ICS 91.080.30   
 
Reference number  
DRS  211-5: 2021  
© RSB 2021  
  
 RWANDA 
STANDARD  DRS  211-5  
 
Second  edition  
2021 -mm-dd 
Mortar for masonry — Test method s —  
Part 5:  
Determination of flexural and compressive 
strength of hardened mortar  
   
DRS 211-5: 2021  
©RSB 2021  - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition 
 
 
 
 
 
 
 
 
© RSB 2021  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reproduce this document should be addressed to : 
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
KK 15 Rd, 49  
Tel. +250 788303492  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw   DRS 211-5: 2021  
iii                ©RSB 2021  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  1 
4 Principle  ................................ ................................ ................................ ................................ ........  1 
5 Apparatus  ................................ ................................ ................................ ................................ ...... 1 
6 Sampling  ................................ ................................ ................................ ................................ ....... 2 
6.1 General  ................................ ................................ ................................ ................................ ..........  2 
6.2 Laboratory prepared mortars  ................................ ................................ ................................ ...... 2 
6.3 Mortars, other than laboratory prepared mortars  ................................ ................................ ..... 3 
7 Preparation and storage of test specimens  ................................ ................................ ..............  3 
7.1 General  ................................ ................................ ................................ ................................ ..........  3 
7.2 Preparation  ................................ ................................ ................................ ................................ .... 3 
7.2.1  General  ................................ ................................ ................................ ................................ ..........  3 
7.2.2  Mortars with h ydraulic binders, and air -lime/cement mortars with mass of air -lime not 
exceeding 50 % of the total binder mass  ................................ ................................ ...................  3 
7.2.3  Mortars base d on air -lime, and air -lime/cement mortars with cement mass not exceeding 
50 % of the total binder mass  ................................ ................................ ................................ ...... 4 
7.3 Storage and curing conditions  ................................ ................................ ................................ ... 4 
8 Determination of flexural strength  ................................ ................................ ..............................  5 
8.1 Apparatus  ................................ ................................ ................................ ................................ ...... 5 
8.2 Procedure  ................................ ................................ ................................ ................................ ...... 7 
8.2.1  Preparation  ................................ ................................ ................................ ................................ .... 7 
8.2.2  Loading  ................................ ................................ ................................ ................................ ..........  7 
8.3 Calculation and expression of results  ................................ ................................ .......................  7 
9 Determination of compressive strength  ................................ ................................ ....................  8 
9.1 Apparatus  ................................ ................................ ................................ ................................ ...... 8 
9.2 Procedure  ................................ ................................ ................................ ................................ ...... 8 
9.2.1  Preparation  ................................ ................................ ................................ ................................ .... 8 
9.2.2  Loading  ................................ ................................ ................................ ................................ ..........  9 
9.3 Calculation and expression of results  ................................ ................................ .......................  9 
9.4 Test report  ................................ ................................ ................................ ................................ ..... 9 
Annex  A (normative)  Description  of metal moulds for specimen preparation  ................................  10 
A.1 General  ................................ ................................ ................................ ................................ ........  10 
Annex  B (normative)  Suggested loading rates for different classes of masonry and rendering 
mortars  ................................ ................................ ................................ ................................ ........  12 
 DRS 211-5: 2021  
©RSB 2021  - All rights reserved                  iv 
 Foreword  
Rwanda Standard s are prepared  by Technical Committees and approved by Rwanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda S tandards adopted 
