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C*ACI 350.2R-04 supersedes ACI 350.2R-97 and became effective June 28, 2004.Copyright 2004, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic ormechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission inwriting is obtained from the copyright proprietors.

ACI Committee Reports, Guides, Standard Practices, andCommentaries are intended for guidance in planning,designing, executing, and inspecting construction. Thisdocument is intended for the use of individuals who arecompetent to evaluate the significance and limitations of itscontent and recommendations and who will acceptresponsibility for the application of the material it contains.The American Concrete Institute disclaims any and allresponsibility for the stated principles. The Institute shall notbe liable for any loss or damage arising therefrom.

Reference to this document shall not be made in contractdocuments. If items found in this document are desired by theArchitect/Engineer to be a part of the contract documents, theyshall be restated in mandatory language for incorporation bythe Architect/Engineer.

350.2R-1

It is the responsibility of the user of this document toestablish health and safety practices appropriate to the specificcircumstances involved with its use. ACI does not make anyrepresentations with regard to health and safety issues and theuse of this document. The user must determine theapplicability of all regulatory limitations before applying thedocument and must comply with all applicable laws andregulations, including but not limited to, United StatesOccupational Safety and Health Administration (OSHA)health and safety standards.

This report presents recommendations for structural design, materials, andconstruction of structures commonly used for hazardous materials contain-ment, including reinforced concrete tanks, sumps, and other structures thatrequire dense, impermeable concrete with high resistance to chemical attack.The report discusses and describes design and spacing of joints, propor-tioning of concrete, placement, curing, and protection against chemicals.Information on liners, secondary containment systems, and leak-detectionsystems is also included.

Keywords: construction joint; joint; joint sealant; precast concrete; pre-stress; water-cementitious material ratio; waterstop.

CONTENTSChapter 1General, p. 350.2R-2

1.1Scope1.2Definitions1.3Types of materials

*Members of ACI 350 Hazardous Materials Subcommittee who prepared this report. Lawrence Valentine served as Chair andSteven R. Close served as Secretary and then took over as chair during the final processing of this revision.Deceased.

Carl A. Gentry Nicholas A. Legatos Lawrence J. Valentine

Clifford Gordon Lawrence G. Mrazek Miroslav F. VejvodaPaul Hedli Javeed A. Munshi Paul Zoltanetzky, Jr.

Jerry A. Holland Jerry Parnes

John A. Aube Ashok K. Dhingra Clifford T. Early, Jr.*

William H. Backous Robert E. Doyle William J. HendricksonPatrick J. Creegan Donald L. Dube David A. KleveteDavid A. Crocker

Consulting and associate members who contributed to this report:Concrete Structureof Hazardou

Reported by AC

James P. Archibald* William

Jon B. Ardahl Keith W.

John W. Baker* Dov KaWalter N. Bennett Reza M.

Steven R. Close* David G

Anthony L. Felder Dennis

Charles S. HanskatChairs for Containments Materials Committee 350

ACI 350.2R-04

J. Irwin Andrew R. Philip

acobson* Narayan M. Prachand

inetzky Satish K. Sachdevianoush William C. Schnobrich

Kittridge John F. Seidensticker

. Kohl* William C. Sherman

Lawrence M. TabatSecretary

E350.2R-2 ACI COMMITT

Chapter 2Concrete design and proportioning,p. 350.2R-3

2.1General2.2Design2.3Concrete cover2.4Exposure2.5Concrete mixture proportions2.6Fiber-reinforced concrete

Chapter 3Waterstops, sealants, and joints,p. 350.2R-6

3.1Waterstops3.2Joint sealants3.3Joints

Chapter 4Construction considerations,p. 350.2R-8

4.1Sump construction techniques4.2Curing and protection4.3Inspection

Chapter 5Liners and coatings, p. 350.2R-115.1Liners5.2Coatings5.3Selection considerations for liners and coatings5.4Inspection and testing of liner and coating installations

Chapter 6Secondary containment, p. 350.2R-146.1General6.2Secondary containment system features6.3Secondary containment materials

Chapter 7Leak-detection systems, p. 350.2R-147.1General7.2Drainage media materials7.3Design and installation of drainage media

Chapter 8References, p. 350.2R-168.1Referenced standards and reports8.2Cited references

CHAPTER 1GENERAL1.1Scope

This report is intended for use in the structural design andconstruction of hazardous material containment systems.Hazardous material containment structures require secondarycontainment and, sometimes, leak-detection systems.Because of the economic and environmental impact of evensmall amounts of leakage of hazardous materials, bothprimary and secondary containment systems should be virtuallyleak free. Therefore, when primary or secondary containmentsystems involve concrete, special design and constructiontechniques are required. This report supplements andenhances the requirements of ACI 350, which is intended forstructures commonly used in water containment, industrialand domestic water, and wastewater treatment works. ACI350, however, does not give specific guidance on the designof the double containment systems, leak-detection systems,or the additional recommendations for enhancing liquid-

tightness covered in this report. This report does not apply toE REPORT

primary or secondary containment of cryogenic liquids,nonliquid materials, or to systems containing radioactivematerials.

The use of information in this report does not ensurecompliance with applicable regulations. The recommendationsin this report were based on the best technical knowledgeavailable at the time they were written; however, they maybe supplemented or superseded by applicable local, state,and national regulations. Therefore, it is important toresearch such regulations (see Section 8.1) thoroughly.

Guidelines for containment and leakage-detection systemsgiven in this report involve combinations of materials thatmay not be readily available in all areas. Therefore, localdistributors and contractors should be contacted during thedesign process to ensure that materials are available.

Proper and thorough inspection of construction is essentialto ensure a quality final product. The written program forinspection should be detailed and comprehensive, andshould be clearly understood by all parties involved. SeeSection 4.3 for an inspection checklist. (See ACI 311.4R forguidance in inspection programs.) A preconstruction confer-ence to discuss the program in detail is recommended.Personnel should be qualified, experienced, and certified asapplicable to their specialty.

1.2DefinitionsThe definitions in Sections 1.2.1 through 1.2.11 have been

correlated with the U.S. Environmental Protection Agency(EPA) Resource Conservation and Recovery Act (RCRA)regulations.

1.2.1 Hazardous materialA hazardous material isdefined as having one or more of the following characteristics:ignitable (NFPA 49), corrosive, reactive, or toxic.

NOTE: EPA-listed wastes are organized into three categoriesunder RCRA: source-specific wastes, generic wastes, andcommercial chemical products. Source specific wastesinclude sludges and wastewaters from treatment and productionprocesses in specific industries such as petroleum refiningand wood preserving. The list of generic wastes includeswastes from common manufacturing and industrialprocesses such as solvents used in degreasing operations.The third list contains specific chemical products such asbenzene, creosote, mercury, and various pesticides.

1.2.2 TankA tank is a stationary containment structurewith self-supporting, watertight walls constructed ofnonearthen material.

1.2.3 Environmental tankAn environmental tank is atank used to collect, store, or treat hazardous material. Anenvironmental tank usually provides either primary orsecondary containment of a hazardous material.

1.2.4 Tank systemA tank system includes its primaryand secondary containment systems, leak-detection system,and the ancillary equipment.

1.2.5 Ancillary equipmentAncillary equipment includespiping, fittings, valves, and pumps.

1.2.6 SumpA sump can be any structural reservoir,usually below grade, designed for collection of runoff or

accidental spillage of hazardous material. It often includes

ACONCRETE STRUCTURES FOR CONT

troughs, trenches, and piping connected to the sump to helpcollect and transport runoff liquids. Regulations may notdistinguish between a sump and an underground tank.

1.2.7 Primary containment systemA primary containmentsystem is the first containment system in contact with thehazardous material.

1.2.8 Secondary containment systemA secondarycontainment system is a backup system for containment ofhazardous materials in case the primary system leaks or failsfor any reason.

1.2.9 Spill or system failureA spill or system failure isany uncontrolled release of hazardous material from theprimary containment system into the environment or into thesecondary containment system. It may also be from thesecondary containment system into the environment.

1.2.10 Spill- or leak-detection systemA spill- or leak-detection system detects, monitors, and signals a spill orleakage from the primary containment system.

1.2.11 Membrane slabA membrane slab is a slab-on-ground designed to be liquid-tight and transmit loads directlyto the subgrade.

1.3Types of materialsThis report provides guidance for the design and construction

of environmental tanks and sumps of reinforced concreteconstruction. Tanks may be constructed of prestressed ornonprestressed reinforced concrete, or steel or other materialswith concrete foundations, concrete secondary containmentsystems, or both. Reinforced concrete is the most widelyused material for sumps, particularly below grade.

