ICS 91.100. 10 
 
Reference number  
DRS 514-2: 2022  
© RSB 2022  
  
 RWANDA 
STANDARD  DRS 
514-2  
 
First e dition  
2022 -mm-dd 
 
 
Compressed earth blocks —  
Part 2: Earth mortars  
   
DRS 514-2: 2022  
©RSB 2022  - 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 2022  
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 : 
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Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw   DRS 514-2: 2022  
iii                ©RSB 2022  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  1 
4 Classification of EMs  ................................ ................................ ................................ ...................  1 
4.1 Classification according to use  ................................ ................................ ................................ .. 1 
4.1.1  Ordinary EMs (EM O) ................................ ................................ ................................ ....................  1 
4.1.2  Facing EMs (EM F)  ................................ ................................ ................................ ........................  2 
4.2 Classification according to field of use  ................................ ................................ .....................  2 
4.2.1  Mechanical constraints  ................................ ................................ ................................ ................  2 
4.2.2  Environmental constraints  ................................ ................................ ................................ ..........  2 
5 Designation of EMs  ................................ ................................ ................................ ......................  3 
6 Technical specifications for ordinary earth mortars  ................................ ................................  3 
6.1 General characteristics  ................................ ................................ ................................ ................  3 
6.2 Textural characteristics  ................................ ................................ ................................ ...............  4 
6.3 Appearance characteristics  ................................ ................................ ................................ ........  4 
6.3.1  General appearance  ................................ ................................ ................................ .....................  4 
6.3.2  Cracks  ................................ ................................ ................................ ................................ ............  4 
6.4 Physicochemical characteristics  ................................ ................................ ................................  4 
6.4.1  Pitting ................................ ................................ ................................ ................................ .............  4 
6.4.2  Efflorescence  ................................ ................................ ................................ ................................  4 
6.5 Mechanical, hygrometric and physical characteristics  ................................ ............................  4 
7 Technical specifications for facing earth mortars  ................................ ................................ .... 5 
7.1 General characteristics  ................................ ................................ ................................ ................  5 
7.2 Textural characteristics  ................................ ................................ ................................ ...............  5 
7.3 Appearance characteristics  ................................ ................................ ................................ ........  5 
7.3.1  General appearance  ................................ ................................ ................................ .....................  5 
7.3.2  Cracks  ................................ ................................ ................................ ................................ ............  5 
7.3.3  Colour  ................................ ................................ ................................ ................................ ............  5 
7.4 Physical -chemical characteristics  ................................ ................................ ..............................  5 
7.4.1  Pitting ................................ ................................ ................................ ................................ .............  5 
7.4.2  Efflorescence  ................................ ................................ ................................ ................................  5 
7.5 Mechanical, hygrometric and physical char acteristics  ................................ ............................  6 
8 Code of practice for the preparation of earth mortars  ................................ .............................  6 
8.1 Recommendations on earth selection  ................................ ................................ .......................  6 
8.1.1  Granular composition  ................................ ................................ ................................ ..................  6 
8.1.2  Plasticity  ................................ ................................ ................................ ................................ ........  7 