by technical  committ ees are ratifie d by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 211-5 was prepared by Technical Committee RSB/TC 009, Civil engineering and building materials . 
In the preparation of this standard, reference was made to the fo llowing standard s: 
1) BS EN 998 -1: 2016 , Specification for mortar for masonry — Part 1: Rendering and plastering mortar  
2) BS EN 998 -2: 2016 , Specification for mortar for masonry — Masonry mortar   
3) BS EN 1015 -2:1999+A1:  2006 , Methods of test for mortar for masonry – Part 2: Bulk sampling of mortars 
and preparation of test mortars  
4) BS EN 1015 -3: 1999 , Methods of test for mortar for masonry – Part 3: Determination of consistence of fresh 
mortar (by flow table)  
5) BS EN 1015 -11:2019 , Methods of test for mortar for masonry – Part 11: Determination of flexural and 
compressive strength of hardened mortar  
The assistance de rived from the above source is hereby acknowledged with thanks.  
This second edition cancels and replaces the first ed ition (RS  211-5: 2010), clauses 6, 7, 9, Table 1, Figures 1 
and A.1 and Annex A, of which have been technically revised.  
DRS 211 consists of the following parts, under the general title Mortar for masonry  — Test method s: 
⎯ Part 1: Determination of particle size distribution (by sieve analysis)  
⎯ Part 2: Bulk sampling of mortars and preparation of test mortars  
⎯ Part 3: Determination of consistence of fresh mortar (by flow table)  
⎯ Part 4: Determination of consistence of fresh m ortar (by plunger penetration)  
⎯ Part 5: Determination of flexural and compressive strength of hardened mortar  
⎯ Part 6: Determination of adhesive strength of hardened rendering and plastering mortars on substrates  
⎯ Part 7: Determination of water absorption c oefficient due to capillary action of hardened mortar  DRS 211-5: 2021  
v                ©RSB 2021  - All rights reserved  
 Committee membership  
The following organizations were represented on the Technical Committee on Civil engineering and b uilding 
materials (RSB/TC 009)  in the preparation of this standard.  
Advanced Construction Technology Services (ACTS) - Rwanda  
CIMERWA   
City of Kigali   
Green Pact Africa   
Rwanda Inspectorate, Competition and Consumer Protection Authority (RICA)  
RTDA   
Standard Geotechnical Engineering and Construction Ltd (STAGECO Ltd)  
SJEC Ltd  
UR-CST  
Rwanda Standards Board (RSB) – Secretariat   DRS  211-5: 2021  
1                ©RSB 2021  - All rights reserved  
 Mortar for masonry — Test method s — Part 5: Determination flexural and 
compressive strength of hardened mortar   
1 Scope  
This Draft Rwanda Standard provides  a method for determining the flexural and compressive strength of 
moulded mortar specimens.  
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.  
DRS 211-1, Mortar for masonry — Test method s — Part 1, Determination of particle size distribution (by sieve 
analysis)  
DRS 211-2, Mortar for masonry — Test method s — Part 2: Sampling of mortars and preparation of test 
mortars  
DRS 211 -3, Mortar for masonry — Test methods — Part 3:   Determination of consistence of fresh mortar (by 
flow table)  
RS 108 , Mortar for masonry — Specification  
3 Terms and definitions  
For the purposes of this standard, the following term and definition apply.  
air-lime  
lime mainly consisting of calcium oxide or hydroxide which slowly harden in air by reacting with atmospheric 
carbon dioxide. Generally, they do not harden under water as they have no hydraulic properties.  
4 Principle  
The flexural strength of mortar is deter mined by three points loading of hardened moulded mortar specimens 
to failure. The compressive strength of the mortar is determined on the two parts resulting from the flexural 
strength test. Where the flexural strength is not required, the parts for compr essive strength testing can be 
produced from the specimens in any way which does not lead to these parts being damaged.  
5 Apparatus  
5.1 Metal moulds , consisting of an open frame of removable walls forming three compartments when 
assembled (see Figure 1 for  typical design and annex A for a detailed description).   
©RSB 2021  - All rights reserved                  2 
 5.2 A tamper , consisting of a rigid, non -absorptive rod of square cross -section, each side of which is 12 m m 
+ 1 mm. The tamping face is flat and at right angles to the length of the tamper. The mas s of the tamper is 50 
g + 1g.  
5.3 Storage chambers , capable of maintaining a temperature of 20 °C (+3 °C/ -2 °C) and a relative humidity 
of 95 % + 5 % or 65 % + 5 %.  
5.4  A clamp , enabling the assembled mould frames to be kept together at right angles.  
5.5 White cotton gauze , four sheets each with a size of approximately 150 mm x 175 mm.  
5.6 Absorbent filter paper , with a specific mass of 200 g/m 2 + 20 g/m 2 and water absorption   capacity of 
160 g/m 2 + 20 g/m 2; twelve sheets each with a size of approximately 150 mm + 175 mm.   
5.7 Polyethylene bags , capable of containing the steel moulds.  
5.8 Two glass plates , of sufficient area to cover the steel mould.  
5.9 A palette knife.  
5.10 A grid , with webs of triangular section providing point contact support for storing and curing the 
specimens.  
5.11 A trowel  
Additional apparatus is described in 8.1 and 9.1.  
6 Sampling  
6.1 General  
6.1.1  The fresh mortar for this test shall have a minimum volume of 1.5 L or at least 1.5 times the quantity 
needed to perform the test, whichever is the greater, and shall be obtained either by reduction of the bulk test  