Liners for environmental tanks and sumps are made of stain-less or coated steel, fiber-reinforced plastics (FRP), variouscombinations of esters, epoxy resins, or thermoplastics.

This report outlines and discusses options for constructionmaterials and provides recommendations for use, whereapplicable.

CHAPTER 2CONCRETE DESIGN AND PROPORTIONING

2.1GeneralConcrete is particularly suitable for above- and below-

grade environmental primary and secondary containmentsystems. When properly designed and constructed, concretecontainment systems are impermeable and highly resistant tofailure during fires. See ACI 216R, CRSI (1980), and Zwiersand Morgan (1989) for information on exposure of concreteto elevated temperatures.

Concrete is a general-purpose material that is easy to workwith and is resistant to a wide range of chemicals. It is used inconstruction of both primary and secondary containmentsystems. The addition of pozzolans, latex, and polymer modi-fiers can increase concretes resistance to chemical attack.

Measures that should be considered to help preventcracking or to control the number and width of cracksinclude: prestressing, details that reduce or prevent restraintof movements due to shrinkage and temperature changes,

higher than normal amounts of nonprestressed reinforcement,closer spacing of reinforcement, shrinkage-compensatingINMENT OF HAZARDOUS MATERIALS 350.2R-3

concrete, concrete mixtures proportioned to reduceshrinkage, and fiber reinforcement. Additionally, someconstruction techniques, such as casting floors and wallsmonolithically (Chapter 4), help prevent or reduce crackingby eliminating the restraint of shrinkage and temperaturemovements of the subsequently placed concrete along thejoint with the previously placed concrete. See ACI 224R andACI 224.3R for additional information on mitigation ofcracking in concrete structures.

2.2Design2.2.1 Design considerationsThe walls, base slabs, and

other elements of containment systems should be designedfor pressure due to contained material, lateral earth pressure,buoyancy, wind, seismic, and other superimposed loads.ACI 350 provides requirements for the design of bothprestressed and nonprestressed tanks and other environ-mental structures. See ASTM C 913 for additional designprovisions relating to factory-precast sumps.

ACI 372R, AWWA D110, ACI 373R, and AWWA D115provide additional guidance for the design of prestressedconcrete liquid-containment structures. See ACI 223 for infor-mation and guidance on shrinkage-compensating concrete.

Roofs should be designed for dead loads, including anysuperimposed dead loads (insulation, membranes, mechanicalequipment, and earth load, if buried) and live loads (snow,pedestrians, and wheel loads, if applicable).

A minimum slope of 2% should be included in the designof floors and trench bottoms to prevent ponding and helpdrainage. Secondary containment systems for flammableand combustible liquids should have a slope that is in accor-dance with NFPA 30, Flammable and Combustible LiquidsCode, or an applicable fire code.

2.2.2 Wall thickness and reinforcementThe minimumwall thickness and reinforcing steel location in walls shouldcomply with Table 2.1.

Table 2.1Wall thickness and reinforcement locations based on concrete placement consideration

Description Wall heightMinimumthickness

Reinforcement location

Cast-in-place concrete

Over 10 ft(3000 mm) 12 in. (300 mm) Both faces4 to 10 ft

(1200 to 3000 mm) 10 in. (250 mm) Both faces

Precast concrete

Less than 4 ft(1200 mm) 6 in. (150 mm) Center of wall

4 ft (1200 mm) or more

8 in. (200 mm) Center of wallLess than 4 ft(1200 mm) 4 in. (100 mm) Center of wall

Description Minimum wall thicknessTendon prestressed concrete tanks See ACI 350

Wrapped prestressed concrete tanks See ACI 350Note: Placement windows (temporary openings in the forms) or tremies are recom-mended to facilitate concrete placement in cast-in-place walls greater than 6 ft(1800 mm) in height.2.2.3 FootingsFootings should be cast on top of, ormonolithically with, the floor slab to enhance liquid tightness.

T350.2R-4 ACI COMMIT

Upturned footings help reduce restraint of shrinkage and itsassociated cracking.

2.2.4 Slabs-on-ground2.2.4.1 Membrane slabsACI 350 provides requirements

for the minimum shrinkage and temperature reinforcementand, if post-tensioned, the residual prestressing requirementsfor membrane floor slabs. Prestressed membrane slabsshould have a minimum thickness of 5 in. (125 mm).Nonprestressed membrane slabs should have a minimumthickness of 6 in. (150 mm). To enhance liquid-tightness,membrane slabs should be placed without constructionjoints. A membrane slab can be reinforced with prestressedand nonprestressed reinforcement in the same layer in eachdirection, or with nonprestressed reinforcement only, at ornear the center of the slab. If prestressed, they should have aminimum of 200 psi (1.4 MPa) residual compression afterdeducting for all losses, including the effects of frictionbetween the slab and the subgrade and after allowing for anytension tie forces. This amount of prestressing has beenfound to provide liquid-tightness without excessive crackingdue to gradual differential subgrade settlements, shrinkageand temperature effects, or both, in slabs on properlyprepared subgrade.

2.2.4.2 Pavement slabsThe term pavement slabs, asused in this report, denotes the particular case of slabs-on-ground designed for drainage capture and primary orsecondary containment of hazardous materials when vehicleor other concentrated loads are anticipated. Pavement slabscan be either prestressed or nonprestressed and designed asplates on elastic foundations. A qualified geotechnical engineershould determine the properties of the subgrade, includingsoil classification and modulus of subgrade reaction.Acceptable analytical techniques include finite element,finite difference, and other techniques that give comparableresults. Flexural and punching shear stresses should be usedto design the conventional and prestressed reinforcement.

Nonprestressed pavement slabs designed for vehicle loadsof AASHTO H-10 or heavier should be at least 8 in. (200 mm)thick and should contain two layers of reinforcement in eachdirection (AASHTO Standard Specification). The slabthickness for lighter wheel loads may be according toSection 2.2.4.1. The reinforcement percentage should totalat least 0.5% of the cross-sectional area in each orthogonaldirection, with at least one-half, but not more than two-thirds,of this amount in the upper layer. ACI 350 provides require-ments for the design of flexural reinforcement, including theadditional durability factor, where applicable.

Prestressed pavement slabs designed for vehicle loads ofAASHTO H-10 or heavier should be at least 6 in. (150 mm)thick. When unbonded post-tensioning tendons are used, thenonprestressed reinforcement percentage should total at least0.30% for primary containment and 0.15% for secondarycontainment in each orthogonal direction. The reinforcementis usually placed at the mid-depth of the slab when theprestressed pavement slab is less than 8 in. (200 mm) thick.When the prestressed pavement slab is 8 in. (200 mm) thick,

or more, the nonprestressed reinforcement is usually dividedinto two mats, one near each face. The prestressed reinforce-EE REPORT

ment, however, should remain near the center of the slab.The residual compressive stress in the slab should be atleast 200 psi (1.4 MPa) after deducting strand friction, long-term losses, and losses due to friction between the slab andthe subgrade. Flexural tensile stresses should not exceed2fc psi (0.167fc MPa) under service loads, unless bondedreinforcement is provided in the precompressed tensile zone.Flexure and shear requirements are given in ACI 350,Section A.3.2(b) for the various bar sizes, exposure condi-tions, and grades of reinforcement.

As with membrane slabs, pavement slabs intended to beliquid-tight should be placed without construction jointswhenever possible. When joints are unavoidable, theyshould be designed and detailed according to the otherrecommendations of this report.

2.2.5 Mat foundationsMat foundations are usually 12 in.(300 mm) thick with two layers of nonprestressed reinforcementor 10 in. (250 mm) thick with prestressed reinforcement.Additional concrete thickness can be provided to help resistbuoyancy, if required.

2.2.6 Minimum reinforcement for nonprestressed secondarycontainmentThe minimum reinforcement to counter theeffects of shrinkage and temperature changes for concreteused as secondary containment structures should complywith ACI 350.

2.2.7 Minimum reinforcement for nonprestressed primarycontainmentTo counter the effects of shrinkage andtemperature changes, the minimum reinforcement contentfor concrete used as primary containment should be 0.5% ofthe cross-sectional concrete area. To further limit crackingcaused by restraint of free movement due to shrinkage andtemperature dropping, the reinforcement parallel to aconstruction joint should be increased to 1.0% within thefirst 4 ft (1200 mm) of a construction joint in the subsequentplacement (Fig. 2.1). For crack mitigation, it is preferable touse several small-diameter bars rather than fewer bars of alarger diameter. The maximum bar spacing should notexceed 12 in. (300 mm).

