MODEL SPECIFICATION
FOR PROTECTIVE COATINGS
FOR CONCRETE
Civil Engineering Department
Hong Kong Government
July 1994
- 2 ­
c Hong Kong Government
First published, July 1994.
Prepared by :
Civil Engineering Department,
Civil Engineering Building,
101, Princess Margaret Road,
Homantin, Kowloon,
Hong Kong.
Standing Committee on Concrete Technology members:
R.H. Pilling (Chairman)
W.M. Chan
C.S. Chung
Y.L. Lee
W.C. Leung
K.C. Ng
P.J. Osborne
H.W. Pang
P.L. Pang
C.W. Poon
W.Y. Tang
This publication is available from:
Government Publications Centre,
General Post Office Building,
Ground Floor,
Connaught Place,
Hong Kong.
Overseas orders should be placed with:
Publications Sales Section,
Information Services Department,
4th Floor, Beaconsfield House,
Queen’s Road Central,
Hong Kong.
Price in Hong Kong : HK$42
Price overseas : US$14(including surface postage)
Cheques, bank drafts or money orders must be payable to HONG KONG GOVERNMENT
- 3 ­
FOREWORD
This Model Specification lays down the quality of materials, the
standards of workmanship, the testing methods and the acceptance criteria
for protective coatings for concrete, appropriate to various aggressive
environments and conditions, in works undertaken for the Hong Kong
Government. It has been prepared in such a manner that the clauses
contained herein should be used as model clauses for the preparation of a
Particular Specification and should be modified or added to where necessary
to suit the requirements of individual projects.
In order to assist in the preparation of a Particular Specification, notes
are provided on adjacent pages against some of the clauses to amplify the
intent of these clauses.
This Model Specification was produced under a consultancy study
monitored by the Standing Committee on Concrete Technology, with the
final editing and production carried out by the Standards Unit of the Civil
Engineering Department.
July 1994
- 4 ­
- 5 ­
CONTENTS
Page
No.
GENERAL
01
Abbreviations
13
SUBMISSIONS
02
03
04
05
06
07
08
09
10
11
12
Supply of information
Coding system
Storage life
Method of using paint components
Surface preparation of concrete
Dry film thickness and coverage
Overcoating
Physical properties
Durability
Health and safety
Maintenance
15
15
15
15
15
15
17
17
17
17
19
GENERAL CONCRETE COATING REQUIREMENTS
13
14
15
16
17
18
Surface preparation for uncoated concrete
Surface preparation for painted concrete
Coating application for dry concrete surfaces
Coating application for damp concrete surfaces
Paint finish
Quality control on site
21
21
23
25
27
27
SPECIFIC REQUIREMENTS FOR
CARBONATION RESISTANCE
19
20
21
New construction and older construction
Back pressure acting on coatings
Concrete subject to graffiti
29
35
35
SPECIFIC REQUIREMENTS FOR CHLORIDE
RESISTANCE
22
Concrete subject to chloride spray and carbonation
35
- 6 ­
Page
No.
23
24
25
Concrete subject to cyclic immersion in seawater
Concrete water retaining structures subject to salt spray
Concrete subject to chloride back-penetration from soil
35
37
37
SPECIFIC REQUIREMENTS FOR CHEMICAL
RESISTANCE
26
27
Resistance to sewage
Resistance to highly aggressive chemicals
37
39
SPECIFIC REQUIREMENTS FOR
ACTIVE/DYNAMIC CRACK BRIDGING
RESISTANCE
28
Concrete subject to active cracks
39
SPECIFIC REQUIREMENTS FOR TIDAL WORK
29
30
Concrete subject to cyclic immersion in seawater
Wet concrete surfaces
39
41
APPENDICES
APPENDIX 1
45
DETERMINATION OF THE WATER VAPOUR
DIFFUSION RESISTANCE OF COATINGS
1.1
1.2
1.3
1.4
1.5
1.6
Scope
Test substrate
Procedure : preparation of specimens
Procedure : determination of water vapour transmission rate
Calculation
Reporting of results
45
45
45
45
46
47
- 7 ­
Page
No.
APPENDIX 2
49
DETERMINATION OF THE CARBON DIOXIDE
DIFFUSION RESISTANCE OF COATINGS
2.1
2.2
2.3
2.4
2.5
2.6
2.7
Scope
Test substrate
Equipment
Procedure : preparation of specimens
Procedure : determination of gas flow rate
Calculation
Reporting of results
49
49
49
49
50
50
52
APPENDIX 3
55
DETERMINATION OF THE WEATHERING
RESISTANCE OF COATINGS
3.1
3.2
3.3
3.4
3.5
Scope
Test substrate
Equipment
Method
Reporting of results
55
55
55
55
56
APPENDIX 4
57
DETERMINATION OF THE SALT SPRAY
RESISTANCE OF COATINGS
4.1
4.2
4.3
4.4
4.5
Scope
Materials
Procedure : preparation of specimens
Procedure : determination of salt spray resistance
Reporting of results
57
57
57
59
59
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Page
No.
APPENDIX 5
61
DETERMINATION OF THE SALT WATER
IMMERSION RESISTANCE OF COATINGS
5.1
5.2
5.3
5.4
5.5
Scope
Materials
Procedure : preparation of specimens
Procedure : determination of salt water immersion resistance
Reporting of results
61
61
61
63
63
APPENDIX 6
65
DETERMINATION OF THE DYNAMIC CRACK
BRIDGING RESISTANCE OF COATINGS
6.1
6.2
6.3
6.4
6.5
6.6
Scope
Materials
Equipment
Procedure : preparation of specimens
Procedure : determination of crack-bridging resistance
Reporting of results
65
65
65
65
66
67
APPENDIX 7
71
DETERMINATION OF THE WATER
PERMEABILITY RESISTANCE OF COATINGS
7.1
7.2
7.3
7.4
7.5
7.6
7.7
Scope
Materials
Equipment
Procedure : preparation of specimens
Procedure : determination of water permeability
by laboratory test rig
Procedure : determination of water permeability
by CLAM Tester
Reporting of results
71
71
71
72
73
74
74
- 9 ­
Page
No.
APPENDIX 8
77
DETERMINATION OF THE BOND
STRENGTH OF COATINGS
8.1
8.2
8.3
8.4
8.5
8.6
Scope
Materials
Equipment
Procedure : preparation of specimens
Procedure : determination of bond strength
Reporting of results
77
77
77
77
78
79
APPENDIX 9
83
DETERMINATION OF THE RESISTANCE
TO AGGRESSIVE LIQUIDS OF COATINGS
9.1
9.2
9.3
9.4
9.5
Scope
Materials
Procedure : preparation of specimens
Procedure : determination of resistance to aggressive
liquids
Reporting of results
83
83
83
84
85
APPENDIX 10
87
DETERMINATION OF WATER UPTAKE
OF COATINGS
10.1
10.2
10.3
10.4
10.5
Scope
Materials
Procedure : preparation of specimens
Procedure : determination of water uptake
Reporting of results
87
87
87
88
89
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Page
No.
APPENDIX 11
91
DETERMINATION OF THE IMPACT
RESISTANCE OF COATINGS
11.1
11.2
11.3
11.4
11.5
11.6
Scope
Materials
Equipment
Procedure : preparation of specimens
Procedure : determination of impact resistance
Reporting of results
91
91
91
91
92
93
APPENDIX 12
97
DETERMINATION OF THE ALGAE
RESISTANCE OF COATINGS
12.1
12.2
12.3
12.4
12.5
12.6
Scope
Materials
Apparatus
Procedure : preparation of specimens
Procedure : determination of algae resistance
Reporting of results
APPENDIX 13
97
97
97
97
98
98
101
METHODS FOR THE ANALYSIS OF COATING SAMPLES
13.1
13.2
13.3
13.4
13.5
13.6
Scope
Method : determination of volatile content
Method : determination of fineness of grind
Method : determination of viscosity
Method : determination of specific gravity
Additional Testing
101
101
101
101
101
101
- 11 ­
Page
No.
APPENDIX 14
103
METHODS FOR CHECKING THE CONTINUITY OF
FILM FORMING COATINGS ON CONCRETE
14.1
14.2
14.3
Scope
Method : determination of thickness
Method : determination of continuity
103
103
103
APPENDIX 15
105
SIMPLE METHOD FOR CHECKING THE ADHESION
OF FILM FORMING COATINGS ON CONCRETE
15.1
15.2
Scope
Method : cross-cut test
105
105
- 12 ­
Notes
- 13 ­
GENERAL
Abbreviations
01
(1) Abbreviations used in this Specification shall have the following
meanings :
ASTM
BS
SISIR
: American Society for Testing and Materials
: British Standard
: Singapore Institute of Standards and Industrial
Research
DFT
: dry film thickness
HOKLAS : Hong Kong Laboratory Accreditation Scheme
OPC
: ordinary Portland cement
PVC
: polyvinyl chloride
R-value : equivalent air layer thickness
SD-value : water vapour diffusion resistance
SBR
: styrene butadiene rubber
UV
: ultra violet
(2) Abbreviations of units of measurement used in this Specification
shall have the following meanings :
o
C
cm
cm2
cm3
cm2/s
g
g/L
g/cm3
g/m2
Hz
kg
kg/m3
kgf
kgf/cm2
L
L/m2
L/m3
m
m2
m3
mL
mm
mol
MPa
m2s
MΩ
m/s
mL/m2s
mol/cm3
: degrees Celsius
: centimetre
: square centimetre
: cubic centimetre
: square centimetre per second
: gram
: gram per litre
: gram per cubic centimetre
: gram per square metre
: hertz
: kilogram
: kilogram per cubic metre
: kilogram force
: kilogram force per square centimetre
: litre
: litre per square metre
: litre per cubic metre
: metre
: square metre
: cubic metre
: millilitre
: millimetre
: molarity
: megapascal
: square metre second
: megaohm
: metre per second
: millilitre per square metre second
: molarity per cubic centimetre
- 15 ­
mol/s
s
µm
%
:
:
:
:
molarity per second
second
micrometre
percentage
SUBMISSIONS
Supply of
Information
02
Prior to the Engineer giving approval of a particular paint type, the
Contractor shall supply information which will satisfy Clauses 03 to
11, and independent test certificates from a HOKLAS or similar
accredited laboratory, traceable to the paints proposed, demonstrating
that they comply with the requirements of this Specification. The
Contractor shall also supply information on the surface finish, colours,
chemical properties, weathering resistance under exposure to sunlight,
previous and existing applications of the paint in Hong Kong. All such
information shall be independently verified; any tests or case histories
on structures shall have been witnessed by an independent,
accountable third-party such as a HOKLAS accredited laboratory.
Coding System
03
All primers, paints and solvents to be used in the works shall be
identified by a unique coding system, relating to the batch of raw
materials from which the product was manufactured and the date of
manufacture.
Storage Life
04
Storage life shall normally be a minimum of one year. If the storage
life is known to be shorter, the expiry date must be marked on the
container prior to dispatch from the manufacturer’s factory.
Method of
Using Paint
Components
05
Preparation and application techniques for all components of the paint
system shall be stated. This information shall include the methods of
mixing to be used and the maximum dilutions, if any, by solvents or
water.
Surface
Preparation
of Concrete
06
Recommendations for preparing the surfaces of concrete shall be
given, including the following :
(a)
(b)
(c)
(d)
Dry Film
Thickness
and Coverage
07
the minimum age,
the maximum moisture content and measuring method,
the equipment to be used for preparing the concrete
surface, and
the materials suitable for filling defects in the concrete.
The minimum and maximum DFT limits for each component of the
paint system shall be given for a temperature of 27 ¡ ηC. The
corresponding coverage in L/m2 shall be quoted for prepared concrete
surfaces typical of low strength (Grade 20) and high strength
(Grade?40) concrete cured under site conditions, in order to achieve
recommended DFT values.
- 16 ­
Notes
- 17 ­
Overcoating
08
Drying and overcoating times of the pretreatments and coats of the
paint system shall be given for a temperature of 27 ¡ ηC and a relative
humidity of 80 ¡ 5 %
. I nf or mati on s houl d al s o be gi ven ont he li m
it
of temperature and humidity at which painting work should cease.
Physical
Properties
09
All components of the paint system shall be capable of unique
identification such that any substitution, dilution or adulteration of the
paint can be identified. The Contractor shall provide test data and
methods of test for the following properties of each applicable primer,
paint and solvent used in the system :
(a) specific gravity,
(b) volume of solids,
(c) viscosity,
(d) fineness of pigment grind,
(e) infra-red spectography,
(f) pyrolysis gas chromatography of the binder,
(g) ash content at 450ηC.
Durability
10
(1) The suitability of the coating for application on damp, alkaline,
cement-based materials shall be stated.
(2) The decorative life of the paint shall be stated, in terms of the
colour-fastness of the finish coat and resistance to chalking, loss of
gloss and atmospheric dirtying.
(3) The life of a paint system prior to the need for recoating shall be
at least 10 years. Examples shall be cited of where the paint system
has achieved this life.
(4) The paint system shall be capable of withstanding cleaning with
hot water (in the range between 40ηC and 50ηC), detergent and
scrubbing action without losing adhesion, softening or changing in
colour or gloss.
Health and
Safety
11
(1) The Contractor shall supply health and safety data relating to the
storage and application of all components of the paint system. As a
minimum, the check list contained in Table?1 shall be completed.
