ICS 91.100.15  
 
Reference number  
DRS 261: 2020  
© RSB 2020  
  
 RWANDA 
STANDARD  DRS  
261  
 
Second edition  
2020 -mm-dd 
) 
Granite tiles and slabs for use in 
Construction — Specification  
 
 DRS 261: 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. Users 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 mecha nical, 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 261: 2020  
iii                ©RSB 2020  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ..........................  vvi 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Classification and type  ................................ ................................ ................................ .........................  4 
5 Physical Properties  ................................ ................................ ................................ ...............................  5 
5.1 General requirements  ................................ ................................ ................................ ...........................  5 
5.2 Sizes ................................ ................................ ................................ ................................ ........................  6 
5.2.1  Granite block  ................................ ................................ ................................ ................................ ..........  6 
5.2.2  Granite slabs  ................................ ................................ ................................ ................................ ........  76 
5.2.3  Granite tiles  ................................ ................................ ................................ ................................ ............  7 
5.2.4  Custom sizes  ................................ ................................ ................................ ................................ .........  7 
5.2.5  Granite surface plates sizes  ................................ ................................ ................................ ...............  87 
5.3 Tolerance  ................................ ................................ ................................ ................................ ..............  98 
6 Finish  ................................ ................................ ................................ ................................ ....................  10 
7 Sampling  ................................ ................................ ................................ ................................ ..............  11 
8 Inspection  ................................ ................................ ................................ ................................ .............  11 
9 Marking  ................................ ................................ ................................ ................................ .................  11 
Annex  A (normative)  Water ab sorption test method  ................................ ................................ ...................  13 
A.1 sampling  ................................ ................................ ................................ ................................ ...............  13 
A.2 Test specimens  ................................ ................................ ................................ ................................ .... 13 
A.3 Proc edure  ................................ ................................ ................................ ................................ .............  13 
A.4 Calculation and Report  ................................ ................................ ................................ .......................  13 
A.5 Report  ................................ ................................ ................................ ................................ ...................  14 
Annex  B (normativ e)  Compressive strength test - Test method  ................................ ................................  15 
B.1 Apparatus  ................................ ................................ ................................ ................................ .............  15 
B.2 Sampling  ................................ ................................ ................................ ................................ ..............  15 
B.3 Test specimens  ................................ ................................ ................................ ................................ .... 15 
B.4 Conditioning  ................................ ................................ ................................ ................................ ........  16 
B.5 Procedure  ................................ ................................ ................................ ................................ .............  16 
B.6 Calculation  ................................ ................................ ................................ ................................ ...........  16 
B.7 Report  ................................ ................................ ................................ ................................ ...................  16 
Annex  C ................................ ................................ ................................ ................................ .............................  18 
Modulus of rupture - test m ethod  ................................ ................................ ................................ ...................  18 
C.1 Apparatus  ................................ ................................ ................................ ................................ .............  18 
C.1.1  Testing machine  ................................ ................................ ................................ ................................ .. 18 
C.1.2  Load Applicat ion and Support Blocks  ................................ ................................ ..............................  18 
C.2 Sampling  ................................ ................................ ................................ ................................ ..............  18 
C.3 Test specimens  ................................ ................................ ................................ ................................ .... 18 
C.4 Marking and measuring specimens  ................................ ................................ ................................ .. 19 
C.5 Conditioning  ................................ ................................ ................................ ................................ ........  20 DRS 261: 2020  
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 C.6 Procedure  ................................ ................................ ................................ ................................ ............  20 
C.7 Calculation  ................................ ................................ ................................ ................................ ...........  20 
C.8 Report  ................................ ................................ ................................ ................................ ..................  20 
Annex  D ................................ ................................ ................................ ................................ ............................  22 
Abrasion resistance - Test method  ................................ ................................ ................................ ................  22 
D.1 Apparatus  ................................ ................................ ................................ ................................ ............  22 
D.2 Sampling  ................................ ................................ ................................ ................................ ..............  22 
D.3 Test specimens  ................................ ................................ ................................ ................................ ... 22 
D.4 Conditioning  ................................ ................................ ................................ ................................ ........  22 
D.5 Procedure  ................................ ................................ ................................ ................................ ............  22 
D.6 Calculation  ................................ ................................ ................................ ................................ ...........  23 
Annex  E ................................ ................................ ................................ ................................ .........................  2524 
Flexural strength - test method  ................................ ................................ ................................ ..................  2524 
E.1 Apparatus  ................................ ................................ ................................ ................................ ........  2524 
E.2 Sampling  ................................ ................................ ................................ ................................ ..........  2524 
E.3 Test specimen  ................................ ................................ ................................ ................................ . 2524 
E.4 Conditioning  ................................ ................................ ................................ ................................ .... 2625 
E.5 Procedure  ................................ ................................ ................................ ................................ ........  2625 
E.6 Calculation  ................................ ................................ ................................ ................................ ....... 2625 
E.7 Report  ................................ ................................ ................................ ................................ ..............  2726 
 DRS 261: 2020  
