§ 6-122. Concrete mix design.

(a)

Materials.

(1)

Portland cement shall conform to A.S.T.M. Standard Specifications for Portland cement, C150-62, Type I.

(2)

High-early-strength Portland cement shall conform to A.S.T.M. Standard Specifications for Portland Cement, C150-62, Type III.

(3)

Aggregates for concrete shall conform to A.S.T.M. Tentative Specifications for Concrete Aggregates, C33-61T or lightweight aggregate C330-60T.

(4)

Air-entrainment may be accomplished by the use of Type 1A cement, or an A.S.T.M.-approved agent added to the mixer. Air-entrainment shall be 5½% 1½% as determined by the A.S.T.M. Designation C138-44. All exterior exposed concrete work shall be air-entrained.

(b)

Tests.

(1)

Air-entrainment 5½% 1½%.

(2)

Slump for handplaced concrete shall not exceed five (5) inches. When high-frequency vibrator is used the slump shall not exceed four (4) inches.

(3)

Test cylinders submitted for compressive strength test shall be sets of three (3) cylinders: One (1) to be broken at seven (7) days and two (2) to be broken at twenty-eight (28) days. Twenty-eight-day breaks shall not be less than three thousand (3,000) p.s.i.

(4)

Aggregate gradation shall be as follows:

a.

Gradation for fine aggregate:

Passing 3/8 " sieve       100%
Passing No. 4 sieve       95—100%
Passing No. 20 sieve       40— 75%
Passing No. 50 sieve       5— 30%
Passing No. 100 sieve       0— 10%

b.

Gradation for course aggregate:

1.

Passing 1" sieve       100%
Passing ¾" sieve       90—100%
Passing 3/8 " sieve       15— 45%
Passing No. 4" sieve       0—  5%

2.

Percent of shale must not exceed 1% by weight.

3.

Percent of chert must not exceed 4% by weight.

(5)

State-approved mix shall be acceptable so long as copies are submitted to the city inspection department at city hall. It shall be the contractor's responsibility to submit approved design mixes to the inspection department prior to placing concrete.

(6)

Approved admixture may be used, however, no less than a five-and-one-half-bag mix may be accepted.

(7)

Additional test cylinders may be required to be cured under same conditions (protection, etc.) as freshly placed concrete. These test cylinders shall be broken as an indication as to whether proper protection was accomplished during low ambient temperature periods.

(8)

In the event that any portion of a project is rejected, the contractor may at his own expense hire a certified testing laboratory to conduct additional tests. If the tests result in the certification (signed and sealed) by the testing laboratory that the structure is sound, then the city shall be liable to the contractor for the expense of the laboratory tests.

(Code 1974, § 5-11)