8.1.3  Nature  ................................ ................................ ................................ ................................ ............  9 
8.2 Recommendations for the use of stabilisation addi tives ................................ .......................  10 
8.2.1  Precautions to take when stabilising by adding a physicochemical additive  .....................  10 
8.2.2  Cement stabilisation  ................................ ................................ ................................ ..................  11 
 DRS 514-2: 2022  
©RSB 2022  - 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 adop ted 
by Technical committ ees are ratified  by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 514-2 was prepared by Technical Committee RSB/TC 9, Civil engineering and building materials.  
In the preparation of this s tandard, reference was made to the following standard:  
ARS 670 -2-2014, Compressed earth blocks - Part 2 : Earth mortars  
The assistance de rived from the above source is hereby acknowledged with thanks.  
DRS 514 consists of the following parts, under the general title Compressed earth blocks : 
⎯ Part 1: Definitions, classifications, specifications  
⎯ Part 2 Earth mortars  
⎯ Part 3: Test methods  
⎯ Part 4: Code of practice for production and construction  
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.  
A+Construction Group Ltd  
Africeramics Ltd  
Consultants Engineers Group (CEG) Ltd 
D&D Resources Ltd  
Dutureheza Ltd  
Enabel Rwanda  
Greenpack Africa Ltd  DRS 514-2: 2022  
v                ©RSB 2022  - All rights reserved  
 Integrated Polytechnic Regional Centre (IPRC) - Musanze  
Mass Design Group  
NP Construction Construction Company (NPCC) Ltd  
Road Transport Development Agency (RTDA)  
Rwanda Housing Autho rity (RHA)  
Rwanda Inspectorate, Competition and Consumer Protection Authority (RICA)  
Rwanda Quarries Association (RQA)  
SKAT Consult  
St Joseph Engineering Company (SJEC) Ltd  
Standards for Sustainability (SfS)  
Stonecraft Industries Ltd  
University of Rwanda - College of Science and Technology (UR - CST)  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 514-2: 2022  
©RSB 2022  - All rights reserved                  vi 
 Introduction  
The aim of the present standard is to define earth mortars (EMs), to classify them according to their appearance, 
their conditions of use, and to determ ine the categories into which they fall as well as their designations.  
The definitions, classifications and designations of the present standard are applicable in drawing up all 
technical, administrative and contractual documents relating to compressed ea rth block technology, and relate 
both to public and to private contracts.  
The standard applies exclusively to EMs intended for the realisation of simple built structures in common 
masonry with thick mortar joints (walls, partitions, piers, small lintels, arches, vaults, domes, etc.) and of any 
similar built structure.  
The standard applies only to mortars prepared on site and intended to be used on the spot.  
The standard does not apply to EMs used for flooring or tiling, nor does it apply to reinforced masonry.  
The standard is not applicable in areas subject to earthquakes, floods or cyclones to an extent that requires the 
application of appropriate rules in order to avoid major damage.  
 DRS 514-2: 2022  
1                ©RSB 2022  - All rights reserved  
 Compressed earth blocks — Part 2 : Earth mortars  
1 Scope  
This Draft Rwanda Standard define s earth mortars (EMs), classif ies them according to their appearance, their 
conditions of use, and specifies  categories into which they fall as well as their designations.  
2 Normative references  
The following referenced documents are indispensable for the application of this document. For dated 
references, only the edition cited applies. For undated references, th e latest edition of the referenced document 
(including any amendments) applies.  
DRS 546, Clay products for building – Vocabulary  
3 Terms and definitions  
For the purposes of this standard, the terms and definitions given in DRS 546 a nd the following apply.  
4.1 
earth mortar  (EM)  
mortar used for compressed earth block masonry of a traditional type using thick mortar joints. An earth mortar 
consists principally of raw earth and water and owes its cohesion in a humid or a dry state essentially to the 
clay fraction  of the earth; an additive and/or filler can, however, be added to the earth to improve or enhance 
particular characteristics of the mortar  
4 Classification of EMs  
4.1 Classification according to use  
EMs can be classified into two groups according to use:  
(i) ordinary EMs;  and 
(ii) facing EMs.  
4.1.1  Ordinary EMs (EM O)  
These are EMs used in masonry structures intended to be covered by some form of protection.   
©RSB 2022  - All rights reserved                  2 
 4.1.2  Facing EMs (EM F)  
These are EMs used in masonry structures intended to remain visible. One can differentiate between:  
(i) normal facing EMs (EM NF);  and 
(ii) fine facing EMs (EM FF).  
The difference between these two facing EMs is restricted to their appearance without affe cting their other 
characteristics.  
4.2 Classification according to field of use  
The fields of use of EMs within masonry structures are classified according to two types of constraint which can 
