1. Concrete repairs, crack sealing
Part 11b)-1
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. Family and company history in civil engineering
NAJDER engineering® is a consulting company as well as a specialist contractor within civil and foundation engineering.
We are preparing technical concepts, design projects, analyses and performing jobs as a subcontractor.
Tomasz Najder joined in the period of Skånska Cementgjuteriet (today Skanska AB) as a member of Supervising Team on the project “Second Dry Dock in Gdynia Shipyard” in Poland.
Tomasz Najder gained his experiences in Stabilator AB (daughter company in Skanska Group) as site manager, project manager and internal consultant (”trouble-shooter”), as Production Manager (Stabilator AB- International Division in Poland), in Polish-Swedish company Stabilator Sp. z o.o. (Skanska Group) as Vice President and Executive Manager – Managing Director.
Anna Elżbieta Najder (wife) owned Polish company Polibeton Sp. o.o. and now Swedish Najder engineering® since 1997 (until 2005 operating as Polimark International) – operating globally.
Anna Monika Najder (daughter) together with Tomasz Najder (as the President of the Board and Executive Manager) owned Polish Najder engineering® operating in Poland.
Family Najder is working within mining, tunneling and civil engineering since six generations.
From the beginning of 2014 company is operating under new name and organization form Najder Engineering AB (AB = Aktiebolag in Swedish → partnerships or limited in English) – with Tomasz Najder as co-owner, Managing Director and Senior Consultant. Anna Elżbieta Najder (wife) is the second co-owner.
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3. Field of activity Foundation engineering and soil investigations.
Reinforcement of existing foundations (underpinning) of industrial buildings, housing estates and ancient monuments (piling, anchors, injections).
Tunneling, rock stability and soil improvement (deep mixing method, high/low-pressure injection, lime-cement columns).
Stabilization of slopes and embankments (geogrids, soil reinforcement, drainage, geotextiles).
Sealing of existing embankments, dams, dikes and waste deposits. Flood defense.
Biological engineering, gabion constructions, coast protection.
Leakage and moisture counteraction (insulations, drainages, sealing injections, dilatation repair) in concrete and brickworks structures.
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4. Various forms of cracking in the concrete
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5. Canyon? No, crack in concrete
Crack in concrete injected using polyurethane resin (PUR)
Jökulsa River in Iceland – canyon
No, crack in concrete
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6. Early-age thermal cracks in the basement of post office building
and communication tunnels under railway yard (Stockholm)
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7. Summary of various forms of cracking in the concrete
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8. The mechanism of early-age thermal cracks
As cement hydrates, it generates heat and the temperature rises. Once the rate of heat loss exceeds the rate of heat generation, the concrete starts to cool and to contract.
If unstrained, the concrete would expand and contract without creating any stresses, but in practice, partial or complete restraint is always present. The difference between free thermal expansion and measured strain is termed the “restrained strain”.
It is only this restrained movement which induces stresses in the concrete and these stresses can cause cracking. If initially the strength of so-called “green concrete” during the first hours of setting and hardening is still low and the tensile stresses high caused by concrete under contraction, cracking occurs – find the next slide.
During first weeks early-age thermal cracks are very fine, but afterwards they are growing in combination with shrinkage.
It must be pointed out that the described phenomenon is natural and common and has nothing to do with bad workmanship.
Please note that early-age thermal cracks appear along vertical and horizontal construction joints.
Such cracks like early-age thermal cracks and settlement cracks are always going through the concrete elements.
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9. Compression
Contraction
Elastic
deformation
Plastic
tension
Elastic
deformation
Frictional change
of length due to
temperature
increase
Elastic
tension
Plastic
deformation
Time
Compressive
stress
Time
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Tensile
stress !
Rupture
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Tensile strenght
Continuous edge restrain of concrete wall cast of the base causing early-age thermal cracks

