KENYA STANDARD      DKS 2802-3:2019 
ICS  
  
 
 
 
 
 
 
 
 
 
 
 
 
Masonry units — Methods of test  
 
Part 3: 
 
Determination of the active soluble salts content of 
clay masonry units 
 
Public Review Draft April 2019 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
© KEBS 2019 First Edition, 2019 
 
 DKS 2802-3:2019  
ii  © KEBS 2019 — All rights reserved   KENYA STANDARD                                         DKS 2802-3:2019 
ICS  
© KEBS 2019 — All rights reserved   iii TECHNICAL COMMITTEE REPRESENTATION 
 
The following organizations were represented on the Technical Committee:  
 
National Housing Corporation 
Kenya Clay Products Ltd 
Coast Clay Works Ltd 
Consumer Information Network 
University of Nairobi  
Kenya Industrial Research & Development Institute 
Architectural Association of Kenya 
M&O Consulting Engineers 
Kenya Association of Manufacturers, 
Kenya National Federation of Jua Kali Association 
Lake Basin Development Authority 
Kenya Bureau of Standards — Secretariat 
 
 
 
 
REVISION OF KENYA STANDARDS 
 
In order to keep abreast of progress in industry, Kenya Standards shall be regularly reviewed. Suggestions for 
improvements to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are 
welcome. 
 
 
 
 
© Kenya Bureau of Standards, 2017 
 
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 130 of 2001 of the Laws of Kenya, copyright subsists 
in all Kenya Standards and except as provided under Section 25 of this Act, no Kenya Standard produced by Kenya Bureau of Standards 
may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from the 
Managing Director.  
  DKS 2802-3:2019  
iv  © KEBS 2019 — All rights reserved  
 
 
 
 
 
 
 
 
 
 
 
 
Masonry units — Methods of test  
 
Part 3: 
 
Determination of the active soluble salts content of clay 
masonry units  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
KENYA BUREAU OF STANDARDS (KEBS) 
 
Head Office: P.O. Box 54974, Nairobi-00200, Tel.: (+254 020) 605490, 602350, Fax: (+254 020) 604031 
E-Mail: info@kebs.org, Web:http://www.kebs.org  
 
Coast Region    Lake Region    Rift Valley Region  
P.O. Box 99376, Mombasa-80100  P.O. Box 2949, Kisumu-40100   P.O. Box 2138, Nakuru-20100 
Tel.: (+254 041) 229563, 230939/40 Tel.: (+254 057) 23549, 22396   Tel.: (+254 051) 210553, 210555  
Fax: (+254 041) 229448   Fax: (+254 057) 21814 
 
Foreword KENYA STANDARD                                         DKS 2802-3:2019 
ICS  
© KEBS 2019 — All rights reserved   v  
This Kenya Standard was prepared by the Clay and Clay Products Technical Committee under the guidance 
of the Standards Projects Committee and in accordance with the procedures of the Kenya Bureau of 
Standards. 
 
During the development of this standard, reference was made to the following documents: 
 
BS EN 772-5:2016 Methods of test for masonry units - Part 1: Determination of the active soluble salts 
content of clay masonry units. 
 
Acknowledgement is hereby made for the assistance received from these sources. 
  
KENYA STANDARD        DKS 2802-3:2019 
 
 
© KEBS 2019 — All rights reserved   1  
Masonry units — Methods of test  
 
Part 3: 
 
Determination of the active soluble salts content of clay masonry units  
 
 
1. Scope  
 
This Kenyan Standard specifies a method for determining the active soluble salts content of clay masonry 
units 
 
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, the latest edition of the referenced document 
(including any amendments) applies. 
 
DKS 2801 -1, Specification for masonry units - Part 1: Clay masonry units 
 
ISO 3310-1, Test sieves - Technical requirements and testing - Part 1: Test sieves of metal wire cloth 
 
ISO 3310-2, Test sieves - Technical requirements and testing - Part 2: Test sieves of perforated metal plate 
 
3. Principle 
 
The method adopted is based on water extraction from a crushed representative sample of the clay masonry 
units, and determines the amounts of soluble magnesium, sodium and potassium ions, released under the test 
conditions, which may be correlated with the potentially damaging effect of salts of those ions on cementitious 
mortars in certain circumstances, or even on the units themselves. These salts are known as «active» soluble 
salts in DKS 2801 -1. 
 
