ICS 91.100.15 
 
Reference number  
 DRS 484 : 2021  
© RSB 2021  
  
 RWANDA 
STANDARD  DRS 
484: 2021   
 
First edition  
2021 -mm-dd 
 
Adobe blocks (Rukarakara)  — 
Specification  
 
   
DRS 484 : 2021  
©RSB 2021  - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition 
 
 
 
 
 
 
 
 
© RSB 2021  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reproduce this document should be addressed to : 
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
KK 15 Rd, 49  
Tel. +250 788303492  
Toll Free: 3250  
E-mail: info@rsb.gov.r w 
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw   DRS 484 : 2021  
iii                ©RSB 2021  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  1 
4 Requirements  ................................ ................................ ................................ ................................  4 
4.1 Dimensions and tolerances  ................................ ................................ ................................ .........  4 
4.2 Shape and appearance  ................................ ................................ ................................ ................  4 
5 Material s and Manufacturing  ................................ ................................ ................................ ....... 4 
5.1 Materials  ................................ ................................ ................................ ................................ ........  4 
5.1.1  Soil ................................ ................................ ................................ ................................ .................  4 
5.1.2  Water  ................................ ................................ ................................ ................................ ..............  5 
5.1.3  Fibres  ................................ ................................ ................................ ................................ .............  6 
5.1.4  Stabilisers  ................................ ................................ ................................ ................................ ..... 6 
5.2 Manufacturing process  ................................ ................................ ................................ ................  6 
5.2.1  Mud preparation  ................................ ................................ ................................ ...........................  6 
5.2.2  Formin g block  ................................ ................................ ................................ ...............................  7 
5.2.3  Curing block  ................................ ................................ ................................ ................................ .. 7 
6 Performance criteria ................................ ................................ ................................ .....................  8 
6.1 Strength  ................................ ................................ ................................ ................................ .........  8 
6.2 Cracking  ................................ ................................ ................................ ................................ ........  8 
6.3 Resistance to water  ................................ ................................ ................................ ......................  9 
6.4 Resist ance to abrasion  ................................ ................................ ................................ ................  9 
Annex  A (normative)  Soil tests  ................................ ................................ ................................ .............  10 
A.1 General  ................................ ................................ ................................ ................................ ........  10 
A.2 Procedure  ................................ ................................ ................................ ................................ .... 10 
A.2.1  Snake Test  ................................ ................................ ................................ ................................ ... 10 
A.2.2  Wash  Test ................................ ................................ ................................ ................................ .... 11 
Annex  B (normative )  Drop test  ................................ ................................ ................................ .............  16 
B.1 Procedure  ................................ ................................ ................................ ................................ .... 16 
B.2 Result  ................................ ................................ ................................ ................................ ...........  16 
Annex  C (normative)  D etermination of moisture content  ................................ ................................ .. 19 
C.1 Procedure to determine appropriate moisture content  ................................ ..........................  19 
 DRS 484 : 2021  
©RSB 2021  - All rights reserved                  iv 
 Foreword   
Rwanda Standard s are prepared  by Technical Committees and approved by Rwanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda S tandards adopted 
by technical  committ ees are ratifie d by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 484  was prepared by Technical Committee RSB/TC 009, Civil engineering and building materials . 
In the preparation of this standard, reference was made to the foll owing standard s: 
1) BS EN 772 -1, Method of test for masonry units. Determination of compressive strength  
2) Rwanda Building Code -Version 2:2019 Official Gazette No. Special od 19/04/2019  
The assistance de rived from the above source is hereby acknowledged with thanks.  
Committee membership  
