Rilem tc 162-tdf: test and design methods for steel fibre reinforced concrete

Materials and Structures/Mat6riaux et Constructions, Vol. 34, January-February2001, pp 3-6

Uni-axial tension test for steel fibre reinforced concrete Recommendations
The text presented hereunder is a draftfor general consideration. Comments should be sent to the TC Chairlady: Prof. Dr. Jr. Lucie Vandewalle, K.U. Leuven, Departement Burgertijke Bouwkunde, de Croylaan 2, 300I Hevertee, Belgium.Fax: +32 I6 321976; e-mail: lucie,vandewalle@bwk.kuleuven.ac,be, by 30 June 2001.

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RILEM TC 162-TDF: TEST AND DESIGN METHODS FOR STEEl_FIBRE REINFORCED CONCRETE

1. SCOPE
The test described in the following is used to determine the so-called stress-crack opening relationship, %(w), for Steel Fibre Reinforced Concrete (SFRC). The test method is applicable for steel fibre reinforcedcements and steel fibre reinforced concretes that exhibit strain softening behaviour. The method can also be used for other fibre reinforced concretes which exhibit strain softening behaviour as well as plain concrete (which is assumed always to exhibit strain softening behaviour). The test is not intended for determination of the tensile strength. It is recommended that the tensile strength isdetermined independently, e.g. indirectly from the compressive strength using empirical relations derived from plain concrete.

and corresponding displacement shall be recorded digitally. The following data interpretation shall be based on at least 6 specimens per test series.

3. SPECIMEN SIZE AND SHAPE
The standard test specimen is cylindrical with a circular cross-section with nominal diameter150 ram. The specimen is notched with a circumferential notch with a depth of 15 m m +/- 1 m m and a width of 2-5 nun. The notch shall be cut with a diamond saw. Mould induced notches are acceptable in situations where cutting is made difficult, e.g when testing at early ages. The nominal length of the specimen shall be equal to 150 mm, see Fig. 1. Only fibre concretes with a maximum aggregate sizeof 32 m m and a maximum fibre length of 60 m m can be used.

2. BASICS
The test shall be conducted as a displacement controlled tensile test on a notched specimen. The specimen can be either cast or cored from an existing structure or structural element. The test shall be conducted in a closed loop mechanical testing machine using the average measurement of the displacement over the notch asthe feed back signal or in another test setup which ensures stable post cracking response. Both ends of the testing specimen shall be clamped to the testing machine and fixed with respect to rotation in such a way that rotation is sufficiently eliminated. At the same time care shall be taken not to introduce pre-stressing of the specimen. This can, for example, be achieved by providing specialfixtures which allow the test specimen to be glued directly into the test machine or by other means providing similar performance. During testing the load
1359-5997/01 9 RILEM 3

Fig. 1 - The geometry of the standard test specimen for uni-axial tensile testing. Planes A, B and C are parallel. Plane B is a symmetry plane. The total nominal length of the prepared specimen is 150 mm and the nominaldiameter of the specimen is 150 ram. A central, circumferential notch with a depth of 15 mm +/- I mm is cut with a diamond saw. The resulting, maximum width of the notch is 2-5 ram.

Materials and Structures/Mat6riaux et Constructions, Vol. 34, January-February2001

5. TEST SETUP 5.1 Basics
An example of a viable test setup is shown in Fig. 2. The specimen is glued to metal plates that areconnected to the testing machine using rigid, bolted connections. The bolts can be pre-stressed to make the connection as stiff as possible.

5.2 Instrumentation
The displacement across the notch shall be measured using no less than 3 displacement transducers arranged at equal distances along the perimeter of the test specimen. The effective gauge length 1. shall not be larger than 40 mm. The...