ICS 91.100.10  
 
Reference number  
DRS 144: 2020  
© RSB 2020  
  
 RWANDA 
STANDARD  DRS  
144  
 
Second edition  
2020 -mm-dd 
Concrete  building blocks and bricks  — 
Specification  
 
 DRS 144: 2020  
©RSB 2020  - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. User s shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB 2020  
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, includ ing 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 144: 2020  
iii                ©RSB 2020  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ............................  iv 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Materials and Manufacture  ................................ ................................ ................................ ...................  5 
4.1 Materials  ................................ ................................ ................................ ................................ .................  5 
4.1.5  Additives or Admixtures  ................................ ................................ ................................ ......................  5 
5 Requirements  ................................ ................................ ................................ ................................ .........  6 
5.1 Shape, appearance and colour  ................................ ................................ ................................ ............  6 
5.1.1  Shape  ................................ ................................ ................................ ................................ ......................  6 
5.1.2  Appearance and texture ................................ ................................ ................................ ........................  6 
5.1.3  Colour  ................................ ................................ ................................ ................................ .....................  6 
5.1.4  Surface Texture  ................................ ................................ ................................ ................................ ..... 7 
5.2 Dimensions and permissible variations ................................ ................................ ..............................  7 
5.3 Physical requirements  ................................ ................................ ................................ ..........................  8 
6 Methods of Sampling and Testing  ................................ ................................ ................................ ....... 9 
7 Compliance  ................................ ................................ ................................ ................................ ............  9 
8 Marking  ................................ ................................ ................................ ................................ .................  10 
Annex  A ................................ ................................ ................................ ................................ .............................  12 
A.1 Apparatus  ................................ ................................ ................................ ................................ .............  12 
A.2 Preparation of test specimens  ................................ ................................ ................................ ...........  12 
A.3 Procedure  ................................ ................................ ................................ ................................ .............  12 
 DRS 144: 2020  
©RSB 2020  - All rights reserved                  iv 
 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.  
DRS 144 was prepared by Technical Committee RSB/TC 9, Civil engineering and building materials . 
In the preparation of this standard, reference was made to the following standard s: 
1) ASTM C55: Standard Specification for Concrete Building Brick  
2) BS771 -3: Specification for Masonry units - Part 3: Aggregate concrete masonry units (dense and 
lightwight aggregates)  
3) SANS 1215, Concrete masonry units  
The assistance de rived from the above source is hereby acknowledged with thanks.  
This second edition  cancels and replaces the first edition (RS  144: 2012 ), Sub -clause 5.3.2, Table 2, w hich 
have  been technically revised.  
Committee membership  
The following organizations were represented on the Technical Committee on Civil engineering and building 
Materials  (RSB/TC 9) in the preparation of this standard.  
City of Kigali  
Green Effect Engineering  
Integrated Polytechnic Regional Centre –Kigali (IPRC)  
TECOS Ltd  
NPD  
REAL Contractors Ltd  
Rwanda Housing Authority (RHA)  DRS 144: 2020  
v                ©RSB 2020  - All rights reserved  
 Rwanda Transport Development Agency (RTDA)  
Gasabo 3D  
BJ Construction Ltd  
Masss Design Group - Rwanda  
Institut d’ Enseignement Supérieur ( INES - Ruhengeri ) 
NPD Ltd  
EAG Industries Ltd  
Institution of Engineers Rwanda  
CIMERWA Ltd  
University of Rwanda – College of Science and Technology (UR -CST)  
Rwanda  Standards Board  (RSB) – Secretariat  
 DRS 144: 2020  
1                ©RSB 2020  - All rights reserved  
 Concrete building blocks and bricks  — Specification  
1 Scope   
This Draft Rwanda S tandard  specifies  precast solid and precast hollow concrete masonry  building blocks and 
bricks for use in  interior and exterior use in constructing structural and non -structural masonry  walling , and 
are made from portland cement, water, and suitable mineral aggregates with or without the inclusion of other 
materials.  
Building block and bricks co vered by this standard are:  
a) Hollow load bearing and non -load bearing cement blocks;  
