ASTM C307
Briquette Tensile Testing Fixture
Standard Test Method for Tensile Strength of Chemical-Resistant Mortar, Grouts, and Monolithic Surfacings - PDF
ASTM C307 is the standard test method for the tensile strength of chemical-resistant mortars, grouts and monolithic surfacings, including resin, silicate and sulfur materials with aggregate smaller than 6.3 mm (¼ in). It is used to qualify linings, brick and tile grouts and machinery grouts for chemical plants, wastewater treatment, food processing floors and other corrosive environments.
The Briquet Specimen
Shape: a figure-eight briquet, 76 mm (3 in) long and 25 mm (1 in) thick.
About 44 mm (1¾ in) wide at the ends, narrowing to a 25 mm (1 in) waist, so the breaking section is 25 × 25 mm (1 in²).
Cast in briquet gang molds coated with release agent, struck off flush, and cured before testing, normally for 7 days (sulfur mortars may be tested at 24 hours).
Make at least six briquets for each test age.
Fixtures and Equipment
Briquet clips: matched upper and lower clips that hold the briquet by its four shoulders on rollers, with stop plates to center it. Wedge or pneumatic grips should not be used, because clamping a brittle mortar briquet cracks it before the test starts.
Universal testing machine: most chemical-resistant mortars break between about 3 and 15 kN, so a 10 to 50 kN frame with a matched load cell is a good fit.
Clevis or pin adapters so the clips hang freely and self-align.
Test Procedure
Cure the briquets for the required age and measure the waist width and thickness.
Seat the briquet in the clips so the rollers bear evenly on all four shoulders.
Pull at a crosshead speed of 5 to 6.4 mm/min (0.20 to 0.25 in/min) until it breaks.
Record the peak force and check that the break is through the waist.
Average the results of the valid specimens.
Tensile Strength Calculation
Tensile strength = peak force ÷ waist cross-sectional area
Example: a briquet with a 25.4 × 25.4 mm (1 in²) waist breaks at 8,000 N (1,800 lbf). Tensile strength = 8,000 ÷ 645 = 12.4 MPa (1,800 psi).
ASTM C307 FAQ
What size is the ASTM C307 briquet?
A figure-eight briquet 76 mm (3 in) long and 25 mm (1 in) thick, about 44 mm (1¾ in) wide at the ends and 25 mm (1 in) wide at the waist, giving a 645 mm² (1 in²) cross section.
What test speed does ASTM C307 use?
A crosshead speed of 5 to 6.4 mm/min (0.20 to 0.25 in/min).
How long are C307 specimens cured before testing?
Usually 7 days, unless the material specification calls for a different age. Sulfur mortars may be tested 24 hours after casting.
Why are clips used instead of wedge grips?
Mortar briquets are brittle and crack under clamping pressure. Briquet clips hold the specimen by its four shoulders on rollers, so it is pulled in tension without being squeezed.