Method Statement for application of SCP to pre fabricated tunnel wall panels
Associated Document
This Method Statement should be read in conjunction with the SCP Method Statement titled
“Method Statement for application of SCP to Concrete Walls and Ceilings” which
describes the general surface preparation and application technique for vertical and overhead
surfaces. ”SCP” generically refers to products manufactured by Spray Lock Concrete
Protection LLC based in Chattanooga TN USA
Notes on Concrete Mix Design
1. AVOID the use of waxy curing membrane admixtures at all times – this admixture
prevents access by SCP 743 to the capillaries in the concrete
2. NOTE that the SCP Optimiser 1000 mix water enhancement product must be applied
to the potable mix water BEFORE any aggregate, cement or admixtures are
introduced
3. NOTE that MCI corrosion inhibitors are not required as SCP 743 will completely fill the
capillaries if applied according to instructions and prevent the ingress of electrolytes
that initiate or continue corrosion of reinforcing steel
Products and Descriptions relevant to prefabricated concrete tunnel wall panels
1.
SCP Optimiser 1000 is a mix water enhancer product applied into the potable mix
water BEFORE any other concrete elements or admixtures are introduced. Note:
BEFORE.
The mix water MUST be potable water quality to gain the benefits of the SCP
Optimiser 1000 which is an increase in the hydration of the free cement in the concrete
mix to gain stronger and more durable concrete over and above the performance of
the ready mix design
2.
SCP 743 is applied as a multi featured concrete treatment solution on concrete
tunnel wall and ceiling panels to deliver moisture proofing, resistance to salt and
chemical attack, surface hardening, densification, protection against ingress of chloride
ions that attack embedded steel and removal of the need for 28 day water ponding,
application and removal of curing membranes, use of moisture membranes and
coatings, and various chemicals for densification, surface hardening and steel
corrosion protection.
SCP 743 is applied in a single spray application that deeply penetrates the capillaries
in the concrete providing permanent moisture proofing and protection against a wide
range of negative impacts on concrete as mentioned above. It can be effectively
applied on both the positive or negative side of pre fabricated concrete panels with
minimum site disruption and it provides early access to other trades.
SCP 743 provides a unique and permanent passive, non destructive catalyzed
colloidal silica gel barrier within the concrete matrix. It has been in use over 25 years
and it should not be confused with temporary, soluble, weakly linked large pore,
thixotropic gels that are formed using sodium silicates, or through free lime reactions
which have been proven to be detrimental to long term concrete integrity. This
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technology is unique and is NOT a sodium, potassium or lithium silicate or oxysilane or
crystalline products used in many other concrete treatments.
Products and equipment required
SCP Optimiser 1000 can be provided in US 5 gallon or EU 20 litre pails or 330 US gallon
totes.
SCP 743 is provided in US 5 gallon or EU 20 litre pails. The product is pre-mixed and ready to
be placed under an Airless Spray Unit after opening the lid. Do NOT add water or any other
liquid into the pail.
Graco Ultra Max II models 395, 495, 695 or 795 Airless Spray Guns (Model 795 can be fitted
with one or two spray outlets), a 0.019” spray tip model 1221, and an extended 25 cm spray
tip rod for spraying 150 mm above substrate. The spray fan should be 200 mm wide when
applied 150 mm perpendicular from the tip to the concrete surface.
Site preparation and Porosity Testing is critical
When using SCP 743 on existing surfaces (see later notes on fabrication sites) - remove all
surface dust, cement dust, grit, particles or contaminants such as paint/ plaster
splashes, oils (including formwork oils) and grease etc that can prevent the penetration
of SCP 743 into the capillaries of the concrete walls and overhead ceilings. Test for
porosity by placing small drops of water at the surface to check rapid absorption (within 60
seconds) – if the drops pond on the surface or run off the concrete immediately they are
applied then the surface impediments must be mechanically removed before testing again.
Concrete which has been burnished on the top by heavy metal power floating will cause
ponding of test water droplets and this burnished surface needs to be removed by grinding
the surface layer to open the pores of the concrete. Test for porosity after grinding or
sanding.
APPLICATION NOTES SPECIFIC TO CONCRETE TUNNEL PANELS
Application Note 1 - SCP Optimiser at the concrete batching plant
Following the mix and dosage instructions provided – apply SCP Optimiser 1000 to the
potable quality mix water before all other elements of the concrete mix – avoiding the use of
any admixture designed to provide a curing membrane in the ready mix concrete as per
NOTE 1 of NOTES ON CONCRETE MIX DESIGN above.
Application Note 2 – SCP 743 at the concrete panel fabrication site
Using the recommended Graco airless spray unit equipped with a short tip length at the gun,
apply SCP 743 to the prefabricated panel as soon as the concrete panel has been floated to a
“wood float” finish with the tip held perpendicular 150 mm above the surface to deliver a 200
mm fan width. Tip Pressure should be 350-400 psi only.
The tip must not be used in a swinging motion as this will alter the angle of spray from the
desired perpendicular angle. The operator needs to be located beside and above the panel
surface.
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The spray fan is overlapped by 50% on each pass thus ensuring a double application of SCP
743 product.