b) Solid load -bearing cement blocks and bricks.  
This Standard specifies performance requirements related to dimensional accuracy, density, strength, water  
absorption, shrinkag e and moisture movement for hollow blocks and solid cement blocks or bricks.  
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 refe rences, only the edition  cited applies. For undated references, 
the latest edition of the referenced document (including any amendments) applies.  
RS 96,  Methods of testing aggregates  
RS 107 , Building Sands - Specification  
RS EAS 18 -1, Cement - Part 1: Comp osition, specification and conformity criteria for common cement  
ASTM C426  Standard Test Method For Linear Drying Shrinkage Of Concrete Masonry Units  
ASTM  C140/C140M -18a Standard Test Methods for Sampl ing and Testing Concrete Masonry Units and 
Related Units  
3 Terms and definitions   
For the purposes of this document, the following terms and definitions apply.  
3.1 
masonry unit  
preformed component intended for use in masonry construction   
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 3.2 
facing masonry unit 
masonry unit intended for use with one or more faces left visible and which may or may not be exposed  to 
external climatic conditions  
3.3 
exposed masonry unit  
facing masonry unit exposed to external climatic conditions without render or other equivale nt protection  
3.4 
grading  
particle size distribution of the aggregate  
3.5 
segregation  
separation of the different sizes in the aggregate  
3.6 
block  
masonry unit, either hollow or solid, any one of the external dimension of which is greater than the 
correspo nding dimension of a brick  
3.7 
brick  
masonry unit with dimensions that satisfy all of the following conditions:  
- length not exceeding 300 mm  
-  width not exceeding 130 mm  
 - height not exceeding 120 mm  
3.8 
solid block s 
block which has solid material not less than 75  percent o f the total volume of the block calculated from the 
overall  dimensions  DRS 144: 2020  
3                ©RSB 2020  - All rights reserved  
 3.9 
hollow blocks  
unit that  
a) contains at least one large hole or cavity of such size that  the solid material in the unit constitutes 
between 50 % and 75 % of the to tal volume of the u nit calculated from its overall dimensions, or   
b) when used in a wall (or in a leaf of a cavity wall), forms internal cavities that have a total area,  in a 
horizontal plane, of more than 25 % of the horizontal cross -sectional area of the w all (or leaf of a 
cavity wall)  
3.10 
cellular block s 
blocks which contain one or more formed voids which do not fully penetrate the block  
3.11 
block density  
the density calculated by dividing the mass of a block by the overall volume, including holes or ca vities  
3.12 
drying shrinkage  
difference between the length of specimen which has been immersed in water and then subsequently dried to 
constant length, all under specified conditions; expressed as a percentage of the dry length of the specimen  
3.13 
face shells  
two outer plates of the hollow block that are connected together by webs  
3.14 
shell  
peripheral solid material between the hole(s) and the face or the header of a hollow block  
3.15 
gross area  
total area occupied by a block on its bedding  face, includ ing areas of the cavities   
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 3.16 
hollow ( open or closed cavity) block  
block having one or more large holes or cavities which either pass through the block (open cavity) or do not 
effectively pass through the block (closed cavity) and having the solid materi al between 50 and 75 percent of 
the total volume of the block calculated from the overall dimensions  
3.17 
moisture movement  
difference between the length of the specimen when dried to constant length and when subsequently  
immersed in water, all under speci fied conditions, expressed as a percentage of the dry length of the 
specimen  
3.18 
solid block  
block which has solid material not less than 75 percent of the total volume of the block calculated from the 
overall  dimensions  
3.19 
webs  
solid sections of the ho llow blocks which connect the face shells  
3.20 
nominal dimension  
dimension includ ing the thickness of the  mortar joint  
3.21 
curing  
process of maintaining a satisfactory moisture content and a favourable temperature in the blocks to ensure 
hydration of the cement and development of optimum strength  
3.22 
Face Unit Aesthetic  (FUA) 
unit especially made for its aesthetic effect deriving from non -uniformity of the surface of the  intended exposed 
face(s)  
 DRS 144: 2020  
5                ©RSB 2020  - All rights reserved  
 4 Materials and manufacture  
4.1 Materials  
4.1.1 Cementitious m aterials shall conform to RS EAS 18 -1.  
4.1.2 Course Aggregates shall conform to RS ISO 19595 except that grading requirements shall not 
necessarily apply.  Finer aggregates shall conform to the requirements given in RS 107  
4.1.3  Potable water should be used  in the manufacture of the  blocks and bricks  and comply with the 
requirements of RS EAS  12. 
4.1.4 Other Constituents —Air-entraining agents, colo uring pigments, integral water repellents, finely 
ground silica, and other constituents shall be previously establ ished as suitable for use in concrete masonry 
units and shall conform to applicable Rwanda Standard or shall be shown by test or experience not to be 
detrimental to the durability of the concrete masonry units or any material customarily used in masonry 
construction.  
4.1.5  Additives or admixtures   