(2) The effects of solvent and vapour build-up on the environment
in the vicinity of the paint applicator shall be monitored, and the loss
of volatiles per unit area of paint in terms of minimum air exchange
rates in confined areas shall be determined.
(3) The in-service performance of the paint under conditions of fire
shall be given, making particular reference to the surface spread of
flame, and the toxicity and opacity of combustion products.
- 18 ­
Notes
- 19 ­
(4) The Contractor shall also supply information on the long term
effects of volatile or leachable components of the paint system upon
the environment, with particular reference to leachable heavy metal
contents such as mercury based algicides or lead driers.
Table 1 : Check list of health and safety information
PRODUCT NAME
USES
COMPOSITION
PHYSICAL AND CHEMICAL PROPERTIES
HEALTH HAZARDS
FIRE HAZARDS
STORAGE PRECAUTIONS
TRANSPORT PRECAUTIONS
HANDLING/USE PRECAUTIONS
(including advice on personal protective equipment)
DISPOSAL PRECAUTIONS
EMERGENCY ACTION
Fire, spillage, first aid
ADDITIONAL INFORMATION
Ecological hazards
Relevant regulations
Advice to Occupational Medical Officers
References
NAME, ADDRESS AND TELEPHONE NUMBER OF SUPPLIER
REFERENCE NUMBER, DATE OF ISSUE
Maintenance
12
(1) The Contractor shall provide information on the methods of
preparation to be used in the event that recoating of the painted surface
is required.
(2) The Contractor shall state which types of paint, other than the
original product, are compatible with the finish coat for recoating
purposes.
(3) The Contractor shall provide information on the technique
which can be used to repair local damage to the coating, with particular
reference to colour and gloss matching of finish coats applied after a
time lapse of 5 years.
- 20 ­
- 21 ­
(4) The Contractor shall provide information on the most
appropriate techniques for cleaning of the finish coat to remove surface
soiling, with particular reference to ease of removal of graffiti or glued
posters, where possible, without damage to the existing finish.
GENERAL CONCRETE COATING REQUIREMENTS
Surface
Preparation
for Uncoated
Concrete
13
(1) Surfaces to receive coatings shall be sound, free from laitence
and contamination such as oils and greases, and shall be at least 28
days old.
(2) The concrete surface shall be prepared by high pressure jetting
with potable water, either with or without added abrasive, wire
brushing or by other means approved by the Engineer, to provide a
strong, hard surface.
(3) Areas of contamination shall be removed by the use of
appropriate solvents, followed by thorough cleaning of the concrete
with potable water.
(4) Shrinkage cracks of width less than 0.3 mm, blow holes or other
defects in the finished concrete surface shall be filled with a levelling
compound compatible with the paint system to be applied; the
compound shall be knifed into defects and tight-trowelled to remove
all surplus materials.
(5) Shrinkage cracks of width greater than 0.3 mm shall be sealed
by resin injection, and movement joints shall be provided at joints
between concrete and blockwork as instructed by the Engineer.
(6) The prepared surface shall be protected against contamination
when it is to be left for periods of more than one week before coating.
Surface
Preparation
for Painted
Concrete
14
(1) The adhesion of existing paint layers to the concrete surface
shall be evaluated initially by a cross-cut test, in accordance with
Appendix?15.
(2) Measurements of cross-cut adhesion shall be made in sufficient
numbers to represent one reading per 10?m2 of coated surface for the
first 100?m2 evaluated, then three readings per 100?m2 thereafter.
(3) The adhesion of existing paint shall be deemed to be satisfactory
provided 75% of the cross-cut surface remains attached to the concrete
and provided the surface is free from cracking, blistering or heavy
chalking.
- 22 ­
Notes
Clause 15
This Clause relates to applications on building structures and civil engineering structures exposed to the weather,
away from the influence of marine spray or other sources of regular wetting.
- 23 ­
(4) Compatibility tests shall be undertaken to establish whether the
new paint will bond to the existing paint. A trial area of 5?m2 shall be
used, cleaned in accordance with Clause?13(2), and the paint system
applied in accordance with the manufacturer’s instructions. Records of
actual coverage rates used on the trial area shall be made available to
the Engineer. After 14 days, pull-off tests shall be made in accordance
with Appendix?8. The DFT shall also be determined for each paint
layer, to be tested by a travelling microscope in a manner similar to
that stated in Clause 1.3(6) at Appendix 1.
(5) Failure to satisfy the requirements of Clause?14(3) or 14(4) will
mean that the existing coatings must be removed by using hot air or
chemical strippers, and the surface finished by high pressure water
jetting with or without abrasive added, in accordance with
Clauses?13(2) to 13(6).
Coating
Application
for Dry
Concrete
Surfaces
15
(1) All concrete surfaces to receive paint shall be dry at the time of
application. Sufficient drying time shall be allowed either after
construction or after wet preparation methods, to satisfy either one of
the following requirements :
(a)
Moisture meter readings is consistently less than 5%.
(b)
There is no moisture retained behind a 1?m x 1?m
polythene sheet, taped securely onto the concrete surface
to form a seal for 24 hours.
(c)
Internal humidity measurements within the concrete is
η?75% when measured by Sereda probe or other methods
approved by the Engineer.
(2) Prior to applying the paint, a test area shall be prepared on the
structure to be painted, except where a compatibility test has already
been undertaken in accordance with Clause 14(4). The complete paint
system shall be applied in accordance with the manufacturer’s
instructions, including any primers and undercoats, to an area of not
less than 5?m2.
(3) The actual consumption in L/m2of the various coats of the paint
system shall be recorded in the trial area, in order that due allowance
may be made for rough, irregular or exceptionally absorbent concrete.
(4) When the paint system has cured for 14 days, a test of surface
adhesion shall be made in accordance with Appendix?8. The average
bond of 3 dollies to the concrete, via the completed coating system,
shall be satisfactory. A core sample shall be taken from the test area
for measurement of the DFT. Should the minimum and mean DFT
- 24 ­
Notes
Clause 16
This Clause relates to applications on coastal works subject to marine spray.
- 25 ­
values of the core sample be less than those specified, the coverage
rates for the paint shall be proportionally increased for the duration of
the Contract.
(5) If the bond strength results are not satisfactory, the concrete
surface shall be cleaned using high pressure water jetting in accordance
with Clause?13(2), followed by re-application and re-testing of the
coating in accordance with Clauses?15(1) to 15(4).
(6) Coatings shall only be applied during favourable weather
periods, when rainfall is not expected for the following 12 hours.
(7) The dew point shall be at least 5ΗC lower than the temperature
of the concrete surface before painting commences.
(8) Painting using water based paints shall not commence whilst the
relative humidity is above 85% or where it may be expected to exceed
90% during the 12 hour curing period.
(9) Primers, undercoats and finish coats may be applied in
accordance with the manufacturer’s instructions using brush, roller,
spray or other technique to achieve the desired surface finish. Brush
application of primers is the preferred method, working the paint into
the concrete pores.
(10) Where brush or roller techniques are used, the brushes or roller
heads shall be used for the day only and then discarded. The
equipment shall not be cleaned for re-use.
(11) Where spray equipment is used, all cleaning fluid shall be
purged from the equipment using undiluted paint prior to painting. All
contaminated paint used for purging equipment shall be discarded and
shall not be used in the works.
(12) Except where airless spray equipment incorporating a nozzle
mixing device is employed when two-component materials are used,
each component shall be thoroughly stirred before mechanical mixing
of the whole units together; part batches shall not be used.
(13) For multiple coat applications, the manufacturer’s stated
minimum and maximum overcoating times for the prevailing weather
conditions shall not be breached, and successive coats shall have
slightly different colour shades to assist in achieving uniform coverage.
Coating
16
Application
for Damp
Concrete Surfaces
(1) Paint for application onto damp concrete surfaces shall be
specifically formulated for tolerance to moisture during application,
cure and in service.
- 26 ­
Notes
Clause 17
Severe drying can be taken to be a wind velocity of 3 m/s at 27 ± 2ΗC and 60 ± 5% relative humidity for 6 hours.
Clause 18
The frequency of carrying out the quality control tests listed at Appendix 13 depends on the size of the protective
coating contract or when the quality of the coating materials are suspected to have been changed.
The frequency of carrying out wet film thickness test is not fixed and is performed as required by the contractor and/or
engineer to ensure adequate film thickness has been applied.
The frequency of testing of dry film thickness of the protective coating by an approved laboratory is normally 1 per 50
square metres of applied coating.
The tests outlined in Appendix 13 are used as quality control tests to compare the properties of the coatings samples
before and during coating works. The basic acceptance criteria is that the average of the results from an individual
test is equal to the properties measured before the coating work and is within the agreed standard deviation which
may be obtained from the coating suppliers.
Responsibilities for tests and test results representation need to be specified in the Contract, e.g. 3 pull-off tests to
form a sample set and one sample set per 50 m² of applied coating or per production of one continuous application
shift, whichever is less.
The bond strength measured from a site test is normally slightly lower than that obtained from a laboratory test.
However, the acceptance criterion of average bond strength being above 1.2MPa mentioned in Clause 8.5(7) at
Appendix 8 should not be relaxed as this should be achievable for coatings applied properly.
- 27 ­
(2) All concrete surfaces to receive paint shall be surface-dry at the
time of application, including any cracks or other defects that may hold
water. The concrete surface shall leave no mark when a sheet of pale
blue blotting paper is pressed uniformly onto the concrete.
(3) Where the requirements of Clause?16(2) cannot be satisfied,
temporary protection shall be provided to encase the concrete and paint
applicator and prevent moisture penetration, ensuring adequate
ventilation is provided.
(4) The paint shall be applied in accordance with Clauses?15(2) to
15(13).
(5) Deposits of salt crystals which collect on coated surfaces must
be washed off with potable water and the surface allowed to dry, prior
to applying further coats of paint.
Paint Finish
17
All paints shall be free from cracking, wrinkling or other defects when
exposed to severe drying conditions.
Quality
Control on
Site
18
(1) Prior to commencing painting works, the Contractor shall
provide samples of all paints to be used of not less than one litre each
in sealed containers, for testing by the Engineer, on each delivery of
paint to site.
(2) During the execution of the painting works the Engineer shall
randomly select samples of paint for comparison with the initial
samples in accordance with the methods stated in Appendix?13.
(3) The Contractor shall store all empty paint tins which have been
used in the Works, along with site delivery tickets, for inspection by
the Engineer who shall then authorize disposal of the tins.
(4) For coatings subject to aggressive liquids, there shall be no signs
of defects, such as pin-holes, cracking and blistering, on the surface .
The electrical continuity of the coating shall be measured in
accordance with Appendix?14, if instructed by the Engineer.
(5) Areas of coating which do not comply with the specified
minimum DFT shall have a further coat applied to make good the
deficiency. Where the manufacturer’s maximum overcoating time has
been exceeded, the surface shall be lightly roughened in accordance
with the manufacturer’s recommendations prior to paint application.
(6) The adhesion of the coating to the concrete shall be checked at
randomly selected locations by the cross-cut test in accordance with
Appendix?15. Should low adhesion be found, defined as more than
25% of the coating being pulled away, further investigation by dolly
pull-off testing is required.
- 28 ­
Notes
Clause 19
The general purpose of applying anti-carbonation coatings is to protect buildings and structures directly exposed to
the atmosphere and ingress of carbon dioxide, and to satisfy aesthetic considerations.
The coating generic types expected to have good performance are acrylic, vinyl and polyurethane. The generic types
not likely to perform well are polyethylene, epoxy, tar epoxy, chlorinated rubber, bituminous, cementitious, silicone
and silicate.
The recommended R-values of coating systems for different concrete grades for both new and older construction are :
(a)
New Construction
Concrete
Grade
R-Value
(m)
15
20
25
35
45
150
100
50
25
25
The R-values quoted are designed to prevent the carbonation front reaching the steel reinforcement in a 60
year life cycle, assuming the cover is not less than 25 mm. Where the cover is less than 25 mm, the R-value
may need to be increased to achieve the 60 year life.
(b)
Older Construction
Concrete
Grade
R-Value
(m)
15
20
25
35
45
300
300
200
100
25
The R-values for old concrete have been calculated for a 5 year old structure, carbonating rapidly. The R-value
should limit further carbonation of the concrete from its present level (x mm) to (x + 5 mm) in a further 55
years.
In considering older construction, for structures of age > 5 years, use of the R-values in the above table will
limit carbonation to less than 5 mm over 60 years life. For younger structures (age < 5 years), the carbonation
may be more than 5 mm over the remaining years.
The above recommended R-values for older construction are only for guidance. For old structures with
sufficient carbonation data from a detailed survey, the Engineer should make reference to the notes on p.30
and p.32 in the calculation of the appropriate R-values for application of anti-carbonation coatings.
It is important that the coating achieves the R-value at the minimum expected DFT following application on site. The
target value for DFT (target mean DFT) is calculated from experience as the minimum DFT plus 33%.
The target mean DFT shall be the average DFT achieved by the contractor. If either the minimum DFT measured on site
is less than the specified minimum DFT or the average DFT on site is less than the specified target mean DFT, then a
thicker coating will need to be applied to meet the specifications.
The dry film thickness (DFT) shall be converted to wet film thickness (WFT), allowing for losses, to get a correct
coverage (L/m²). The target mean WFT shall be used by the contractor/supplier to calculate actual coverage rates and
not the minimum DFT or WFT which is commonly done.