occur simultaneously:  
(i) mechanical constraints;  and 
(ii) environmental constraints.  
4.2.1  Mechanical constraints  
These are defined according to three categories of resistance:  
(a) category 1: structural elements which are not load -bearing and structural elements capable of withstanding 
limited external (live) loads: e.g.: fill -in in a load -bearing structure; boundary wall; a single -storey building made 
of load -bearing structural elements.  
(b) category 2: structural elements capable of withstanding important external (live) loads: e.g.: a two -storey 
building with acces sible terrace made of thin load -bearing structural elements.  
(c) category 3: structural elements capable of withstanding high external (live) loads e.g.: a three -storey public 
building made of thin load -bearing structural elements.  
4.2.2  Environmental constraint s 
These are defined by 4 categories of environment:  
(a) category D: structural elements located in a dry environment with no danger of being wet: e.g.: internal 
partitions; external walls which are not exposed or which are protected from water damage  
(b) category R: structural elements capable of withstanding water damage by lateral spraying: e.g.: lateral walls 
exposed to rain; bathroom walls being splashed  
(c) category C: structural elements capable of withstanding water damage by vertical penetration (c apillary 
rise, penetration by gravity, suction or internal condensation): e.g.: external walls unprotected from capillary 
rise; internal walls unprotected from water leaking through the roof)  DRS 514-2: 2022  
3                ©RSB 2022  - All rights reserved  
 (d) category A: structural elements capable of withstanding mech anical abrasion (impact, rubbing or wind 
damage): e.g.: corners or walls subject to impact; areas subject to rubbing by animals; areas subject to sand 
storms).  
5 Designation of EMs  
The designation of earth mortars includes the following indications, to be gi ven in the same order:  
a) product designation  
⎯ EM for «earth mortar»;  
b) designation according to use:  
⎯ for «ordinary»  
⎯ F for «facing»  
⎯ NF for «normal facing»  
⎯ FF for «fine facing»;  
c) designation according to mechanical constraints  
⎯ 1 for «category 1»  
⎯ 2 for «category 2»  
⎯ 3 for «category 3»;  
d) designation according to the constraints of the hygrometric environment  
⎯ D for «category C»  
⎯ R for «category R»  
⎯ C for «category C»;  
e) designation according to the constraints of the mechanical abrasion environment:  
⎯ A for «cat egory A».  
f) The EM designation may also include the following indications to be given in the same order:  
⎯ colour;  
⎯ any other feature which helps to identify EMs.  
Table 1 — Examples of designation  
Designation  Description   Example   
EM O 1 D  Ordinary earth mortar used as an element in 
a non -load bearing structure in a dry 
environment not subject to mechanical 
abrasion  Internal partition of a single family 
ground floor house  
EM FF 3 RA  Fine facing earth mortar used as an element 
in a load -bearing structure exposed to rain 
weathering by lateral spraying as well as to 
mechanical abrasion  External wall of a 3 -storey building 
of high quality appearance 
exposed to driving rain and to sand 
storms  
6 Technical specifications for ordinary e arth mortars  
6.1 General characteristics  
The characteristics of ordinary mortars must be compatible with the category of blocks chosen.   
©RSB 2022  - All rights reserved                  4 
 6.2 Textural characteristics  
The earth must contain at least 90% of grains the dimensions of which are less than 1/3 of the thi ckness of the 
joint. 10% of grains with a maximum dimension of between 1/3 and 1/2 of the thickness of the joint is tolerated. 
The use of an earth mortar, the largest grain size of which is less than or equal to 4 mm is recommended.  
6.3 Appearance characteristics  
6.3.1  General appearance  
Ordinary EMs should display no systematic defects such as cracks or significant chips of a kind likely to 
jeopardise correct execution and the stability of the masonry.  
6.3.2  Cracks  
Micro -cracks and macro -cracks can be tolerat ed on all surfaces but their presence must not be concentrated or 
systematic over a part or the whole of the built structure.  
6.4 Physicochemical characteristics  
6.4.1  Pitting  
No pitting due to the bursting of expansive materials is tolerated.  
6.4.2  Efflorescence  
Ordina ry EMs must not display any significant and lasting efflorescence covering a large area of the EM. A faint 
whitish film or a thin band are not taken into account.  
6.5 Mechanical, hygrometric and physical characteristics  
Table 2 — Mecha nical, hygrometric and physical characteristics of ordinary earth mortars  
Designation  Environmental 
constraint 
category  Mechanical 
constraint 
category  fb dry 
N/mm2 fb wet 
N/mm2 Water 
absorption 
% Abrasion 
Loss of 
matter %  
EM O 1 D  Dry environment  
(D) 1 0.5 N/A N/A N/A 
EM O 2 D  2 1.5 N/A N/A N/A 
EM O 3 D  3 2.5 N/A N/A N/A 
EM O 1 R  Effect of water by 
lateral spraying  
(R) 1 0.5 0.5 ≤30 N/A 
EM O 2 R  2 1.5 1 ≤20 N/A 
EM O 3 R  3 2.5 1.5 ≤10 N/A 
EM O 1 C  Effect of water  
by vertical  
penetration (C)  1 0.5 0.5 ≤30 N/A 
EM O 2 C  2 1.5 1 ≤20 N/A 
EM O 3 C  3 2.5 1.5 ≤10 N/A 
1) N/A = not applicable  
 