Additives or admixtures may be added either as additives to the cement during manufacture, or as admixtures 
to mix. Additives or admixtures used in the manufacture of blocks and bricks  may be:  
a) a
ccelerating, water -reducing and air -entraining admixtures  such as Fly  ash 
b) w
aterproofing agents  
c) c
olouring pigments  
4.2 Manufacture  
4.2.1  materials should be protected from deterioration or contamination until used  methods of storing, 
handling and batching should ensure minim um segregation of the  aggregates  all materials  shall be batched to 
acceptable  degrees of accuracy . 
4.2.2  The water:  cement ratio should be 0.4 for dry materials. In the other case, the quantity of water to be 
added into the mix shall depend on the moisture  content of cement and aggregates until the consistency is 
reached.  
4.2.3  Mixing shall be carried out manually or mechanically  
4.2.4  Placing and compaction shall be done properly such that no voids or honeycombs shall appear after 
the mould is removed.  
4.2.5 The wet mix should not be allowed to stand for more than half an hour to avoid the loss of strength of 
the final products when working in hot weather.   
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4.2.6 Curing  
4.2.6.1  Blocks and bricks shall be cured to ensure that sufficient moisture is availabl e and that the 
temperature is suitable for the chemical reaction (hydration) between cement and water to occur.  Curing 
should be cured in one of the following ways:  
− immersing in water  
− spraying continuously with water  
− wetting the products and wrapping or co vering with a plastic sheet  
4.2.6.2  Curing should be continued for at least 7 days in normal weather (20 °C to 25 °C).  
5 Requirements  
5.1 Shape, appearance and colour  
5.1.1  Shape  
All units shall be solid or hollow, shall be of nominally rectangular shape and true to  the appropriate 
acceptable pattern, and may in the case of solid units be manufactured with or without frogs. They shall be 
acceptably free from visible defects that could interfere with the proper laying of the units or impair the 
strength or the stabili ty (or both) of a construction.  
5.1.2  Appearance  and texture  
5.1.2.1  The surface(s) of face units used for exposed work shall be acceptably uniform in colour and texture 
(see 3.2), and acceptably free from chips, cracks and other imperfections, except that if no t more than 5 % of 
the units of a sample of a consignment contain slight cracks or small chips not larger than 10 mm, this shall 
not be deemed to be grounds for rejection.  
5.1.2.2  When the surface of facing units are declared by the manufacturer to be plan e, they shall not  deviate 
from a plane by more than ( 0 .1√ ld ) mm or 2 mm whichever is the greater , where ld is the length  of the 
diagonal of the surface of the unit declared plane, based on the actual size of the unit.  The requirements for 
flatness shall not apply to the surfaces of units which are manufactur ed to be non -planar.  
Blocks or bricks should  be given a variety of surface textures ranging from a very fine close texture to a 
coarse open texture by the proper selection, grading, and proportioning of aggrega tes at the time of 
manufacture.  
5.1.3  Colour  
When f ace units are required to have coloured surfaces the colour shall be as agreed upon between the 
manufacturer and the purchaser and the manufacturer shall supply to the purchaser for his retention three 
units of the agreed colour to serve as an example of t he possible range of such colour.  DRS 144: 2020  
7                ©RSB 2020  - All rights reserved  
 5.1.4  Surface Texture  
The surface characteristics of units intended for use with plaster or other types of surface finish shall be such 
that the surface will provide adequate adhesion for the plaster or other finish.  
5.2 Dimensions  and permissible variations  
5.2.1  No overall dimension (width, height, and length) shall differ by more than 3.2 mm from the specified 
standard dimensions . 
NOTE  Standard dimensions of concrete building brick are the manufacturer’s designated dimensions. Nom inal 
dimensions of modular size concrete building brick are equal to the standard dimensions plus the thickness of one mortar 
joint. Nominal dimensions of non -modular size concrete building brick usually exceed the standard dimensions by 3.2 to 
6.4 mm . 
5.2.2 Coring : Unless otherwise specified, brick shall be either solid or cored at the option of the seller. For 
cored concrete building brick, the net cross -sectional area in any plane parallel to the surface containing the 
cores shall be at least 75 % of the  gross cross -sectional area measure in the same plane. No part of any hole 
shall be less than 19.1 mm  from any edge of the unit.  
5.2.3  The work size of a unit, as indicated by the overall length L, overall width W and overall height H, 
shall be as stated b y the manufacturer and, when determined in accordance with 5.3, shall not differ from the 
stated nominal values by more than the applicable tolerance given in column 2 of table 1.  
Table 1 — Tolerances on work sizes  
1 2 
Overall Size  Tolerances  
mm 
Length  +2 
-4 
Width  + 3* 
Height  + 3 
* NOTE  In the case of FUA units, the tolerance  
on the overall width shall be + 10 mm.  
5.2.4  Shell and web thicknesses (hollow units)  
The shell thickness and, when applicable, the transverse web thick ness of the unit, determ ined in accordance 
with ASTM C140  shall be at least one -sixth of the overall width of the unit  or 25 mm, whichever is the greater.  
Nominal block  
width   
 Face shell  
thickness   
 Thickness of  
web  
100 or less  
  
