Pudlo is a concrete admixture that modifies the microstructure of concrete to improve its durability. It reduces permeability, absorption, and diffusion by densifying the cement paste and reducing porosity and pore size. This makes concrete virtually water-tight and prevents ingress of chloride ions, carbon dioxide, water and other chemicals that can cause corrosion of steel reinforcement or chemical attacks on concrete. Pudlo also autogenously heals microcracks to further improve concrete's resistance to permeation and durability against various degradation mechanisms like corrosion, sulfate attack, and acid attack. Case studies and third party testing show that Pudlo modified concrete outperforms standard concrete in real world exposure conditions and infrastructure projects.

1. Concrete durability and water resistance
Abu Saleh Mohammod PhD, MICT
General Manager
Pudlo Middle East Building Materials L.L.C
www.pudlo.com

2. Content
• Permeation properties of concrete
• Pudlo modified durable concrete
• Attacks on concrete durability
• Case studies

3. Permeation Properties

4. Permeation and transportation mechanisms
In nearly all chemical and physical processes influencing durability of
concrete structures, two factors are dominant:
1. Transport within the pore structure and cracks
2. Movement of water (often containing dissolved salts or gasses)
Permeation of water and gasses can be divided into three distinct
phenomena:
• Permeability
• Absorption
• Diffusion
Many factors influence these phenomena both internally and externally

5. Permeability
P1
P2
The flow property of concrete which
quantitatively characterises the ease
by which a fluid will pass through it,
under a pressure differential
Fluid movement
Typically affects: dams, tunnel linings, liquid retaining structures,
submerged offshore structures
Concrete

6. Permeability – influencing factors
Permeability = ƒ {pressure gradient, capillary pore size, pore interconnection}
Permeability
Capillary size and
interconnectivity
Environmental
Conditions
Water/cement
ratio
Aggregate type
Hydrate structure
Cement type
Primary parameter
Secondary parameter
Pressure gradient

7. Absorption
Absorption = ƒ{moisture gradient, capillary pore size, pore interconnection}
Typically affects: Structures subjected to cyclic wetting and drying
eg marine structures in the tidal zone
The process by which concrete takes in
liquid, normally water or aqueous solution
by capillary action. Sorptivity is the rate at
which water enters the concrete
Water reservoir
Concrete

8. Absorption – Influencing Factors
Capillary size and
interconnectivity
Environmental
Conditions
Water/cement
ratio
Aggregate type
Hydrate structure
Cement type
Primary parameter
Secondary parameter
Moisture gradient
Pore fluid content
Degree of
saturation
Absorption = {moisture gradient, capillary pore size, pore interconnection}
Absorption

9. Diffusion
Diffusion = ƒ {concentration gradient, capillary pore size, pore interconnection,
degree of reactivity of substrate}
Typically affects: Foundation elements , Highway structures
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
C1 C2
The process by which a vapour, gas or ion
can pass through concrete under the action
of a concentration gradient

10. Diffusion – Influencing Factors
Capillary size and
interconnectivity
Environmental
Conditions
Water/cement
ratio
Aggregate type
Hydrate chemistry
Cement type
Primary parameter
Secondary parameter
Ionic concentration
gradient
Pore fluid chemistry
Curing conditions
Diffusion = ƒ {concentration gradient, capillary pore size, pore
interconnection, degree of reactivity of substrate}
Diffusion

11. Pudlo Modified Durable Concrete

12. • PUDLO developed late 19th Century
• Global Brand by 1925 (exported to 79 countries)
• Technical Manuals produced in over 15 languages
• By 1940 a verb in the English Language “PUDLO it”
Brief History

14. The Pudlo System
What is PUDLO?
A hydrophobic and micro pore blocking admixture which
additionally alters the microstructure of concrete to stop
water and moisture transport mechanisms, thus increasing
the long term durability of concrete

15. The benefits of watertight, impermeable, corrosion-resistant concrete.
Reducing the passage of water & air within concrete will reduce primary corrosion mechanism.
Comparison between control concrete and PUDLO modified concrete
Porosity highlighted in red scale