- 29 ­
SPECIFIC REQUIREMENTS FOR
CARBONATION RESISTANCE
New
Construction
and Older
Construction
19
(1) The carbon dioxide diffusion resistance of the paint system,
measured in accordance with Appendix?2, shall be expressed in terms
of an R-value.
(2)
m.
The required minimum R-value for the paint system shall be ......
(3) The DFT used to calculate the R-value for the paint system shall
be the minimum DFT to be achieved in service. The target mean DFT
shall be greater than the minimum DFT by 33%.
(4) The paint shall be applied in two coats. The minimum DFT
shall be not less than 150?µm.
(5) The SD value of the paint system at the mean DFT shall not
exceed 4?m equivalent air layer resistance and shall be measured in
accordance with Appendix?1.
(6) The adhesion of the paint system, measured in accordance with
Appendix?8, shall be satisfactory.
(7) The paint system shall not support algal growth, when measured
in accordance with Appendix?12.
(8) Water uptake by the paint system shall be zero when measured
in accordance with Appendix?10.
(9) The requirements of Clauses 19(2) and 19(6) shall also be
satisfied after 4000 hours artificial weathering in accordance with
Appendix?3.
- 30 ­
Notes
Selection of Anti-carbonation Coatings for Application to Old Construction with Sufficient Carbonation Data from a
Detailed Survey
The first step is to estimate the carbonation coefficient of the concrete, by measurement of the carbonation depth
around the structure. This is done by taking the maximum carbonation recorded or a value that more appropriately
represents the carbonation state of the structure (Xo), and substituting into equation (1) to obtain the carbonation
coefficient (D),
Xo²
D=
(1)
2To
where
D
Xo
To
= carbonation coefficient (mm²/year)
= actual carbonation depth (mm)
= age of the structure (year)
The second step is to select the parameters necessary for estimating the required R value of the coatings as follows :
(a)
(b)
Maximum depth of carbonation before reinforcing bar becomes active (XM).
Required design life of the structure (TM).
(1)
According to Engelfried , depth of carbonation for older construction with a coating applied at some point after
construction is given by :
½
X = (Sc² + K) - Sc
(2)
where
Sc
K
TE
= carbonation resistance of the coating, expressed as an equivalent thickness of
concrete
= 2ScXo + Xo² + 2DTE
= elapsed time since application of the coating
Thus, in order to determine the necessary performance of a coating, the appropriate parameters are fed into equation
(2), as follows :
½
XM
= (Sc² + K) - Sc
K
= 2ScXo + Xo² + 2D(TM - To)
(3)
and
By re-arranging equation (3), Sc can be obtained:
Xo² + 2D(TM - To) - XM²
Sc
=
(4)
(2XM - 2Xo)
The R-value for the coating can then be calculated as follows,
R
where
= Sc ηµc
(5)
- 30 Notes
R
µc
= equivalent air layer resistance to carbon dioxide diffusion
= carbon dioxide diffusion resistance for concrete (typically 400)
- 31 ­
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- 32 ­
Notes
Example
A 7-year old concrete structure was found to have a carbonation depth ranging from 15 mm to 23 mm. It was proposed
to select an anti-carbonation protective coating to reduce further carbonation to less than 5 mm in the next 25 years.
Solution
Design for the worst case, choose:
Xo
= 23 mm
= 28 mm
XM
= 7 years
To
= 32 years
TM
Using Equation (1),
Xo²
D
=
2T
o
23²
=
2 η7
2
= 38 mm /year.
Hence, substituting into equation (4),
23² + 2η38η25 - 28²
Sc
=
(2η28 - 2η23)
= 163 mm
Using equation (5), therefore,
R
= 163 η400 mm
= 65200 mm
= 65 m (say)
Hence the Engineer should select a coating which has the property of R 3 65m. Provided that the coating is applied
properly with sufficient film thickness and that degradation of the coating under natural weathering will not reduce the
R value of the coating to below 65 m, then the carbonation front will not advance more than 5 mm in the next 25 years.
If the coating is expected to degrade to R < 65 m within the design life, then recoating will be required. The Engineer
will thus need to consider the need to recoat the structure to ensure a continuous, high performance barrier is present.
REFERENCE :
(1)
Engelfried, R., "Carbonation of Unprotected Concrete and its Control by Means of Coatings", Defazet, V31, n9,
1977, pp 353-359.
- 33 ­
This page is intentionally left blank
- 34 ­
Notes
Clause 20
Situations occur where concrete is saturated on one face, but is exposed to the air or sea spray on others. Structures
which are subject to these conditions include water towers, swimming pools and subways.
Where this occurs, coatings must not form a barrier to the passage of water vapour through the concrete, otherwise
blistering of the coating may occur. The thickest area of the coating will be at greatest risk from blistering, hence the
maximum thickness is specified for testing in accordance with Appendix 1 of this Model Specification.
Coatings which are suitable for application in these conditions include the higher performance acrylics and
cementitious coatings. Coatings which are unlikely to be suitable include barrier coatings based on epoxy and
polyurethane resins.
Clause 21
Paints which would be expected to comply with Clause 21 are moisture curing or two-component polyurethane based
systems, with the property to penetrate into the concrete surface. These types of paint may not necessarily be
compatible with all the requirements contained in Clauses 19 & 20.
Clause 22
The coatings applied to structures in the splash zone and atmospheric zone should have good resistance to U.V.,
abrasion, and be suitable for application under high humidity/moisture conditions. The aesthetic considerations are
normally of secondary importance.
Suitable coating systems include acrylic and polyurethane. Epoxy and coal tar epoxy may also be used if protected
from sunlight. Coating systems not appropriate for wet applications or not suitable for splash zones are water based
coatings and soft coatings such as bituminous coatings.
Water-repellent systems such as silanes are not suitable for lower grade concrete, as rapid carbonation would occur.
However, for new construction of Grade 45 and above or where carbonation is not a concern, the R-value requirement
may be waived, allowing the use of water-repellent systems. The non-film forming water repellent system should be
specified to comply with Clauses 22(2) and 22(3), at the manufacturer's minimum recommended coverage rate. Also,
the treated concrete should be resistant to water uptake when measured in accordance with Appendix 10 of this Model
Specification, both before and after artificial weathering to 4000 hours in accordance with Appendix 3 of this Model
Specification.
Clause 23
The coatings applied to structures in the tidal zone will be subject to abrasion from various floating objects and
possible contamination by oils and solvents.
Coating systems such as cross-linking high performance epoxy, coal tar epoxy and polyurethane are normally
effective for immersed conditions. Heavily modified cement based coatings may not be suitable for permanent
immersion and are not recommended.
For structural elements subject to flexural cracking under load, the paint system should be specified not to fail under
1000 cycles of flexure when tested in accordance with Appendix 6 of this Model Specification at a temperature of 27 ±
2ηC.
- 35 ­
Back Pressure
Acting on
Coatings
20
(1) The requirements for paints applied to new concrete or to old
concrete shall be in accordance with Clause 19, except as stated in
Clauses?20(2) and 20(3).
(2) The SD of the paint system shall not exceed 4?m equivalent air
layer resistance at the maximum DFT, measured in accordance with
Appendix?1. The maximum DFT shall not be greater than 1.5 times the
target mean DFT.
(3) The water permeability measured in accordance with
Appendix?7, Clause?7.5(2), shall classify the coating system as
resistant at the recommended thickness.
Concrete
Subject to
Graffiti
21
In addition to any requirements covered by Clauses 19 and 20, paints
which are subject to graffiti must have the following properties :
(a)
The paint system shall be resistant to treatment with the
solvents necessary for the removal of solvent-based spray
graffiti.
(b)
The paint system shall be resistant to high pressure
washing used to remove posters and water-based graffiti.
SPECIFIC REQUIREMENTS FOR CHLORIDE
RESISTANCE
Concrete
Subject to
Chloride
Spray and
Carbonation
22
(1) The paint system shall comply with Clause 19 or Clause 28
except as stated in Clauses?22(2) and 22(3).
(2) The paint system shall be resistant to the ingress of salt spray
when measured in accordance with Appendix?4.
(3) The paint system shall be resistant to salt spray in accordance
with Clause 22(2) after 4000 hours artificial weathering to Appendix?3.
Concrete
Subject to
Cyclic
Immersion
in Seawater
23
(1) The paint system shall be formulated for application onto
surface dry but saturated concrete in the tidal range.
(2) The paint system shall cure rapidly between the tidal cycles,
such that it may be immersed in seawater within 3 hours of
application.
(3) The paint system shall be resistant to the diffusion of chloride
ion when tested in accordance with Appendix?5.
(4) The minimum DFT of the paint system, tested in accordance
with Clause 1.3(6) at Appendix 1, shall be the minimum DFT for the
field application; the target mean DFT shall be at least 33% greater
- 36 ­
Notes
Clause 24
Water repellent systems such as silanes are not suitable for lower grade concrete, as rapid carbonation would occur.
However, for new construction of Grade 45 and above or where carbonation is not a concern, the R-value requirement
may be waived, allowing the use of water repellent systems. The non-film forming water repellent system should be
specified to comply with Clauses 22(2) and 22(3), at the manufacturer's minimum recommended coverage rate. Also,
the treated concrete should be resistant to water uptake when measured in accordance with Appendix 10 of this Model
Specification, both before and after artificial weathering to 4000 hours in accordance with Appendix 3 of this Model
Specification.
Clause 26
Coatings will be immersed and subject to a variety of chemicals, including possible acid attack due to sulphur
oxidizing bacteria.
Coating systems such as cross-linking high performance epoxy, coal tar epoxy and polyurethane normally perform
well under exposure to sewage.
Where the concrete structure is expected to crack, perhaps due to shrinkage or flexural movement, the paint system
should be specified to be reinforced with glass-fibre fabric, of density 280-300 g/m² open weave lapped by 25 mm at its
edges. In such circumstances, the minimum DFT of the system would be expected to exceed 1 mm.
- 37 ­
than the minimum DFT.
(5) The paint shall be applied in two coats. The minimum DFT
shall be not less than 150?µm.
(6) The water permeability of the coating, measured in accordance
with Appendix?7, Clause?7.5(1), shall be classified as water resistant at
the recommended thickness.
(7) The adhesion of the coating system, measured in accordance
with Appendix?8, shall be satisfactory.
(8) The impact resistance of the paint system, measured in
accordance with Appendix?11, shall be such that no water penetrates
through the coating after testing.
Concrete
Water
Retaining
Structures
Subject to Salt
Spray
24
(1) The paint system shall comply with Clauses 20 or 28, except as
stated in Clauses?24(2) and 24(3).
(2) The paint system shall be resistant to the ingress of salt spray,
when measured in accordance with Appendix?4.
(3) The paint system shall be resistant to salt spray in accordance
with Clause 24(2) after 4000 hours artificial weathering to Appendix?3.
Concrete
Subject to
Chloride
Backpenetration
from Soil
25
(1) The paint system shall comply with Clause 20 or 28, except as
stated in Clauses?25(2) and 25(3).
(2) The paint system shall be resistant to the ingress of salt spray,
when measured in accordance with Appendix?4.
(3) The paint system shall be resistant to salt spray in accordance
with Clause?25(2) after 4000 hours artificial weathering to Appendix?3.
SPECIFIC REQUIREMENTS FOR CHEMICAL
RESISTANCE
Resistance
to Sewage
26
(1) The paint shall be applied in two coats. The minimum DFT
shall be not less than 150?µm, and the target mean DFT shall be not
less than 200?µm.
(2) The paint system complying with Clause 26(1) shall be tested in
accordance with Appendix?9, using 1% sulphuric acid test solution,
and shall not deteriorate over a 3 month test duration.
(3) The bond strength of the paint system measured in accordance
with Appendix?8, shall be satisfactory.
- 38 ­
Notes
Clause 27
In this environment, coatings may be immersed in strong acids, alkalis and solvents.
Coating systems such as high performance solvent free epoxy and coal tar epoxy with at least 400 µm DFT are likely to
be suitable.
Where the concrete structure is expected to crack, perhaps due to shrinkage or flexural movement, the paint system
should be specified to be reinforced with glass-fibre fabric, of density 280-300 g/m² open weave lapped by 25 mm at its
edges. In such circumstances, the minimum DFT of the system would be expected to exceed 1 mm.
Clause 28
The ability of concrete to crack, opening to widths from hairline to 0.3 mm, places very high stresses on paint films. In
order to bridge cracks successfully the coating must have a substantial thickness, typically with a minimum DFT of at
least 300 µm, and be elastomeric or plastomeric in physical terms.
Elastomeric coatings for concrete are typically polyurethane based, whereas plastomeric are soft acrylic copolymer
formulations, which commonly have high rates of dirt pick-up and may need cosmetic top coats.
Alternative approaches are either to reinforce over the crack with glass-fibre fabric, or to chase out the crack, fill the
chase with sealant and then apply a conventional paint.
It is unlikely that crack-bridging paint systems will perform adequately when applied over existing brittle paint finishes.
- 39 ­
(4) Water permeability of the paint system, measured in accordance
with Appendix?7, Clause?7.5(2), shall be classified as resistant at the
recommended thickness.
Resistance
to Highly
Aggressive
Chemicals
27
(1) The paint system shall be applied in at least two coats. The
minimum DFT shall be not less than 275?µm and the target mean DFT
shall be not less than 400?µm,
(2) The paint system complying with Clause 27(1) shall be tested in
accordance with Appendix?9. The coating shall not deteriorate over a
3 month test duration.