2) The use of EMs in R and C category environments requires using a stabiliser if the protection provided is not guaranteed. If the 
protection provided against water damage is guaranteed, the environment is regarded as category D.  
 DRS 514-2: 2022  
5                ©RSB 2022  - All rights reserved  
 3) If tests to establis h water absorption or abrasion are not feasible, or if the results are not available, this deficiency can be 
compensated by increasing the requirements for the dry and/or wet compressive strength by one category.  
 
4) The values given are the average value s obtained from tests carried out on a set of samples.  
7 Technical specifications for facing earth mortars  
7.1 General characteristics  
The characteristics of facing mortars must be compatible with the category of blocks chosen.  
7.2 Textural characteristics  
The ear th should not contain grains larger than 1/3 of the thickness of the joints. The use of an earth mortar , 
the largest grain size of which is less than or equal to 4 mm is recommended.  
7.3 Appearance characteristics  
7.3.1  General appearance  
Facing EMs should display no systematic defects such as cracks or significant chips of a kind likely to jeopardise 
correct execution and the stability of the masonry.  
7.3.2  Cracks  
(a) Micro -cracks: can be tolerated on all exposed faces.  
 
(b) Macro -cracks: Conditions of acceptability for all faces:  
 
(i) they must not exceed 0.5 mm in width;  
 
(ii) they must not exceed 20 mm in length;  
 
(iii) they must not exceed 10 mm in depth;  
 
(iv) the presence of acceptable macro -cracks must not be concentrated or found through out one part 
or the whole of the built structure.  
7.3.3  Colour  
The colour of facing EMs should be uniform throughout the built structure. It may differ from that of the CEBs.  
7.4 Physical -chemical characteristics  
7.4.1  Pitting  
No pitting due to the bursting of expansive materials is tolerated.  
7.4.2  Efflorescence  
Facing EMs must not display any significant and lasting efflorescence covering a large area of the EM. A faint 
whitish film or a thin band are not taken into account.  
  
©RSB 2022  - All rights reserved                  6 
 7.5 Mechanical, hygrometric and physical characteris tics 
Table 3 — Mechanical, hygrometric and physical characteristics of facing earth mortars  
Designation   Environmental 
constraint 
category  Mechanical 
constraint 
category  fb dry 
N/mm2 fb wet 
N/mm2 Water 
absorption 
% Abrasion 
loss of 
matter %  
EM NF 1 D or EM FF 1 D  Dry environment  1 0.5 N/A N/A ≤15 
EM NF 2 D or EM FF 2 D  (D) 2 1.5 N/A N/A ≤10 
EM NF 3 D or EM FF 3 D   
3 2.5 N/A N/A ≤5 
EM NF 1 R or EM FF 1 R  Effect of water 
by 1 0.5 0.5 ≤30 ≤15 
EM NF 2 R or EM FF 2 R  lateral spraying  2 1.5 1 ≤20 ≤10 
EM NF 3 R or EM FF 3 R  (R) 3 2.5 1.5 ≤10 ≤5 
EM NF 1 C or EM FF 1 C  Effect of water  1 0.5 0.5 ≤30 ≤15 
EM NF 2 C or EM FF 2 C  by vertical  2 1.5 1 ≤20 ≤10 
EM NF 3 C or EM FF 3 C  penetration (C)  3 2.5 1.5 ≤10 ≤5 
1) N/A = not applicable  
 
2) The use of EMs in R and C category environments requires using a stabiliser if the protection provided is not guaranteed. If 
the protection provided against water damage is guaranteed, the environment is regarded as category D .  
 
3) If tests to establish water absorption or abrasion are not feasible, or if the results are not available, this deficiency can be 
compensated by increasing the requirements for the dry and/or wet compressive strength by one category.  
 
4) The values give n are the average values obtained from tests carried out on a set of samples.  
8 Code of practice for the preparation of earth mortars  
8.1 Recommendations on earth selection  
Selecting a suitable type of earth can take place in the field using parameters which are the fruit of experience 
acquired in the course of operational practice. If any doubt persists, laboratory identification tests should be 
carried out.  
 
8.1.1  Granular compo sition  
The granular composition of the earth should preferably fall within the limits of the shaded area on the diagram 
of texture which follows and should be similar in shape.  
 
The limits of the recommended shaded area are approximate.  
 
Types of earth t he granular composition of which fall within the recommended shaded area in most cases give 
satisfactory results.  
Types of earth the granular composition of which fall outside the shaded area may still give acceptable results, 
but it is recommended that t hey be subjected to a series of tests enabling their suitability to be assessed.  DRS 514-2: 2022  
7                ©RSB 2022  - All rights reserved  
  
Figure 1 — Diagram of texture  
8.1.2  Plasticity  
The plasticity of the soil should preferably fall within the limits of the shaded area of the diagram of plasticity 
which follows.  
The limits of the recommended shaded area are approximate.  
Types of earth the plasticity of which fall within the recommend ed shaded area in most cases give satisfactory 
results.  
Types of earth the plasticity of which fall outside the shaded area may still give acceptable results, but it is 
recommended that they be subjected to a series of tests enabling their suitability to be assessed.  
 
©RSB 2022  - All rights reserved                  8 
  
Figure 2 — Diagram of plasticity  
DRS 514-2: 2022  
9                ©RSB 2022  - All rights reserved  
 8.1.3  Nature  
 
Figure 3 — Classification of materials according to their nature  
The nature of types of earth is determined by the combination of val ues resulting from tests for particle size 
distribution, plasticity and methylene blue value. The overall suitability of types of earth is as follows:  
 
A1: an acceptable material but with slightly too many fines.  
 
A2: an acceptable material but with too many fines.  
 
