KENYA STANDARD  FDKS 2129 -2:2023 
ICS : 91.100.01  
2nd  Edition  
  
 © KEBS 202 3  
 Tile adhesive for marble, granite, 
ceramic and porcelain  
Part 2: Test methods  
 
 
  
TECHNICAL COMMITTEE REPRESENTATION  
The following organizations were represented on the Technical Committee:  
1. Bamburi Cement  
2. Dryche m Kenya Solutions Ltd.  
3. East African Portlan d Cement Company Plc  
4. Homalime  
5. Institute of Quantity Surveyors of Kenya  
6. Institution of Engineers of Kenya  
7. Kenya Builders & Concrete Co mpany  Ltd 
8. Micro  and small Enterprises A uthority 
9. Ministry of Transport, Infrastructure, Housing, Urban Development and Publi c Works  
10. Mlima Construction  
11. Mombasa Cement Ltd.  
12. Multimedia University of Kenya  
13. National Cement Limited  
14. Royal Automation Systems  
15. Savannah Cement  
16. SIKA  Kenya  
17. Technical Uni versity of Kenya   
18. Kenya Bureau of Standards — Secretariat  
 
REVISION OF KENYA STANDARDS  
In order to keep abreast of progress in industry, Kenya Standards shall be regularly reviewed.  Suggestions 
for impro vements to published standards, addressed to the Managing Director, Kenya Bureau of Standards, 
are welcome.  
© Kenya Bureau of Standards,202 3 
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 130 of 2001 of the Laws of Ke nya, copyright 
subsists in all Kenya Standards and except as provided under Section 25 of this Act, no Kenya Standard produced by Kenya Bure au of 
Standards may be reproduced, stored in a retrieval system in any form or transmitted by any means without prio r permission in writing 
from the Managing Director.DKS 2129 -2:2022 
 
 
 
 
Tile adhesive for marble, 
granite, ceramic and porcelain  
Part 2: Test methods  
Kenya Bureau of Standards, Popo Road, Off Mombasa Road,  
P.O. Box 54974 - 00200,  Nairobi, Kenya  
 +254 020 6948000, + 254 722202137, + 254 734600471  
 info@kebs.org  
 @KEBS_ke  
 kenya bureau of standards (kebs)   
Foreword  
 
This Kenya Standard was prepared by  the Cement Technical Committee under the guidance of the Standards 
Projects Committee, and it is in accordance with the procedures of the Kenya Bureau of Standards.  
This standard on tile adhesive complements already existing standards on cement and was fo und necessary 
following technological development on cement -based tile adhesive.  
Tile adhesive has wide application as it can be used to fix til es on any surface including glass. The product is 
flexible and does not shrink or crank due to physical, therma l and moisture movement or temperature 
changes. Above all, it prevents crazing and shedding of tiles. It is recommended to use tile grout to fill  tile 
joints once tile adhesive has been used to fix tiles to prevent seeping of water underneath the tiles.  
  
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1 Tile adhesive for marble, granite, ceramic and porcelain Part 2: Test methods  
 
1. Scope  
This  Standard specifies  the methods  for determining  characteristics  for adhesives  used in   internal  and external  
installation  of ceramic tiles.  
This  Standard  does  not contain  performance  requirements  or recommendations  for the design  and installation  of 
ceramic tiles.  
The following  test method s are  described:  
— determination  of open  time (8.1);  
 
— determination  of slip (8.2);  
 
— determination  of tensile  adhesion  strength  for cementitious  adhesives  (8.3);  
 
— determination  of shear  adhesion  strength  of dispersion  adhesives  (8.4);  
 
— determination  of shear  adhesion  strength  of reaction  resin  adhesives  (8.5);  
 
— determination  of transverse  deformation  of cementitious  adhesives  (8.6).  
 
NOT E Ceramic  tile adhesives  can be used  also for other  kinds  of tiles (natural  and agglomerated  stones,  
etc.),  if they do not adversely  affect  the stones.  
 
WARNING — This  Standard can involve hazardous materials and operations. Persons  using this standard 
should be familiar with normal laboratory practice. This  Standard  does not purport to address all the safety 
problems, if any,  associated with its use. It is the  responsibility of the user to establish appropriate safety and 
health practices and to ensure  compliance  with any  and national  regulatory  conditions.  
 
2. Normative  references  
The following documents, in whole or in part, a re normatively referenced in this document and are  
indispensable  for its application.  For dated  references,  only the edition  cited  applies.  For undated  
references,  the latest  edition  of the referenced  document  (including  any amendments)  applies.  
KS EAS 18 -1, Methods  of testing  cement  — Part 1: Determination  of strength  
 
KS 1780 -2, Building  lime  - Part 2:  Test methods  
EN 1067,  Adhesive s - Examination  and preparation  of samples  for testing  
 
EN 12004 -1, Adhesives  for ceramic  tiles  - Part  1: Requirements,  asses sment  and verification  of constancy  
of performance,  classification  and marking  
 
EN 14411,  Ceramic  tiles  - Definition,  classificatio n, characteristics,  assessment  and verification  of 
constancy  of performance  and marking  
 
ISO 15605,  Adhesives  - Sampling  (ISO  15605)  
 
3. Sampling  DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  2   Take  at least  2 kg sample  of the adhesive  in accordance  with ISO 15605  and EN 1067.  
 
4. Test  conditions  
  Standard  conditions  shall be (23 ± 2) °C and (50 ± 5) % relative  humidity  and the speed  of air in 
  the t testing  area less than  0.2 m/s. 
  The tolerance  in the time of conditioning  for all test  specimens  shall be as shown  in Table 1  below:  
Table  1 — Allowed  toler ance  in testing  time for all samples  requiring  conditioning  
 
Sample  Conditioning  Time  Allowed  tolerance  for testing  
6 h ±15 min  
7 d ±3 h 
14 d ±6 h 
21 d ±9 h 
28 d ±12 h 
Testing  shall  be performed  within  the specified  time  window.  
 
