Atch_22 _ASTM_C478_manholes.pdf

Designation: C478 − 12a

Standard Specification for Precast Reinforced Concrete Manhole Sections1

This standard is issued under the fixed designation C478; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.

This standard has been approved for use by agencies of the Department of Defense.

PART I—GENERAL

1. Scope

1.1 This specification covers the manufacture and purchase

requirements of products used for the assembly and construc-tion of circular vertical precast reinforced concrete manholes and structures used in sewer, drainage, and water works.

1.2 Part I, Sections 1-11, of this specification presents

general requirements and requirements that are common to each precast concrete product covered by this specification.

1.3 Part II of this specification presents specific require-

ments for each manhole product in the following sections:

Product Section Grade Rings 12 Flat Slab Tops 13 Risers and Conical Tops 14 Base Sections 15 Steps and Ladders 16

NOTE 1—Future products will to be included in Part II in a future revision of this specification.

1.4 This specification is the inch-pound companion to

Specification C478M; therefore, no SI equivalents are pre-sented in the specification.

NOTE 2—This specification is a manufacturing and purchase specifica-tion only and does not include requirements for backfill, or the relation-ship between field load conditions and the strength requirements of the manhole products and appurtenances. Experience has shown, however, that the successful performance of this product depends upon the proper selection of the product strength, type of foundation and backfill, and care in the field installation of the manhole products and connecting pipes. The owner of the project for which these products are specified herein is cautioned to require inspection at the construction site.

2. Referenced Documents

2.1 ASTM Standards:2

A615/A615M Specification for Deformed and Plain Carbon- Steel Bars for Concrete Reinforcement

A706/A706M Specification for Low-Alloy Steel Deformed and Plain Bars for Concrete Reinforcement

A1064/A1064M Specification for Steel Wire and Welded Wire Reinforcement, Plain and Deformed, for Concrete

C33 Specification for Concrete Aggregates C39/C39M Test Method for Compressive Strength of Cylin-drical Concrete Specimens C150 Specification for Portland Cement C260 Specification for Air-Entraining Admixtures for Con-crete C309 Specification for Liquid Membrane-Forming Com-pounds for Curing Concrete C494/C494M Specification for Chemical Admixtures for

Concrete C497 Test Methods for Concrete Pipe, Manhole Sections, or

Tile C595 Specification for Blended Hydraulic Cements C618 Specification for Coal Fly Ash and Raw or Calcined

Natural Pozzolan for Use in Concrete C822 Terminology Relating to Concrete Pipe and Related

Products C989 Specification for Slag Cement for Use in Concrete and

Mortars C1017/C1017M Specification for Chemical Admixtures for

Use in Producing Flowing Concrete

2.2 ACI Standard:3

318 Building Code, Requirements for Reinforced Concrete

3. Terminology

3.1 Definitions—For definitions of terms relating to precast

reinforced concrete manholes, see Terminology C822.

1 This specification is under the jurisdiction of ASTM Committee C13 on Concrete Pipe and is the direct responsibility of Subcommittee C13.06 on Manholes and Specials.

Current edition approved Oct. 1, 2012. Published October 2012. Originally approved in 1961. Last previous edition approved in 2012 as C478 – 12. DOI:

10.1520/C0478-12A.

2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.

3 Available from American Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333-9094, http://www.aci-int.org.

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4. Materials and Manufacture

4.1 General material requirements for precast reinforced

concrete manhole products are presented in 4.1.1-4.1.8. Other materials or additional requirements for a product, if any, are covered in the Part II section for that specific product.

4.1.1 Reinforced Concrete—Reinforced concrete shall con-

sist of cementitious materials, mineral aggregates, and water, in which steel reinforcement has been embedded in such a manner so that the steel reinforcement and concrete act together.

4.1.2 Cementitious Materials:

4.1.2.1 Cement—Cement shall conform to the requirements

for portland cement of Specification C150, or shall be portland blast-furnace slag cement or portland-pozzolan cement con-forming to Specification C595, except that the pozzolan constituent of the Type IP portland-pozzolan cement shall be fly ash.

4.1.2.2 Fly Ash—Fly ash shall conform to the requirements

of Class F or Class C of Specification C618.

4.1.2.3 Slag Cement—Slag cement shall conform to the

requirements of Grade 100 or 120 of Specification C989.

4.1.3 Allowable Combinations of Cementitious Materials—

The combination of cementitious materials used in the concrete shall be one of the following:

4.1.3.1 Portland cement only,

4.1.3.2 Portland blast-furnace slag cement only,

4.1.3.3 Portland pozzolan cement only,

4.1.3.4 A combination of Portland cement and slag cement,

4.1.3.5 A combination of Portland cement and fly ash, or

4.1.3.6 A combination of Portland cement, slag cement (not

to exceed 25 % of the total cementitious weight) and fly ash (not to exceed 25 % of the total cementitious weight).

4.1.4 Aggregates—Aggregates shall conform to Specifica-

tion C33, except that the requirements for gradation shall not apply.