©RSB 2022  - All rights reserved                  10 
 A3: an acceptable material but requiring particular care, as it is relatively active.  
 
A4: a material which is difficult to use, as it is very active.  
 
B1: a sandy material requiring fines to be added to make it acceptable.  
 
B2: an acceptable material slightly lacking in fines.  
 
B3: a sandy material requiring a considerable addition of fines to make it acceptable.  
 
B4: an acceptable material lacking in fin es.  
 
B5: an acceptable material but slightly lacking in fines.  
 
B6: an acceptable material but slightly lacking in fines.  
 
C1: a material containing too much gravel, which should be sieved to change its nature.  
 
C2: a material containing too much gravel, which should be sieved to change its nature.  
 
D1: a sandy material requiring fines to be added to make it acceptable.  
 
D2: a sandy material requiring a considerable addition of fines to make it acceptable.  
 
D3: A material containing too much gravel, which should be sieved to change its nature and which requires 
a considerable addition of fines to make it acceptable.  
 
R: unsuit able materials.  
 
F: materials requiring advanced identification tests notably with regard to their chemical analysis and 
mechanical tests in order to be able to determine their suitability. Testing pre -production stage CEBs 
should be considered.  
 
8.2 Recommendations for the use of stabilisation additives  
8.2.1  Precautions to take when stabilising by adding a physicochemical additive  
The presence of certain salts or organic materials can affect the efficacy of stabilising by the addition of an 
additive. In th ese cases, some chemical analysis should be therefore be undertaken to determine the presence, 
the value and the concentration of the following factors:  
⎯ pH; 
⎯ soluble salts;  
⎯ acid salts;  
⎯ alkaline salts;  
⎯ organic matter or humus;  
⎯ carbonates;  
⎯ sulphates;  
⎯ chlorid es. DRS 514-2: 2022  
11                ©RSB 2022  - All rights reserved  
 8.2.2  Cement stabilisation  
8.2.2.1  Efficacy and dosage  
As earth mortars are used in a plastic state, up to 50 % more cement is sometimes required to obtain the same 
efficacy as when using the same type of earth, compressed in a humid state, for the manufacture of CE Bs.  
 
The efficacy of the dosages depends on the texture and structure of the earth, and on how it is used. 6 to 12% 
of the weight of the dry earth generally gives good results. Compressive strength remains highly dependent on 
the dosage.  
 
The dosages ind icated are relative to dry weight and are determined in laboratory conditions. Measures for 
checking in the workshop or on site should take account of the specific hygrometric conditions existing locally.  
 
8.2.2.2  Efficacy parameters  
(1) Types of earth  
 
Almost all types of earth can be stabilised with cement. The best results are obtained with sandy types of 
earth.  
 
(2) Organic matter  
 
This is recognised as deleterious, and as a general rule, an organic matter content in excess of 1% is 
risky; earth cont aining more than 2% should not be used.  
 
(3) Sulphates  
 
When dry, calcium sulphates, which are frequently found, are less deleterious than magnesium sulphates. 
When wet, sulphates are always very deleterious. Sulphates destroy the hardened hydraulic binde r matrix 
and increase the sensitivity to humidity of the clays. A specific study for earth containing more than 2 to 
3% total sulphate content is indispensable.  
 
(4) Oxides and metallic hydroxides  
 
Essentially, these are iron and aluminium oxides which are rarely present in excess of around 5% and 
which in that event have little effect. In types of earth containing more than 5%, stabilisation has been 
observed to be highly effective with little cemen t.  
 
(5) Water  
 
In principle one should reject water containing organic matter and salty water: these may cause 
efflorescence. Water rich in sulphates may be unfavourable.  
 
8.2.2.3  Types of cement  
Portland cements or cements of a similar class are very suitable. Composite cements can also be used. 
However, suitability tests should be carried out to justify using them. There is no point in using high strength 
cements which give no particular improvement and which are more expensive.  
 
8.2.2.4  Additives  
 
Certain products, added in small quantities to the earth -cement during mixing, can improve certain of its 
properties.   
©RSB 2022  - All rights reserved                  12 
  
(1) Reducing sensitivity to organic matter   
 
Slaked lime, used at 2%, can reduce the deleterious effect of organic matter, as can calciu m chloride (0.3 
to 2 %) which also accelerates the setting of the cement.  
 
(2) Modifying the plasticity of the earth   
 
Slaked lime can also be used to modify the plasticity of the soil and to restrict the formation of nodules.  
 
(3) Rendering the earth wa ter-proof   
 
Bitumens, in emulsion or cut -back, used at 2 % to 4 %, enable mortars to be made impermeable.  
 