sample (see DRS 211-2) using a sample divider or by quartering, or by preparation fr om dry constituents and 
water in the laboratory. Two test samples shall be prepared.  
6.1.2  The mortar shall be brought to a defined flow value as specified in DRS 211 -2 determined in accordance 
with DRS 211 -3 or DRS 211 -4 and reported.  
6.1.3  Before testing, the batch shall be gently stirred by hand using a trowel or palette knife in 5 s to 10 s to 
counteract any false setting, etc., but without any additional mixing of the batch.  
6.2 Laboratory prepared mortars   
6.2.1  The length of the mixing period shal l be measured from the moment all the constituents are introduced 
into the mixer. The test procedure shall start after mixing but shall be concluded within the specified workable 
life of the mortar (preferably within 30 min after completion of mixing).  DRS  211-5: 2021  
3                ©RSB 2021  - All rights reserved  
 6.2.2  Any deviation from the mixing procedure shall be noted.   
6.3 Mortars, other than laboratory prepared mortars  
Ready to use mortars (factory -made wet mortars which are retarded), and pre -batched air -lime/sand wet 
mortars when not gauged with hydraulic binde rs, shall be used for specimen preparation within their specified 
workable life.  
7 Preparation and storage of test specimens  
7.1 General  
The test specimens shall be specimens of 160 mm x 40 mm x 40 mm. Three specimens shall be provided. For 
the compressive stre ngth test, break the specimens into two halves to provide six half specimens .  
7.2 Preparation  
7.2.1  General  
7.2.1.1 Prepare mortars based on hydraulic binders (retarded or not retarded), and air -lime/cement mortars 
with mass of air -lime not exceeding 50 % of the total binder mass, in accordance with 7.2.2.  
7.2.1.2 Prepare mortars based on air -lime, and air -lime/cement mortars with cement mass not exceeding 
50 % of the total binder mass, in accordance with 7.2.3.   
7.2.1.3  Preparation and storage conditions are gi ven in Table 1.   
7.2.1.4 Prepare three specimens for testing at an age of 28 days, or more if retarding agents are 
incorporated in the mortar, unless otherwise specified.  
7.2.1.5  Clean the moulds and lubricate the internal faces of the assembled moulds with a thin layer of 
mineral based oil that does not affect setting of mortars, to prevent adhesion of the mortar.  
7.2.2  Mortars with hydraulic binders, and air -lime/cement mortars with mass of air -lime not 
exceeding 50 % of the total binder mass  
7.2.2.1 Fill the mould with mortar in two approximately equal layers, each layer being compacted by 25 
strokes of the t amper. Alternatively, the mould may be tilted through approximately 30° and tapped ten times, 
returned to the horizontal and then tilted and tap ped a further ten times. The method of compaction shall be 
reported.  
7.2.2.2 Skin off the excess mortar with a palette knife, leaving the mortar surface plane and level with the 
top of the mould. Then store the mould  as described in 7. 3.   
©RSB 2021  - All rights reserved                  4 
 7.2.3  Mortars based on air -lime, and air -lime/cement mortars with cement mass not exceeding 50 % 
of the total binder mass  
7.1.3.1  Place the assembled mould frame, clamped together at right angles, on a glass plate on which two 
layers of dry white cotton gauze have been placed. Fill the mould with mortar in two approximately equal layers, 
each layer bein g compacted by 25 strokes of the tamper. Alternatively the mould may be tilted through 
approximately 30° and tapped ten times, returned to the horizontal and then tilted and tapped a further ten times. 
The method of compaction shall be reported.  
7.1.3.2  Skim of the excess mortar with a palette knife leaving the mortar surface plane and level with the 
top of the mould.  
7.1.3.3  Place two layers of white cotton gauze tightly on the mortar surface. Place six layers of absorbent 
filter paper on top of the gauze .  
7.1.3.4  Cover the absorbent filter paper with a glass plate and turn the mould upside down keeping the 
glass plates at the bottom and top firmly attached to the mould.  
7.1.3.5  Carefully remove the glass plate from the top of the inverted mould, place s ix layers of absorbent 
filter paper on the exposed gauze and re -cover with the glass plate on top.  
7.1.3.6  Re-invert the mould back to its upright position and place it on a fixed table and load with mass of 
approximately 5 kg.  
7.1.3.7  After 3 h remove t he load and the glass plate. Discard the absorbent filter paper and the gauze on 
top of the mould, and re -cover with the glass plate on top.  Invert the mould, keeping the non -absorptive plates 
at the bottom and the top firmly attached to the mould. Remove the non -absorptive plate from the top of the  
Inverted mould and discard the absorbent filter paper and the gauze. Then store the mould  as described in 7. 3.  
7.3 Storage and curing conditions  
7.3.1  Mortars with hydraulic binders, and air -lime/cement mortars with mass of air -lime not exceeding 
50 % of the total binder mass.  
Place the mould in a humidity chamber or in sealed polyethylene bags. Then after the period given in Table 1 
remove the specimens from the mould and subsequently store them on a metal grid  under the conditions also 
described in Table 1  
7.3.2  Mortars based on air -lime, and air -lime/cement mortars with cement mass not exceeding 50 % of 
the total binder mass.  
Place the mould in the storage chamber. Then after five days remove the specimens from the mould and 
subsequently store them on a metal grid under the conditions described in Table 2.  
 
