PROPORTIONING 1.12.1 GENERAL (2009)

Mix proportions shall be proposed by the Contractor for the various parts of the work subject to the approval of the Engineer. Revised mix proportions may be submitted by the Contractor for approval by the Engineer during the work to reflect concrete test results. Proportions of materials for making concrete shall be selected to provide the strength, workability, durability and other qualities specified on the Plans and required by the Engineer.

1.12.2 MEASUREMENT OF MATERIALS (2009)

a. In the measurement of cement, 94 lb per bag = 1/4 barrel = 1 cubic foot (1.5 kg of cement shall be assumed to be as one liter). Materials shall be measured by weighing, except as otherwise specified or where other methods are specifically authorized by the Engineer. The apparatus provided for weighing the aggregates and cement shall be suitably designed and constructed for this purpose. The aggregates and cement shall be weighed separately. The accuracy of all weighing devices shall be such that successive quantities can be measured to within 1% of the desired amount. Cement in standard packages (bags) need not be weighed, but bulk cement and fractional packages shall be weighed. The mixing water shall be measured by volume or by weight. The water-measuring device shall be accurate to within 1/2%. All measuring devices shall be subject to approval of the Engineer.

b. Where volumetric measurements are authorized by the Engineer, the weight proportions shall be converted to equivalent volumetric proportions. In making this conversion, suitable allowance shall be made for variations in the moisture condition of the aggregates, including the bulking effect in the fine aggregate.

1.12.3 WATER-CEMENTITIOUS MATERIALS RATIO (2009)

a. The proportioning of materials shall be based on the requirements for a plastic and workable mix suited to the conditions of placement containing not more than the specified amount of water, including the free water contained in the aggregates. The maximum specified amount of water shall not exceed the quantities shown in Table 8-1-9 for the type of structure and the condition of exposure to which it will be subjected. Moisture in the aggregates shall be measured by methods satisfactory to the Engineer.

b. Free water content of aggregates included in the quantities specified must be deducted from the amounts given in the Table to determine the amount to be added at the mixer. Allowance may be made for absorption when aggregates are not saturated.

1.12.4 AIR CONTENT OF AIR-ENTRAINED CONCRETE (2009)

a. The volume of entrained air in concrete shall be within the limits shown in Table 8-1-10.

Table 8-1-9. Maximum Permissible Water-Cementitious Materials Ratio (by Weight) for Different Types of Structures and Degrees of Exposure

Exposure Conditions (Note 1) Severe wider range in

temperature or frequent alternations of

freezing and thawing (air-entrained conc. only)

Mild temperature rarely below freezing, or rainy, or arid

Description At the water line or _{within the range of}

fluctuating water level or spray

At the water line or within the range of fluctuating water level or spray In Air In Fresh Water In Sea Water or In Contact With Sulfates (Note 2) In Air In Fresh Water In Sea Water or In Contact With Sulfates (Note 2)

Thin sections, such as railings, curbs, sills, ledges, ornamental or architectural concrete, reinforced piles, and pipe

0.49 0.44 0.40

(Note 3)

0.53 0.49 0.40

(Note 3) Moderate sections, such as retaining walls,

abutments, piers, girders, beams

0.53 0.49 0.44

(Note 3)

(Note 4) 0.53 0.44

(Note 3)

Exterior portions of heavy (mass) sections 0.58 0.49 0.44

(Note 3)

(Note 4) 0.53 0.44

(Note 3)

Concrete deposited by tremie underwater – 0.44 0.44 – 0.44 0.44

Concrete slabs laid on the ground 0.53 – – (Note 4) – –

Concrete protected from weather, interiors of buildings, concrete below ground

(Note 4) – – (Note 4) – –

Concrete which will later be protected by

enclosure of backfill but which may be exposed to freezing and thawing for several years before such protection is offered

0.53 – – (Note 4) – –

Note 1: Air-entrained concrete shall be used under all conditions involving severe exposure and may be used under mild exposure conditions to improve workability of the mixture.

Note 2: Soil or ground water containing sulfate concentrations of more than 0.2%.

Note 3: When sulfate resisting cement is used, maximum water-cementitious material ratio may be increased by 0.05. Note 4: Water-cementitious material ratio should be selected on basis of strength requirements.

1

3

4

b. The air content shall be determined by one of the following methods: (1) The gravimetric method, ASTM C138.

(2) The volumetric method, ASTM C173. (3) The pressure method, ASTM C231.

1.12.5 STRENGTH OF CONCRETE MIXTURES (2011)

a. The provisions of this Section are not applicable when using cementitious materials other than Portland cement. b. When preliminary tests of the materials to be used are not available, the required water-cementitious materials ratio

shall be determined in accordance with Method 1 (Article 1.12.5.1). When strengths in excess of 4000 psi (28 MPa) are required, or where lightweight aggregates or admixtures (other than those exclusively for the purpose of entraining air) are to be used, the required water-cementitious materials ratio shall be determined in accordance with Method 2 (Article 1.12.5.2). Method 3 (Article 1.12.5.3) may be used if statistical data conforming to Article 1.12.5.3 are available.

1.12.5.1 Method 1 – Without Preliminary Tests

a. Concrete proportions may be determined in accordance with this method if approved by the Engineer. Concrete proportions shall then be based on the water-cementitious materials ratio limits found in Table 8-1-11. These limits are only for concrete that is made with cements meeting Types I, IA, II, IIA, III, IIIA, or V of ASTM C150, or Types IS, IS-(A), IS(MS), IS-(A)(MS), IP or IP-(A), of ASTM C595. Volume of entrained air shall be within limits of

Article 1.12.4. Air Content of Air-Entrained Concrete ratio shall not be greater than that required by Article 1.12.4.

b. The values in Table 8-1-11 are based on the use of cement and aggregates meeting the requirements of this Section and the concrete being sufficiently protected from loss of moisture and from low temperatures to ensure that proper curing

Table 8-1-10. Air-Entrained Concrete Volume

Maximum Size Coarse Aggregate Inches (mm) Air Content % by Volume 1-1/2, 2, or 2-1/2 (38, 50, 63) 5 ±1 3/4, 1 (19, 25) 6 ±1 3/8, 1/2 (10, 13) 7-1/2 ±1

Table 8-1-11. Water-Cementitious Materials Ratio for Air Entrained Concrete

Specified 28 Day Compressive Strength