The following organizations were represented on the Technical Committee on Civil engineering and building 
materials  (RSB/TC 009) in the preparation of this standard.  
CIMERWA   
Enabel   
EGC Ltd   
GECO Africa  
Mass Design Group  
Rwanda Housing Authority (RHA)  
Rwanda Inspectorate, Competition and Consumer Protection Authority (RICA)  
Standard Geotechnical Engineering and Construction Ltd (STAGECO Ltd)  
SJEC Ltd  
University of Rwanda/College of Science and Technology (UR -CST)  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 484: 2021  
1                ©RSB 2021  - All rights reserved  
 Adobe blocks (Rukarakara)  — Specification  
1 Scope  
This Draft Rwanda Standard provides the requirements, sampling and test methods for adobe blocks, also 
known as “Rukarakara ” for interior and exterior use in masonry walling .   
The use of adobe blocks specified in this Draft Rwanda Standard applies to all buildings in category two (2) as 
provided in the Ministerial Order governing the categorization of buildings.  
Construction with adobe blocks is  regulated by  the Rwanda Building Code  and other related regulations.  
2 Normative references  
The following documents are referred to in the text in such a way that some or all of  their content constitutes 
requirements of this document.  For dated references, only the edition  cited applies. For undated references, the 
latest edit ion of the referenced document (including any amendments) applies.  
RS ISO 14688 -1, Geotechnical investigation and testing. Identification and classification of soil. Identification 
and description.  
RS EAS 18 -1 , Cements ― Part 1: Composition, specification and conformity criteria for common cements  
3 Terms and definitions   
For the purposes of this standard, the follow ing terms and definitions apply . 
3.1 
adobe  block / ”rukarakara ” 
air dried masonry unit made from puddled earth /soil mixture of clay, sand and silt with or without organic  
materials . It sometimes contains fibres and/or stabilizers  
3.2 
block 
discrete unit of earth masonry  with the following dimensions:  
 length between 200mm and 300 mm;  
 width between  200mm and 250 mm; and  
 height between 100mm and 150 mm. DRS 484: 2021  
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 3.3 
clay 
fine grained, natural, earthy material composed primarily of hydrous aluminium silicates with grain diameters 
less than 0.002 mm  
3.4 
compressive strength    
physical property of a material that indicates its ability  to withstand compressive forces, usually expressed in 
N/mm2. 
3.5 
curing  
the process in which adobe blocks are protected from loss of moisture and kept within a reasonable temperature 
range to increase strength and minimize cracking  
3.6 
durable  
resistant to wear  and decay. Durability has a corresponding meaning.  
3.7 
earth (for earth building)  
natural sub -soil comprised of varying percentages of clay, silt, sand and gravel which is unfired and is free of 
significant organic matter  
3.8 
erosion  
physi cal and chemical  processes by which earth building material is worn away.   It includes the processes of 
weathering and mechanical wear  
3.9 
fibres  
typically,  straw but may also be animal hair, or from sisal, agave or bamboo for instance  
3.10 
gravel  
individual rock or mineral fragments that range in diameter from 2 mm to 63 mm  DRS 484: 2021  
3                ©RSB 2021  - All rights reserved  
 3.11 
mud 
mixture of soil and water  
3.12 
sand 
individual rock or mineral fragments tha t range in diameter from 0.063 mm to 2.0 mm  
3.13 
shrinkage  
decrease in volume of earth material caused by curing or the evaporation of water  
3.14 
silt 
individual mineral particles in a soil that range in size from the upper limit of clay (0.002 mm) to the lower limit 
of fine sand (0.063 mm)  
3.15 
stabilisation  
improvement of the performance of earth building material properties by the addition of materials which bind the 
earth particles. Stabilization  may increase the resistance of earth to moisture, red uce volume changes, improve 
strength or durability. Where this standard refers to stabilization  it means chemical stabilization  
3.16 
chemical stabilization  
intermixture of cement, lime, gypsum, asphalt emulsion, or other materials with the soil before emplacement, 
and curing as appropriate for the stabilizer  and chemical reaction   
3.17 
mechanical stabilization  
compacting or compressing a plastic earth mixture , or containing earth in permanent forms such as bags  
3.18 
stabiliser  
material including cement complying with relevant standard requirements  which is used for stabilization   DRS 484: 2021  
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 4 Requirements  
The design, manufacturing and construction requirements in this standard shall be used in conjunction with 
the requirements of the relevant sections of the Rwanda Building Code.  
4.1 Dimensions  and tolerances  
4.1.1  Adobe blocks shall have the following dimensions : 
a) length  between 200 mm and 300 mm;  
b) width between  200 mm and 250 mm; and  
c) height between  100 mm and 150 mm. 
4.2.2  tolerances shall be as follows:  
a) length: +1mm, -3 mm ; 
b) width: +2 mm, -1 mm ; and  
c) height: +1 mm, -3 mm. 
4.2 Shape  and appearance  
4.2.1  Adobe blocks shall be:  
a) solid; 
b) of nominally rectangular shape; and  
c) true to the appropriate acceptable pattern.  
4.2.2  They shall be acceptably free from broken edges, honeycombing and other visible defects that could 
interfere with the proper laying of the units or impair the strength or the stability (or both) of a construction.  
5 Materials  and manufacturing  
5.1 Materials  
5.1.1  Soil 
5.1.1.1 Soils for Adobe block  are a mixture of a binder (clay), silt, sand, and gravel. These mixtures may 