5. Test  materials  
5.1. Gener al 
Condition  all test materials for  at least  24 h under  standard  conditions.  
The adhesive  to be tested  shall  be within  its shelf  life, where  this is specified.  
5.2. Ceramic  tiles 
The tiles shall be checked prior to conditioning to ensure that they are unused, c lean and 
dry. The type of tile shall be as specified  under  the specific  test procedures  found  in 
Clause  8. 
5.3. Test substrate  
5.3.1.  Concrete  slab 
 
The concrete  slab shall be at least  35 mm thick,  have  a moisture  content  of less than 3 % by mass  
(carbide  method)  and have  a water  absorption  at the surface  after 4 h in the range  of 0,5 cm3 to 1,5 cm3. 
The tensile  adhesion  strength  shall be at least  1,5 N/mm2. 
The test surface  shall have  a finish  similar  to that obtained  by using  a wooden  float and be clean  
and dust-free at the time of the test. 
A method  for manufacturing  a suitable  concrete  test slab and the procedures  for measuring  the 
performances  are given  in Annex  A. 
5.3.2.  Other  substrates  
 
Other  substrates  may be used  upon  agreement  if the substrate  is recommended  for ceramic  tile 
application by the adhesive manufacturer. To demonstrate compatibility with other optional 
substrates,  the adhesive shall be applied to the selected substrate in accordance with the open time 
test method  (8.1).  When  the result  of > 0,5 N/mm2 is achieved  or cohesive  failure  occurs  in the 
substrate,  the requirement  is considered  satisfied.  
 
 FDKS 212 9-2: 202 3 
© KEBS 202 3 — All rights reserved  3 6. Mixing  of the adhesive  
The amount of wa ter and/or liquid admix required for preparing the cementitious adhesive shall be 
as stated by the manufacturer in parts by mass, i.e. liquid to dry powder (in the case where a range 
of values  is given,  the average  shall be used).  
Prepare a minimum quantit y of 2 kg of the adhesive in a mixer of the type described in KS EAS 18 -
1:2016,  4.4, using  the slow speed  settings  (140 ±  5) rotations  per min and (62 ± 5)  revolution  
planetary  movement.  
Carry  out the following  procedure:  
— pour the liquid  into the pan; 
 
— scatter the dry powder  over the liquid;  
 
— mix for 30 s;  
 
— take out the mixing  paddle;  
 
— scrape  down  the paddle  and pan within  1 min; 
 
— replace  the paddle  and mix for 1 min. 
 
Let the adhesive  mature  as specified  in the manufacturer's  instructions,  and then mix for a further  15 s. 
Where ready -to-use dispersion adhesives or reaction resin adhesives are to be used, the 
manufacturer's  instructions  shall be followed.  
 
7. Test report  
The test report  shall  provide  the following  information:  
a) the number  and year of issue  of this  Standard,  i.e. EN 12004 -2, and date of issue;  
 
b) the place,  date and time of sampling;  
 
c) type of adhesive,  commercial  designation  and manufacturer;  
 
d) identification  of test sample;  
 
e) handling  and storage  of samples  before  testing;  
 
f) test conditions;  
 
g) date of test; 
 
h) amount  of water  or liquid  used  for preparing  the adhesive  (for cementitious  adhesives);  
 
i) any other  factor  that could have  influenced  the result;  
 
j) test results  (individual  and mean  values  and mode  of failure  where  required):  
 
1) open  time;  
 
2) slip;  
3) tensi le adhesion  strength;  
 
4) shear  adhesion  strength;  DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  4  
5) transverse  deformation.  
 
8. Test methods  
8.1. Determination  of open  time  
8.1.1.  Test materials  
8.1.1.1.  Ceramic  tiles 
 
The tiles used for this method shall be glazed porous body tile complying with EN 14411, group BIII, 
of water ab sorption (15 ± 3) % by mass, with a thickness in the range 7 mm to 10 mm and a profile 
back  pattern  less than  0,25 mm  deep, cut to facial  dimensions of  (50 ±  1) mm x  (50 ± 1) mm. 
8.1.1.2.  Test substrate  
 
The concrete  slab shall comply  with the  requirements given  in 5.3.1.  
8.1.2.  Apparatus  
 
8.1.2.1.  Notched  trowel.  
 
A notched  trowel  having  6 mm x  6 mm notches at  12 mm centres.  
8.1.2.2.  Weight  (Mass).  
 
A mass  capable  of exerting  a force  of (20 ± 0,05)  N, with a cross -sectional  area of less 
than 50 mm x  50 mm. 
8.1.2.3.  Pull-head  plates.  
 
Square  metalli c plates,  with dimensions  of (50 ± 1) mm x (50 ± 1) mm and a minimum  
thickness  of 10 mm with  a suitable  fitting  for conne ction  to the test machine.  
8.1.2.4.  Test machine.  
 
A test machine  for direct  pull tensile  force  test and with suitable  capacity  and sensitivity  for the 
test. The machine shall be capable of applying the load to the pull -head plate at the rate of (250 ± 
50) N/s  through a suitable  fitting  that does not  exert  any bending  force.  
8.1.3.  Procedure  
 
Apply a  thin layer  of the adhesive,  mixed  in accordance  with Clause 6,  to the concrete slab with a  
straight  edge  trowel.  Then  apply  a thicker  layer  and comb  with the notched  trowel  (8.1.2.1).  
The trowel shall be held at an angle of approximately 60° to the substrate at a right angle to one 
edge of  the slab and drawn  across  the slab parallel  to that edge  (in a straight  line). 
After 5 min, 10 min, 20 min and 30 min place at least 10 test  tiles (8.1.1.1) 50 mm apart, on the 
adhesive  within  30 s.  The tiles are placed  on no more  than four ribs for all adhesives.  Load  
each  tile with (20 ± 0,05)  N for  30 s (8.1.2.2).  
After 27 d storage under standard conditions, bond the pull -head plates (8.1. 2.3) to the tiles with a  
suitable  high strength adhesive  (e.g. epoxide  adhesive).  
After a further 24 h storage under standard condition s determine the tensile adhesion strength of the  
adhesive  by applying  a force  increasing  at a constant  rate of (250 ± 50) N/s. 
 
