Concrete Construction – Engineering Feed

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ASTM C-94 Standard Specification for Ready-Mixed Concrete

Material Requirements

Cement: C 150 or C 595

Aggregates: C 33 or C 330 (light weight concrete)

Water: clear and apparently clean

Admixtures: C 260, C 494, C 618, C 989, C 1017.

Specifications Needed

Size of course aggregate.

Slump at delivery.

Percent of air-entrained.

One of the following:

A. Compressive strength at 28 days (lab cure sample)

B. Cement content (bags or lb/yard3), Maximum allowable water content, admixtures.

C. Compressive strength at 28 days, Minimum cement content (bags or lb/yard3), admixtures.

Unit weight (for light weight concrete).

Mixing and Delivery

Adding water: no water should be added.

Sampling: volume: 2 ft3, after discharge 15% of concrete before 85% of discharge. Sample should be taken within 15 minute of elapse time.

Discharge time: discharge should be completed within 90 minutes.

Minimum Tests for Strength, Slump, and Air Entraining

1. One test for 150 cubic yards.

2. One test from each separate batch.

3. One for each class of concrete.

ASTM Specified Method of Testing and Sampling

1. Compression test specimens – C 31

2. Compression test – C 39

3. Yield, unit weight – C 138

4. Air entraining – C 138, C 173, or C 231.

5. Slump – C 143.

6. Sampling fresh concrete – C 172.

7. Temperature – C 1064.

 

Recommended Total Air-Content for Air-Entrained Concrete

Maximum aggregate size

Exposure

condition

3/8″

(9.5mm)

½”

(12.5mm)

3/4″

(19mm)

1″

(25mm)

1-1/2″

(37.5mm)

2″

(50mm)

3″

(75mm)

Mild

4.5

4

3.5

3

2.5

2

1.5

Moderate

6

5.5

5

4.5

4.5

4

3.5

Server

7.5

7

6

6

5.5

5

4.5

Tolerance in Slump

1. When specification specifies “maximum” or “not to exceed”

Specified slump

3″ or less

more than 3″

Plus tolerance

0

0

Minimum tolerance

1-1/2″ (38 mm)

2-1/2″ (63 mm)

2. When specification did not specifies “maximum” or “not to exceed”

Specified slump

Tolerance

2″ (51 mm) or less

±½” (13 mm)

More than 2″ through 4″

±1″ (25 mm)

More than 4″

±1-1/2″ (38 mm)

 





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