Transcript Presentation_Slides

Sewer Infrastructure
Rehabilitation
Kevin Morris
Market Director Water & Wastewater
Learning Objectives
• Causes of Deterioration of
Concrete in Municipal
Infrastructure
• Stopping Inflow & Infiltration
• Structural Rehabilitation Materials
• Chemical Resistant Coatings and
Linings
Causes of Deterioration
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Structural Fatigue
Corrosive Gases
Microbial Induced Corrosion (MIC)
Old Age
Causes of Deterioration
Structural Fatigue
• Caused by:
– Traffic Loading
– Freeze/Thaw Cycling
– Soil Movement
– Erosion or Cavitation
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)
Causes of Deterioration
Corrosive Gases
• Carbon Dioxide
– Slow deterioration of the substrate
– Naturally occurring
– Acts to reduce pH of the substrate
– Carbonated concrete
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.
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.
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
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
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)
Stopping Inflow & Infiltration
• Process
– Treated through trenchless
technology applications
– Utilizing polyurethane grout injection
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.
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.
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.
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**
Stopping Inflow & Infiltration
• Polyurethane Chemical Grouts
are broken in to two categories.
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–
1. Hydrophobic
2. Hydrophilic
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
Typical Problems
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.
Using Oakum
Apply
Oakum in
Joint
Soak Oakum
In Resin
Dip Oakum with
Resin in Water
Insertion of Wall Spear
Insertion of Ports
Shutting Off High Flow Leaks
Complete encapsulation
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
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.
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Relatively Inexpensive
Easily Located
Susceptible to MIC
Long cure times before topcoating
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
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
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*.
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*.
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*.
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.
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
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.
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
• “Hot Pot” Spray
Cons
• Rigid films
• Subject to Blush
• Exothermic Reaction
could cause
microfracturing
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.
Polyurethane Coatings &
Linings
Pros
• Flexibility of formulation
– Flexible
– Rigid
– Hand Applied Repair
Grades
• Improved elongation
• Fast cure times
• Abrasion Resistance
• High film builds
Cons
• Do not tolerate moisture
well during application or
initial cure
• Plural Component Spray
• May require a primer
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.
Polyurea/Hybrid Polyurea
Coatings & Linings
Pros
• Fast dry times
• High film builds
• Used for linings and
chimney seals
• Physical Toughness
– Excellent Abrasion
resistance
– Elongation
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
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
Spark Testing
Polyurethane Elastomer
Installation
For manhole rehab.
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.
Thank You