Questions and Answers
This test method measures the compressive strength of cylindrical concrete that has a density of less than 50 lb/ft^3.
False
Test method C39/C39M consists of applying a compressive axial load to molded cylinders or cores at any rate until failure occurs.
False
Results obtained from the compressive strength test method will depend on many things, such as the size and _____ of the specimen, batching, _____ procedures, the age, temperature, and _____ conditions during curing.
Shape, mixing, moisture
This test method is used to determine ___ ___ of cylindrical specimens.
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The calibration of the testing machines must be verified under four conditions: within ___ months of the last calibration, upon original installation or after _____, after making _____ or adjustments, and whenever there is reason to suspect the _____ of the indicated loads.
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The machine must be power operated and apply the load intermittently.
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Supplemental means of loading for calibration may be power or hand operated.
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The percentage of error for loads used in the testing machine should not exceed _____ of the indicated load.
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The testing machine should have two steel bearing blocks: a spherically seated block and a solid block.
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The _____ and _____ of the spherically seated bearing blocks must be designed so the steel in the contact area doesn't permanently deform when loaded to the capacity of the testing machine.
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The curved surface of the socket should be _____ and lubricated with _____ at least every _____.
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The ___ ___ block should provide a readily machinable surface for maintenance of the specified surface conditions.
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Specimens should not be tested if any individual diameter of the cylinder differs from another diameter of the same cylinder by less than 2%.
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If cylinders have been made from a single lot of molds which consistently produce nearly the same size specimens, the number of individual cylinders measured is not prohibited from being _____ to one for each ten specimens or _____ per day, whichever is greater.
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When conducting compression test of moist-cured specimens, wait at least three days after their removal from moist storage before testing.
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Test specimens should be ___ ___ during the period between storage and testing.
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When placing the lower bearing block in the table or platen, place the ___ ___ up.
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Align the _____ of the specimen with the _____ of thrust of the spherically seated block.
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Prior to testing the specimen, verify that the load indicator is _____.
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Apply the load _____ and without _____.
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A higher rate of load shall be permitted during the application of the first half of the anticipated loading phase.
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When the specimen fails, record the ___ ___ carried by the specimen during the test, and note the _________.
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Calculate the compressive strength by dividing the ___ ___ by the average ______ area determined.
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Which of these should the test report include?
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The results of this test method may be used to determine quality control of concrete proportioning, mixing, and _____ operations; compliance with _____, or for evaluating the effectiveness of _____.
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The load of a compression machine can be registered on a _____ or in _____.
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Study Notes
Compressive Strength Testing Overview
- ASTM C39/C39M measures compressive strength of cylindrical concrete specimens with density MORE than 50 lb/ft³.
- Test involves applying a PRESCRIBED axial load to cylinders until failure.
Influencing Factors
- Compressive strength test results depend on specimen size, shape, batching, mixing procedures, age, temperature, and moisture conditions during curing.
Calibration and Machine Requirements
- Calibration of testing machines is necessary within 13 months of last calibration, after relocation, repairs, and whenever accuracy is questioned.
- The loading machine must apply continuous load; intermittent application is not allowed.
- Testing machines should have both a spherically seated block and a solid block.
Bearing Blocks and Maintenance
- Spherically seated bearing blocks must be designed to prevent permanent deformation under load.
- The curved surface of the socket should be kept clean and lubricated with petroleum at least every six months.
- The bottom bearing block should offer a machinable surface for maintenance.
Specimen Testing Criteria
- Specimens must not be tested if the diameter difference exceeds more than 2%.
Testing Procedures
- If cylinders produced from similar molds yield consistent sizes, the number of measurements can be reduced to one per ten specimens or three per day.
- Testing for moist-cured specimens should occur as soon as practicable after removing from moist storage.
- Specimens should be kept moist between storage and testing.
Alignment and Load Application
- Lower bearing block should be placed hardened face up, aligning the specimen's axis with the center of the spherically seated block.
- Before testing, ensure the load indicator is set to zero.
- Apply the load continuously and without shock, though a higher rate is allowed during the first half of the loading phase.
Recording and Calculating Results
- Upon specimen failure, record the maximum load and observe the fracture pattern.
- Compressive strength calculation involves dividing the maximum load by the average cross-sectional area.
Test Report Components
- Test reports must include ID number, maximum load, specimen age, cross-sectional area, and any noted defects, among other details.
Quality Control and Usage of Results
- Test results assist in quality control of concrete proportioning, mixing, compliance with specifications, and evaluating admixtures.
- Compression machine loads may be registered in dial or digital form.
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Description
This quiz covers the ASTM C39/C39M standard for measuring the compressive strength of cylindrical concrete specimens. It explores the factors affecting test results, calibration requirements for testing machines, and the importance of proper maintenance of bearing blocks. Test your knowledge on this vital aspect of concrete testing.