8.1.4.  Evaluation  and expression  of results  
 
The individual  tensile  adhesion  strengths  are quoted  to the nearest  0,1 N/mm2 using  the following  FDKS 212 9-2: 202 3 
© KEBS 202 3 — All rights reserved  5 formula:  
As 
 L A (1) 
where  
As is the individual  tensile  adhesion  strength  in Newton  per square  millimetre;  
L is the total tensile  load in Newton;  
A is the bonding  area in square  millimetre  (2 500 mm2). 
The tensile  adhesion  strength  for each  time interval  is determine d as follows:  
— determine  the mean  of the 10 values;  
 
— discard  the values falling  outside  the range  of ± 20 % of the mean  value;  
 
— if five or more  values  remain,  determine  the new mean;  
 
— if less than five values  remain  repeat  the test; 
 
— determine  the mode  of failure  of the test units  according  to Annex  B as the predominant  mode.  
 
The open  time in minutes,  is the maximum  time interval  at which  the adhesive  meets  the tensile  
adhesion  strength requirement  defined  in EN 12004 -1. 
8.1.5.  Test report  
 
The information  listed  in Clause  7, items a)  to i) shall  be provided  plus item j)  1: open  time in minutes.  
8.2. Determination  of slip 
8.2.1.  Test materials  
8.2.1.1.  Ceramic  tiles 
 
The tiles used for this method shall be dry pressed ceramic tile in accordance with EN 14411, group  
BIa, with a water  absorption ≤ 0,5 %  by mass,  unglazed,  with plane  adhering  surface  and with facial  
dimensions  of (100 ± 1) mm x  (100 ± 1) mm, a mass  of (200 ± 10) g and a thickness  in the 
range  of 8 mm to  10 mm. 
8.2.1.2.  Test substrate  
 
The concrete  slab shall comply  with the requi rements  given  in 5.3.1.  
8.2.2.  Apparatus  
 
8.2.2.1.  Steel  straight  edge.  
 
8.2.2.2.  Clamps .  
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1  
8.2.2.3.  Masking  tape.  
 
A 25 mm wide  masking  tape.  
8.2.2.4.  Notched  trowel.  
 
A notched  trowel  having  6 mm x  6 mm notches at  12 mm centres.  
8.2.2.5.  Spacers.  
 
Two (25 ± 0,5) mm x (25 ± 0,5) mm x  (10 ± 0,5) mm thick  spacers made  from stainless  steel.  
8.2.2.6.  Weight  (Mass).  
 
A mass  capable  of exerting  a force  of (50 ± 0,1) N   with   a   cross -sectional   area   of   less   
than (100 ± 1) mm x  (100 ± 1) mm. 
8.2.2.7.  Vernier  caliper.  
 
A Vernier  caliper  accurate  to 0,01 mm.  
8.2.3.  Procedure  
 
Secu re the steel straight edge (8.2.2.1), with the clamps (8.2.2.2), at the top of the concrete slab so 
that its bottom edge  is horizontal  when  the slab is raised  to its vertical  position.  
Position 25 mm wide masking tape (8.2.2.3) immediately below the steel straight edge and apply a 
thin layer  of the adhesive  mixed  in accordance  with Clause  6 to the concrete  slab with a straight  
edge  trowel.  
Then apply a thicker layer of adhesive to the surface of the concrete slab so that it just overlaps the  
bottom edge of the masking tape. Comb the adhesive at right angles to the straight -edge with the  
notched  trowel  (8.2.2.4).  
The trowel shall be held at an angle of approximately 60° to the substrate and parallel to the straight  
edge.  
Immediately remove the masking tape, p osition 25 mm spacers (8.2.2.5) against the straight edge 
and after two minutes place the tile (8.2.1.1) against the spacers, as shown in Figure 1, and load 
with the  mass  of (50 ± 0,1) N (8.2.2.6).  
Measure  the gap between  the straight  edge  and the tile, in three points,  with the Vernier  caliper  
(8.2.2.7)  to within  ± 0,1 mm. 
After (30 ± 5) s remove the weight and the spacers and immediately and carefully lift the slab into a  
vertical  position.  After  (20 ± 2) min re-measure  the gap, as before,  in the same  three points.  
The maximum slip of the tile under its own mass is the difference between the two 
readings.  Carry  out the test for each  of 3 tiles, for each adhesive.  
Report  the results  in millimetres  and the mean  value.  
8.2.4.  Test report  
 
The information listed in C lause 7, items a) to i) shall be provided plus item j) 2: Slip in millimetre  
(individual  and mean  values).   
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1  
 
 
 
Key 
1 steel  straight  edge  
2 masking  tape 25 mm wide  
3 25 mm x  25 mm x 10 mm thick  spacers  
4 tile: 100 mm x 100 mm 
5 adhesive  
6 concrete  slab 
 
Figure  1 — Slip test 
 
8.3. Determination  of tensile  adhesion  strength  for cementitious  adhesives  (C) 
8.3.1.  Test materials  
8.3.1.1.  Ceramic  tiles 
 
The tiles used for this test shall be dry pressed ceramic tile in accordance with EN 14411, Group 
BIa, fully vitrifi ed, with a water absorption of ≤ 0,5 % by mass, unglazed and with a plain, matt, 
adhering  surface,  with facial  dimensions of  (50 ± 1) mm x  (50 ± 1) mm. 
8.3.1.2.  Test substrate  
DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  2  
The concrete  test substrate  shall conform  to requirements  given  in 5.3.1.  
8.3.2.  Apparatus  
 
8.3.2.1.  Weight (Mass).  
 
A mass  capable  of exerting  a force   of   (20 ± 0,05) N,   with  a   cross   sectional   area  of   less   
than 50 mm x  50 mm. 
8.3.2.2.  Pull head  plate.  
 
Square  metallic  plates,  with dimensions  of (50 ± 1) mm x (50 ± 1) mm and a minimum  thickness  
of 10 mm with a suitable  fitting  for connection  to the test machine.  
8.3.2.3.  Tensile  testing  apparatus.  
 
A test machine  for direct  pull tensile  force  test and with suitable  capacity  and sensitivity  for the 
test. The machine shall be capable of applying the load to the pu ll-head plate at the rate of (250 ± 
50) N/s  through  a suitable  fitting  that does not  exert  any bending  force.  
8.3.2.4.  Air circulating oven.  
 
