flushing of the early-age thermal cracks
Drilling
Vacuum suction of drill powder (borings)
Installing of packers
Water flushing using separate hand pump
Flushing of the early-age thermal cracks
with water through the packers
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6. Drilling method – not recommended
Flushing of the early-age thermal cracks
with water through the packers
Grouting using PUR
Flushing of the early-age thermal cracks with water through the packers – cont.
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7. Resin preparation
The resin has to be prepared with the predetermined quantity of catalyst.
The reaction speed must be adjusted according to the mixing diagrams of Technical Data Sheet from the Producer to make adequate reaction times sufficient to fill the hole with resin, and thus not for pushing already reacted foam.
No reaction with PU resin will occur until the resin comes into contact with water.
The resin must be protected from water, since this will trigger a reaction in the vessel used and might cause the resin to harden or foam prematurely within the injection equipment.
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8. To compare: heavy grouting equipment for cement slurry
Recommended membrane pump for 1-comp. PU resins
Simple pump for 1-comp. PUR resins driven
by boring machine – not recommended
Simple hand pump for 1-comp. PUR resins and epoxy,
useful for water flushing through the packers
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9. Simple hand pump for water flushing through the packers
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Simple hand pump for water flushing through the packers
and membrane pump for 1-comp. PU resins

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Grouting pump for 1-comp. PUR and (acrylic resins) driven by drill machine
– not recommended

11. higher grout output than 2÷3 litres/min.
To avoid concrete fracturing during grouting in fine fissures should not be used:
piston pumps,
higher grout output than 2÷3 litres/min.
Packer and nippels:
- for PUR,
- for epoxy resins,
- for cement slurry.
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Not recommended
Recommended
Selection of the injection tools – cont.

12. Preparation of the injection equipment
It is highly recommended to use separate pumps for water and PU resin injection to prevent contamination and blockages as mentioned above.
The pumps must be thoroughly primed with the cleaning agent like CarboSolv D and CarboSolv S to lubricate and dry the system before starting injection.
The thumb rule is that the viscosity of a resin changes with its temperature:
- Warmer temperature = lower viscosity.
Colder temperature = higher viscosity.
In cold working conditions or very cold leaking water the resin will be more difficult to flow in the pump and the crack.
Therefore pre-heating the resin > +20 °C is suggested.
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13. Injection
The Contractor always has to consult the Technical Data Sheets and Material Safety Data Sheets prior to its use.
The pump will be filled with resin first and charge the hose and gun. It is absolutely vital to keep the resin supply covered from dripping water.
Depending of the situation it is indicated to remove all trapped air in the pump and hoses.
Sequential procedure to remove the trapped air is the following:
- Pumping with loose high pressure hoses first until the air escapes and the resin starts flowing.
- Tightening the high pressure hose and pump.
- Tightening the ball valve and the packer connector.
Connecting the spherical valve, continuation primes the system, closing the valve when the
resin appears.
Connecting the packer head.
The injection will always start at the first packer (i.e. the lowest packer in a vertical crack or the packer at the narrowest end of a vertical crack). Grouting should start at the lowest pressure setting of the pump.
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14. … now start grouting this hole The general sequence of PUR grouting
continue this hole …
The general sequence of PUR grouting
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15. Drilling and PUR (1-comp
Drilling and PUR (1-comp.) injection – sealing of cracks in bottom slab
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16. between high pressure hose
PUR grouting with sliding coupler
between high pressure hose
and the packer
PUR grouting using “grouting gun”
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17. If the resin does not flow through the line into the crack, the pump pressure at the pump will slowly be increased until the resin shows good regular flow.
Pressures may vary between 30 bars to 150 bars depending on the size of the crack, thickness of the concrete and general condition of the concrete. The thumb rule is to allow enough time for the resin to intrude deeply in the structure.
When the resin starts to flow, water will be observed flowing out of the crack first. Grouting will be continued until resin starts to flow from the crack. Then grouting should be interrupted for a few minutes to allow the initial reaction of the resin with the water and then inject again.
The pressure must be maintained so that the resin can react under pressure.
Large spills of resin should be stopped by filling up the crack with wet cotton rags or cotton rags with resin. It is recommended to wait for the resin to cure, and then pump again to fill up the crack and densify the foam gasket.
It is recommended wetting the wall/floor etc. with water and maintaining it wet before the grouting to allow easy removal of the PU foam after curing.
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18. This will seal the injection port and further densify the crack.
A little leakage of resin through the concrete or crack is useful in showing the extent of resin travel.
During the injection under normal circumstances first water will flow from the crack, followed by foaming PU resin.
After this, pure resin will flow from the crack. The pumping will be stopped when the pure resin reaches at least the next packer + half a distance to second next, the packer is not sitting in the hole properly or the refusal pressure is reached.
After injecting a few packers, it is recommended to go back to the first one and re-inject with PU resin.
This will seal the injection port and further densify the crack.
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19. The water bearing crack before and after PUR grouting
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The general sequence of PUR grouting – cont.