Both surfaces and all edges of the concrete panel need to have SCP 743 applied in this
manner. Repeat spray over the first pass of SCP 743 on each surface. If SCP 743 is quickly
absorbed in some parts of the panel spray these areas again. Use a soft bristle broom to
move pools of product into absorbent areas. Do not let the product pool dry on the surface
Any power floating or surface burnishing of the panels needs to be carried out AFTER the
application of SCP 743.
Panels treated with SCP 743 can be stored under cover 2 hours after treatment or in open
area storage after 24 hours as SCP 743 accelerates the curing process.
Application Note 3 – procedure to treat any cementitious joint sealants in situ
Due to the vertical and overhead plane of the installed concrete panel walls and ceilings a
variation to the spraying technique is required if it is desired to treat any cementitious joint
sealants that may be used between the concrete panels with SCP 743.
For walls, spray horizontal and vertical joints from left to right, bottom to top at a faster rate
(approx 200%) of the speed normally used on horizontal slabs. Repeat the coverage over
the joints each time. A shorter tip extension may be used on the airless spray unit but it is
important that the tip is held perpendicular to the wall surface at all times (do not swing the tip
– walk along with it). By spraying at this rate the tendency for the product to run down the wall
joint surface is minimized. The tip pressure should be 350-400 psi for wall and ceiling
panel joints.
For overhead concrete panels, spray across the joints in 200mm wide strips at a faster
rate (approx 300%) of the speed used on horizontal slabs. Apply coverage a total of
THREE times over the ceiling panel joints. It is important that the tip is held
perpendicular to the ceiling surface at all times (do not swing the tip – walk along with
it). By spraying at this rate the tendency for the product to drip from the ceiling is
minimized. Note carefully which joints have been sprayed to ensure that all joints are
treated.
By applying repeated coats at reduced pressures there should not be too much loss of
product through running down walls or dripping from ceilings. The speed of application can be
matched to the porosity of the concrete joint material to deliver this result.
Application Note 4 - treatment of wall and ceiling penetrations
Apply SCP 743 to all exposed wall and ceiling penetrations taking care to clean these areas
of dirt and contaminants (such as timber formwork oils etc) before application with the
recommended Graco Airless Spray Unit fitted with the fan spray nozzle at the appropriate
pressure settings.
These steps will assist in preserving the moisture barrier qualities of SCP 743 in the concrete
matrix but normal sealing and waterproofing coverage products procedures should still be
followed to ensure overall integrity of the concrete slab, and construction / expansion joints.
SCP 743 is not a crack repair technology although very shallow surface cracks under 1.5 mm
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will have a moisture barrier protection if fully covered and penetrated by SCP 743 prior to
application of the appropriate crack repair solution.
Release of treated areas to other trades
Areas requiring SCP 743 treatment need only to be closed to other trades during the
application process and can be released to other trades immediately after treatment when the
surface is dry if no other surface coatings are planned.
Where a surface coating is planned, the area should be closed for 24 hours (not necessary if
the area had been sand blasted before treatment) then flushed with water, removing all
purged salts, particles, sediments or other contaminants that may be released from the
concrete by the application of SCP 743. The treated surface can then be prepared in
accordance with the coating manufacturer specifications.
SCP 743 is an excellent primer for surface treatments as it addresses the causes of potential
early coating failures such as alkaline capillary moisture accumulation, saponification, laitance
effects etc.
Precautions
SCP 743’s spray mist is not hazardous to breathe in small concentrations. However, use of a
face mask over nose and mouth is recommended during application in confined spaces or for
large areas of application due to the risk of displaced concrete dust and other surface grit.
Refer to the MSDS.
Like many construction materials including fresh concrete itself, SCP 743 contacting glass or
aluminium trims should be avoided wherever possible. If sprayed flush with water and do not
not allow SCP 743 to dry on the surfaces since glass and aluminium may be etched.
Do not apply on frozen substrates or when temperature is near freezing. Do not apply if rain
showers are imminent within two hours and stop application (and record treated area
boundaries) if rainfall begins without warning as application over very wet surfaces can result
in operators not applying the product with the correct 50% overlap patterns.
Product Description
SCP 743 is a single coat spray applied product that fully penetrates the capillaries in the
concrete providing permanent moisture proofing and protection against a wide range of
negative impacts on concrete. It can be effectively applied on either the positive or negative
side of concrete structures with minimum site disruption and it provides early access to other
trades.SCP 743 provides a unique and permanent passive, non destructive catalyzed
colloidal silica gel barrier that has been in use over 25 years and it should not be confused
with temporary, soluble, weakly linked large pore, thixotropic gels that are formed using
sodium silicates, or through free lime reactions which have been proven to be detrimental to
long term concrete integrity. This technology is unique and is NOT a sodium, potassium or
lithium silicate or oxysilane or crystalline product used in many other concrete treatments.
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Technical Data in brief
Physical: Liquid
Colour: Cloudy White (dries clear)
Odour: None
Specific Gravity: 1.10
pH: 11.5
Flammability: None
Toxicity: None
VOC/ VOS Content: None
Surface Bond Quality: Excellent
Paintability over product: Excellent
Clean Up: Water
Environmental Impact: None/ Neutral
Chloride Screenability: Excellent
User Status: User Friendly
Slip effect after treatment: Nil
END
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