be naturally occurring local soils or engineered by mixing different soils.   DRS 484: 2021  
5                ©RSB 2021  - All rights reserved  
 5.1.1.2 Soil classification by particle size shall be defined in accordance with RS ISO 14688 -1 and the 
recommended particle size distribution for adobe blocks shall be : 
a) gravel and sand 30  %-80 %;  
b) silt 10  %-30 %; and  
c) clay 10  %-40 %.  
5.1.1.3  The suitability of soil shall be determined by the Snake Test and Wash Test  in accordance with 
Annex . A. These tests shall be  performed by experienced trained masons who understand the local soil 
behaviour.  
NOTE 1  The tests determine that the soil has eno ugh clay to bind the particles together and enough granular particles 
to provide strength and limit cracking.  
NOTE 2  Mixing different soils may be required to achieve a suitable soil mix. An appropriate mix of soils may be 
determined using local knowledge from experienced trained masons, the tests identified in clause 5.1.1.3, or laboratory 
testing to achieve the recommended particle size distribution.  
5.1.1. 4 Soil shall be free from:  
a) uncontrolled organic matter. This can typically be achieved by removing t he 500  mm topsoil ; 
b) organic matter likely to rot, break down or sprout ; 
c) water - soluble salts likely to impair strength or durability ; and : 
d) large aggregates that may impair strength or homogeneous performance. The  maximum aggregates 
size shall be 25 mm in any dimension.  
5.1.2  Water  
5.1.2.1  Water shall be from a clean source such as :  
a)  rainwater ;  
b)  underground water ; 
c)  natural surface water; and 
d) potable water . 
5.1.2.2  Water shall not contain matters including:  
a) soaps,  DRS 484: 2021  
©RSB 2021  - All rights reserved                  6 
 b) detergents,  
c) oil; and  
d) harmful chemicals or sewage.  
5.1.3  Fibres  
5.1.3.1  Fibres  are generally added to blocks to reduce cracking due to drying shrinkage.  
5.1.3.2  The fibre  length  shall be between 5  cm and  7cm.  
5.1.3.3  The quantity of fibres depends on the type of soil and type of fibres being used. The optimum 
quantity can be determi ned through trial blocks . However , the quantity  of fibres shall not be less than 5 kg/m3, or 
2kg of fibre per 50 blocks sized 30x20x15  cm as a prototype . 
5.1.3.4  The type of fibres shall be determined based on local knowledge from experienced trained masons 
and they shall not rot, breakdown or sprout in the block.  
NOTE  Fibres like “ishinge ” are proven to work well.   
5.1.4  Stabilisers  
5.1.4.1  Stabilisers  may greatly improve strength and durability.   
5.1.4.2  Stabilisers should only be used when there is no other viable strategy for achieving the project 
requirements  because they have a high embodied carbon and permanently alter the soil, reducing its poten tial 
future uses.  
5.1.4.3  If stabilisers  are required, the minimum quantity should be used to achieve the project requirements  
and they shall comply  with relevant standards requirements  
NOTE 1  Portland cement and lime are the most used chemical stabilisers . 
NOTE  2 Stabilisers may impact curing times and the required curing conditions.  
5.2 Manufacturing process  
5.2.1  Mud preparation  
5.2.1.1  The mud shall be prepared so that it meets the requirements of clause 5.2.1.2. If stabilisers are 
used , they shall be well mixed with the dry soil.  
5.2.1.2  Water shall be added to the soil so that the mud has a consistency that enables it to be worked into 
the mould. Excessive water will increase shrinkage cracks and too little water will make it difficult to compact 
the mud i n the mould. The optimal moisture content for making adobe blocks  shall be determined in accordance 
with Annex C . DRS 484: 2021  
7                ©RSB 2021  - All rights reserved  
 5.2.1.3  Depending on the soil type and its existing moisture content, the volume of soil shall be between 5 
and 7 times the volume of water. ( Water/soil ratio shall be between1:5 and 1:7)  
5.2.1.4  It is recommended to leave the mud for between 12  h and 24 h to improve water distribution and 
activate the clays cohesive properties. This should not be done if cement stabilisers are used.  
5.2.1.5  If fibres are used then they shall be evenly mixed into the mud.   
5.2.1.6  It should be demonstrated through prior experience that fibres will not rot, break down or sprout in 
the block.  
5.2.2  Forming block  
5.2.2.1  The size of the block shall be determine d based on the design and construction requirements. The 
influencing factors include : 
 the size and weight to allow safe and efficient handling ; 
 thickness of the wall to be built since it is common to use a single block width ; 
 corner bonds. Different sized blocks may be required at corners ; and  
 excessive shrinkage may occur in larger blocks. Blocks with dimensions greater than 300mm are not 
recommended and should be considered carefully.  
5.2.2.2  The internal face of the mould shall be cleaned of any stuck mud and soaked before the new mud 
is added to limit soil adhesion.  
5.2.2.3  The blocks shall be  manufactured where they are to be cured and close to where they will be stored 
to avoid damage due to transporting them between locations.  
5.2.2 .4 Mud shall be added to the mould in at least three layers of approximately equal thickness and 
compacted into  the corners.  
5.2.3  Curing block  
5.2.3.1  It is recommended that blocks are air dried, not sun-baked . This is to say that they should be shaded 
from direct strong sunlight, especially in the first 4 days of curing, but still have adequate airflow around the 
block s. Excessive exposure to strong sun can accelerate surface drying and cause cracking. If curing in a 