10. Grouting materials. Proper choice of injection materials for crack repairs
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11. Grout = liquid → solid form in the crack
Grout An injection fluid, generally referred to as grout is a pumpable material (suspension, solution, emulsion or mortar) injected into a soil or rock formation which stiffens and sets with time and thereby changes the physical characteristics of the formation (for consolidation or/and for sealing)
1. Suspensions = particles suspended in water
Water + cement corns (alt. microcements, ultra fine cements, fly ash etc.)
Water + cement corns + fillers (ballast like sand)
liquid → solid form by hydratation
2. Solutions = chemicals diluted in water
Water + sodium/natrium silicates + reactans
Water + colloidal silica SiO2 + NaCl or CaCl2
liquid → solid form by gelling (chemical reaction)
3. Resinous grouts = pre polymers or monomers or isomers
(2 or more components in liquid and/or powder form)
Water + acrylic polimers (hydrogels)
1-comp. and 2-comp. polyurethanes
Urea-silicate resins (foams)
Phenolic foams
liquid → solid form by polymerisation (3-D linking)
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12. Only a chemical reaction would dissolve these bonds.
POLYMERIZATION
Polymerization is the formation of a large molecular chain or network of chains from smaller chemical units. 
In polymerization, permanent chemical bonds hold the molecular chains together. 
Only a chemical reaction would dissolve these bonds. 
Polymerization is different for silicates and organic grouts. 
Organics form three-dimensional networks of chemical chains that are hooked together, whereas silicates tend to form gels through attractive charge effects, which may involve some permanent bonding.
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13. Classification of grouts
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14. Comparison between the range of penetration
Chemicals, polymers
Cementitious grouts
Cement based slurries
Water
PUR EP
OPC, MC
Comparison between the range of penetration
of water and common grouting materials
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15. Classification of grouts – cont. Convenient in low temperatures
See separate slide
See separated slide
Classification of grouts – cont.
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Convenient in low temperatures
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16. “hockey stick” reaction
Polyurethanes (fast-moderate-, slow reacting)
Sodium/natrium silicates
Epoxy resins
Cement based suspensions
“hockey stick” reaction
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17. OPC
MC, UFC
PUR
Permeability limits of water in soil, rock and cracks in concrete
Permeability limits of PUR in soil, rock and cracks in concrete
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18. Description 2- comp. PUR 1- comp. PUR
Chemical differences between so-called 2-component polyurethanes (“dual component” PUR) and 1-component polyurethanes (“single component” PUR)
Description
2- comp. PUR
1- comp. PUR
Base System
Resin = B
Reagents
Hardener = A
Catalysator (accelerator, aktivator) = CAT
Preparation
A + B
B + CAT
Reaction Starts
After Mixing
After Contact with Water
(min 6%)
Reaction Start Time
Almost Immediately
= f (temp.) → (20”÷ 30’)
Variable on Site
(“in situ”)
= f (temp., % CAT) → (1’÷ 6’)
Reaction Start
Set
Factory Pre-Set otherwise option with “accelerators”
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Hydrophilic grout will absorb the water it finds in the concrete or soil (rock).
Hydrophobic grout will repel it and push it away.
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19. pumping pressure + CO2 (expansion pressure) One-component PU resins
Viscosity vs. time
2’÷ 12’
30”÷ 3’ +
0.25 ÷ 10%
x 10 ÷ 30
pumping pressure
pumping pressure CO2 (expansion pressure)
One-component PU resins
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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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20. Sealing of leaking cracks using polyurethane and epoxi resins
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21. Presented crack sealing or bonding by grouting from buildings interior
does not need any excavation from outside
for sealing with alternative methods like covering of the walls using sealing membranes, mastic sealents and adhesives, bitumen coatings etc.
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22. Injection with PUR in concrete
mechanical packer
Injection with PUR in concrete
1 mm
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Permeability limits of water, OPC, MC, epoxy and PUR vs. crack width
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23. Choice of proper grouting material
The main factors for proper choice of any grouting material are the width and geometry of the fissures. Unfortunately water has viscosity lower then all grouting liquids and can enter such narrow cracks like 0,30 mm causing leakage (find the previous slides).
According to many years of my practical experience the best solution for water leaking through these small cracks are so-called 1-component aqua reactive polyurethane resins which are most useful and effective.
Ordinary Portland cement can be used for cracks wider than 2÷3 mm, but not in the case of leaking water in low temperatures like +3÷5 ºC.
Very fine fissures like 0,50÷1,0 mm are available for extremely fine microcements (UFC) with Blaine > 8000 cm2/gm only but with restrictions for low temperature.
Epoxy resins are almost useless for water leaking cracks, especially in the case of cold water.
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24. Successful injection with Ordinary Portland Cement
(OPC)
… in 3.0 mm crack
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25. Limited penetration of OPC and MC based grouts
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26. Fracturing of concrete – to high pump speed
α ≈ 30º
2/3 D
1/3 D
Foam 1
Alternative drilling
Foam 2
Fracturing of concrete – to high pump speed
or to big angle α
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Foam
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Principles for drilling and PUR grouting of cracks in the concrete wall