An air-circulating  oven  capable  of controlling  the temperature  to within  ± 3 °C. 
8.3.2.5.  Notched  trowel.  
 
A notched  trowel  having  6 mm x 6 mm notches at  12 mm centres.  
8.3.3.  Procedure  
8.3.3.1.  Preparation  of test units  
 
Apply  a thin layer  of the adhesive,  mixed  in accordance  with Clause  6, to the concrete  slab with a 
straight  edge  trowel.  Then  apply  a thicker  layer  and comb  with a notched  trowel  (8.3.2.5). 
The trowel shall  be held at an angle  of approximately  60° to the substrate  at a right angle  to one 
edge  of the slab and drawn  across  the slab parallel  to that edge  (in a straight  line). 
After  5 min place  10 tiles (8.3.1.1)  on the adhesive  at a distance apart  of 50 mm and load each  tile 
with (20 ± 0,05)  N for  30 s. 
8.3.3.2.  Initial  tensile  adhesion  strength  
 
Prepare  the test units  in accordance  with 8.3.3.1.  
After 27 d storage under standard conditions bond the pull -head plates (8.3.2.2) to the tiles with a  
suitable  high strength adhesive  (e.g. epoxide).  
After a further 24 h storage under standard conditions determine the tensile adhesion strength of the  
adhesive  by applying  a force  at a constant  rate of (250 ± 50) N/s. 
If fast -setting properties of adhesives are to be tested, determine the tensile adhesion strength after 
six hours under standard conditions; the pull head plates shall be bonded a minimum of two hours 
before  determining  the tensile  adhesion  strength.  
Report  the results  in Newton.  
8.3.3.3.  Tensile  adhesio n strength  after  water  immersion  
 
Prepare  the test units  in accordance  with 8.3.3.1.  
Condition  the test units  under  standard  conditions  for 7 d, and immerse in  water  at the standard  
temperature.  FDKS 212 9-2: 202 3 
© KEBS 202 3 — All rights reserved  3 After 20 d remove the test units from the water, wipe with a cloth and bond the pull -head plates  
(8.3.2.2) to the tiles. After a further 7 h in standard conditions immerse the test units in water at the  
standard  temperature.  
The following day remove the test units from water and immediately carry out the tensile adh esion 
test in accordance  with 8.3.3.2.  
 
 
Report  the results  in Newton.  
8.3.3.4.  Tensile  adhesion  strength  after  heat ageing  
 
Prepare  the test units  in accordance  with 8.3.3.1.  
Condition the test units under standard conditions for 14 d and then place the units in a n air-
circulating  oven at (70 ± 3) °C for a further 14 d. Remove from the oven and bond the pull -head 
plates (8.3.2.2) to  the tiles with a  suitable  high strength  adhesive  (e.g. epoxide).  
Condition the test units for a further 24 h under standard conditions . Determine the tensile adhesion  
strength  in accordance  with 8.3.3.2.  
Report  the results  in Newton.  
8.3.3.5.  Tension  adhesion  strength  after  freeze–thaw  cycle  
 
Prepare  the test units  in accordance  with 8.3.3.1. In addition a  layer of  the adhesive  
approximately  1 mm  thick shall be applied with a straight edged trowel to the back face of the tile 
(8.3.1.1) before  placing.  
Condition  the test units for  7 d under standard conditions  and immerse in  water for  21 d before  
carrying  out 25 freeze –thaw  cycles.  
For each  freeze –thaw cycle:  
1) remove  the test units  from the water  and place  in a cold chamber  to achieve  a steady  
cabinet  
temperature  of (−15 ± 3) °C within  2 h ± 20 min; 
 
2) maintain  the test units at  (−15 ± 3) °C for 2 h ± 20 min; 
 
3) immerse  the test units  in water  at (20 ±  3) °C and raise  the temperature  to (15 ±  3) °C; 
 
4) maintain the  test units at (15 ± 3) °C  for a minimum  2 h before commencing the  next freeze –
thaw  cycle.  
 
Repeat  the cycle  25 times.  
After the last cycle remove the test units from water, wipe with a cloth and bond the pull -head plates  
(8.3.2.2) to the tiles. Condition the test units for a further 24 h under standard conditions and 
determine  the tensile  adhesion  strength in  accordance  with 8.3.3.2.  
Report  the results  in Newton.  
8.3.4.  Evaluation  and expression  of resul ts 
 
The individual tensile adhesion strength shall be determined to an accuracy of 0,1 N/mm2 using the  
following  formula:  
As 
 L A (2) 
where  
As is the individual  tensile  adhesion  strength  in Newton  per square  millimetre;  DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  4 L is the total load in Newton;  
A is the bonding  area in square  millimetre  (2 500 mm2). 
The tensile  adhesion  strength for  each  set of conditions  shall be determined  as follows:  
— determine  the mean  of the 10 values;  
 
— discard  the values  falling  outside  the range  of ± 20 % from the  mean  value ; 
 
— if five or more  than five values  remain,  determine  the new mean  value;  
 
— if less than five values  remain,  repeat  the test; 
 
— determine  the mode  of failure  of the test units according  to Annex  B as the  predominant  mode.  
8.3.5.  Test report  
 
The information  listed  in Clause  7, items  a) to i) shall be provided  plus item j) 3): Tensile  adhesion  
strength  for each condition  in Newton  per square  millimetre.  
8.4. Determination  of shear  adhesion  strength  of dispersion  adhesives  (D) 
8.4.1.  Test materials  
 
8.4.1.1.  Ceramic  tiles.  
 
The tiles used  for this method shall be glazed porous body tiles  in accordance with EN 14411, 
group  BIII,     with     a     water     absorption     (15 ± 3) %     by     mass,      with      facial      
dimensions      of  (108 ± 1) mm x (108 ± 1) mm, a thickness in th e range 7 mm to 10 mm and a 
profile back pattern less  than 0,25 mm thick.  
8.4.2.  Apparatus  
 
8.4.2.1.  Template.  
 
A smooth  non absorbent  frame  (e.g. polytetrafluoroethylene)  as shown  in Figure 2.   
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1  
 
Dimensions  in millimetres  
 
Key 
1 material:  PTFE  or similar  material  with non-stick properties;  hole diameter:  (14,3  ± 0,1) mm; thickness:  
(1,5 ± 0,1) mm; conventional  contact  area:  5 508 mm2 
 
Figure  2 — Template  (Dispersion  adhesives)  
 
8.4.2.2.  Spacers.  
 
Spacer  rods 0,8 mm diameter,  approximately  40 mm long. 
8.4.2.3.  Weight  (Mass).  
 
