Document - 2.pdf

6. Manufacture

6.1

Mixture—

The aggregates, cement, and water shall be

proportioned and mixed to produce a homogeneous concrete

meeting the requirements of this specification, and in accor-

dance with Specification

C94/C94M

C685/C685M

6.2

Forms—

The forms used in manufacture shall be suffi-

ciently rigid and accurate to maintain the dimensions of the

structure within the tolerances given in Section

. All casting

surfaces shall be of smooth nonporous material. Form releasing

agents used shall not be injurious to the concrete.

6.3

Reinforcement—

Reinforcement must be securely tied or

welded (as allowed by the design) in place to maintain position

during concrete placing operations. Where specified all chairs,

bolsters, braces, and spacers in contact with forms shall have a

corrosion-resistant surface.

6.3.1 Flexural reinforcing steel shall not exceed spacing of

12 in. (30.5 cm) center to center.

6.4

Concrete Placement—

Concrete shall be placed in the

forms at a rate such that the concrete is plastic at all times and

consolidates in all parts of the form and around all reinforce-

ment steel and embedded fixtures without segregation of

materials.

6.5

Curing—

The precast concrete sections shall be cured by

any method or combination of methods that will develop the

specified compressive strength at 28 days or less.

6.6

Concrete Quality—

The quality of the concrete shall be

in accordance with the chapter on concrete quality of ACI 318,

current edition, except for frequency of tests, which shall be

specified by the purchaser. Concrete tests shall be conducted in

accordance with Test Method

C39/C39M

6.6.1

Water-Cementitious Ratio—

Concrete that will be ex-

posed to freezing and thawing shall contain entrained air and

shall have water-cementitious ratios of 0.45 or less. Concrete

that will not be exposed to freezing but that is required to be

watertight shall have a water-cementitious ratio of 0.48 or less

if the concrete is exposed to fresh water. For corrosion

protection, reinforced concrete exposed to deicer salts, brack-

ish water, or seawater shall have water-cementitious ratio of

0.40 or less.

7. Tolerances

7.1

Dimensional Tolerances—

The length, width, height, or

diameter measurements of the structure when measured on the

inside surface shall not deviate from the design dimensions

more than the following:

Dimension

Tolerance

0 to 5 ft (0 to 1.5 m)

⁄

in. (±6 mm)

5 to 10 ft (1.5 to 3.0 m)

⁄

in. (±10 mm)

10 to 20 ft (3.0 to 6.1 m)

⁄

in. (±13 mm)

20 ft (6.1 m) and over

as agreed upon between

manufacturer and purchaser

7.2

Squareness Tolerance—

The inside of the rectangular

precast concrete component shall be square as determined by

diagonal measurements. The difference between such measure-

ments shall not exceed:

Measured Length

Allowable Difference

0 to 10 ft (0 to 3.0 m)

⁄

in. (13 mm)

10 to 20 ft (3.0 to 6.1 m)

⁄

in. (19 mm)

20 ft (6.1 m) and over

as agreed upon between

manufacturer and purchaser

7.3

Joint Surfaces—

The following joint tolerances for water

retaining structures shall apply:

7.3.1

Flexible Joint—

The inside joint seam gap between

two sections placed together before a joint sealant is applied

shall not exceed

⁄

in. (10 mm).

7.3.2

Grout Joint—

The opening to be grouted in a group

joint shall not exceed 1 in. (25 mm).

7.4

Reinforcement Location—

With reference to thickness of

wall or slab, reinforcement shall be within

⁄

in. (6 mm) of

the design location, but in no case shall the cover be less than

1 in. (25 mm) for water-retaining structures and

⁄

in. (19 mm)

for nonwater-retaining structures. The varations in reinforce-

ment spacing shall not be more than one tenth of the designed

bar spacing nor exceed 1

⁄

in. (38 mm). The total number of

bars shall not be less than that computed using the design

spacing.

7.5

Slab and Wall Thickness—

The slab and wall thickness

shall be uniform and shall not be less than that shown in the

design by more than 5 % or

⁄

in. (10 mm), whichever is

greater. A thickness greater than that required in the design

shall not be a cause for rejection.

8. Repairs

8.1 Repairs shall be performed by the manufacturer in a

manner to ensure that the repaired structure will conform to the

requirements of this specification.

9. Rejection

9.1 Precast concrete structures or sections of structures shall

be subject to rejection because of failure to conform to any of

the requirements contained herein.

10. Marking

10.1 The following information shall be clearly marked on

each structure or section of structure, by indentation, water-

proof paint, or other approved means:

10.1.1 Date of manufacture,

10.1.2 Name or trademark of the manufacturer, and

10.1.3 Initials or symbols to indicate the intended use of the

structure.

11. Keywords

11.1 concrete; precast; structures; wastewater; water

C913 − 08

Downloaded/printed by

Jed Friesen (Predl Systems) pursuant to License Agreement. No further reproductions authorized.