KENYA STANDARD DKS2802-7:2018
ICS
Masonry units —Methods of test
Part 7:
Determination of net and gross d ry density of
masonry units (except for natural stone)
© KEBS 201 8 First Edition ,2018DKS2802-7:2018
ii ©KEBS 201 8—All rights reservedTECHNICAL COMMITTEE REPRES ENTATION
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 Nairo bi
Kenya Industrial Research & Development Institute
Architectural Association of Kenya
M&O Consulting Engineers
Kenya Association of Manufacturers,
Miritini Building Products Ltd .
Kenya National Federation of Jua Kali Association
Kenya Bureau of Standards —Secretariat
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© Kenya Bureau of Standards, 201 7
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 130 of 2001  of the Laws of Kenya, copy right subsists
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Managing Director.KENYA STANDARD DKS2802-7:2018
ICS
© KEBS 201 8—All rights reserved iiiMasonry units —Methods of test
Part 7:
Determination of net and gross dry density of masonry
units (except for natural stone)
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
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Tel.: (+254  041) 229563, 230939/40 Tel.: (+254 057) 23549, 22396 Tel.: (+254 051) 210553, 210555
Fax: (+254  041) 229448 Fax: (+254 057) 21814DKS2802-7:2018
iv ©KEBS 201 8—All rights reservedForeword
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:
EN 772 -13, Methods of test for masonry units —Part 13: Determination of net and gross dry density of masonry
units (except for natural stone).
Acknowledgement is hereby made for the assistance received from these sources .KENYA STANDARD DKS2802-7:2018
© KEBS 201 8—All rights reserved 1Masonry units —Methods of test
Part 7:
Determination of net and gross dry density of masonry units (except for
natural stone)
1 Scope
This Kenya Standard specifies a method of determining the net and gross dry density of masonry units (except
for natural stone 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) a pplies.
DKS 2801 :1 Masonry Units —Specification —Part 1: Clay Masonry Units. .
DKS 2802 :2 Masonry units —Test Methods —Part 2: Determination of net volume and percentage of voids
of clay masonry units by hydrostatic weighing.
DKS 2802 :5 Masonry units —Test Methods —Part 5: Determination of volume and percentage of voids and
net volume of clay and calcium silicate masonr y units by sand filling.
DKS 2802 :8 Masonry units —Test Methods —Part 8: Determination of dimensions.
3 Principle
After drying to constant mass and calculating the net and gross volume, the net and gross dry density of the
masonry units are calculated.
4. Definitions
4.1
gross dry density
the mass per unit gross volume after drying t o constant mass
4.1.2
gross volume
the volume  of the unit derived  from  the length, width and  height with a deduction of the volume of
perforations, voids, recesses or indenta tions intended to be filled with mortar
4.1.3
net dry density
the mass per unit net volum e after drying to constant mass
4.1.4
net volume2 ©KEBS 201 8—All rights reservedthe gross volume of the unit less the volume of any perforations or voids not intended to be filled with mortar.
5 Symbols
lu is the unit length, (mm)
Wu is the unit width, (mm)
hu is the unit height, (mm)
mo,u is the mass of a whole unit specimen prior to drying, (g)
mo,p,tot is the combined mass of a group of three representative portions of a whole unit specimen prior to
drying, (g)
mdry,p is the mass of one individual representative  portion of the three portions of a whole unit specimen
after drying to constant mass, (g)
mdry,p,tot isthecombined mass  of a group of three representative portions of a whole unit specimen after
drying to constant mass, (g)
mdry,u isthe mass of a whole unit specimen  (or corresponding  whole unit where representative portions
have been taken) after drying to constant mass, (g)
wp is the moisture content of a group of three representative portions of a whole unit specimen
vn,u isthe net volume of unit, (mm3)
vg,u is the gross volume of unit, (mm3)
vg,p is the gross volume of parts of unit, (mm3)
ρn,u is the net dry density, (kg/m3)
ρn,p is  the net dry density of parts of unit, (kg/m3)
ρg,u is the gross dry density, (kg/m3)
6 Materials
6.1 Ventilated oven ,capable of maintaining a temperature of  105 °C ± 5 ° C for  use with clay, calcium
silicate and autoclaved aerated concrete units.
6.2 Ventilated oven ,capable of maintaining a temperature of 70 ° C ± 5 ° C for use with aggregate
concrete and manufactured stone units.
6.3 Weighing instrument ,capable of weighing the whole unit or portions of it to an accuracy of 0, 1 % of
their mass.
7 Sampling
The me thod of sampling shall be in accordance with the relevant part of DKS 2801 :1. The minimum number
of specimen s shall be six, but a larger minimum number may be specified inthe product specification, in which
case that larger number shall be used.
