AASHTO T-22-90

Con c rete Lab orato ry T-22

Janua ry 200 2009 9

Compressive Strength of Cylindrical Concrete Specimens AASHTO T-22-07 (Modified) This test method covers the apparatus, concrete test specimen, and the determination of  compressive strength of cylindrical concrete specimens. It is limited to concrete having a unit 3 3 weight in excess of 800 kg/m (50 lb/ft ). Compressive strength is done on concrete cylinders in order to communicate concepts and to verify structural integrity.  M odification: Do not record cylinder break type.

Key Elements:

AASHTO T-23, Making and Curing 1. Obtain test specimen. Obtain specimen according to AASHTO Concrete Test Specimen in the Field. 2. Inspect apparatus. Testing machine shall be of a type having sufficient capacity and capable of applying the load continuously and without shock. Verify that the upper bearing block  moves freely. Calibrate when machine is originally installed or relocation of the machine. Recalibrate whenever there is reason to doubt the accuracy of the results (5.1.1.4). See Section 5 of AASHTO T-22, for all requirements of testing machine. 3. Prepare the test cylinder.   Neither end of test specimen when tested shall depart from  perpendicularity to the axis by more than 0.5 degrees (approximately equivalent to 1.6 mm in 300 mm (1/16 in. in 12 in.), and 1 mm in 200 mm (1/25 in. in 8 in.) long cylinder) (6.2). Measure the diameter of each cylinder. The diameter used for calculating the cross-sectional area of the test specimen shall be determined to the nearest 0.25 mm (0.01 in.) by averaging two diameters measured at right angles to each other at about mid-height of the cylinder  (6.1). Do not test any cylinder for strength if any individual diameter of a cylinder differs from any other diameter of the same cylinder by more than 2.0 percent.  Note: Cross-sectional area = π(r²)

4. Check planeness of cylinder ends. The ends of compression test specimens that are not   plane within 0.050 mm (0.002 in.) shall be sawed or ground, but if the ends are plane to within 0.050 mm (0.002 in.) with no depressions deeper than 0.050 mm (0.002 in.), then neoprene caps with steel controllers may be used instead of capping. (6.2)  Note:

Cylinder ends must not have any depressions greater than 5.0 mm (0.20 in) in order to use unbonded caps.

5. Insert cylinder into testing machine. Place the lower bearing block, on the table or platen of the testing machine directly under the upper bearing block. Wipe clean the bearing faces of the upper and lower bearing blocks and wipe clean the ends of the test specimen. Carefully align the axis of the specimen with the center of the upper bearing block. Rotate the upper   bearing block to ensure it moves freely.

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Con c rete Lab orato ry T-22

Janua ry 2009

6. Rate of loading. Apply the load continuously and without shock. For hydraulically operated machines, the load shall be applied at a rate on the specimen of 35 ± 7 psi/s. The designed rate of movement shall be maintained at least during the latter half of the anticipated strength (7.5.1). During the application of the first half of the anticipated loading phase a higher rate of loading shall be permitted (7.5.2). Make no adjustment in the rate of loading during the latter half of the loading. Continue to load specimen until complete failure is achieved. 7. Record results. Record the maximum load carried by the test specimen. 8. Calculate the compressive strength. Divide the maximum load by the cross-sectional area of the test cylinder calculated in Key Element 2. 9. Report the following test specimen information. Test specimen identification number, diameter, cross-sectional area, maximum load, any defects in specimens or caps, age of  specimen, and calculated compressive strength to the nearest 0.1 MPa (10 psi). (9)

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