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Section 50 – Construction Materials

Class "B-1" Concrete—Shall contain five (5) sacks (470 pounds) of portland cement per

cubic yard and shall have a maximum size of coarse aggregate of either one inch (1”) or

one and one-half inches (1-1/2”).

Class"B-2" Concrete—Shall contain five (5) sacks (470 pounds) of portland cement per

cubic yard and shall have a maximum size of coarse aggregate of three-quarters inch

Class "C" Concrete—Shall contain four (4) sacks (376 pounds) of portland cement per

cubic yard and shall have a maximum size of coarse aggregate of either one inch (1”) or

one and one-half inches (1-1/2”).

Should the quantity of ingredients designed to produce a cubic yard of finished concrete

result in a yield greater than one (1) cubic yard, the relative proportions of fine and coarse

aggregates shall be adjusted as necessary to maintain a consistent quantity of portland cement

in each cubic yard of concrete.

A mix design for each class of portland cement concrete used in the Work shall be

submitted to the Agency for approval at least seven (7) days prior to the proposed portland

cement concrete being incorporated into the Work.

50-5.02 Proportioning

The Contractor shall determine the mix proportions for all portland cement concrete to be

used in the Work. The coarse and fine aggregates shall be combined in such proportions that

the percentage composition by weight of the individual and primary aggregate sizes, as

determined by laboratory screens and sieves, conforms to Section 90-3, “Aggregate Gradings”,

of the State Specifications.

Exact proportions of primary aggregate sizes used in the concrete mix shall be as

designated or approved by the Agency. The Agency may adjust the mix to accommodate

changes in aggregate and moisture contents, to improve mixing and placing characteristics and

to secure maximum quality of the finished concrete.

Concrete shall be from an approved plant. All concrete mixing shall be done in machine

batch mixers of an approved type, having a capacity of not less than that which utilizes a full

sack of cement, unless, in the opinion of the Agency, the quantity to be mixed is too small to

justify the use of a batch mixer. Sacks of cement shall be completely emptied by dumping

directly upon other materials previously measured into the mixer. No splitting of sacks of

cement will be allowed. The cement may be weighed into the batch from bulk storage if the

Contractor provides suitable equipment approved by the Agency.

Mixing shall continue for a minimum of one (1) minute. In mixers larger than one (1) cubic

yard capacity the mixing time shall be increased so minimum mixing time is not less than one

(1) minute for each cubic yard, or part thereof, of the mixer capacity. Where transit mixers are

used, the mixing period shall conform to the requirements of ASTM Designation: C 94.

The total volume of material mixed per batch shall not exceed the rated capacity of the

mixer as determined by the standard requirements of the Associated General Contractors of

America. Mixing equipment not indicated in this Section shall be operated at the speeds

recommended by the manufacturer. Revolving drum mixers, except on transit mixers, shall not

make less than fourteen (14) nor more than eighteen (18) revolutions per minute. The rotation

rate of transit mixers shall produce a peripheral speed of approximately two hundred (200) feet

Each paving mixer or stationary mixer shall be equipped with an acceptable timing device.

Should the Contractor elect to utilize transit-mixing equipment, the Contractor shall make

adequate advance arrangements for preventing delays in delivery and placing of the concrete.

If there is an interval of more than forty-five (45) minutes between any two (2) consecutive

batches or loads, or a delivery and placing rate of less than eight (8) cubic yards of concrete per