DRAFT UGANDA STANDARD  
  DUS 2093  
First E dition  
2018 -mm-dd 
 
 
 Reference number  
DUS 2093 : 2018 
© UNBS 2018   
  
Carbon and Glass Fibre  Reinforced Polymer bar materials for 
concrete reinforcement — Specification  
 DUS 2093 : 2018  
ii © UNBS 2018  – All rights reserved  
 Compliance with this standard does not, of itself confer immunity from legal obligations  
A Uganda Standard does not purport to include all necessary provi sions of a contract. Users are 
responsible for its correct application  
© UNBS 2018   
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, including photocopying and microfilm, without prior written 
permission from UNBS.  
Requests for permission to reproduce this document should be addressed to  
The Executive Director  
Uganda National Bureau of Standards  
P.O. Box 6329  
Kampala  
Uganda  
Tel: +256 41 4 333 2 50/1/2/3  
Fax: +256 41 4 286 123  
E-mail: info@unbs.go.ug  
Web: www.unbs.go.ug  CDUS 2093 :2018  
© UNBS 2018  – All rights reserved  iii 
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ............................  iv 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  2 
4 Classification  ................................ ................................ ................................ ................................ .........  3 
5 Materials and manufacture  ................................ ................................ ................................ ...................  3 
5.1 Fibres  ................................ ................................ ................................ ................................ ......................  3 
5.2 Matrix resins  ................................ ................................ ................................ ................................ ..........  3 
5.3 Fillers and additives  ................................ ................................ ................................ ..............................  3 
5.4 Manufacturing process  ................................ ................................ ................................ .........................  3 
6 Physical properties  ................................ ................................ ................................ ...............................  4 
6.1 Fiber content  ................................ ................................ ................................ ................................ ..........  4 
6.2 Glass transition temperature  ................................ ................................ ................................ ...............  4 
6.3 Bar sizes  ................................ ................................ ................................ ................................ .................  4 
7 Mechanical properties ................................ ................................ ................................ ...........................  5 
7.1 Tensile strength  ................................ ................................ ................................ ................................ ..... 5 
7.2 Tensile modulus of elasticity  ................................ ................................ ................................ ...............  5 
7.3 Shear strength (perpendicular to bar)  ................................ ................................ ................................ . 5 
7.4 Ultimate tensile strain  ................................ ................................ ................................ ...........................  5 
7.5 Bond strength  ................................ ................................ ................................ ................................ ........  5 
8 Durability properties  ................................ ................................ ................................ .............................  5 
8.1 Moisture absorption  ................................ ................................ ................................ ..............................  5 
8.2 Resistance to alkaline environment  ................................ ................................ ................................ .... 6 
8.3 Longitudinal wicking  ................................ ................................ ................................ .............................  6 
9 Other requirements  ................................ ................................ ................................ ...............................  6 
9.1 Bend radius  ................................ ................................ ................................ ................................ ............  6 
9.2 Strength of bends  ................................ ................................ ................................ ................................ .. 6 
10 Marking  ................................ ................................ ................................ ................................ ...................  7 
11 Sampling  ................................ ................................ ................................ ................................ ................  8 
11.1  Sampling frequency and number of specimens  ................................ ................................ ................  8 
11.2  Methods of sample selection  ................................ ................................ ................................ ...............  8 
Annex A  (normative)  Test method for strength of FRP bent bars and stirrups at bend locations  ..........  9 
A.1 Scope  ................................ ................................ ................................ ................................ ......................  9 
A.2 Significance and use  ................................ ................................ ................................ .............................  9 
A.3 Test equipment and requirements  ................................ ................................ ................................ ....... 9 
A.4 Specimen preparation  ................................ ................................ ................................ ...........................  9 
A.5 Conditioning  ................................ ................................ ................................ ................................ ........  10 
A.6 Test method  ................................ ................................ ................................ ................................ .........  10 
A.7 Calculations  ................................ ................................ ................................ ................................ .........  11 
A.8 Report  ................................ ................................ ................................ ................................ ...................  12 
 DUS 2093 : 2018  
iv © UNBS 2018  – All rights reserved  
 Foreword  
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Trade , Industry and 
Cooperatives established under Cap 327 , of the Laws of Uganda , as amended .  UNBS is mandated to co -
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT  Agreement  of the World Trade Organisation (WTO).  