16. 100 times magnification – low w/c ratio concrete

17. 350 times magnification – low w/c ratio Pudlo modified concrete

18. Cement Particle Hydration Process Providing Autogenous Healing
Within The Cement Paste Matrix
Within standard concrete
the development of the
hydration process
typically takes place over
a period of one to two
weeks
Although the process
alone does not eliminate
the presence of voids
within the concrete
matrix
Pudlo blocks the pores
by densifying the
cement matrix to
eliminate the voids

19. Hydrophobic
characteristics of
Pudlo modified
durable concrete

20. Pudlo CWP is a proprietary concrete admixture designed to
enhance the permeation properties of concrete by modifying the
microstructure of cement paste, porosity and pore structure.
Effect of Pudlo on the Permeation properties

21. • The unique properties of Pudlo densify the cement paste by
reducing the porosity and pore sizes
• It increases the tortuosity of capillary pores by both physical
filling of voids and increasing the mass of hydrates
• This enhanced microstructure reduces the permeability and
diffusion properties of concrete
Effect of Pudlo on the Permeation properties

22. • It also significantly reduces the absorption of concrete by
providing hydrophobic lining along the pore walls, thus reducing
capillary suction of pores
• By enhancing the permeation properties and reducing the
permeability, absorption and diffusion of concrete, Pudlo makes
the concrete virtually water-tight, the key factors for durability in
concrete structures
Effect of Pudlo on the Permeation properties

23. Steel Reinforcement & Pudlo
BS EN 1992 Pt 1 (was BS 8110)
vs
BS EN 1992 Pt 3 (was BS 8007)
• No practical difference between a
0.2mm and a 0.3mm crack width
• Reduction of up to 30%
reinforcement steel
(CIRIA 139)
Autogenous Healing

24. PUDLO BBA Approval Certificate
Pudlo is BBA Approved

25. Attacks on concrete durability

26. Type of attacks on concrete durability
Corrosion of reinforcement bar by:
Chloride ingress
Carbonation
Sulfate attack
Delayed Ettringite Formation (DEF)
Physical salt weathering
Acid attack
Alkali Silica reaction
Multi-aggressive sea water attack

27. Corrosion

28. Corrosion of steel
• Corrosion of steel is an electro-chemical process, which starts once the
passive oxide layer of steel bar embedded in concrete is broken down,
creating microcells of anode and cathode.
• The passivating layer which is maintained due to rich alkaline environment
of concrete pore solution could be broken down mainly due to the
ingression of chloride ions or carbonation.
• At anode, once the passivating layer is broken down, dissolution of steel is
taken place producing positive iron ions and negative electros into the
solution.

29. Corrosion of steel
• At the cathode the liberated negative electrons combine with water and
oxygen to form negative hydroxyl ion.
• These hydroxyl ions then travel to the anode to add with positive iron ions
to form ferric oxide Fe2O3.H2O or rust.
• The volume of rust is three to six times more than the original volume of
steel.
• Thus the formation of rust resulting into an expansive pressure to the
concrete.
• Concrete cracks when this pressure exceeds the tensile strength capacity of
concrete.

30. Schematic diagram of corrosion

31. Corrosion of steel and permeation properties
• Corrosion of steel in concrete is directly related to the permeation
properties of concrete which would include permeability, absorption and
diffusion characteristics of the concrete cover.
• Water the main factors required to initiate corrosion can permeate through
concrete by all of these three mechanism whereas O2, CO2 and Cl
-
ions
diffuse through concrete cover to reach the steel surface.
• Therefore, it is utmost important to enhance the permeation properties of
concrete cover by reducing the permeability, absorption and diffusion
parameters of concrete.