4.1.5 Admixtures and Blends—The following admixtures

and blends are allowable:

4.1.5.1 Air-entraining admixture conforming to Specifica-

tion C260;

4.1.5.2 Chemical admixture conforming to Specification

C494/C494M;

4.1.5.3 Chemical admixture for use in producing flowing

concrete conforming to Specification C1017/C1017M;

4.1.5.4 Chemical admixture or blend approved by the

owner.

4.1.6 Steel Reinforcement—Reinforcement shall consist of

wire and welded wire conforming to Specification A1064/ A1064M or of bars conforming to Specification A615/A615M, Grade 40 or 60, or Specification A706/A706M, Grade 60.

4.1.7 Secondary Synthetic Fiber—Collated fibrillated poly-

propylene virgin fibers shall not be prohibited when used in steel reinforced concrete manholes as a non-structural manu-facturing enhancement. Only fibers designed and manufactured specifically for use in concrete and so certified by the manu-facturer shall be accepted.

4.1.8 Other Materials—Other materials required for a prod-

uct and not covered in Section 4 will be covered in the Part II section for that specific product.

5. Design

5.1 Design requirements for a product are prescribed in the

specific Part II section for that product.

5.1.1 The minimum compressive strength of concrete man-

hole products covered by this specification shall be 4000 psi unless specified otherwise in Part II of this specification.

5.2 Modified or Special Design

5.2.1 Manufacturers are not prohibited from submitting to

the owner, for approval prior to manufacture, designs other than those prescribed in the specific section for a product. If such approval is obtained, then the product shall meet all the tests and performance requirements specified by the owner in accordance with the appropriate sections on manufacture and physical requirements.

5.2.2 If permitted by the owner, the manufacturer is not

prohibited from requesting approval of designs of special sections, such as reducers, tees, and bases.

6. Reinforcement

6.1 This section presents requirements for reinforcement

cover, continuity, laps, welds, and splices. Other reinforcement requirements are presented in Section 4, and any additional requirements are given in the Part II section for a specific product.

6.2 Cover—The exposure of the ends of reinforcement, stirrups or spacers used to position the reinforcement during placement of the concrete shall not be cause for rejection.

6.3 Continuity—The continuity of the circumferential rein-

forcement shall not be destroyed during the manufacture of the product, except when lift holes or pipe openings are provided in the product.

6.4 Welded Steel Cage Laps, Welds, and Splices:

6.4.1 If splices are not welded, the reinforcement shall be

lapped not less than 20 diameters for deformed bars, and 40 diameters for plain bars and cold-drawn wire. In addition, where lapped cages of welded wire fabric are used without welding, the lap shall contain a longitudinal wire.

6.4.2 When splices are welded and are not lapped to the

minimum requirements in 6.4.1, pull tests of representative specimens shall develop at least 50 % of the minimum speci-fied strength of the steel, and there shall be a minimum lap of 2 in. For butt welded splices in bars or wire, permitted only with helically wound cages, pull tests of representative speci-mens shall develop at least 75 % of the minimum specified strength of the steel.

6.5 Steel Hoop Splices—A representative sample steel hoop

with welded splices shall develop at least 50 % of the mini-mum specified strength of the steel, and there shall be a minimum lap of 2 in. For butt welded splices, the representa-tive steel hoop sample shall develop at least 75 % of the minimum specified strength of the steel.

7. Precast Concrete Manufacture

7.1 Mixture—The aggregates shall be sized, graded, proportioned, and mixed with such proportions of cementitious materials and water as will produce a thoroughly-mixed

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7.2 Curing—Concrete products shall be subjected to any

one of the methods of curing prescribed in 7.2.1-7.2.4 or to any other method or combination of methods approved by the owner that will give satisfactory results.

7.2.1 Steam Curing—Concrete products are placed in a

curing chamber, free of outside drafts, and cured in a moist atmosphere maintained by the injection of steam for such time and such temperatures as needed to enable the products to meet the strength requirements. The curing chamber shall be so constructed as to allow full circulation of the steam around the entire product.

7.2.2 Water Curing—Concrete products are water-cured by

covering with water-saturated material, or by a system of perforated pipes, mechanical sprinklers, porous hose, or by any other approved method that will keep the products moist during the curing period.

7.2.3 Sealing Membrane—A sealing membrane conforming

to the requirements of Specification C309 is applied and shall be left intact until the required concrete strength requirements are met. The concrete at the time of application of the membrane shall be within 10°F of the atmospheric tempera-ture. All concrete surfaces shall be kept moist prior to the application of the membrane and shall be damp when the membrane is applied.

7.2.4 The manufacturer is not prohibited from combining

the methods prescribed in 7.2.1-7.2.3 provided the required concrete compressive strength is attained.

8. Acceptance

8.1 Acceptance Procedures:

8.1.1 Unless otherwise designated by the owner at the time

of, or before, placing an order, acceptance procedures for precast reinforced concrete manhole products shall be as specified in the Part II section for a particular product, and shall not be prohibited from consisting of one or more of the following:

8.1.1.1 Acceptance of a product on the basis of tests of

materials, including concrete compressive strength and absorp-tion.