20. The water bearing crack after PUR grouting
filled with PUR
line of packers
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The water bearing crack after PUR grouting

21. Re-injecting with water
After the resin injection, small amount water can be re-injected into the ports to cure resin
left behind.
Caution
Semi-reacted resin in the packer may react under very high pressure when the packer is
opened / removed. However this may not show.
Try to post-inject with water before removal. Always wear face shield and protective clothing,
and stand sideways of the packers when you remove them.
Removing packers
The safety precaution is to let the resin cure thoroughly, before removing the packers.
Packers can be removed by cutting flush with the concrete surface or by untying with
spanner or wrench.
The resulting holes can be filled with hydraulic cement and the surface treated as wanted.
Excess resin on the surface can be removed by wire brush, scraper or hand held grinder.
Accidental spills over dry substrates are difficult to remove and stains may be visible
afterwards. Once used packers must never be used again!
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22. Drilling and PUR grouting
in the case of difficult access
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23. Concrete fracturing (spalling) during grouting with PUR
Mistakes:
Piston pump instead to membrane pump.
To high pumping rate.
To short reaction time.
To large foaming rate.
Packer to close to the surface.
Concrete fracturing (spalling) during grouting with PUR
of crack in the concrete wall
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24. Concrete repair of a crack in concrete tunnel lining
– with surface treatment (not recommended)
Grouting pump operator blind!
Adhesive for plugging of crack before injection
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Concrete repair of a crack in concrete tunnel lining
– without surface treatment

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Caution
Injected PU resin in the packer, even after re-injection with water, may not or not wholly react under very high pressure, at least when the packer is not opened / removed. Release carefully the pressure pushing the ball into the packer

26. ”Soda water phenomenon” while grouting using 1-component PUR
18 bar
Grout pressure = CO2 released =
start of foaming
Grout pressure not released
(in the crack)
Grout pressure = CO2 released
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27. ”Soda water phenomenon” with 1-component PUR – cont.
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None reacted 1-comp. PU resin + colloidal silica (1 year after grouting!).
PUR activated by puncturing of rock mass by drilling → grout pressure = CO2 released = start of foaming

28. Recommended mechanical packers for 1-comp. PUR grouting
Non-return ball valve
Recommended mechanical packers for 1-comp. PUR grouting
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29. Non-return ball valve
Non-return ball valve
Not recommended mechanical packers for 1-comp. PUR grouting Existing resin pressure cannot be released!
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30. Recommended mechanical packer for 1-comp. PUR grouting
Non-return ball valve
Non-return ball valve
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31. Recommended mechanical packer for 1-comp. PUR grouting
Non-return ball valves
Not recommended mechanical packers for 1-comp. PUR grouting
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32. 2. Re-injected water into the packer after completed PUR grouting
1. Pre-injecting of packer with water before starting PUR grouting
2. PUR grouting
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Remember: pre-inject packer with water before starting grouting and re-inject after completion of injection.
After the resin injection, small amount of water must be re-injected into the packers to cure resin left behind (especial important while using hydrophobic resins)

33. Penetration of PU resin into the crack
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Penetration of PU resin into the crack
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34. Excellent penetration of PU resin into the crack (and even around the reinforcement bar)
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35. 1 mm PUR in the crack 0.10÷0.30 mm (*)
(*) – note openings along PUR fill caused by shrinkage of concrete. Cracks still were completely dry!
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36. ! ! chemical shrinkage in cm3 / 100 g cement time (log) days months
None convenient time of grouting
time (log)
days
months
chemical shrinkage vs. time for different water/cement contents
Shrinkage causing re-opening of grouted cracks
shrinkage in ‰ !
age in days
chemical shrinkage vs. time for different water/cement contents
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37. Crack and joint repairing in the concrete structures
– general remarks !! !
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38. Rigid or semi-rigid PU resin recommended for grouting of dormant cracks only
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39. End of Part 2
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