The work of preparing Ugan da Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a given field or area and consists of key stakeholders 
including government, academia, consumer groups, private sector and other in terested parties.  
Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
The committee responsible for this document is Technical Committee UNBS /TC 04, Mechanical engineering 
and metallurgy.  
 DRAFT UGANDA STANDARD  DUS 2093 : 2018  
 
© UNBS  2018 – All rights reserved  1 
 Carbon and Glass Fibre  Reinforced Polymer bar materials for 
concrete reinforcemen t — Specification  
1 Scope   
1.1 This specification describes permitted constituent materials, limits on constituent volumes, and minimum 
performance requirements for carbon and glass fibre reinforced polymer (FRP) bars to be used as 
reinforcement for non -pre-stressed concrete . 
Note  Due consideration should be taken when using FRP bars covered by this standard for 
reinforcement in suspended structural elements such as a beams and slabs . 
1.2 Only carbon and Glass FRP bars are covered by this specification.  
1.3 FRP bars made of more than one fibre type (hybrid FRP) are not covered by this specification.  
1.4 Pultruded FRP bars with no external surface enhancement (that is, plain or smooth bars) to facilitate 
bond with concrete are not covered by this specificatio n. Similarly, hollow FRP bars are not considered due to 
lack of documented performance as reinforcement for concrete.  
1.5 Plain FRP bars used as dowels (that is, devices that transfer shear across concrete joints) where the 
intended function requires slip of the dowel are not covered by this specification.  
1.6 This specification does not cover pre -manufactured grids and gratings made with FRP materials. FRP 
mats resulting from assembly of deformed FRP bars, however, are covered by this document.  
1.7 This sp ecification does not cover FRP bars when used for external and near -surface -mounted 
strengthening applications.  
1.8 The text of this specification references notes and footnotes that provide explanatory material. These 
notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the 
specification.  
2 Normative references   
The following referenced documents referred to in the text in such a way that some or all of their content 
constitutes requirements of this documen t. For dated references, only the edition cited applies. For undated 
references, the latest edition of the referenced document (including any amendments) applies.  
ISO 62 , Plastics — Determination of water absorption  
ISO 7822, Textile glass reinforced plast ics — Determination of void content — Loss on ignition, mechanical 
disintegration and statistical counting methods  
ASTM D3171 -06 Standard Test Methods for Constituent Content of Composite Materials  
ISO 11667, Fibre -reinforced plastics — Moulding compounds and prepregs — Determination of resin, 
reinforced -fibre and mineral -filler content — Dissolution methods  DUS 2093: 2018  
2 © UNBS 2018  – All rights reserved  
 ASTM D5117 -17, Standard Test Method for Dye Penetration of Solid Fiberglass Reinforced Pultruded Stock  
ISO 10406 -1, Fibre -reinforced polymer (FRP) rein forcement of concrete — Test methods — Part 1: FRP bars 
and grids  
ISO 11357 -2, Plastics — Differential scanning calorimetry (DSC) — Part 2: Determination of glass transition 
temperature and glass transition step height  
ISO 6721 -11, Plastics — Determination  of dynamic mechanical properties — Part 11: Glass transition 
temperature  
US 1834 , Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens . 
US 1840 , Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory  
US 1837 , Standard Test Method for Slump of Hydraulic -Cement 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 foll owing addresses:  
— ISO Online browsing platform: available at http://www.iso.org/obp  
3.1  
commercial -grade material  
a material formulated for and used in industrial (not consumer) applications  
3.2  
production lot  
any lot of FRP bar produced from start to finish with the same constituent materials used in the same 
proportions without changing any production parameter, such as cure temperature or line speed  
3.3  
property, nominal  
a value provided by the manufacturer no greater than the mean of at least the required number of samples 
tested according to a specified method. This definition is applicable to tensile elastic modulus, moisture 
absorption, and resi stance to alkaline environment  
3.4  
Pultruded bar  
linear composite bar produced continuously by the pultrusion process and usually of constant cross -section 
and characteristics  
3.5  
Glass transition  
reversible change in an amorphous polymer or in amorpho us regions of a partially crystalline polymer from (or 
to) a viscous or rubbery condition to (or from) a hard and relatively brittle one  
3.6  
glass transition temperature  
approximate midpoint of the temperature range over which a glass transforms between elastic and 
viscoelastic behaviour characterized by the onset of a rapid change in its coefficient of thermal expansion  DUS 2093: 2018  
© UNBS 2018  – All rights reserved  3 
 4 Classification  
FRP bars shall be classified according to fibre composition with the first letter of the acronym designating fiber 
type as follows:  
a) CFRP: carbon fibre-reinforced polymer bar  
b) GFRP: glass fibre-reinforced polymer bar . 
