The key to the overall success of all specialised applications is the preparation.
Correct substrate preparation is achieved by the various methods
outlined below. A general guide to the correct technique is determined
by two factors:
1) The condition of the existing substrate and the need to remove any existing coatings, or contaminants
2) The requirements of the subsequent coatings or topping to be applied.
Captive Shot Blasting
Captive shot blasting is the profiling of the substrate by way of
mechanically firing steel abrasives onto the floor surface at great
force to create the desired profile for subsequent coatings. The
process involves containment of the steel grit within in the body of
the machine, which is drawn back and recycled for continuous use.
Captive shot blasting has been proven through studies to be the most
effective form of concrete preparation. Captive shot blasting is up to
20% more effective than other methods of surface preparation such as
diamond grinding.
Captive shot blasting can where appropriate be effective as a
standalone profile for tiles or concrete where a decorative and/or
non-slip finish is required
Diamond Grinding
Diamond grinding is by definition the most practical and widely used
method of concrete preparation, in particular where the desired finish
is not compatible to the more aggressive method of profiling.
By virtue of the numerous combinations and configurations of blade
selection combined with the various machinery available offers a broad
range of solutions to many facets of concrete preparation, such as the
removal of carpet and tile glue, the removal of cementitious screeds
and toppings through to the general cleaning and removal of latent’s
and preparation for subsequent finishes. Another area where diamond
grinding stands alone is in the area of polishing concrete to expose
the aggregate where an architectural finish is required or an ethically
suitable clear finish is desired. Diamond grinding is widely specified
in the rectification of undulating or rain damaged concrete
Scarifying
Scarifying is performed by the use of a mechanically driven drum
containing tungsten tipped discs which aggressively removes coatings or
concrete for the preparation of the substrate to receive high build
trowel on toppings or in the preparation of slab on slab toppings.
Heavy duty scarifying removes the existing substrate and exposes the
underlying coarse aggregate which creates a suitable plane that will
bond to the new concrete overlay or system. In general typical
scarifying depths range from 3mm to 10mm. The result of scarifying is
an exposed aggregate which is a clean and undamaged layer of concrete
ready to provide a strong anchor for the overlay or repair material.
Acid Etching
Acid etching is the reaction of a dilute acidic solution with the
surface laitance resulting in a fine sandpaper like texture suitable
for over coating with thin penetrating sealers and coatings.
Acid etching by definition has in the past not been environmentally
sound. The hazardous fumes associated with hydrochloric acid combined
with the corrosive effect on exposed steel have led to the widespread
condemnation of this method by the engineering profession.
This method has now been refined. A combination of mild organic
detergents, emulsifiers and solvents results in the desired etching
profile whilst not affecting the concrete matrix or having negative
environmental effects.
Acid etching carried out correctly provides for excellent coating
adhesion and penetration by opening up the surface of the concrete.
High Pressure Cleaning
High pressure cleaning is used in conjunction with any combination of
the above methods where the relevant substrate required specific
treatment for the removal of oils, staining and contaminates etc.
Conclusion
The above list of techniques is not exhaustive and it is more than
likely that a repair strategy will involve a combination of methods.
However, when selecting repair techniques, aspects must be considered
other than just the technical.
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