Revised March 2006
Polyurethane joint sealant for construction purposes
Description Sikaflex-Construction is a one component thixotropic polyurethane based
joint sealant. It cures under the influence of atmospheric moisture to form an
elastomeric material with adhesive properties in some cases without the
need for priming of the substrate.
Uses An elastic joint sealant on cement based substrates such as:
???? Expansion joints in buildings and civil structures above and below
???? Joints in precast concrete elements such as facades and tilt-up panels.
???? External walling and cladding joints.
???? Curtain walling.
???? Retaining walls.
Advantages ???? New Sikaflex-Construction will bond to well cleaned old Sikaflex-
???? Excellent adhesion on all cement based materials.
???? High durability.
???? Good weathering resistance.
???? Easy to use.
???? Short cut off string even after storage.
???? Ready for immediate use no mixing saves time.
???? No potential mixing errors or wastage due to mixed quantities being
greater than required.
???? Can be painted over with many water solvent and rubber based paints
(preliminary tests recommended).
Storage and Shelf Life When stored in cool dry conditions between 10°C and 25°C unopened
Sikaflex-Construction will keep for a minimum of twelve (12) months.
Instructions for Use
Clean sound dry and free of oil grease and surface contaminants such as
form release agents curing membranes and hydrophobic water repellents.
Any loose particles or laitance should be removed with a rotary mechanical
wire brush followed by blowing out with oil free compressed air. Use Sika
cementitious or epoxy mortars for making good spalled or damaged joints.
Priming (Refer Primer Selection Guide for detailed information. This is a
Application Slide unipac into the special applicator gun then either nick the unipac
wrapper at the extrusion end or cut off the very end of the unipac if it contains
partially cured lumpy Sikaflex. Fit the gun with a suitable nozzle that has
been cut to deliver the right bead size.
All primer on joint sides which is generally applied after backer rods or
release tapes are in place (refer joint design section) must have not exceeded
its open time and it must be thoroughly dry and not just skinned over;
otherwise in conditions of rising temperature trapped solvent can blow
bubbles in the uncured sealant.
Very porous substrates such as poorly compacted or cracked concrete must
have their porous bond area surfaces thoroughly sealed to avoid the
possibility of air bubbles being blown into the uncured sealant if the substrate
Extrude the Sikaflex-Construction into the joint ensuring that no air is trapped
in the joint. Wide joints will require more than one pass of the application gun
to make sure that Sikaflex-Construction is in full contact with the sides and
bottom of the joint. Tooling-off the sealant will assist by forcing the sealant
Revised March 2006
Application (continued) into the joint against its sides and back up material; this will also break any
air bubbles and expose any air pockets.
Final tooling of the joint surface can be done effectively with a spatula dipped
in a 20% solution of washing up detergent in water (test to ensure it does not
discolour the cured Sikaflex-Construction) or a profiled piece of raw potato.
When tooling off with detergent solution ensure no solution is allowed to get
onto adjacent joint sides/bonding areas before the sealant has reached the
final tooling stage in those locations. When masking sides of joints for
neatness remove tape before the sealant cures. Always allow sufficient
surface exposed to moisture.
In conditions of low atmospheric humidity say less than 45% R.H. at 20°C or
<60% R.H. At 10°C when early joint movement is anticipated (eg. the joint
has been sealed in the later afternoon sun and at sunset a rapid temperature
drop is expected Canberra or Alice Springs in winter) it is advisable to
spray the surface of the tooled Sikaflex with a fine mist of water to promote
early skinning. Seal joints in walls facing west in the morning.
Cleaning Use Sika Colma Cleaner to remove uncured sealant from tools after first
removing the bulk of the Sikaflex material with a scraper followed by a rag or
paper tissue. Sikaflex Hand Cleaner will remove fresh and partially cured
Sikaflex from the skin. Hardened material can only be removed mechanically.
