UGANDA STANDARD  
  DUS 2032  
First  Edition  
2018 -09-10 
 
 
 Reference number  
DUS 2032 : 2018 
© UNBS 2018   
  
Concrete hollow b lock — Specification  
 DUS 2032 : 2018  
ii © UNBS 2018  – All rights reserved  
 Compliance with this standard does not, of itself confer immunity from legal obligations  
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct a pplication  
© UNBS yyyy  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, including photocopying and microfilm, without prior written 
permission  from UNBS.  
Requests for permission to reproduce this document should be addressed to  
The Executive Director  
Uganda National Bureau of Standards  
P.O. Box 6329  
Kampala  
Uganda  
Tel: +256 41 4 333 2 50/1/2/3  
Fax: +256 41 4 286 123  
E-mail: info@unbs.go.ug  
Web: www.unbs.go.ug  DUS 2032 : 2018  
© UNBS 2018  – All rights reserved  iii 
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ............................  iv 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Specifica tion, types, grades and marks  ................................ ................................ ..............................  2 
4.1 Specification  ................................ ................................ ................................ ................................ ..........  2 
4.2 Category  ................................ ................................ ................................ ................................ .................  3 
4.3 Classification  ................................ ................................ ................................ ................................ .........  3 
4.4 Mark  ................................ ................................ ................................ ................................ ........................  4 
5 Raw material  ................................ ................................ ................................ ................................ ..........  4 
5.1 Cement  ................................ ................................ ................................ ................................ ...................  4 
5.2 Aggregate  ................................ ................................ ................................ ................................ ...............  4 
5.2.1  Fine aggregates  ................................ ................................ ................................ ................................ ..... 4 
5.2.2  The coarse aggreg ates,  ................................ ................................ ................................ ........................  4 
5.3 Fly ash  ................................ ................................ ................................ ................................ ....................  4 
5.4 Granulated blast -furnace slag powder  ................................ ................................ ................................  4 
5.5 Water  ................................ ................................ ................................ ................................ .......................  4 
5.6 Admixtures  ................................ ................................ ................................ ................................ .............  4 
5.7 Other materials  ................................ ................................ ................................ ................................ ...... 4 
6 Technical requirements  ................................ ................................ ................................ ........................  5 
6.1 Dimension deviation  ................................ ................................ ................................ .............................  5 
6.2 Appearance quality  ................................ ................................ ................................ ...............................  5 
6.3 Hollow rate  ................................ ................................ ................................ ................................ .............  5 
6.4 External wall and rib thickness  ................................ ................................ ................................ ............  5 
6.5 Strength grade  ................................ ................................ ................................ ................................ ....... 5 
6.6 Water absorption  ................................ ................................ ................................ ................................ ... 6 
6.7 The linear dryness shrinkage  ................................ ................................ ................................ ...............  6 
6.8 Frost resistance  ................................ ................................ ................................ ................................ ..... 6 
6.9 Carbonization coefficient  ................................ ................................ ................................ .....................  6 
6.10  Softening coefficient  ................................ ................................ ................................ .............................  6 
6.11  The radionuclide limitations  ................................ ................................ ................................ .................  6 
7 Test method  ................................ ................................ ................................ ................................ ...........  7 
8 Inspection rules  ................................ ................................ ................................ ................................ ..... 7 
8.1 Classification of insp ection  ................................ ................................ ................................ ..................  7 
8.2 Batching rules  ................................ ................................ ................................ ................................ ........  7 
8.3 Sampling  ................................ ................................ ................................ ................................ ................  7 
8.4 Acceptance rule s ................................ ................................ ................................ ................................ ... 8 
9 Product certificate, stacking and transport  ................................ ................................ ........................  8 
Bibliography  ................................ ................................ ................................ ................................ ........................  9 
 DUS 2032 : 2018  
iv © UNBS 2018  – All rights reserved  
 Foreword  
Uganda National Bur eau of Standards (UNBS) is a parastatal under the Ministry of Trade , Industry and 
Cooperatives established under Cap 327 , of the Laws of Uganda , as amended .  UNBS is mandated to co -
ordinate the elaboration of standards and is  
(a) a member of International Org anisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT  Agreement  of the World Trade Organisation (WTO).  
The work of preparing Uganda Standards is carr ied out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a given field or area and consists of key stakeholders 
including government, academia, consumer groups, private sector and other interested parties.  
Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
The committee responsible for this document is Technical Committee UNBS /TC ###, [name of committee] , 
Subcommittee SC ##, [name of subcommittee] . 
This second/third/… edition cancels and replaces the first/second/… edition (US nnn-n:yyyy), which has been 
technically revised.  
US nnn consists of the following parts, under the general title Introductory element — Main element :  
  Part n: Part title  
  Part [n+1]: Part title  
  Part [n+2]: Part title  
 DUS 2032 : 2018  
© UNBS 2018  – All rights reserved  v 
  