8.1.1.2 Acceptance of a product on the basis of inspection of the finished product, including amount and placement of reinforcement to determine conformance with the design prescribed under this specification, and freedom from defects.

8.2 Test Methods:

8.2.1 Concrete Compressive Strength Test:

8.2.1.1 Type of Specimen—Compression tests for satisfying

the minimum specified concrete strength requirement shall be made on either concrete cylinders or, at the option of the manufacturer, on cores cut from the concrete manhole product.

8.2.1.2 Compression Testing of Cylinders—Cylinders shall

be made in accordance with Test Methods C497, and shall be tested in accordance with Test Method C39/C39M. For man-hole products, an owner shall not be prohibited from requiring concrete compressive tests on cylinder specimens numbering in the amount of 5 % of the total order of a manhole product, but not to exceed two cylinders for each day’s production. The average compressive strength of all cylinders tested shall be equal to or greater than the specified strength of the concrete.

Not more than 10 % of the cylinders tested shall fall below the specified strength of the concrete. In no case shall any cylinder tested fall below 80 % of the specified strength of the concrete.

8.2.1.3 Compression Testing of Cores—Cores shall be cut

from the concrete manhole product and tested in accordance with Test Methods C497, except that the requirements for moisture conditioning shall not apply. One core shall be taken from a manhole product selected at random from each day’s production run of a single concrete strength. When the concrete compressive strength of the core is equal to or greater than 80 % of the specified strength of the concrete, the concrete strength of the production run is acceptable. If the core does not meet the preceding concrete strength requirement, another core from the same manhole product shall be taken and tested.

8.2.1.4 If the concrete compressive strength of the recore is equal to or greater than 80 % of the specified strength of the concrete, the concrete strength of the production run is accept-able. If the recore does not meet the preceding concrete strength requirement, that manhole product shall be rejected.

Two manhole products from the remainder of the day’s production run shall be selected at random and one core taken from each manhole product and tested. When the average concrete strength of the two cores is equal to or greater than 80 % of the specified strength of the concrete with no core below 75 % of the specified strength of the concrete, the concrete strength of the day’s production run shall be accept-able.

8.2.1.5 If the concrete strength of the two cores does not

meet the preceding concrete strength requirement, then the remainder of the day’s production run shall be either rejected, or, at the option of the manufacturer, each manhole product of the remainder of the day’s production run is not prohibited from being cored and accepted individually.

8.2.1.6 Plugging Core Holes—Core holes on accepted con-

crete manhole products shall be plugged and sealed by the manufacturer in a manner such that the manhole products will meet all of the requirements of this specification. Manhole sections so sealed shall be considered as satisfactory for use.

8.2.2 Absorption Test:

8.2.2.1 The absorption of a specimen from a concrete

product, as determined in Test Methods C497, shall not exceed 9 % of the dry mass for Test Method A procedure or 8.5 % for Test Method B procedure. All specimens shall be free of visible cracks and shall represent the full thickness of the product.

8.2.2.2 Specimens for Test Method B shall meet the require-

ments of Test Methods C497.

8.2.2.3 Each specimen tested by Test Method A shall have a

minimum weight of 2.2 lbs.

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8.2.2.4 When the initial absorption specimen from a con-

crete product fails to conform to this specification, the absorp-tion test shall be made on another specimen from the same product and the results of the retest shall be substituted for the original test results.

8.2.3 Retests—When not more than 20 % of the concrete

test specimens tested under either 8.2.2.1 or 8.2.2.2 fail to pass the requirements of this specification, the manufacturer is not prohibited from culling his stock and eliminating whatever quantity of product he desires and shall so mark the culled product that they will not be shipped for the order. The required tests shall be made on the balance of the order and the products shall be accepted if in conformance with the requirements of this specification.

8.3 Test Equipment—Every manufacturer furnishing man-

hole products under this specification shall furnish all facilities and personnel necessary to carry out the tests required for acceptance.

9. Repairs

9.1 Repair of manhole products shall not be prohibited, if

necessary, because of imperfections in manufacture or damage during handling, and will be acceptable if, in the opinion of the owner, the repaired products conform to the requirements of this specification.

10. Inspection

10.1 The quality of materials, the process of manufacture, and the finished manhole products shall be subject to inspec-tion and approval by the owner.

11. Product Marking

11.1 The following information shall be legibly marked on

each precast concrete product:

11.1.1 Specification and product designation: MH for man-

hole base, riser, conical tops, and grade rings,

11.1.2 Date of manufacture, and

11.1.3 Name or trademark of the manufacturer.

11.2 Marking shall be indented into the concrete or shall be

painted thereon with waterproof paint.

PART II—PRODUCTS

12. Grade Rings

12.1 Scope—This section covers precast reinforced concrete

grade rings used for final adjustment of manholes to grade.