Joint Design Permissible change in joint width at ambient temperatures:
???? Above 0°C is ±25% of average joint width at the time of sealing
???? Below 0°C is a total of ±12½% of average joint width at the time of
???? Admissible total shear movement is 20% of joint width at the time of
For the successful sealing of joints with Sikaflex-Construction it is essential
that the following guidelines on joint configuration are observed:
For joints up to 12 mm wide width to depth ratio = 1 : 1
For joints over 12 mm wide width to depth ratio = 2 : 1
An approximate rule of thumb for joints in pre-cast concrete
Joint interval (metres)
Joint width (mm)
Up to 2.0
To ensure that the correct width to depth ratio is achieved and to provide a
firm backing against which the sealant can be tooled off and also prevent the
sealant from adhering to the bottom of the joint the space under the Sikaflexconstruction
must be filled with a tight fitting non-rotting non-absorbent
backing material eg. fibreboard combined with a bond breaking tape (eg.
polypropylene or PVC) or alternatively an open cell polyurethane or closed
cell polyethylene backer rod supplied by Sika. Open cell PU backer rod has
the advantages of allowing moisture access to the front and back of the joint
simultaneously facilitating faster curing. Also open cell PU backer rod is
much more compressible than closed cell PE foam thus one diameter rod can
be used in a much wider range of joint widths. Closed cell PE backer rod can
cause bubbling in uncured sealant in rising temperature conditions if its outer
skin is punctured. It is essential that oil or tar impregnated backing materials
are not used.
Revised March 2006
Criteria that have to be observed in designing expansion joints
Usually the joint has the following geometry:
For joint widths up to 12mm
Width = 1 or w=d
For joint widths 12mm to 50mm
Width = 1 or w=2d
For concrete and masonry joints subject
to movement the depth of the Sikaflex in the
joint has to be at least 8mm.
Technical Data (Typical)
Colours Concrete Grey
Density 1.4 kg/litre
Basis Moisture curing polyurethane prepolymer
Priming Refer separate Primer Selection Guide
Application temperature 5°C to 40°C
Service temperature -30°C to 70°C (maximum +40°C in water and temporarily +50°C)
Shore A Hardness (DIN
<35 after 28 days (at 23°C 50% R.H.)
Elastic Recovery (DIN 52
Tensile strength (DIN 52
<0.6 MPa @ 60% elongation @ -20°C
<0.4 MPa @ 100% elongation @ +23°C
Elongation at break (DIN
Tensile strength at break
(DIN 53 455)
Refer Joint Design section
Skinning Time (at 23°C
4 to 6 hours
The bottom of the joint must not restrict
the deformation of the sealant since this
could result in failure during the opening
of the joint. The depth of the joint should
be adjusted by inserting a suitable joint
In corner joints too the insertion of a release
tape or backer rod is required otherwise the
sealant will fall during expansion of the joint.
The edges or corners of
concrete joints are often
weak because of poorly
compacted concrete thus
it is desirable to use
chamfers and recess the
Revised March 2006
Cure rate (at 23°C 50%
2 mm per day
(rough guide only)
Dilute mineral acids
Dilute mineral alkalis
Swimming/spa pool water
Low to Very Low
Consumption Sika Primer 1 13 ) About 4-5m² per litre of primer. As a guide a
) 250 ml can of primer will normally be
) sufficient for about 35-40 running metres of
) 12.5 mm (deep joint).
Approx. 5-8 m²/litre
Sikaflex Estimating Chart
Quantities: a guide to Sikaflex-Construction quantities (for fillet work multiply metre runs per unipac by two).
Joint size in mm Litre Sikaflex-Construction
per metre run
Per unipac (600 ml)
5 x 5 0.025 24
5 x 10 0.050 12
5 x 15 0.075 8.0
10 x 10 0.100 6.0
10 x 15 0.150 4.0
10 x 20 0.200 3.0
10 x 25 0.250 2.4
15 x 10 0.150 3.9
15 x 15 0.225 2.7
15 x 20 0.300 2.0
15 x 25 0.375 1.6
15 x 30 0.450 1.3
15 x 40 0.600 1.0
20 x 10 0.200 3.0
20 x 15 0.050 2.0
20 x 20 0.400 1.5
25 x 12.5 0.310 2.0
25 x 15 0.380 1.6
25 x 20 0.500 1.2
25 x 25 0.630 0.9
30 x 15 0.450 1.3
30 x 20 0.600 1.0
30 x 25 0.750 0.8
40 x 20 0.800 0.8
40 x 25 1.000 0.6
40 x 30 1.200 0.5
Packaging 600 ml unipac per carton of 20
Sika Primers are supplied in 250 ml cans (Flammable)
Sika Colma Cleaner is supplied in 1 litre and 20 litre cans (Flammable)
Important Notes ???? Sikaflex-Construction is best stored at temperatures between 10°C and
25°C in dry areas. The storage temperature should not exceed 30°C for
???? For best results use opened unipac the same day otherwise the Sikaflex-
Construction in the nozzle will cure and have to be removed.
