Concrete is used extensively in structural applications for its great compressive strength. As a brittle material, tensile loads, such as bending stresses, can pose problems for structural integrity. One method to improve the tensile strength and resilience of concrete materials is through the use of fiber reinforcement. Cracking is inevitable in concrete structures subject to large bending loads, such as those experienced by bridges, building floors, and poured concrete dams. Therefore, it is necessary to test, the flexural strength of reinforced concrete to first crack, the residual bending strength after first crack up to rupture, and crack growth. The information from these tests allow structural engineers to determine the appropriate design of load bearing concrete structures and safety inspectors to evaluate the condition of aging structures.
An important part of flexural testing of concrete is the measurement of net deflection. This is most easily accomplished using either a 2 or 3 transducer arrangement. The 2 transducer arrangement uses a jig attached to the concrete specimen directly above the support members and at the specimen ASTM has specified a standard test method, ASTM C78, for testing flexural strength of concrete beams using a four point bend test by the third-point method. This method is used as the basis for the standard test methods for flexural strength of fiber reinforced concrete. The ASTM standards used for testing fiber reinforced concrete beams in bending are ASTM C1399 for average residual strength and ASTM C1609 for flexural performance including peak strength and toughness. ASTM C1018 is a discontinued standard, also following the methods of ASTM C78, which is sometimes still used to determine flexural toughness and first crack strength. European standards have also been developed for testing flexural strength of concrete beams; these are EN 12390 for hardened concrete and EN 14651 for metallic fibre concrete. Test machines for flexural bend tests of concrete beams must have a high force capacity. Small displacements correspond to large force increases for concrete, so machine actuators and controls must be able to apply this increasing force without significant oscillation, around the desired force, caused by crosshead vibration. The machine and fixture families below can be configured to meet the needs of concrete testing and the requirements of ASTM and EN test standards.
Applicable Testing Standards
- ISO 14651 Flexural Tensile Strength of Metallic Fiber Concrete Test Machine
- BS EN 12390-4 Flexural Compressive Strength - Concrete Test Machine
- ASTM C78 Flexural Bend Concrete Test Equipment
- ASTM C1018 Fiber Reinforced Concrete Flexural Toughness Equipment
- ASTM C1399 Residual Strength Fiber-Reinforced Concrete Test Equipment
- ASTM C1609 Fiber-Reinforced Concrete Flexural Test Equipment
Recommended Test Machine
Force range of 5 kN to 600 kN (1,125 lbf to 135,000 lbf)
Adjustable test space
The most popular choice for static tension and compression tests
These dual column testers are available in both tabletop and floor standing models
Recommended Testing Accessories
Designed in accordance to ASTM C1399
Standard load ratings up to 300 kN (67,500 lbf); higher ratings available upon request
Platen diameters from 56 mm to 346 mm (2.2 in to 13.6 in)
Available in steel, stainless steel, aluminum, or delrin construction
Machined surface for flat interface with test specimen
Available from a 1 mm (0.04 in) measurement range to a 25 mm (1.0 in) measurement range
May be used in a wide variety of tests
Includes a magnetic and adjustable mounting base
Standard units meet Class B-1 of ASTM E83, Class 0,5 of ISO 9513