8.2.3  Lime stabilisation  
 
8.2.3.1  Types of lime  
 
(1) Non-hydraulic limes  
 
These are produced by calcinating very pure limestone and are the main kinds of lime used in 
stabilisation.  
 
⎯ Quicklime (CaO):  produced directly by calcinating stone containing lime. Its use may be restricted 
because of the careful storage and handling it requires. Quicklime is highly water absorbent and 
must be protected from humidity. It is an aggressive material which must be handled with great 
care: it becomes very hot during the hydration phase (up to 150  °C). Weight for weight, it is more 
efficient th an slaked lime because it contains more calcium ions. When the earth is wet, it can 
absorb the water required for it to be hydrated.  
 
⎯ Slaked lime Ca(OH)2: this is obtained by hydrating (slaking) quicklime. Used in stabilisation, it does 
not have the storage and handling disadvantages of quicklime. Slaked limes should not be too finely 
ground to be effective. Industrial quality slaked limes contain 90 % to 99  % «active lime», whereas 
those of craft production quality can contain as little as 70 % to 75  % with the remainder being inert 
material which is either not calcinated or excessively calcinated. Stabilisation dosages should be 
modified in consequence.  
 
(2) Hydraulic limes  
 
These resemble cements. They should be considered for use only if there are no other qualities of lime 
available. Natural hydraulic limes are more efficient for stabilisation than artificial hydraulic limes which 
are not recommended.  
 
(3) Agricultural limes  
 
These are used to modify agricultural types of earth and generally have no stabilising effect.  
 
(4) Dolomite limes  
 
These are suitable for stabilisation, but they set excessively slowly.  
 
8.2.3.2  Efficacy and dosage  
By adding 1% quicklime to the earth, the exothermic reaction of hydration dries the earth, removing 
approximately 0.5 to 1  % moisture. Adding 2  % to 3 % qu icklime immediately causes a fall in the plasticity of 
the earth and breaks down lumps; this reaction is called the lime fixing point. For ordinary stabilisation using 
slaked lime, dosages of 4 % to 12  % are generally used, equivalent to those used with cement, but it should be 
noted that with lime, there is an optimal quantity for each type of earth.  DRS 514-2: 2022  
13                ©RSB 2022  - All rights reserved  
  
The dosages indicated are relative to dry weight and are determined in laboratory conditions. Measures  for 
checking in the workshop or on site should take account of the specific hygrometric conditions existing locally.  
 
8.2.3.3  Efficacy parameters  
(1) Types of earth  
 
These should contain a reasonable clay fraction. Results vary depending on the nature of the clay 
minerals and are good with those which are high in aluminium silicate, in silica, and in iron hydroxide. 
Natural pozzolanas react quickly and well with lime.  
 
(2) Organic matter  
 
This can prevent ion exchanges in clayey soils, without however, pre venting the pozzolanic reaction.  
 
Types of earth containing up to 20  % organic matter can be stabilised with lime but care must be taken.  
 
(3) Sulphates  
 
When dry, calcium sulphates, which are frequently found, are less deleterious than magnesium sulphates. 
When wet, sulphates are always very deleterious. Sulphates destroy the hardened hydraulic binder matrix 
and increase the sensitivity to humidity of the clays. A specific study for earth containing more than 2 to 
3 % total sulphate cont ent is indispensable.  
 
8.2.3.4  Additives  
Certain additives mixed with lime can produce special effects.  
 
(1) Increasing compressive strength   
 
Portland cement or composite cement with a variable dosage which can be up to 100  % of the lime 
dosage.  
 
(2) Rendering the treated earth water -proof   
 
(a) bituminous products;  
 
(b) other waterproofing agents.  
 
8.2.4  Stabilising using commercial products  
 
Using commercial products other than cement and lime to stabilise the earth with a view to manufacturing earth 
mortars should be examined beforehand by an approved testing laboratory to establish the genuine efficacy of 
the product.  
 
8.3 Recommendations for manufacturing parameters  
Poor execution of any one of the manufacturing stages will considerably lower the quality of the EMs.  
 
8.3.1  Stocking raw materials  
8.3.1.1  Stocking the earth  
 
Earth which has been taken delivery of should be s tocked in such a manner as to avoid any pollution from 
another type of earth or any other material.  
 
The earth should also be protected from accidentally being moistened.  
 
8.3.1.2  Stocking additives  
  
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 Stocking additives should be arranged so that they are  protected from bad weather and so that there is a rapid 
turnover between delivery and use.  
 
8.3.2  Preparing the mix  
At the end of the preparation, the earth should be as dry as possible (water content ≤5  %). No grain or particle 
should have a diameter in  excess of 4 mm and preferably not in excess of 2 mm.  
 
