Test Procedure for Compressive strength of concrete cylinder
1. Placing the Specimen— The plain (lower) bearing block is placed, with its hardened face up, on the table of the testing machine directly under the spherically seated (upper) bearing block. The bearing faces of the upper and lower bearing blocks are cleaned and the test specimen is placed on the lower bearing block.
2. Zero Verification and Block Seating— Prior to testing the specimen, it is verified that the load indicator is set to zero. If the indicator is not properly set to zero, it is adjusted.
3. Rate of Loading— The load is applied continuously and without shock.
4. Standards specify that for testing machines of the screw type, the moving head shall travel at a rate of approximately 0.05in. (1mm)/min when the machine is running idle. While for hydraulically operated machines, the load shall be applied at a rate of movement (platen to crosshead measurement) corresponding to a loading rate on the specimen within the range of 20 to 50 psi/sec (0.15 to 0.35 MPa/sec).
5. During the application of the first half of the anticipated loading phase, a higher rate of loading is allowed.
6. No adjustment is made in the rate of movement of the platen at any time while a specimen is yielding rapidly immediately before failure.
7. Load is applied until the specimen fails, and the maximum load carried by the specimen during the test is recorded. The type of failure and the appearance of the concrete are also noted.
Calculation
Compressive strength of the specimen is calculated by dividing the maximum load carried by the specimen during the test with the average cross-sectional area. Determine and express the result to the nearest 10 psi (0.1 MPa).
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