12.2 Acceptance—Acceptability of grade rings covered by

this specification shall be determined by the results of such tests of materials as are required by Section 4; by compressive strength tests on concrete cores or concrete cylinders required by Section 8; and by inspection of the finished product, including amount and placement of reinforcement as pre-scribed by 12.4, 12.5, and 12.6, to determine its conformance with the design prescribed under this specification and its freedom from defects.

12.3 Design—The minimum wall thickness shall be one

twelfth of the internal diameter of the grade ring or 4 in., whichever is greater.

12.3.1 Joints—Grade rings are not required to have the joint

formed with male and female ends.

12.4 Circumferential Reinforcement :

12.4.1 The circumferential reinforcement shall have an

equivalent area of not less than 0.07 in.2/vertical ft, but not less than 0.024 in.2 in any one grade ring.

12.4.2 The circumferential reinforcement shall be one line

in the center third of the wall of the grade ring.

12.5 Permissible Variations:

12.5.1 Internal Diameter—The internal diameter of grade

rings shall not vary more than 6 1 %.

12.5.2 Wall Thickness—The wall thickness of grade rings

shall be not less than that prescribed in the design by more than 5 % or 6 3⁄16 in., whichever is greater. A wall thickness greater than that prescribed in the design shall not be cause for rejection.

12.5.3 Height of Two Opposite Sides—Variations in laying

height of two opposite sides of grade rings shall be not more than 1⁄4 in.

12.5.4 Height of Grade Ring—The underrun in height of a

grade ring shall be not more than 1⁄8 in./ft of height.

12.5.5 Position of Reinforcement—For grade rings with a

4-in. wall thickness, the maximum variation in the design position of circumferential reinforcement from that described in 12.4.1 shall be 610 % of the wall thickness or 61⁄4 in., whichever is greater. For grade rings with a wall thickness greater than 4 in., the maximum variation from the design position of reinforcement shall be 610 % of the wall thickness or 65⁄8 in., whichever is the lesser. In no case, however, shall the cover over the reinforcement be less than 3⁄4 in. The preceding minimum cover limitation does not apply to the mating surfaces of the joint.

12.5.6 Area of Reinforcement—Steel reinforcement areas

that are 0.005 in.2/linear ft less than called for by design shall be considered as meeting the required steel reinforcement area.

12.6 Rejection:

12.6.1 Grade rings shall be subject to rejection for failure to conform to any of the specification requirements. In addition, an individual grade ring shall be subject to rejection because of any of the following:

12.6.1.1 Fractures or cracks passing through the wall, ex-

cept for a single end crack that does not exceed the depth of the joint.

12.6.1.2 Defects that indicate mixing and molding not in

compliance with 7.1 or surface defects indicating honey-combed or open texture that would adversely affect the function of the grade ring.

12.6.1.3 The planes of the ends are not perpendicular to the

longitudinal axis of the grade ring, within the limits of permissible variations prescribed in 12.5.

12.6.1.4 Damaged or cracked ends, where such damage

would prevent making a satisfactory joint.

12.6.1.5 Any continuous crack having a surface width of

0.01 in. or more and extending for a length of 12 in. or more, regardless of position in the wall.

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13. Flat Slab Tops

13.1 Scope—This section covers precast reinforced concrete

flat slab tops used in the construction of manholes for use in sewer, drainage, and water works.

13.2 Acceptance:

13.2.1 Acceptability of flat slab tops shall be determined by the results of such tests of materials as are required by Section 4; by compressive strength tests on concrete cores or concrete cylinders required by Section 8; and by inspection of the finished product, including amount and placement of reinforce-ment as prescribed by 13.4 and 13.6, to determine its confor-mance with the design prescribed under this specification and its freedom from defects.

13.2.2 Unless otherwise designated by the owner at the time

of, or before, placing an order, two separate and alternative methods of acceptance are permitted for flat slab top manufac-turer designs, in addition to tests of materials and inspection required in 13.2.1.

13.2.2.1 Acceptance on the Basis of Proof-of-Design Test—

Acceptance of flat slab tops on the basis of the results of a proof-of-design test performed in accordance with 13.5 in lieu of submission of design calculations and detailed drawings.

13.2.2.2 Acceptance on the Basis of Rational Design—

Acceptance of flat slab tops on the basis of design calculations by a rational method and detailed drawings.

13.3 Design:

13.3.1 The basis of flat slab top designs shall be the

appropriate sections of the latest edition of ACI 318.

13.3.2 Flat slab tops shall have a minimum thickness of 6 in.

for risers up to and including 48 in. in diameter and 8 in. for larger diameters.

13.3.3 The flat slab top access opening shall be a minimum

of 24 in. in diameter.

13.3.4 Joint—The reinforced concrete flat slab top shall be

formed with or without a male or female end so that when the manhole base, riser and top section are assembled, they will make a continuous and uniform manhole compatible with the tolerances given in 13.6.

13.3.4.1 Joints are designed to perform in axial compres-

sion; therefore, shear or load testing of the joint is not required.

13.4 Reinforcement:

13.4.1 Flat slab tops manufactured with a joint or with other indication of the top or bottom of the slab shall be manufac-tured with one layer of reinforcement placed near the bottom surface so that the protective cover over the reinforcement shall be 1 in.