 
 DRS  211-5: 2021  
5                ©RSB 2021  - All rights reserved  
 Table 1 — Preparation and conditions of storing specimens for mortars in accordance with 7.3.1  
Type of mortar  Preparation  Storage time at a temperature of 20 °C (+3°C /- 2 °C 
in days  
Relative humidity  
95 % ± 5 % or in polyethylene bag  65 % ± 5 % 
In the mould  With the mould 
removed  With the 
mould 
removed  
Cement and air -lime/cement mortars 
with mass of air-lime not exceeding 
50 % of the total binder mass  7.2.2  1-3 until a total of 7 
days in the 
storage 
chamber or 
polyethylene 
bags  21 
Mortars with other hydraulic binders  7.2.2  1-3 21 
Retarded mortars  7.2.2  7 - 21 
Table 2 — Preparation and conditions of storing specimens for mortars in accordance with 7.3.2  
Type of mortar  Preparation  Storage time at a temperature of 20 °C (+3°C /- 2 °C 
in days  
Relative humidity  
95 % ± 5 % or in polyethylene bag  65 % ± 5 % 
In the mould  With the mould 
removed  With the 
mould 
removed  
Air-lime mortars  7.2.3  5 
 2 21 
Air-lime/cement mortars with cement 
mass not exceeding 50 % of the total  
binder mass  7.2.3  5 2 21 
Additionally, testing can be performed after an extended 90 -day cure under the conditions defined in Table 2 (7 
days at 95 % relative humidity followed by 83 days at 65 % relative humidity). The alternative curing period shall 
be clearly identified.  
8 Determination of flexural strength  
8.1 Apparatus  
8.1.1  A testing machine , capable of ap plying the load at a rate specified in 8.2. The machine shall comply 
with the requirements in Table 3. The machine shall have two steel supporting rollers of length between 45 mm 
and 50 mm and 10 mm + 0.5 mm diameter, spaced 100.0 mm + 0.5 mm apart, and a third steel roller of the 
same length and diameter located centrally between the support rollers (see Figure 1)    
©RSB 2021  - All rights reserved                  6 
 8.1.2  The three vertical planes through the axes of the three rollers shall be parallel and remain parallel, 
equidistant normal to the directi on of the specimen under test. One of the supporting rollers and the loading 
roller shall be capable of tilting slightly to allow a uniform distribution of the load over the width of the specimen 
without subjecting it to any tensional stresses.  
  
