STUDY ON WATERPROOFING METHODS USED 
FOR CONCRETE SLABS
Rajitha Fonseka,
Department of Civil Engineering, University of Moratuwa. 
(email: rajithahiru^gmail.com)
K. Baskaran,
Department of Civil Engineering, University of Moratuwa. 
(email: baskaran@civil.mrt.ac.lk)
L. L. Ekanayake,
Department of Civil Engineering, University of Moratuwa. 
(email: lesly@dvil.mrtac.lk)
Abstract
watertight enough on their own. Therefore, waterproofing has become an essential component of a 
structure to protect its aesthetic appearance, prevent structural damages and for the safety of the 
occupants. For concrete slabs, major objective will be to stop the water intrusion into the interior of the 
building at various locations under various exposure conditions. Accordingly the type and the 
method of waterproofing required may vary with the location and exposure conditions. In the 
construction industry, many commercially available materials are used for waterproofing ground 
slabs, roof slabs and bathroom floors. In this research, field surveys were done to identify the types of 
waterproofing material, different methods of applications and quality controlling measures regarding 
to waterproofing. Furthermore, issues related to waterproofing were studied to identify common 
problems which can be arrived in a functioning building. Then the rectifying methods and their 
performance related to such issues were also studied. A laboratory test serieswas performed on 
commercially available waterproofing materials to check their suitability. After applying 
waterproofing materials ontest specimens, they were checked for water absorption under laboratory 
conditions for 24 hours. Furthermore specimens with integral admixtures were tested for compressive 
strength to identify any increase in their compressive strength due to crystalline formation.
A building or a structure requires waterproofing, if the building materials are not
Waterproofing, Slabs, Crystallization, Integral waterproofingKeywords:
the past decades. They are traditional 
materialsand modern materials. Examples of 
those materials are categorized in Table 1.
Introduction1.
Waterproofing is a fundamental requirement of 
a structure in order to protect its aesthetic 
appearance, prevent structural damages and for 
the safety of the occupants. It is identified as a 
major requirement because the building 
materials (mostly reinforced concrete) will not 
be able to waterproof structure itself under 
different exposure conditions such as direct 
sunlight, direct rainfall during the lifetime of a 
building. So waterproofing can be simply 
defined as preventing water intrusion and 
extrusion from various parts of a structure. This 
can be achieved by providing an impermeable 
barrier specifically designed for the intended 
purpose.
Basically, there are two types of waterproofing 
materials used in the construction industry over
Table 1: Traditional & modern waterproofing 
materials
Traditional Materials Modern Materials
Internal waterproofing 
____ compounds____
Silicon based water
repellent
Bitumen coating with 
sand sprinkling
Polymerized
bitumen
Waterproofing
membranePoly ethylene film
Waterproofing by 
crystallizationAluminium foil
All these materials are more or less used for 
different kind of purposes in the construction 
industry and each method has its own
29
rtwo types of integral waterproofing 
compounds namely reactive and un-reactive. 
Reactive compounds truly waterproof 
structures by forming crystalizing compounds 
when moisture is penetrated to the concrete. On 
the other hand un-reactive compounds reduce 
the permeability of concrete by increasing the 
density of it. Like reactive compounds they do 
not reactivate in the presence of water. 
Generally integral waterproofing is considered 
as a one-time treatment (Biparva &Yuers).