v                ©RSB 2020  - 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.  
DRS 261 was prepared b y Technical Committee RSB/TC 09, Civil Engineering and Building Materials.  
In the preparation of this standard, reference was made to the following standard s: 
1) SANS 1357:2008 Granite surface plates and tables  
2) ASTM C615/C615M – 11 Standard Specification for Granite Dimension Stone  
The assistance de rived from the above source is hereby acknowledged with thanks.  
This second edition  cancels and replaces the first edition (RS  261: 2014 ), of which have  been technically 
revised.  
Committee membership  
The following o rganizations were represented on the Technical Committee on Civil engineering and building 
materials (RSB/TC 9) in the preparation of this standard.  
Paragraph of p articipants  
University of Rwanda – College of Science and Technology (UR -CST)  
City of Kigali  
Green Effect Engineering  
Integrated Polytechnic Regional Centre –Kigali (IPRC)  
TECOS Ltd  
NPD  
REAL Contractors Ltd  DRS 261: 2020  
©RSB 2020  - All rights reserved                  vi 
 Rwanda Housing Authority (RHA)  
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  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 261: 2020  
1                ©RSB 2020  - All rights reserved  
 Granite Tiles and Slabs for use in construction  — Specification  
1 Scope   
This Draft Rwanda Standard specifies requirements for  granite  dimension stone such as granite  tiles and 
slabs used in flooring , wall facing  or cladding , work tops, skirting  and any other use.  
The granite specified in this standard is natural stone that is sawed, cut, split or otherw ise finished or shaped.  
This standard does not cover  moulded, cast or otherwise artificially aggregated units composed of fragments, 
and also crushed and broken stone  
2 Normative references  
The following documents are referred to in the text in such a way th at 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.  
ASTM C97 / C97M  Stan dard Test Methods for Absorption and Bulk Specific Gravity of Dimension Stone  
ASTM  C170/C170M Standard Test Method for Compressive Strength of Dimension Stone  
ASTM C99 / C99M  Standard Test Method for  Modulus of Rupture of Dimension Stone  
ASTM  C241/C241M Standard Test Method for Abrasion Resistance of Stone Subjected to Foot Traffic  
ASTM C1353 / C1353M Standard Test Method for Abrasion Resistance of Dimension Stone Subjected to 
Foot Traffic Using a Rotary Platform Abraser  
ASTM C880 / C880M Standard Test Method for Flexural Strength of Dimension Stone  
3 Terms and definitions   
For the purposes of this document, the following terms and definitions apply . 
3.1 
granite (commercial definition)  
visibly granular, igneous and metamorphic  rock generally ranging in colo ur from pink to light or dark grey and 
consisting mostly o f quartz and feldspars, accompanied by one or more dark minerals.  The texture is typica lly 
homogeneous , but may be gneissic or porphyritic.  Some dark granular igneous  and metamorphic rocks, 
though not granite proper, are included in the definition   
©RSB 2020  - All rights reserved                  2 
 3.2 
granite (scientific definition)  
visibly granular, crystalline rock with equigranular or i nequigranular texture, normally having an essential 
composition of two feldspars (alkali/feldspar plus sodic plagioclase or two alkali feldspars), quartz, micas, 
hornblende and rarely pyroxene  
3.3 
texture  
modified appearance of natural stone resulting from  one or several mechanical treatments that is determined 
by size, shape and mutual relationships of component grains or crystals  
Textur es related to granites include:  
a)  Equigranular  - grains of approximately the same size.  
b) Inequigranular - grains of m arkedly unequal sizes.  
c) Porphyritic  - A texture defined by relatively large grains (phenocrysts), typically feldspar that are 
distributed in distinctly fine grained matrix.  The phenocrysts of porphyritic granites generally are 
rectangular or partly roun ded in outline and may be as much as several c entimetres in maximum 
dimension  
d)  Foliated - a continuous or discontinuous layer structure in metamorphic rocks formed by the 
segregation or different minerals in streaks or lenticles, or by alternation of ba nds of different textures.  
3.4 
abrasive finish  
flat non -reflective surface finish  
2.5 
honed finish  
honed is a super fine smooth finish, though not as fine as a polished finish  
3.6 
cladding  
non-load-bearing stone used as the facing material in wall constru ction that contains other materials  
3 .7 
crack  
partial break in the stone ( seam)  DRS 261: 2020  
3                ©RSB 2020  - All rights reserved  
 3.8 
polished finish  
the finest and smoothest finish available in stone characterized by a high luster (gloss) and strong reflection of 
incident light, generally only possible on hard, dense materials  
3.9 
sand/blasted finish  
matte -texture surface finish with no gloss, accomplished by exposing the surface to a steady flow of sand 
under pressure  
3.10 
durability  
measure of the ability of dimension stone to endure and to maintain i ts essential and distinctive characteristics  
of strength, resistance to decay, and appearance  
3.11 
pits 
small depressions, voids or pinholes in stone, especially on a finished surface  
3.12 
cut stone  
stone fa bricated to specific dimensions  
3.13 
dimension st one 
natural stone that has been selected and fabrica ted to specific sizes or shapes  
3.14 
slab 
piece of stone  having two parallel  surfaces and produced by shaving or splitting in the first milling or quarrying 
operation  
3.15 
tile 
thin modular stone unit  under 50mm thick   
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 3.16 
lot 
not more than 10 tiles or slabs of the same size, type, and accuracy grade, from one  manufacturer, submitted 
at any one time for inspection and testing  
3.17 
defective  
surface plate that fails in one or more respects to comply with the relevant requirements of the  specification  
3.18 
sound stone  
stone which is free of cracks, fissures, or other physical defects  
3.19 
clamping ledge  
margin of reduced thickness that is used for mounting clamps along an edge of a surface plate  
3.20 
flatne ss tolerance of work surface  
distance separating two parallel planes between which the work surface can be contained  
3.21 
seam  
flaw or crack in a granite plate  
3.22 
stiffness  
resistance of a surface plate to sagging under load  
4 Classification  and type  
4.1 Granite tiles and slabs  occurs in various colours and sha pes depending upon the source . Granite 
dimension stone specified in this standard  shall be  granite used for:  
a)  exterior and interior cladding of buildings and structures;  
b)  curbstone, paving, and landscape features;  DRS 261: 2020  
5                ©RSB 2020  - All rights reserved  
 c)  structural components having established dimensions;  
d)  grade separations and retaining walls; and  
c)  mo numents.  
4.2 Granite surface plates   
Surface plates are usually used for mounting mechanical, electronic, and optical gaging s ystems  
4.2.1  The type of surface plate shall be one of the following, as specified by the purchaser:  
a) Type 1: No clamping ledge.  
b) Type 2: Two clamping ledges, one on each of the longer sides of the rectangular plate, unless  otherwise 
specified by the purchaser.  
c) Type 3: Four clamping ledges.  
4.2.2 The proportions of clamping ledges on surface plates, when relevant, shall be as follows:  
1) Plates less than 160 mm thick :   
  - Depth:     not less than 40 % of plate thickness  
  - Overhang: approximately  25 % of plate thickness  
2) Plates 160 mm thick and over :  
  - Depth: not less than 75 mm  
  - Overhang: not more than 50 mm  
5  Physical Properties  
5.1 General requirements  
5.1.1  Granite supplied under this specification shall conform to the physical requirement s specified  in 
Table 1 . for possible variations from this table.  
5.1.2  Granite shall be sound, durable, and free of spalls, cracks, open seams, pits, or other defects that 
are likely to impair its structural integrity in its intended use.  
5.1.3  Granite sha ll be free of minerals that may cause objectionable staining under normal environments of 
use. 
5.1.4  The desired color and texture, with their permissible natural variations in material characteristics for 
all material to be produced for the project, shall  be established by control samples. Select representative 
samples by viewing a sufficient number of physical samples prior to production that show the complete range 
of variations in color and texture of the granite specified.   
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 Table 1 — Physical requiremen ts 
Physical Property  Test requirements A  Test method(s)  
Absorption by weight, max %  0.4 ASTM C97/C97M  
Density, min, kg/m3  2560  ASTM C97/C97M  
Compressive strength, min, c Mpa  131 ASTM C170/C170M  
Modulus of rupture, min, Mpa  10.3 ASTM C99/C99M  
Abrasion resistance, min, Ha D,E,F  25 ASTM C241/C241M / ASTM C1353  
Flexural strength, min, Mpa  8.3 ASTM C880/C880M  
A The material property values in Table 1 were established using samples  prepared according to the individual test methods,  
Finishes, other  than th ose specified in the individual test methods, may result in a deviation from established  values.     
B The material properties given in Table 1 represent properties of granite that have history of successful use for general build ing and 
structural purposes .  
C The minimum compressive strength, flexural strength, and modulus of rupture shall be based upon the minimum average strength of 
specimens tested in four conditions; wet or dry and parallel or perpendicular to rift.  
D pertains only to stone subject t o foot traffic  
    