Figure 1 — Flexural strength test  
 
where  
1 Load  
l is the distance between the axes of the support rollers, in millimetres (mm)  
DRS  211-5: 2021  
7                ©RSB 2021  - All rights reserved  
 Table 3 — Requirements for testing machines  
Maximum permissible 
repeatability of forces as 
percentage of nominal force  Maximum permissible 
means error of force as  
percentage of nominal  
force  Maximum permissible error of zero 
force as percentage of maximum  
force of range  
±2.0  ±2.0  ± 0.4  
8.2 Procedure  
8.2.1  Preparation  
Test the specimen at 28 days after casting, or more if retarding agents are incorporated in the mortar, unless 
otherwise specified, and immediately after removing from the storage atmosphere. Wipe the bearing surfaces 
of the roller and the sides of specime n with a clean cloth to remove any loose grit or other material. Place the 
specimen with one of its faces (which has been cast against the steel of the mould) on the supporting rollers.  
8.2.2  Loading  
Apply the load without shock at a uniform rate in the range 10 N/s to 50 N/s so that failure occurs within a period 
of 30 s to 90 s.  
NOTE  A loading rate at the lower end of the permitted range may need to be used for the lower strength mortars.  
Record the maximum load applied, in N. Return the broken specimen to the storage chamber and keep it there 
if required, for compressive strength measurements.   
8.3 Calculation and expression of results  
8.3.1  Calculate the flexural strength, f, in N/mm2 using the following equation:  
𝑓=1.5Fl
b𝑑2 
where   
F  is the maximum load applied to the specimen, in Newtons (N) ;  
l is the distance between the support rollers, in millimetres ; 
b is the width of specimen in millimeters (mm) ;  
d is the depth of the specimen in millimeters (mm) .   
©RSB 2021  - All rights reserved                  8 
 8.3.2  b and d may be taken as the internal mould dimensions.  
8.3.3   Record the flexural strength of each specimen to the nearest 0.05 N/mm2. Calculate the mean to the 
nearest 0.1 N/mm2.  
8.3.4  Record age of test specimen and age at demoulding.  
9 Determination of compres sive strength  
9.1 Apparatus  
9.1.1  A testing machine , capable of applying the load at a rate specified in 9.2.2. The machine shall comply 
with the requirements in Table 3. The upper machine platen shall be to align freely as contact is made with the 
specimen , but the platens shall be restrained from tilting with respect to one another during loading.  
9.1.2   Two bearing plates , made of tungsten carbide or of steel of surface hardness at least 600 HV Vickers 
hardness value. The plates shall be 40.0 mm long X 4 0.0 mm ± 0.1 mm wide and 10 mm ±0.1mm thick. The 
dimensional tolerance for the width shall be based on the average of four symmetrically placed measurements. 
The flatness tolerance for the contact faces shall be 0.01 mm.  
9.1.3  Compression jig , used to facilitate the location of the bearing pl ates. The base plate of the jig shall be 
of hardened and tempered tool steel and the faces shall have a flatness tolerance of 0.01 mm. A device to 
provide positive centring on the lower platen of the testing machine shall be provided. Hardened and tempered  
silver steel pillars shall be symmetrically placed about the cantering device so that the gap in one direction is 
the nominal width of the prism plus 0.3 mm and in the other direction is the nominal width of the prism plus 0.8 
mm. The top face of the base  plate shall be marked with an arrow in the direction of the greater distance between 
the pillars to indicate the direction of the long axis of the bearing plates.   
9.2 Procedure  
9.2.1  Preparation  
9.2.1.1  Test the specimen at 28 days after casting, or more if retarding agents are incorporated in the 
mortar, unless otherwise specified, and immediately on removing from the storage atmosphere or after the 
flexural strength test. Remove any loose grit or other material from the sides of the specimen as cast. Wipe t he 
bearing surface of the testing machine, and the bearing plates and jig, with a clean cloth and place the specimen 
in the machine in such a manner that the load is applied to one of its faces (which has been cast against the 
steel of the mould).   
9.2.1.2  Arrange the prism so that the cast en d is 16 mm ± 0.1 mm from the nearer edge of the platens or 
bearing plates. Discard any specimens that do not provide a cube of solid material between the top and bottom 
platens or bearing plates. Carefully align the sp ecimen so that the load is being applied to the whole width of 
the faces in contact with the platens. When using the bearing plates and jig, place one bearing plate on the 
upper surface of the jig with its long axis parallel to the indicating arrow, ensuri ng that it makes close contact 
over the whole surface.   
9.2.1.3  Place the specimen in the jig, between the pillars, with its long axis perpendicular to the arrow and 
place the other bearing plate on top of the specimen parallel to the lower bearing plate.  Carefully centre the 
compression jig assembly on the lower platen of the test machine.   DRS  211-5: 2021  
9                ©RSB 2021  - All rights reserved  
 9.2.2  Loading  
9.2.2.1  Apply the load without shock and increase it continuously until failure occurs. As a guide suggested 
loading rates are given for the different classes  of masonry and rendering mortars in Annex B.  
9.2.2.2  Record the maximum load applied, in N, during the test.  
9.3 Calculation and expression of results  
9.3.1  Calculate the strength as the maximum load carried by the specimen divided by its cross -sectional  area 
of the bearing plate (nominally 1600 mm2).  
9.3.2  Record the strength of each specimen to the nearest 0.05 N/mm2; calculate the mean to the nearest  
0.1 N/mm2.  
9.3.3  Record the age of specimens and the age at demoulding.  
9.4 Test report  
The test rep ort shall include the following information:  
a) the place, date and time of taking the bulk test sample;  
b) the method used for taking the bulk test sample (if known) and the name of the organization that took it;  
c) the type, origin and designation of the mortar by reference to the relevant standard;  
d) the date of testing;  
e) preparation (mixing, casting) and storage (curing) conditions;  
f) the date and time of preparing samples for test (i.e.  date and time of any mixing, casting, demoulding, or 
demoulding procedure, if appropriate);  
g) the flow value of the test mortar determined in accordance with DRS 211-3;  
h) age of mortar when tested;  
i) test results (individual values of flexural strength, if r equired, and of the compressive strength of mortar 
stated to the nearest 0.05 N/mm2, and corresponding mean value stated to the nearest 0.1 N/mm2;  
j) j) remarks, if any.  
NOTE  The is the sample taken from the bulk supply that is to be used for all of the te sts in RS 211  
 