be used for different 
different exposure 
suitable
areproperties, which 
applications
conditions. Therefore, selecting a 
waterproofing method and a material depends 
on various parameters. Before selecting a 
waterproofing method for a particular 
application, the ways which water can 
within a structure to cause problems need to be
move within a
can
under
move
studied. Basically water can 
structure due to gravity, wind and surface 
tension. However this will depend on the 
conditions as mentioned before.exposure
Therefore, it is required to study the possible 
ways of water entering paths and exposure 
conditions well before applying a particular
Previous research2.2
A collaborative experimental program has been 
carried out by Dias (2007) with FINCO (PVT) 
Ltd. to test the effectiveness of concrete 
waterproofing systems in Sri Lanka. In this 
experiment both admixture and coating 
waterproofing systems have been tested to 
check their suitability for water retaining 
structures. After preparing specimens using 
grade 40 concrete, permeability and sorptivity 
tests have been carried out to check their 
effectiveness. Two waterproofing products 
namely XYPEX Admix and XYPEX Coating 
have been tested with control specimens with 
added silica fume under this experiment. It has 
been found that XYPEX Admix give the best 
performance against a considerable water head 
implying that it is suitable for water retaining 
structures. Specimens with silica fume have 
given the best performance for the resistance 
against water penetration into unsaturated 
concrete. And according to the test results 
XYPEX Coating has not performed as well as 
expected.
waterproofing material.
Therefore, this research was carried out to 
study the waterproofing methods used for 
concrete slabs.
Waterproofing Methods2.
What is waterproofing?2.1
Waterproofing can be achieved by the 
formation of an internal or external membrane 
which is capable of preventing water from 
entering or escaping through a permeable layer. 
Further it can be defined as the formation of an 
internal or external membrane which is capable 
of preventing water from entering or escaping 
through a permeable layer. There are many 
different means to provide internal or external 
membranes in the construction industry. 
Internal/intcgral membranes are provided via 
waterproofing admixtures, which are added to 
the concrete during the mixing process. 
External membranes are provided using sheet 
membranes and liquid coatings on the concrete 
surface (Biparva &Yuers).
Primary objective of a waterproofing 
membrane is to prevent water from entering to 
the occupant area during its life time. 
Therefore the performance of a water proofing 
membrane can be measured by the 
permeability of the membrane. In the research 
by Sahal and Ozkan (2004), they have presented 
performance-based laboratory test 
method to assess the vapour and water 
permeability of strained waterproofing 
membranes under hydrostatic pressure. In this 
test method they have simulated strain 
conditions using membrane test specimens in 
laboratory conditions. Other field conditions 
such as air and hydrostatic pressure arc also 
simulated on the strained specimen and the 
vapour and water permeability of the specimen 
is measured in a test apparatus. This laboratory 
test method is considered to be a new approach 
that can help to estimate the vapour and water
External waterproofing membranes can be 
divided into two categories as liquid-applied 
membranes and sheet applied membranes. 
Liquid-applied products 
coatings, which can be produced at site by 
mixing liquid and powder according to the 
given ratio. Sheet membranes are normally 
made from thermoplastics, vulcanized rubber 
and
membranes can be bonded to the surface or can 
be left un-bonded (Biparva &Yuers).
Internal/integral waterproofing 
considered as a technology which uses 
admixtures to prevent the movement of water 
by blocking the pores inside the concrete. Th
are cementitous new
rubberized asphalts. These sheet
can be
ere
30
bituminous membranes with a self-protection 
constituted by mineral granules. These granules 
constitute the barrier against the fundamental 
environmental agent of degradation, the UV 
radiation. Marques et al (2010),have presented 
an experimental study on the behaviour of the 
self-protection granule of bituminous 
membranes when subjected to environmental 
agents of degradation. Different types of 
bituminous membranes, with different 
finishing systems have been exposed to the 
effects of elevated temperature and water for 
up to 24 weeks and 4 weeks respectively. 
Following accelerated ageing, specimens of the 
different types of membranes were subjected to 
brushing tests in order to evaluate the adhesion 
of the self-protection granules. Experimental 
results have shown that the higher loss of self­
protection granule of bituminous membranes 
occurs in membranes modified by Atactic 
polypropylene polymers. In addition, it has 
been concluded that the effect of water is much 
more severe than that of the elevated 
temperature.
permeability of the waterproofing membranes 
in field conditions.