A mass  of less than 100 mm x 100 mm cross  sectional  area capable  of exerting  a uniform  
force  of (70 ± 0,15)  N. 
8.4.2.4.  Test machine.  
 
A test machine  with suitable  capacity  and sensitivity  for the test and with a variable  testing  speed.  
The machine  shall be capable  of applying  the load to the tile through a  suitable  jig (8.4.2.5).  
8.4.2.5.  Shear  test jig.  
 
DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  2 
A suitable  jig used  for converting  the compressive  or tensile  load exerted  by the testing  machine  into 
a shear  force.  Examples of  suitable  jigs are  shown  in Figures 3  and 4. 
 
Dimension s in millimetres  
 FDKS 212 9-2: 202 3 
© KEBS 202 3 — All rights reserved  3  
Key 
1 hardened  insert  
2 adjustable  jaws from  12 mm to 45 mm 
 
Figure  3 — Jig for shear  adhesion  test using  a compression  machine   
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1 
 
 
Dimensions  in millimetres  
 
 
 
Key 
1 test unit 
2 pressure  plate  
3 stops  
4 adapter  
5 “U” section  frame  
6 box section  frame 
 
Figure  4 — Jig for shear  adhesion  test using  a tensile  machine  
 
8.4.2.6.  Air circulating  oven.  
 
An air circulating  oven  capable  of controlling  the temperature  to within  ± 3 °C. 
8.4.3.  Procedure  
8.4.3.1.  Preparation  of test units  
 
Each  test unit shall be prepared  with two tiles (8.4.1.1).  
Draw  a straight  line on the porous  side of one tile 6 mm from the tile edge.  (To serve  as a guide  
DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  2 in overlapping  of the tile as explained  below.)  
Place  the template  (Figure  2) over the unglazed  back  of the first test tile. Trowel  sufficient  adhesive 
across  the template  and then screed  it clean  so as to  neatly  and completely  fill the holes  in the 
template.  
Carefully  remove  the template  vertically  (see Figure  5). 
Place  spacers  rods (8.4.2.2)  at each  corner  of the first tile, approximately  20 mm over the tile. 
 
After 2 min place a second standard test tile over the coated tile. Place it offset to provide an overlap  
between tiles with displacement of 6 mm, using the previously scribed line as a guide and ensuring 
that the edges of  the tiles are  parallel (Figure  5). 
Place the test units on a plane surface and carefully load with (70 ± 0,15) N for 3 min. Carefully 
remove  the spacer  rods,  without  disturbing  the relative  position  of the tiles in  the test units.  
Dimensions  in millimetres  
 
Key 
1 spacer  rods 
2 ceramic  test tile 108 mm x 108  mm 
3 direction  of application  of load 
4 guide  line 
5 adhesive  
 
Figure  5 — Preparation  of tile test unit (Dispersion  adhesives)  
 
A total of 10 test units are required for each test.  
Condition  the units  according  to the test require ments. 
8.4.3.2.  Initial  shear  adhesion  strength  
 
Condition  10 test units in  standard  test conditions  for 14 d. 
FDKS 212 9-2: 202 3 
© KEBS 202 3 — All rights reserved  3 After  conditioning  has been  completed,  place  the test units  in a shear  test jig (8.4.2.5)  and apply  a 
shear  force  by moving  the crosshead  at a speed  of (5 ± 0,5) mm/min  until failure  occurs.  
Report  the results  in Newton.  
8.4.3.3.  Adhesion  strength  after  water  immersion  
 
Condition  10 test units  in standard  test conditions  for 7 d, then immerse  in water  at standard  
temperature  for 7 d. Remove  the units and  wipe  with a cloth and  test them  as described  in 8.4.3.2.  
Report  the results  in Newton.  
 
 
NOTE  This test is only for dispersion  adhesives  used  in internal  installations  subject  to wet conditions.  
 
8.4.3.4.  Shear  adhesion  strength  after  heat ageing  
 
Condition  10 test units  in standard conditions  for 14 d and then place  them  in an air-circulating  oven  
at (70 ± 3) °C for a further  14 d, ensuring  that air is free  to circulate  around  each test  unit. 
Condition the units for a further 24 h in standard conditions and test them as descr ibed in 
8.4.3.2.  Report  the results in  Newton.  
8.4.3.5.  Shear  adhesion  strength  at elevated  temperature  
 
Use the procedure  described  in 8.4.3.4  but test the tile adhesion  within  1 min after removal  of the test 
unit from the  air circulating  oven.  
Report  the results  in Newton.  
8.4.4.  Evaluation  and expression  of results  
 
Divide  the individual  values  in Newton  by the conventional  area (5 508  mm2) of adhesive  contact.  
The individual  values  are quoted  to 0,1 N/mm2. 
The shear  adhesion  strength  is determined  in the following  way: 
— determine  the mean  of 10 values;  
 
— discard  the values  falling  outside  the range  of ± 20 % from the  mean  value;  
 
— if five or more  values  remain,  determine  the new mean  value;  
 
— if less than five values  remain,  repeat  the test. 
8.4.5.  Test report  
 
The information  listed in Clause  7, items  a) to i) shall  be provided  plus item  j)  4: Shear  
adhesion  strength  for each condition  in Newton  per square  millimetre.  
8.5. Determination  of shear  adhesion  strength  of reaction  resin  adhesives  (R) 
8.5.1.  Test materials  
8.5.1.1.  Ceramic  tiles 
 
The tiles used for this method shall be fully vitrified tiles in accordance with EN 14411, group BI a, 
with a  water absorption ≤ 0,5 % by mass, unglazed and with plane adhering surface with facial 
dimensions of  (100 ± 1) mm ×  (100 ± 1) mm and  a thickness in  the range  8 mm to  10 mm. 
8.5.2.  Apparatus  
 
8.5.2.1.  Template.  DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  4 
 
A smooth  non-absorbent  frame  (e.g. polytetrafluoroethylene)  in accordance  with Figure  6. 
 
