External coating undergoes many
harsh condition of environmental changes so it must have the property of UV
resistant, anti-carbonation, breathability, waterproofness, crack bridge-ability, etc. Generally,
coatings like on Acrylic elastomeric coating, Epoxy polyurethane paint system
and Epoxy phenolic coating systems are proven as best.
IRC: SP-20, has clarified and put
the specification requirement for Acrylic elastomeric coatings:
Coating requirement:
|
Sl No |
Parameters |
Requirement |
Reference |
|
1 |
Specific gravity |
1.35 – 1.4 |
IS 345 |
|
2 |
Solid content |
70 ± 3% |
IS 345 |
|
3 |
UV resistant |
No colour change |
ASTM G 53 / DIN EN 150 – 105 |
|
4 |
IR Spectrum |
As per Acrylic polymer |
IR – Spectrum Meter standard |
|
5 |
Adhesion with concrete |
1.5 N/Sqmm |
ASTM D 4541 -02 DIN 500014 |
|
6 |
Dry film thickness |
200-225 micron per min 2 coats |
|
|
7 |
Coverage |
400-500 gm/Sqm for 2 coats |
|
|
8 |
Physical properties diffusion resistance against carbon-dioxide |
Equivalent to air thickness SD CO2 shall be > 50m |
DIN 53122 Part 1 |
|
9 |
Diffusion resistance against water vapour |
Equivalent to air thickness SD CO2 shall be > 4m |
DIN 52615 |
|
10 |
Waterproofing characteristics |
Percentage reduction in flux should be > 50% |
|
|
11 |
Re-coat-ability |
Min 2-72 Hrs or as per manufacturer specification
with the approval of engineer in-charge |
|
Primer requirement:
a. System
– Single component
b. Base
– Acrylic resin dispersion
c. Curing
– Air cure
d. Colour
– Milk white, transparent application
e. Shelf
life: 6 months or as per manufacturer’s specification
f.
Coverage – 75-100 Gms per Smtr (depending on
surface porosity)
Performance guarantee of coating
system: 5 years
Reference: IRC: SP-20 : 2008,
page No 37 and 38.
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