Al-Zahrani et al (2002),conducted a study to 
evaluate reinforcement corrosion and some 
physical properties of concrete specimens 
coated with two polymer-based, a cement- 
based polymer-modified, and cement-based 
waterproofing coatings. The coated and 
uncoated concrete specimens have been 
subjected to accelerated corrosion to determine 
the time taken to initiate corrosion. The 
physical properties were also evaluated by 
subjecting the concrete specimens to 
wetting/drying cycles and heating/cooling 
cycles for five months. The physical properties 
such as water absorption, water permeability, 
chloride permeability, and adhesion were also 
evaluated. The accelerated corrosion test results 
have clearly showed that the specimens coated 
with the polyurethane elastomer-based 
waterproofing material performed better than 
concrete specimens coated with other 
waterproofing materials. This has been 
followed by the specimens coated with cement- 
based polymer modified, epoxy-based, and 
cement-based coatings in descending order. 
The two polymer-based coatings have shown 
better performance than the cement-based 
polymer-modified and cement-based coatings 
in terms of the evaluated physical properties.
3. Field Survey Results
In order to identify the waterproofing methods 
which are currently being used in the 
construction industry, a field survey was 
carried out. Industrial professionals were 
interviewed during the field survey to identify 
the issues related to waterproofing.
In most of the buildings, bituminous sheet 
membranes are used for the waterproofing 
purposes in roof slabs. These bituminous sheets 
are ideal for slabs having large spans so that it 
can cover a large area. However, when 
applying these sheets, lap joints will 
occur.Hence they will become the most critical 
areas in the waterproofing system. And also 
these lap joints are largely responsible for the 
defects which will occur with time. Therefore 
the dimensional stability of the sheets is one of 
the most important characteristics, as it can 
strongly influence the performance of the lap 
joints. In their research, Lopes et al (2010) have 
presented the results of an experimental study 
on the dimensional changes exhibited by 
bituminous sheets when subjected to 
temperature variations. This experiment has 
been done on different types of traditional and 
non-traditional sheets, with various types of 
bituminous mixtures. Experimental results 
have confirmed that the sheets with polyester 
reinforcement are much less stable than sheets 
reinforced with glass fibre.
General Site Practices3.1
Before applying the waterproofing, a surface 
preparation should be carried out properly. 
Surface should be free from debris, grout 
deposits and dust before applying the 
waterproofing material. After preparing the 
surface, any cracks or uneven areas should be 
filled with construction grout. Then a 45° fillet 
as shown in Figure 1 should be introduced with 
cement sand mortar along the edges where the 
slab meets vertical walls. This is done to ensure 
the proper continuity of waterproofing along 
edges.
As mentioned earlier, most of the flat roofs of 
the buildings are waterproofed by using Figure 1: 45° fillet along the edges
31
* l
I:
Then those edges and gully areas are reinforced
that the Floor levelby using fibre glass nets, so 
waterproofing can be made flexible along the 
edges. After mixing the powder and the liquid 
to the given ratio, thin slurry can be obtained to 
apply on the surface of the slab. Then the first 
coat is applied using the brush application 
method according to manufacturer s 
specifications. Second coat can be applied as 
the first coat is dried. To ensure water 
tightness, second coat is applied orthogonally 
to the direction of first coat. Then the curing is 
carried out for 1 or 2 days according to the 
manufacturer's specifications. At the end, 
ponding test will be carried out to check for any 
leakages. After filling the slab area with water, 
visual inspection will be done to detect any 
kind of leakage. If the waterproofing is 
satisfactory, slab area will be covered with a 
cement sand mortar to protect the 
waterproofing from foot traffic and other 
impacts.
*U Gully Pipe
Figure 2: Correct placement of gully pipe
Apart from that another type of water leakage 
occur under the door step of the bathroom. 
