ICS 91.100 .10 
 
Reference number  
RS nnn-n: yyyy 
© RSB yyyy 
  
 RWANDA 
STANDARD  DRS 
426-2  
 
1st edition  
yyyy-mm-dd 
 
Masonry Cement  — 
Part 2 : Test methods  
 
 DRS 426-2: 2020 
©RSB yyyy - 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 ascerta in that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB yyyy 
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 photocopyin g 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 426-2: 2020 
iii                ©RSB yyyy - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ .............................  v 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 General requireme nts for testing  ................................ ................................ ................................ .........  1 
3.1.1  Laboratory  ................................ ................................ ................................ ................................ ..............  1 
3.2 Manufacturing tolerances for test equipment  ................................ ................................ ....................  1 
3.2.1  Dimensions  ................................ ................................ ................................ ................................ ............  1 
3.2.2  Mass  ................................ ................................ ................................ ................................ ........................  2 
3.3 Tolerances for test equipment in use  ................................ ................................ ................................ .. 2 
3.4 Number of tests  ................................ ................................ ................................ ................................ ..... 2 
4 Determination of setting time  ................................ ................................ ................................ ...............  2 
4.1 General  ................................ ................................ ................................ ................................ ...................  2 
4.2 Method A  ................................ ................................ ................................ ................................ ................  2 
4.3 Method B  ................................ ................................ ................................ ................................ ................  2 
4.3.1  Test Principle  ................................ ................................ ................................ ................................ .........  2 
4.3.2  Initial setting time procedure  ................................ ................................ ................................ ...............  2 
4.3.3  Report - Initial setting time  ................................ ................................ ................................ ...................  3 
4.3.4  Final setting time procedure  ................................ ................................ ................................ ................  3 
4.3.5  Report – final setting time  ................................ ................................ ................................ ....................  3 
5 Preparation of standard mortar  ................................ ................................ ................................ ...........  3 
5.1 principl e ................................ ................................ ................................ ................................ ..................  3 
5.2 Consistence of fresh mortar by plunger apparatus (reference method)  ................................ .........  3 
5.2.1  Apparatus  ................................ ................................ ................................ ................................ ...............  3 
5.2.2  Procedure  ................................ ................................ ................................ ................................ ...............  4 
5.2.3  Reproducibility  ................................ ................................ ................................ ................................ ...... 4 
5.3 Consistence of fresh mortar by flow table (alternative metho d) ................................ ......................  4 
5.3.1  Method  ................................ ................................ ................................ ................................ ....................  4 
5.3.2  Apparatus  ................................ ................................ ................................ ................................ ...............  4 
5.3.3  Calibration  ................................ ................................ ................................ ................................ ..............  4 
5.3.4  Procedure  ................................ ................................ ................................ ................................ ...............  5 
6 Determination of water retention  ................................ ................................ ................................ .........  5 
6.1 Principle  ................................ ................................ ................................ ................................ .................  5 
6.2 Preparation  ................................ ................................ ................................ ................................ .............  5 
6.3 Apparatus  ................................ ................................ ................................ ................................ ...............  7 
6.4 Procedure  ................................ ................................ ................................ ................................ ...............  8 
6.5 Repeatability and reproducibility  ................................ ................................ ................................ .........  9 
7 Determination of Air content  ................................ ................................ ................................ ................  9 
7.1 General  ................................ ................................ ................................ ................................ ...................  9 
7.2 Pressure method (reference method)  ................................ ................................ ................................ . 9 
7.2.1  Principle  ................................ ................................ ................................ ................................ .................  9 
7.2.2  Apparatus  ................................ ................................ ................................ ................................ ...............  9 
7.2.3  Calibration  ................................ ................................ ................................ ................................ ..............  9 
7.2.4  Procedure  ................................ ................................ ................................ ................................ .............  10 
7.2.5  Repeatability and reproducibilit y ................................ ................................ ................................ ....... 10 
7.3 Alcohol method (alternative method)  ................................ ................................ ................................  11 
7.3.1  Principle  ................................ ................................ ................................ ................................ ...............  11 
7.3.2 Apparatus  ................................ ................................ ................................ ................................ .............  11 DRS 426-2: 2020 
©RSB yyyy - All rights reserved                  iv 
 7.3.3  Procedure  ................................ ................................ ................................ ................................ ............  11 
 DRS 426-2: 2020 
v                ©RSB yyyy - All rights reserved  
 Foreword   
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda 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 ratified  by me mbers of RSB Board of Director s for publication and 
gazettment as Rwanda Standards.  
RS nnn-n was prepared by Technical Committee RSB/TC 09, Civil Engineering and Building Materials  
In the preparation of this  standard, reference was made to the following standard  : 
1) BS EN 413 -2: 2005 Masonry cement — Part 2: Test methods  
The assistance de rived from the above source is hereby acknowledged with thanks.  
RS nnn consists of the following parts, under the general tit le Masonry Cement  — 
Part 1: Composition, specifications and  Conformity criteria  
Part 2: Test methods  
Committee membership  
The following organizations were represented on the Technical Committee on Civil Engineering and Building 
Materials  (RSB/TC 09) in th e preparation of this standard.  
City of Kigali  
Green Effect Engineering  
Integrated Polytechnic Regional Centre –Kigali (IPRC)  
NPD  
REAL Contractors Ltd  
Rwanda Housing Authority (RHA)  
Rwanda Transport Development Agency (RTDA)  DRS 426-2: 2020 
©RSB yyyy - All rights reserved                  vi 
 Standard For Sustainability (SF S) 
TEMACO Builders  
Gasabo 3D  
Masss Design Group - Rwanda  
Institut d’ Enseignement Supérieur ( INES - Ruhengeri ) 
Amajyambere Industry Co Ltd  
NPD Ltd  
Rabbit Construction Ltd  
Institution of Engineers Rwanda  
CIMERWA Ltd  
University of Rwanda – College of Science and Technology (UR -CST)  
Rwanda Standards Board (RSB) – Secretariat  DRS 426-2: 2020 
vii                ©RSB yyyy - All rights reserved  
 Introduction   
This Draft  Standard includes additional test methods to those described in RS EAS 148  Methods of  testing 
cement that enable the performance of masonry cement to be assessed w hen used in mortar  for bedding 
masonry units and for rendering and plastering.  
 
