Presentation on theme: "Sewer Infrastructure Rehabilitation"— Presentation transcript:
1 Sewer Infrastructure Rehabilitation Kevin MorrisMarket Director Water & Wastewater
2 Learning ObjectivesCauses of Deterioration of Concrete in Municipal InfrastructureStopping Inflow & InfiltrationStructural Rehabilitation MaterialsChemical Resistant Coatings and Linings
3 Causes of Deterioration Structural FatigueCorrosive GasesMicrobial Induced Corrosion (MIC)Old Age
4 Causes of Deterioration Structural FatigueCaused by:Traffic LoadingFreeze/Thaw CyclingSoil MovementErosion or Cavitation
5 Causes of Deterioration Corrosive GasesHydrogen Sulfide – H2SCorrosive to metal and concreteReduces the pH levelConverts to sulfuric acid when it comes in contact with Sulfur Reducing Bacteria (SRB’s)
6 Causes of Deterioration Corrosive GasesCarbon DioxideSlow deterioration of the substrateNaturally occurringActs to reduce pH of the substrateCarbonated concrete
7 Causes of Deterioration Microbial Induced Corrosion(Four Phases)Phase 1Sulfur 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 CorrosionPhase 2The 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 CorrosionPhase 3The SOB’s are known as Thiobacillus Thioxidans. They consume H2S and discharge sulfuric acid H2SO4The pH continues to drop and microbial growth accelerates creating more H2SO4
10 Causes of Deterioration Microbial Induced CorrosionPhase 4 – Final PhaseAcid 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)
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.
17 Stopping Inflow & Infiltration Chemical Grouts are broken down into 4 basic categories.1. Acrylamide2. Acrylate3. Acrylic4. Polyurethane**Acrylamide and Acrylate grouts are the primary chemical grouts used forMainline sewer grouting**
18 Stopping Inflow & Infiltration Polyurethane Chemical Grouts are broken in to two categories.1. Hydrophobic2. Hydrophilic
19 Stopping Inflow & Infiltration Hydrophilic ResinsFlexibleResin onlyGreat BondAbsorbs WaterMedium to High ShrinkageMedium ExpansionFoam or GelHydrophobic ResinsRigid and FlexibleResin + CatalystGood BondRepeals WaterLow ShrinkageHigh ExpansionAdjustable Set TimesFoam
20 Typical Problems Grouting Leaks in main line pipes can Here are four products designed to solveproblems in Manholes:Polyurethane foam A flexible Polyurethane for cracks and pipepenetration.Hydrophobic: A Polyurethane capable of shutting off gushing leaks and ffilling voids.Gel : A Polyurethane gel that will seal leaks and stop infiltration throughthe walls.OAKUM: A dry jute rope when soaked in Polyurethane is capable offilling large cracks.Grouting Leaks in main line pipes caneasily be accomplished using Acrylatesor Acrylamide grouts.
21 Using Oakum Apply Oakum in Joint Soak Oakum In Resin Dip Oakum with Resin in Water
26 Structural Rehabilitation Materials Cementitious Repair MortarsPortland Cement with Admixtures or Calcium AluminatesSprayed or trowel appliedNew product mixes allow radial spray with no entry into manholeWill degrade as the original surface did
27 Structural Rehabilitation Materials Portland CementThis is the most commonly used cement during the precasting and/or cast-in-place production of today’s wastewater components.Relatively InexpensiveEasily LocatedSusceptible to MICLong cure times before topcoating
28 Structural Rehabilitation Materials Microsilica Repair MortarsMicrosilica 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 PermeabilityCan be used as a stand alone liner in a mild H2S environments.Faster cure times for topcoatingSusceptible to MICLower cost than Calcium Aluminate Mortars
29 Structural Rehabilitation Materials Calcium Aluminate Repair MortarsThere are two common types of calcium aluminate mortar commercially available today.Pure Calcium Aluminate MortarsWhere the aggregate is a coarsely ground version of the cement dustCalcium Aluminate MortarsWhere the aggregate is silica sand
30 Structural Rehabilitation Materials Calcium Aluminate Repair MortarsMultiple 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 MortarsAvailable 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 MortarsIn 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 MortarsOffer an improved life cycle over other repair mortarsFastest cure time for topcoatingRequire humidity to properly cureSusceptible to MIC but a reduced rateCan be used as a stand alone liner in moderate H2S environments.
36 Chemical Resistant Coatings & Linings Protect the surrounding environmentProvide a longer life cycle for the substrate they are protectingProvide an excellent infiltration barrierAvailable chemistries include:EpoxyPolyurethanePolyurea
37 Chemical Resistant Coatings & Linings Epoxy Coating and LiningsEpoxy 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 ProsMoisture toleranceHigh film buildsHigh strengthLow/No OdorChemical ResistanceVariable formulationsEpoxy Resins“Hot Pot” SprayPlural Component SprayEpoxy MortarsHand trowelConsRigid filmsSubject to BlushExothermic Reaction could cause microfracturing
41 Chemical Resistant Coatings & Linings Polyurethane Coating and LiningsPolyurethane 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 ConsDo not tolerate moisture well during application or initial curePlural Component SprayMay require a primerProsFlexibility of formulationFlexibleRigidHand Applied Repair GradesImproved elongationFast cure timesAbrasion ResistanceHigh film buildsAbrasion 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 LiningsPolyurea 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 ConsDo not tolerate moisture well during application or initial curePlural Component direct impingement applicationChemical resistanceHigh tensile strengthPrimer may be requiredProsFast dry timesHigh film buildsUsed for linings and chimney sealsPhysical ToughnessExcellent Abrasion resistanceElongationAbrasion Resistance – 6 mg loss; Tensile Strength – 3,000 psi; Elongation – 425 psi; Tear Strength 495 pli; 20% Sulfuric Acid – No EffectApplication – Only suitable for large structures unless applied through ROI equipment
46 Inspection and Holiday Inspection Required to test liner for discontinuityMoisture in substrate sufficient for readingHigh Voltage – > 20.0 DFT100 volts per dry mil
47 Polyurethane Elastomer Installation Spark TestingPolyurethane Elastomer InstallationFor 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 SummaryThere 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.