E The new abrasive is currently more aggressive, resulting in lower abrasive hardness values (Ha). Therefore, care should be ta ken when 
interpreting Ha values from tests using the new abrasive, particularly with regard to current ASTM s tone standard specification 
requirements for abrasion resistance.  
F Abrasion Resistance test method ASTM C1353 will eventually replace Test Method C241/C241M and it is not necessary to perform 
both tests. Availability of the proper equipment and material s by the testing laboratory may determine which test is performed.  
5.1.5  Stiffness of surface plates  
When tested in accordance with 6.4, a surface plate of size 400 mm × 250 mm or larger shall have a 
thickness or a modulus of elasticity (or both) such th at it is capable of supporting a mass load of 250 kg/m2 of 
work surface area centrally without deflecting by more than one -half of the appropriate flatness tolerance (see 
5.2.5.1.b ), measured along a diagonal at the centre of the plate.  
5.2 Sizes  
5.2.1  Granite block 
Granite blocks shall be supplied in the form of cubes with the following dimensions:  
  a) The length shall be 2.5m to 4m ; 
  b) The width shall be 1m to 2m ;and 
  c) The height shall be 1m to 2m . 
NOTE  Dimensions more than the above mentioned may be produced  as per the customer’s demand and the cutting 
machine in use . DRS 261: 2020  
7                ©RSB 2020  - All rights reserved  
 5.2.2  Granite  slabs  
5.2.2.1 Granite slabs shall be rectangular or square and of specified dimensions. The tolerance in length and 
breadth shall be + 2 mm and thickness + 1 mm. The bottom face may be rough but the top surface shall be 
fine dressed and joint faces shall be dressed back square with the top surface for at least 50 mm, without 
hollowness or spalling off.  
5.2.2.2   The granite slabs shall be supplied in the sizes given below:  
 a) The length shall be 2 000 to 4 000mm   
b) The width shall be 600mm to 1 500mm   
c) The thickness shall be 20  mm to 100 mm  
NOTE  The width of 600  mm to 850  mm can be produced using “cutting disc” with diamond segment. width more than 
850 mm can be produced using gang saw cutting machines.  
5.2.3  Granite  tiles 
The granite tiles shall be supplied in sizes given below:  
a) 600 mm  300 mm;  
b) 600 mm x 600 mm  
c) 500 mm 250 mm;  
d) 400 mm 400 mm;  
e) 300 mm  300 mm;  
f) 200 mm  200 mm; and  
g) 100 mm  100 mm.  
The thickness of tiles shall be 10  mm, 15  mm and  20 mm in the same piece.  
5.2.4  Custom sizes   
Sizes and shapes other than those specified may be supplied as agreed between the supplier and the 
purchaser depending on the design requirements.  However, thickness should not be below 10 mm for tiles 
and 20  mm for slabs.   
©RSB 2020  - All rights reserved                  8 
 5.2.5  Granite surface plates  sizes  
The size of a surface plate shall be one of th ose given in column 1 of table 2 , as specified by the purchaser.  
Table 2  — Size of surface plates  
Size of plate*, i.e. nominal  length+ 
x nominal  width+                       
mm Nominal 
surface area     
mm Approx.  diagonal           
of plate                
mm Thickness of plate                 
min., mm  Nominal mass of 
plate               
 kg 
160 x 100  
250 x 160  
400 x 250  1,6 
4,0 
10,0 188 
296 
471 50 
50 
50 2,4 
5,9 
14,8 
400 x 400  
630 x 400  
630 x 630  16,0 
25,0 
40,0 566 
745 
891 70 
70 
70 33 
52 
82 
100 x 630  
1 000 x 1 000  
1 600 x 1 000  63,0 
100,0  
160,0  1 180  
1 414  
1 880  100 
100 
160 186 
295 
755 
2 000 x 1 000  
2 500 x 1 600  
3 500 x 1 600  200,0  
400,0  
560,0  2 236  
2 960  
3 848  200 
250 
300 1 180  
2 950  
4 956  
*   Plates sizes, except 2 000 mm x 1 000 mm and 3 500 mm x 1 600 mm x 1 600 mm, correspond to the number series R5.                                                                                                                                                     
+  The actual dimensions shall be subject to a tolerance of +2%  , - 0%                                                                 
+  Based on a density of 2 950 kgm3 
5.2.5.1  Side faces  
5.2.5.1.1   Chamfers : All edges and corners shall be chamfered as follows:  
 Table 3 — chamfers for different plate sizes  
Size of plate  chamfer  
160 mm × 100 mm  a2 mm  
250 mm × 160 mm  
400 mm × 250 mm  a3 mm  
630 mm × 400 mm  
> 630 mm × 630 mm  a5 mm  
The corresponding slope lengt hs shall be approximately 3, 4, 
and 7 mm respectively.  
5.2.5.1. 2  The squareness  tolerance of the side faces of a type 1 surface plate relative to the  work surface 
shall be subject to agreement between the purchaser and the manufacturer.  
5.2.6.1  The flatn ess tolerance of the side faces of a type 1 surface plate shall be subject to agreement 
between the purchaser and the manufacturer.  
 DRS 261: 2020  
9                ©RSB 2020  - All rights reserved  
 5.3 Tolerance  
5.6.1 The following tolerance shall be allowed on tiles, slabs and skirtings whether they are standard sizes 
or custom sizes:  
5.6.1.1 Slabs  Tolerance  
  a) Length      2 mm  
  b) Width      2 mm  
  c) Thickness     1 mm  
5.6.1.2 Tiles  Tolerance  
  a) Linear Dimension    1 mm  
  b) Thickness     1 mm  
5.6.1.3 Surface plates tolerance  
Flatness : When a surface plate is tested in accordance with clause 7 , the accuracy grade shall conform to one 
of the grades 00, 0, 1, or 2, as specified by the purchaser. The rounded -off values of the flatness tolerances 
corresponding to these accuracy grades and the various nominal lengths of su rface plates are given in table 
4. 
The values give in Table 4 have been calculated from the following formulae:  
For any accuracy of 00, flatness tolerance = 
  