13.4.2 Flat slab tops manufactured without a joint or with-

out other indication of the top or bottom of the slab shall be manufactured with two layers of steel reinforcement, one located near the bottom surface and one near the top surface so that the protective cover over each layer is 1 in.

13.4.3 A layer of reinforcement shall have a minimum area

of 0.12 in.2/linear ft in both directions.

13.4.4 Openings in flat slab tops shall be additionally

reinforced with a minimum of the equivalent of 0.20 in.2 of steel at 90°. Straight rods used to reinforce openings shall have a minimum length equal to the diameter of the opening plus 2 in.

13.5 Physical Requirements—Physical requirements for

tests shall conform to the requirements of Section 8.

13.5.1 Proof-of-Design Test:

13.5.1.1 If 13.2.2.2 has been designated as the basis of

acceptance, one flat slab top for each design shall be tested unless the owner has indicated otherwise.

13.5.1.2 The flat slab top proof-of-design test procedures

shall be in accordance with Test Methods C497.

13.5.1.3 The ultimate test load shall be the sum of at least

130 % of the dead load on the slab plus at lest 217 % of the live-plus impact load on the slab. Dead load is the weight of the column of earth over the slab plus the weight of the riser supported by the slab. Live load is the maximum anticipated wheel load that may be transmitted through the riser to the slab.

13.5.1.4 The flat slab top shall be acceptable if it supports the required ultimate test load without failure. Ultimate strength failure is defined as the inability of the slab to resist an increase in the applied load.

13.5.1.5 When agreed upon by the owner and manufacturer, the flat slab top shall be acceptable based on certified copies of the results of tests performed on identical flat slab tops instead of requiring new proof-of-design acceptance tests.

13.6 Permissible Variations:

13.6.1 Internal Diameter—The internal diameter of the flat

slab tops entrance hole shall not vary more than 61 %.

13.6.2 Thickness—The thickness of flat slab tops shall be

not less than that prescribed in the design by more than 5 % or 63⁄16 in., whichever is greater. A thickness greater than that prescribed in the design shall not be cause for rejection.

13.6.3 Length of Two Opposite Sides—Variations in lengths

of two opposite sides of flat slab tops shall be not more than 1⁄4 in.

13.6.4 Length—The underrun in length of a flat slab top

shall be not more than 1⁄8 in./ft of length.

13.6.5 Position of Reinforcement—For flat slab tops with

less than a 6 in. thickness, the maximum variation in the position of reinforcement from that prescribed in 13.5 shall be 610 % of the thickness or 61⁄4 in., whichever is greater. For flat slab tops with a thickness greater than 6 in., the maximum variation shall be 610 % of the thickness or 65 ⁄8 in., whichever is the lesser. In no case, however, shall the cover over the reinforcement be less than 3⁄4 in.

13.6.6 Area of Reinforcement—Steel reinforcement areas

that are 0.005 in2/linear ft less than called for by design shall be considered as meeting the required steel reinforcement area.

13.7 Rejection:

13.7.1 Flat slab tops shall be subject to rejection for failure to conform to any of the specification requirements. In addition, an individual flat slab top of shall be subject to rejection because of any of the following:

13.7.1.1 Fractures or cracks passing through the wall, ex-

cept for a single end crack that does not exceed the depth of the joint.

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13.7.1.2 Defects that indicate mixing and molding not in

compliance with 7.1 or surface defects indicating honey-combed or open texture that would adversely affect the function of the flat slab top.

13.7.1.3 The planes of the ends are not perpendicular to the

longitudinal axis of the flat slab top, within the limits of permissible variations prescribed in 13.6.

13.7.1.4 Damaged or cracked ends, where such damage

would prevent making a satisfactory joint.

13.7.1.5 Any continuous crack having a surface width of

0.01 in, or more and extending for a length of 12 in. or more, regardless of position in the slab.

14. Risers and Conical Tops

14.1 Scope—This section covers precast reinforced concrete

risers and conical tops used in construction of manholes for use in sewer, drainage, and water works.

14.2 Acceptance—Acceptability of risers and conical tops

covered by this specification shall be determined by the results of such tests of materials as are required by Section 4; by compressive strength tests on concrete cores or concrete cylinders required by Section 8; and by inspection of the finished product, including the amount of reinforcement as prescribed by either 14.4 or 14.5 and meeting permissible variations as prescribed by 14.7, to determine its conformance with the design prescribed under this specification and its freedom from defects.

14.3 Design—The minimum wall thickness shall be one

twelfth of the largest internal diameter of the riser or conical top.

14.4 Welded Steel Cage Reinforcement :

14.4.1 Circumferential Reinforcement for Risers and Coni-

cal Tops:

14.4.1.1 Circumferential reinforcement shall consist of ei-

ther one or two lines of steel. The total area of reinforcement per vertical foot shall be not less than 0.0025 times the internal diameter in inches.