5 Materials and manufacture  
5.1 Fibres  
Fibres shall be in the form of  unidirectional rovings (glass fibres) or unidirectional tows (carbon fibres) of given 
size and mass . Fibre sizings and coupling agents shall be compatible with the resin system used to 
impregnate them.  
Note  The fibre type and fibre amount determine the ph ysical and mechanical properties of the FRP bar.  
5.2 Matrix resins  
5.2.1  Vinylester and epoxy resin systems are permitted provided the finished product meets the physical 
and durability requirements of this specification. Blending of Vinylester and epoxy r esins is permitted.  
5.2.2  The base polymer in the resin system shall not contain any polyester.  
5.2.3  Styrene is permitted to be added to the polymer resin during processing. Added styrene shall be less 
than 10% by mass of the polymer resin. The amount of styrene, as a mass percentage of the polymer resin, 
added during processing shall be reported.  
5.2.4  Constituent content of resin shall be determined by ASTM D3171.  
5.3 Fillers and additives  
5.3.1  Only commercial -grade inorganic fillers such as kaolin clay , calcium carbonate, and alumina trihydrate 
are permitted, and shall not exceed 20% by mass of the polymer resin constituent.  
5.3.2  Only commercial -grade additives and process aids, such as release agents, low -profile shrink 
additives, initiators, promoter s, hardeners, catalysts, pigments, fire retardants, and ultraviolet inhibitors are 
permitted and depend on the processing method. Shrink additives, if used, shall be less than 10% by mass of 
the polymer resin.  
5.3.3  Only commercial -grade inorganic or organ ic nonwoven surfacing mats or veils are permitted.  
5.4 Manufacturing process  
5.4.1  The manufacturer shall produce FRP bars using variations of the pultrusion process.  
5.4.2  Process or material modifications are not permitted during the production of a sin gle lot.  
5.4.3  The manufacturer shall document the process used and report the date of production and production 
lot size . DUS 2093: 2018  
4 © UNBS 2018  – All rights reserved  
 6 Physical properties  
6.1 Fiber content  
The fiber content shall be measured by ASTM D3171 or D2584. When ASTM D3171 is used, fiber co ntent 
shall not be less than 55% by volume. When ISO 7822  is used, fiber content shall not be less than the fraction 
by mass corresponding to 55% by volume. The manufacturer shall report the fiber content of the end product 
by volume or by mass in accordan ce with the method used.  
6.2 Glass transition temperature  
The glass transition temperature Tg of the resin shall not be less than 1 10 °C (see Note 3). The glass 
transition temperature shall be measured on a coupon cut from the as -produced bar using either the 
Differential Scanning Calorimetry (DSC) method in ISO 11357 -2 or the Dynamic Mechanical Analysis (DMA) 
method in ISO 6721 -11. When using the DSC method, test results for both the first scan (according to ISO 
11357 -2) and the second scan shall be report ed. 
Note  This temperature does not represent the maximum  permitted service temperature, and is intended for 
purchaser’s  quality assurance only.  
6.3 Bar sizes  
6.3.1  Only FRP bars of solid round or elliptical cross -section  shape are allowed.  
6.3.2  The size o f FRP bars shall be as listed in Table 1. 
Table 1—Bar size of FRP round bars  
Nominal diameter  
mm Tolerances , 
% 
6 +5 
7 
8 
10 
12 
16 +4 
20 
22 
25 
32 
 
6.3.3  The calculated diameter of an FRP bar is equivalent  to that of  a smooth round bar having the same 
area as the  FRP bar measu red in accordance with US ISO 10406 -1. 