8 procedure
8.1 Determination of dry mass
8.1.1 Whole unit specimensCD/ENG/16 -7:2017
© KEBS 201 8—All rights reserved 3Dry the test specimens to constant mass mdry,uin a ventilated oven at a temperature  of 70 ° C ± 5  ° C (6.2)
for aggregate concrete and manufacture d stone masonry  units or 105 °C ± 5 ° C(6.1) for clay, ca lcium  silicate
and autoclaved aerated concrete masonry units. Constant mass is reached, if during the drying process in two
subsequent weighings with a 24 h interval, the loss in mass between the two determinations is not more than
0.2% of the total mass. Record the mass mdry,u.
8.1.2 Portions of whole unit specimens
Where representative portions are used, first weigh each whole unit specimen and record the mass
(mo,u).·Then obtain three representative  s olid portions,  i.e. containing no enclosed or exposed formed voids,
of at least 100 g from each whole unit specimen and weigh each group of three together. Record the mass of
each group ( mo,p,tot).
Dry each group of three portions to constant mass following the procedure of 8.1.1 above. Record the mass
of each group (m dry,p,tot ).
Calculate the moisture content of each group of three portions using equation (1):
=,, ,,
,,……………eqn (1)
Calculate the corresponding dry mass of the whole unit ( mdry,u) using equation (2):
,=,………………………..eqn (2)
8.2 Net dry density
8.2.1 Whole units
Determine the net volume using one of the following methods as appropriate;
a)For clay masonry units, by weighing in water as indicated in DKS 2802:2 .
b)For calcium silicate masonry units, by using sand filling as indicated in DKS 2802: 5.
c)For  manufactured   stone  and  solid  aggregate concrete masonry  units, by subtracting  the volume
of all recesses  or indentations,  determined  using a suitable measuring  device, from the volume
(length x width x height )  deter mined  in accordance  with DKS 2802: 8. Express the net volume Vn,uto
the nearest  104mm3.
d)For aggregate concrete masonry units with formed voids, by the method of c) above, but in addition
subtracting the volume of all voids. Express the net volume Vn,uto the nearest 104mm3.
Determine the net dry density of the masonry unit (ρ n,u) using equ ation (3);
,=,10()………………….eqn (3)
Calculate thenetdrydensity ofeach whole  unit specimen tothenearest 5kg/m' fordensities upto
1000kg/m3andtothenearest 10kg/m3fordensities over 1000kg/m3.Calculate themean ofthenet
drydensities ofthespecimens.
8.2.2 Representative portions of whole unit specimens
8.2.2.1 Determine the net dry density of the parts as follows:
8.2.2.2 Determine the dry mass of each portion of the whole unit specimen mdry,pby drying according to 8.1.2;
4 ©KEBS 201 8—All rights reserved8.2.2.3 Determine the volume of the parts Vg,pby measuring length, width  and height  to the nearest 1 mm;
8.2.2.4 Calculate the net dry density ρn,pto the nearest 5 kg/m3using equation (4):
,=,
,10()……………….eqn (4)
Define the net dry density of each whole unit specimen (from which the portions were obtained) as the mean
value of the net dry density of the three repres entative portions.  Express the net dry density  of the  whole
unit  specimens  to the nearest  5 kg/m3for densities  up to  1000 kg/m3and to the  nearest 10 kg/m3for
densities over  1000 kg/m3.  Calculate the mean of the net dry densities of the whol e unit specimens.
8.3 Gross dry density
Calculate  the gross volume Vg,uof the unit  from the unit  dimensions  length, width  and height  (CD/ENG/16 -
8:2017) with a subtraction  of the volume  of perforations,  voids, recesses  or indentations  intended to be
filled with mortar determined by measurement by any suitable metho d with the same accuracy of measurement
as incorporated  in DKS 2802: 8.
To find the gross dry density of the unit (ρ g,u) [see equation (5)], divide the dry mass ( mdry,u) obtained according
to 8.1 by the gross volume ( Vg,u) of the unit:
,=,
,10()……………eqn (5)
Express the gross dry density of each whole unit specimen to the nearest 5 kg/m3for densities  up to 1000
kg/m3and to the nearest  10 kg/m3for densities  over  1000 kg/m3.  Calculate the mean of the gross dry
densities of the specimens.
9 Test report
The test report shall contain the following information:
a)the number, title and date of issue of this Kenyan Standard;
b)the number, title and date of issue of this European  Standard;
c)a description of the masonry unit to the relevant part of DKS 280 1:1.
d)the method of sampling and by which organization;
e)date of receipt of the specimens by the test laboratory;
f)the date of testing the specimens;
g)the  number  of  specimens  in  sample  and whether  the se  are whole  units  or representative
portions thereof;
h)the individual and mean values of net dry density;
i)the individual and mean values of gross dry density; and
j)remarks, if any.