Most of the times, door steps are made out of 
bricks which can lead to a weak joint between 
the door step and the concrete slab. Therefore, 
with time water can leak to the adjacent bed 
room. If a slab drop is not provided for the 
bathroom area, water can leak to the adjacent 
bedroom also. Therefore, this can be avoided by 
providing a concrete door step if a slab drop is 
not provided.
soon as
can
3.2.2 Issues in Roof Slab Areas& Solutions
Common Issues3.2
Most of the time, waterproofing in roof slabs is 
done by using bituminous membranes. This is a 
popular method for waterproofing slabs with 
long spans including roof slabs and ground 
slabs. According to gathered data during field 
survey, with time these bituminous membranes 
will lose the bond with the surface due to the 
temperature especially when they are placed in 
roof slabs. Therefore, once the water enters 
through a damaged part of the membrane, it 
can flow anywhere under the membrane. With 
time this water can leak through the concrete to 
create water patches on the slab soffit. So, when 
a leakage occurs, it isdifficult to find a location 
to treat in such a case.Therefore, whole 
membrane should be removed and repaired in 
such a case.
Most issues in waterproofing occur in 
bathrooms and roof slabs as they are directly 
exposed to water.
3.2.1 Issues in Bathroom Areas & Solutions
Bathrooms are very vulnerable to water 
leakages if the correct procedure is not 
followed. Due to the discontinuity of the 
concrete slab at the edges cracks can develop 
around the fillets. Therefore, water can leak 
from the mortar joint under the brick wall. 
Same thing can happen around the gully, 
where a weak plane can develop with time.
According to the discussion,many problems in 
waterproofing can be avoided if the correct 
procedures are followed. One example is the 
placement of the gully pipe to avoid permanent 
ponding, which can stop water leakages around 
gulley. Sometimegulley pipe can be placed 
above the floor level to allow the drainage of 
water from the bathroom. But the problem 
occurs when the water is leaked from the tiles 
to the slab through the waterproofing which 
can
the tile cannot escape through the gulley pipe if 
it is placed above the slab level. Then the water 
patches will appear on the soffit of the slab. 
Therefore, waterproofing companies ask the 
client to place the gully pipe as shown in Fig 
2.
Another problem that can occur in roof slabs is 
due to the leakage from the parapet wall. These 
kinds of leakage are hard to identify, because a 
ponding test would not detect cracks in the 
parapet wall.In such a case, crack should be 
sealed by using a fibre glass mesh and a binder 
in order to stop the water flow. One such crack 
found in a parapet wall is shown in Figure 3.lead to permanent ponding. Water under
Another type of problem that can 
slab is the leakage that occurred from the edge 
of the slab. If the leakage is severe, slab soffit 
also be damaged due to the water patches. 
This will destroy the aesthetic appearance of
t ie building and reinforcement corrosion could 
also
in roofoccur
can
ure
• By providing a concrete step or aoccur
32
parapet wall, this type of leakage can be 
prevented by continuing the waterproofing 
membrane up to some height.
Admixture type waterproofing products should 
be added to the concrete when it is batched. So, 
it was decided to cast all the 21 specimens on 
same day, and add the admixtures separately 
for the required 9 cubes at the time of batching. 
Cementitous coating type materials were 
applied on the specimens after 14 days.
Testing Procedure4.4
It was decided to check the effectiveness of 
waterproofing materials by checking the water 
absorption of each product. There are many 
laboratory test methods to check the different 
parameters of the waterproofing products. But 
there is no specific test developed to measure 
the water absorption of waterproofing 
materials. However, to check the effectiveness 
of waterproofing materials, test for water 
absorption of concrete (BS 1881-122:1983) was 
adopted in this research.
Figure 3: Crack appeared in a parapet wall
Laboratory Experiments4.
4.1 Introduction
In order to identify the effectiveness of the 
commercially available waterproofing materials 
laboratory experiments were carried out. 
Cementitous coating type and integral 
waterproofing type materials were tested under 
the laboratory experiment series.
