1. Sewer Infrastructure Rehabilitation
Kevin Morris
Market Director Water & Wastewater

2. Learning Objectives
Causes of Deterioration of Concrete in Municipal Infrastructure
Stopping Inflow & Infiltration
Structural Rehabilitation Materials
Chemical Resistant Coatings and Linings

3. Causes of Deterioration
Structural Fatigue
Corrosive Gases
Microbial Induced Corrosion (MIC)
Old Age

4. Causes of Deterioration
Structural Fatigue
Caused by:
Traffic Loading
Freeze/Thaw Cycling
Soil Movement
Erosion or Cavitation

5. Causes of Deterioration
Corrosive Gases
Hydrogen Sulfide – H2S
Corrosive to metal and concrete
Reduces the pH level
Converts to sulfuric acid when it comes in contact with Sulfur Reducing Bacteria (SRB’s)

6. Causes of Deterioration
Corrosive Gases
Carbon Dioxide
Slow deterioration of the substrate
Naturally occurring
Acts to reduce pH of the substrate
Carbonated concrete

7. Causes of Deterioration
Microbial Induced Corrosion
(Four Phases)
Phase 1
Sulfur reducing bacteria (SRB) break down sulfates in the waste stream and produce hydrogen sulfide (H2 S) and carbon dioxide CO2.

8. Causes of Deterioration
Microbial Induced Corrosion
Phase 2
The acidic gases H2S and CO2 act to reduce the pH of concrete from approximately 12 to as low as 9.
Sulfur oxidizing bacteria (SOB’s) attach to the surface as sulfates are produced.

9. Causes of Deterioration
Microbial Induced Corrosion
Phase 3
The SOB’s are known as Thiobacillus Thioxidans. They consume H2S and discharge sulfuric acid H2SO4
The pH continues to drop and microbial growth accelerates creating more H2SO4

10. Causes of Deterioration
Microbial Induced Corrosion
Phase 4 – Final Phase
Acid attack of the concrete creates a layer of gypsum (calcium sulfate). As organisms reproduce additional acid is produced.
Eventual structural failure

12. Stopping Inflow & Infiltration
Purpose:
Lower the cost of wastewater being treated at the plant.
Lower the cost of equipment maintenance associated with abrasive soils in the waste stream.
Protect the environment for Sanitary Sewer Overflows (SSO’s) or Combined Sewer Overflows (Cso’s)

13. Stopping Inflow & Infiltration
Process
Treated through trenchless technology applications
Utilizing polyurethane grout injection

14. Stopping Inflow & Infiltration
Why should you use polyurethane grouts?
Lowest cost permanent repair procedure.
Little disruption to the community.
Grouting seals leaks and fills voids.
Can be performed in house or contracted out.

15. Stopping Inflow & Infiltration
Grouting is a Non Structural repair, if the manhole/pipe are in good sound condition grouting is all that is needed to seal leaks, fill voids, extend the structures life, lower repair costs.
Grouting, in many cases, may be needed to stop infiltration prior to the application of coatings and linings.

16. Stopping Inflow & Infiltration
Possible Applications
Leak Repairs
Manholes, Storm Sewers, Treatment Plant Tanks,Tunnels, Box Culverts, Dams, Seawalls & Pipe joints.
Stabilization
Manholes, Roadways, Seawalls , Pipe lines &Tank Slabs.

17. Stopping Inflow & Infiltration
Chemical Grouts are broken down into 4 basic categories.
1. Acrylamide
2. Acrylate
3. Acrylic
4. Polyurethane
**Acrylamide and Acrylate grouts are the primary chemical grouts used for
Mainline sewer grouting**

18. Stopping Inflow & Infiltration
Polyurethane Chemical Grouts are broken in to two categories.
1. Hydrophobic
2. Hydrophilic

19. Stopping Inflow & Infiltration
Hydrophilic Resins
Flexible
Resin only
Great Bond
Absorbs Water
Medium to High Shrinkage
Medium Expansion
Foam or Gel
Hydrophobic Resins
Rigid and Flexible
Resin + Catalyst
Good Bond
Repeals Water
Low Shrinkage
High Expansion
Adjustable Set Times
Foam

20. Typical Problems Grouting Leaks in main line pipes can
Here are four products designed to solve
problems in Manholes:
Polyurethane foam A flexible Polyurethane for cracks and pipe
penetration.
Hydrophobic: A Polyurethane capable of shutting off gushing leaks and f
filling voids.
Gel : A Polyurethane gel that will seal leaks and stop infiltration through
the walls.
OAKUM: A dry jute rope when soaked in Polyurethane is capable of
filling large cracks.
Grouting Leaks in main line pipes can
easily be accomplished using Acrylates
or Acrylamide grouts.