 25  25 
     
Over 100 to 150   25  25  
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 Over 1 50 to 200   30  25 
Over 200   35  30 
 
5.2.5  Squareness  
In the case of units of overall height exceeding 90 mm, a ny out -of-squareness of a unit, determined in 
accordance ASTM C140  shall not exceed 2 mm.  
5.3 Physical requirements  
5.3.1 General  
At the time of del ivery to the purchaser, units shall conform to the physical requirements prescribed in Table 2. 
All units shall be sound and free of cracks or other defects that interfere with the proper placement of the units 
or significantly impair the strength or perma nence of the construction. Minor cracks incidental to the usual 
method of manufacture or minor chipping resulting from customary methods of handling in shipment and 
delivery are not grounds for rejection.  
5.3.2 Compressive strength  
5.3.2. 1 When higher comp ressive strengths than those listed in Table 2  are specified, the tested average net 
area compressive strength of three units shall equal or exceed the specified compressive strength, and the 
following single unit strength requirements shall apply.  
5.3.2.2  The nominal compressive strength of units shall be one of the values given in column 1 of Table 2. 
The average and individual compressive strengths of units, determined in accordance with ASTM C140 , shall 
comply with the appropriate values given in Table 2. 
Table 2 — Compressive strength  
Type of Blocks  Grades  Density of 
blocks  
Kg/m3 Nominal compressive 
strength  
Mpa Compressive strength  
Mpa, min  
 
 Average for 5* 
units  individual 
units  
Hollow load 
bearing unit  A (3,5) 
 
> 1 500  3,5 4,0 3,0 
A (4,5)  4,5 5,0 4,0 
A (7,0) 7,0 8,0 5,5 
Hollow non -load 
bearing unit  B(2,5) 2,5 3,5 2,0 
B(3,0)  3,0 3.5 2.5 
Solid load bearing 
unit C (7)  
> 1 800  7,0 8,0 5,5 
C (14)  14,0 15,5 11,0 
        C (21)  21,0 23,5 17,0 DRS 144: 2020  
9                ©RSB 2020  - All rights reserved  
  * In the case of units having an overall  length of 290 mm or less, an average for 
12 units is taken  
 