32. How Pudlo resist corrosion
• By enhancing the permeation properties and reducing the permeability,
absorption and diffusion of concrete, Pudlo makes the concrete virtually
water-tight, the key factors for steel corrosion in concrete structures.
• Reduced diffusion translates into prolonged initiation period to corrosion,
as chloride ions take much longer time to reach the chloride threshold level
required to breakdown the oxide passivation layer of the steel
reinforcement bar.
• As there is virtually no presence of moisture, therefore possibility of
corrosion initiation in Pudlo modified concrete is almost nil.

33. Sulfate attack

34. Sulfate Attack of Concrete
Solid salts, such as sulfates, will not directly attack concrete however, when in solution, they
can react with certain components of the cement paste leading to expansion, cracking and
spalling of concrete.
The most common forms of sulfate are:
Sodium sulfate Na2SO4
Potassium sulfate K2SO4
Magnesium sulfate MgSO4
Calcium sulfate CaSO4
The above sulfates are common in natural groundwater conditions and may exist singly or in
combinations.
Sulfates may also be present from unnatural sources such as fertilizers (ammonium sulfate) or
contaminants in soils such as industrial effluent.

35. Mechanism of Sulfate Attack
Conversion of
C3A (if present)
and expansion
Hydrated
C3A
Sulfate solution
from the
environment
Diffusion of
sulfates into
concrete
Crack
formation
Sulfate attack is characterised by the
chemical reaction between sulfate ions
with the aluminate component, calcium
and hydroxyl of hardened Portland cement.
The reaction leads to the formation of
expansive ettringite and to a lesser extent,
gypsum
The reaction, providing there is enough water
present, will cause expansion leading to
cracking. This in turn will allow further ingress
of sulfates and accelerate the degradation
process.

36. Mechanism of Sulfate Attack
Sulfate attack is easily recognisable as a map
cracking on the surface, expansion of the
concrete and the appearance of a ‘soft’ white
substance.
Continued attack from sulfate solutions and
the presence of water will eventually lead to
complete disintegration of the concrete
The picture here shows a column which has
undergone sulfate attack. Concrete is easily
removed by hand using a chisel.

37. Mechanism of Sulfate Attack
Sulfates will attack some or all of the three main hydrate components of hardened concrete:
Calcium hydroxide Ca(OH)2
Calcium aluminate hydrate CaO.Al2O3.H2O
Calcium silicate hydrate CaO.SiO2.H2O
depending on the type of sulfate in solution involved.
Attack of Ca(OH)2 components
Sulfates will attack the calcium hydroxide component in an ‘acid’ type attack, producing
crystalline calcium sulfates (gypsum) and soluble hydroxide : eg
Ca(OH)2 + Na2SO4.10H2O CaSO4.2H2O + 2NaOH + 8H2O
gypsum soluble hydroxide

38. Mechanism of Sulfate Attack
Attack of calcium aluminate hydrate (CaO.Al2O3.H2O) components
Sulfates will also attack the calcium aluminate hydrate component, producing calcium sulfoaluminate
(ettringite), and expansive product and soluble hydroxides: eg
2(3CaO.Al2O3.12H2O) + 3(Na2SO4.10H2O) 3CaO.Al2O3.3CaSO4.31H2O + 2Al(OH)3 + 6NaOH + 17H2O
ettringite soluble hydroxides
Attack of calcium silicate hydrate (CaO.SiO2.H2O) components
Certain sulfates such as magnesium sulfate will also attack the calcium silicate hydrate as well as the
calcium aluminate hydrate and calcium hydroxide, producing very severe sulfate attack. and
expansive product and soluble hydroxides: eg
3CaO.2SiO2.aq + MgSO4.7H2O CaSO4.2H2O + Mg(OH)2 + SiO2.aq
low solubility hydroxide
The low solubility of the hydroxide means that the reaction proceeds until completion resulting in complete destruction of C‐S H

39. Factors Influencing Sulfate Attack
The main parameters which influence sulfate attack are:
1. Type of sulfate: Magnesium sulfate tends to be severely detrimental due to its
combined attack on C‐S‐H, Ca(OH)2 and C3A. Other sulfates such as sodium
sulfate and calcium sulfate attack single hydrate components.
2. Concentration. Higher concentrations of sulfates will increase the rate of attack.
Concentrations are expressed as g/l and sulfate contents classified accordingly.
3. Permeation properties of concrete. Sulfates enter concrete in solution by a
combination of absorption, permeability and diffusion. The interconnectivity
and pore size distribution will influence the ability for sulfates to enter the
concrete.

