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, H 2 S 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.
Why Accelerated Corrosion? 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, H 2 S has risen to levels as high as several hundred ppm, averaging over 30 ppm in collection piping, manholes and tanks. H 2 SO 4 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!
PHASE I Microbial Induced Concrete Corrosion Sulfur reducing bacteria (SRB) break down sulfates in the waste stream and produce hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ). PHASE II The acidic gases H 2 S and CO 2 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.
PHASE III Microbial Induced Concrete Corrosion The SOB s are known as Thiobacillus Thioxidans. They consume H 2 S and discharge sulfuric acid H 2 SO 4 The ph continues to drop and microbial growth accelerates creating more H 2 SO 4
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