shaded area is not possible, in the case of strong sunlight the blocks shall   be covered with grass or banana 
leaves or a layer of soil or sand to prevent  immediate cracking.   
5.2.3.2  Protection from rain and surface water is extremely important throughout the curing period and 
when in the wall and not covered by a roof. A plastic sheet shall be used to protect the blocks from rain however 
it should not lim it airflow or drying of blocks for long periods of time.  DRS 484: 2021  
©RSB 2021  - All rights reserved                  8 
 NOTE  Other forms of rain protection such as banana leaves provide limited protection during large rainfall and do not 
allow the blocks to dry if placed directly against them. Raising the blocks off the ground and providing a bund around the 
curing area will help to protect them from surface water during large rainfalls.   
5.2.3.3  Following initial drying, the blocks should be turned onto their side when strong enough to do so, 
and then rotated every 3 -4 day s. Depending on the size of block and the weather, curing may take between 1 
week and 2 months, and blocks shall not be used before they are fully cured.   When they are fully cured, the 
block has the same colo ur as the dry soil they were made from, a nd when tapped with a coin they produce a 
‘clear ring’.   
5.2.3.4  Dry blocks shall be stacked in rows not exceeding 7 number.  
5.2.3.5  Blocks stabilised with cement shall be damp cured for at least 1 week before being air dried. During 
damp curing the blocks  are not allowed to dry.  
6 Performance criteria  
6.1 Strength  
6.1.1  Compressive strength shall be performed in accordance with BS EN 772 -1:2011+A1:2015 . 
6.1.2  The minimum  compressive strength is 0.5N/m m2. 
6.1.3  The Block  Drop Test may be used as an indicator of strength.  
6.1.4  At least 20 trial blocks should be made using the same materials and techniques expected to be used 
in the future manufacture of blocks. These trial blocks should be tested using the Block Drop Test  and if 80% 
pass the blocks may be considered to have met the required minimum compressive strength  as per Annex B .  
6.1.5  If any part of the mixture or manufacturing process changes during construction then the testing 
described in clause 6.1.4 shall be p erformed again. Any of the following would require testing to be performed 
again:  
 soil from another location is used ; 
 the type of soil in the pit clearly changes, often indicated by changes in colour or particle size ; and  
 fibre type or quantity of fibre is  changed . 
6.1.6  If still suitable , the broken blocks from the test may be used in the building as half blocks at openings 
or wall ends.  
6.2 Cracking  
6.2.1  Cracks occur  due to the natural shrinkage of blocks as they cure.  
6.2.2  Cracks  that do not impair structural integrity or handling of blocks are acceptable.  DRS 484: 2021  
9                ©RSB 2021  - All rights reserved  
 6.2.3  Cracks  less than 3  mm in width are typically acceptable.  
6.2.4  It is recommended  that not more than 10  % of blocks in a wall contain cracks wider than 3  mm and 
longer than 75  mm or, irrespective of the crack length or width, deeper than 10  mm along any part of the crack.  
6.2.5  Cracks may be reduced by modifying the soil mix, limiting the size of the blocks, m odifying fibre content, 
or reducing  curing speed.  
6.3 Resistance to water  
6.3.1  Unstabilised earth can lose much of its structural strength when moist or wet. Rukarakara should not 
therefore be used for below -grade applications such as foundations or retaining  walls. When exposed to 
weather, Rukarakara is very susceptible to water erosion which may reduce the width of the wall over time. This 
is a common problem at the base of walls where a horizontal cavity develops due to rain coming down the face 
of the wall  and rain splash from the ground.   
6.3.2  There is no minimum requirement for the block itself because durability provisions should be put in 
place to protect the block from water, and therefore it may never encounter durability issues, even if the block 
itself is not resistant to water.   
6.3.3   Recommended methods of protecting the block from water include:  
a) adequate roof overhangs to reduce driven rain - recommended length of roof overhang for full protection 
is one third of the wall height  
b) sacrific ial protection layer, typically an earth plaster that is maintained over time ; and  
c) elevating the blocks, for example on a stone plinth, above any potential ground water or rainwater splash 
back - recommended elevation 200  mm above external ground level, 50 mm above internal ground level   
6.3.4  Stabilization can also be used to increase resistance to water.  
6.4 Resistance to abrasion  
6.4.1  Adobe block is susceptible to erosion from abrasion. Abrasion is particularly common at corners of 
buildings and doorways , which are areas key to the structural integrity of buildings. Excessive erosion will reduce 
structural integrity.  
6.4.2  There is no minimum requirement for the block itself because the block may be protected from abrasion 
and therefore never encounter perfor mance issues even if the block itself is not resistant to abrasion.  
6.4.3  The recommended method of protecting the block from abrasion is to add a sacrificial protection layer, 
typically an earth plaster that is maintained over time. Increasing the thickne ss of this layer at the corners of 
buildings and either side of doorways will increase protection to areas of the building most susceptible to 
abrasion.  
6.4.4  Stabilization can also be used to increase resistance to abrasion.  DRS 484: 2021  
©RSB 2021  - All rights reserved                  10 
 Annex  A 
(normative ) 
 