2.2.8 Minimum nonprestressed reinforcement forprestressed concreteThe minimum nonprestressedreinforcement in prestressed concrete containment structuresshould be 0.15% for secondary containment and 0.30% forprimary containment when movement due to shrinkage ispartially restrained, such as slabs-on-ground. It should be thesame as recommended for nonprestressed concrete wherevermovement due to shrinkage is fully restrained, such as whenconcrete is placed against and bonded to hardened concreteat a construction joint.

2.2.9 Roofs2.2.9.1 Joints in roofsLiquid-tight cast-in-place roofs

should be placed without construction joints wheneverpossible. When joints in cast-in-place roofs are unavoidable,they should be designed and detailed according to therecommendations of Section 2.2.7. Joints between precastroof members should be designed and detailed for liquid-

tightness with requirements provided by ACI 350 andSection 3.2 of this report.

ICONCRETE STRUCTURES FOR CONTA

2.2.9.2 Roof designACI 350 provides requirementsfor the design of domes and post-tensioned roof slabs forprestressed concrete liquid-containing structures. Roof slabscan be either prestressed or nonprestressed. Acceptableanalytical techniques include finite element, finite difference,equivalent frame, and other techniques that give comparableresults. Flexural and punching shear stresses should be usedto design the section thickness and conventional andprestressed reinforcement.

Flat nonprestressed roof slabs should be at least 6 in.(150 mm) thick. The reinforcement percentage should totalat least 0.5% of the cross-sectional concrete area in eachorthogonal direction. ACI 350 provides requirements for thedesign of flexural reinforcement, including the additionaldurability coefficients where applicable. Roof slabs should bechecked for long-term deflection and the potential for ponding.

Flat prestressed roof slabs should be at least 6 in. (150 mm)thick. When unbonded post-tensioning tendons are used, thenonprestressed reinforcement ratio should be in accordancewith the requirements of ACI 350. The compressive stress inthe slab should be at least 150 psi (1.0 MPa) after tendon frictionand long-term losses and after considering the restrainingeffects of walls. This is less than the minimum compressivestress recommended for floors and walls because the roof doesnot actually contain the hazardous material.

Flexural tension should be limited to 2 fc psi (0.167 fcMPa), unless bonded reinforcement is provided in theprecompressed tensile zone. This reinforcements designrequirements are given in ACI 350 for the various bar sizes,exposure conditions, and grades of reinforcement.

2.3Concrete coverReinforcement should have at least the minimum concrete

cover required by ACI 350. Additional concrete cover orcoatings on the concrete can be used as needed for supple-mental corrosion protection.

2.4Exposure2.4.1 Freezing and thawingConcrete in a saturated or

near saturated condition is susceptible to damage due tofreezing-and-thawing cycles. Air entrainment improvesfreezing-and-thawing resistance and should be specified forconcrete exposed to such conditions. Resistance to freezing-and-thawing damage is also improved by measures thatincrease the density or reduce the permeability of the concrete.

In severe freezing-and-thawing environments, concreteshould be protected from multiple freezing-and-thawingcycles or from reaching near saturated conditions. Externalinsulation or burial helps limit the number of cycles andseverity of the freezing. Also, internal liners or coatings canbe used to reduce the moisture saturation of the concrete.

2.4.2. Other durability considerationsFor harsh serviceconditions, reinforcement cover should be increased and, ifnecessary, the concrete should be provided with a corrosion-protection system. Harsh service conditions include exposureof the concrete to chemicals and materials that will have a

chemical reaction with the concrete. These service conditionsinclude exposure to certain acids and bases and high sulfateNMENT OF HAZARDOUS MATERIALS 350.2R-5

content solutions. Coated reinforcement or coatedprestressing, stainless steel, or nonmetallic reinforcementshould be considered in corrosive chemical applications.When using coated reinforcement, the reduction in bondstrength, particularly as it may affect cracking, should betaken into account. Using a greater number of smaller diameterbars or a higher percentage of reinforcing (a higher rein-forcing ratio) will reduce these effects. See ACI 201.2R forother durability considerations.

2.4.3 Chemical resistanceSome chemicals are soaggressive to concrete that the only way to provide protectionfor the concrete is to provide a corrosion-protection system,such as a coating or covering. The corrosion-protectionsystem should provide not only corrosion protection but, tothe maximum extent possible, the flexibility to span cracksand accommodate the expansion and contraction the concretewill experience due to moisture and temperature changes.

2.5Concrete mixture proportions2.5.1 Water and cementitious materialThe maximum

water-cementitious material ratio (w/cm) (cement pluspozzolan) should be 0.40 for primary containment and inaccordance with ACI 350 for secondary containment.

Water demand for shrinkage-compensating concrete ishigher than for portland-cement concrete. Refer to ACI 223,Section 4.2, for guidance on shrinkage-compensatingconcrete proportions.

To reduce permeability, the minimum cementitious materialscontent should be 700 lb/yd3 (420 kg/m3) for primarycontainment and 600 lb/yd3 (360 kg/m3) for secondary

Fig. 2.1Recommendations for increased reinforcementpercentage parallel to bonded joints.containment. When fly ash or other pozzolans exceed 25%

T350.2R-6 ACI COMMIT

of total cementitious materials content, the designer shouldconsider their effects on durability and chemical resistance.

2.5.2 AdmixturesWorkability can be increased by theaddition of normal or high-range water-reducing admixturesand air-entraining admixtures. Calcium chloride or admix-tures containing chloride from other than incidental impuri-ties should not be used in concrete for either primary orsecondary hazardous material containment systems. Theadmixture should undergo certification, tests, or both, toconfirm this requirement.

2.5.3 Compressive strengthThe minimum cementitiousmaterial contents and maximum w/cm given in Section 2.5.1should result in compressive strengths of the concrete thatexceed most structural requirements and the requirements ofACI 350.

2.5.4 Air entrainmentACI 350 provides requirementsfor the air entrainment of concrete.

2.6Fiber-reinforced concrete2.6.1 GeneralFiber-reinforced concrete (FRC) uses

fibers that are available in lengths ranging from 3/4 to 2 in.(20 to 50 mm) long. Mixing these fibers with concrete mayreduce cracking due to plastic shrinkage.

When selecting fibers for use in reinforced concrete,consideration should be given to the fact that some fibers (forexample, rayon, acrylic, fiberglass, and polyesters) aresubject to alkali attack by the cement. Only fibers that are chem-ically compatible with the hazardous materials containedshould be used.

Fibers do not replace reinforcement. The same membersizes and minimum reinforcement apply for concrete with orwithout fibers.

Fibers, together with an epoxy bonding agent, shouldallow the application of a thinner (2 in. [50 mm] minimum)overlay on existing concrete, such as clarifier topping slabs.

2.6.2 ProportioningThe fiber ratio should follow themanufacturers recommendations. The fibers can be added atthe batch plant or the construction site. In either case, thefibers need a mixing time of at least 7 min (at the mixingspeed recommended by the manufacturer) to ensure dispersionof the fibers throughout the concrete.

The addition of fibers normally reduces the slump by 1 to2 in. (25 to 50 mm). This should be considered in the mixtureproportioning. The use of high-range water-reducing admix-tures should regain the lost workability without the additionof water.

2.6.3 FinishingThe addition of polypropylene fibers toconcrete makes it more difficult to achieve a smooth steel-troweled finish. The fibers will usually protrude from theconcrete. The exposed portions of the fibers should degradequickly due to traffic abrasion or UV exposure.

CHAPTER 3WATERSTOPS,SEALANTS, AND JOINTS

3.1Waterstops3.1.1 GeneralWaterstops should be provided at expan-sion/contraction joints and where construction joints cannotbe avoided. Waterstops are positioned in concrete joints toEE REPORT

prevent the passage of liquid through the joint. Mechanicaljoints may be considered for repairing an existing joint. (SeeFig. 3.1 as an example.)

3.1.2 MaterialsThe chemical resistance of the waterstopmaterial, exposure, temperature, and chemical concentrationof the contained material should be considered whenselecting the waterstop material. Each situation should beevaluated individually, including concrete placement andconcrete cover recommendations from the manufacturer.

3.1.2.1 PVC waterstopsPVC waterstops are manufac-tured in various sizes and many special shapes such as dumb-bell, serrated, with or without center bulb, split, and tear web.When movement across the joint is expected, serrated orribbed profiles with center bulbs should be used. The ribsincrease the effective mechanical seal area of the waterstop,while the bulbs accommodate the movement.

3.1.2.2 Expansive rubberExpansive rubber waterstops,which expand on contact with water, may be used in joints castagainst previously placed concrete and in new construction.Adhesive type expansive rubber waterstops should only beused where joint movement is prevented. Expansive rubberwaterstops expand on contact with water and may contract ifpermitted to dry out. Joints using such waterstops may leakuntil adequate moisture is present to re-expand the waterstop.Furthermore, the waterstop may not have the same expan-sive properties when exposed to chemicals instead of water.