For any accuracy of 0, flatness tolerance = 
  
For any accuracy of 1, flatness toleran ce =  
  
For any accuracy of 2, flatness tolerance =   
  
 
where L is the nominal length of the surface plate in millimetres.  
  
©RSB 2020  - All rights reserved                  10 
 Table  4 - Flatness tolerances of surface plates  
Length of surface plate  
mm Flatness tolerance for accuracy grades  
µm 
00 0 1 2 
160 2 5 12 23 
250 3 5 13 25 
400 3 6 14 28 
630 3 7 16 33 
1 000  4 8 20 40 
1 600  5 10 26 32 
2 000  6 12 30 60 
2 500  7 14 35 70 
3 500  9 18 45 90 
6 Finish  
6.1 The granite tiles and slabs shall be sound, durable and free of imperfectio ns such as stains, cra cks, pits, 
or other defects that would impair its strength, durability or appearance.  
6.2 The faces of granite slabs and tiles shall be supplied with one of the following finishes:  
  a)     Sand -blasted and/or abrasive finish;  
  b) Honed finish;  
  c) Polis hed finish.  
  d)     Flamed finish  
Note:  granite slabs and tiles will have a one side of the surface polished; other surface finishes like Sand -blasting, honing 
and flaming can be done on demand.  
6.3 The edges of the slabs and tiles shall be true and stra ight, but may be profiled, bull nosed or chamfered  
and can be polished or left unpolished depending on the customer’s requirements . 
6.4 Machine cut tiles and slabs with square edges may be supplied if so specified by the customer/purchaser.  
6.5 When so req uired by the purchaser, a surface plate shall be provided with a properly fitting cover or other 
means of protecting the work surface and the edges when the plate is not in use. The cover may be of 
plywood, well seasoned timber, or a derivative of wood sui tably treated with a varnish or other coating to give 
the desired finish.  DRS 261: 2020  
11                ©RSB 2020  - All rights reserved  
 7 Sampling  and testing  
7.1 Samples, if required, for testing to determine the characteristics and physical properties shall be 
representative of the granite to be used.  
7.2 In any co nsignment, all the slabs, surface plates or tiles of the same group, size and finish shall be 
grouped together to constitute a lot. Samples shall be selected and tested separately for each lot for 
determining its conformity or otherwise to the requirements  of the specification.  
7.3 The number of slabs, surface plates or tiles to be selected for the sample shall depend upon the size of 
the lot and shall be in accordance with table 3. The slabs or tiles in the sample shall be selected at random 
and in order t o ensure the randomness of selection, random number tables may be used.  
Table 4 sample size and criteria for conformity  
Number of slabs, tiles in the lot    (L)  Number of  slabs, or tiles to be selected in sample  Permissible number of 
defectives  
L < 25 3 0 
26 < L < 100 5 0 
101 < L < 200 8 0 
201 < L < 500 13 0 
501 < L < 1000  20 1 
Lot size surface plates  Sample for inspection 
surface plates  Sample for testing 
surface plates   
1 -- 4 All 1 0 
5 -- 10 5 1 0 
7.4 All the slabs , surface plates  or tiles selec ted in the sample shall be examined for dimensions, finish and 
general requirements.  Any slab, surface palate or tile failing in any one or more of the above requirements 
shall be considered as defective.  A lot shall be co nsidered as conforming to these requirements if the number 
of defective obtained is not more than the permissible number of defectives given in column 3 of table 4. 
8 Inspection  
The purchaser/customer or his authorized representative shall , if he so desires , be granted facilities for 
inspection of finished slabs or tiles prior to dispatch from the supplier's works.  
9 Marking  
Each type of granite slabs and tiles should be permanently label led clearly and indelibly with the following  
information : 
a) name of manufacturer or trade mark;  and 
b) the number and size of the tile.   
©RSB 2020  - All rights reserved                  12 
 c) accuracy grade  
d) serial number  
 DRS 261: 2020  
13                ©RSB 2020  - All rights reserved  
 Annex  A 
(normative)  
 
