Municipal Infrastructure Lining and Rehabilitation

Presented by

Bruce Snyder

Business Development Manager

Water and Wastewater

Agenda

• Deterioration within the manhole structures

• Chemical Grouts for stopping inflow and infiltration

• Cementitious Liners

• Chemical resistant coatings

Causes of Deterioration in Manhole Structures

• Structural fatigue

• Acid attack (MIC)

• Corrosive gases (H2S)

• Old age

Why Accelerated Corrosion?

Prior to the Clean Water Act of 1972,

H2S concentrations were below 10 ppm

in most municipal systems. The result

was very gradual acid attack to concrete and

metals. As a result, thin film systems (<25m)

such as coal tar epoxy provided effective

protection for 10-15 years.

Following the amendment of the Clean

Water Act of 1980, industrial pretreatment of

wastewater effluent to eliminate or reduce

the presence of heavy metals (lead,

mercury, cadmium) was mandated. Prior to

1980, these metals killed or retarded the

growth of bacteria.

Why Accelerated Corrosion?

Consequently, H2S has risen to levels as high as several hundred ppm, averaging over 30 ppm in collection piping, manholes and tanks. H2SO4 concentrations have risen from solutions of 1.5% to as high as 7%, resulting in pH ranges found to be as low as 1.5-2.5, and often less than 1.0 !

Why Accelerated Corrosion?

Microbial Induced Concrete Corrosion

PHASE I

• Sulfur reducing bacteria (SRB) break down sulfates in the waste stream and produce hydrogen sulfide (H2 S) and carbon dioxide (CO2).

PHASE II

• 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) attach to the surface as

sulfates are produced.

Microbial Induced Concrete Corrosion

PHASE III

• 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

Why Stop Infiltration?

• 25-30% of infiltration and 70% of inflow in sanitary sewer collection systems comes from the manhole.

– Stops unnecessary treatment of ground water.

– Stops infiltration that is detrimental to a corrosion protection systems service life.

– Extends the life of the structure.

– Stops sink holes from occurring.

Chemical Grouts

• 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**

Polyurethane’s

Polyurethane Chemical Grouts are broken in to three categories.

1.Hydrophobic

2.Hydrophilic

3.Multi Component

Hydrophilic & Hydrophobic

Hydrophilic

• Flexible

• Resin only

• Great Bond

• Absorbs Water

• Medium to High Shrinkage

• Medium Expansion (brick)

• Foam or Gel

Hydrophobic

• Rigid and Flexible

• Resin + Catalyst

• Good Bond

• Repeals Water

• Low Shrinkage

• High Expansion

• Adjustable Set Times

• Foam

Manhole Rehabilitation Market

• Past – Cheap Fix - Temporary, i.e. Gunite, Patch & Go

• Present –Multitude of Technologies - Linings, PVC, etc.

• Future –Work will be done upfront – Long term

solutions, new construction to be lined prior to installation

Microsilica/Fumed Silica Mortars

Advantages

1. Tighter matrix – lower permeability

2. Chemical resistant

3. Drive water off faster than pure portland

4. Lower cost than Calcium Aluminate

Limitations

1. Susceptible to MIC

2. Longer overcoat time than Calcium Aluminate Mortar

Microsilica Application

Microsilica Application

Microsilica Application

Calcium Aluminate Mortars

Two types available in the market.

Pure Calcium Aluminate Mortar

Binder or paste are calcium aluminate as well as the aggregate.

Calcium Aluminate Mortar

Binder or paste are calcium aluminate and the aggregate is typically silicon dioxide (Silica Sand)

Calcium Aluminate Mortar

Advantages

1. With stands MIC longer than portland based materials

2. Faster set times (Typically 4-24 hours)

3. Can be used as a standalone liner

Limitations

1. Susceptible to MIC, but at a reduced rate.

2. Cost

Chemical Resistant Coatings

• Epoxy, Polyurethane and Polyurea

– Provide excellent infiltration barrier

– Longer useful life than cementitious coatings

100% Solids Epoxy Coating • An Amine Cured, Chemical Resistant, 100% Solids, Epoxy

Coating.

• Resistant to hydrogen sulfide gas, carbon dioxide gas and microbiologically induced corrosion by sulfuric acid formation.

• High Build Capabilities – Traditional installed at 60-125 mils DFT in one coat un reinforced and up to 250 mils with aggregate addition.

• Drawback of epoxy technology is the limited flexibility within the system

Polyurethane/Polyurea Coating • 100% solids polyurethane/polyurea coating have excellent

flexibility, impact, tear and abrasion resistance.

• Resistant to hydrogen sulfide gas, carbon dioxide gas and microbiologically induced corrosion and sulfuric acid formation.

• Fast cure and short downtime

• High Build Capabilities – Traditional installed at 80-125 mils DFT in one coat.

• Used as a total monolithic liner or chimney seal

• Drawback of polyurea/polyurethane technology is the sensitivity to moisture.

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

Questions? Bruce Snyder

Sherwin-Williams Company

11350 Alameda Dr

Strongsville, Ohio 44149

216.533.4472

440.846.1701 fax

bksnyder@sherwin.com

www.sherwin-williams.com/protective