14.4.1.2 A line of circumferential reinforcement for any

given total area may be composed of two layers if the layers are not separated by more than the thickness of one cross member plus 1⁄4 in. The two layers shall be tied together to form a single cage. All other specification requirements such as laps, welds, and tolerances of placement in the wall of the riser or conical top shall apply to this method of fabricating a line of reinforcement.

14.4.1.3 Where one line of circumferential reinforcement is

used, it shall be placed in the center third of the wall. The protective cover over the circumferential reinforcement in the wall shall be no less than 3⁄4 in. in accordance with 14.7.

14.4.1.4 Where two lines of circumferential reinforcement

are used, each line shall be so placed that the protective covering over the circumferential reinforcement in the wall shall be 1 in.

14.4.1.5 The location of the reinforcement shall be subject

to the permissible variations in dimensions prescribed in 14.7.

14.4.1.6 The spacing center to center of circumferential

reinforcement in a cage shall not exceed 6 in.

14.4.2 Longitudinal Members—Each line of circumferential

reinforcement shall be assembled into a cage that shall contain sufficient longitudinal bars or members to maintain the rein-forcement in shape and position within the form to comply with permissible variations in 14.7.

14.4.3 Joint Reinforcement—The tongue or groove of the

joint is not required to contain circumferential reinforcement.

14.5 Steel Hoop Reinforcement:

14.5.1 Continuous Steel Hoop Reinforcement for Risers and

Conical Tops Up to and Including 48 in. in Diameter:

NOTE 3—Care shall be taken to ensure that none of the steel hoop reinforcement is cut prior to installation of the riser or conical top.

14.5.1.1 Circumferential reinforcement for manhole risers

and conical tops up to and including 24 in. in height shall consist of no less than two hoops of steel wire or reinforcing bars. The steel hoop shall have a minimum cross-sectional diameter of 0.250 in. and shall be located in each end quarter of the riser or conical top, with a minimum distance of 1 in.

from the shoulder of the riser or conical top.

14.5.1.2 Circumferential reinforcement for manhole risers

and conical tops greater in height than 24 in. and up to and including 48 in. in height shall consist of no less than three hoops of steel wire or reinforcing bars. The steel hoops shall have a minimum cross-sectional diameter of 0.250 in. and shall have a hoop located in each end quarter of the riser or conical top with a minimum distance of 1 in. from the shoulder of the riser or conical top. The third, or middle, hoop shall be located from the shoulder of the riser or conical top a distance equal to one-half the section height 66 in.

14.5.1.3 Circumferential reinforcement for manhole risers

and conical tops greater in height than 48 in. and up to and including 72 in. in height shall consist of no less than four hoops of steel wire or reinforcing bars spaced equally 63 in.

throughout the height of the riser or conical top. The steel hoops shall have a minimum cross-sectional diameter of 0.250

in. and shall have a hoop located in each end quarter of the riser or conical top with a minimum distance of 1 in. from the shoulder of the riser or conical top.

14.5.1.4 The hoop reinforcement shall be placed in the

center third of the riser wall or conical top. The concrete cover over the hoop reinforcement in the wall of the section shall be no less than 3⁄4 in. in accordance with 14.7.

14.5.1.5 For riser sections with openings, this section 14.5 is not permitted.

14.5.2 Joint Reinforcement—The tongue or groove of the

joint is not required to contain circumferential reinforcement.

14.6 Joints—Precast reinforced concrete risers and conical

tops shall be designed and manufactured with male and female ends, so that the assembled manhole base, riser and conical top shall make a continuous and uniform manhole, compatible with the tolerances given in 14.7.

14.6.1 Joints are designed to perform in axial compression;

therefore, shear or load testing of the joint is not required.

14.7 Permissible Variations:

14.7.1 Internal Diameter—The internal diameter of risers

and conical tops shall not vary more than 1 %.

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14.7.2 Wall Thickness—The wall thickness of risers and

conical tops shall be not less than that prescribed in the design by more than 5 % or 63⁄16 in., whichever is greater. A wall thickness greater than that prescribed in the design shall not be cause for rejection.

14.7.3 Height of Two Opposite Sides—Variations in laying

heights of two opposite sides of risers or conical tops shall be not more than 5⁄8 in.

14.7.4 Height of Section—The underrun in height of a riser

or conical top shall be not more than 1⁄4 in./ft of height with a maximum of 1⁄2 in. in any one section.

14.7.5 Position of Reinforcement—For risers or conical tops

with a 4 in. wall thickness or less, the maximum variation in the position of reinforcement from that prescribed in 14.5 and

14.6 shall be 610 % of the wall thickness or 61⁄4 in., whichever is greater. For sections with a wall thickness greater than 4 in., the maximum variation in the position of reinforce-ment shall be 610 % of the wall thickness or 65⁄8 in., whichever is the lesser. In no case, however, shall the cover over the reinforcement be less than 3⁄4 in. The preceding minimum cover limitation does not apply to the mating surfaces of the joint.

14.7.6 Area of Reinforcement—Steel reinforcement areas

that are 0.005 in.2/linear ft less than called for by design shall be considered as meeting the required steel reinforcement area.