 DRS 426-2: 2020 
1                ©RSB yyyy - All rights reserved  
 Masonry Cement  — Part 2 : Test methods  
1 Scope   
This Draft  Rwanda Standard describes reference and alternative test methods to be used when testing 
masonry cements to assess th eir conformity to DRS 426 -1 (under development)  It gives the tests on fresh 
mortar for  consistence, water retention and air content.  
2 Normative references   
The following documents are referred to in the text in such a way that some or all of  their content c onstitutes 
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.  
RS EAS 148 -1, Cement — Test methods — Part 1: Determin ation of strength   
EAS 73 -2: Building limes (quicklime and hydrated lime) — Test methods  
RS EAS 18 -2, Cement — Part 2: Conformity evaluation  
RS EAS 148 -1, Cement — Test methods — Part 1: Determination of strength  
RS ISO  2768 -1: General tolerances  — Part 1: Tolerances for linear and angular dimensions without individual 
tolerance indications  
3 General requirements for testing   
3.1.1  Laboratory  
Unless specifically stated to the contrary, all the tests described in this document shall be carried out in a 
laboratory  where the air temperature is maintained at (20 ± 2) °C and the relative humidity at not less than 50 
%. 
3.2 Manufacturing tolerances for test equipment  
3.2.1  Dimensions  
Figures indicating the specified requirements for apparatus used in the tests described in this document shall 
include essential dimensions for which manufacturing tolerances are given. Unless otherwise stated, tolerance 
class m according to RS ISO  2768 -1 should be applied.  
NOTE All other dimensions are given for guidance.   
©RSB yyyy - All rights reserved                  2 
 3.2.2  Mass  
Specified masses shall  have manufacturing tolerances within ± 1 % of the mass unless otherwise stated.  
3.3 Tolerances for test equipment in use  
Tolerances applying to apparatus, which has been subjected to wear in use shall not exceed twice the  
corresponding manufacturing tolerance  unless alternative requirements are specified.  
3.4 Number of tests  
Where the test is one of a series subject to statistical control, determination of each property by a single test 
shall be the minimum required. Where the test is not part of a series subject to statistical control, two tests 
shall be performed to determine each property.  
4 Determination of setting time  
4.1 General  
The setting time is determined by observing the penetration of a needle into a cement paste of  standard 
consistence until it reaches a sp ecified value.  The setting time is determined in accordance with either method 
A (4.2) or method B (4.3).  Method B is the reference method.  
4.2 Method A  
The setting time is determined in accordance with RS EAS 148 -3. 
NOTE Experience has shown that the method s pecified in RS EAS 148 -3  in which the specimens are tested under water,  
is not suitable for some masonry cements which have low clinker contents.  
4.3 Method B  
4.3.1  Test Principle  
The equipment used and the specimen preparation procedures are as described in EN 19 6-3 but with  the 
additional requirement for a room or a humidity cabinet of adequate size and maintained at (20 ±  1) °C and 
not less than 90 % relative humidity.  
4.3.2  Initial setting time procedure  
Calibrate the Vicat apparatus with the needle, attached in adva nce of the test, by lowering the needle  to rest 
on the base -plate to be used and adjusting the pointer to read zero on the scale. Raise the  needle to the 
stand -by position. Fill a Vicat mould in accordance with 5.2.2 of RS EAS 148 -3 with paste of standard 
consistence mixed  in accordance with 5.2.1 of RS EAS 148 -3.  
Place the filled mould and base -plate in the room or humidity cabinet and after a suitable time,  position the 
mould, base -plate and container under the needle of the Vicat apparatus. Lower the  needle gently until it is in DRS 426-2: 2020 
3                ©RSB yyyy - All rights reserved  
 contact with the paste. Pause in that position for between 1 s and 2 s in  order to avoid initial velocity or forced 
acceleration of the moving parts. Then release the moving parts  quickly and allow the needle to penetrate 
vertica lly into the paste. Read the scale when penetration  has ceased, or 30 s after the release of the needle, 