Note: Classes C 14 and C21 a re used in structural retaining  
Drying shrinkage  
At the time of delivery to the purchaser, the average total linear drying shrinkage of the three units tested shall 
not exceed 0.065 % when tested in accordance with  ASTM C426.  
Soundness  
When units manufactured from slag or clinker or burnt clay brick aggregates are tested in  accordance with 
Annex 1 , the following surface pop -outs shall be allowed:  
a) A maximum of two pop -outs of mean diameter 2  mm - 5 mm in each of only two of the six units  tested 
and  none in the remaining four; or  
b) a maximum of two pop -outs of mean diameter 5  mm - 10 mm in only one of the six units tested and  none 
in  the remaining five.  None of the six u nits shall have pop -outs of mean diameter exceeding 10 mm.  
6 Methods of sampling and testing  
6.1 The purchaser or authorized representative shall be accorded proper facilities to inspect and sample the 
concrete  building brick at the place of manufacture from  the lots ready for delivery.  
6.2 Compressive strength, absorption, density, and dimensional tolerances shall be based on tests of 
concrete building brick of any configuration or dimensions made with the same materials, concrete mix design, 
manufacturing p rocess, and curing method, conducted in accordance with Test Methods ASTM C140  and not 
more than 12 months prior to delivery.  
6.3 Total linear drying shrinkage shall be based on tests of concrete building brick of any configuration or 
dimensions made with the same materials, concrete mix design, manufacturing process, and curing method, 
conducted in accordance with Test Method ASTM C426  and not more than 24 months prior to delivery.  
7 Compliance  
7.1 If a sample fails to conform to the specified requirements, the manufacturer shall be permitted to remove 
units from the shipment. A new sample shall be selected by the purchaser from remaining units from the 
shipment with a similar configuration and dimension and tested at the expense of the manufacturer. If the 
second sample meets the specified requirements, the remaining portion of the shipment represented by the 
sample meets the specified requirements. If the second sample fails to meet the specified requirements, the 
remaining portion of the shipment represente d by the sample fails to meet the specified requirements.  
NOTEUnless otherwise specified in the purchase order, the costs of tests is typically borne as follows: ( 1) if the results of 
the tests show that the units do not conform to the requirements of this  specification, the cost is typically borne by the 
seller; ( 2) if the results of the tests show that the units conform to the specification requirements, the cost is typically borne 
by the purchaser.   
©RSB 2020  - All rights reserved                  10 
 7.2 The lot shall be considered as conforming to the req uirements of the specification if the conditions 
mentioned in this clause  are satisfied.  
7.3 The number of blocks with dimensions outside the tolerance limit and/or with visual defects, among those 
inspected shall be not more than two.  
7.4 For block densit y (see Note in Table 2 ) and compressive strength, the mean value determined shall be 
greater than or equal to the minimum limit specified in table 2 . 
7.5 For drying shrinkage and moisture movement, all the test specimens shall satisfy the requirements of the 
test. If one or more specimens fail to satisfy the requirements, the remaining 3 blocks shall be subjected to 
these tests. All these blocks shall satisfy the requirements.  
7.6 For water absorption, the mean value determined shall be equal or less than maximum limit specified in 
Table 2 . 
8 Marking  
Each consignment of units shall be accompanied by a despatch or consignment note in which  the following 
information is given:  
a) The manufacturer's name, trade name, or trade mark;  
b) the date of manufacture or related  batch number;  
c) whether solid or hollow units;  
d) the work size;  
e) the nominal compressive strength (as given in column 1 of table 2) of the units;  
f) the average drying shrinkage;  
g) in the case of face units having a coloured finish, the colour;  and 
h) when relevant, t hat the units contain a slag or clinker or burnt clay brick aggregate.  
 
