ISO 21914:2019

INTERNATIONAL ISO
STANDARD 21914
First edition
2019-07
Test methods for fibre-reinforced
cementitious composites — Bending
moment — Curvature curve by four-
point bending test
Méthodes d'essai des composites à base de ciment renforcés par
des fibres — Moment de flexion — Courbe de courbure par essai de
flexion quatre points
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Symbols . 2
5 Test specimens. 3
5.1 Geometry . 3
5.2 Fabrication of specimen . 3
5.3 Loading of specimen . 4
6 Test equipment. 4
6.1 Testing machine . 4
6.2 Loading apparatus . 4
6.3 Measuring device for average curvature . 5
7 Test procedure . 6
8 Calculations. 7
9 Test report . 7
Annex A (informative) Method of estimating tensile strength and average ultimate tensile strain .9
Bibliography .11
Foreword
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This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre-
stressed concrete, Subcommittee SC 6, Non-traditional reinforcing materials for concrete structures.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 21914:2019(E)
Test methods for fibre-reinforced cementitious
composites — Bending moment — Curvature curve by
four-point bending test
1 Scope
This document specifies the test method for obtaining bending moment-curvature curves of fibre-
reinforced cementitious composites (FRCCs) through four-point bending test of prism specimens.
It is applicable to FRCCs that show separated multiple cracks under pure bending before maximum load.
NOTE Separated multiple cracks means two or more independent cracks visible to the eye occurring in the
constant moment span from the bottom side over half depth of the specimen before maximum load is observed, as
shown in Figure 1. For the purpose of confirmation of cracks, spraying up the specimen surface using an alcohol
solution or acetone makes observations easier. The formation of multiple cracks is associated with deflection
hardening behaviour. For FRCCs that do not show separated multiple cracks, see ISO 19044.
a)  Applicable b)  Not applicable
Key
1 constant moment span
2 crack visible to the eye
3 crack
4 crack (out of constant moment span)
P applied load
Figure 1 — Cracking in FRCCs covered by this document
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
1)
ISO 1920-3:— , Testing of concrete — Part 3: Making and curing test specimens
2)
ISO 1920-4:— , Testing of concrete — Part 4: Strength of hardened concrete
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
fibre-reinforced cementitious composite
FRCC
concrete or mortar containing short discrete fibres distributed throughout matrix
Note 1 to entry: Fibres include man-made fibres (e.g., metallic fibres, inorganic fibres, synthetic fibres) and
natural fibres.
3.2
average strain
ratio of axial deformation to gauge length
3.3
average curvature
gradient of average strains (3.2) in constant moment span
4 Symbols
See Table 1.
Table 1 — Symbols
Symbol Unit Description Subclause
b mm width of cross-section of specimen 5.1
D mm depth of cross-section of specimen 5.1
d mm distance between two LVDTs 6.4
L mm overall length of specimen 5.1
M N·mm bending moment 8
P N applied load 8
S mm specimen span 6.2
average strain calculated by measured displacement of
ε — 8
upper LVDT
average strain calculated by measured displacement of
ε — 8
lower LVDT
1) Under preparation. (Stage at the time of publication: ISO/DIS 1920-3:2018.)
2) Under preparation. (Stage at the time of publication: ISO/DIS 1920-4:2018.)
2 © ISO 2019 – All rights reserved

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