40. Factors Influencing Sulfate Attack
4. Cement Type: As sulfates attack the C3A, C‐S‐H and Ca(OH)2, the cement type
used will play an important part. Cements with low C3A contents will resist
sulfate attack due to the lack of this component.
5. Mobility Rate: The rate at which sulfates become available is important. e.g. a
clay soil may have a high sulfate content however, because of it’s low
permeability, the rate at which the sulfate diffuse through the soil is very slow.
6. Section size: The size of concrete section is vital. e.g. 20mm sulfate attack on a
1.2m wide section is less of a problem than 20mm sulfate attack on a 200mm
width section.
7. Environment: High temperatures will increase the rate of reaction between the
sulfates in solution and concrete hydration products.

41. • Sulfate ions enter into the concrete matrix as solution of ground water
• Pudlo makes the concrete virtually watertight by significantly reducing its
permeability and absorption properties
• Therefore concrete elements treated with Pudlo remain protected against
any form of sulfate attack
How Pudlo minimise the Effects of Sulfate Attack

42. Minimising the Effects of Sulfate Attack
Sulfate attack may be combated by the following:
• Use of supplementary cementitious materials. These materials have proved to be very
resistant to sulfates in field trials. Pozzolanic materials will reduce the interconnected
porosity of the concrete minimising ingress of sulfate bearing solutions. Pozzolanic
materials also react with Ca(OH)2, reducing the risk of attack on this particular hydrate
component.
• Use of Sulfate Resisting Portland Cement (SRPC). SRPC has a limited C3A content
compared to conventional PC to prevent attack of this hydrate component. C3A content is
limited to 3.5% by mass in BS 4027: 1996
• Appropriate mix design. Current standards (BS8500, EN206 & BRE SD 1) classify severity
of sulfate attack depending on sulfate concentration, ground permeability and ionic
mobility and provide guidance on mix design against sulfate attack.
• Provide physical barrier against sulfates. Surface coating of bitumen will provide
physical barrier against mobile sulfates from surrounding environment

43. Delayed Ettringite Formation (DEF)

44. Delayed Ettringite Formation (DEF)
• Delayed Ettringite Formation (DEF) which is associated with high
concrete temperature could be a cause of concern in the Arab
Peninsula due to the high ambient temperature during summer
• As a part of the hydration process, ettringite, C6AS3H32 is normal to
produce at the early stage due to the reaction of C3A with gypsum
• However, if the concrete temperature exceeds 70°C, the early
formation of ettringite does not occur
• The formation of ettringite could be delayed, generally after hardening
in the prolonged presence of water when the temperature cooled
down
• As the volume of ettringite is larger than its original hydration product,
it would produce internal stress, and induce cracks

45. Factors responsible for DEF
• The most common factors of DEF in Portland cement
are:
• elevated temperature
• prolonged exposure to water
• Other factors:
i) Composition of concrete
ii) Aggregate type
iii) Aggregate paste bond
iv) Cement type and chemical composition of cement
v) Exposure condition
vi) Presence of high sulfate and alkali content in the original
mix is also contributed to the DEF

46. Combatting DEF
• Controlling the concrete temperature during hydration is one of the key factor to combat DEF
• Use of high volume GGBS to reduce the heat of hydration of mass concrete is an important step
• Use of pozzolanic materials or reduced C3A content cement may have good resistance against the
formation of DEF
• As water is a requirement to DEF, enhancement of permeation properties of concrete is important. Use
of Pudlo in combination with GGBS would provide highly impermeable and low heat concrete