Dimensions  in millimetres  
 
Key 
1 material:  PTFE  or similar  material  with non-stick properties;  hole diameter:  (15,0  ± 0,1) mm; thickness:  
(1,5 ± 0,1) mm; conventional  contact  area:  1 660 mm2 
 
Figure  6 — Template  for the prepar ation  of tile test unit 
 
8.5.2.2.  Spacers.  
 
Spacer  rods 0,8 mm diameter,  approximately  40 mm long. 
8.5.2.3.  Weight  (Mass).  
 
A mass  of less than 100 mm x 100 mm cross  sectional  area capable  of exerting  a uniform  
force  of (70 ± 0,15)  N. 
8.5.2.4.  Test machine.  
 
A test machine  with suitable capacity  and sensitivity  for the test and with a variable  testing  speed.  The 
machine  shall  be capable  of applying  the load to the tile through a  suitable  jig (8.5.2.5).  
8.5.2.5.  Shear  test jig.  
 
A suitable  jig used  for converting  the compressive  or tensile  load exerted  by the testing  machine  
into a shear  force.  Examples of  suitable  jigs are  shown  in Figures  3 and 4. 
8.5.2.6.  Air circulating  oven.  
 
An air circulating  oven  capable  of controlling  the temperature  to within  ± 3 °C. 
8.5.3.  Procedure  FDKS 212 9-2: 202 3 
© KEBS 202 3 — All rights reserved  5 
8.5.3.1.  Preparation  of test units  
 
Each  test unit shall be prepared  with two tiles (8.5.1.1).  
 
 
Draw  a straight  line on the porous  side of one tile 6 mm from the tile edge.  (To serve  as a guide  
in overlapping  of the tile as explained  below.)  
Place  the template  (Figure 6)  over the unglazed  back  of the first test tile. Trowel  sufficient  adhesive  
across  the template  and then screed  it clean  so as to  neatly  and completely  fill the holes  in the 
template.  
Carefully  remove  the template  vertically  (see Figure  7). 
Place  spacers  rods (8.5.2.2)  at each  corne r of the first tile, approximately  20 mm over the tile. 
Dimensions  in millimetres  
 
Key 
1 spacer  rods 
2 ceramic  test tile 100 mm x 100  mm 
3 direction  of application  of load 
4 guide  line 
5 adhesive  
 
Figure  7 — Preparation  of tile test unit 
 
After 2 min place a second  standard test tile over the coated tile. Place it offset to provide an overlap  
between tiles with displacement of 6 mm, using the previously scribed line as a guide and ensuring 
that the edges of  the tiles are  parallel  (Figure  7). 
Place the test units on a plane surface and carefully load with (70 ± 0,15) N for 3 min. Carefully 
remove  the spacer  rods,  without  disturbing  the relative  position  of the tiles in  the test units.  
A total of 10 test units  are required  for each test.  
Condition  the test pieces  in the standard  test conditions  for 7 d and then according  to the test 
requirements.  DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  6 8.5.3.2.  Initial  shear  adhesion  strength  
 
Place the test pieces in the shear test jig (8.5.2.5) and apply a shear force by moving the crosshead 
at a speed  of (5 ± 0,5) mm/min  until failure occurs.  
 
Report  the results  in Newton.  
8.5.3.3.  Shear  adhesion  strength  after  water  immersion  
 
Immerse  the 10 test pieces  in water  at (23 ±  2) °C for 21 d. Remove  the test pieces,  wipe with a 
cloth  and test them as described  in 8.5.3.2.  
Report  the results  in Newton.  
8.5.3.4.  Shear  adhesion  strength  after  thermal  shock  
 
Place  the 10 test pieces  in a waterbath  maintained  at (23 ± 2) °C for 30 min and then in a (100 ±  2) °C 
waterbath  for a further  30 min.  
Repeat  the cycle  for a total of four times  and then place  the test pieces  in the (23 ± 2) °C bath for 
approximately  30 min for cooling.  
Remove each test piece from the water, wipe off the excess water and test as described in 
8.5.3.2.  Report  the result  in Newton.  
8.5.4.  Evaluation  and expression  of results  
 
Divide  the individual  values  in Newton  by the conventional  area (1 660 mm2) of adhesive  contact.  The 
individual  values  are quoted  to 0.1 N/mm2. 
The shear  adhesion  strength  is determined  in the following  way: 
— determine  the mean  of 10 values;  
 
— discard  the values falling  outside  the range  of ± 20 % from the  mean  value;  
 
— if five or more  values  remain,  determine  the new mean  value;  
 
— if less than five values  remain,  repeat  the test. 
8.5.5.  Test report  
 
The information  listed  in Clause  7, items  a) to i) shall  be provided  plus item  j)  4: Shear  adhesion  
strength  for each condition  in Newton  per square  millimetre.  
8.6. Determination  of transverse  deformation  of cementitious  adhesives  (C) 
8.6.1.  Principle  
 
The test described in this  Standard measures the transverse deformation of cementitious  adhesives  
when  subjected  to a 3-point  bending  load,  performed  on test specimens  of the stated  dimension.  
NOTE  Transverse deformation is used to evaluate the deformability of the adhesive, i.e. its capacity to be  
deformed by  stresses  between  the tile and the  fixing surfac e without  damage  to the installed  surface.  
 
8.6.2.  Test materials  
 
8.6.2.1.  Substrate.  
 
A polyethylene  film of minimum thickness  0.15 mm. 
8.6.2.2.  Plastic  container.  FDKS 212 9-2: 202 3 
© KEBS 202 3 — All rights reserved  7  
A plastic  container that is  capable  of being  sealed  to make it air tight,  with an  internal  volume  of 
(26 ± 5) I, e.g. a container  with dimensions  (600 ±  20) mm  ×  (400 ± 10) mm × (110 ± 10) mm. 
8.6.2.3.  Support.  
 
 
Rigid,  smooth  and flat support  for the polyethylene  film. 
8.6.3.  Apparatus  
 
8.6.3.1.  Anvil.  
 
A metallic  construction  conforming  to the dimensions  of Figure  8. 
8.6.3.2.  Test jig. 
 