(3) The bond strength of the paint system measured in accordance
with Appendix?8, shall be satisfactory.
(4) The water permeability of the paint system, measured in
accordance with Appendix?7, Clause?7.5(2), shall be classified as
resistant at the recommended thickness.
SPECIFIC REQUIREMENTS FOR
ACTIVE/DYNAMIC CRACK BRIDGING
RESISTANCE
Concrete
Subject to
Active Cracks
28
In addition to the requirements of Clauses 19 and 20, paints for
application onto concrete with active cracks shall comply with the
following :
(a)
The paint system shall not fail under 1000 cycles of
flexure, when tested in accordance with Appendix?6 at
temperatures of 5 ¡ C and 27 ¡ C at the minimum
DFT.
(b)
The paint system shall not fail in accordance with
Clause?28(a) after being subjected to artificial weathering
for 4000 hours to Appendix?3 at the minimum DFT.
SPECIFIC REQUIREMENTS FOR TIDAL WORK
Concrete
Subject to
Cyclic
Immersion
in Seawater
29
(1) The paint system shall be formulated for application onto
surface dry but saturated concrete in the tidal range.
(2) The paint system shall cure rapidly between the tidal cycles,
such that it may be immersed in seawater within 3 hours of
application.
(3) The paint system shall be resistant to the diffusion of chloride
ion when tested in accordance with Appendix?5.
- 40 ­
Notes
Clause 30
This Clause relates to applications on concrete in the splash or tidal zone that remains saturated beneath the concrete
surface.
- 41 ­
(4) The target mean DFT shall be at least 33% greater than the
minimum DFT.
(5) The paint shall be applied in two coats. The minimum DFT
shall be not less than 150?µm.
(6) The water permeability of the coating, measured in accordance
with Appendix?7, Clause?7.5(1), shall be classified as water resistant at
the recommended thickness.
(7) The adhesion of the coating system, measured in accordance
with Appendix?8, shall be satisfactory.
(8) The impact resistance of the paint system, measured in
accordance with Appendix?11, shall be such that no water penetrates
through the coating after testing.
Wet Concrete
Surfaces
30
(1) Paint for application in the tidal and splash zone shall comply
with Clauses 29(1) to 29(8).
(2) All concrete surfaces to receive paint shall be free from surface
water at the time of application.
(3) For working above water, temporary anti-splash protection shall
be provided to reduce the effect of wave action in re-wetting concrete
surfaces.
(4) Painting works shall be programmed to meet the manufacturer’s
minimum time limit before the paint can be immersed in water.
(5) The paint shall be applied in accordance with Clauses?16(4) and
16(5).
- 42 ­
Notes
Listed below are short lists of some types of coating system studied by Consultancy Agreement No. 47/88
SHORTLIST OF ANTI-CARBONATION COATINGS
Recommended
DFT (microns)
Coating system
Supplier
Generic Type
Granoimpact Roma
Cali-Empire Ltd
Acrylic
440
Granogloss
Cali-Empire Ltd
Acrylic
200
SBD Stonepaint
Dodwell Industrial
Acrylic
250
SBD Weatherproof
Dodwell Industrial
Acrylic
250
Decadex
Expandite-Interswiss
Acrylic
350
Dekguard/Topcoat W
Foseco Industries
Silox/Acrylic
300
Dekguard/Topcoat S
Foseco Industries
Silox/MMA
140
Thorolastic
ICI-Thoro
Acrylic
325
Emer-Clad
New Asia Eng’g
Acrylic
350
Icosit Cosmetic
Sika Ltd
MMA
120
Elastofil
Sika Ltd
Acrylic
900
SHORTLIST OF COATINGS TO RESIST SEAWATER SPRAY
Recommended
DFT (microns)
Coating system
Supplier
Generic Type
Hdrozo Clear 16
Ameron Ltd
Silane
N/A
Berger C.R. Finish
Berger Paints Ltd
Chlor.Rubber
200
Granoimpact Rolana
Cali-Empire Ltd
Acrylic
210
SBD Aquapel WR
Dodwell Industrial
Silane
N/A
Hardac Acrylic Sealer
Dodwell Industrial
Acrylic
N/A
FCR 851
Expandite-Interswiss
Cement
2000
Nitocote EP 430
Foseco Industries
Epoxy
400
EP 41
Loyal Enterprise
Epoxy
200
Dekguard/Topcoat S
Foseco Industries
Silox/MMA
140
Interguard EF/Interthane PQ
International Paint
Epoxy-P/U
150
Icosit Cosmetic
Sika Ltd
MMA
120
Nitocote ET 550
Foseco Industries
Tar Epoxy
350
Nafulan I Dick
Univic Engineering
Tar Epoxy
500
Eptar 56
Loyal Enterprise
Tar Epoxy
225
Only where protected from sunlight
- 43 ­
Notes
SHORTLIST OF COATINGS TO RESIST SEAWATER IMMERSION
Recommended
DFT (microns)
Coating system
Supplier
Generic Type
Luxatar 6
Berger Paints
Tar Epoxy
800
Nitocote EP 403
Foseco Industries
Epoxy
400
Nitocote ET 401
Foseco Industries
Tar Epoxy
500
Nitocote EP 430
Foseco Industries
Epoxy
400
Nitocote ET 550
Foseco Industries
Tar Epoxy
350
Dulux Epoxy Bildcote AR580
ICI Ltd
Epoxy
300
Intergard EF/Intertuf JJA 180
International Paint
Epoxy-P/U
300
Concresive 1447/1448, Hydrocote
Inter Pacific Ltd
Epoxy
500
Eptar 56
Loyal Enterprise Ltd
Tar Epoxy
225
EP 41
Loyal Enterprise Ltd
Epoxy
200
Emer-Tar Epoxy
New Asia Engineering
Tar Epoxy
200
Irathane
Pyrok Industries
Polyurethane
225
Coluriet TCN 300
Sigma Coatings
Tar Epoxy
300
Poxitar F
Sika Ltd
Tar Epoxy
150
Probond 811C/EC-400
Spray Engineering
Epoxy
500
Rust-Oleum 9578
Topman International
Tar Epoxy
200
Escoweld 7502 E
Univic Engineering Ltd
Epoxy
500
MC-DUR 1500 ToF
Univic Engineering Ltd
Tar Epoxy
500
Foseco Industries
Epoxy
400
Suitable for Contact with Potable Water
Nitocote EP 405
SHORTLIST OF CRACK-BRIDGING ANTI-CARBONATION COATINGS
Recommended
DFT (microns)
Coating system
Supplier
Generic Type
SBD Weatherproof EC
Dodwell Industrial
Acrylic
800
Decadex
Expandite-Interswiss
Acrylic
350
Dekguard Elastic
Foseco Industries
Acrylic
400
Thorolastic
ICI-Thoro
Acrylic
325
Emer-Clad Reinforced
New Asia Eng’g
Acrylic
750
Irathane
Pyrok Industries
Polyurethane
225
Barracryl
Sanxoz Master Builders
Acrylic
300
Icosit Elastic
Sika Ltd
Ethylene
300
Elastofil
Sika Ltd
Acrylic
900
- 44 ­
Notes
SHORTLIST OF COATINGS TO RESIST SEWAGE
Recommended
Coating system
Supplier
Generic Type
DFT (microns)
Amercoat 78 HB
Epoxy Plus Coating
Epilux 4
Nitocote EP 403
Nitocote ET 401
Nitocote EP 430
Nitocote ET 550
Dulux AR 431-7790/7791
Concresive 1170
Eptar 56
Emer-Tar Epoxy
Irathane
Colturiet TCN 300
Poxitar F
Poxitar
Probond 711C/EC-400
Rust-Oleum 9578
Escoweld 7502 E
MC-DUR 1500 ToF
Ameron Ltd
Dodwell Industrial
Berger Paints
Foseco Industries
Foseco Industries
Foseco Industries
Foseco Industries
ICI Ltd
Inter Pacific Ltd
Loyal Enterprise Ltd
New Asia Engineering
Pyrok Industries
Sigma Coatings
Sika Ltd
Sika Ltd
Spray Engineering
Topman International
Univic Engineering Ltd
Univic Engineering Ltd
Tar Epoxy
Epoxy
Tar Epoxy
Epoxy
Tar Epoxy
Epoxy
Tar Epoxy
Tar Epoxy
Epoxy
Tar Epoxy
Tar Epoxy
Polyurethane
Tar Epoxy
Tar Epoxy
Tar Epoxy
Epoxy
Tar Epoxy
Epoxy
Tar Epoxy
400
500
215
400
500
400
350
200
200
225
200
225
300
285
285
500
200
500
500
Foseco Industries
Epoxy
400
Suitable for Contact With Potable Water
Nitocote EP 405
SHORTLIST OF COATINGS TO RESIST CHEMICALS
Recommended
Coating system
Supplier
Generic Type
Nitocote EP 403
Nitocote ET 401
Nitocote EP 430
Resicote F7/Resilay HB
Probond EC-400
Escoweld 7502 E
MC-DUR 1500 ToF
Foseco Industries
Foseco Industries
Foseco Industries
Sui Tai Ltd
Spray Engineering
Univic Engineering
Univic Engineering
Epoxy
Tar Epoxy
Epoxy
Epoxy
Epoxy
Epoxy
Tar Epoxy
400
500
400
500
500
500
500
Foseco Industries
Epoxy
400
DFT (microns)
Suitable for Contact With Potable Water
Nitocote EP 405
SHORTLIST OF CRACK-BRIDGING COATINGS TO RESIST SEA SPRAY
Recommended
Coating system
Supplier
Generic Type
SBD Weatherproof EC/Aquapel WR
Irathane
Dodwell Industrial
Pyroc Industries
Siloxane/Acryli
c
Polyurethane
DFT (microns)
800
225
è 45 è
APPENDIX 1
DETERMINATION OF THE WATER VAPOUR
DIFFUSION RESISTANCE OF COATINGS
Scope
1.1 This method covers the determination of the water vapour diffusion
resistance of coatings for concrete by measuring the water vapour
transmission through a coated composite.
Test
Substrate
1.2
Procedure :
Preparation
of
Specimens
1.3 (1) The tiles and all materials shall be conditioned for 24 hours at
the application conditions of 27 ¡ ⎝C and 80 ¡ 5 %rel ati ve hu m
i dit y
Unglazed ceramic tiles of 100 x 100 x 5 mm size shall be used as the
substrate. The tiles shall be of uniform quality and from a single batch,
free from contamination.
(2) The coating system shall be applied in accordance with the
manufacturer’s instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
(3)
Application shall be by spray, brush or roller.
(4) 10 tiles shall be prepared in one operation for all tests to be
carried out.
(5) After coating, the specimens shall be conditioned at 27 ¡ ⎝C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(6) Following conditioning, 2 tiles shall be sawn in half and the
maximum, minimum and mean DFT measured using a travelling
microscope; the mean value shall be taken from at least 30
observations.
(7) 2 tiles shall be labelled and stored in a light-fast box to serve as
colour control panels for artificial or natural weathering tests.
Procedure :
Determination
of Water
Vapour
Transmission
Rate
1.4
(1) The sample shall be set in a metal cell using silicone rubber,
such that the uncoated face shall be sealed above a reservoir of distilled
water.
(2) The unit shall be placed in a desiccator at 27 ¡ ⎝C and 0%
relative humidity. The change in weight of the unit with time shall be
measured periodically.
(3) The measurement shall be continued until a steady-state weight
loss has been recorded for a continuous 3 day period.
è 46 è
Calculation
1.5
(1) The water vapour transmission rate for the coated tile shall be
calculated in accordance with the equation :
dG
(g/m2 per 24 hr)
WVT =
T.A
where :
WVT is the water vapour transmission rate (g/m2per 24 hr),
dG is the weight change under steady-state conditions (g),
A is the test area (m2), and
T is the time during which dG occurred (24 hr units)
(2) The water vapour diffusion coefficient shall be calculated for the
composite, from which the diffusion coefficient for a measured mean
thickness of coating shall be obtained. The water vapour diffusion
coefficient for the composite shall be calculated from the equation :
WVT . tT
dT
H2O
=
(cm2/s)
Pw
where :
dT
H2O
is the water vapour diffusion coefficient (cm2/s),
WVT is the water vapour transmission rate (g/m2per 24 hr),
tT is the thickness of the composite (cm), and
Pw is the density of saturated water vapour at the test
temperature (g/cm3)
(3)
The performance of the composite is then given by :
tT
tt
=
dT
H2O
tc
+
dt
H2O
dc
H2O
where :
tT is the thickness of the composite (cm),
tt is the thickness of the tile (cm),
tc is the thickness of the coating (cm),
dT
H2O
is the water vapour diffusion coefficient for the
composite (cm2/s),
ˆ 47 ˆ
dt
H2O
is the water vapour diffusion coefficient for the tile
(cm2/s), and
dc
H2O
is the water vapour diffusion coefficient for the coating
(cm2/s)
(4) The equivalent air layer resistance of the coating to the diffusion
of water vapour shall be calculated from the equation :
da
H2O
SD =
tc (m)
dc
H2O
where :
SD is the equivalent air layer resistance (m),
da
H2O
is the diffusion coefficient for water vapour in air, which
is equal to 0.242 cm2/s)
tc is the thickness of the coating (m), and
dc
H2O
is the water vapour diffusion coefficient for the coating
cm2/s
(5) The water vapour diffusion resistance of the coating shall be
calculated as the mean of two determinations.