Water absorption test method  
A.1 sampling  
The sample shall be selected to represent a true average of the type or grade of stone under consideration 
and shall be of the quality supplied to the market under the type designation to be tested. The sample may be 
selected by the purchaser or his authorized representative from the quarried stone or taken from the natural 
ledge and shall be of adequate size to permit the preparation of at least five test specimens. When perceptible 
variations occur, the purchaser may select as many samples as are necessary for determining the range in 
properties.  
A.2 Test specimens  
The specimens may be cubes, prisms, cylinders, or any regular form with least  dimension not under 50 mm 
and greatest dimension not over 75 mm but the ratio of volume to surfa ce area shall not be less than 8 nor 
greater than 12 .5. All surfaces shall be reasonably smooth. Saw or core drill surfaces are considered 
satisfactory, but ro ugher surfaces shall be finished with No. 80 abrasive. No chisels or similar tools shall be 
used at any stage of preparing the specimens. At least five specimens from each sample shall be prepared.  
A.3 Procedure  
A.3.1  Dry the specimens for 48 h in a ventilated  oven at a temperature of 60oC ± 2°C. At the 46th, 47th, and 
48th hour, weigh the specimens to ensure that the weight is the same. If the weight continues to drop, continue 
to dry the  specimens until there are three successive hourly readings with the same  weight.  
A.3.2  After drying, cool the specimens in the room for 30 min and weigh. When the specimens cannot be 
weighed immediately after cooling, store them in a desiccator. Determine the weights to the nearest  0.01 g.  
 A.3.3  Immerse the specimens complet ely in filtered or distilled water at 22oC ± 2°C for 48 h. At the end of this 
period remove them from the water bath one at a time, surface  dry with a damp cloth, and weigh to the 
nearest 0 .001g.  
A.4 Calculation and Report  
 Calculate th e weight percentage abso rption for each specimen as follows:  
Absorption, weight % =  
  
                                                                          
where ; 
A = weight of the dried specimen, [g], and   
©RSB 2020  - All rights reserved                  14 
 B = weight of the specimen after immersion, [ g]. 
 Calculate the mean water absorption of the sample as the average of the weight percentage absorption for all 
specimens.  
A.5 Report  
The report shall contain the following information:  
a) Identity of party providing the sample ; 
b) Name of stone ; 
c) Identity of sampl e; 
d) Mean water absorption of sample ; 
e) Any variations to the procedure, including specimen dimensions, given in this standard ; 
f) Weight of dried specimen ; 
g) Weight of soaked and surface -dried specimen in air ; and  
h) Percentage water absorption by weight of specimen.  
 DRS 261: 2020  
15                ©RSB 2020  - All rights reserved  
 Annex  B 
(normative)  
 
Compressive strength test - Test method  
B.1 Apparatus  
In vertical testing machines, the spherical bearing block shall be suspended from the upper head of the 
machine in such a manner that the contact plate remains in a central position (spheric al surfaces in full 
contact) when not loaded. The spherical surfaces shall be well lubricated, and the center of curvature shall lie 
in the surface of contact with the specimen.  
B.2 Sampling  
 The sample shall be selected to represent a true average of the type  or grade of stone under consideration 
and shall be of the quality supplied to the market in finished form under the type designation to be tested. The 
sample may be selected by the purchaser or his authorized representative from quarried stone or taken fr om 
the natural ledge and shall be of adequate size to permit the preparation of the desired number of test 
specimens. When perceptible variations occur, the purchaser may select as many samples as are necessary 
for determining  the variation in compressive strength.  
B.3 Test specimens  
The test specimens may be cubes or cylinders and shall be cut from the sample with saws or core drills. The 
diameter or lateral dimension (distance between opposite vertical faces) shall be not less than 50 mm, and the 
ratio of h eight to diameter or lateral dimension shall be 1:1. At least five specimens shall be prepared for each 
condition of the test; that is, when the compressive strength is desired for the wet and dry conditions but in 
only one direction, such as perpendicular  to the bed (or rift) (see Figure  B1(a)), ten specimens will be 
required. For wet and dry strength tests both perpendicular and parallel to the bed (or rift) (see Fig ure B1(a) 
and ( b)), twenty specimens are required .The load -bearing faces shall be finishe d by grinding to as nearly true 
and parallel planes as practicable.  The load -bearing surfaces and the direction of bedding (or rift) shall be 
marked on each specimen after finishing.  
 