Two metalli c cylindrical  supports,  of diameter  (10 ± 0,1) mm, spaced  (200 ± 1) mm centre  to centre,  of 
length  60 mm minimum.  See Figure  9. 
8.6.3.3.  Template A.  
 
A smooth,  rigid,  non absorbent  rectangular  frame  of internal  dimensions  (280 ±  1) mm ×  (45 ± 1) 
mm and thickness (5  ± 0,1) mm; e.g. made  from polytetrafluoroethylene  (PTFE)  or metal.  
A round  hole of approximately  2 mm diameter  drilled  at each  internal  corner  is recommended  to ease  
production  of the test piece.  See Figure  10. 
8.6.3.4.  Template  B. 
 
A smooth,  rigid,  non-absorbent  mould  (see Figure 11)  or similar  device  capable  of producing  a 
test specimen  of dimensions (300  ± 1) mm ×  (45 ± 1) mm ×  (3 ± 0,05)  mm. 
8.6.3.5.  Test machine.  
 
The test machine  shall  be a press,  capable  of applying  the anvil (8.6.3.1)  to the test piece  at a 
rate of 2 mm/min.  
8.6.3.6.  Flow  table.  
 
The flow table  used  for the compaction  of (280 ± 1) mm ×  (45 ± 1) mm × (5 ± 0,1) mm specimen  
shall comply  with KS 1780 -2.  
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1 
 
Dimensions  in millimetres  
 
 
Figure  8 — Anvil  
 
Dimensions  in millimetres  
 
 
 
Key 
1 cylindrical  support,  diamete r (10 ± 0,1) mm,  length  60 mm minimum  
2 adhesive  (3 ± 0,1) mm thick 
 
Figure  9 — Test jig  
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1 
 
 
Dimensions  in millimetres  
 
 
Figure  10 — Template  A 
 
Dimensions  in millimetres  
 
 
Figure  11 — Template  B 
 
8.6.4.  Procedure  
8.6.4.1.  Preparation  of substrate  
 
Fix the polyethylene  film (8.6.2.1)  firmly  to the rigid support  (8.6.2.3),  ensuring  the surface,  to 
which  the adhesive  is to be applied,  is not  distorted,  e.g. without  pleats  or wrinkles.  
8.6.4.2.  Preparation  of test units  
 DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  2 Hold the template  A (8.6.3.3)  firmly  onto the polyethylene  film. 
Trowel  sufficient  adhesive  across  the template  and then screed  clean  so as to neatly  and 
completely  fill the hole in the template.  
Clamp  the mould  firmly  to the flow table  and compact  the sample  using  70 jolts. 
Lift the mould  gently  from the flow table  and carefully  remove  the template  vertically.  
Apply a layer of release agent to the template B (8.6.3.4) and position it centrally over the specimen.  
Load the template with a weight capable of exerting a force of (100 ± 0,1) N and an approximate 
cross - sectio nal area of (290 × 45) mm. The applied pressure ensures that the material fully fills the 
recess of  the template to the required thickness. Remove any excess material from the sides of the 
template and  one hour later remove  the weight.  
After 48 h remove th e template 
B. Prepare  six samples  for each  
test. 
Condition  the units  according  to the test requirements.  
8.6.4.3.  Conditioning  
 
Immediately  after the removal  of template  B place  six specimens,  on the support,  horizontally  into 
the plastic  container  (8.6.2.2)  and make it air tight. 
Condition  the test units  at (23 ± 2) °C. After  12 d remove  them  from the plastic  container  and 
condition  them for  14 d in air in standard  conditions.  
8.6.4.4.  Transverse  deformation  
 
After conditioning has been completed, remove the specimens from the polyethylene film and 
measure  their thickness,  using  a caliper  with 0,01 mm  precision,  at three  positions,  i.e. in the 
middle  and (50 ± 1) mm from each end. If the three values fall within the required tolerance of (3,0 ± 
0,1) mm,  calculate  the average  value;  discard  any specimen  which  falls outside  the required  
permissible  thickness. If a test specimen has a raised, burr edge along one or both of the long 
dimensions as an  artefact of the removal of excess material in 8.6.4.2, it is permissible to gentl y 
sand the burr edge using  an ISO 6344 compliant sandpaper of P120 grit. Only the burr edge may be 
sanded and the sample shall  otherwise fully meet the thickness criteria. Unless removed, the burr 
edges can create variation in test  results.  
Place the test sample on the test jig (Figure 9). Orient the test sample so that any natural curve in 
the test specimen  points down,  away  from the  anvil.  
The starting point is defined when the anvil touches the sample. Deform the sample, from the 
starting  point,  with a  transverse  load applied  by the anvil at a rate of 2 mm/min  until failure.  
Record the deformation from the starting point, in millimetre. When no cracking occurs, report the  
maximum  force  and deformation.  
Repeat the test on the other test pieces. Test data f rom specimens with transverse deformation 
values  that deviate by ± 20 % from the calculated average should be excluded. A minimum of 3 
remaining test  specimens  is required.  
8.6.4.5.  Evaluation  and expression  of results  
 
The transverse  deformation  is determined  to 0,1 mm, by calculating  the average  value  of the 
deformations  obtained  in the test. 
8.6.5.  Test report  
 
The information  listed  in Clause  7, items  a) to i) shall  be provided  plus item j) 5: Transverse  
deformation  in millimetres.   
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1  
 
Annex  A 
(normative)  
 
Concrete  slab for test 
 
 
A.1 General  information  
A concrete  test slab suitable  for the adhesive  tests  described  in this standard  may be manufactured  
and tested  using  these  described  procedures.  Other  concrete  products  meeting  the requirements  
listed  in 
5.3 may be utilized. 
 
 A.2 Test conditions  
Test conditions  listed  in Clause  4 shall apply.  
 
 A.3Apparatus  
 A.3.1   Pull-head  plates.  
Square  metallic  (e.g. steel,  aluminium)  plates,  with dimensions  of (50 ± 1) mm x (50 ± 1) mm and a 
minimum  thickness of  10 mm with a  suitable  fitting for connection  to the tensile  testing  machine.  
 A.3.2  Tensile  testing  machine.  
 