14.8 Rejection:

14.8.1 Risers and conical tops shall be subject to rejection

for failure to conform to any of the specification requirements.

In addition, an individual riser or conical top shall be subject to rejection because of any of the following:

14.8.1.1 Fractures or cracks passing through the wall, ex-

cept for a single end crack that does not exceed the depth of the joint.

14.8.1.2 Defects that indicate mixing and molding not in

compliance with 7.1 or surface defects indicating honey-combed or open texture that would adversely affect the function of the riser or conical top.

14.8.1.3 The planes of the ends are not perpendicular to the

longitudinal axis of the riser or conical top, within the limits of permissible variations prescribed in 14.7.

14.8.1.4 Damaged or cracked ends, where such damage

would prevent making a satisfactory joint.

14.8.1.5 Any continuous crack having a surface width of

0.01 in., or more and extending for a length of 12 in. or more, regardless of position in the wall.

15. Base Sections

15.1 Scope—This section covers three types of precast

concrete base sections manufactured for use in the construction of manholes used in sewer, drainage, and water works. The three types of base sections are (1) a base with riser wall and base slab cast monolithically as a single unit with or without benching, (2) a base consisting of a riser section with a secondary poured integral base slab, with or without benching, and (3) a two-piece base consisting of a separate precast base slab and a riser section with a sealed joint between the two. The riser portions of a base section shall meet all the requirements of Section 14.

15.2 Acceptance—Acceptability of base sections covered by

this specification shall be determined by the results of such tests of materials as are required by Section 4; by compressive strength tests on concrete cores or concrete cylinders required by Section 8; and by inspection of the finished product, including amount and placement of reinforcement as pre-scribed by 15.4 and 15.6, to determine conformance with the design prescribed under this specification and its freedom from defects.

15.3 Design:

15.3.1 The basis of base slab designs shall be the appropri-

ate sections of the latest edition of ACI 318.

15.3.2 Base slabs shall have a minimum thickness of 6 in.

for manholes up to and including 48 in. in diameter and 8 in.

for larger diameter manholes.

15.3.2.1 When a base section is precast monolithically with

a benched invert, the minimum concrete thickness from the invert to bottom of the base slab shall be 4 in.

15.3.3 Benched inverts cast either monolithically with the

base section or as a secondary casting in a cured base section shall have the following minimum dimensions:

15.3.3.1 Minimum slope of 1⁄2 in./ft from the channel to the

inside diameter (ID) of riser wall for the benching.

15.3.3.2 Minimum channel invert depth of one-half the pipe

ID.

15.3.3.3 When a channel is cast in a cured base section, the

minimum concrete thickness under the invert shall be 2 in.

15.3.3.4 Width of channel at top of benching shall be a

minimum equal to the pipe ID.

15.3.3.5 Invert shall provide a positive flow between inlet to outlet pipes.

15.3.3.6 The minimum channel centerline radius shall be

equal to the pipe ID.

15.4 Reinforcement:

15.4.1 Base Section Circumferential Reinforcement—

Circumferential reinforcement shall meet all the requirements of Section 14, except that Section 14.5 is not permitted.

15.4.2 Base Slab Reinforcement:

15.4.2.1 A layer of reinforcement shall be placed above the

midpoint and shall have a minimum area of 0.12 in.2/linear ft in both directions.

15.4.2.2 The minimum protective cover over the reinforce-

ment shall be 1 in.

15.4.3 Longitudinal Members—Longitudinal bars or mem-

bers used to maintain a cage of circumferential reinforcement in shape and position within the form shall meet all the requirements of Section 14.

15.4.4 Joint Reinforcement—The mating surface of the base

section joint is not required to contain circumferential rein-forcement.

NOTE 4—(Advisory) Base sections with multiple openings, large openings, or both may require special consideration of their handling reinforcement.

15.5 Joints—Precast reinforced base sections shall be de-

signed and manufactured with a male or female end, so that the

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15.5.1 Joints are designed to perform in axial compression;

therefore, shear or load testing of the joint is not required.

15.6 Permissible Variations:

15.6.1 Internal Diameter—The internal diameter of base

sections shall not vary more than 1 %.

15.6.2 Thickness—The thickness of base slabs with or

without benching shall be not less than that prescribed in the design by more than 5 %. A thickness greater than that prescribed in the design shall not be cause for rejection.

15.6.3 Height of Two Opposite Sides—Variations in laying

heights of two opposite sides of base sections shall be not more than 5⁄8 in.

15.6.4 Height of Sections—The underrun in height of a base

section shall be not more than 1⁄4 in./ft of height with a maximum of 1⁄2 in. in any one base section.

15.6.5 Position of Reinforcement—For base slabs with

monolithic benched inverts with a 4 in. thickness, the maxi-mum variation in the position of reinforcement from that prescribed in 15.4 shall be 610 % of the thickness or 61⁄4 in., whichever is greater. For base slabs with a 6 in. thickness or greater, the maximum variation shall be 610 % of the thick-ness or 65⁄8 in., whichever is the lesser. In no case, however, shall the cover over the reinforcement be less than 3⁄4 in. The preceding minimum cover limitation does not apply to the mating surfaces of base section joints.