21. Using Oakum Apply Oakum in Joint Soak Oakum In Resin Dip Oakum with
Resin in Water

22. Insertion of Wall Spear

23. Insertion of Ports

24. Shutting Off High Flow Leaks

25. Complete encapsulation

26. Structural Rehabilitation Materials
Cementitious Repair Mortars
Portland Cement with Admixtures or Calcium Aluminates
Sprayed or trowel applied
New product mixes allow radial spray with no entry into manhole
Will degrade as the original surface did

27. Structural Rehabilitation Materials
Portland Cement
This is the most commonly used cement during the precasting and/or cast-in-place production of today’s wastewater components.
Relatively Inexpensive
Easily Located
Susceptible to MIC
Long cure times before topcoating

28. Structural Rehabilitation Materials
Microsilica Repair Mortars
Microsilica repair mortars utilize portland cement to create the cement paste but also contain a fumed silica admixture to create a more dense substrate.
Chemical Resistant / Lower Permeability
Can be used as a stand alone liner in a mild H2S environments.
Faster cure times for topcoating
Susceptible to MIC
Lower cost than Calcium Aluminate Mortars

29. Structural Rehabilitation Materials
Calcium Aluminate Repair Mortars
There are two common types of calcium aluminate mortar commercially available today.
Pure Calcium Aluminate Mortars
Where the aggregate is a coarsely ground version of the cement dust
Calcium Aluminate Mortars
Where the aggregate is silica sand

30. Structural Rehabilitation Materials
Calcium Aluminate Repair Mortars
Multiple manufacturers in the U.S.
The principle behind Calcium Aluminates is that they maintain a higher pH that prevents they colonization of the Thiobacillus bacteria.
The paste will erode exposing the chemically inert silica sand. Eventually the sand will fall out of the surface of the repair mortar*.

31. Structural Rehabilitation Materials
Calcium Aluminate Repair Mortars
Available from only 3 manufacturers in the U.S.
The principle behind Calcium Aluminates is that they maintain a higher pH that prevents they colonization of the Thiobacillus bacteria.
The paste will erode at the same rate as the aggregate*.

32. Structural Rehabilitation Materials
Pure or Fused Vs. Calcium Aluminate Mortars
In a test conducted in Germany to replicate an 8-year service life in a sewer system the weight loss difference between these 2 products was approximately 1%. Contributed to the previous statements marked with an*.

33. Structural Rehabilitation Materials
Calcium Aluminate Mortars
Offer an improved life cycle over other repair mortars
Fastest cure time for topcoating
Require humidity to properly cure
Susceptible to MIC but a reduced rate
Can be used as a stand alone liner in moderate H2S environments.

36. Chemical Resistant Coatings & Linings
Protect the surrounding environment
Provide a longer life cycle for the substrate they are protecting
Provide an excellent infiltration barrier
Available chemistries include:
Epoxy
Polyurethane
Polyurea

37. Chemical Resistant Coatings & Linings
Epoxy Coating and Linings
Epoxy coatings have been the industry standard since municipalities began lining manholes and provide performance properties that will satisfy the requirements of many rehabilitation projects. Epoxies are not the cure or fix for every situation and should be considered based on the structure, location, use, and environment during application.

38. Epoxy Coatings & Linings
Pros
Moisture tolerance
High film builds
High strength
Low/No Odor
Chemical Resistance
Variable formulations
Epoxy Resins
“Hot Pot” Spray
Plural Component Spray
Epoxy Mortars
Hand trowel
Cons
Rigid films
Subject to Blush
Exothermic Reaction could cause microfracturing

41. Chemical Resistant Coatings & Linings
Polyurethane Coating and Linings
Polyurethane chemistries have gained market acceptance over the last several years. This generic chemistry offers the greatest flexibility of formulation to fit the desired needs of the end user and excellent chemical resistance.

42. Polyurethane Coatings & Linings
Cons
Do not tolerate moisture well during application or initial cure
Plural Component Spray
May require a primer
Pros
Flexibility of formulation
Flexible
Rigid
Hand Applied Repair Grades
Improved elongation
Fast cure times
Abrasion Resistance
High film builds
Abrasion Resistance – 106 mg loss; Tensile Strength – 1,988 psi; 20% Sulfuric Acid – No Effect; Elongation 47% Recoverable

44. Chemical Resistant Coatings & Linings
Polyurea Coating and Linings
Polyurea or Hybrid Polyurea chemistries are the newest technologies to have gained market acceptance. This technology may be one of the most difficult for an end user to evaluate due to the formulation variances. These variances can effect performance and chemical resistance.

45. Polyurea/Hybrid Polyurea Coatings & Linings
Cons
Do not tolerate moisture well during application or initial cure
Plural Component direct impingement application
Chemical resistance
High tensile strength
Primer may be required
Pros
Fast dry times
High film builds
Used for linings and chimney seals
Physical Toughness
Excellent Abrasion resistance
Elongation
Abrasion Resistance – 6 mg loss; Tensile Strength – 3,000 psi; Elongation – 425 psi; Tear Strength 495 pli; 20% Sulfuric Acid – No Effect
Application – Only suitable for large structures unless applied through ROI equipment

46. Inspection and Holiday Inspection
Required to test liner for discontinuity
Moisture in substrate sufficient for reading
High Voltage – > 20.0 DFT
100 volts per dry mil

47. Polyurethane Elastomer Installation
Spark Testing
Polyurethane Elastomer Installation
For manhole rehab.
This photo shows the tester grounded to the cast and moving the wire brush across the surface looking for pinholes or holidays. If a pinhole or holiday is present a spark will appear. These areas are then marked for repair.

48. Summary
There are numerous products and methods available for the lining and rehabilitation of sewer infrastructure.
Physical performance characteristics vary greatly across the numerous chemistries.
Products should be selected based on the needs of the end user.
Uniform monolithic films aid in prevention of chemical attack.

49. Thank You