Waterproofing : New Technology & Approach
Dr. M. S. Modak, Head- R&D and
Arijit Basu , Corporate Market Field Manager
(Waterproofing & Sealants)
Sika India Pvt. Ltd
A building for any use is constructed generally by using ---- concrete, brick, mortar, window, and
door. The purpose of the building is to protect inhabitants from rainwater, heat from Sun, and
storm. In performing so the building is also exposed to the environment existing around it.
Although a building will resist water infiltration but water leakage may take place through concrete,
wall, joints, pipe entries, gap between door and window frames. Out of these, leakage through
concrete takes place mainly due to high porosity. The other defects are due to bad workmanship. To
solve all these problems, Chemicals and accessories are available at present. Proper use of these
materials will enhance the durability of a building. But selection of such materials will play a major
role to impart the beneficial properties.
Chemicals and accessories:
During the manufacture of Concrete either Water Reducing or High Range Water Reducing
Admixtures can be used like Plastiment or Sikament of Sika India. The dosage of Plastiment is
normally 0.2 to 0.6% by weight of Cement and that of Sikament is 0.5 to 1.5%. The following
figures will explain the benefits.
Effect of Plastiment on Slump Effect of Sikament on Slump
Cement = 350 kg/m 3, W/C= 0.45
Cement = 350 kg/m 3, W/C = 0.43
100 92 150
50 100 95
0 0.2 0.4 0.6 0 0.5 1
Dosage, % by w t Dosage, % by w t.
The effect of Chemical on slump is observed from the above figures. To get this slump without
Chemical high w/c ratio of more than 0.55 should have been used. This excess water will generate
high porosity due to bleeding and evaporation, which may lead to leakage problem. So the use of
Chemical is beneficial from waterproofing point and this impart permanent solution. The above
products satisfy the requirement of Indian Standard IS 9103 – 1999.
Leakage through brickwork is another problem. In this case leakage takes place through the
mortars. To stop this Chemical like of Sika India can be used. This has the bifunctional property of
waterproofing and reduction of rebound loss. The rebound loss is that when green plaster falls
down during application. The rebound loss reduction will make the plastering job faster. Sika
Plastocrete Plus should be used @ 0.2% by weight of cement. The other material, which can be
used, is Sika Noleek CP of Sika India. This will bring in waterproofing and should be used @ 1.0%
by weight of cement. These products reduces water permeability by more than 50% as per the
requirement of Indian Standard IS 2645. Both the material should be used during making the
Use of Polymers in the form of dispersion in water with plaster brings in multiple benefits. To use
it in plasters, first it should be diluted with clean water in the ratio of 1:1 to 1:8, where 1 is Polymer
and the other part is water. The sand cement mixture is then mixed with this diluted Polymer
without using raw water. The benefits that is imparted are:
Good bond with the brick & concrete surface
Example of such Polymer is Sika Cemflex of Sika India. The following figures will show the
Effect of Sika Cemflex on Water Absorption
0 1:08 1:04 1:02
12 12 12.5
4.5 4.85 5
4 4 4.2
0 5 10 25
Immersion time, hour
Effect of Cemflex on Bond Strength
0 1:04 1:06 1:08
Cemflex : Water
From the above figures it is clear, properties are better with more Sika Cemflex, which is expected.
The gaps between doors and window frames can be insulated against water by the use of a suitable
sealant. This is available in sausage, cartridge or paste. It is applied on the gap and finished
properly. The aesthetic look increases to a great extent by its use. Examples of such sealants are
Sikaflex Construction and Sikacryl of Sika India. Sikaflex Construction is based on PU and Sikacryl
– acrylic. These sealants stretches with the movement of the gaps due to heat and cold and keeps
the gap sealed. Consumption of such sealant is around 5 running meter with 600ml material for
8x15 mm groove.For sealing pipe, electric cable entry points and the gap around AC machines in
the wall, PU foam can be used. This is available in metal containers in ready to use form and is
liquid in nature. As soon as it is injected in the gaps it expands to form foam. The foam is allowed
to hardened and then trimmed off to finish. Example of such product is Sika Boom of Sika India.
This also acts as
thermal and electrical insulations. 1 cm thick Sika Boom has the insulation power equivalent to 40
cm concrete and 20 cm brick.
For sealing joints on roof, wall, expansion joints a new concept can be used which is to apply a
synthetic polymer based, UV resistant, tough sheet of 1 to 2 mm thick having width of 10 – 20 cm.
The sheet is bonded on the surface by an adhesive. One such very successful system is Sikadur
Combiflex of Sika India. It is very easy to apply and is effective for long time. This can be used
also to seal pipe entries into the building. The following figures will illustrate the matter.