27. To find the crack
... using “heat pistol” or gas burner and/or by pumping water through the installed packers
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28. Wall Thickness = Drilling distance from crack otherwise ca. 20 cm. 2
Drilling at an angle of ca. 30° in the direction of the crack is recommended. The depth of the bore should be approximately 60÷70% of the thickness of the concrete element.
As a rule of thumb the distance of the drill point to the crack is taken as
Wall Thickness = Drilling distance from crack otherwise ca. 20 cm. 2
The distance between holes can vary between ca. 15 cm and 35 cm, depending on the actual situation. In construction and expansion joints the distance can vary between 30 cm and 50 cm.
For very large cracks, the holes can be drilled directly into the crack to seal the crack over the full length between and around the packers.
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29. Drilling method not recommended
Concrete dust (borings) clogging the drill hole
Core drilling
Rotary-percussive drilling
with the direct suction of borings from the hole
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Different drilling methods for PUR grouting

30. Handhold core drilling machine
The proper methods of drilling are only core drilling (to the left) or rotary-percussive drilling with the direct suction of borings from the hole.
Otherwise ordinary rotary-percussive drilling (like HILTI) wet or dry borings saturated by the leaking water build soft “cake” around the borehole sufficiently closing (clogging) the connection of the hole with the crack.
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Different drilling methods for PUR grouting – cont.

31. Concrete dust (borings) clogging the drill hole
The (too) small steel packers in φ=13 mm boreholes drilled with rotary-percussive drilling machines like HILTI
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32. Different drilling methods for PUR grouting – cont.
Drilling method not recommended
Concrete dust (borings) clogging the drill hole
Rotary- percussive drilling with the direct suction of borings from the hole
Core drilling
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Different drilling methods for PUR grouting – cont.

33. The recommended method of drilling and PUR grouting for cracks and
at the leaking construction joint – cont.
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34. Mechanical packers with HP-pan-head nipple
Sealing of cracks in the concrete with polyurethanes
Mechanical packers with HP-pan-head nipple
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35. Installation of the packers
Packers are mechanical in different sizes. The choice of the packer is in accordance with the size of the crack and the type of resin viscosity.
Usually the larger the crack and the more important the leak, the larger the diameter has to be applied.
The size of the internal diameter of the crack and packer has a repercussion in the pressure needed to activate the transport and distribution of the resin.
A little bit larger may, in certain circumstances, reduce the capital of labour necessary to perform the work, and this will reduce the costs.
According to author’s experience packers with diameter φ=17÷19 mm are the best in most cases.
A correctly sized packer should be inserted into the hole for about 2/3 of its length.
To keep the packer in place during injection the grouting personal must tight the packer with a wrench or spanner by turning clockwise until sufficient tension has been reached.
If the packers is moved completely from the hole during grouting it must be always replaced with a new one.
For packers like φ=17÷19 mm the diameter of boreholes must be optimally 18÷19 mm respectively 20÷21 mm.
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36. The small plastic packers like φ=10 mm
mounted by hammering in φ=11 mm boreholes drilled with rotary-percussive drilling machines like HILTI are useless and dangerous during high pressure grouting.
They can be easily pushed out from the hole by grout!
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37. Not recommended system of drilling and grouting using PU resins
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The small steel packers like φ=10 mm mounted in φ=11 mm boreholes drilled with rotary-percussive drilling machines like HILTI
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The small plastic packers like φ=10 mm mounted by hammering in φ=11 mm boreholes drilled with rotary-percussive drilling machines like HILTI

39. End of Part 1
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