15.6.6 Area of Reinforcement—Steel reinforcement areas

that are 0.005 in.2/linear ft less than called for by design shall be considered as meeting the required steel reinforcement area.

15.7 Rejection:

15.7.1 Base sections shall be subject to rejection for failure to conform to any of the specification requirements. In addition, an individual base section shall be subject to rejection because of any of the following:

15.7.1.1 Fractures or cracks passing through the riser wall, except for a single end crack that does not exceed the depth of the joint.

15.7.1.2 Defects that indicate mixing and molding not in

compliance with 7.1 or surface defects indicating honey-combed or open texture that would adversely affect the function of the base section.

15.7.1.3 The planes of the ends are not perpendicular to the

longitudinal axis of the base section, within the limits of permissible variations prescribed in 15.6.

15.7.1.4 Damaged or cracked ends, where such damage

would prevent making a satisfactory joint.

15.7.1.5 Any continuous crack having a surface width of

0.01 in., or more and extending for a length of 12 in. or more, regardless of position in the base section.

16. Steps and Ladders

16.1 Scope:

16.1.1 This section covers manhole steps and ladders used

for providing access through manholes for use in sewer and water works.

16.1.2 The user of this specification is advised that access

through manholes may be by steps that are cast, mortared, or attached by mechanical means into the walls of base, riser, or conical top sections or by ladder.

16.2 Acceptance—Unless otherwise designated by the

owner at the time of, or before, placing an order, acceptance of steps and ladders installed in manholes will be on the basis of tests and inspection of the completed product.

16.3 Materials:

16.3.1 Except as required by Section 16, manhole steps and

ladders shall conform to the requirements of the Occupational Safety and Health Standards, U.S. Department of Labor.

16.3.2 Manhole steps that are cast, mortared, or attached by

mechanical means into the walls of base, riser or conical top sections shall meet the requirements of 16.4 and 16.5 in addition to the following:

16.3.2.1 When dissimilar types of materials are used in the

steps, appurtenances and fastenings, the materials shall be treated to prevent deleterious effects.

16.3.2.2 That portion of the step projecting into the base

section, riser or conical top opening shall be free of splinters, sharp edges, burrs, or projections which may be a hazard.

16.4 Design:

16.4.1 Steps in base section, riser and conical top sections

shall be aligned in each section so as to form a continuous ladder with rungs equally spaced vertically in the assembled manhole at a maximum design distance of 16 in. apart.

16.4.2 Steps shall be embedded in the base section, riser or

conical top section wall a minimum distance of 3 in.

16.5 Dimensions:

16.5.1 Ferrous metal steps not painted or treated to resist

corrosion shall have a minimum cross sectional dimension of 1 in.

16.5.2 The minimum width of rungs or cleats shall be 10 in.

16.5.3 The rung or cleat shall project a uniform clear

distance of 4 in. (minimum) to 6 in. (maximum) 6 1⁄4 in. from the wall of the base, riser, or conical top section measured from the point of embedment to the embedment side of the rung.

NOTE 5—Embedment point is considered the junction of the centerline of the step leg and the wall of the base, riser or conical top section.

16.5.4 The minimum clear distance between the rung or

cleat and the opposite wall of the base, riser, or conical top shall be 18 in. measured at the center face of the rung or cleat.

16.5.5 The vertical spacing and vertical alignment between

adjacent manhole steps and horizontal distance from the inside wall to the centerline of a manhole step may vary 1 inch from the design dimension.

16.6 Physical Requirements:

16.6.1 Testing:

16.6.1.1 The manufacturer furnishing manhole sections

with steps under this specification shall furnish all facilities and personnel necessary to carry out the tests required in the Manhole Step Test section of Test Methods C497.

16.6.1.2 One installed manhole step of the type to be used

on a project shall be tested unless certified test results are available.

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16.6.1.3 Vertical and horizontal load test procedures for

manhole steps shall be in accordance with Test Methods C497.

16.6.1.4 The horizontal pull out load shall be 400 lb.

16.6.1.5 The vertical load shall be 800 lb.

16.6.2 Acceptance—The step shall be acceptable if the

following requirements are met:

16.6.2.1 The step remains solidly embedded after applica-

tion of the horizontal load test.

16.6.2.2 The step sustains a permanent set of 1⁄2 in. or less after application of the vertical load test.

16.6.2.3 No cracking or fracture of the step nor spalling of

the concrete is evident.

16.6.2.4 If certified test results are not available and the step selected fails to conform to the test requirements, the manu-facturer may select two other steps for retests. If either of these steps fail the retest, the steps shall be rejected.

17. Keywords

17.1 absorption; acceptance criteria; base sections; com-pressive strength; concrete; cone tops; design; flat slab tops;

grade rings; ladders; manhole; manufacture; reinforced; riser sections; sewer; steps; tests; water

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