 
 
Perpendicular to bedding or rift                                                          Parallel to bedding or rift  
(a) Loading Perpendicular to Bedding or Rift                                      (b) Loading Parallel to Bedding or Rift  
NOTE  Dashed lines indicate direction of bedding or rift. Arrows indicate direction of  loading.  
Figure B  1 - Methods of applying load with reference to bedding or rift 
 
 
©RSB 2020  - All rights reserved                  16 
 The load -bearing areas of the specimen shall be calculated from measurements taken midway between the 
load bearing surfaces. The dimensions of the specimens shall be measure d to the nearest 0 .5 mm) and the 
load-bearing areas calculated to the nearest 0 .10 mm2. 
B.4 Conditioning  
Before testing the specimens in a dry condition, dry them for 48 h at 60oC ± 2°C. At the 46th, 47th, and 48th h, 
weigh the specimens to ensure that the wei ght is the same. If the weight continues to drop, continue to dry the 
specimens until there are 3 successive hourly readings with the same weight. After removing the specimens 
from the oven, cool them to room temperature in a desiccator before testing them . 
Before testing the specimens in a wet condition, immerse them in water for 48 h at 22oC ± 2°C. Test them 
immediately upon removal from the bath, wiping the specimens free of surface water.  
B.5 Procedure  
Position  the specimens at the centre of the testing mac hine and apply the initial load at a rate that will permit 
hand adjustment of the contact plate on the specimen. Rotate the plate back and forth through an angle of 
about 30° under a small load to properly seat the spherical block, but take care not to mov e the specimen out 
of the central position. Preferably, the rate of loading should not exceed 0 .5 MPa/s, but this requirement may 
be considered as being met if the speed of the loading head is not more than 1 mm/min.  
B.6 Calculation  
Calculate the compressive s trength of each specimen as follows:   
 
where ; 
C = compressive strength of the specimen, MPa  
W = total load, N, on the specimen at failure, and  
A = calculated area of the bearing surface in mm2. 
Round each individual result to the nearest 1 MPa . 
B.7 Report  
Report the average of all values of compressive strength of specim ens loaded perpendicular to the bedding 
(or rift) as shown in Figure. B1( a) in a dry condition as the compressive strength perpendicular to the rift in a 
dry condition. Similarly , report the values perpendicular/wet, parallel/dry as shown in Figure  B1(b) and 
parallel/wet. All determinations shall be reported as information.  
The following additional information shall be reported:  DRS 261: 2020  
17                ©RSB 2020  - All rights reserved  
 a) identification of the sample, including name and locati on of the quarry,  name or position of the ledge, 
date when sample was taken and trade name or grade of stone ; 
b) size and shape of specimens used in the tests ; and a description of the way in which the specimens 
were prepared . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
©RSB 2020  - All rights reserved                  18 
 Annex  C 
(normative)  
 
Modulus of rupture - test method  
C.1  Apparatus  
C.1.1  Testing machine  
The accuracy of the testing machine shall be within 1 % for the range from 50 to 5000 N.  
C.1.2  Load Application and Support Blocks  
The supports for the specimen shall be of the rocker type ( Figure C1 ) with edges at least as long as the width 
of the specimen. The load application block may be of either the rocker or rigid type. The portions of the load 
application and support blocks contacting the stone shall be rounded, with a nominal radius of 13 mm.  
C.2 Sampling  
 Select the sample to represent a true average of the type  or grade of stone under consideration and of the 
quality  supplied to the market under the type designation to be tested. The sample may be selected by the 
purchaser or his authorized repre sentative from the quarried stone or taken from the natural ledge and shall 
be of adequate size to permit the preparation of the desired number of test specimens. When perceptible 
variations occur, the purchaser may select as many samples as are necessary for determining the variations 
in modulus of rupture.  
C.3 Test specimens  
The specimens shall be 100 by 200 by 60 mm  in size and fabricated to tolerances of 62 mm. They shall be 
sawed from the sample and finished by grinding to smooth surfaces. The 100 by 200 -mm faces shall be as 
nearly plane and parallel as practicable. For loading perpendicular to the rift ( Note 1 ) five specimens shall b e 
prepared with the 100 by 200 -mm faces parallel to the rift planes (see Figure C1 ), and for loading parallel to 
the rift, f ive specimens shall be prepared with the 100 by 60 -mm faces parallel to the rift ( Note 2 ). When tests 
are desired on the stone in both the wet and dry condition, ten specimens shall be prepared for each direction 
of loading; that is, five for tests dry, pe rpendicular to the rift, five for tests wet, perpendicular to the rift, etc.  
NOTE 1 The term rift is used here to designate the direction in which the stone splits most easily. In stratified stones it 
is considered to coincide with the bedding or stratific ation. The rift direction should always be marked on the sample by the 
quarryman, since it often is not possible to determine it on a small block.  
NOTE 2 Another condition of loading may occur in structures when the rift planes are vertical and parallel to  the length 
of the beam. The  strength of the stone may be obtained for such loading by cutting the sp ecimens with the 260 by 200 -
mm face parallel to the rift.  The meager data available for this condition of loading indicates that the strength is at least a s 
high as when the load is applied perpendicular to the rift as shown in Figure C 1.  
 DRS 261: 2020  
19                ©RSB 2020  - All rights reserved  
  
                                                          Specimens in position for testing  
 
  
               Specimen for testing perpendicula r to lift                     Specimen for testing parallel to lift  
Note: 1 inch is equivalent to 25.4 mm  
Figure C.1 Specimens and preferred type of load application and support blocks for  determining the  
   modulus of rupture of building stone  
C.4 Marking and measuring specimens  
On the 100 by 200 -mm face, draw the center line perpendicular to one edge 60 by 200 -mm face and extend 
down both edges perpendicular to the 4 by 100 by 200 -mm face. At a distance of 90 mm each way from the 
center line, draw two similar sets of lines (span lines in Figure C 1). Mark each specimen to indicate the 
direction of the rift and label with suitable numbers or letters for identification in measuring and testing.  
 