 UGANDA STANDARD  DUS 2032 : 2018  
 
© UNBS 2018  – All rights reserved  1 
 Concrete hollow b lock — Specification  
1 Scope   
The standard regulates the terminology and def inition of normal concrete  block, size, type, grade and mark, 
raw material, technological specification, test methods, inspection standard, qualification certificate, storage 
and trans portation.  
The standard applies to  the industrial and civil concrete  block (“Block”).  
2 Normative references   
The following referenced documents referred to in the text in such a way that some or all of their content 
constitutes requirements of this docu ment. For dated references, only the edition cited applies. For undated 
references, the latest edition of the referenced document (including any amendments) applies.  
US 310:  2016, Cement — Part 1: Composition, specification and conformity criteria for comm on cements  
DUS 2107 :2018, Test methods for concrete block and brick  
US 1681:  2017, Chemical admixtures for concrete — specification  
DUS 2108:2018, Sand for construction  
DUS 1691, Aggregates for concrete — Specification  
US EAS 12:2014, Potable water — Spec ification  
DUS 2109 :2109,  Radionuclide limitations   
3 Terms and definitions   
For the purposes of this document, the following terms and definitions apply.  
ISO and IEC maintain terminological databases for use in standardization at the following addresses:   
— ISO Online browsing platform: available at http://www.iso.org/obp  
3.1 
concrete hollow  block 
The concrete, mineral admixture, rubbles, sands, water and etc. are mixed and formed via the vibration into 
the small blo cks including hollow and solid ones.  
3.2 
main shape block  
The shape is right angle hexahedron. The length is 400mm vertical brick work joint thickness and height is 
200 mm horizontal work joint thickness. The side face is enclosed block.   
2 © UNBS 2018  – All rights reserved  
 3.3 
auxiliary bl ock 
The special shaped blocks, which are used associating with the main shape blocks are divided into hollow and 
solid, including non -standard shaped blocks, girth blocks, blocks with one opening end, 7 percentile blocks, 
half blocks and etc.  
3.4 
blocks wi thout mortar  
When the wall is constructed with the blocks, no slurry is needed. The  blocks are interconnected with  
structures.  
4 Specification, types, grades and marks  
4.1 Specification  
4.1.1  The part names of main shape block  
Refer to figure 1 for the pa rt name of main shape block  
 
Note:  
1 Side face;  
2 bedding face (smaller rib thickness)  
3 top face (bigger rib thickness)  
4 end face  
5 length  
6 width  
7 height  
8 wall  
9 rib 
Figure 1  The part name in block  WDUS 2032 : 2018  
© UNBS 2018  – All rights reserved  3 
  