 
4. Symbols 
 
MMg   is the number of milligrams of Mg equivalent to 1 ml of EDTA  
 
x,y    is the volume of EDTA titrated, en millilitres (ml)  
 
C1    is the lower reference sample concentration, in percentage (%)  
 
C2    is the higher reference sample, concentration, in percentage (%)  
 
Cx    is the sample concentration, in percentage (%)  
 
E1    is the measured signal for the lower reference sample concentration C1 
 
E2    is the measured signal for the higher reference sample, concentration C2 
 
Ex    is the measured signal for sample  
 
d    is the dilution factor 
5. Materials  
2  © KEBS 2019 — All rights reserved  
5.1. For all methods 
 
Distilled or deionized water for extraction of active soluble salts from the sample, and for preparation of 
analytical test solutions. 
 
Hydrochloric acid (relative density 1,18). 
 
All chemicals shall be of analytical reagent grade.  
 
5.2. Instrumental method Atomic Absorption Spectroscopy (AAS)and flame 
photometry 
 
Hydrated Lanthanum chloride   LaCL 3 · 7H20, 210 g/l Solution 
 
Caesium Chloride        CsCl, 63 g/l Solution 
                             
5.3. Instrumental method Atomic Absorption Spectroscopy (AAS)and flame 
photometry or inductively coupled plasma spectrometry (ICP) 
 
High purity standard solutions 
 
5.4. EDTA method (alternative) 
 
Magnesium metal 
 
Ethylenediamine tetra acetic acid (EDTA) Indicators:  Calcein 
 
                       Methyl thymol blue complexone  
 
Potassium hydroxide 
 
Ammonia solution (relative density 0,88)  
 
Potassium nitrate 
 
6. Apparatus 
 
6.1. Test sieves,  complying with the requirements of ISO 3310-1, ISO 3310-2 
6.2. Mortar  or other suitable grinding equipment capable of producing particles to pass a 150 µm test  
sieve. 
6.3. Polyethylene bottle or Conical flask , typically with a capacity 500 ml 
6.4.  Weighing instrument,  readable to the nearest 0,1 mg 
6.5. Burette , typically 10 ml 
6.6. Pipette,  typically 10 ml, 50 ml 
6.7. Graduated flask,  typically 1 l 
6.8. Volumetric flask , typically 100 ml 
6.9. One dimensional horizontal shaking equipment,  capable of oscillating at (120 ± 5) min-1 having a 
horizontal movement of 20 mm, or a rotary shaker capable of revolving at 30 ± 3 revolutions per 
minute. 
6.10. Polyethylene bottle,  typically with a capacity of between 1 l and 1,5 l. DKS 2802-3:2019  
© KEBS 2019 — All rights reserved   3 6.11. Ventilated oven , capable of maintaining a temperature of (105 ± 5) °C  
7. Preparation of sample 
 
7.1. Sampling 
 
The method of sampling shall be in accordance with DKS 2801-1. The minimum number of specimens for the 
determination of the active soluble salts content shall be six and shall comprise whole units but a larger number 
may be specified in the product specification, in which case that larger number shall be used. The specimens 
shall be sampled in such a manner that they have not been exposed to water that would lead to leaching of 
soluble salts from the units. 
 
From the bulk sample of units a representative sample of 50 g to 250 g of material, ground to pass a 
150 µm test sieve (6.1), is prepared, using the crushing method described in 7.2. 
 
7.2. Crushing 
 
Crush each unit to give lumps not greater than 10 mm. Obtain from each crushed specimen a representative 
subsample of at least 50 g, either by coning and quartering or using a suitable mechanical sampling device. 
Mix this material and crush it to give particles not greater than approximately 1 mm. Reduce the prepared 
sample to 50 g to 250 g using the same splitting method. 
 
Dry the crushed sample to constant mass in a ventilated oven at a temperature of (105 ± 5) 0C. Before 
weighing, the sample shall be cooled to room temperature in a dessicator. 
 
Constant mass is achieved, when the loss in mass between two successive determinations conducted at an 
interval of 24 h during the drying, process does not exceed 0,2 % of the total mass. 
 
Finally grind the complete sample such that 95 % will pass a 150 µm test sieve (6.1) complying with 
ISO 3310-1 or ISO 3310-2, using a mortar (6.2) or other suitable grinding equipment. 
 
8. Extraction procedure 
 
Weigh 20 g ± 0,05 g of the sample and transfer it to a 500 ml polyethylene bottle, or a 500 ml conical flask 
(6.3) when using horizontal shaking equipment (6.9). 
 
Add 200 ml of distilled or deionised water at room temperature, close the bottle with a screw-on polyethylene 
top and shake the bottle for 60 min ± 2 min, using a one dimensional horizontal shaking equipment at (120 ± 
5) min-1 with a horizontal movement of 20 mm, or a rotary shaker (6.9) revolving at 30 min-1 ± 3 min-1. 
 
Within 15 min ± 1 min of completing the extraction filter the suspended sample using an ashless blue ribbon 
filter paper or equivalent and collect the filtrate in a clean dry flask (6.10). Do not wash the residue on the filter. 
Alternatively use a centrifuge. It is essential that the filtrate shall be clear. 
 