©RSB 2020  - All rights reserved                  20 
 Measure the dimensions of the cross section on the center line. Measure the width to the nearest 0 .1 mm and 
take the thickness as the average of three measurements to the nearest 0 .1 mm, one taken at the center and 
one near each edge.  
C.5 Conditioning  
C.5.1   Before testing the specimens in a dry  condition, dry them for 48 h at 60oC±2°C. At the 46th, 47th and 
48th hour, weigh the specimens to ensure that the weight is the same. If the weight continues to drop, continue 
to dry the specimens until there are three successive hourly readings with  the same weight. After removing 
the specimens from the oven, cool them to room temperature in a desiccator before testing them.  
C.5.2  Before testing the specimens in a wet condition, immerse them in water for 48 h at 22oC ±2°C. Test  
them immediately upon remov al from the bath, wiping the specimens free of surface water.  
C.6 Procedure  
Lay the specimen flatwise on the support blocks, spaced 180 mm  apart and equidistant from the load  
application block ( Note 3 ), with all three load application and support blocks parall el. When a load of 50 N has 
been applied, stop the loading and make all load application and support blocks coincide with the marks on 
the specimen by centering the specimen under the load application block and moving the support blocks 
under the span mark s. Apply the loading at a rate not exceeding 5000 N/min until failure of the specimen.  
NOTE 3   When all three load application and support blocks are of the rocker type, care shall  be taken to adjust all three 
until the top face of the specimen is horizo ntal when loaded.  
C.7 Calculation  
Calculate the modulus of rupture of each specimen as follows:     
                                           
where;  
R = modulus of rupture, MPa,  
W = breaking load, N,  
l = length of span, mm,  
b = width of specimen, mm, and  
d = thickness of specimen, mm.  
C.8 Report  
Report the average of all values of modulus of rupture for test specimens loaded perpendicular to the rift as 
the modulus of rupture perpendicular to the rift, and report the average for all test specimens loaded parallel to 
the rift as the modulus of rupture parallel to the rift. In case any specimen gives a value of as much as 20 % 
under the average it shall be examined for defects and, if the low value appears to be due to a flaw or faulty  DRS 261: 2020  
21                ©RSB 2020  - All rights reserved  
 test piece, report the average of the remaining specimens of the group as the modulus of rupture of the 
sample for the condition of loading under consideration. Report all determinations as information.  
Report the following additional information:  
a) Identification of the sample, including  the name and location of the quarry, name and position of the 
ledge, date when sample was taken, and trade name or grade of the stone;  
b) Size and shape of specimens used in the test; and  
c) A description of the way in which the specimens were prepared  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
©RSB 2020  - All rights reserved                  22 
 Annex  D 
(normative)  
 
Abrasion resistance - Test method  
D.1 Apparatus  
The abrasion testing   apparatus shown in Fig. D1  shall be used. This apparatus consists essentially of a 
power -driven grinding lap, A, 250 mm in diameter, which is revolved at 45 rpm; three  specimen holders, B, 
with superimposed weights; gears, C, for revolving the specimen; and a means of feeding abrasive at a 
constant rate to the lap. The guide rings, D, are clamped in position slightly above the specimen holders, and 
the 2000 g weight bea ring on the specimen is the combined weight of the specimen holder, vertical shaft 
above with the attached spur gear, and a weight hopper, E, containing additional adjustment weights. The 
frame, F, carrying the guide rings is adjustable vertically to accom modate different specimen thicknesses. 
Gears, C, are adjusted on the shafts for each specimen  thickness, so that they are slightly above the plate, G, 
throughout the test.  
D.2 Sampling  
The sample may be selected by the purchaser or his authorized agent but sha ll represent the average quality 
of the  type or grade of stone under consideration. It shall be of sufficient size to permit the preparation of at 
least three test  specimens, and one face should have the finish to be exposed to traffic. The sample 
preferab ly should be 25 mm thick and  200 mm  square.  
D.3 Test specimens  
At least three specimens 50 mm square and preferably 25 mm in thickness shall be sawed from the sample. 
The sharp edges shall be rounded by grinding to a radius of approximately  1 mm  in order to prevent  crumbling 
during the test.  
D.4 Conditioning  
Dry the specimens for 48 h in a ventilated oven at a temperature of 60oC ± 2°C. At the 46th, 47th, and  48th 
hour, weigh the specimens to ensure that the weight is the same. If the weight continues to drop, co ntinue to 
dry the specimens until there are three successive hourly readings with the same weight. After removing the 
specimens from the oven, cool them to room temperature in a desiccator before testing  them.  
D.5 Procedure  
D.5.1  Weigh the test specimens to th e nearest 0.01 g; then place them in the abrasion testing apparatus . 
Remove the specimens from the apparatus, brush them free of dust, and weigh to the same precision as for 
the original weights.  
D.5.2  Place the specimens in water for an hour or more, surf ace dry them with a towel, and weigh again. 
Weigh the  specimens in water and calcul ate the bulk specific gravity.  DRS 261: 2020  
23                ©RSB 2020  - All rights reserved  
 NOTE 1  Humidity affects the results to some extent in that the rate of grinding is higher for higher humidity. For this 
reason it is advisabl e to make the test when the relative humidity is between 30 and 40 %.  
NOTE 2  The abrasive hardness value, Ha, is the reciprocal of the volume of material abraded multiplied by ten. The 
superimposed weight on the specimen is 2000 g and this is augmented by  the weight of the specimen itself. The 
correction for the weight of the specimen, included in the formula, is based on the fact that the rate of abrasion is directl y 
proportional to the weight. By basing the abrasive resistance values on the volumes, rath er than the weights abraded, a 
better comparison is obtained for materials that vary considerably in bulk density.  
D.6 Calculation  
Calculate the abrasion resistance of each specimen as follows ( Note 2 ): 
Ha= 10.95G  (2000+Ws)  / 2000Wa  
where ; 
G = bulk specific gr avity of the sample,  
Ws = average weight of the specimen (original weight plus  final weight divided by 2), in g, and  
Wa = loss of weight during the grinding operation, in g.  
D.7  Report  
 The average of the tests on individual specimens, expressed to two si gnificant figures, shall be reported as 
the abrasive resistance of the sample, but all results shall be reported as information. The report shall identify 
the type and grade of stone, its source, and the approximate date of removal from the quarry.  
 