Reporting of
Results
1.6
The following shall be reported :
(a)
The name of the coating system and the batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The results for water vapour diffusion resistance value SD
at the mean DFT.
(g)
Whether the samples have been subjected to artificial
weathering and the duration.
- 48 ­
Figure 1.1 - Set-up for Water Vapour Diffusion Test
- 49 ­
APPENDIX 2
DETERMINATION OF THE CARBON DIOXIDE
DIFFUSION RESISTANCE OF COATINGS
Scope
2.1 This method covers the determination of the carbon dioxide diffusion
resistance of coatings for concrete by measuring the flow rate of a
mixture of oxygen and carbon dioxide gas through a coated composite.
Test
substrate
2.2 Unglazed ceramic tiles of 100?mm x 100?mm x 5?mm size shall be
used as the substrate. The tiles shall be of uniform quality and
preferably from a single batch, free from contamination.
Equipment
2.3 The following equipment is required, as shown in Figure 2.1.
Procedure :
preparation
of
specimens
(a)
A test chamber to receive 5?mm thick unglazed ceramic
tiles with coating systems applied.
(b)
Supplies of analytical grade 85/15 oxygen and carbon
dioxide gas blend and helium gas.
(c)
Pressure balance equipment.
(d)
A gas chromatograph and integrator.
2.4 (1) The tiles and all materials shall be conditioned for 24 hours at
the application conditions of 27 ¡ ♦C and 80 ¡ 5 %rel ati ve hu m
i dit y
(2) The coating system shall be applied in accordance with the
manufacturer’s instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
(3)
Application shall be by spray, brush or roller.
(4) 10 tiles shall be prepared in one operation for all tests to be
carried out.
(5) After coating, the specimens shall be conditioned at 27 ¡ ♦C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(6) Following conditioning, 2 tiles shall be sawn in half and the
maximum, minimum and mean DFT measured using a travelling
microscope; the mean value shall be taken from at least 30
observations.
- 50 ­
(7) 2 tiles shall be labelled and stored in a light-fast box to serve as
colour control panels for artificial or natural weathering tests.
Procedure :
determination
of gas flow
rate
2.5
(1) After conditioning, the coated sample shall be carefully placed
in the test chamber.
(2) The gas cylinders shall be turned on and the gas flow rates
monitored to obtain the same flow rate and pressure on both sides of
the coated tile.
(3)
The system shall be allowed to equilibrate for at least 24 hours.
(4) The carbon dioxide and oxygen diffusion rate through the coated
tile composite shall then be measured by gas chromatography.
Calculation
2.6
(1) The flux rate for carbon dioxide shall be calculated as the carbon
dioxide diffusion coefficient for the composite using Ficks first law of
diffusion :
QxL
d=
(cm2/s)
AxC
where :
d is the carbon dioxide diffusion coefficient (cm2/s),
Q is the flow rate (mol/s),
L is the thickness of the composite (cm),
A is the test area (cm2), and
C is the concentration drop (mol/cm3).
(2)
The performance of the composite is then given by :
tt
tT
=
dT
CO2
tc
+
dt
CO2
dc
CO2
where :
tT is the thickness of the composite (cm),
tt is the thickness of the tile (cm),
tc is the thickness of the coating (cm),
dT
CO2
is the carbon dioxide diffusion coefficient for the
composite (cm2/s),
- 51 ­
dt
CO2
is the carbon dioxide diffusion coefficient for the tile
(cm2/s), and
dc
CO2
is the carbon dioxide diffusion coefficient for the coating
(cm2/s)
(3) The relative carbon dioxide diffusion coefficient for the coating
shall be expressed as a dimensionless ratio, as follows :
da
CO2
µ =
dc
CO2
where :
µ is the relative carbon dioxide diffusion coefficient of the
coating,
da
CO2
is the coefficient for carbon dioxide diffused through air,
which is equal to 0.160 cm2/s, and
dc
CO2
is the coefficient for carbon dioxide diffused through the
coating (cm2/s).
(4) The resistance of the coating, expressed as an equivalent air
layer thickness, or "R-value", shall be calculated as follows :
R = µ . t (m)
where :
R is the equivalent air layer thickness (R-value) (m),
µ is the relative carbon dioxide diffusion coefficient of the
coating, and
t is the mean DFT of the coating under test (m)
(5) Alternatively, the resistance of the coating may be expressed as
an equivalent thickness of concrete cover, or "Sc-value", which shall be
calculated as follows :
R
Sc = (m)
µc
- 52 ­
where :
Sc is the equivalent thickness of concrete cover,
R is the equivalent air layer thickness, and
µc is the diffusion resistance factor for concrete, typically 400.
(6) The carbon dioxide diffusion resistance parameters for the
coating shall be calculated as the mean of two determinations.
Reporting of
results
2.7
The following shall be reported :
(a)
The name of the coating system and the batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The results for carbon dioxide diffusion resistance in
terms of µ, R and Sc, at the mean DFT.
(g)
Whether the samples have been subjected to artificial
weathering and the duration.
- 53 ­
Figure 2.1 - Set-up for Gas Flux Measurement
- 54 ­
- 55 ­
APPENDIX 3
DETERMINATION OF THE
RESISTANCE OF COATINGS
WEATHERING
Scope
3.1 This method covers the determination of the weathering resistance of
coatings for concrete, applied to various substrates, using a QUV
artificial weathering cabinet.
Test
substrate
3.2
Equipment
Method
The substrate shall be one of the following :
(a)
Coated unglazed ceramic tiles of 100 x 100 x 5?mm size.
(b)
Coated 100 mm core samples.
(c)
Coated mortar prisms of 40?x 40 x 160?mm dimension.
3.3 The following equipment is required :
(a)
QUV artificial weathering cabinet fitted with UV-A
fluorescent tubes.
(b)
Frames to hold concrete core and mortar prism specimens
in the specimen tray.
3.4 (1) Coated specimens shall be located in the specimen tray of the
QUV weatherometer.
(2) The specimens shall be tested in accordance with the following
weathering cycle :
6 hours UV-A light at 60 +
_ 2∪C
6 hours condensation at 50 +
_ 2∪C
for 4000 hours.
(3) On completion of the weathering cycle, a visual inspection shall
be made to assess the physical defects of the coating system in
accordance with the standard methods outlined in :
- ASTM?D?659-86 for chalking,
- ASTM?D?660-87 for checking,
- ASTM?D?661-86 for cracking,
- ASTM?D?714-87 for blistering,
- ASTM?D?772-86 for flaking, and
- ASTM?D?2616-67(1979) for colour change.
- 56 ­
(4) The specimens shall be conditioned at 27 +
_ 2∪C and 80 +
_ 5%
relative humidity for 2 weeks prior to further testing.
Reporting of
results
3.5
The following shall be reported :
(a)
The name of the coating system and the batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
Visual defects recorded using standard techniques.
- 57 ­
APPENDIX 4
DETERMINATION OF THE
RESISTANCE OF COATINGS
SALT
SPRAY
Scope
4.1 This method covers the determination of the salt spray resistance of
coatings for concrete by using a salt spray cabinet.
Materials
4.2 The following materials are required.
Procedure :
preparation
of
specimens
4.3
(a)
Ordinary Portland cement complying with BS?12:1989.
(b)
Oven-dry natural sand with rounded particle shape and
Zone M grading complying with BS?882:1983, Table?5.
(c)
20?mm graded coarse
BS?882:1983, Table?4.
(d)
Petroleum jelly, mineral oil or a proprietary mould
releasing agent.
(e)
Epoxy resin (Araldite concrete primer CM xh 125 AB) or
equivalent.
(f)
Artificial seawater, made up with 30 ¡ 5?g/ L s odi u
chloride salt in distilled water, complying with the
preparation method outlined in BS?3900:1985, Part?F12.
aggregate
complying
with
(1) Concrete of Grade 20/20 shall be used to prepare the specimens.
The approximate mix proportions shall be in accordance with Table
4.1 and trial mixes shall be used to finalize the concrete mix.
Table 4.1 Mix proportions for concrete specimens
Ordinary Portland Cement (BS?12)
Zone M Sand (BS?882)
20 mm Graded Aggregate (BS?882)
Water (free)
Slump
28 day cube strength (Target Mean)
250 kg/m3
625 kg/m3
1250 kg/m3
190 L/m3
75 mm
25 MPa
(2) Concrete panels of 500?mm?x 500?mm x 50?mm shall be
fabricated using fair-faced ply moulds.
- 58 ­
(3) All materials and moulds shall be conditioned at 27 ¡ ∪C for 24
hours before casting.
(4) After mixing, the concrete shall be placed and compacted within
30 minutes into cleaned, lightly oiled moulds. The concrete shall be
finished by trowelling with a wood float, and then covered with
polythene sheeting for 24 hours.
(5) After 24 hours, the mould shall be stripped and the panels shall
be wrapped in polythene sheeting and stored at 27 ¡ ∪C for at least 28
days, until ready for coating application.
(6) The test face shall be the moulded 500?mm x 500?mm side of
the panel.
(7) The test face shall be prepared in accordance with the
manufacturer’s instructions by either wire brushing, grit blasting or
high pressure water blasting, followed by filling of blow hole defects
as required. In the absence of instructions from the manufacturer, a
mix comprising 1:2.5 OPC/Zone F sand complying with BS?882:1983
and 2:1 water/SBR solution shall be used for filling blow holes and
defects, and shall be applied to a damp concrete surface. The filled
surface shall be covered with polythene sheeting and left for 24 hours
at 27 ¡ ∪C prior to coating.
(8) The coating shall be applied in accordance with the
manufacturer’s instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
(9)
Application shall be by spray, brush or roller.
(10) 10 panels shall be prepared in one operation for all tests to be
carried out.
(11) After coating, the specimens shall be conditioned at 27 ¡ ∪C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(12) Following conditioning, ten 100?mm diameter and 50?mm thick
core samples shall be taken from the panels.
(13) 2 coated core samples shall be cut in half and the maximum,
minimum and mean DFT measured using a travelling microscope; the
mean value shall be taken from at least 30 observations.
(14) The concrete surfaces of the core shall be encased on all sides
with a 5?mm layer of epoxy resin, except for the coated face.
(15) After the epoxy resin has hardened and fully cured, the
specimens shall be placed in a salt spray cabinet ready for testing.
- 59 ­
Procedure :
determination
of salt spray
resistance
4.4
(1) The specimen shall be mounted in the salt spray cabinet and
shall be tested in accordance with the following weathering cycle :
4 hours salt water spray at 40∪C,
8 hours drying at 40∪C and 30% relative humidity
for 1000 hours.
(2) On completion of the weathering cycle, the coated surface shall
be washed with distilled water.
(3) The depth of penetration of chloride through the coating shall be
determined in depth increment ranges of 0 to 5?mm, 5?mm to 10?mm,
and 10?mm to 15?mm beneath the coating, using the central 50?mm of
the specimen, by grinding and analyzing the concrete dust in
accordance with CS 1, Vol. 2, Clause 21.10.2.
(4) The chloride content result for the coating shall be calculated as
the mean of two determinations.
Reporting of
results
4.5
The following shall be reported :
(a)
The name of the coating system and the batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The results of the chloride content determination, given
by weight of sample for each depth increment tested for
both coated and uncoated concrete.
(g)
The results for the salt spray resistance of the coating,
expressing the coating as resistant at the mean DFT, if the
chloride content in the 5-10?mm increment range and
deeper is ∪0.04%, or not resistant at the mean DFT, if the
chloride content is >0.04%, both before and after
weathering.
(h)
Whether the samples have been subjected to artificial
weathering and the duration.
- 60 ­
- 61 ­
APPENDIX 5
DETERMINATION OF THE SALT WATER
IMMERSION RESISTANCE OF COATINGS
Scope
5.1 This method covers the determination of the salt water immersion
resistance of coatings for concrete by immersing in artificial seawater.
Materials
5.2 The following materials are required.
Procedure :
preparation of
specimens
5.3
(a)
Ordinary Portland cement complying with BS?12:1989.
(b)
Oven-dry natural sand with rounded particle shape and
Zone M grading complying with BS?882:1983, Table?5.
(c)
20?mm graded coarse
BS?882:1983, Table?4.
(d)
Petroleum jelly, mineral oil or a proprietary mould
releasing agent.
(e)
Epoxy resin (Araldite concrete primer CM xh 125 AB) or
equivalent.
(f)
Artificial seawater made up with 30 ¡ 5g/litr sodium
chloride salt in distilled water, complying with the
preparation method outlined in BS?3900:1985, Part?F12.
aggregate
complying
with
(1) Concrete of Grade 20/20 shall be used to prepare the specimens.
The approximate mix proportions shall be in accordance with Table
1.5.1 and trial mixes shall be used to finalize the concrete mix.
Table 1.5.1 Mix proportions for concrete specimens
Ordinary Portland Cement (BS?12)
Zone M Sand (BS?882)
20 mm Graded Aggregate (BS?882)
Water (free)
Slump
28 day cube strength (Target Mean)
250 kg/m3
625 kg/m3
1250 kg/m3
190 L/m3
75 mm
25 MPa
(2) Concrete panels of 500?mm x 500?mm x 50?mm shall be
fabricated using fair-faced ply moulds.