 
 
 
 DRS 144: 2020  
11                ©RSB 2020  - All rights reserved  
  
 
 
 
 
 
 
 
 
 
  
©RSB 2020  - All rights reserved                  12 
 Annex  A 
(normative)  
 
Soundness test  
A.1 Apparatus  
A.1.1  A pressure vessel capable of maintaining a steam pressure of 100  kPa - 120 kPa, of suitable 
volume  for the size and number o f specimens to be tested, equipped with a pressure release valve that  can 
be set at 100  kPa - 120 kPa, and a safety valve.  
A.1.2  A heating facility , either as a built -in unit or an external source of heat at the base of the  pressure 
vessel.  
NOTE  Domestic p ressure cookers of various types and sizes complying with the above description are readily  
available. It is recommended that , in respect of safety aspects.  
A.2 Preparation of test specimens  
A.2.1  Cut from a stretcher face of each unit (see 5.3) a test specim en of length approximately 200 mm  and 
cross -section at least 70 mm × 25 mm.  
A.2.2  Prepare a "lime paint" consis ting of hydrated lime  with enough water to allow the "lime paint" to be 
brushed onto the  test specimens to obtain a uniform and thin coating.  
A.2.3 Coat the surface of the uncut face (i.e. the intended exposed face) of the specimen (including  
interstices between aggregate particles) with "lime paint", using a brush to apply a thin coating of  uniform 
colour and texture, and allow it to dry.  
NOTE  It is recommended that a "stock" of a lime mixture of the consistency of a stiff putty be kept in airtight  non-
corrodible containers and that, from this mixture, "lime paint" (see (b) above) be prepared just prior to use.  This procedure 
will enhance the plas ticity properties of the lime. Alternatively, commercially available "lime  wash" that contains no water -
repellents may be used.  
A.3 Procedure  
A.3.1  Ensure that the pressure vessel contains enough water (usually about one -third of its capacity)  and 
so place the  specimens on a rack above the water level that all sides of the specimens will  be exposed to 
steam.  
A.3.2  Secure the lid of the vessel, open the release valve and raise the temperature of the water until  
escaping steam from the release valve is evident. S et the release valve at its working pressure  (100 kPa - 120 
kPa) and so raise and so maintain the temperature of the water that steam just  escapes occasionally from the 
release valve. Maintain this pressure for 6 h.  
A.3.3  Shut off the heat and cool the ves sel by allowing cold water to flow over it until ambient  temperature 
is reached, or gradually release the steam pressure by slightly opening the release  valve until atmospheric 
pressure is reached. Open the vessel and remove the specimens for  examination.  
A.4 Examination of test specimens  DRS 144: 2020  
13                ©RSB 2020  - All rights reserved  
 A.4.1  General  - Inspect the coated surface of each specimen for pop -outs.  
A.4.1.1  Surface pop -outs caused by expansion of unsound material typically appear as small  eruptions on 
the surface, with cracks radiating from thei r apexes. When the material from  such an eruption is gently 
removed and any loose material blown off, a crater -like hole will  be evident at the base of which the remnants 
of a nodule of the expansive substance is likely  to be found.  
Alternatively, the expa nsive forces of unsound nodules may be so great that surface  material is pushed off 
completely and the crater thus formed is directly and positively  Identifiable. It is usual that large nodules of 
unsound material bedded fairly deep in the  specimen will ca use the largest craters and can be readily 
identified. On the other hand, if  such nodules are close to the surface of the specimen, the apparent disruption 
of the  surface is less and the crater formed comparatively small.  
A.4.1.2  It is also possible that " blow-holes" are formed on the surface of the specimen under the  skin of 
cement formed during manufacture of units or under the layer of "lime paint" applied  during preparation of the 
specimens. This skin of layer may, owing to the steaming or other  mechani cal handling, either be broken or 
appear to form small eruptions in places. If the  broken layer is carefully brushed off, the underlying hole will be 
almost hemispherical and  smooth of texture. Such holes shall not be construed as pop -outs.  
A.4.2  Evaluatio n - Record the number and size of surface pop -outs as identified in accordance  with (a)(1) 
above, and check for compliance with the requirements of 3.9.  
 
  
©RSB 2020  - All rights reserved                  14 
 Bibliography  
[1] RS EAS 94: 1999 , Burnt clay building blocks  — Specification  
[2] RS EAS 54:1999 , Burnt build ing bricks — Specification  
[3] RS 107: 2018 , Building sand  — Specification  
[4] ISO 19595 :yyyy, Natural Aggregates for concrete  
 
 DRS 144: 2020  
 
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