whichever is the earlier.  
Record the scale reading, which indicates the distance between the end of the needle and the base -plate,  
together with the ti me from zero. Repeat the penetration on the same specimen at conveniently  spaced 
positions, not less than 8 mm from the rim of the mould or 5mm from each other and at least  10 mm from the 
last penetration position, at conveniently spaced intervals of time,  e.g. at 10 min  intervals. Between 
penetrations keep the specimen in a room or humidity cabinet. Clean the Vicat  needle immediately after each 
penetration. Retain the specimen if determination of the final setting  time is to be made.  
4.3.3  Report - Initial setti ng time  
Report the time measured from zero at which the distance between the needle and the base -plate is  (6 ± 3) 
mm as the initial setting time of the cement to the nearest 5 min.  If the initial setting time exceeds 6h 
determine the final setting time.  
4.3.4  Final setting time procedure  
Invert the filled mould and follow the procedure described in 6.3 of RS EAS 148 -3 with the specimen  held in 
the room or humidity cabinet at controlled humidity rather than under water.  
4.3.5  Report – final setting time  
Report the time  measured from zero at which the needle first penetrates only 0,5 mm into the  specimen as the 
final setting time of the cement, to the nearest 15 min.  
5 Preparation of standard mortar  
5.1 principle  
The properties of fresh mortar made with masonry cement are ass essed on standard mortar prepared  in 
accordance with RS EAS 148-1, but with the water content necessary for the standard consistence.  
The consistence is measured using the plunger apparatus (see 5.2) as the reference method to  achieve the 
required value of  penetration.  
A flow table test (see 5.3) is allowed as an alternative to the plunger test but it is important that the  flow table 
spread equivalent to the required value of penetration is established, using the same type  of masonry cement 
as that which is  to be tested.  
5.2 Consistence of fresh mortar by plunger apparatus (reference method)  
5.2.1  Apparatus  
The mixer and ancillary equipment shall be as described in RS EAS 148 -1.  
©RSB yyyy - All rights reserved                  4 
 The plunger apparatus shown in Figure 1 shall conform to the dimensions specified. The sh ape of the base -
plate (1) shall enable the mortar container (8) to be placed centrally below the plunger (7). The plunger shall 
have a hemispherical lower end, be resistant to corrosion and not attacked by mortar. The total mass of the 
rod (6) and plunger (7) shall be (90 ± 2) g. A release mechanism (5) holds the measuring rod in its initial 
position so that the lower end of the plunger is (100 ± 0,5) mm above the mortar surface prior to commencing 
the test (the initial position in 5.2.2). The tamper (see F igure 2) shall consist of a round rod made of 
impermeable material with sheet metal protection and shall weigh (250 ± 15) g.  
5.2.2  Procedure  
Prepare the mortar according to the procedure described in RS EAS 148 -1 except that the water content shall 
be that deter mined to give the consistence required. Before the start of each test wipe the plunger with a 
damp cloth. Fill the container in two layers immediately after completing the mixing procedure. Compact each 
layer with 10 light strokes of the tamper.  
Strike off  the excess mortar, within 1 min of completion of mixing, by a gentle sawing action using the  
straightedge held at an angle of about 45 degrees. Then at a slightly flatter angle smooth the surface  in a 
single direction in the reverse direction. After placi ng the container on the base -plate, release the  plunger from 
its initial position (150 ± 15) s after the completion of mixing and determine the value of  penetration into the 
mortar by reading the scale.  
A value of penetration of (35 ± 3) mm is required for  the mortar to be of standard consistence. If the  mortar 
does not achieve the standard consistence required then mix a new batch of mortar using a  different quantity 
of water. Repeat the test on new batches of mortar until the value of penetration of  (35 ±  3) mm is obtained in 
two consecutive tests.  Record the mass of water required in grams to obtain standard consistence and the 