Soil tests  
A.1 General  
The Snake Test and Wash Test shall be performed to determine if the soil is appropriate for making adobe 
blocks. The process is as follows:  
a) Perform the snake test using the methodology below.  
b) If the soil fails the snake test (i.e. the soil cannot b e rolled into a 3 mm diameter thread) then the soil is 
not plastic enough and is not recommended for making adobe blocks.  
c) If it passes the snake test (i.e. the soil sample can be rolled into a 3 mm diameter thread), the wash test 
shall be performed in acco rdance with the methodology below to work out the percentage of coarse 
material (sand and gravel) in the soil.   
d) If the amount of coarse material in the soil is outside the recommended values in this document, which 
is 30 to 80  %, the soil is not recommende d for adobe blocks.  
e) If the amount of coarse material in the soil is within the recommended values in this document then the 
soil is recommended for adobe blocks and trial blocks shall be made.  
A.2 Procedure  
A.2.1  Snake Test  
A.2.1.1  The purpose of the  snake test is t o check the plasticity of soils. Being plastic means that they have 
a noticeable amount of clay. To do that, place a small amount of wet soil free from gravel between palms. 
Confirm the moisture content is correct according to Annex C. Roll the soil until it forms a long, round thread of 
about 3 mm diameter. If it fails to be rolled into such a thread, it will not be plastic and not recommended for 
making adobe blocks. Where this is the case - the soil can be mixed with a finer soil in order to increase pla sticity, 
and this test should be repeated.  The typical process is presented below.  DRS 484: 2021  
11                ©RSB 2021  - All rights reserved  
  