If on completion of the preparation stage, the earth falls outside the recommended zones of texture and 
plasticity, it should be corrected by adding a filler until it comes back within the recommended  zones. If even 
after correction, the mix is still outside the recommended areas, another type of earth will have to be sought or 
the suitability of the mix will have to be specifically examined by an approved laboratory.  
 
8.3.2.1  Screening the earth  
This operation aims to eliminate all components with a diameter in excess of that required. However, these 
components can be made up of aggregates or agglomerates made up of fines which will equally be eliminated, 
whereas they are required to ensure the cohesi on of the final product. It is therefore preferable to break down 
these agglomerates by a pulverisation operation.  
 
8.3.2.2  Pulverising the earth  
This is an important operation and must be carried out with great care. The more finely the clay and the silt  is 
broken down, the more homogeneous the earth will be, and in the event of stabilisation, the more efficient the 
action of the stabiliser. The operation can be a difficult one as clay is highly cohesive. There should not be too 
great a concentration of f ines in agglomerates the size of which should not exceed 4 mm. The presence of 50  
% by weight of agglomerates of fines of 4 mm in size can reduce compressive strength by half. Certain types 
of earth still require screening after pulverisation.  
 
8.3.2.3  Mixing  
The homogeneity of the material depends on the quality of the mixing. It is important to use dry earth to obtain 
best mixing conditions.  
 
In wet regions, this may mean drying out the earth beforehand. Mixing can accelerate the drying proces s and 
help to break down lumps. The water required for mixing should be sprinkled or sprayed in and only at the end 
of the mixing process, after a required phase of dry mixing.  
 
The water should be added gradually until a smooth and homogeneous mix has be en obtained.  
 
Mixing in an additive should be done dry except in the particular case of products requiring wet mixing. Mixing 
should continue until a homogeneous mix has been obtained.  
 
The time needed for manual or mechanised mixing depends on the mixing time required to obtain a perfectly 
homogeneous mix; this can be assessed by its uniform colour, and no streaks should be visible.  
 
8.3.3  Using the EM  
 
8.3.3.1  Retention time of the mix  
The earth mortar should be plastic and smooth and should hold on the trowel. Liquid earth mortars should not 
be used.  
 
Any precautions needed to prevent water evaporation from the EM must be taken in order to maintain the 
plasticity and the smoothness at  the required level.  
 
When the mixing has been with added cement, the EM should be used within half an hour of the beginning of 
the wet mixing stage.  
 
When the mixing has been with added non -hydraulic lime, the EM can be used after several hours.  
 DRS 514-2: 2022  
15                ©RSB 2022  - All rights reserved  
 Any p recautions needed to prevent water evaporation from the mix must be taken in order to maintain the right 
water content of the mix at the required level.  
 
8.4 Checking procedures  
 
8.4.1  Raw materials  
8.4.1.1  Earth  
 
Conditions for taking delivery of earth supplies  shall be in accordance with Clause 8.5 of this Standard . 
 
8.4.1.2  Stabilising additives  
(1) Procedure   
 
(a) for cements, tests on samples of standard cement mortar;  
 
(b) for lime, chemical composition tests.  
 
(2) Frequency: at each delivery.  
 
8.4.1.3  Water  
(1) Procedure: in the case of a manufacturing process with stabilisation using an additive with a 
physicochemical effect (Portland cement, lime), analysis of the content of salts and of the pH value.  
 
(2) Frequency: once during the «running i n» period, then annually.  
 
8.4.2  Preparing the earth  
(1) Procedure: wet screening of the prepared earth and calculation of the percentage by weight of grains 
the diameter of which is in excess of 4 mm.  
 
(2) Frequency: weekly during the start -up period, less frequently once production is established.  
 
8.4.3  Mixing  
 
8.4.3.1  Earth and additive dosage  
(1) Procedure: weighing and measuring volume directly or calculating consumption periodically (e.g. the 
number sacks of stabiliser consumed per number of batches produced).  
 
(2) Frequency: frequently and without warning.  
 
8.4.3.2  Mix 
(1) Procedure:  
 
(a) visual examination of the homogeneity of the mix;  
 
(b) timing the average mixing time.  
 
(2) Frequency: weekly or more.  
 
8.4.4  Waiting time before use  
(1) Procedure: timing the average waiting time.  
 
(2) Frequency: weekly or more.  
 
8.4.5 Curing  
(1) Procedure: visual examination (shrinkage cracks, surface drying out);  
 
(2) Frequency: weekly   
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8.5 Conditions for taking delivery of earth supplies  
 
8.5.1  General  
 
8.5.1.1  Types of check on taking delivery  
There are two types of check on taking delivery:  
 
(a) a simple check, which relates solely to the comparative examination of the appearance, the simplified 
sedimentation test and the sand equivalent test of t he earth supplied compared with the values recorded 
in the reference earth selected when ordering;  
 
(b) a complete check, which relates to measuring texture and plasticity and the presence of organic matter 
and sulphates with the values of the sample of refer ence earth.  
 