(3)All materials and moulds shall be conditioned at 27 ¡
hours before casting.
∪C for 24
- 62 ­
(4) After mixing, the concrete shall be placed and compacted within
30 minutes into cleaned, lightly oiled moulds. The concrete shall be
finished by trowelling with a wood float, and then covered with
polythene sheeting for 24 hours.
(5) After 24 hours, the mould shall be stripped and the panels shall
be wrapped in polythene sheeting and stored at 27 ¡ ∪C for at least 28
days, until ready for coating application.
(6) The test face shall be the moulded 500?mm x 500?mm side of
the panel.
(7) The test face shall be prepared in accordance with the
manufacturer’s instructions by either wire brushing, grit blasting or
high pressure water blasting, followed by filling of blow hole defects
as required. In the absence of instructions from the manufacturer, a
mix comprising 1:2.5 OPC/Zone F sand complying with BS?882:1983
and 2:1 water/SBR solution shall be used for filling blow holes and
defects, and shall be applied to a damp concrete surface. The filled
surface shall be covered with polythene sheeting and left for 24 hours
at 27 ¡ ∪C prior to coating.
(8) The coating shall be applied in accordance with the
manufacturers instructions, using all necessary primers and undercoats,
and coverage rates shall be checked by weighing.
(9)
Application shall be by spray, brush or roller.
(10) 10 panels shall be prepared in one operation for all tests to be
carried out.
(11) After coating, the specimens shall be conditioned at 27 ¡ ∪C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(12) Following conditioning, ten 100?mm diameter and 50?mm thick
core samples shall be taken from the panels.
(13) 2 coated core samples shall be cut in half and the maximum,
minimum and mean DFT measured using a travelling microscope; the
mean value shall be taken from at least 30 observations.
(14) The concrete surfaces of the core shall be encased on all sides
with a 5?mm layer of epoxy resin, except for the coated face.
(15) After the epoxy resin has hardened and fully cured, the
specimens shall be placed in a container above a tank of artificial
seawater, ready for testing.
- 63 ­
Procedure :
determination
of salt water
immersion
resistance
5.4
(1) The specimens shall be immersed in artificial seawater and shall
be tested in accordance with the following weathering cycle?:
6 hours immersion in artificial seawater at 1 metre depth at 27 i
2∪C,
6 hours drying at 40∪C and 30% relative humidity
for 1000 hours.
(2) On completion of the weathering cycle, the coated surface shall
be washed with distilled water.
(3) The depth of penetration of chloride through the coating shall be
determined in depth increment ranges of 0 to 5?mm, 5?mm to 10?mm,
and 10?mm to 15?mm beneath the coating, using the central 50?mm of
the specimen only, by grinding and analyzing the concrete dust in
accordance with CS 1, Vol. 2, Clause 21.10.2.
(4) The chloride content result for the coating shall be calculated as
the mean of two determinations.
Reporting of
results
5.5
The following shall be reported :
(a)
The name of the coating system and the batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The results of the chloride content determination, given
by weight of sample for each depth increment tested for
both coated and uncoated concrete.
(g)
The results for the salt water immersion resistance of the
coating, expressing the coating as resistant at the mean
DFT, if the chloride content in the 5-10?mm increment
range and deeper is ∪0.04%, or not resistant at the mean
DFT, if the chloride content is >0.04%, both before and
after weathering.
(h)
Whether the samples have been subjected to artificial
weathering and the duration.
- 64 ­
- 65 ­
APPENDIX 6
DETERMINATION OF THE DYNAMIC CRACK
BRIDGING RESISTANCE OF COATINGS
Scope
6.1 This method covers the determination of the dynamic crack bridging
resistance of coatings for concrete based on German BAM
ZVT-BEL-OS recommendations.
Materials
6.2 The following materials are required.
Equipment
Procedure :
preparation
of
specimens
(a)
Ordinary Portland cement complying with BS?12:1989.
(b)
Oven-dry natural sand with rounded particle shape and
Zone M grading complying with BS?882:1983, Table?5.
(c)
Petroleum jelly, mineral oil or a proprietary mould
releasing agent.
(d)
8?mm single wire prestressing strand, cut to a length of
320?mm.
(e)
PVC sleeve or rubber tubing of 2?mm wall thickness and
8?mm internal diameter, cut to 100?mm length.
6.3 The following equipment is required.
6.4
(a)
A pneumatic, lever action crack bridging resistance tester
to BAM ZVT-BEL-OS.
(b)
A test cabinet with temperature control to 27 ¡ ∪C, 5 M
2∪C and relative humidity control to 80 ¡ 5 %and 70
5%.
(c)
Steel prism moulds of 40?mm x 40?mm x 160?mm with
PVC inserts and slots for prestressing strand as shown in
Figure 6.1.
(1) Sand-cement mortar shall be used to prepare the specimens in
the proportions stated in Table 6.1; trial mixes shall be used to finalize
the mortar mix.
(2) The PVC sleeve shall be fitted onto the central region of the
prestressing strand.
- 66 ­
Table 6.1 Mix proportions for mortar specimens
Ordinary Portland Cement (BS?12)
Zone M Sand (BS?882)
Water (free)
28 day cube strength (Target Mean)
250 kg/m3
750 kg/m3
150 L/m3
35 MPa
(3) A 3?mm x 16?mm x 40?mm PVC insert and the prestressing
strand shall be placed into the lightly oiled steel mould in the position
shown in Figure 6.1.
(4) The mixed sand-cement mortar shall be carefully worked into
the mould by tamping with small plastic or steel tamping rod to
eliminate all voids.
(5)
The surface shall be struck off and finished with a wood float.
(6) All the specimens shall be cured under polythene sheeting at 27
¡ Ó∪C.
(7) After 3 days curing, the mould shall be stripped and the prism
shall be wrapped in polythene sheeting and stored at 27 ¡ Ó∪C for 28
days.
(8) The floated surface of the prism shall be the test surface to
receive the coating, as shown in Figure 6.2.
(9) The coating shall be applied in accordance with the
manufacturer's instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
(10) Application shall be by spray, brush or roller.
(11) 10 prisms shall be prepared in one operation for all tests to be
carried out, including spares.
(12) After coating, the prism specimens shall be conditioned at 27 b
2∪C and 80 ¡ Ó 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l os
of solvents and other volatile materials.
Procedure :
determination
of crackbridging
resistance
6.5
(1) The coated test specimen shall be fixed into the testing
equipment.
(2) The specimen shall be set to produce an initial crack width of
0.05?mm (Wu) with a manual or electronic movement gauges fixed to
the side of the specimen over the crack.
(3) The maximum crack width for the test shall be set to 0.3?mm
(Wo).
- 67 ­
(4) The frequency of the test for the opening of the crack shall be set
to 1?Hz.
(5) The equipment and the coated test specimen shall be maintained
in the test cabinet at 27 ¡ ∪C and 80 ¡ 5 %rel ati ve hu m
i dit y
(6) The test shall be started by cycling the test specimen with the
crack opening between Wu and Wo in a sine wave form for 1000
cycles.
(7) After 1000 cycles, the coated surface shall be examined with a
magnifying glass to check for cracks.
(8) The test shall be repeated with a new specimen of the same
coating system but shall be tested in the test cabinet at 5 ¡ ∪C and 70
¡ Ó5 %rel ati ve hu m
i dit y
(9) On completion of testing, the specimen shall be cut in half and
the DFT measured using a travelling microscope; the mean value shall
be taken from at least 15 observations.
(10) Two test specimens shall be used to determine the
crack-bridging capacity of the coating system at each temperature.
Neither specimen shall fail after 1000 cycles. The coating shall be
classified as suitable for use over dynamic cracks provided that the
film has not failed at the end of the test.
Reporting of
results
6.6
The following shall be reported :
(a)
The name of the coating system and the batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The results for crack-bridging resistance and the
temperature at which testing was undertaken.
(h)
Whether the samples have been subjected to artificial
weathering and the duration.
- 68 ­
Figure 6.1 - Mould for Crack-bridging Test Specimen
- 69 ­
Figure 6.2 - Section through Crack-Bridging Test Specimen
- 70 ­
- 71 ­
APPENDIX 7
DETERMINATION OF THE WATER
PERMEABILITY RESISTANCE OF COATINGS
Scope
7.1 This method covers the determination of the water permeability
resistance of coatings for concrete by laboratory based and portable
in-situ permeability cells.
Materials
7.2 The following materials are required.
Equipment
7.3
(a)
Ordinary Portland cement complying with BS?12:1989.
(b)
Oven-dry natural sand with rounded particle shape and
Zone M grading complying with BS?882:1983, Table?5.
(c)
20?mm graded coarse
BS?882:1983, Table?4.
(d)
Petroleum jelly, mineral oil or a proprietary mould
releasing agent.
(e)
Epoxy resin (Araldite concrete primer CM xh 125 AB) or
equivalent.
aggregate
complying
with
(1) The laboratory based permeability cell may be of various
designs, and shall comprise the following :
(a)
A stainless steel top ring.
(b)
A stainless steel bottom plate with a hole drilled to form
the water inlet.
(c)
A perspex window to fit into the centre of the top ring.
(d)
A tapered brass sleeve, being widest at the upstream end,
with O-ring seals at each end.
(e)
A tapered brass sleeve with the same dimension as that in
Clause?7.3(d), except without O-ring seals.
(f)
A stainless steel bar as a clamp for the perspex window.
(g)
Stainless steel bolts to hold the top ring and bottom plate
together.
(h)
Stainless steel connecting tubing.
- 72 ­
(i)
Equipment to produce pressurized water (see Clause 7.5
(1)(b).
(2) The portable permeability cell shall be the CLAM in-situ
permeability tester developed by Queen’s University, Belfast.
Procedure :
preparation
of
specimens
7.4
(1) Concrete of Grade 20/20 shall be used to prepare the specimens
and the approximate proportions shall be in accordance with Table?7.1;
trial mixes shall be used to finalize the concrete mix.
Table 7.1 Mix proportions for concrete specimens
Ordinary Portland Cement (BS?12)
Zone M Sand (BS?882)
20 mm Graded Aggregate (BS?882)
Water (free)
Slump
28 day cube strength (Target Mean)
250 kg/m3
625 kg/m3
1250 kg/m3
190 L/m3
75 mm
25 MPa
(2) Concrete panels of 500?mm x 500?mm x 50?mm shall be
fabricated using fair-faced ply moulds.
(3) All materials and moulds shall be conditioned at 27 ¡ ⎝C for 24
hours before casting.
(4) After mixing, the concrete shall be placed and compacted within
30 minutes into cleaned, lightly oiled moulds. The concrete shall be
finished by trowelling with a wood float, and then covered with
polythene sheeting for 24 hours.
(5) After 24 hours, the mould shall be stripped and the panels
wrapped in polythene sheeting and stored at 27 ¡ ⎝C for at least 28
days, until ready for coating application.
(6) The test face shall be the moulded 500?mm x 500?mm side of
the panel.
(7) The test face shall be prepared in accordance with the
manufacturer’s instructions by either wire brushing, grit blasting or
high pressure water blasting, followed by filling of blow hole defects
as required. In the absence of instructions from the manufacturer, a
mix comprising 1:2.5 OPC/Zone F sand complying with BS?882:1983
and 2:1 water/SBR solution shall be used for filling blow holes and
defects, and shall be applied to a damp concrete surface. The filled
surface shall be covered with polythene sheeting and left for 24 hours
at 27 ¡ ⎝C prior to coating.
(8) The coating shall be applied in accordance with the
manufacturer’s instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
- 73 ­
(9)
Application shall be by spray, brush or roller.
(10) 10 panels shall be prepared in one operation for all tests to be
carried out, including spares.
(11) After coating, the specimens shall be conditioned at 27 ¡ ⎝C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(12) Following conditioning, ten 100?mm diameter by 50?mm thick
core samples shall be taken from the panels.
(13) 2 coated core samples shall be cut in half and the maximum,
minimum and mean DFT measured using a travelling microscope; the
mean value shall be taken from at least 30 observations.
(14) The top coated surface and the bottom concrete surface of the
core shall be masked with drafting tape and the specimen placed in a
lightly greased tapered brass sleeve without O-ring seals.
(15) The void between the concrete and the sleeve shall be filled with
epoxy resin.
(16) After the epoxy resin has hardened and fully cured, the
specimens shall be removed from the sleeve and the drafting tape shall
be removed from both surfaces.
Procedure :
determination
of water
permeability
by laboratory
test rig
7.5
(1) The short term water permeability resistance of the coating
system shall be determined as follows :
(a)
The specimen shall be placed in the permeability rig with
all the bolts tightened.
(b)
The water, at 2 bar pressure (20?m head), shall be applied
through the rig to the bottom (uncoated) face of the
specimen.
(c)
The time for water to appear through the coated face shall
be recorded over a 24 hour period.
(d)
The water permeability of the coating, measured from two
determinations shall be considered resistant if no water
has penetrated through the coating during the test period.
(2) The long term water permeability resistance of the coating
system shall be determined in accordance with Clause?7.5(1), except
that the duration of the test shall be three months.
- 74 ­
Procedure :
determination
of water
permeability
by CLAM
Tester
7.6
The procedure from the operation manual of the CLAM In-situ
Permeability Tester shall be followed.
Reporting of
results
7.7
The following shall be reported :
(a)
The name of the coating system and batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The results for short term resistance to water penetration
at the mean DFT.