6.3.4  When the FRP bar is of elliptical shape, the minimum  and maximum outside dimensions of the bar 
cross section  shall be provided in addition to the calc ulated diameter.  The calculated diameter of elliptical FRP 
bars is equivalent  to that of a solid round bar having the same cross -sectional  area as determined according 
to ISO 10406 -1. DUS 2093: 2018  
© UNBS 2018  – All rights reserved  5 
 6.3.5  The nominal diameter of an FRP bar to be used for  designation and design shall be equal to the 
calculated diameter.  When the calculated diameter does not correspond to one of the  nominal values given in 
Table 1, the next immediately smaller  nominal diameter given in such table shall be used.  
7 Mechanical properties  
7.1 Tensile strength  
7.1.1 The tensile strength for product certification shall be measured according to US ISO 10406 -1 based 
on nominal dimensions and at a frequency and number of specimens, as indicated in Section 11. The 
minimum tensile strength shall be 800  N/mm2 for GFRP and 1400 N/mm2 for CFRP . The manufacturer shall 
report the individual test results.  
7.1.2 The tensile stren gth of a production lot shall be  measured according to  ISO 10406 -1 at a frequency 
and number of  specimens as indicated in Section 11 . The strength of each  specimen shall be reported and be 
not less than the strength re ported by the manufacturer. Otherwise , the production lot shall be rejected.  
7.2 Tensile modulus of elasticity  
The nominal tensile modu lus of elasticity of GFRP bars shall be at least 50 N/mm2 regardless of bar size or 
geometry. The tensile modulus of elasticity of CFRP bars shall be at least 1 30 N/mm2 regardless of bar size or 
geometry. The tensile modulus of elasticity is de rived from specimens tested in accordance with US ISO 
10406 -1 at a frequency and number of specimens as indicated in Section 11 . The manufacturer shall report 
the individual test results.  
7.3 Shear strength (perpendicular to bar)  
The transverse shear strength of FRP bars shall  be at least 1 50 N/mm2 as determined by a test method  in US 
ISO 10406 -1 at a frequency and number of specimens as indicated in Section 11 . The manufacturer shall 
report the individual test results.  
7.4 Ultimate tensile strain  
The ultimate tensile strain shall be calculated for the  purpose of product certification (that is, nominal value). 
The nominal ultimate tensile strain shall be calculat ed by  dividing the tensile strength by the nominal  elastic 
modulus. The nominal ultimate tensile  strain of CFRP and GFRP bars obtained by this procedure  shall be at 
least 0.5 % and 1.2%, respectively . 
Note  The calculation method is based on the  assumption t hat the stress -strain behavior is linear elastic  
7.5 Bond strength  
The bond strength of FRP bars shall be at least 10 MPa as determined in accordance with  a test method in 
US ISO 10406 -1, at a frequency and number of specimens as indicated in Section 11 . The manufacturer shall 
report the individual test results and the method used for casting the test specimens.  
8 Durability properties  
8.1 Moisture absorption  
Moisture absorption tests shall be determined (that is, nominal value) in  accordance with ISO 62 , Section 7.4 , 
using a water temperature of 50 °C  at a frequency and number of specimens as indicated in  Section 11. The 
individual moisture absorption test results  shall be reported, and their average shall be less than 1.0% . DUS 2093: 2018  
6 © UNBS 2018  – All rights reserved  
 8.2 Resistance to alkaline environment  
Resistance to alkaline environment tests shall be determined (that is, nominal value) in accordance with a test 
method in US ISO 10406 -1 at a frequency and number of specimens as indicated in Section 11 . The 
manufacturer shall report the individual test results and the test method . Tensile strength reduction shall be 
less than 25  % 
8.3 Longitudinal wicking  
Five consecutive 25 mm long segments cut from an FRP bar shall be tested in accordance with ASTM D5117 
at a frequency as indicated in Section 11. No continuous voids shall be permitted in the resin. A continuous 
void is one that appears in all five conse cutive test specimens. The presence of hollow fibers is not considered 
a void.  
