This document discusses permeability reducing admixtures (PRAs) that can be added to concrete to improve its waterproofing properties. It describes how PRAs work by reducing the size, number and connectivity of pores to limit water penetration. The main types are hydrophobic, finely divided solids, and crystalline materials. Test results show crystalline PRAs can reduce permeability by up to 70%. PRAs should be used for structures exposed to moisture or hydrostatic pressure. Dosage depends on the type but is typically 2-5% by weight. Successful projects using PRAs are mentioned.

1. Admixtures For Water
Proofing In concrete
Submitted By:
Sanjipta Behera
Civil Engineering
Roll no-13011521
Sem-7th , Sec-B2

2. Contents
1. Introduction
2. Damages to structure
3. Permeability Reducing Admixtures(PRAs)
4. Functions of Water Proofing Admixtures
5. Types of materials used in PRAs
6. Reduction of permeability using PRAs
7. Comparison of reduction of permeability
8. When to use PRAs
9. Dosage of PRAs
10. Application procedure
11. Quality assurance
12. Successful projects
13. Conclusion

3. Introduction
 Permeability is one of the main factors that can affect the
durability of the structure.
 Permeable structures can result for various reasons such as low
cement content, poor compaction too much water during concrete
mixing etc.
 The passage of water through cracks ,joints, voids, and inter
connected capillaries in the mass concrete makes the concrete
pervious, ultimately leads to poor protection of structures,
increases the rate of alkali aggregate reaction and also accelerates
the rate of corrosion in the steel.

4. Introduction (cont.)
 The impervious property of concrete can be improved by addition
of admixture in the green concrete or by surface treatments and
the phenomenon is generally known as waterproofing.
 The products used in both the stages of concrete are known as
construction chemicals or admixtures and waterproofing is one of
the aspects in construction aid.
 These products are required for modifying the properties of
concrete or mortar to make them more suitable for the work at
hand or for the economy for such purposes are saving energy

5. Damages to Structure

6. Permeability Reducing Admixtures(PRAs)
So to counteract these problems there is a need of an admixture
which can control the porosity of concrete. These admixtures are
known as permeability-reducing admixtures (PRAs) .
There are two broad classifications depending on concrete exposure
1.concrete exposed to non hydrostatic conditions (PRAN)
2.concrete exposed to hydrostatic conditions (PRAH)

7. Functions of Water Proofing Admixtures
A permeability reducing concrete admixture or waterproofing
admixtures function in following ways:
 It reduces the size of capillary pores, their numbers and continuity
inside the concrete structure.
 It blocks the capillary pores of concrete
 It may line the capillary pores with hydrophobic materials. This
prevents the absorption of water in the pores due to capillary
absorption.
 Besides reducing permeability, some PRAs impart other
beneficial characteristics, such as reduced drying shrinkage,
reduced chloride-ion penetration, improved freeze/thaw
resistance.

8. Types of materials used in PRAs
According to American Concrete Institute (ACI) Committee 212
the materials used to produce PRAs vary, but they generally fall into
three categories.
1.The largest category consists of hydrophobic, or water-repellent,
chemicals derived from soaps or fatty acids, vegetable oils, and
petroleum.
 These materials form a water-repellent layer along pores in the
concrete, but the pores themselves remain open.
2.The second category is finely divided solids—either inert or
chemically active fillers such as talc, clay, siliceous powders,
hydrocarbon resins, and coal-tar pitches.
 These materials densify the concrete and physically limit the passage
of water through the pores. Some experts also consider supplementary
cementitious materials (SCMs) to be in this category.

9. Types of materials used in PRAs(cont.)
3.The third category consists of crystalline products—proprietary
active chemicals in a carrier of cement and sand.
 These are hydrophilic materials that increase the density of
calcium silicate hydrate or generate crystalline deposits that block
concrete pores to resist water penetration.
The various types of materials can be used alone or in combination
to give different levels of performance.

10. Reduction of permeability using PRAs
 According to the ACI report, concrete produced with hydrophobic
chemical admixtures could theoretically resist some hydrostatic
pressure. It reduces the permeability upto 49%.
 The hydrophilic crystalline admixtures provide the concrete with
the greatest resistance to infiltration of water under hydrostatic
pressure. It reduces permeability upto 70%.
 The colloidal silica is very less effective in reduction of
permeability. It reduces permeability upto 19%.