Initially a water absorption test was carried out 
on specimens without the oven drying 
procedure. Then the same test was carried out 
on specimens after oven drying them for 72 
hours. This was done to check whether the 
oven drying procedure causedany damage to 
waterproofing materials.
Materials4.2
It was decided to use grade 30 concrete to 
prepare concrete specimens for the test. As 
most of the building slabs are constructed using 
grade 25 or 30 concrete, results would 
demonstrate the actual site conditions if grade 
30 is used. Waterproofing materials given in 
table 2 were tested under this laboratory test 
series.
Final experiment was carried out to check the 
compressive strength of specimens, for which 
crystallizing admixtures were added. This was 
done to sec whether the compressive strength 
has been increased due to the crystallization 
effect. All the specimens with admixtures were 
tested using the compressive strength testing 
machine. Control samples were also tested to 
compare with the specimens cast using 
admixtures.
Table 2:Selected waterproofing materials
Cementitous coating 
type waterproofing
Admixture type 
waterproofing Test Results and Discussion5.
BrushbondXypex admix Water Absorption Test 15.1
Xypex ConcentrateTamscal admix
Test results of the water absorption test after 24 
hours without oven drying procedure are given 
in Table 3. According to the results it can be 
seen that all the specimens, which were 
waterproofed have performed better than the 
control specimens. Among them Kll Flex 
specimens gave the best results (0.19%) 
compared to control specimens (0.57%). Also, it 
can be seen that the liquid-applied 
waterproofing materials have given the best 
results compared to integral waterproofing 
compounds.
Kll flexPenetron admix
4.3 Methodology
Tests were carried out using 150 mm x 150 mm 
xl50 mm concrete specimens of grade 30 
concrete. For each waterproofing product, three 
cubes were cast and three control specimens 
were also cast separately. Therefore, altogether 
21 cubes were tested under this test.
33
■' ■
Table 3: Water Absorption Test Results (1) [After 24 hours]
Water Absorption (%) 
Value
nf \vater absorbed (g)
1440 min AverageInitial Weight (g) 420 min180 minCube Name 60 min30 min15 minMaterial 0.413535351510108440TA-1 0.4135 0.4125150008450TA-2Tamscal Admix 0.413535201510108620TA-3 0.353030151515158520XA-I 0.4840 0.3720202020208380XA-2Xypex Admix 0.302520155558465XA-3 0.413525151010108605Pe-1 0.3530 0.37251515508470Pc-2Penctron Admix 0.35302515151558490Pc-3 0.292515151515158685XC-1 0.2220 0.271055558900XC-2Xypex Concentrate 25 0.281555558780XC-3 0.403520105558710B1 0.45 0.4140251510558925B2Brushbond 0.383520105509145B3 0.2220500008935K-l 15 0.17 0.191050009055K-2K11 Flex 15 0.171000008960K-3
55 0.6440303030108560C-l
0.5745 0.5435302520158315C-2Control cubes
45 0.5340402020158565C-3
to obtain a constant mass of the specimens. 
However, according to the test results some 
specimens have absorbed more water than the 
control specimens. It can be assumed that the 
waterproofing has been damaged due to the 
oven drying procedure. However, in the second 
experiment also, Kll Flex specimen gave the 
best results compared to others.
Water Absorption Test 25.2
Test results of the water absorption test after 24 
hours with oven drying procedure are given in 
Table 4. When compared with the test results of 
the first experiment, it can be seen that the 
water absorption has significantly increased in 
the specimens of the second experiment. This is 
due to the oven drying procedure carried out 
prior to the test. Oven drying was done in order
Table 4: Water Absorption Test Results (2) [After 24 hours]
Mass of water absorbed fe)Material Cube Name Initial Weight (g) Water Absorption (%)15 min 30 min 60 min 180 min 420 min 1440 min
Tamscal Admix TA-2 8130 150 190 220 290 315 4.06330
Xypex Admix XA-3 8160 150 185 225 275 300 3.80310
Penctron Admix Pe-2 8195 135 170 200 235 255 3.29270
Xypex Concentrate XC-2 8560 160 205 245 295 315 3.86330
Brushbond B-l 8350 115 160 195 270 335 380 4.55
Kll Flex K-2 8740 50 70 85 125 165 230 2.63
Control cubes C-l 8245 165 215 260 305 330 350 4.24
34
5.3 Compressive Strength Test Conclusions6.
Results of the compressive strength test of each 
cube are given in the Table 5.
