Concrete Mixing and Testing Procedure

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What is the primary objective of mixing the cement samples at the laboratory?

To achieve the greatest possible blending and uniformity in the material (correct)

To produce full compaction of the concrete with segregation

To ensure the loss of water or other materials

To determine the quantities of cement, aggregate, and water for each batch

Why is it necessary to store the test specimens in a place free from vibration?

To maintain the specified temperature and humidity

To prevent segregation of the concrete (correct)

To ensure the test specimens are not exposed to air

To prevent excessive laitance formation

What is the purpose of curing the test specimens in water after 24 hours?

To achieve uniform compaction of the concrete

To enhance the strength of the concrete (correct)

To prevent excessive laitance formation

To reduce the temperature of the concrete

What is the minimum relative humidity required for storing the test specimens?

90 percent Signup and view all the answers

What is the maximum permissible deviation in temperature during the storage of test specimens?

± 2°C Signup and view all the answers

What is the size of the test specimens if the largest nominal size of the aggregate does not exceed 2 cm?

10 × 10 × 10 cm Signup and view all the answers

What is the primary factor that compressive strength of concrete depends on?

Water-cement ratio Signup and view all the answers

At what ages are tests typically made for compressive strength?

7, 14, and 28 days Signup and view all the answers

What is the minimum number of specimens required for testing at each selected age?

3 Signup and view all the answers

What is the size of the cube mould conforming to IS: 10086-1982?

150 mm Signup and view all the answers

What is the condition of the aggregates required for each batch of concrete?

Air-dried Signup and view all the answers

What is the purpose of the compressive testing machine in the testing procedure?

To apply a compressive axial load Signup and view all the answers

What is the purpose of wiping the bearing surfaces of the testing machine clean in Step 7?

To remove any loose sand or other material that may interfere with the test Signup and view all the answers

What is the recommended rate of load application in the compression testing machine?

140 kg/sq cm/min Signup and view all the answers

What is the significance of aligning the axis of the specimen with the center of thrust of the spherically seated platen in Step 9?

To ensure the load is applied evenly and accurately Signup and view all the answers

What is the purpose of noting the appearance of the concrete and any unusual features in the type of failure in Step 11?

To observe the behavior of the concrete under compression Signup and view all the answers

What is the duration of curing for the specimens before they are tested by the compression testing machine?

7 days, 14 days, or 28 days Signup and view all the answers

What is the purpose of not applying a packing material between the faces of the test specimen and the steel platen in Step 10?

To prevent any irregularities in the contact surface from affecting the test results Signup and view all the answers