???? When applying sealant avoid air entrapment.
???? Joint movement must not exceed ±25% (above 0°C) of the width of the
joint at the time it is sealed.
???? Joints in low humidity environments should be sprayed with a mist of
water as soon as tooling off is complete to accelerate the curing process
Revised March 2006
and minimise the risk of early movement cracks.
???? For specific chemical resistance please contact our Technical Service
???? If there is no history of a particular coating/paint being applied over cured
Sikaflex-Construction for a period of six months or more an
overpaintability test should be made to determine:
i) that the paint dries properly within the expected time frame.
ii) That if the paint film dries satisfactorily it is not subsequently
softened and/or stained where it comes into contact with the
Sikaflex-Construction when exposed to the heat of the sun.
iii) That the adhesion of the paint/coating is satisfactory to the
Conduct a simple test overpaint a cured sample of Sikaflex-Construction
allow the normal drying time for the coating to elapse and then expose it to a
temperature of 80°C continuously for seven days. Sikas technical
department can conduct this testing.
???? Do not paint Sikaflex-Construction with Sikagard-680S it will not dry
???? Do not use Sikaflex-Construction to seal joints in chlorinated swimming
pools or spa pools because occasional over dosing with chlorine etc. can
eventually cause the Sikaflex-Construction surface to become sticky.
???? Where possible backer rod should be placed in a joint before it is primed.
???? Do not twist or puncture closed cell polyurethane backer rod during
installation this can lead to out gassing. The gas from the backer rod
blows bubbles into freshly applied Sikaflex-Construction during conditions
of rising temperature.
???? Open cell backer rod allows moist air access to the bottom of the joint so
that the Sikaflex-Construction can cure simultaneously from the front and
back of the joint.
???? Sikaflex-Construction should be used with care resealing joints that were
previously filled with silicone sealant. Consult our Technical Department.
???? Not to be used in glazing applications where the Sikaflex to glass bond is
exposed to direct or indirect sunlight or UV radiation.
Handling Precautions Sika sealants are generally harmless provided that certain precautions
normally taken when handling chemicals are observed. The uncured
materials must not for instance be allowed to come into contact with
foodstuffs or food utensils and measures should also be taken to prevent the
uncured materials from coming into contact with the skin since people with
particularly sensitive skin may be affected. The use of protecting clothing
goggles barrier creams and rubber gloves is recommended. The skin should
be thoroughly cleansed at the end of each working period either by washing
with soap and warm water or by using a resin removing cream the use of
powerful solvents is to be avoided. Disposable paper towels not cloth towels
should be used to dry the skin. Adequate ventilation of the working area is
recommended. In case of accidental eye or mouth contact flush with water.
Consult a doctor immediately.
Important Notification The information and in particular the recommendations relating to the application and
end-use of Sikas products are given in good faith based on Sikas current knowledge
and experience of the products when properly stored handled and applied under
normal conditions. In practice the differences in materials substrates and actual site
conditions are such that no warranty in respect of merchantability or of fitness for a
particular purpose nor any liability arising out of any legal relationship whatsoever can
be inferred either from this information or from any written recommendations or from
any other advice offered. The proprietary rights of third parties must be observed. All
orders are accepted subject of our terms and conditions of sale. Users should always
refer to the most recent issue of the Technical Data Sheet for the product concerned
copies of which will be supplied on request.
PLEASE CONSULT OUR TECHNICAL DEPARTMENT FOR FURTHER