3.1.2.3 Metal waterstopsMetal waterstops should bestainless steel or other metals compatible with the hazardousmaterial. Metal waterstops should not be used in jointssubject to movement.

3.1.2.4 Injectable tube systemsInjectable tube water-stopping systems can also be used in concrete environmentalstructures. The injected material should be compatible withthe hazardous material to be contained.

3.1.2.5 Other materialsOther materials can be used,provided they are compatible with the hazardous material.

3.1.3 Splicing3.1.3.1 PVC waterstopsProper splicing of waterstops

is extremely important to ensure continuity and liquid-tightness. Splices should be avoided if possible. Splices for

Fig. 3.1Mechanical joint repair at an existing joint.corner, tee, and cross junctions made in the factory are alsoavailable for certain types of materials and shapes. The

ACONCRETE STRUCTURES FOR CONT

procedures for splicing vary with the type of material and themanufacturers recommendations for proper splicing.

3.1.3.2 Metal waterstopsMetal waterstops should bespliced as recommended by the engineer or manufacturer.

3.1.4 Installation3.1.4.1 GeneralImproperly installed waterstops can

create leaky joints. The waterstop should be clean and free ofdirt and splattered concrete. Intimate contact with clean,sound concrete is essential over the entire surface of thewaterstop. Entrapped air and honeycombing near the jointcould compromise the effectiveness of the waterstop. Thewaterstop should be placed and located accurately with thecenter bulb directly at the centerline of expansion andcontraction joints. Otherwise, the functionality of the centerbulb is lost.

3.1.4.2 Horizontal PVC waterstops Joints in floorslabs are vulnerable to leakage and difficult to inspect, underservice conditions, due to their location. Therefore, jointsthat require waterstops should not be used if at all possible.If joints must be used, care should be taken to place concretewithout voids or honeycombing under horizontal PVCwaterstops. Horizontal PVC waterstops should be supportedin such a way as to be able to be lifted as the concrete isplaced underneath (Fig. 2.1 and 3.2). Any dowels throughthe joints should not interfere with the edges of the water-stops when they are lifted. The concrete under the liftedwaterstop should be vibrated, the PVC waterstop laid intothe concrete placed on top of the waterstop, and the entirejoint vibrated again.

Continuous inspection of concrete placement aroundhorizontal PVC waterstops in floor slabs is necessary.

3.1.4.3 Vertical PVC waterstopsVertical PVC water-stops should be braced or lashed firmly to the reinforcementat no more than 12 in. (300 mm) centers to prevent movementduring placing of the concrete (Fig. 3.2 and 3.3).

3.1.4.4 Metal waterstopsMetal waterstops should beinstalled in accordance with the contract documents and themanufacturers recommendations, and the concrete underhorizontal metal waterstops properly placed and consolidated.

3.1.4.5 Expansive rubber and injectable tube systemsExpansive rubber and injectable tube systems should beinstalled in accordance with the contract documents and themanufacturers recommendations. Adequate concrete cover isnecessary to avoid spalling at the joint due to expansive forces.

3.2Joint sealants3.2.1 General Provide joints with chemically resistant

sealants. See ACI 504R for additional information onsealing joints.

Sealants are generally applied in liquid or semiliquid form,and are thus formed into the required shape within the moldprovided at the joint opening.

The manufacturers recommendations and applications foruse should be thoroughly explored for each specific applicationof a sealant. ACI 504R provides additional information onjoint sealants.For satisfactory performance, a sealant should:1. Be impermeable;INMENT OF HAZARDOUS MATERIALS 350.2R-7

2. Be deformable to adapt to the expected joint movement;3. Recover its original properties and shape after cyclical

deformations;4. Remain bonded to joint faces. The sealant should only

be bonded to the sides of expansion and contraction joints tospread the movement over the full width of the sealant;

5. Remain pliable and not become brittle at higher or lowerservice temperatures;

6. Be resistant to weather, sunlight, aging, continuousimmersion (when applicable), and other service factors; and

7. Be resistant to chemical breakdown when exposed tothe contained material.

Generally, the elastomeric sealants, according to ASTM C

Fig. 3.2Typical expansion joints.

Fig. 3.3Base slab to wall starter joint.920, are preferable to oil-based mastic or bituminouscompounds.

T350.2R-8 ACI COMMIT

Although initially more expensive, thermosetting, chemical-curing sealants have a generally longer service life andshould withstand greater movements. The sealants in thisclass are either one- or two-component systems that cure bychemical reaction. Sealants in this category include polysul-fides, silicones, and urethanes.

Some sealants require primers to be applied to joint facesbefore sealant installation. If the manufacturer specifies theuse of a primer as optional, it should be used for hazardousmaterial containment systems.

Backup materials limit the depth of sealants, support themagainst sagging and fluid pressure, and help tooling. Theymay also serve as a bond breaker to prevent the sealant frombonding to the back of the joint.

Backup materials are typically made of expanded poly-ethylene, polyurethane, polyvinyl chloride, and flexiblepolypropylene foams. The sealant manufacturers recom-mendations should be followed to ensure compatibility withbackup materials.

Polyethylene tape, urethane backer rods, coated papers,metal foils, or other suitable materials can be used if a separatebond breaker is necessary.

3.2.2 Joint preparationJoint faces should be clean andfree from defects that would impair bond with field-moldedsealants. Sandblasting is the best method to clean joint faceson existing structures. Sandblasting should be used if amembrane curing compound is used and does not dissipatebefore the installation of the sealant, particularly with chem-ically cured thermosetting sealants. Solvents should not beused to clean joint faces. Final cleanup to dry and removedust from the joint may be accomplished by oil-freecompressed air or vacuum cleaner.

Inspection of each joint is essential to ensure that it is cleanand dry before placing backup materials, primers, or sealant.Primers need the required time to dry before sealant installation.Failure to allow this may lead to adhesion failure. Primerscan be brushed or sprayed on. The manufacturers specifica-tions and recommendations should be followed.

3.2.3 Sealant installationBackup materials requireproper positioning before the sealant is installed. Backupmaterials should be set at the correct depths and contaminationof the cleaned joint faces avoided. The correct width andshape of backup material should be selected so that, afterinstallation, it is approximately 50% compressed, andstretching, braiding, or twisting rod stock should be avoided.

Backup materials containing bitumen should only be usedin combination with compatible oil-based or bituminoussealants. Oils absorbed into joint surfaces may impair adhesionof other sealants.

Sealants with two or more components require full and inti-mate mixing if the material is to cure with uniform properties.

If the sealant is applied with a gun, the gun nozzle shouldbe held at a 45-degree angle. The gun should be movedsteadily along a joint to apply a uniform bead by pushing thesealant in front of the nozzle without dragging, tearing, orleaving unfilled spaces. In large joints, the sealant should be

built up in several passes, applying a triangular wedge oneach pass.EE REPORT

Tooling may be required to ensure contact with joint faces,remove trapped air, consolidate material, and provide a neatappearance, following the manufacturers recommendations.

3.2.4 Sealant inspection and maintenanceJoints shouldbe inspected during construction and at scheduled periodsfollowing construction to ensure sealant integrity. Thefrequency of inspection should be established consideringthe resistance of the sealant to chemical attack from thecontained materials, with frequency increasing as theexpected life is approached.

Immediate repairs of defective joints and sealants in hazardousmaterial containment structures and sumps is required.

Repairs of small gaps and soft or hard spots in sealants canusually be made with the same material. When the repair isextensive, it is usually necessary to remove the sealant, prop-erly prepare the surfaces, and replace the sealant.

3.3JointsJoints in primary and secondary containment applications

should be avoided wherever possible. Joints should beprovided only where shown and detailed on the drawings orpermitted by the engineer.

Construction joints should only be used when absolutelynecessary for construction. Because liquid tightness is ofprimary concern in environmental systems, the design drawingsand specifications should show the location of acceptableconstruction joints and specify waterstops and sealants.

CHAPTER 4CONSTRUCTION CONSIDERATIONS4.1Sump construction techniques

4.1.1 Precasting sumps in a single unitThere are threemajor advantages of precasting concrete sumps in a singleunit. First, it eliminates construction joints, which can be amajor source of leakage and cracking. Second, it gives bettercontrol of the concrete placement when the sump is precastin the upside-down position. Third, it results in lowerconstruction cost and more efficient job scheduling. Precastsumps may be fabricated at the contractors convenience.Also, with proper scheduling the precast units can cure aslong as required before installation. The unit can be set andbackfilled the same day. In contrast, when sumps are cast-in-place, the excavation for the sump will be open for severaldays or weeks to build the forms and cast the concrete. Toprevent damage to the sump walls, it takes additional time tocure the concrete and strip the forms before backfilling.