Note  This requirement is intended to check for continuous voids that could occur due to shrinkage of the resin 
during processing or as the result of poor consolidation of the fi ber and resin matrix during production.  
9 Other requirements  
9.1 Bend radius  
Bends shall be formed in FRP bars that are made with  thermosetting resin and only while the resin is in a 
physical  liquid state. The minimum inside bend radii for  factory -formed F RP bar bends are specified in Table 
2. 
Note  After the resin has passed the liquid state, bending or alteration of the FRP bar is not possible due to the 
inability of the fibers to move [or reorient] within the resin matrix. Because thermosetting polymers are highly cross linked, 
heating the bar on site will not be allowed as it leads to a decomposition of the resin, thus creating a loss of strength in the 
FRP bar.  
Table 2 — Minimum inside bend radius of bent bars  
Nominal bar diame ter 
mm Bend radius  
mm 
6 19 
7  
8  
10 28 
12  
16 48 
20  
22 67 
25 76 
32 127 
9.2 Strength of bends  
9.2.1  The strength of bends shall be at least 70%  and 60%  of the tensile strength of corresponding straight 
bars of CFRP and GFRP respe ctively as determined in accordance with a method contained in Annex A . 
Testing frequency and number of specimens  shall be as indicated in clause  11. The manufacturer shall  report 
the individual test results.  DUS 2093: 2018  
© UNBS 2018  – All rights reserved  7 
 9.2.2 For a measure of the manufacturer’s quali ty control  and purchaser’s quality assurance on FRP bends, 
one of the  two test methods listed as follows shall be used at a frequency  and number of specimens as 
indicated in clause  11. The manufacturer shall report the individual test  results.  
9.2.2.1  When it is possible to extract a straight portion  of the tail of the bent bar of sufficient length, such an 
element  shall be tested a ccording to US ISO 10406 -1. The  strength of each specimen shall be not less than 
the strength reported by the manufacturer for the bar of that  diameter.  
9.2.2.2  When the bend size does not allow for the  tensile testing of one of its straight portions, a sp ecimen 
shall be obtained from the bend and tested for inter -laminar  (horizontal) shear strength according to US ISO 
10406 -1 and for fiber content according to ISO 7510 . The  manufacturer shall report the individual test results. 
Minimum inter -laminar shear strength values have not yet been established . The fiber content of each  
specimen shall be not less than the minimum percent by  volume reported in Section 6.1. 
10 Marking  
10.1 Each bundle of bars shall be identified with a corresponding  production lot numb er. Production lot 
numbers  shall be printed on each bar or affixed to each bundle by  means of a durable tag.  
10.2 Each bundle of bars shall be labeled with the  following information:  
a) manufacturer ’s name and address ; 
b) classification of fiber (that is,  G for glass and C for carbon);  
c) nominal bar diameter and length (in metric);  
d) nominal tensile strength;  
e) nominal modulus of elasticity ; and  
f) for bent bars, the shape of the bend, the radius of the bend, and the length of the legs  
10.3 The only marking required for each individual bar  shall be the nominal bar diameter designation, and it 
shall be  made by a durable means.  Bar markings shall take the form of permanent physical  marking of the bar 
size in metric on the product or permanent  color coding applied to  the bar as shown in Table 3 
Note  Marki ngs will be used at the construction site  to verify that the  specified bars are being used.  
Table 3 — Colour codes for marking bar sizes  
Nominal bar diameter  
mm Colour * 
6 Black  
7 Royal blue  
8 Gray  
10 Orange  
12 Green  
16 Red 
20 Blue 
22 Yellow  
25 Purple  DUS 2093: 2018  
8 © UNBS 2018  – All rights reserved  
 32 Brown  
*Color coding should be at least 150 mm of FRP  at each 
end of bars. 
 
11 Sampling  
11.1 Sampling frequency and number of  specimens  
11.1.1 For the determination of each of the mechanical and  durability properties for the manufacturer’s 
quality control  tests and for the purchaser’s quality assurance test s, at least  five samples of sufficient length to 
perform the required tests  shall be obtained from each production lot.  