9. Determinations of cations by instrumental techniques 
 
9.1. General 
 
Determine the metal ion content using an established method, e.g. inductively coupled plasma spectrometry, 
atomic absorption spectroscopy, or flame photometry. Alternatively determine and calculate the magnesium 
content following the procedure described in Clause 10. 
 
9.2. Atomic absorption spectroscopy method (AAS) and flame photometry 
 
9.2.1. Sample preparation 
  
4  © KEBS 2019 — All rights reserved Pipette (6.6) a 50 ml aliquot of the soluble salts extract into a 100 ml volumetric flask (6.8) add 4 ml of 
hydrochloric acid (1 + 1 volume) and 4 ml of lanthanum chloride. If Na and K are to be measured by AAS, add 
4 ml of caesium chloride. Fill to the mark with water and mix.  
 
9.2.2. Calibration: preparation of the reference series 
 
Either: 
 
a) use dilutions of commercially available standard solutions, magnesium 1000 µg/ml, potassium 
1000 µg/ml, sodium 1000 µg/ml or, 
 
b) use a multi-element solution for example: 
 
1) weigh the following substances up to nearest 0,1 mg; 
2) 1 000 mg magnesium metal; 
3) 1 767,3 mg potassium carbonate K 2CO3 dried to 105 °C ± 5 °C; 
4) 2 305,1 mg sodium carbonate Na 2C03 dried to 105 °C ± 5 °C; 
5) add 50 ml of hydrochloric acid (1+1 volume) wait till the reaction is completed and warm up carefully 
on a heating plate until complete dissolution; complete to the mark in a 1 000 ml graduated flask 
(6.7). 
 
All chemicals shall be of analytical reagent grade. 
 
Then prepare a series of reference solutions as suggested in Table 1. 
 
Table 1 - Suggested reference solution series 
Solution  Volume of standard 
solutions or multi- 
element solution 
each other diluted 
1/10 Add Hydrochloric 
acid (1 + 1 volume) 
and Lanthanum 
chloride and 
Caesium chloridea Fill to 100 ml 
with water 
and mix Concentration  in 
Mg,K, Na% of the 
mass of the 
original sample 
0 0 ml  
4 ml each  0 
1 1 ml 0,002 
2 2 ml 0,004 
3  5 ml 0,010 
4 10 ml 0,020 
5 15 ml 0,030 
NOTE: If the concentration is higher than 0,03 % pipette (6.6) a low aliquot of the solution salts extract and 
multiply by dilution factor d (e.g. aliquot 25 ml, dilution factor d = 2). 
40.  
a  Only in case where Na, K are measured by AAS. 
 
 
 
 
 
 
 
 
9.2.3. Spectroscopic lines and parameters for AAS and flame photometry 
analysis 
 DKS 2802-3:2019  
© KEBS 2019 — All rights reserved   5 The data to be used for the analysis may be as given in Table 2. 
 
Table 2 - Suggested spectroscopic lines and parameters for AAS and flame photometry analysis 
Type analysis        Element  nm Type of flame  
AAS Mg 285,2 air /acetylene 
flame emission or AAS K 766,5 air /acetylene 
flame emission or AAS Na 589,0 air /acetylene 
 
9.3. Inductively coupled plasma spectrometry method (ICP) 
 
9.3.1. General 
 
The sample preparation (see 9.2.1) and the preparation of reference series (see 9.2.2) shall be as that for the 
atomic absorption spectroscopy method, but without any addition of lanthanum chloride or caesium chloride. 
 
9.3.2. Spectroscopic lines for ICP analysis 
 
The data to be used for the analysis can be as given in Table 3. 
 
Table 3 - Suggested spectroscopic lines for ICP analysis 
Element  nm 
Mg 279,553 
 
285,213 
K 766,491 
 
769,900 
Na 588,995 
 
589,592 
 
 
9.4. Calculation of the results 
 
Construct calibration on the basis of measurements taking into account the directions given by the instrument 
manufacturers. 
 
For example: 
 
E1   measured signal for the lower reference sample concentration C 1 
 
E2   measured signal for the higher reference sample, concentration C 2 
 
Ex   measured signal for sample 
 
 𝐶𝑥 𝑠𝑎𝑚𝑝𝑙𝑒=𝐶ଵ+(𝐶ଶ− 𝐶ଵ)(𝐸௑− 𝐸ଵ) 
(𝐸ଶ− 𝐸ଵ)  .𝑑 
 
 
 
 
where 
C1   is the lower reference sample concentration, in percentage (%)  
6  © KEBS 2019 — All rights reserved C2   is the higher reference sample, concentration, in percentage (%)  
Cx   is the sample concentration, in percentage (%) 
E1   is the measured signal for the lower reference sample concentration C 1 
 
E2   is the measured signal for the higher reference sample, concentration C 2 
 
Ex   is the measured signal for sample 
 
d   is the dilution factor 
 
If the concentration of the sample is, greater than 0,001 % then subtract the concentration value found for the 
blank solution from the calculated concentration of the sample.  
 