The size of a precast concrete sump is limited by the sizeof lifting and hauling equipment.

An optional secondary containment slab, sloped in theform of a bowl below a precast sump, will help reduce thedispersion of potential leakage. Refer to Fig. 4.1 for an illus-tration of this setting technique.

4.1.2 Monolithic placement of cast-in-place sumpsLikethe precast sumps, monolithic placement of concrete in slabsand walls eliminates joints and associated shrinkage cracks.One of two conditions is needed to place concrete in wallsmonolithically with slabs:

Walls less than 4 ft (1200 mm) high; and A base slab width less than 4 ft (1200 mm).

CONCRETE STRUCTURES FOR CONTA

The following paragraphs discuss each of these condi-tions. Monolithic placement is limited by the shape and sizeof the sump.

4.1.2.1 Walls less than 4 ft (1200 mm) highForm wallsless than 4 ft (1200 mm) high, as shown in Fig. 4.2. Thisincludes placing an approximately 6 in. (150 mm) high lift ofthe wall concrete shortly after placing the base slab concrete.This starter wall segment should be placed after the slabconcrete starts to stiffen, but before a cold joint formsbetween the starter wall segment and the base slab. Theremaining portion of the wall needs to be placed before acold joint forms at the top of starter wall segment but afterthe slab concrete has set sufficiently to prevent a blowout. Ifhigh-range water-reducing admixtures are used in the slabconcrete, their plasticizing effects have to dissipate beforeplacing the starter wall segment. To help prevent a possibleblowout of the slab concrete, hand rodding (not a vibrator)initially can be used to ensure a bond between the first walllift and the starter wall segment. Then vibrators are used toconsolidate the wall concrete, including the first lifts;however, the vibrators should not be allowed to penetrateinto the slab concrete.

4.1.2.2 Base widths less than 4 ft (1200 mm)In sumpsthat have deep walls but bottom slabs less than 4 ft (1200 mm)wide, a plywood form with 3/8 in. (10 mm) holes spaced at12 in. (300 mm) on center each way should form the top

Fig. 4.1Precast sump installation.

Fig. 4.2Monolithic concrete placement for wall heights of4 ft or less.surface of the base slab (Fig. 4.3). The holes in the plywoodINMENT OF HAZARDOUS MATERIALS 350.2R-9

should help ensure the slab concrete is placed withouthoneycombing. High-range water-reducing admixtures maybe beneficial in this mixture. Visual inspections of theconcrete protruding through these holes during placementwill help ensure that the concrete in the floor is being properlyplaced (consolidated).

4.1.3 Traditional constructionWhen joints cannot beavoided, a starter section is recommended for walls. Thisfacilitates wall forming, leak detection, and repair, if needed.

Trench bottoms and tank floor slabs should be cast overthe top of a pit or sump wall instead of butting up against thewall (Fig. 4.4).

Wall ties should have a welded cutoff collar to act as awaterstop. Also, they should be broken off 1 in. (25 mm)

Fig. 4.3Monolithic concrete placement for sumps withfloor span of 4 ft or less.

Fig. 4.4Trench bottom or floor slab joint to sump wall.from the face of the wall in a cone-shaped depression. Epoxy

T350.2R-10 ACI COMMIT

or dry-packed shrinkage-compensating grouts with an epoxybonding agent should be used to fill the resulting holes.

Form materials should provide a smooth form finish,according to ACI 301. Base slabs should have a power-float finish.

4.1.4 Pipe penetrationsPipe penetrations below theliquid level should be avoided when possible. If penetrationsare necessary, they should be through walls (Fig. 4.5 and 4.6)or through the sides of bottom slabs at the outer perimeter ofthe floor (Fig. 4.7) to permit visual inspection. Mechanicalprotection (from differential settlement) of pipes coming outof bottom slabs should be considered. Dual containmentpipes and flexible couplings are two means of providing thisprotection.

Additional reinforcement should be provided around pipepenetrations that interrupt other reinforcing bars. Generally,additional reinforcement should at least replace the area of

Fig. 4.5Steel pipe penetration detail.

Fig. 4.6Pipe penetration detail at a lined containmentstructures. reinforcing bars cut to accommodate the opening in everyapplicable direction. Some designers also recommendEE REPORT

additional bars placed at 45 degrees to the orthogonalreinforcement.

4.1.5 BackfillingWhen a below-grade sump is part ofor attached to a tank floor, the backfill around and beneaththe sump should be thoroughly compacted and tested or bemade of controlled low-strength material. This shouldprevent excessive differential settlement of the floor slabaround the sump.

4.2Curing and protection4.2.1 CuringCuring is one of the most important

operations in reinforced concrete construction. Withoutproper curing, even the best-designed reinforced concretedevelops surface cracks. Refer to ACI 308R and ACI 308.1for a complete description of curing procedures.

The primary purposes of curing are to maintain the moisturecontent of the green concrete at satisfactory levels and protectthe concrete against rapid temperature changes. Inadequatecuring may cause excessive cracking or crazing in theconcrete and seriously reduce the liquid-tightness of thestructure. For concrete placed during cold weather, curingmay also provide protection against freezing.

Dampening the subgrade or the use of plastic sheetingshould be considered before placing cast-in-place concrete forsump bottoms and slabs-on-ground. This helps prevent loss ofmoisture from fresh concrete and provides reserve moisturefor curing. Standing water, however, should not be allowed.

Curing procedures should start when placing and finishingoperations allow. The surface of the concrete placed early inthe placing operation should not be allowed to dry out whileplacing subsequent concrete. The materials and equipmentneeded for curing should be available and ready for usebefore the concrete arrives.

While there are many methods of curing concrete, thereare two main approaches: Apply water or cover with materials saturated with

water; and Prevent loss of water by impervious covers (membranes),

or membrane-forming curing compounds.One or more of the methods described in Sections 4.2.1.1

through 4.2.1.7 can be used.

Fig. 4.7Typical floor penetration detail.4.2.1.1 PondingPonding is one of the best methods ofcuring concrete slabs-on-ground, especially for slabs using

ACONCRETE STRUCTURES FOR CONT

shrinkage-compensating concrete. The concrete is coveredwith water, and the water level is maintained to make up forevaporation during the curing period. Preferably, the watercuring is kept in place until the structure is complete andready to be cleaned up before being placed in service.

4.2.1.2 Running waterSprinklers or soaker hoses areused whenever a continuous flow of water is available, andthe runoff does not cause any harm to the surrounding area.Fog spraying during finishing and curing is also effective,especially in hot weather.

With any methods involving running water, the pressureand flow of water should be kept low enough to avoidwashing away the surface of the newly placed concrete (8 h,more or less, after initial set). Also, for ponding or runningwater, the temperature of the curing water should not bemore than 10 C (20 F) cooler than the surface temperatureof the concrete at the time the water and the concrete comein contact.

4.2.1.3 Absorptive coveringsConcrete may also becured by covering it with wet burlap, blankets, or cotton mats.These coverings can be hung to cover vertical surfaces andplaced on horizontal surfaces. These materials should be keptwet during the entire curing period. Burlap should be heavy-weight and thoroughly rinsed before use. The strips of burlapshould overlap half their width to provide a double layer.

4.2.1.4 SteamSteam curing is a suitable method ofcuring for precast concrete, especially in cold weather.Atmospheric pressure procedures are used.

4.2.1.5 Plastic filmsConcrete slabs-on-ground andwalls may be cured by covering them with 6 mil (0.15 mm)plastic sheets securely anchored at the edges and overlaps.

4.2.1.6 Curing compoundsCuring compounds shouldbe used only when the other methods described in this reportare either impossible or economically impractical. Curingcompounds should be sprayable, with a high solids content(18% minimum), and placed at twice the manufacturersrecommended rate in two coats applied in directions perpen-dicular to each other. A fugitive dye should be used toconfirm complete coverage. They should not be applied onsurfaces expected to bond with subsequently placed concreteor with other materials such as coatings or sealants.

4.2.1.7 DurationConcrete should be cured for at leastseven days.

4.2.2 Cold-weather concretingIn cold weather, concreteshould be cured and protected from freezing as recommendedby ACI 306R. ACI 306.1 should be used for specifying coldweather curing and protection. ACI 306.1 also provides guid-ance on minimum durations for maintaining the protection.Calcium chloride should not be used as a concrete admixture.Excessive chloride quantities promote corrosion of thereinforcing steel. See ACI 350 for chloride limits.