11.1.2 For the determination of each of the mechanical and  durability properties, at least 25 samples of 
sufficient  length to perform th e required tests shall be obtained in groups  of five from five different production 
lots. 
11.1.3 For orders of bends in varying quantities that together  will comprise a production lot of bends, at the 
discretion of  the purchaser, testing of bends for the m anufacturer’s quality  control and for the purchaser’s 
quality assurance may be  limited to a minimum of five samples of a 90 -degree bend  with the smallest bend 
radius to bar diameter ratio.  
11.2 Methods of sample selection  
Samples from each production lot t o be used for preparing  test specimens shall be selected by the 
manufacturer on a  random basis . DUS 2093: 2018  
© UNBS 2018  – All rights reserved  9 
 Annex  A 
 
(normative)  
 
Test method for strength of FRP bent bars and stirrups at bend locations  
A.1 Scope  
This test method specifies the test requirements for strength capacity of FRP bent bars used a s an anchorage 
for stirrups in concrete structures  
A.2 Significance and use  
A.2.1  This test method is intended for use in laboratory tests to determine the strength capacity of the bent 
portion provided as an anchorage in which the principal variable is th e size, bend radius, or type of FRP 
stirrup.  
A.2.2  Bending of FRP stirrups to develop anchorage leads to a significant reduction in the strength capacity 
of the stirrups. The bend radius and tail length beyond the bend are important factors affecting the b end 
capacity.  
A.2.3  This test method measures the ultimate load capacity of a single FRP stirrup subjected to tensile 
forces in the direction of the straight portion.  
A.2.4  This test method is intended to determine the bend capacity and strength reduction for material 
specifications, research and development, quality assurance, and structural design and analysis. The 
behavior of bent bars and stirrups should be measured according to the method given herein, in keeping with 
the intended purposes.  
A.3 Test eq uipment and requirements  
The hydraulic cylinder and load cell should be calibrated, have a loading capacity in excess of the capacity of 
the specimen, and be capable of applying load at the required loading rate. The load cell should also be 
capable of giv ing readings of loading accurate to within 1% throughout the test.  
A.4 Specimen preparation  
A.4.1  The configuration of a typical specimen is shown in Figure 1. The dimensions of each concrete block 
used to anchor the FRP stirrup may be varied according to the dimensions of the stirrup used. The free length 
of the stirrup between the two blocks, however, should not be less than 200 mm (400 mm is suggested). The 
concrete block should be reinforced using steel stirrups, as shown in Figure 1, to prevent splitti ng of the 
concrete block before rupture of the stirrup at the bend. The dimensions of the stirrups might be variable, 
therefore, the tail length lt of the FRP stirrup tested to evaluate the bend capacity should not exceed 150 mm. 
The debonding tube is used  to eliminate the straight -bar development of the hooked bar. The debonding tube 
should slip fit over the reinforcing bar. Fill the ends of the debonding tube with caulk to prevent the tubes from 
filling with concrete during casting.  DUS 2093: 2018  
10 © UNBS 2018  – All rights reserved  
 
 
Figure 1 — Configuration of specimen.  
A.4.2  The concrete should be a standard mixture, with coarse aggregates having a maximum dimension of 
20 to 25 mm. It should be batched and mixed in accordance with the applicable clauses  of US 1840. The 
concrete should have slump of 100 ± 20 mm in accordance with US 1837, and the compressive strength at 28 
days should be 30 ± 3 MPa in accordance with US 1834. A minimum of five standard 150 x 300 mm or 100 x 
200 mm control cylinders should be made for dete rmining compressive strength from each batch of concrete  
A.4.3  The number of test specimens for each test condition should not be less than five. If a specimen fails 
by splitting of the concrete block, an additional test should be performed on a separate s pecimen taken from 
the same lot as the failed specimen.  
A.4.4  If test specimens fail due to pullout of the bent bar from the concrete, this is an indication that the 
bend radius and tail length are inadequate for the bar being tested. It will be necessary to adjust these 
parameters, and perhaps the size of the test blocks as well, and retest.  
A.5 Conditioning  
A.5.1  Unless a different testing environment is specified as part of the experiment, the tests should be 
conducted at the standard laboratory atmosphe re (23 ± 3 °C and 50 ± 10% relative humidity).  