(g)
The results for long term resistance to water penetration at
the mean DFT.
(h)
Whether the samples have been subjected to artificial
weathering and the duration.
- 75 ­
Figure 7.1 - Permeability Test Rig
- 76 ­
- 77 ­
APPENDIX 8
DETERMINATION OF THE BOND STRENGTH
OF COATINGS
Scope
8.1 This method covers the determination of the bond strength of coatings
for concrete by the direct pull-off test.
Materials
8.2 The following materials are required.
(a)
Ordinary Portland cement complying with BS?12:1989.
(b)
Oven-dry natural sand with rounded particle shape and
Zone M grading complying with BS?882:1983, Table?5.
(c)
20?mm graded coarse
BS?882:1983, Table?4.
(d)
Petroleum jelly, mineral oil or a proprietary mould
releasing agent.
(e)
A steel dolly of 50 mm diameter to fit for the direct pulloff tester.
(f)
Fast set epoxy adhesive.
aggregate
complying
with
Equipment
8.3 The LIMPET tester developed by Queen’s University, Belfast, shall be
used.
Procedure :
preparation of
specimen
8.4
(1) Concrete of Grade 20/20 shall be used to prepare the specimens
and the approximate proportions shall be in accordance with Table?8.1;
trial mixes shall be used to finalize the concrete mix.
Table 8.1 Mix proportions for concrete specimens
Ordinary Portland Cement (BS?12)
Zone M Sand (BS?882)
20 mm Graded Aggregate (BS?882)
Water (free)
Slump
28 day cube strength (Target Mean)
250 kg/m3
625 kg/m3
1250 kg/m3
190 L/m3
75 mm
25 MPa
(2) Concrete panels of 500?mm x 500?mm x 50?mm shall be
fabricated using fair-faced ply moulds.
(3) All materials and moulds shall be conditioned at 27 ¡ ⎝C for 24
hours before casting.
- 78 ­
(4) After mixing, the concrete shall be placed and compacted within
30 minutes into cleaned, lightly oiled moulds. The concrete shall be
finished by trowelling with a wood float, and then covered with
polythene sheeting for 24 hours.
(5) After 24 hours, the mould shall be stripped and the panels shall
be wrapped in polythene sheeting and stored at 27 ¡ ⎝C for at least 28
days, until ready for coating application.
(6) The test face shall be the moulded 500 x 500?mm side of the
panel.
(7) The test face shall be prepared in accordance with the
manufacturer’s instruction by either wire brushing, grit blasting or high
pressure water blasting, followed by filling of blow hole defects as
required. In the absence of instructions from the manufacturer, a mix
comprising 1:2.5 OPC/Zone F sand complying with BS?882:1983 and
2:1 water/SBR solution shall be used for filling blow holes and defects,
and shall be applied to a damp concrete surface. The filled surface
shall be covered with polythene sheeting and left for 24 hours at 27 t
2⎝C prior to coating.
(8) The coating shall be applied in accordance with the
manufacturer’s instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
(9)
Application shall be by spray, brush or roller.
(10) 10 panels shall be prepared in one operation for all tests to be
carried out, including spares.
(11) After coating, the specimens shall be conditioned at 27 ¡ ⎝C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(12) Following conditioning, a 50?mm diameter partial core shall be
made at 3 test locations to a nominal depth which shall be 5?mm
greater than the thickness of the coating under test so as to ensure that
the 50?mm core bit passes into the concrete substrate.
(13) 2 coated core samples shall be cut in half and the maximum,
minimum and mean DFT measured using a travelling microscope; the
mean value shall be taken from at least 30 observations.
Procedure :
determination
of bond
strength
8.5 (1) The coated surface of each partial core shall be degreased with
alcohol and a steel dolly shall be bonded onto the coating using fast set
epoxy adhesive.
(2) After the epoxy has cured and hardened, the Limpet tester shall
be set over the dolly and the pull rod shall be screwed into the thread
- 79 ­
of the dolly.
(3) The test procedure outlined in the operation manual of the tester
shall be followed.
(4)
After failure, the failure load shall be recorded.
(5) The mode of failure shall be recorded by examining the portion
adhering to the dolly as shown in Figure 8.1 and using the system
listed in Table 8.2.
Table 8.2 : Failure mode of bond strength test
Category
Failure Mode
Type 1
Concrete bond - concrete and coating attached to dolly
Type 2
Primer bond - top coats and primer attached to dolly
Type 3
Intercoat bond - failure between :
(a) primer and top coat
(b) top coats or within coating
(c) top coat and dolly adhesive
Note : where combined failures occur, the percentages of each type
of failure shall be given (e.g. 30% Type 1, 70% Type?3b).
(6) The adhesion of the coating system shall be considered
satisfactory when all three results produce failure which is
predominantly within the concrete substrate (>75% Type 1) and the
bond strength at each location exceeds 0.7?MPa.
(7) Failures which lie predominantly at the bond line (>75%
Type?2) may indicate poor surface preparation or a reaction between
the concrete and coating, and shall only be considered satisfactory
where the bond strength is 3 1.2?MPa.
(8) Failure of the dolly adhesive to bond to the coating (Type 3c),
indicates poor dolly preparation and a repeat test shall be carried out.
(9) Failures predominantly within layers of the coating system
(>75% Type 3a or 3b) shall only be considered satisfactory where the
bond strength is 3 1.2?MPa.
Reporting of
results
8.6
The following shall be reported :
(a)
The name of the coating system and the batch numbers.
- 80 ­
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The results for the bond strength of the coating, being
satisfactory or otherwise, and comments on the modes of
failure, where applicable.
(g)
Whether the samples have been subjected to artificial
weathering and the duration.
- 81 ­
Figure 8.1 - Possible Failure Modes
- 82 ­
- 83 ­
APPENDIX 9
DETERMINATION OF THE RESISTANCE TO
AGGRESSIVE LIQUIDS OF COATINGS
Scope
9.1 This method covers the determination of the resistance of coatings for
concrete to aggressive liquids.
Materials
9.2 The following materials are required.
Procedure :
preparation of
specimen
9.3
(a)
Ordinary Portland cement complying with BS?12:1989.
(b)
Oven-dry natural sand with rounded particle shape and
Zone M grading complying with BS?882:1983, Table?5.
(c)
20?mm graded coarse
BS?882:1983, Table?4.
(d)
Petroleum jelly, mineral oil or a proprietary mould
releasing agent.
(e)
Appropriate concentrations of the chemicals constituting
the aggressive liquids.
(f)
Epoxy resin adhesive.
aggregate
complying
with
(1) Concrete of Grade 20/20 shall be used to prepare the specimens
and the approximate proportions shall be in accordance with Table?9.1;
trial mixes shall be used to finalize the concrete mix.
Table 9.1 Mix proportions for concrete specimens
Ordinary Portland Cement (BS?12)
Zone M Sand (BS?882)
20 mm Graded Aggregate (BS?882)
Water (free)
Slump
28 day cube strength (Target Mean)
250 kg/m3
625 kg/m3
1250 kg/m3
190 L/m3
75 mm
25 MPa
(2) Concrete panels of 500?mm x 500?mm x 50?mm shall be
fabricated using fair-faced ply moulds.
(3) All materials and moulds shall be conditioned at 27 ¡ ⎝C for 24
hours before casting.
(4) After mixing, the concrete shall be placed and compacted
within 30 minutes into cleaned, lightly oiled moulds. The concrete
shall be finished by trowelling with a wood float, and then covered
- 84 ­
with polythene sheeting for 24 hours.
(5) After 24 hours, the mould shall be stripped and the panels shall
be wrapped in polythene sheeting and stored at 27 ¡ ⎝C for at least 28
days, until ready for coating application.
(6) The test face shall be the moulded 500?mm x 500?mm side of
the panel.
(7) The test face shall be prepared in accordance with the
manufacturer’s instruction by either wire brushing, grit blasting or high
pressure water blasting, followed by filling of blow hole defects as
required. In the absence of instructions from the manufacturer, a mix
comprising 1:2.5 OPC/Zone F sand complying with BS?882:1983 and
2:1 water/SBR solution shall be used for filling blow holes and defects,
and shall be applied to a damp concrete surface. The filled surface
shall be covered with polythene sheeting and left for 24 hours at 27 t
2⎝C prior to coating.
(8) The coating shall be applied in accordance with the
manufacturer’s instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
(9)
Application shall be by spray, brush or roller.
(10) 10 panels shall be prepared in one operation for all tests to be
carried out, including spares.
(11) After coating, the specimens shall be conditioned at 27 ¡ ⎝C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(12) Following conditioning, ten 100?mm diameter by 50?mm thick
core samples shall be taken from the panels.
(13) 2 coated core samples shall be cut in half and the maximum,
minimum and mean DFT measured using a travelling microscope; the
mean value shall be taken from at least 30 observations.
Procedure :
determination
of resistance
to aggressive
liquids
9.4
(1) A perspex cylinder of 80?mm internal diameter shall be bonded
onto the coated surface of the 100?mm core using epoxy resin
adhesive.
(2) The specimen and chemicals to be used shall be conditioned at
40 ¡ ⎝C for 24 hours prior to commencing the test.
(3) The chemicals shall be poured into the cylinder to pond onto the
coated concrete surface to a depth of 10?mm and the arrangement
maintained at 40 ¡ ⎝C throughout the test.
- 85 ­
(4) The surface of the coating shall be inspected periodically for
change of colour and failure due to expansive eruption of the
cementitious substrate.
(5) After testing for three months, the coating shall be considered
resistant to chemicals if no noticeable deterioration has been found in
either of the two specimens tested.
Reporting of
results
9.5
The following shall be reported :
(a)
The name of the coating system and batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The results for the chemical resistance of the coating,
being either resistant or not resistant at the mean DFT.
- 86 ­
- 87 ­
APPENDIX 10
DETERMINATION OF WATER UPTAKE OF
COATINGS
Scope
10.1 This method covers the determination of the water uptake of coatings
for concrete by the method of BS?1881:Part?5, Initial Surface
Absorption Test (ISAT).
Materials
10.2 The following materials are required.
Procedure :
preparation
of
specimens
(a)
Ordinary Portland cement complying with BS?12:1989.
(b)
Oven-dry natural sand with rounded particle shape and
Zone M grading complying with BS?882:1983, Table?5.
(c)
20 mm graded coarse aggregate complying with
BS?882:1983, Table?4.
(d)
Petroleum jelly, mineral oil or a proprietary mould
releasing agent.
(e)
Oil-based modelling clay.
10.3 (1) Concrete of Grade 20/20 shall be used to prepare the specimens
and the approximate proportions shall be in accordance with
Table?10.1; trial mixes shall be used to finalize the concrete mix.
Table 10.1 Mix proportions for concrete specimens
Ordinary Portland Cement (BS?12)
Zone M Sand (BS?882)
20 mm Graded Aggregate (BS?882)
Water (free)
Slump
28 day cube strength (Target Mean)
250 kg/m3
625 kg/m3
1250 kg/m3
190 L/m3
75 mm
25 MPa
(2) Concrete panels of 500?mm x 500?mm x 50?mm shall be
fabricated using fair-faced ply moulds.
(3) All materials and moulds shall be conditioned at 27 ¡ ⎝C for 24
hours before casting.
(4) After mixing, the concrete shall be placed and compacted within
30 minutes into cleaned, lightly oiled moulds. The concrete shall be
finished by trowelling with a wood float, and then covered with
polythene sheeting for 24 hours.
- 88 ­
(5) After 24 hours, the mould shall be stripped and the panels shall
be wrapped in polythene sheeting and stored at 27 ¡ ⎝C for at least 28
days, until ready for coating application.
(6) The test face shall be the moulded 500 x 500?mm side of the
panel.
(7) The test face shall be prepared in accordance with the
manufacturer’s instruction by either wire brushing, grit blasting or high
pressure water blasting, followed by filling of blow hole defects as
required. In the absence of instructions from the manufacturer, a mix
comprising 1:2.5 OPC/Zone F sand complying with BS?882:1983 and
2:1 water/SBR solution shall be used for filling blow holes and defects,
and shall be applied to a damp concrete surface. The filled surface
shall be covered with polythene sheeting and left for 24 hours at 27 t
2⎝C prior to coating.
(8) The coating shall be applied in accordance with the
manufacturer’s instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
(9)
Application shall be by spray, brush or roller.
(10) 10 panels shall be prepared in one operation for all tests to be
carried out, including spares.
(11) After coating, the specimens shall be conditioned at 27 ¡ ⎝C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(12) Following conditioning, ten 100?mm diameter by 50?mm thick
core samples shall be taken from the panels.
(13) 2 coated core samples shall be cut in half and the maximum,
minimum and mean DFT measured using a travelling microscope; the
mean value shall be taken from at least 30 observations.
Procedure :
determination
of water
uptake
10.4 (1) After calibrating the ISAT equipment, the circular cap shall be
sealed onto the coated concrete panel with oil-based modelling clay.
(2)
The test shall be performed in accordance with BS?1881:Part?5.
(3) The rate of water uptake into the coated panel shall be
determined after 10 minutes, 30 minutes, 1 hour and 2 hours, and shall
be calculated to the nearest 0.005?mL/m2s.
(4) The coating system shall be considered as resistant to water
uptake if the calculated water uptake after 2 hours is less than
0.025?mL/m2s.