  
©RSB 2021  - All rights reserved                  10 
 Annex  A 
(normative)  
 
Description of metal moulds for specimen preparation  
A.1 General  
A.1.1  The compartment walls are at least 8mm thick and rigid enough to prevent distortion or damage to 
specimens on removal.  
A.1.2  The assembled mould frame is fi rmly attached to a rigid base plate by means of a fixing screw 
arrangement thus giving a water -resistant joint when greased (see 7. 2.2), or it may be held together at right 
angles by means of a clamp and firmly placed on a loose glass plate thus forming th e bottom of the mould (see 
7.2.3).  
A.1.3  A typical mould design for prism specimens is shown in Figure 1  
A.1.4  The assembled moulds conform to the following requirements:  
a) Dimensions : For each compartment, the internal dimensions are: length 160mm ±1mm ; depth 
40mm ±0.1mm and width 40mm ±0.2mm.  .  
b) flatness : the surface of each internal face lies between two parallel planes 0.03 mm apart. The joints 
between the sections of the mould and between the bottom surface of the mould and the top surface of the 
base plate shall lie between two parallel planes 0.06 mm  apart.  
c) squareness : the surface of each internal face lies between two parallel planes 0.50 apart, which are 
perpendicular to the bottom surface of the mould and also to the adjacent internal faces.  
d) parallelism : the top surface of the mould lies between two parallel planes 1.0 mm apart and is parallel to 
the bottom surface.  
e) surface texture : the surface texture of each internal surface shall be not greater than 3.2 mm R a.  DRS  211-5: 2021  
11                ©RSB 2021  - All rights reserved  
    
Figure A.1 — Mould for forming test specimens  
 
 
 
 
 
 
 
©RSB 2021  - All rights reserved                  12 
 Annex  B 
(normative)  
 
Suggested lo ading rates for different classes of masonry and rendering 
mortars  
Suggested loading rates for different classes of masonry and rendering mortars, in N/s, are given in Table B.1.  
Table B.1 — Suggested loading rates   
 Masonry mortars   Rendering mortars  
Category  Compressive strength 
(N/mm2)  Loading rate 
(N/s)  Category  
  Loading rate (N/s)  
M20  20  400  CS I  400  
M 15  15  400  CS II  200  
M 10  10  400  CS III  100  
M 5  5  200  CS IV  50  
M 2.5  2.5  100  -  -  
M 1  1  50  -  -  
 DRS 211-5: 2021  
 
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