value of  penetration in millimetres.  
5.2.3  Reproducibility  
The reproducibility which can be expected, expressed as the standard deviati on of the results of the 
penetration test obtained by different, well -experienced, laboratories is 3,0 mm.  
5.3 Consistence of fresh mortar by flow table (alternative method)  
5.3.1  Method  
NOTE It is anticipated that the test detailed in this clause will be removed at  the next revision of this document, due to the 
increasing availability and use of the plunger apparatus (see 5.2).  
5.3.2  Apparatus  
Flow table, as described in 5.5.2.1.2 of EAS 73 . 
5.3.3  Calibration  
Calibrate the flow table, using the same type of masonry cement as th at to be tested, against the  plunger used 
for the consistence test described in 5.2. Carry out a minimum of three pairs of tests at  different water 
contents in order to establish the spread range on the flow table which is equivalent to  a (35 ± 3) mm value  of 
penetration using the plunger apparatus. Then adopt this spread in order to  achieve the defined level of DRS 426-2: 2020 
5                ©RSB yyyy - All rights reserved  
 consistence required. The relationship be tween the values using the flow table and the plunger apparatus 
shall be established for all products and updated at least once every 12 months.  
NOTE It is recommended to establish a relation in the range 30 -40 mm  
5.3.4  Procedure  
Before the start of each test, ensure that the plate and inner surface of the mould are clean and dry.  If the flow 
table has not been used  during the hour prior to the test, the empty table shall be jolted several times. There 
shall be neither fluid nor dirt between t he bearing (6) and the boss (8) (see Figure 7 of EAS 73-2:) 
In order to determine the flow diameter, place the mould in the ce ntre o f the clean, dry surface of the flow 
table (5.3.2). Fill it with two layers of mortar (prepared just before in accordance with 5.2.2) during  which 
operation the mould with the mounted hopper shall be held firm ly onto the plate with one hand in such a  way 
that its edge coincides with the circle engraved on the plate. Spread each layer of mortar by tamping it lightly 
10 times with the tamper (Figure 2) so that the mould is filled uniformly.  
Remove the hopper without delay, and strike off the excess mort ar, within 1 min of completion of mixing, by a 
gentle sawing action using the straightedge held at an angle of about 45 degrees. Then at a slightly flatter 
angle smooth the surface in a single direction in the reverse direction. Clean the  flow table and re move any 
water in the proximity of the mould. After 10 s to 15 s have elaps ed from the time the mortar has been struck 
off, lift the mould slowly and vertically from the plate (150 ± 15) s  after the completion of mixing. Spread the 
mortar by jolting the pl ate 15 times at one jolt per second.  
Measure the diameter of the pat with a calliper in two directions at right angles to one another. Report  the 
mean value of these measurements to 1 mm as the flow.  
A value of flow corresponding to a plunger penetration o f (35 ± 3) mm is required for the mortar to be  of 
standard consistence. If the mortar does not achieve the standard consistence required then mix a  new batch 
of mortar using a different quantity of water. Repeat the test on new batches of mortar until  the required value 
of flow is obtained.  Record the mass of water required in grams to obtain standard consistence and the value 
of flow in  millimetres.  
6 Determination of water retention  
6.1 Principle  
 The fresh mortar, of standard consistence, is subjected to a suc tion treatment under defined  conditions using 
filter paper as a substrate. The water retention of the mortar is the mass of water  retained in the mortar after 
the suction treatment and is expressed as a percentage by mass of its  original water content.  
6.2 Preparation  
Having completed the consistence test described in 5.2 or 5.3, remix the mortar remaining in the  mixing bowl 
on low speed for 15 s and then carry out the water retention test. Should the time interval  between the 
commencement of mixing and the sta rt of the suction period of the water retention test  exceed 10 min, then a 
fresh batch of mortar shall be prepared.  
  