4.2.3 Hot weather concretingIn hot weather, cure andprotect concrete as recommended by ACI 305R. Wood ormetal forms remaining in place are not a satisfactory meansof curing; forms should be covered and kept moist. It isdesirable to loosen the forms as soon as possible without

damaging the concrete and to run curing water down theinside of the forms.INMENT OF HAZARDOUS MATERIALS 350.2R-11

4.3InspectionKey items to be inspected during construction are listed in

Sections 4.3.1 through 4.3.12. See ACI 311.1R for guidanceon inspection, ACI 311.4R for guidance on the set up andcontent of the inspection program, and ACI 311.5R forguidance on concrete plant and field testing. A preconstructionconference should be a mandatory requirement. Inspectionsshould preferably be by an ACI Certified Concrete Inspector.

4.3.1 Subgrade preparationBearing capacity and compac-tion should be checked, and proper grade should be verified.

4.3.2 Reinforcing steelReinforcement size, bends,grade, spacing, minimum concrete cover, proper locationand height of supports, splices, cleanliness, and condition ofany protective coatings should be inspected.

4.3.3 Post-tensioning tendonsSize, spacing, profile, andcondition of sheathing of unbonded tendons and location andcondition of ducts, strand, and grouting of bonded tendonsshould be checked.

4.3.4 WaterstopsProper placement of waterstops,including alignment, should be checked. The ties of PVCwater-stops (when used) to supports should be inspected foradequacy to maintain proper alignment of the waterstopduring concrete placement. Also, the splices of waterstopsshould be checked when used.

4.3.5 JointsBefore placing new concrete against previ-ously placed or existing concrete, the completion of jointpreparation should be verified.

4.3.6 FormworkLine and grade, cleanliness, width,depth, and length should be checked.

4.3.7 InsertsCondition and location of penetrations andinserts, including their sealants and waterstops, should beverified.

4.3.8 ConcreteMixture proportions, including admixturedosages (at the batch plant), and time from plant to siteshould be checked.

4.3.9 Concrete placementPlacing techniques andconsolidation, including placement around waterstops andembedded items, should be inspected.

4.3.10 CuringCuring requirements and conditionsshould be met.

4.3.11 MiscellaneousSpecial requirements for placingshould be met.

4.3.12 Concrete testingConcrete testing should beaccording to the requirements of ACI 301 and performed byan agency accredited to ASTM E 329.

CHAPTER 5LINERS AND COATINGS5.1Liners

Liners can function as either the primary or secondarycontainment, depending upon the type of installation and thelocation of the liner within the installation.

A liner should exhibit good chemical resistance to deteri-oration and compatibility with the hazardous material.

Many different types of liner materials can be used. Insome cases, the material has been specifically developed for

an application. In others, the material has been adopted dueto its specific mechanical, chemical, and thermal properties.

T350.2R-12 ACI COMMIT

In general, all liner materials that can be used for primarycontainment are also suitable for secondary containment. Aswith primary liners, each use is project specific. Additionaldiscussion of liners used as secondary containment and aspart of a leak-detection system is given in Chapters 6 and 7,respectively. Liner materials may be categorized as eithermetallic or geomembrane materials.

5.1.1 MetallicMetal plate liners are suitable for manyapplications, with a wide range of metals available. Forexample, carbon steel may be used to line caustic tanks,trenches, and sumps. Because the liner is usually thin foreconomic reasons and cannot support itself, it is fastened tothe concrete walls (Fig. 5.1 and 5.2) for support. The details offastening should be designed carefully to prevent leakage andto account for all stresses, including thermal effects. Corrosionprotection of metallic liners should also be considered.

5.1.2 Geomembrane materialsThis group of linermaterials includes geomembranes consisting of flexiblethermoplastic polymeric materials. Many types of geomem-branes are available. They range in thickness from 30 to100 mils (0.75 to 2.5 mm). Some geomembranes have a

Fig. 5.1Internal liner construction details.

Fig. 5.2Internal liner attachment details.reinforcing scrim (grid) made of woven polyester or EE REPORT

polypropylene filaments. The materials are manufactured inlarge sheets or panels and are joined or seamed together usingheat fusion, heat extrusion, or chemical welding techniques.

Other specialty products are made of polyethylene. Theseinclude sheets ranging from 50 mils (1.3 mm) to 2 in. (50 mm)thick. Thick sheets are joined at the seams by extrusionwelding. These materials work well for lining the interior ofconcrete sumps or pipes.

The most widely used types of geomembranes includepolyethylene (PE), high-density polyethylene (HDPE), poly-vinyl chloride (PVC), and chlorosulfonated polyethylene(CSPE).

Thermosets include polyester, vinylester, derakane, furan,and epoxy resins made into FRP sheets, preformed sections, orapplied in place. These materials are generally best in high-temperature, aggressive acid service. They can be relativelybrittle and have high thermal expansion coefficients comparedwith steel and concrete. Their use as liners for concrete instal-lations may be limited due to the difficulties of fastening.Therefore, they are often used as bonded coatings.

5.2CoatingsWhen the material contained in the primary system is

aggressive to concrete, a coating is appropriate. Secondarycontainment systems can also require a coating in areaswhere piping connections and disconnections are frequentlymade or when required by the applicable environmentalauthority. Coating systems include materials such as paints,mortars, liquefied rubbers, and resins. Some coating systemsincorporate reinforcing scrims applied in multiple layers.Other coating systems include vitrified clay tile and acid-proof and chemical-resistant mortar. Concrete to be coatedshould be tested for moisture to determine compatibility withthe coating manufacturers requirements.

Application methods include brushing, spraying, rolling,troweling, and shotcreting. These depend on the material andthe type of installation. In coating systems, the bond to theconcrete (ASTM C 811) and the curing conditions are critical.Manufacturers recommendations should be fully understoodand followed. See ACI 515.1R for additional information oncoatings.

5.3Selection considerations for liners and coatings

5.3.1 Testing for compatibilityCompatibility of the lineror coating material with the contents is the primary designconsideration. Compatibility tests between the contents andliner or coating materials, including fabricated seams, shouldbe performed. These tests should simulate the actual opera-tional conditions, pH, temperature, pressure, and otherservice conditions as closely as possible. Vendor literatureand past case histories are for information, but actual testingis highly recommended. Testing may take up to six monthsto complete; therefore, the testing should be initiated as earlyin the design process as possible. Accelerated testingprocedures may be available, but caution should be exercised in

use and interpretation of the results.

ICONCRETE STRUCTURES FOR CONTA

Liner or coating immersion and other tests should beperformed in accordance with ASTM C 868, D 1474, D 1973,D 2197, D 2370, D 2485, D 3456, D 4060, D 5402, and D 5322,with the hazardous material to be contained when using theliner or coating for primary containment.

When using a liner or coating for secondary containment,liner or coating immersion and other tests (Chapter 8) can beperformed with the sump contents, and when a liner is to beused below grade, testing of the liner, for long-term compat-ibility with the substrate it is in contact with, should beperformed.

5.3.2 Thermal effectsLiner or coating materials mayhave a much different coefficient of thermal expansion thanthe concrete support structure or substrate on which they areinstalled. The amount of the potential expansion/contractiondifferential movement between the liner or coating and thesupport structure or substrate should be considered. Thisaffects the design of the liner fastening or anchorage system,the liner joints or seams, and the integrity of the bondbetween the coating and the concrete.

5.3.3 Fasteners and jointsFastening points and jointsare typically the weak links in the integrity of a liningsystem. Every fastening device that penetrates the liner andevery liner joint is a potential leak point. This includes metalbatten strips that mechanically anchor the liner to the supportstructure. Each of these potential leak points needs to besealed. For geomembranes, cap strips of the liner materialare welded over the penetrating fasteners or the nonweldedjoints. When possible, concrete inserts made of liner materialshould be used to fasten the liner to the concrete (Fig. 5.1).

5.3.4 Ultraviolet light resistanceUltraviolet (UV) lightmay attack or degrade the thermoplastic and thermoset linersunless UV light stabilizers were added during the liner manu-facture. If the liner is going to be covered after installation, UVlight protection is not as critical; however, protection may berequired during construction. ASTM D 1435, D 4355, andD 5970 are tests for determining UV degradation of liners.

5.4Inspection and testing of liner and coating installations

5.4.1 GeneralInspection and testing of the liner or coatingmaterial should start right after the selection of the manufacturerof the product and continue through its installation.

Written certification of the manufacturers inspection andtesting should ensure that the liner or coating meets theproject specifications. Similar certification should also berequired from anyone who works on or adds to the productbefore shipping it to the end user. The engineer will usuallywant to inspect the manufacturer or fabrication plant.

Inspection and testing during installation should include,but not be limited to, the following: substrate condition, thecondition of the liner, joints or seams, and fastenings oranchorages.