8.5.1.2  Choosing the type of check on taking delivery  
The buyer is free to choose the type of check on taking delivery.  
 
If the buyer requires that a complete check should be carried out, it is preferable for him to inform the supplier 
of this in writing on the order document.  
 
Carrying out laboratory tests intended to check product conformity to reference values normally r equires a 
minimum of two weeks.  
 
8.5.1.3  Date and place of taking delivery  
Taking delivery occurs at the moment the buyer assumes responsibility for the products, i.e. either at the supplier 
location or at the delivery location.  
 
If it takes place at the  supplier location, the date should be mutually agreed. The buyer should be present or 
represented.  
 
If it takes place at the delivery location, the date should be indicated to the supplier who has the right to be 
present at the operations relating to tak ing delivery, or to be represented there by a person attending on his 
behalf.  
 
Unless specifically stated, taking delivery can occur at the delivery location only if the supplier is responsible for 
the transport.  
 
8.5.2  Taking delivery on site  
As soon as  the earth has been unloaded and before any subsequent handling in the brickworks, the buyer 
should proceed with an overall examination of the appearance of the earth.  
 
If this examination shows that the earth delivered is not homogeneous in nature, after  due hearing of the parties, 
one may proceed, at the supplier's expense, to sort it with a view to separating the a priori  acceptable types of 
earth from the rest of the delivery.  
 
If the earth is homogeneous in nature, one should proceed with the operati ons for taking delivery properly 
speaking.  
 
8.5.3  Simple check on taking delivery  
 
8.5.3.1  Samples  
For each delivery, take a sample at random and from below the surface of four buckets of earth at four points 
from the bottom of the pile and two buckets from the upper part of the pile.  
 
Having carried out the simple sedimentation test examination of appearance and that of sand equivalent, these 
products should be returned to the delivery.  DRS 514-2: 2022  
17                ©RSB 2022  - All rights reserved  
  
8.5.3.2  Conditions of acceptability  
If the results of the examination give values corresponding to the reference values, the delivery should be 
accepted.  
 
8.5.4  Complete check on taking delivery  
 
8.5.4.1 Examination of appearance  
The complete check on taking delivery includes, first, examining appearance as defined above.  
Complete checks on taking del ivery are carried out in the manner described below.  
 
8.5.4.2  Samples from the lots   
 
8.5.4.2.1 Deliveries of up to or equal to 7 tonnes or 5 m3 
No sample is taken if the delivery is up to or equal to 7 tonnes or 5 m3 in volume. Consequently, visual 
exami nation is sufficient.  
 
8.5.4.2.2 Deliveries of over 7 tonnes or 5 m3 
Split the delivery into lots of maximum 7 tonnes or 5 m3.  
 
8.5.4.2.3 Particular case of supply occurring on several sites  
When delivery is taken on the supplier location, split the comp lete supply into lots of maximum 21 tonnes or 15 
m3.  
 
When delivery is taken on site where it is common to several sites, the reference site is selected by the 
entrepreneur, who advises the supplier of this in writing.  
 
8.5.4.2.4 Samples  
The samples must  be taken on the basis of a sampling process the procedure for which is defined by the 
standards for testing.  
 
8.5.4.3  Conditions of acceptability  
If, for each of the tests carried out, the results conform to the reference values, the delivery should be accepted.  
 
If this is not the case, one may proceed with a counter -expertise for the test which failed to give satisfaction.  
 
If the results of the counter -expertise are still unfavourable, the delivery can be refused. If the result is 
favourable, the whole delivery should be accepted.  
 
8.5.4.4  Choice of laboratory  
 
Tests are carried out on site, in a workshop or in a laboratory  selected by mutual agreement between the 
supplier and the buyer.  
 
8.5.4.5  Costs of taking delivery  
The costs of taking delivery are borne by the buyer if the conditions of acceptability are satisfactory and borne 
by the supplier if they are not.  
 
8.5.5  Particular case  
The preceding arrangements do not preclude, by mutual consent, the buyer and the supplier proceeding with 
partial checks, relating only to certain reference values.  
  
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 Bibliography  
[1] Compressed earth blocks. Vol. II. Manual of design and c onstruction. CRATerre -EAG: Guillaud H., Joffroy 
T., Odul P. Aus der Arbeit von GATE, Friedrich Vieweg & Sohn, Braunschweig/Wiesbaden, Germany, 1995.  
 DRS 514-2: 2022  
 
Price based on  17 pages  
©RSB 2022  - All rights reserved