A.5.2  Preconditioning of FRP bars before casting in concrete is permissible but must be reported.  
A.6 Test method  
A.6.1  The test setup, shown in Figure 2, consists of a hydraulic jack to apply the relative dis placement 
between the two concrete blocks and a load cell to measure the applied load. Steel plates and plaster bags 
should be placed in front of the load cell and the hydraulic jack to distribute the applied load to the surface of 
the concrete. A spherica l washer may also be used at the end of the ram. The two blocks should be placed on 
top of steel rollers to minimize the friction forces between the blocks and testing bed.  DUS 2093: 2018  
© UNBS 2018  – All rights reserved  11 
 
 
Figure 2 — Test setup.  
A.6.2  Tensile strength of straigh t FRP bars with the same diameter as the FRP stirrups should be 
determined in accordance with US ISO 10406 -1 
A.6.3  The test specimens should not be subjected to any shock, vibration, or torsion during the test. 
Increase the force in the jack in a smooth, c ontinuous manner until the specimen fails. Do not pause the 
application of load during the test.  
The loading rate should be selected so that the specimen fails at a time of between 1 and 10 min from the 
start of the test.  
A.6.4  Record the failure load and failure mode for the specimen.  
A.7 Calculations  
A.7.1  The bend capacity of the FRP stirrup should only be assessed on the basis of the specimen 
undergoing failure at the bend. In cases where block splitting has clearly taken place, the data should be 
disre garded, and additional tests should be performed until the number of the test specimens failing at the 
bend is not less than five.  
A.7.2  The bend capacity of the FRP stirrup should be calculated according to Eq. (1), and rounded to three 
significant digits  
AFfub
ub2
 
where  
fub bend capacity of the FRP stirrup, MPa  
Fub ultimate load capacity according to bend tests, N; and  
A cross -sectional area of single leg of the FRP stirrup, mm2. 
A.7.3  The strength -reduction factor is calculated according to Eq. (2)  
uub
ffX
 DUS 2093: 2018  
12 © UNBS 2018  – All rights reserved  
 where  
χ  strength -reduction factor due to bend effect; and  
fu  ultimate tensile strength parallel to the fibers, (MPa).  
A.8 Report  
The test report should include the following items:  
A.8.1  Properties of concrete;  
A.8.1.1  The mixture proportions of cement, fine aggregate, coarse aggregate, admixture (if any used), 
and the w/c ratio.  
A.8.1.2  Slump of freshly mixed concrete as determined in accordance with US 1837.  
A.8.1.3  Twenty -eight -day strength of control cyli nders as determined in accordance with US 1834.  
A.8.1.4  Any deviation from the stipulated standards in such aspects as mixing, curing, dates of 
demolding, and testing of control cylinders.  
A.8.2  Trade name, shape, and date of manufacture, if available, and  lot number of FRP bar tested for 
stirrups.  
A.8.3  Type of fiber and matrix used in the FRP stirrup, and fiber volume fraction.  
A.8.4  Process used to fabricate the stirrups, as reported by the manufacturer.  
A.8.5  Numbers or identification marks of test stir rups.  
A.8.6  Designation, diameter, and cross -sectional area.  
A.8.7  Dimensions of concrete block, configuration (diameter and space) of steel stirrup confinement, 
debonded length, bend radius, and tail length of the bent bar.  
A.8.8  Preconditioning of FRP ba rs before casting.  
A.8.9  Date of test and test temperature.  
A.8.10  Type and capacity of load cell.  
A.8.11  Bend capacity and strength -reduction factor for each test stirrup.  
A.8.12  Average bend capacity and strength -reduction factor for all specimens that f ailed at the bend as 
intended  
 CDUS 2093: 2018  
© UNBS  2018 – All rights reserved  13 
 Certification marking  
Products that conform to Uganda standards may be marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licensed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in conjunction with the relevant Uganda Standard. The 
presen ce of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision, control and testing in accordance with the 
certification mark scheme of the Uganda National  Bureau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 CDUS 2093: 2018    
 
ICS 91.100.30 , 83.120  
Price based on nn pages  
© UNBS 2018 – All rights reserved