Single-layer concrete protection based on sol

Protective Coatings
Dr-Ing Georg Wagner, NTC Nano Tech Coatings, discusses a decorative
anti carbonation and anti graffiti coating
Single-layer concrete protection
based on sol-gel hybrid polymers
W
Cohesive failure
hile the new coating material discussed here is
used for the protection of all concrete infrastructure, the initial focus, when the coating was
first designed, was for road tunnel applications. In fact over
the past 20 years the costs associated with maintenance in
tunnels has increased exponentially. These trends are
resulting in the need for tunnels to last longer. The requirement for best practice has never been more important in
order to achieve:
ɀ Cost efficient design
ɀ Enhance service life
ɀ Reduce maintenance costs
ɀ Highest safety
Some years ago the Swiss Government issued a request
for a new coating material to fulfil new standards in
Switzerland’s numerous tunnels. The scope of this request
is summarised below:
ɀ Increased tunnel safety by reducing pollution and easier,
faster cleaning. Bright, stable and clean tunnels was the primary aim.
ɀ Reduction of maintenance time.
ɀ Simple, chemical free cleaning procedures. Cleaning with
water (low-medium pressure spray) and rotating brush.
ɀ Increased resistance to environmental influences (temperature, moisture, chemical attack from salts, diesel soot,
rubber abrasion etc).
ɀ Protect the value of the investment – robust and durable
coating (one coat to last 30 years).
ɀ Minimisation of risk in application.
ɀ Not critical to application conditions (temperature, moisture).
ɀ Short tunnel closures.
The coating material is a designed solution to meet the
requirements of the Swiss Government Specification. Over
the past seven years several tunnels in Switzerland have
been coated and evaluated and a number of other trials are
also well under way in Europe, USA and Australia.
TUBECOAT
Tubecoat is a new technology coating material produced
from the sol-gel process for highly stressed concrete surfaces. Tubecoat is an organometallic coating, that is, it has
both organic and inorganic polymeric network structures.
Compared with traditional coatings that are inherently
organic (polyurethane, epoxies etc) these new hybrid coatings have some exceptional properties.
Some properties include:
ɀ Good bond strength with substrates (long durability)
ɀ Very high resistance to UV radiation and resistance to
chemicals (acids, bases and solvents)
ɀ Very high resistance to environmental influences (weathering, temperature shock etc)
ɀ Low dirt pick up
ɀ Chemical reactions with surfaces that enable easy application on both new and old surfaces
ɀ Single coat applications possible.
The sol-gel manufacturing process is enabling the creation
of new materials, materials that can be specifically modified
for particular applications and for particular functions.
Author:
Dr-Ing Georg Wagner, Executive Director, NTC Nano Tech Coatings GmbH, Germany
[email protected]; www.ntcgmbh.com
32 PPCJ – June 2015 www.coatingsgroup.com
Protective Coatings
Above: Anti graffiti testing
Above right: Car park floor coating
Technical data
Case studies and architect specified projects
Tubecoat is a poly siloxane-epoxy resin: >97 % solids (very
low VOC), with a coating thickness of (DFT) 120-200µm
3.5 – 4.5m²/kg at 200µm (DFT). Consumption depends on
surface roughness and a finish can be attained in satin or
matte. Thermal resistance is -20°C – 150°C. The two component coating has at least 12 months shelf life in its original sealed containers, with a large range of colours available. With a versatile application range from low temperatures – 3°C - 30°C – to high RH (955) and suitable for damp
surfaces, ie in tunnels and fast application times.
ɀ
Key features and benefits
This paper was presented at the Advances
in Coatings Technology – ACT’14 conference, organised by the Paint and Plastics
Department of the Institute for Engineering
of Polymer Materials and Dyes on October
21-23, 2014 in Sosnowiec, Poland
Below: Road barrier coated with Tubecoat
Below right: Coloured single layer coating
with permanent easy to clean properties
It can be applied to old and new concrete, cement surfaces
and old paint (the old paint surface has to be clean and stable / strong enough bond to the surface). A single coat
application process is possible but, if specified, multiple
coats are possible.
With an exceptional bond strength, the coating has five
times the normal bond strength with concrete, as compared
with other coatings (>3.5N/mm²). It has also been proven
that there is also exceptional bond strength with old paint
(>3N/mm²). It has proven to be durable, UV resistant and
has long term protection against concrete carbonation and
corrosion barrier to chloride ions, barrier to water, barrier
to carbon dioxide, allows water vapour to pass.
Further resistance is achieved against high chemical, solvent and graffiti. Its hydrophobic surface is easy clean / selfcleaning. Overall, improved optical characteristics lead to
continuous reflection properties, which also reduce electricity requirements associated with lighting.
With low maintenance costs there are longer periods of
time between cleaning. So when cleaning is required it is fast,
safe and easy. As there are no chemicals needed for cleaning,
it is both cost effective and environmentally friendly.
Several high traffic road tunnels in Switzerland.
Road safety barriers and noise walls (work for Australian
Road Authority Approval).
ɀ New road safety barriers were high pressure washed and
coated with Tubecoat in separate locations in Melbourne,
Australia’s freeway system (140,000 cars/day).
ɀ In spite of a partially wet surface there were no adhesion
problems with the coating material (>3N/mm²). Coating still
fully cures.
ɀ Application was carried out on both dry concrete and
damp concrete.
ɀ Independent pull off adhesion tests carried out (Average
result >3.8N/mm² cohesive failure of the concrete)
ɀ Application done as a two coat process to a 200µm DFT.
ɀ
Summary of advantages for all stakeholders
Architects:
ɀ Long term asset protection
ɀ Self cleaning assets
ɀ Environmentally Sustainable Design (ESD)
ɀ Concrete protection (anti-carbonation) and permanent
anti graffiti in one coating.
ɀ Blocking efficiency – removes inconsistencies in concrete.
Construction companies:
ɀ One coating that delivers two key properties. Can be
applied as one coat or two coat wet on wet.
ɀ Fast application
ɀ The likelihood of weather interruptions can also be
reduced (can coat damp concrete). These points mean that
the coating can be applied in shorter time periods and be
done when scheduled with less risk of delay.
Asset owner:
ɀ Long-term asset protection
ɀ Low maintenance costs.
33 PPCJ – June 2015 www.coatingsgroup.com