©RSB yyyy - All rights reserved                  6 
 
Dimensions  and tolerances  in milimetres  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Key 
1) Base -plate  
2) Support  
3) Holder  
4) Guide bushes  
5) Release mechanism  
6) Aluminium measuring rod (scale with 1 mm graduations)  
7) Plunger  
8) Container (with drip protection)  
Figure 1 — Plunger apparatus for measuring consistence  DRS 426-2: 2020 
7                ©RSB yyyy - All rights reserved  
 
 
Dimensions and tolerances in milimetres  
 
 
 
 
 
 
 
 
Figure 2 — Tamper  
6.3 Apparatus  
6.3.1 Rigid mould , of (100 ± 1) mm internal diameter and (25 ± 1) mm internal depth.  
6.3.2 Metal straightedge , as described in RS EAS 148 -1. 
6.3.3 Mass , 2 kg.  
6.3.4 Rigid plate , non -porous (110 ± 5) mm diameter, (5 ± 1) mm thick.  
6.3.5 Cotton gauze or non woven tissue 1) two cir cles (110 ± 1) mm diameter or two squares of (110 ± 1) mm 
 side, of nominal area weight 20 g/m 2 dry gauze or tissue, each piece having a nominal thickness of 0,09 
 mm and nominal permeability to air of 1000 l/m2s. 
6.3.6 Balance , with a capacity of at least  2 kg and capable of weighing to 0,1 g.  
6.3.7 Filter paper , eight circles, (110 ± 1) mm diameter of 180 g/m 2 to 200 g/m 2 dry paper, each circle having a 
 nominal thickness of 0,40 mm and having a nominal particle retention size of 6 µm. Discard all used fi lter 
 papers.  
6.3.8 Palette knife , with a blade 150 mm to 200 mm long and 20 mm to 30 mm wide.   
©RSB yyyy - All rights reserved                  8 
 
6.4 Procedure  
Weigh the empty and dry mould (6.3.1) to the nearest 0,1 g ( u). Weigh the eight circles of unused filter paper 
to the nearest 0,1 g ( v). 
Fill the mould  with the mortar in about 10 increments using the end of the palette knife until the mortar is 
slightly above the edge of the mould. Strike off the excess mortar by a gentle sawing action using the 
straightedge held at an angle of about 45 degrees. Then at  a slightly flatter angle smooth the surface in a 
single direction in the reverse direction.  
Weigh the mould and its contents to the nearest 0,1 g ( w). Cover the surface of the mortar with the two pieces 
of cotton gauze and place the eight circles of filte r paper on top of the gauze. Place the non -porous plate on 
top of the filter papers, invert the mould on to a flat surface and place the 2 kg mass on the inverted base of 
the mould.  
After (300 ± 5) s remove the 2 kg mass, re -invert the assembly, remove the  rigid non -porous plate, filter 
papers and the cotton gauze and weigh the filter papers to the nearest 0,1 g (x).  
Calculate the mass of mortar involved in the test as ( w – u), then the mass of water present ( z), from:  
 
