Determination of Compressive Strength of Cylindrical Concrete Specimens (ASTM Designation: C 39) Hussam Khalid Al Mubarak Abdullah Nasser Al Motairi Omar Al Shalhoub Abdullah Al Zeer Supervisor: Dr Amjed Khabaz Civil and Environmental Engineering Department College of Engineering, Engineering Day 23 April 2013

Objectives The purpose is to determine the compressive strength of cylindrical specimens, either molded or drilled cores. The method is limited to concrete having a density of at least 800 kg/m3 (50 lb/ft3). The 28-day compressive strength ( ) of molded cylinders is normally used in design.

Significance to KSA Compressive strength of concrete is a primary physical property and frequently used in design calculations for the Kingdom concrete projects as bridges, buildings, and other structures. Most general-use concrete has a compressive strength between 20 and 40 MPa (3000 and 6000 psi). Compressive strengths of 70 to 140 MPa (10,000 to 20,000 psi) have been used in special bridge and high-rise building applications.

Description

Equipment and Materials Reusable steel or wax-coated cardboard disposable cylindrical molds, 15 cm in diameter by 30 cm in height or 10 cm in diameter by 20 cm in height. Moist storage facility for curing the fresh concrete. Straight steel tamping rod that is 16 mm in diameter and about 60 cm in length with one end rounded in a hemispherical tip Rubber mallet weighing about 0.6 kg (1.3 lb) A set of special steel caps of appropriate diameter with a neoprene pad contact with the concrete for capping the specimen. Testing machine capable of applying load continuously at the rate of 0.14 to 0.34 MPa/s

Test Procedure Preparation of cylindrical specimens a. Prepare and cure the specimens in accordance with ASTM Designation: C 192. b. Perform air content, slump, and penetration tests on the fresh concrete prior to casting the specimens in accordance with ASTM Designations: C 143, C 231, and C 360. c. Fill the cylinders with three lifts of freshly mixed concrete, tamping each lift 25 times with the tamping rod. Also tap each lift lightly with a mallet 10 to 15times. d. Strike off the excess concrete with the tamping rod and finish to a smooth surface with a steel trowel. e. It is recommended that specimens be prepared and tested in groups of three.

Test Procedure (Cont.) 2) Curing of the concrete specimens a. Allow the specimens to set for about 24 hours at normal room temperature, with the to surface covered to prevent loss of moisture. b. Strip the mold from the specimens and place in the curing facility until ready for testing

Test Procedure (Cont.) 3) Compression Testing Procedure a. Remove the specimen from the curing facility just prior to testing. Specimens shall be tested while still in a moist condition. b. Measure the diameter of the specimen, determined at right angles to each other about mid-height of the specimen. Average the two values to the nearest 0.25 mm (0.01 in.). c. Center the capped specimens in the testing machine and load at the prescribed rate of 0.14 to 0.34 MPa/s (20 to 50 psi/s). d. Load to failure. e. Record the ultimate load, the angle of fracture, and any other pertinent aspects of failure such as voids.

Results

Results

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