According to the field survey data, it can be 
concluded that the selection of waterproofing 
type for a particular application depends on 
the location of the structural element and the 
exposure conditions. Therefore, special care 
should be taken when selecting a 
waterproofing material for a new construction. 
However, problems which can occur in the 
construction stage are minimal.
Table 5: Compressive Strength Test Results
Density (kg/m3)Cube Name Compressive Strength (MPa)
TA-1 2440 51.17
TA-2 2489 35.59
TA-3 2548 44.60
XA-1 2502 38.0-1
XA-2 2474 47.39
XA-3 2519 34.02
Most of the waterproofing issues occur during 
the functioning period of the building. These 
issues arise due to poor selection of 
waterproofing 
workmanship. Therefore, the efficiency of 
waterproofing system cannot be guaranteed 
just by selecting a good quality waterproofing 
material as long as poor workmanship is 
involved.
Pe-l 2449 50.82
Pc-2 2454 32.72
Pe-3 2469 40.30
C-l 2460 37.60
andmaterials poorC-2 2476 39.38
C-3 2451 40.86
According to the test results it can be seen that 
the compressive strength of specimens with 
admixtures has been slightly increased 
compared to control samples. Average 
compressive strength of each set of specimens 
is given below. (Strength of oven dried 
samples are not considered for average 
compressive strength)
Liquid-applied membranes are the most 
common waterproofing systems which can be 
used to waterproof bathrooms, kitchens and 
balconies. Integral waterproofing admixtures 
are widely used nowadays to waterproof 
ground slabs, sump areas and lift cores. From 
the above mentioned waterproofing systems, 
integral waterproofing system is considered as 
a one-time treatment.
1) .TAMSEAL Admix- 47.89 MPa
2) . XYPEX Admix- 42.72 MPa
3) .PENETRON Admix- 45.56 MPa
4) .Control Samples- 40.12 MPa
A graphical representation of the average 
compressive strength of each product is given 
in the Figure 4.
According to the laboratory experiments, 
liquid-applied waterproofing systems perform 
better than the integral waterproofing systems. 
However, this conclusion is based on the water 
absorption test carried out on waterproofed 
specimens. More comprehensive tests should 
be done to check the effectiveness of 
waterproofing systems under different 
exposure conditions.
Compressive Strength Test Results
srrr
ir
I
ii References:!
L Vu Al-Zaharani, M., Al-Dulaijan, S., Ibrahim, M., 
Sandmen, H., & Sharif, F. (2002). Effect of 
waterproofing coatings on steel reinforcement 
corrosion and physical properties of concrete. 
Cement & Concrete Composites, 127-137.
Biparva, A., & Yuers, K. (n.d.). Integral 
Crystalline Waterproofing Technology. Retrieved 
12 11, 2013, from
http://www.slideshare.net/KrytonIntl/integr 
al-crystalline-watcrproofing-technology 
British Standard Institution. (1983). BS 1881- 
122. Method for determination of water absorption.
L—
XYPEX A.liniv IVwtron Admix Conlrx'l SamplesTjm«\>l Admix
Figure 4: Comparison of Compressive Strength
From the comparison it can be seen that the 
average compressive strength of specimens 
with TAMSEAL Admix has been increased by 
20% compared to control samples. 
PENETRON Admix has given a 14% increase 
in compressive strength while XYPEX Admix 
has given a 6.5% increase in compressive 
strength compared to control samples.
Slideshare:
35
I:
i- '
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36