Nondestructive and destructive testing methods are

available, where applicable, both at the factory and on-site,during and after installation is complete.NMENT OF HAZARDOUS MATERIALS 350.2R-13

5.4.2 Nondestructive test methodsThere were no ASTMstandards for the following tests known to ACI Committee350 at the time of publication of this report.

5.4.2.1 Hydrostatic testHydrostatic test is mainly used totest the integrity and liquid-tightness of the concrete structure.The structure should be hydrostatically tested before theapplication of liners or coatings. Hydrostatic testing is alsoused to test the liner material, when applicable. The linedstructure is filled with water and the level drop measuredover a specified period to detect if any leakage has occurred.The effects of evaporation should be included. See ACI350.1/350.1R for additional guidance on hydrostatic testing,which can take several days.

5.4.2.2 Electric current testsThese tests use an elec-trical current to verify continuity of the liner. These types oftest systems can also be used as leak-detection systems whilethe structure is in service. In spark testing, an electric currentis passed through the liner. A spark should be seen whereverholes are present. This technique is used on thermosets,thermoplastics, and coating systems.

5.4.2.3 X-ray testingX-ray testing is most effective onmetals but may also be used with some success on thermosetsand thermoplastics.

5.4.2.4 Ultrasonic testingUltrasonic testing may beused for metal, thermoset, and thermoplastic materialsand joints.

5.4.2.5 Vacuum testingVacuum testing can be done onjoints or seams to evaluate their integrity. Vacuum testingmay be used on metals, thermosets, and thermoplastic liners.

5.4.2.6 Air-pressure testingAir-pressure testing isdone on systems intended to be air-tight by pressurizing thestructure, or a portion of it, and checking for a loss in pressureover a specified period. Low air pressure is used and the testperformed with extreme caution. The structural designshould consider the test pressure.

5.4.2.7 Air-lance testingThe air-lance testing methoduses a high-pressure air stream directed at the seam in theliner to detect loose edges. This test is used on some types ofgeomembrane installations.

5.4.3 Destructive test methodsDestructive testing ofliners involves cutting test coupons from the joints or seamsand the liner material. These coupons may be subjected to avariety of tests as in Sections 5.4.3.1 through 5.4.3.3.

5.4.3.1 Tensile testTensile tests are used to checktensile strength of the joints, seams, and the material. Thistest is used on metals, thermosets, and thermoplastics.ASTM D 638, D 882, and D 751 are the recommended testmethods for liners.

5.4.3.2 Tear testTear tests are used to check the tearstrength of the material, especially thermoplastics. Themeasurement of tear resistance of liners can be done in anumber of ways. ASTM D 751, D 1004, D 1424, D 1938,and D 2261 all cover the general topic.

5.4.3.3 Peel testThe peel (or bond) test is used to checkthe peel strength of the joints or seams and bond strength ofcoating systems to the substrate. This test is used on thermo-

sets, thermoplastics, and coating systems. ASTM D 413 andD 4437 are the recommended test methods for liner seams.

T350.2R-14 ACI COMMIT

CHAPTER 6SECONDARY CONTAINMENT6.1General

A secondary containment system should prevent anyprimary containment leak from escaping to the environment.The secondary containment system should either retain such aleak until it is removed or should direct the leaked material toa predetermined and controllable drainage channel or sump.

Secondary containment systems are normally dry inservice. These systems include chemical tank farms, truckunloading stations, sumps, drumming rooms, apron slabs,trenches, and other areas where hazardous materials arehandled or transferred.

Secondary containment, even if not required by regula-tion, is also recommended for environmental tanks, sumps,and underground piping systems that store, treat, or transporthazardous materials.

Fig. 6.1Tank with exterior liner and environmental chamber.

Fig. 6.2Tank with interior liner.

Fig. 6.3Tank with exterior liner.The design recommendations for secondary containmentstructures constructed of reinforced concrete are usually lessEE REPORT

stringent than those for primary containment (Sections2.2.4.2, 2.2.6, and 2.2.7). If the secondary containment struc-ture is required to have the same reliability and performanceas the primary containment structure, then the design recom-mendations for primary containment structures should beused for the design of the secondary containment structure.

6.2Secondary containment system featuresChemical compatibilityChemical compatibility is

required to prevent failure of the secondary containmentsystem due to physical contact with both the materialscontained and with the substrate on which they are installed.The secondary containment system does not necessarily need tobe suitable for prolonged contact with the hazardous material,because the hazardous material can be removed and the leak inthe primary containment system located and repaired.

Secondary containment systems should also not fail due toclimatic conditions, settlement, or stress of daily activitysuch as cleaning, flushing, or pedestrian or vehicular traffic.IFC and Federal Regulations for secondary containment ofhazardous materials and other applicable codes, such asNFPA 30 and the UFC for secondary containment offlammable and combustible materials should be consultedfor containment requirements.

6.3Secondary containment materialsThe secondary containment system may be constructed of

the same material as the environmental tank or sump, such asconcrete inside concrete, or constructed of different materials,such as concrete inside polyethylene (Fig. 6.1).

Secondary containment materials include concrete,metals, thermoplastics, thermosets, composites and nativesoils, compacted clays, bentonite, or other soil mixtures withlow permeability (3.28 109 ft/s [1 107 cm/s]). Thesecondary containment system should be designed to thestructural criteria given in this report; however, it may notrequire long-term compatibility with the contents if a spill orleak will be cleaned up within a short time. Because leakageof the secondary containment system may lead to a costlyenvironmental clean up, design and construction techniquesshould make liquid tightness a key consideration.

When small sumps are required, commercially availableprefabricated metal sumps or precast manholes may beapplicable (Fig. 6.2). The prefabricated shapes can also beused to retrofit an existing sump or manhole.

Flexible membrane liners, also known as geomembranes,can be used on the outside of the tank or sump as thesecondary containment (Fig. 6.3). External liners may needprotection from damage by backfilling or from UV rays.

CHAPTER 7LEAK-DETECTION SYSTEMS7.1General

Leak-detection systems are recommended for tanks andsumps that contain a hazardous material or that may do so inthe future. A leak-detection system should be far less expensiveto install during the construction of a new facility than during

the retrofit of an existing facility. It can also help save thecosts of environmental cleanup and regulatory penalties.

ACONCRETE STRUCTURES FOR CONT

Leak-detection systems should detect leakage out of theprimary containment system as soon as feasible after theinitiation of a leak. The detection should occur no later than24 h after initiation of the leakage but before a breach oroverflow occurs in the secondary containment system.

Recommended leak-detection systems are those that rely onvisual inspection of the system and gravity flow of the leakage.Other leak-detection systems use monitoring instruments todetect and can sometimes pinpoint the location of leaks. Theseinstruments range from gas monitors to single probes orinstalled grid systems. The probes and grids measure thermalor electrical conductivity or electrical resistivity.

Any leak-detection system using drainage media shouldbe compatible with the hazardous material contained. Long-term compatibility of the drainage medium may not berequired if the hazardous material can be removed frommedium contact shortly after the leakage occurs. This mayallow for the use of a less-expensive drainage mediummaterial. If leakage enters the drainage medium, the systemshould be thoroughly flushed and cleaned before returningthe medium to service. If cleaning the system is very diffi-cult or economically impractical, replacement of thedrainage medium or conversion to a leak-collection systemshould be considered.

Leak-detection systems are only as good as their generaldesign and the location of the actual leak-detection points ordevices. The designer should take great care in providing a pathof travel through drainage media, or along slabs or trenches, forthe contained material to travel to the point of detection. Theapplicable fire codes for flammable or combustible liquidsshould be consulted. Finally, cathodic protection, if used, canaffect the design of the leak-detection system.

7.2Drainage media materialsDrainage netting, or drainage cell (usually called geonet or

geocell, respectively), is a highly permeable net orcellular material, typically made from polyethylene.Drainage netting may be installed in single or multiple layersoutside of a concrete tank or sump (refer to Fig. 7.1).

A geotextile is placed above the net or cells to act as a filter.This keeps out soil particles or other debris. Nonwovengeotextiles (typically made from polypropylene or polyester)of either the heat bonded or needle-punched variety aretypically used. The heat-bonded materials are stiffer andimpinge less on the geonet or geocell flow channels. Theneedle-punched materials are typically more permeable andless susceptible to clogging. Some nets and cells come withthe geotextile attached to one or both sides and are called acomposite or double composite, respectively.

A granular material with high permeability, such ascoarse-graded sand (size No. 1, ASTM C 404), pea gravel(size No. 8, ASTM C 33), or a mixture of both, can be aneffective drainage medium. These materials are typicallyplaced in layers 6 to 12 in. (150 to 300 mm) thick. A well-graded mixture is more stable underfoot and less affected by

washout than sand or ungraded gravel alone. Not more than5% should pass the No. 200 sieve.INMENT OF HAZARDOUS MATERIALS 350.2R-15

Geotextiles should not be used alone due to the compress-ibility of these materials under sustained loads.