Another chances of leakage are through the joints in the basement. To stop such leakage
conventionally water bars are used. The main drawback of water bars is to keep its profile straight
during construction. If it is not straight it cannot act as a barriers for water flow through the joint.
The new concept in this area is to use a sealant at the joint, which will expand in contact with green
concrete as well as water. This helps to keep the joint sealed for flow of water. A product in this
class is Sika Swell S2 of Sika India. It is PU resin based special sealant, which will expand in
presence of water. This is supplied in Cartridge. The following figures will illustrate its
Sika Swell S2
Sika Swell S2 is available in two triangular sections 15 and 20mm. 15 mm is used for structures
less than 30 cm thickness and 20mm is used for 30 – 50 cm thickness. Sika Swell S2 expands 100%
by volume in 7 days in contact with water.
New age sealing technology with single component PU sealants:
The usage of moisture curing , single component PU sealants are becoming fast popular over the
conventional type of two component , reaction curing sealants like Poly sulphide due to several
operational and performance related benefits.
Sealant History :
1940 1950 1960 1970 1980 1990 2000
S e a la n t M a r k e t to t a l W o r ld 2 0 0 0 (ttl / to n s )
4 3 %
1 7 %
For satisfactory performance a sealant in various joints must be:
Waterproof It must be an impermeable material
Durable Not adversely affected by aging weathering for a
reasonable service life.
Permanently elastic Sufficiently recover its original properties and
shape after cyclical deformations. Deform to
accommodate the movement occurring at the
Of high cohesive Must not tear easily.
Capable of adhering Must remain in intimate contact with the joint
well to concrete etc. faces.
Non toxic Be free of substances harmful to the user and
environment especially in treatment plants and
reservoirs where the water is for human
Sealant System Polyurethane Silicone Polysulfide Acrylic Modified PU-Hybrid
Practical Elongation in an
Expansion joint (based on
15 - 25 % 15 - 25 % 15 - 25 % 5 - 10 % 15 - 25 % 15 - 25 %
German Study Building Sealant
defects over a 20 year period)
60-80% >80% <80% <60% 30-70% >80%
Formulations No No Yes No No
-30o C -40o C -30o C -20o C -30o C -30o C
up to up to up to up to up to up to
+90o C +200o C 100o C 80o C +90o C +90o C
Tear Strength + - + + 0 +
Paintability + - + + +
Cure Speed 1K + + 0 0 + +
Skin Overtime + + + 0 + +
Tack free time + +/- + 0 + +
Adhesion + + 0 0 + +
Grindability + - - - 0 0
Staining + - 0 + + +
Primer Requirement + + 0 0 + +
Gunability + + 0 + + +
Storage Life + + - + 0 +
Weatherability 0 + 0 0 0 +
0 Depending on formulation and manufacturer
Considering the above facts and figures , lets us now look into the comparison on advantages of 1
– component products over 2 – component products :
Single component – no weighing and mixing at site, reduces chances of human error.
Time saving, easy, user friendly and cleaner application.
Uniformity of colour.
No need for expensive mixer / guns. Can be applied with light weight guns.
More friendly to environment / non toxic .
World wide moisture curing, singe component polyurethane ( PU ) products are well accepted as
the most suitable products for flexible sealing applications in various types of joints and cracks .
The following details will substantiate this :
Poly urethanes :
Reaction products of Isocyanates with polyols and other H-Donors.
The many possible permutations and combinations of commercially available raw materials result
in a spectrum of polyurethane sealants which range from high quality high performance sealants to
low quality low performance sealants of the one generic type. Thus, particular care must be
exercised when selecting a PU sealant that is cost effective in the long term.
Packaging: 1 and 2 Part systems
90% of the market 1 Part
US market > 50% 2 Part
•Cost / performance
•Primer less adhesion on many non porous
•Wide variety of products for multiplicity of applications.
• General purpose product.
•Bonds well to itself in joint repairs.
•Good abrasion and tear resistance
(good for floor joints).
•Perimeter joints (window and door frames). There is no single sealant type which works
best in all situations. Final choice will
depend on all aspects of specific project.
•Joints in pre cast concrete panelling.
•Concrete, quarry tile, floor and pavement joints.
•General use in structural and civil engineering.
•Water immersed joint.
Sealing operation has become an important and integral part of waterproofing of a
building construction and the pioneering technology with single component , flexible Poly
urethane sealants are the most widely used one word over.
This paper contains a few examples of different chemicals, which are very effective to get
permanent solutions for various problems in constructing buildings and structures. There are many
other chemicals, which can be used based on the requirement. Use of such chemicals increases the
durability and aesthetic of a building.