The machine  shall be capable  of applying  the load to the pull-head  plate  at the rate of (250 ± 50) N/s, 
through  a suitable  fitting  that does not  exert  any bending  force.  
 A.3.3   Carsten -Röhrchen  flask.  
 
Carsten -Röhrchen flask or other suitable apparatus for measuring the water absorption at the surface of  
the concrete  slab (see Figure  A.1). 
 
 A.4 Concrete  slab 
 A.4.1Manufacture  of the concrete  slab 
The specification  (see 5.3 .1) can be achieved  by using  the following  procedure  to manufacture  the 
concrete  slab: 
— binder:  Portland  cement  type CEM  I 42,5 R in accordance  with EN 197 -1; 
 DKS 2129 -2: 202 3 
 
© KEBS 202 3 — All rights reserved  2 — aggregate: gravel sand, of 0 mm to 8 mm particle size, continuous grading curve between A 
and B  (see Figure A.2);  
 
— mix ratio binder  and aggregate:  1:5 in proportion  by mass;  
 
— ultrafines content per cubic meter of ready mixed concrete: 500 kg/m3 prepared concrete. The  
concrete shall contain ultrafines in order to be properly workable and have a closed struct ure; 
the ultrafines  content  consists of  cement  and aggregate  particle  size up to 0,125  mm; 
 
— water/cement  ratio:  0.5 by mass;  
 
— manufacture:  vertically  or horizontally  in moulds,  avoid  the use of any mould  release  agent;   
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1  
— compaction:  90 s on a vibrati ng table at 50 Hz. 
 A.4.2Conditioning  of the concrete  slab 
The slabs  shall  be stored  for 24 h under  standard  conditions,  followed  by six days  water  
immersion  at (20 ± 2) °C. 
Before  being  tested  the concrete  slabs  shall be stored  separately,  in vertical  position, in a dry and 
ventilated  environment,  for at least  three  months and  conditioned  for 24 h under  standard  conditions.  
 A.4.3  Water  absorption  at the  surface  
Water  absorption  at the surface  of the concrete  slab shall  be determined  by the following  method : 
a) bond  a graduated glass  measuring  tube (Carsten -Röhrchen flask)  to the concrete  slab by 
means  of a suitable  sealant;  
 
b) after the sealant  has cured,  fill the measuring  tube with water,  to the upper  level;  
 
c) record  the water  level every  60 min during  the 4 h of the test, and draw  the absorption  
as a function  of time;  
 
d) perform  at least  3 tests  on a reference  concrete  slab from each  batch.  
 A.4.4  Tensile  adhesion  strength  
The tensile adhesion strength shall be determined by bonding at least five pull head plates  (A.3. 1) 
directly  to the slab,  e.g. with an epoxide  resin,  and determining  the tensile  adhesion  strength  by 
applying  a force  which  increases at  a constant  rate of (250 ±  50) N/s. 
 A.4.5  Data  recorded  
The following  items  shall be recorded:  
a) description  of the conc rete slab,  and reference  to the batch;  
 
b) handling  and storage  of concrete  slabs  before  testing;  
 
c) water  absorption  of concrete  slab,  representative  of the batch;  
 
d) moisture  content  of the concrete  slabs,  representative  of the batch;  
 
e) tensile  adhesion  strength  of concrete  slab,  representative  of the batch;  
 
f) any other  factor  that might  have  influenced  the result;  
 
g) date of the test.  
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1 
 
 
Dimensions  in millimetres  
 
Key 
* area = 706.5 mm2 
 
Figure  A.1 — Example  of apparatus  for evaluating  water  absorption   
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1 
 
 
 
Key 
X nominal opening size in 
millimetres  Y undersize  as a 
percentage  by mass  
 
Figure  A.2 — Grading  curves  for 8 mm maximum  particle  size  
 
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1 
 
 
Annex  B(normative)  
Failure  patterns  
 B.1 Adhesion  failure  (AF-S or AF -T) 
When failure occurs  at the interface between adhesive and substrate the notation AF -S is used, when it  
occurs between tile and adhesive the notation AF -T is used and in both cases the test values equal the  
adhesion  strength (see  Figure  B.1 and Figure  B.2). 
In some cases fail ure can occur in the adhesive layer between the tile and the pull -head plate. In this  case 
the notation BT is used, see Figure B.3, and the adhesion strength is greater than the test value. The  test 
should  be preferably  repeated.  
 
 
 
Key 
1 pull head  plate  
2 tile 
3 adhesive  
4 substrate  (concrete  slab)  
 
Figure  B.1 — Adhesive  failure  between  adhesive  and substrate  (AF-S)  
KENYA STANDARD                        FDKS 2129 -2:2023 
 
© KEBS 20 23 — All rights reserved  1 
 
 
 
Key 
1 pull head  plate  
2 tile 
3 adhesive  
4 substrate  (concrete  slab)  
 
Figure  B.2 — Adhesive  failure  betwee n tile and adhesi ve (AF-T) 
 
Key 
1 pull head  plate  
2 tile 
3 adhesive  
4 substrate  (concrete  slab)  
 
Figure  B.3 — Adhesive  failure  between  tile and pull head  plate  (BT)  
 
 B.2 Cohesive  failure  within  the adhesive  (CF-A) 
When  failure  occurs  within  the adhesive  layer  (see Figure  B.4). 
KS 2 129-2:2023   
 
© KEBS 202 3– All right s reserved   
  
 
 
 
Key 
1 pull head  plate  
2 tile 
3 adhesive  
4 substrate  (concrete  slab)  
 
Figure  B.4 — Cohesive  failure  within  the adhesive  (CF-
A) 
 
 B.3 Cohesive  failure  in the substrate  or in the tile (CF-S or CF-T) 
When failure  occurs  within the substra te the notation CF -S is used,  see Figure B.5;  
when it happens  within  the body  of the tile the notation  CF-T is used  (see Figure  B.6). 
NOTE  In this case  the strength  of the adhesive  is greater  than the test value.  
 
Key 
1 pull head  plate  
2 tile 
3 adhesive  
4 substra te (concrete  slab)  
 
Figure  B.5 — Cohesive  failure  within  the substrate  (CF-S)