11. Comparison of reduction of permeability
Given below the table reproduced from ACI 212.3, summarizes
results from a series of permeability tests performed on concrete
mixes with three different types of PRAs
Admixture type Coefficient of
permeability
of reference
concrete
Coefficient of
permeability of
test concrete
Percent
reduction in
permeability
Crystalline 4.29×10−14 1.28×10−14 70
Colloidal silica 1.98×10−13
1.61×10−13
19
Hydrophobic pore
blocker
2.23×10−12 1.14×10−12 49

12. When to use PRAs
The value of a PRA depends entirely on the environment the
concrete will be exposed to and the importance of keeping water
from passing through.
 For interior columns, beams, and floor slabs in a high-rise,
permeability isn’t a big issue.
 For structures that will be exposed to moisture, salt or salt water,
wicking, or water under hydrostatic pressure, using a PRA can
help prevent problems such as water migration, leaks, freeze/thaw
damage, corrosion, carbonation, and efflorescence.

13. When to use PRAs(cont.)
 PRANs are often used in architectural concrete, precast panels,
and concrete brick, block, and pavers to repel rain and minimize
dampness. Reducing permeability can help minimize
efflorescence and make it easier to keep walls clean.
 PRAHs are needed for more extreme and continuous exposures,
such as below-grade structures, tunnels and subways, water tanks
and pools, bridges, and dams. Manufacturers of the crystalline
PRAHs say the products can eliminate the need for membrane
waterproofing systems and epoxy-coated reinforcement, thereby
reducing the cost of waterproofing.

14. Dosage of PRAs.
Like other admixtures, PRAs are typically specified by the architect
or engineer and added to the concrete at the ready-mix plant.
Dosage of these admixtures vary depending on the type of admixture
and the level of performance required.
 Hydrophobic type- 2% of weight of concrete.
 Colloidal silica- 5% by weight of concrete.
 Crystalline PRAH-2% by weight of cementious material.

15. Application procedure:
1.The part of the structure where water proofing is to be done is
determined. So more importance is given to that part which is more
exposed to water.
2.Water cement ratio is fixed properly as more water or less cement
is vulnerable to permeability. Cement is provided as per the ratio.
3.Fine and coarse aggregates are added as per the mixed design.
4.Admixure of specified dosage is added.
5.Water is added as per the mixed design.
6.Mixing is done with the help of machine.
7.After mixing the concrete is applied at the desired location.

16. Quality assurance:
1. Waterproofing admixture to be certified by the International Code
Council (ICC) as a Chemical Admixture Used in Concrete
(AC198).
2. Waterproofing admixture must be certified to NSF/ANSI
Standard 61.
3. Waterproofing admixture shall hold a valid agreement certificate
from the British Board of Agreement.

17. Successful projects
1. Waterproofing admixture was used in the renovation and
expansion of the Mark Jefferson Science Complex at Eastern
Michigan University in Ypsilanti.
2. South Cobb Tunnel Lift Station near Atlanta.
3. Gardens by the Bay, Marina Bay, Singapore.
4. National Road Bikeway Tunnel near St. Clairsville.
5. Singapore international airport terminal 3.

18. Drawbacks
Besides having so many benefits PRAs has some drawbacks
1. It will not form membrane on cracks larger than half a
millimeter.
2. Joints, penetrations, and transitions will need attention as well.
In some instances, such as basements of single family homes, a
contractor may still need to provide an adequate drainage system
to avoid water buildup through the life of the structure.

19. Conclusion
There are many products in the market now a day which are
available to protect the concrete structure from damage due to water
penetration. For example, coatings, sealers, membranes etc. are used
to prevent water penetration. But all these require huge amount of
money and time. These process can be simplified by the use of water
resisting admixture which prevent the ingress of water through
concrete by making it waterproof.
For projects and applications that need waterproof concrete, the use
of PRAs is worth considering. Contractors need only follow sound
placement and finishing practices to install it successfully, and
owners may be able to cover the costs by saving the labor and
materials required for other waterproofing methods.

20. References
1. http://www.kryton.com/products/krystol-internal-membrane-
kim/attachment/concrete-waterproof_admixture_csi_kim/
2. http://www.concreteconstruction.net/how-
to/materials/waterproofing-admixtures-for-concrete_o
3. www.penetron.com/doc/pdf/PRANvsPRAH_ThePenetronDiffere
nce.
4. http://theconstructor.org/concrete/waterproofing-admixtures-
concrete/11110/

22. Questions