                (1) 
where:  
  u  is the mass of the empty mould, in grams;  
  w  is the mass of the mould and its contents, in grams;  
  y  is the mass of the water used to produce mortar having a penetration of (35 ± 3) mm, in grams.  
The mass of water taken up by the filter papers is given by (x – v). Calculate the water retention as a 
percentage by mass of the total water from:  
 
                         (2) 
  v  is the mass of the eight filter papers before absorption, in grams;  
  x  is the mass of the eight filter papers after absorption, in  grams;  
   z  is the mass of water present in the mortar before absorption, in grams.  DRS 426-2: 2020 
9                ©RSB yyyy - All rights reserved  
 Where the test is not part of a series subject to statistical control and two individual test results differ  by more 
than twice the standard deviation of repeatability (1  %), repeat the test and take the mean of  the two closest 
test results. Report the water retention value, which is expressed to the nearest 1 %.  
6.5 Repeatability and reproducibility  
The standard deviation of repeatability is 1 %.  
The standard deviation of rep roducibility is 2 %.  
These precision data take into account uncertainty of measurement.  
7 Determination of Air content  
7.1 General  
Two methods for determining the air content are included in this document. The pressure method (7.2) is the 
reference method and th e alcohol method is the alternative method (7.3). Other methods may also be used 
provided that prior to use they have been shown to give similar results to the reference method.  
7.2 Pressure method (reference method)  
7.2.1  Principle  
The air content of the fresh mort ar is determined from the reduction in volume when a pressure is applied.  
7.2.2  Apparatus  
The test apparatus (see Figure 3) consists of a metal cylinder (sample container) with a capacity of (0,75 ± 
0,05) l or (1,00 ± 0,05) l 2). The sample container (1) and the cover (2) are sealed airtight together by means of 
clamps (3). The valve (7) is provided to enable filling with water and venting of air. The air is compressed by 
means of a pump (4). The pressure gauge (8) has a scale to measure the air content with divis ions not greater 
than 0,5 %.  
7.2.3  Calibration  
Calibration shall be carried out, in addition to the manufacturer's instructions, in accordance with the following 
procedure:  
 a) Measure and record the total weight of the air content meter on a dry basis.  
 b) Fill  the air content meter 100 % with water, close the valve and take a calibration reading at zero     
      air content.  
 c) Measure and record the total weight of the air content meter as filled in b).   
©RSB yyyy - All rights reserved                  10 
  d) Calculate the difference between c) and a), d. 
 e) Take calibration readings at 5 approximately equally spaced values within an approximate range 
      of 5-25 %  air content using the calculated difference, d. 
The calibration test values obtained shall be used in conjunction with the pressure gauge readin gs to derive a 
relationship that can be used to correct the values when read from the pressure gauge (see 7.2.4).  
7.2.4  Procedure  
Immediately after mixing has been completed, place the mortar into the sample container in two approximately 
equal layers. The final  layer of mortar shall slightly overfill the sample container. To remove air bubbles lightly 
touch each layer using 10 strokes of the tamper (Figure 2), evenly distributed over the surface of the mortar. 
Strike off the mortar level with the top edge of the  container as described in 6.4.  
NOTE: It may be necessary when using the 1,00 l container to increase the size of the batch of mortar.  
Wipe the edge of the container clean with a moist cloth or with a sponge. The air content shall be determined 
between 5 a nd 10 min after the test mortar has been mixed.  
Place the cover (2) onto the container. Seal the cover and the container airtight together by closing the clamps 
(3). 
Allow both the valves (5) and (7) to remain open. Use a squeeze bottle to squirt water int o the valve (7) until 
all air still remaining in the meter has been evacuated through the overflow valve (5) [the water which flows 
out through the valve (5) is to be without air bubbles.  
Operate the air pump until the pressure indicator has reached the in itial prescribed level. Should the pressure 
