ASTM C496
Splitting Tensile Jig for Concrete Cylinders
ASTM C496 Splitting Tensile Jig – Universal Grip Data Sheet (PDF)
ASTM C496 is the standard test method for splitting tensile strength of cylindrical concrete specimens. Concrete is weak in tension and awkward to grip, so instead of pulling it the method lays a cylinder on its side and compresses it along its length. The line load induces a nearly uniform tensile stress across the vertical diametral plane, and the cylinder splits in two. Universal Grip builds the splitting tensile jig that makes this repeatable: alignment guides that put the cylinder on the loading diameter, supplementary bearing bars that spread the load along the full length, and replaceable bearing strips between steel and concrete.
What ASTM C496 Measures
The method reports splitting tensile strength, T = 2P/(πLD), where P is the maximum applied force, L the specimen length and D the diameter. Molded cylinders and drilled cores are both covered. The value is higher than the direct tensile strength and is used, among other things, to evaluate the shear resistance of lightweight-aggregate concrete and as a design property in codes that reference it. The testing machine must conform to ASTM C39/C39M, and either a concrete compression machine or a universal testing machine can be used. When the bearing faces of the machine are shorter than the cylinder, a supplementary bearing bar or plate carries the load along the full length, and thin bearing strips between the specimen and the bars cushion surface irregularities and seat the cylinder.
How the ASTM C496 Test Works
Draw diametral lines on both ends of the cylinder in the same axial plane so the specimen can be centered and the fracture plane checked afterward.
Measure the diameter (average of three readings) and the length (average of at least two readings) to the precision the standard requires.
Place one bearing strip along the center of the lower bearing bar and set the cylinder on it with the marked plane vertical.
Place the second bearing strip and the upper bearing bar along the top line, and align the jig so the bar sits under the thrust of the machine's spherically seated block.
Apply load continuously without shock at a constant rate within the range the standard specifies until the cylinder splits.
Record the maximum force, the fracture type and the appearance of the concrete, and calculate T = 2P/(πLD).
Discard the bearing strips; they are single-use.
Specimens and Setup
Standard cylinders such as 4 x 8 in. (100 x 200 mm) and 6 x 12 in. (150 x 300 mm) are typical; cores should have a length-to-diameter ratio no greater than about 2.1 and may need ends ground or capped.
Bearing strips are thin plywood, about 1/8 in. (3.2 mm) thick and 1 in. (25 mm) wide, at least as long as the specimen, and are not reused.
The loading rate is specified as a stress rate; for a 6 x 12 in. cylinder this is on the order of a few hundred pounds per second — set it from the current edition for your specimen size.
Keep the cylinder, the strips and the bearing bars dry and clean; a strip that slips changes the loaded line.
Note the curing condition and age of the specimen, which the standard requires in the report.
Universal Grip ASTM C496 Fixture
Alignment jig centers the cylinder on the loading diameter
Supplementary bearing bars spread load along the full specimen length
Uses replaceable bearing strips as specified by the method
Adjustable guides fit common cylinder sizes
Steel construction with machined and ground bearing surfaces
Sits between platens on concrete compression machines and universal frames; adapters available
High-capacity design sized to your compression machine
Applications
Ready-mix and precast concrete QC
Lightweight aggregate concrete design
Drilled core evaluation of in-place concrete
Research and mix development
Related Standards and Products
Send us your specimen dimensions, required capacity and machine connection through our contact page and we will quote an ASTM C496 splitting tensile jig. Request a quote
ASTM C496 FAQ
How is splitting tensile strength calculated?
T = 2P/(πLD): twice the maximum force divided by π times the cylinder length times its diameter. The factor of two comes from the line load being applied along the full length on two diametrically opposite lines.
What are the bearing strips for?
Thin plywood strips, roughly 1/8 in. thick and 1 in. wide, go between the steel bearing bars and the concrete. They cushion surface roughness, define the loaded line and are discarded after one use.
Can I run C496 on a universal testing machine?
Yes. The standard allows any machine that conforms to ASTM C39/C39M, and the jig sits between the platens of a universal frame as readily as in a concrete compression machine, provided the capacity covers the expected splitting load.
Does the jig work with cores?
Yes. Drilled cores are within the scope; they may need ends ground or capped and should keep a length-to-diameter ratio of about 2.1 or less. The adjustable guides accommodate the core diameter.