47. Salt Weathering or Physical Salt Attack

48. Salt Weathering
• Salts, particularly sulfate, from the underground water can rise up through the concrete structure by capillary or
by diffusion
• In the surface the moisture will dry up depositing salts in the concrete pore near the surface
• The deposition of salt crystal will exert pressure on the concrete pore wall due to expansive volume of
crystalline salts, creating tensile stress, causing cracks and erosion

49. Salt Weathering
• The mechanism of physical salt weathering is similar to freezing and thawing of water in concrete in that salts
(usually salts of sulfates and possibly chlorides) crystallise in the pores of concrete close to its surface. The
crystal growth exerts pressure and this can disrupt the concrete.
• Salt in solution from groundwater or damp soil can be transported by capillary action vertically through a
concrete member
• Above ground level, the moisture is drawn to the surface and evaporates, leaving crystals of salt growing in the
near surface pores
• This results in an area of deterioration just above ground level
• This form of attack is common in hot, dry areas and may also occur in marine structures

50. Combatting Salt Weathering
• Salt weathering is more pronounce on porous structure by capillary rise mechanism
• Reduction of porosity by densifying the concrete microstructure will improve the concrete’s ability to resist salt
weathering
• Enhancing permeation properties by means of lower absorption of concrete will also reduce the effect of salt
weathering
• Pudlo CWP densify the concrete matrix by producing more C‐S‐H
• Pudlo also reduce the absorption of concrete by creating a hydrophobic lining on the concrete pore walls, thus
Pudlo treated concrete effectively resist the deterioration of salt weathering

51. Case studies

52. Maple Lodge Sewage treatment work
• More than 70 years old
• No coating
• The works is a fully nitrifying diffused-air activated sludge plant
with heated anaerobic sludge digestion
• published data on the PH level of the raw water ranges from 4.5 to 8

53. Maple Lodge Sewage Treatment Works

54. Construction began 1938 as above and
after 70 years continuous wet/dry use
no sign of corrosion
Maple Lodge Sewage Treatment Works

55. 1950’s
Maple Lodge Sewage Treatment Works

56. 1952 2007
Maple Lodge Sewage Treatment Works

57. Southwark’s Integrated Waste Management Facility
• Chemical leachate
• High temperature up to 85 deg C
• No coating
• Extreme chemical environment
• Beside chemical resistant Pudlo provided
higher initial and final compressive
strength in high volume GGBS concrete

58. London borough waste and recycling centre
• Resistance to the chemical residues -
mostly acidic -leached by the waste.
• Floor needed to withstand
substantial wear and tear from heavy
vehicles and plant
• Pudlo modified durable concrete
with the addition of steel and PPE
fibres provided the solution

59. Examples of Truly Durable Structures
London Zoo Reptile
House
Designed and built in 1926-27
by Joan Beauchamp Proctor
and Sir Edward Guy Dawber,
the reptile house opened in
1929.

60. Examples of Truly Durable Structures
1931 2006

61. Durable concrete for iconic deep structures ...

63. Great Finish!
Building Design Partnership / Taylor Woodrow

64. … even in the most hostile environments such as
Middle East more than 100 projects
Holford Associates / RJ Crockers Partnershipge

65. Burj Khalifa Fountains
• Fountain rises to a height of 500ft, equivalent of a 50 storey building
• Over 6,600 lights and 50
colour projectors create a
visual spectrum of over
1,000 different water
• expressions

66. Burj Khalifa Fountains
• 900ft (275m) in length
located on the 35 acre
Dubai Lake
• 22,000 gallons of water
airborne at anytime
• 2½ kilometres of under-
ground tunnels

67. Burj Dubai Man-Made Lake

68. Lightweight, durable, corrosion resistant concrete
Building Design Partnership / Galliford Try

70. Merchant
Square
12 metre deep
London basement,
adjoining
The Paddington Basin

71. Merchant Square

72. Merchant Square

73. Pudlo modified
concrete used in
the lift shaft.
Central London
Green Park
Underground
Station
Lift shaft and associated
tunnels designed to
provide step free access.
Constructed close to
existing infrastructure.
Rail Projects

75. Thank you