 
 
 
 
 
 
 
 
  
©RSB 2020  - All rights reserved                  24 
  DRS 261: 2020  
25                ©RSB 2020  - All rights reserved  
 Annex  E 
(normative)  
 
Flexural strength - test method  
E.1 Apparatus  
Testing machine  (Fig. E.1 ), conforming to the requirements of the applicable sections of Practices E .4. The 
quarterpoint loading method shall be used in making flexure tests of stone employing be aring blocks which will 
ensure that forces applied to the beam will be vertical only and applied without eccentricity. The apparatus 
should be capable of maintaining the span length and distances between load -applying blocks and support 
blocks constant wit hin 6 1 mm . The load should be capable of being applied at a uniform rate and in such a 
manner as to avoid shock.  
 
NOTE 1 —Apparatus may be used inverted.  
Figure E.1 Diagrammatic view of a suitable apparatus for flexure test of stone 
E.2 Sampling  
Select the sample to represent a true average of the type or grade of stone under consideration and of the 
quality  supplied to the market under the type designation to be tested.  
The sample may be selected by the purchaser or his authorized re presentative from the quarried stone or 
taken from the natural ledge and shall be of adequate size to permit the preparation of the desired number of 
test specimens. When perceptible variations occur, the purchaser may select as many samples as are 
necessa ry for determining the variations in flexural strength.  
E.3 Test specimen  
E.3.1The test specimens shall measure100 mm wide by 30 mm thick by 350 mm long, with a span as tested 
of 300 mm. The sides of the specimen shall be at right angles with the top and botto m. The specimens shall 
have a fine abrasive finish on the planes perpendicular to the load and a fine saw finish on the other four 
planes. The dimensions of the specimen shall be measured and recorded to the nearest 0.1 mm. A minimum 
 
©RSB 2020  - All rights reserved                  26 
 of five specimens shal l be tested for each condition of test. The average value of the test results is reported as 
the flexural strength of the stone.  
E.3.2 Where the material  thickness has been set (for example, the thickness of the stone panels for the 
project has been  establ ished), it is often requested to perform flexure tests at the job thickness. The following 
shall govern the specimen size where it is requested to test at the  material thickness and it  is other than 30 
mm. The span as tested shall be 10 times the thickness . The specimen lengths shall be not less than 50 mm  
and not more than 100 mm greater than the span as tested. Where the thickness is less than 70 mm , the 
width of the specimen shall be 100 mm . Where the thickness is greater than 70 mm the width shall be 1. 5 
times the thickness. Where the thickness is other than 30 mm  and the specimen size is in accordance with the 
job thickness criteria noted in the foregoing, the average value of the test results shall be reported as the 
flexural strength of the stone at t he material  thickness.  
E.3.4  Where the  material  surface finish has been set (for example, the architectural finish on the panels for 
the project has been established), it is often requested to perform flexure tests on specimens with the finish 
the same a s on the  material . The following shall govern when it is requested to test at the  material  surface 
finish. The specimens shall have a finish on one plane perpendicular to the load in accordance with the finish 
specified for the material . Unless there is da ta to the contrary, the positioning of the specimen should be with 
the finished face in flexural tension. The average value of the test results shall be reported as the flexural 
strength of the stone at the job surface finish.  
E.3.5  Test results obtained by this test method are those of flexural strength properties. In specific 
applications, test specimens of different geometry may give useful results in terms of a modulus of rupture 
value.  
E.4 Conditioning  
E.4.1  Before testing the specimens in a dry condition , dry them for 48 h at 600C±2°C . At the 46th, 47th and 48th 
hour, weigh the specimens to ensure that the weight is the same. If the weight continues to drop, continue to 
dry the specimens until there are three successive hourly readings with the same weigh t. After removing the 
specimens from the oven, cool them to room temperature in a desiccator before testing them.  
E.4.2  Before testing the specimens in a wet condition, immerse them in water for 48 h at 22oC ± 2°C . Test  
them immediately upon removal from t he bath, wiping the specimens free of surface water.  
E.5  Procedure  
E.5.1  Assemble the apparatus and place the specimen on the span supports and adjust the quarter point 
loading blocks into contact with the specimen.  
E.5.2  Apply the load at a uniform stress ra te of 4 MPa/min to failure.  
E.6 Calculation  
Calculate the flexural strength, σ as follows:  
σ =
  DRS 261: 2020  
27                ©RSB 2020  - All rights reserved  
 where ; 
σ = flexural strength, MPa,  
W = maximum load, N,  
L = span, mm,  
L = 10 d, 
b = width of specimen, mm, b ≥ 1.5d, and  
d = depth of specimen, mm.  
E.7 Repo rt 
The report shall include the following:  
a) stone type;  
b) sizes of the specimens used;  
c) preconditioning procedure used;  
d) individual test results for each specimen;  
e) average value of the test results for each group using the following relation:  
 
 
f) standard deviat ion, s, of the test results for each group using the following relation:  
 
g) any variations from the above procedural techniques.  
The following additional information shall also be reported:  
i. identification of the sample,  
ii. name and location of the quarry   
©RSB 2020  - All rights reserved                  28 
 iii. name  and position of the ledge, date when sample was taken, and  
iv. trade name or grade of the slate.  
 DRS 261: 2020  
29                ©RSB 2020  - All rights reserved  
 Bibliography  
 
[1] ASTM C 97  Standard Test Methods for Absorption and Bulk Specific Gravity of Dimension Stone  
[2] ASTM C 170  Standard Test Method for Compressive Strengt h of Dimension Stone  
[3] ASTM C 99  Standard Test Method for Modulus of Rupture of Dimension Stone  
[4] ASTM C 241  Standard Test Method for Abrasion Resistance of Stone Subjected to Foot Traffic  
[5] ASTM C 880  Standard Test Method for Flexural Strength of Dimension Ston e 
 
 DRS 261: 2020  
 
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