7.3Design and installation of drainage media7.3.1 Under tanks and sumpsGeonet, geocell, or granular

material under tanks and sumps should slope to one or morelow points for collection of any leakage. A minimum slopeof 3% is recommended for earthen or flexible membranesurfaces and 2% for concrete surfaces (Fig. 7.1).

7.3.2 Collection pipesWhere a granular materialdrainage medium is used for a tank or large sump, perforatedcollection pipes are recommended if leaked material musttravel more than 50 ft (15 m). The pipes should be 4 to 6 in.(100 to 150 mm) in diameter and installed radiating from lowpoints. The pipes are covered with a granular envelope. Thegradation of the granular material should be such that theratio D85/Dp 2, where D85 is the sieve opening dimensionsmaller than 85% of the sample, and Dp is the diameter orleast dimension of the pipe perforation. If the drainagemedium includes sand or other fine material, the pea gravelenvelope can be wrapped with a geotextile filter to furtherprotect the pipe from clogging. The geotextile should be thesame as those described in Section 7.2.

Where geonets or geocells are used, collection pipes may

Fig. 7.1Granular material and leak detection system.

Fig. 7.2Double-walled sump with leak detection system.not be needed due to the good flow characteristics of thegeonet or geocell.

TE350.2R-16 ACI COMMIT

On small sumps, where sand or pea gravel is used as thedrainage medium, the collection pipes may be eliminateddue to the short flow distances involved.

7.3.3 RisersManholes or perforated riser pipes shouldbe installed at the low point(s) of the drainage medium orcollection pipes (Fig. 7.2). Using a manhole or riser allowsfor periodic sampling of any liquid or gas that may collect inthe system. The riser should be large enough to allow for themonitoring and sampling device or recovery pumping.

CHAPTER 8REFERENCES8.1Referenced standards and reports

The standards and reports listed below were the latesteditions at the time this document was prepared. Becausethese documents are revised frequently, the reader is advisedto contact the proper sponsoring group if the latest version isdesired.

American Association of State Highway and TransportationOfficials (AASHTO)Standard Specification for Highway Bridges

American Concrete Institute (ACI)201.2R Guide to Durable Concrete216R Determining the Fire Endurance of

Concrete Elements223 Standard Practice for the Use of Shrinkage-

Compensating Concrete224R Control of Cracking in Concrete Structures224.3R Joints in Concrete Construction301 Specifications for Structural Concrete305R Hot Weather Concreting306.1 Standard Specification for Cold Weather

Concreting306R Cold Weather Concreting308R Standard Practice for Curing Concrete308.1 Standard Specification for Curing Concrete.311.1R SP-2: ACI Manual of Concrete Inspection311.4R Guide for Concrete Inspection311.5R Guide for Concrete Plant Inspection and

Testing of Ready-Mixed Concrete350/350R Code Requirements for Environmental

Engineering Concrete Structures andCommentary

350.1/350.1R Tightness Testing of Environmental Engi-neering Concrete Structures and Commentary

372R Design and Construction of Circular Wire-and Strand-Wrapped Prestressed ConcreteStructures

373R Design and Construction of CircularPrestressed Concrete Structures withCircumferential Tendons

504R Guide to Joint Sealants for ConcreteStructures

515.1R Guide To The Use of Waterproofing,

Dampproofing, Protective and DecorativeBarrier Systems For ConcreteE REPORT

ASTM InternationalC 33 Specification for Concrete AggregatesC 404 Specification for Aggregates for Masonry

GroutC 811 Specification for Preparation of Concrete

for Application of Chemical-ResistantResin Monolithic Surfacings

C 868 Test Method for Chemical Resistance ofProtective Linings

C 913 Specification for Precast Concrete Waterand Wastewater Structures

C 920 Specification for Elastomeric Joint SealantsD 413 Standard Test Methods for Rubber Property-

Adhesion to Flexible SubstrateD 638 Standard Test Method for Tensile Properties

of PlasticsD 751 Standard Test Method for Coated FabricsD 882 Standard Test Method for Tensile Proper-

ties of Thin Plastic SheetingD 1004 Standard Test Method for Initial Tear Resis-

tance of Plastic Film and SheetingD 1424 Standard Test Method for Tearing Strength

of Fabrics by Falling-Pendulum Type(Elmendorf) Apparatus

D 1435 Standard Practice for Outdoor Weatheringof Plastics

D 1474 Test Methods for Indentation Hardness forOrganic Coatings

D 1938 Standard Test Method for Tear-PropagationResistance of Plastic Film and ThinSheeting by a Single Tear Method

D 1973 Guide for Design of a Liner System forContainment of Wastes

D 2197 Test Method for Adhesion of Organic Coat-ings by Scrape Adhesion

D 2261 Standard Test Method for Tearing Strength ofFabrics by the Tongue (Single Rib) Procedure(Constant-Rate-of-Expansion Tensile TestingMachine)

D 2370 Test Method for Tensile Properties ofOrganic Coatings

D 2485 Test Method for Evaluating Coatings forHigh Temperature Service

D 3456 Practice for Determining by Exterior Expo-sure Tests the Susceptibility of Paint Filmsto Microbiological Attack

D 4060 Test Method for Abrasion Resistance ofOrganic Coatings by Taber Abraser

D 4355 Standard Test Method for Deterioration ofGeotextiles from Exposure to UltravioletLights and Water

D 4437 Standard Practice for Determining theIntegrity of Field Seams Used in JoiningFlexible Polymeric Sheet Geomembranes

D 5402 Practice for Assessing the Solvent Resis-

tance of Organic Coatings Using SolventRubs

CONCRETE STRUCTURES FOR CONTAINMENT OF HAZARDOUS MATERIALS 350.2R-17

D 5322 Practice for Immersion Procedures forEvaluating the Chemical Resistance ofGeosynthetics to Liquids

D 5970 Standard Practice for Deterioration ofGeotextiles from Outdoor Exposure

E 329 Standard Specification for AgenciesEngaged in the Testing and/or Inspection ofMaterials Used In Construction

American Water Works Association (AWWA)D110 AWWA Standard for Wire and Strand

Wrapped Circular Prestressed ConcreteWater Tanks

D115 AWWA Standard for Circular PrestressedConcrete Water Tanks With Circumferen-tial Tendons

National Fire Protection Association (NFPA)NFPA 30 Flammable and Combustible Liquids CodeNFPA 49 Hazardous Chemical Data

The above publications may be obtained from thefollowing organizations:

American Association of State Highway and TransportationOfficials (AASHTO)

444 North Capitol Street, N.W., Suite 249Washington, D.C. 20001

American Concrete Institute (ACI)P.O. Box 9094Farmington Hills, MI 48333-9094

ASTM International100 Barr Harbor DriveWest Conshohocken, PA 19428-2959

American Water Works Association (AWWA)6666 West Quincy Ave.Denver, CO 80235

National Fire Protection Association (NFPA)Batterymarch ParkP.O. Box 9101Quincy, MA 02269-9959

8.2Cited referencesCRSI, 1980, Reinforced Concrete Fire Resistance, First

Edition, Concrete Reinforcing Steel Institute, Schaumburg,Ill., 256 pp.

Zwiers, R. I., and Morgan, B. J., 1989, Performance ofConcrete Members Subjected to Large Hydrocarbon PoolFires, PCI Journal, V. 34, No. 1, Jan.-Feb., pp. 120-135.

MAIN MENUCONTENTSCHAPTER 1GENERAL 1.1- Scope1.2Definitions1.3Types of materials

CHAPTER 2CONCRETE DESIGN AND PROPORTIONING 2.1- General2.2DesignTable 2.1Wall thickness and reinforcement locations based on concrete placement consideration2.3Concrete cover2.4Exposure2.5Concrete mixture proportions2.6Fiber-reinforced concrete

CHAPTER 3WATERSTOPS, SEALANTS, AND JOINTS 3.1- Waterstops3.2Joint sealants3.3Joints

CHAPTER 4CONSTRUCTION CONSIDERATIONS 4.1- Sump construction techniques4.2Curing and protection4.3Inspection

CHAPTER 5LINERS AND COATINGS 5.1- Liners5.2Coatings5.3Selection considerations for liners and coatings5.4Inspection and testing of liner and coating installations

CHAPTER 6SECONDARY CONTAINMENT 6.1- General6.2Secondary containment system features6.3Secondary containment materials

CHAPTER 7LEAK-DETECTION SYSTEMS 7.1- General7.2Drainage media materials7.3Design and installation of drainage media

CHAPTER 8REFERENCES 8.1- Referenced standards and reports8.2Cited references