Figure 1: Snake test demonstrating soil has appropriate plasticity levels  
 
A.2.1.2  As a note, it is essential to make sure that the soil is not too dry or too wet. If it is too dry, it may 
crumble in hands immediately after starting to roll it, and if it is too wet, it may tend to stick to hands resisting to 
get rolled between palms of hands.  
 
 
Figure 2: Left - too dry, Right - too wet  
A.2.2  Wash  Test  
A.2.2.1  Materials required:  
• Soil, roughly 3kg  
• Weighing scale of 0.1kg accuracy  
• Large plastic sheet  
DRS 484: 2021  
©RSB 2021  - All rights reserved                  12 
 • Buckets x 2  
• 1L bottle for measuring water  
A.2.2.2  Take a representative sample of soil of about 3kg, free from vegetation debris and other organic 
material. The soil for making adobe blocks should be collected after stripping off the top soil to a depth of at 
least 0.5 m from the ground surface.  
A.2.2.3  Weigh the soil with a scale and record its (wet) weight (Ww).  
A.2.2.4  Air dry the soil sample for at least 48h p referably in the sun. Try to disperse the soil over a large 
plastic sheet so that soil thickness does not exceed 5 mm.   
 
Figure 3: Dispersing soil over large plastic sheet  
A.2.2.5  Touch through it thoroughly every 1 to 2 hours turning it in all directions to allow even drying.  
 
Figure 4: Touch through soil thoroughly  
DRS 484: 2021  
13                ©RSB 2021  - All rights reserved  
  
 
A.2.2.6  Weigh  the soil after the drying process and record its dry weight (Ws).  
A.2.2.7  Put the dry soil into a bucket and add water little by little while mixing to break clumped soil. You 
will need to add about 6 liters of water.  
 
Figure 5: Adding water to dry soil in bucket  
A.2.2.8  Once all clumped  soil has been broken, agitate vigorously using a hand for about 1min. The mixture 
should look homogenous, there should be no remaining clumps of soil, and instead it should be possible to feel 
sand grains and gravel pieces.  
 
Figure 6: Agitate soil to bre ak down all clumps  
A.2.2.9  After agitation, leave the mixture to stand for about 1 minute. The coarser material will settle to the 
bottom of the bucket and the fines will remain in suspension.  
DRS 484: 2021  
©RSB 2021  - All rights reserved                  14 
  
Figure 7: Coarser material settles first  
A.2.2.10  Pour out the slurry (i.e. fines in suspension) gently into another bucket and stop when you reach 
the deposit which looks like a thick slurry at the bottom of the bucket.  
 
Figure 8: Pour out the slurry of fine material, keep the coarse material at the bottom  
 
 
A.2.2.11  Add water, and repeat the process from step A.2.2.7  to step A.2.2.9 . 
A.2.2.12  Repeat the process over and over again until you remain with clean coarse material (sand and 
gravel) as a deposit at the bottom of the bucket. The water should appear clear. Air dry the material on a plastic 
sheet preferably in the sun for at least 4 hours or until it is visually dry. Weigh the dry amount of coarse material 
and record its weight (Ds).  
DRS 484: 2021  
15                ©RSB 2021  - All rights reserved  
  
Figure 9: Remaining clean coarse material  
A.2.2.13  Work out the percent amount of coarse material (sand and gravel) in the soil as (Ds/Ws)  x100.  
  
DRS 484: 2021  
©RSB 2021  - All rights reserved                  16 
 Annex  B 
(normative ) 
 
Drop test  
B.1 Procedure  
B.1.1  A block shall be selected that is fully cured  
B.1.2  The block shall have a length of between 1 and 2 times its width. The block may be cut so that it has 
this ratio.  
B.1.3  It shall be dropped on its corner as shown in Figure 10 from a height of 900mm onto a hard surface, 
such as compacted earth.  
 
Figure 10: Orientation of adobe block prior to dropping  
B.2 Result  
B.2.1  The block shall pass if the following criteria are met:  
a) it does not shatter or break into approximately equally sized pieces  
b) there shall not be a piece broken off that has a dimension either:  
DRS 484: 2021  
17                ©RSB 2021  - All rights reserved  
 ⎯ greater than the smallest dimension of the block. For instance if the block has 
dimensions 300x200x100, then the maximum size of the broken piece shall be 
100mm. 
⎯ greater  than 150mm.  
 
Figure 11: Shattered block: FAIL  
 
Figure 12: Block  broken in half: FAIL  
 
DRS 484: 2021  
©RSB 2021  - All rights reserved                  18 
  
Figure 13: Small piece broken off block corner: Measure according to Figure 14  
 
Figure 14: How to measure broken piece - if less than 150mm : PASS  
 
B.2.2  The following  are recommendations based on the pass rate of at least 20 blocks.  
a) > 80% pass rate: block performs well  
b) 60-80% pass rate: block is acceptable but recommend improvements, such as mixing with another soil 
to improve the properties and testing again  
c) < 60% pas s rate: strongly recommend not using the soil. Mixing with a significant percentage of another 
soil may improve the properties. Test again after mixing.  
DRS 484: 2021  
19                ©RSB 2021  - All rights reserved  
 Annex  C 
(normative ) 
 
Determination of moisture content  
C.1 Procedure to determine appropriate moisture content  
The optimal amount of water in a mud paste is determined by taking a handful of the mixture and squeezing it 
to see how wet it is in the hand, and how much mud exits through the fingers. More information is provided in 
the table below.  
 
 
DRS 484 : 2021  
 
Price based on  20 pages  
©RSB 2021  - All right s reserved