- 89 ­
(5) The test shall be repeated at a second location and the mean
result obtained.
Reporting of
results
10.5 The following shall be reported :
(a)
The name of the coating system and batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
The rate of water uptake to the nearest 0.005?mL/m2s.
(g)
The result for the resistance to water uptake of the
coating, expressed as either resistant or not resistant at the
mean DFT.
(h)
Whether the samples have been subjected to artificial
weathering and the duration.
- 90 ­
- 91 ­
APPENDIX?11
DETERMINATION OF THE IMPACT
RESISTANCE OF COATINGS
Scope
11.1 This method covers the determination of the impact resistance of
coatings for concrete, by falling weight indenter.
Materials
11.2 The following materials are required.
Equipment
(a)
Ordinary Portland cement complying with BS?12:1989.
(b)
Oven-dry natural sand with rounded particle shape and
Zone M grading complying with BS?882:1983, Table?5.
(c)
20 mm graded coarse aggregate complying with
BS?882:1983, Table?4.
(d)
Petroleum jelly, mineral oil or a proprietary mould
releasing agent.
11.3 (1) The standard equipment to BS?3900:Part E3, fitted with a
14?mm diameter indentor and 4.75?kg weight.
(2)
Procedure :
preparation
of
specimens
A modified base plate as shown in Figure 11.1.
11.4 (1) Concrete of Grade 20/20 shall be used to prepare the specimens
and the approximate proportions shall be in accordance with
Table?11.1; trial mixes shall be used to finalize the concrete mix.
Table 11.1 Mix proportions for concrete specimens
Ordinary Portland Cement (BS?12)
Zone M Sand (BS?882)
20 mm Graded Aggregate (BS?882)
Water (free)
Slump
28 day cube strength (Target Mean)
250 kg/m3
625 kg/m3
1250 kg/m3
190 L/m3
75 mm
25 MPa
(2) Concrete panels of 200?mm x 200?mm x 100?mm shall be
fabricated using fair-faced ply moulds.
(3) All materials and moulds shall be conditioned at 27 ¡ ⎝C for 24
hours before casting.
- 92 ­
(4) After mixing, the concrete shall be placed and compacted within
30 minutes into cleaned, lightly oiled moulds. The concrete shall be
finished by trowelling with a wood float, and then covered with
polythene sheeting for 24 hours.
(5) After 24 hours, the mould shall be stripped and the panels shall
be wrapped in polythene sheeting and stored at 27 ¡ ⎝C for at least 28
days, until ready for coating application.
(6) The test face shall be the moulded 200?mm x 200?mm side of
the panel.
(7) The test face shall be prepared in accordance with the
manufacturer’s instruction by either wire brushing, grit blasting or high
pressure water blasting, followed by filling of blow hole defects as
required. In the absence of instructions from the manufacturer, a mix
comprising 1:2.5 OPC/Zone F sand complying with BS?882:1983 and
2:1 water/SBR solution shall be used for filling blow holes and defects,
and shall be applied to a damp concrete surface. The filled surface
shall be covered with polythene sheeting and left for 24 hours at 27 t
2⎝C prior to coating.
(8) The coating shall be applied in accordance with the
manufacturer’s instructions, using all necessary primers and
undercoats, and coverage rates shall be checked by weighing.
(9)
Application shall be by spray, brush or roller.
(10) 10 panels shall be prepared in one operation for all tests to be
carried out, including spares.
(11) After coating, the specimens shall be conditioned at 27 ¡ ⎝C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(12) Following conditioning, ten 100?mm diameter by 50?mm thick
core samples shall be taken from the panels.
(13) 2 coated core samples shall be cut in half and the maximum,
minimum and mean DFT measured using a travelling microscope; the
mean value shall be taken from at least 30 observations.
Procedure :
determination
of impact
resistance
11.5 (1) Two test specimens shall be used for each determination,
conditioned at 5 ¡ ⎝C and 70 ¡ 5 %rel ati ve hu m
i dit y, and at 27 ¡ ⎝C
and 80 ¡ 5 %rel ati ve hu m
i dit y respecti vel y f or 24 hours bef oret esti ng
(2) In order to prevent flexural failure under impact load, each
specimen shall be located in a bed of sand which will absorb the
impact stress wave.
- 93 ­
(3) The test shall be performed in accordance with BS?3900:Part?E3
with the impactor dropping onto the panel from a height of 570?mm at
three strike locations as shown in Figure?11.2.
(4)
The following defects shall be recorded :
(a)
(b)
(c)
(5)
the presence of cracking and extent,
delamination of coating and substrate condition, and
the occurrence of chipping.
The test panel shall be photographed.
(6) The continuity of the coating after the test shall be measured
using an ISAT type of tester as stated in Appendix?10 at a water
column head of 225?mm.
(7) The coating system shall be considered to be satisfactory under
the impact test if the water uptake after 2 hours is ⎝ 0.025?mL/m2sec.
Reporting of
Results
11.6 The following shall be reported :
(a)
The name of the coating system and the batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured mean, minimum and maximum DFT.
(e)
Comments on any application or testing irregularities.
(f)
A description of the defects after the impact test.
(g)
The results for water uptake of the impact area, being
classed as either satisfactory or not satisfactory after
impact at the mean DFT.
(h)
Whether the samples have been subjected to artificial
weathering and the duration.
- 94 ­
Figure 11.1 - Modified BS 3900 Impact Tester for Concrete
- 95 ­
Figure 11.2 - Typical Failed Concrete Panel
- 96 ­
- 97 ­
APPENDIX 12
DETERMINATION OF THE ALGAE RESISTANCE
OF COATINGS
Scope
12.1 This method covers the determination of the algae resistance of
coatings for concrete based on SISIR test method.
Materials
12.2 The following materials are required.
Apparatus
Procedure :
preparation
of
specimens
(a)
Sterilized Bold Basal medium.
(b)
Algae culture, predominantly
cultured in Bold Basal medium.
(c)
Sterilized distilled water.
Tretapohila
Odorata
12.3 The following apparatus is required.
(a)
Four sterilized petri dishes, of approximately 90 mm
diameter, with covers.
(b)
A shelf with fluorescent lighting such that the light
intensity incident to the test surface is 1000 to 1400 lux.
(This can be achieved by installing two 40-watt cool
fluorescent lamp tubes approximately 25?cm apart at a
horizontal level and approximately 60?cm above the test
surface).
(c)
An autoclave of 1.2 to 1.5 kgf/cm2.
12.4 (1) A special primer or pretreatment (e.g. hydrofluoric acid etch) for
the glass shall be applied to the inner surfaces and edges of the glass
petri dishes for bonding purposes, according to the manufacturer’s
instructions.
(2) All chemicals, water, non-disposable containers and tools used
for the test shall be sterilized by the autoclave under a pressure of 1.2
to 1.5 kgf/cm2for 30 minutes.
(3) All materials shall be conditioned at 27 ¡ ⎝C for 24 hours prior
to application.
(4) The coating system shall be applied to the inner surfaces and
edges of two sterilized, petri dishes in accordance with the
manufacturer’s instructions.
(5)
The coverage rates for the coating shall be checked by
- 98 ­
weighing and by wet film thickness measurement (e.g. comb gauge).
(6) After coating, the specimens shall be conditioned at 27 ¡ ⎝C
and 80 ¡ 5 %rel ati ve hu m
i dit y f or 6 weeks t o per m
it nat ural l oss o
solvents and other volatile materials.
(7) The DFT of the coating shall be estimated by re-weighing the
specimens.
Procedure :
determination
of algae
resistance
12.5 (1) The two coated petri dish specimens shall be artificially
weathered to 4000 hours in accordance with Appendix 3.
(2) After weathering, the specimens shall be inoculated with the
algal species by adding 2?mL of algae culture onto two coated and two
uncoated petri dishes. The culture shall be spread on the surface as
evenly as possible, so that it covers approximately 10% of the bottom
of the surface of the petri dish.
(3) After inoculation with the algae culture, the petri dishes shall be
covered with dish covers and subjected to exposure under fluorescent
lighting at a temperature of 27 ¡ ⎝C using a lighting cycle of 12 hours
on followed by 12 hours off.
(4) The coating film shall be kept moist by periodically adding a
diluted Bold Basal medium of 1 part Bold Basal medium to 3 parts of
distilled water by volume; normally no more than 1?mL every 2 days
shall be required.
(5) The period of exposure shall be 8 weeks from the date of
inoculation of the algae culture. During the exposure period, the petri
dishes shall be kept covered.
(6) At the end of the test, the growth intensity of algae on the
coating samples shall be compared with those of the blank controls.
(7) The coating shall be considered to have passed the test if the
algae culture is killed, as evidenced by the bleaching of the green
colour. Any growth shall be compared with the increase in algal
growth in the blank petri dishes.
Reporting of
results
12.6 The following shall be reported :
(a)
The name of the coating system and the batch numbers.
(b)
The name of the manufacturer and Hong Kong supplier.
(c)
The coverage rates used for each component of the
coating system.
(d)
The measured wet film thickness and estimated DFT.
- 99 ­
(e)
Comments on any application or testing irregularities.
(f)
The results for the algal resistance of the coating system,
being classed as either resistant or non-resistant to algal
growth at the estimated DFT.
- 100 ­
- 101 ­
APPENDIX 13
METHODS FOR THE ANALYSIS OF COATING
SAMPLES
Scope
13.1 This appendix covers the test methods for site quality control of
coatings for concrete.
Method :
determination
of volatile
content
13.2 (1) A 200 mL coating sample shall be poured into a pre-weighed
disposable metal container and the sample shall be weighed.
(2) The sample shall be dried in a ventilated oven at 105 ¡ 5⎝C for 3
hours.
(3) After allowing the sample to cool in a desiccator for 15 ¡
minutes, the sample shall be re-weighed.
(4) The volatile content of the coating sample shall be calculated as
follow :
Wo - Wd
Wv =
x 100%
Wo
where :
Wv is the volatile content of the coating sample (%),
Wo is the initial weight of the coating (g), and
Wd is the oven-dry weight of the coating (g).
Method :
determination
of fineness of
grind
13.3 The fineness of grind of the coating shall be determined in accordance
with the method stated in ASTM D?1210, using a grindometer at a
temperature of 27 ¡ ⎝C.
Method :
determination
of viscosity
13.4 The viscosity of the coating shall be measured in accordance with the
flow cup method stated in BS?3900:Part A6, 1986 at a temperature of
27 ¡ ⎝C.
Method :
determination
of specific
gravity
13.5 The specific gravity of the coating shall be determined in accordance
with the density bottle method stated in BS?3900:Part A12, 1975 at a
temperature of 27 ¡ ⎝C.
Additional
Testing
13.6 If instructed by the Engineer, coating samples shall be sent for
labelling using infra-red spectography and pyrolysis gas
chromatography, and the results shall be compared with master data
supplied by the manufacturer.
- 102 ­
- 103 ­
APPENDIX 14
METHODS FOR CHECKING THE CONTINUITY
OF FILM FORMING COATINGS ON CONCRETE
Scope
14.1 This appendix covers the test methods for checking the film thickness
and continuity of coatings for concrete.
Method :
determination
of thickness
14.2 (1) For rough concrete surfaces, the measurement of film thickness
shall be obtained from a microscopic examination of the coated surface
of core samples, that have been either purpose-cut or taken from other
tests.
(2) Spot checks shall be made by drilling a tapered hole into the
film using an Erichsen Paint Borer and measuring the thickness and
number of coats.
Method :
determination
of continuity
14.3 (1) The continuity of the coating shall be measured using a concrete
resistivity meter. One lead of the meter shall be connected to the
reinforcing cage in the concrete, in contact with the bar beneath the
area of coating under test. The circuit shall be completed by using a
sponge contact unit soaked in a suitable electrolyte, which is pressed
onto the coated concrete surface.
(2) The resistance readings shall be obtained from the resistivity
meter, to give an indication of the continuity of the coating.
(3) The coating shall be considered continuous if the resistance
reading gives values in excess of 1?MΩ. Pinholes in the coating will
reduce the resistance.
- 104 ­
- 105 ­
APPENDIX 15
SIMPLE METHOD FOR CHECKING THE
ADHESION OF FILM FORMING COATINGS ON
CONCRETE
Scope
15.1 This appendix covers the cross-cut test for checking the adhesion of
coatings for concrete.
Method :
cross-cut
test
15.2 The adhesion test shall be carried out in accordance with the cross-cut
test stated in ASTM?D?3359-83, except as modified below?:
Note :
(a)
The coated surface shall be scribed with 11 parallel cuts,
made using a sharp cutting tool to BS?3900:Part?E6
against a steel straight edge. The cuts shall be spaced at
3?mm centres and each shall be at least 50?mm in length.
(b)
A second series of 11 cuts shall then be made,
perpendicular to the first series, to form a lattice pattern.
(c)
A 30?mm wide adhesive tape shall be pressed over the
lattice with even thumb pressure, left for 1 minute and
then peeled off sharply in less than 0.5 second.
(d)
The surface shall be inspected using normal vision and
classified as either having passed or failed the criterion of
⎝ 25% of the surface having come away.
A suitable tape has an adhesive bond of 44.6 ¡ 2. 8?g/ mm
measured in accordance with ASTM?D?3330, such as
Permacel 99 by Permacel Inc., New Brunswick, USA.
3M "Red Lithographic Tape" may also be suitable.