 
10. Alternative method of determination of the content of active soluble salts 
 
10.1. Preparations of reagents for magnesium determination 
 
10.1.1. Magnesium test solution (1,0 mg Mg/ml) 
 
Dissolve 1,000 g of magnesium metal in a slight excess of hydrochloric acid solution consisting of one part 
hydrochloric acid (relative density 1,18) to three parts distilled or deionized water, and dilute to 1 l  with distilled 
or deionized water in the graduated flask (6.7). Before weighing, etch the metal ribbon or foil in diluted 
hydrochloric acid, wash it with water and then dry it with alcohol followed by ether. Adjust the mass with 
scissors. 
 
10.1.2. Preparation of EDTA test solution (0,5 %) 
 
Dissolve 5 g of ethylenediamine tetra acetic acid (EDTA) (disodium salt, dihydrated) in warm distilled or 
deionized water, filter if necessary, cool and dilute it to 1 l. Store in a polyethylene bottle (6.10). Standardize 
against the magnesium test solution described in 10.1.1 using methyl thymol blue complexone, where MMg is 
the number of milligrams of Mg equivalent to 1 ml of EDTA 
 
10.2. First titration (calcium plus magnesium) 
 
Pipette (6.6) a 10 ml aliquot of the soluble salts extract into a 500 ml conical flask. Add 20 drops of hydrochloric 
acid (relative density 1,18), followed by 10 ml of ammonia solution (relative density 0,88) and dilute with distilled 
or deionized water to about 200 ml. Add about 0,04 g of methyl blue complexone indicator, prepared by 
grinding together 0,2 g of methyl thymol blue complexone with 20 g of potassium nitrate. Titrate with EDTA 
test solution, prepared as described in 10.1.2 from a 10 ml burette (6.5), the colour change being from blue to 
colourless. Measure the volume titrated, where the volume of EDTA used in the titration is denoted by x. 
 
10.3. Second titration (calcium) 
 
Pipette (6.6) a 10 ml aliquot of the soluble salts extract a 500 ml conical flask. Add 20 drops of hydrochloric 
acid (relative density 1,18), followed by 10 ml of potassium hydroxide solution (approximately 250 g/l), and 
dilute to about 200 ml with distilled or deionized water. Add about 0,015 g of calcein indicator prepared by 
grinding together 0, 1 g of calcein with 10 g of potassium chloride. Titrate with EDTA test solution, prepared 
as described in 10.1.2 from a 10 ml burette (6.5), the colour change being from fluorescent green to pink. 
Measure the volume titrated, where the volume of EDTA used in the titration is denoted by x. 
 
 
 
10.4. Magnesium content 
 
Calculate the mass of water soluble magnesium as a percentage of the mass of the original sample from the 
formula: DKS 2802-3:2019  
© KEBS 2019 — All rights reserved   7  
𝑀𝑔=(y− x) 𝑀௠௚
10   𝑖𝑛 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒  % 
 
Where y is the volume of the EDTA used in the titration described in 10.2 and  x is the volume of EDTA 
described in 10.3. 
 
10.5. Determination of sodium and potassium 
 
Compare a portion of the soluble salts extract with test solutions containing 5 µg/ml by mass of sodium and 10 
µg/ml by mass of potassium in a flame photometer or by atomic absorption spectroscopy. Calculate the sodium 
and potassium contents by reference to previously prepared calibration graphs. 
 
11. Expression of results 
 
Report the sum of sodium and potassium contents to the nearest 0,01 % and the magnesium to the nearest 
0,01 %. 
 
12. Test report 
 
The test report shall contain the following information: 
 
a) the name, title and date of issue of this European Standard; 
b) the name of the organization that carried out the sampling and the method used; 
c) the date of testing; 
d)  the type, origin and designation of the masonry unit by reference to DKS 2801-1; 
e) the date of delivery of the specimens; 
f)  the number of specimens in the sample; 
g) the method of analysis, detailing whether chemical or alternative instrumental methods were used; 
h) the active soluble salts content of the sample, expressed as a percentage to the nearest 0,001 % for 
the ions of magnesium, sodium, and potassium; 
i) express the sum of sodium and potassium contents to the nearest 0,01 % and the magnesium to the 
nearest 0,01 %; 
j) Remarks, if any.