fall slightly after a few seconds, increase the pressure by pumping again until the pressure indicator has again 
reached the mark. If the indicator goes past the mark then this shall be corrected by partially ope ning 
correction valve (6) until the pressure indicator has returned exactly to the mark.  
Shut both valves (5) and (7). Open the correction valve (6) until the pressure equalization has been achieved. 
Tap lightly on the gauge until the indicator comes to re st and read the air content of the mortar as indicated. 
Correct this reading using the calibration relationship derived in 7.2.3.  
After testing, open both valves (5) and (7) slowly to relieve the pressure in the sample container (1) and then 
repeat the tes t. Where the test is not part of a series subject to statistical control and two individual test results 
differ by more than twice the standard deviation of repeatability (0,5 %), repeat the test and take the mean of 
the two closest test results Report the  air content value, which is expressed to the nearest 0,5 %.  
NOTE: Variations to this procedure may be found between apparatus supplied by different manufacturers. However, the 
manufacturers’ instructions have to be followed to obtain a calibration as requ ired in 7.2.3.  
7.2.5  Repeatability and reproducibility  
The standard deviation of repeatability is 0,5 %.  
The standard deviation of reproducibility is 1,0 %.  DRS 426-2: 2020 
11                ©RSB yyyy - All rights reserved  
 These precision data take into account uncertainty of measurement.  
7.3 Alcohol method (alternative method)  
7.3.1  Principle  
The air content of the mortar is determined from the reduction in volume which occurs when the air is expelled 
by a liquid.  
7.3.2  Apparatus  
 7.3.2.1 Measuring cylinder, approximately 50 mm in diameter, with a capacity of 500 ml and with  5 ml    
      graduations.  
7.3.2.2 Rubber bung, fitting the measuring cylinder.  
7.3.2.3 Funnel, fitting the measuring cylinder and suitable for filling it with mortar.  
7.3.2.4 Mixiture, of 60 % by volume alcohol (ethanol) and 40 % by volume water.  
A sufficient quantity of 2-octanol may be used in place of ethanol.  
7.3.3  Procedure  
Place approximately 200 ml of mortar into the cylinder using the funnel, taking care to avoid cavities in  the 
mortar. Tap the cylinder to level the mortar surface and release entrapped air. Record the mo rtar volume ( Vm) 
to the nearest millilitre. Pour the mixture of alcohol and water carefully into the cylinder  up to the 500 ml mark.  
Seal the cylinder with the rubber bung and invert 20 times to obtain a complete dispersion of the  mortar in the 
alcohol -water mixture. Let the dispersion settle for (5,0 ± 0,5) min and read the resulting  liquid level to the 
nearest millilitre. Repeat this process until two successive readings do not differ by  more than 1 ml. With this 
liquid level (Vv) calculate the air conten t (A) of each mortar sample as a  percentage of the original mortar 
volume from the following formula to the nearest 0,1 %:  
   A = [(500 – Vv)/Vm] 100              (3) 
 where  
  Vm  is the volume of mortar, in millilitres;  
  Vv  is the volume of mortar plus liquid after shaking, in millilitres.  
Calculate the average value of the two individual air contents to the nearest 0,5 %. If the two  individual values 
deviate more than 10 % relatively from their average value, test two additional  samples and calculate a new 
average value. Report the result as the air content to the nearest 0,5 %.   
©RSB yyyy - All rights reserved                  12 
 
 
 
 
 
 
 
 
 
 
Key 
1) Sample container  
2) Cover  
3) Clamp  
4) Pump  
5) Discharge valve  
6) Correction valve  
7) Ball valve  
8) Pressure gauge  
9) Pressure chamber  
 
 
Figure 3 — Schematic diag ram of an air content meter  
 
 
 
 DRS 426-2: 2020 
13                ©RSB yyyy - All rights reserved  
 Bibliography  
[1] EN 197 -1: 2011; Cement – Part 1; Composition, specifications and conformity criteria for common 
cements  
[2] EN 413 -1, Masonry cement — Part 1: Composition, specifications and conformity criteria  
[3] ISO 5725 -2, Accurac y (trueness and precision) of measurement methods and results — Part 2: Basic method 
for the determination of repeatability and reproducibilit y of a standard measurement method  
 DRS 426-1: 2020  
 
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