4.1.2  The preferred shape for the block is rig ht angle hexahedron. The typical block size and specification 
are listed in table 1.  
Table 1  The specification and size of blocks  
Length (mm)  Width (mm)  Height (mm)  
390 90 
120 
140 
190 
240 
290 90, 
140, 
190 
Note   Other specifications and sizes can be deci ded by the buyers and sellers. 
If the blocks are used in the think brick wall joint, the sizes can be adjusted.  
4.2 Category  
4.2.1  Based on the hole rates, the blocks can be divided into hole blocks  (whose hole rate is above 25% 
with a code name H) and s olid blocks  (whose hole rate is below 25% with a code name S).  
4.2.2  Based on the block wall structure and force bearing, the blocks can be divided into weight bearing 
structure blocks (code name: L, “weight bearing blocks”) and non -weight bearing structu re blocks (code name 
N, “non -weight bearing blocks”)  
4.2.3  The auxiliary block includes : half blocks —50，7 percentile blocks —70，girth blocks —U, and blocks 
with a cleaning hole —W. 
4.3 Classification  
The classification of blocks based on the compressive st rength is listed in table 2.  
Table 2  The grades of compressive strength  
Block type  Load  bearing blocks （L）
(MPa)  non-load bearing blocks （N）
(MPa)  
hollow blocks （H） 7.5 
10.0 
15.0 
20.0 
25.0 5.0 
7.5 
10.0 
solid blocks （S） 15.0 
20.0 
25.0 
30.0 
35.0 
40.0 10.0 
15.0 
20.0  
4 © UNBS 2018  – All rights reserved  
 4.4 Mark  
The sequence numbers on blocks are listed in the following orders: block type, size, strength grade  (C), 
standard code name  
Examples of marks:  
a) For a weight bearing solid block whose size is 390 mmX190 mm  X190 mm and strength grade is 
C15.0, the sequence number will be LS 390X190 X190 C15.0 US 2032 —2018 . 
b) For a non -weight bearing hollow block whose size is 395 mmX190 mmX194 mm and strength grade 
is C5.0, the sequence number will be NH 395X190 X194 C5.0 US 2032 —2018 . 
c) For a weight bearing ha lf block whose size is 190 mmX190mmX190 mm and strength grade is C15.0, 
the sequence number will be LH50 190X190 X190 C15.0 US 2032 —2018 . 
5 Raw material  
5.1 Cement  
It shall comply with the provisions of US 310 -1. 
5.2 Aggregate  
5.2.1  Fine aggregates  
shall f ollow DUS 2108   
5.2.2  The coarse aggregates,  
rubbles and pebbles shall follow DUS 1691 . The maximum particle size of coarse aggregate shall not exceed 
10 mm,  
5.3 Fly ash  
It shall comply with the provisions of US 310 -1. 
5.4 Granulated blast -furnace slag po wder  
It shall comply with the provisions of US 310 -1. 
5.5 Water  
which shall follow US EAS 12 .  
5.6 Admixtures  
It shall comply with the provisions of US 1681  
5.7 Other m aterials  
Other raw material shall follow the relevant standards and produce no harm to b lock life, environment, and 
humans.  WDUS 2032 : 2018  
© UNBS 2018  – All rights reserved  5 
 6 Technical requirements  
6.1 Dimension deviation  
The permissible variation in dimension shall follow table 3. For the blocks used in thin brick joint, the allowable 
tolerance shall be controlled within + 1 mm and -2 mm.   
Table 3  Permissible variation in dimension  
Item Name  Technical index (mm)  
Length  ±2 
Width  ±2 
Height  +3，-2 
Note  The permissible variation in dimension for the blocks 
without mortar shall be given by the individuals. The size tolerance 
shall not impact  the stacking capability and wall performance.  
6.2 Appearance quality  
The appearance quality of blocks shall m eet the requirements in table.  
Table 4  Appearance quality  
Item Name  Technical index  
Bending   not higher than  2 mm  
The missing 
edges and 
corne rs  Qty. shall not exceed  1 
the maximum value of projected 
dimensions at three directions  not higher than  20 mm  
The aggregated projected dimensions of crack 
extension  not higher than  30 mm  
6.3 Hollow  rate  
The hollow rate for hollow blocks shall be below 25% (H) and above 25% (S) for solid blocks.  
6.4 External wall and rib thickness  
6.4.1   For weight bearing hollow blocks, the minimum external wall thickness shall not be less than 30 mm 
and the minimum rib thickness shall not be less than 25 mm.  
6.4.2 For weight bearing hollow blocks, the minimum external wall thickness and the minimum rib thickness 
shall not be less than 20 mm.  
6.5 Strength grade  
The strength of blocks shall follow table 5.  
 
 
  
6 © UNBS 2018  – All rights reserved  
 Table 5  Strength grade  
 
Strength grade  Compressive s trength  (MPa)  
Average value ≥  Minimum value of a single block ≥  
C5.0 5.0 4.0 
C7.5 7.5 6.0 
C10 10.0 8.0 
C15 15.0 12.0 
C20 20.0 16.0 
C25 25.0 20.0 
C30 30.0 24.0 
C35 35.0 28.0 
C40 40.0 32.0 
6.6 Water absorption  
The moisture absorption for L type blo cks and N type shall not exceed 10% and 14% respectively.  
6.7 The linear dryness shrinkage  
The linear dryness shrinkage for L type blocks and N type shall not exceed 0.45 mm/m and 0.65 mm/m 
respectively.  
6.8 Frost r esistance  
The frost resistance shall fo llow table 6.  
Table 6  Frost r esistance  
 
Service Conditions  Freezing resistance indicator  The quality loss rate  The strength loss rate  
The region with hot 
summer and warm winter  D15 
The average value ≤5%  
The maximum valve for 
single block ≤10%  The average value ≤20%  
The maximum valve for 
single block ≤ 30%  The region with hot 
summer and cold winter  D25 
Cold region  D35 
Severe Cold Area  D50 
6.9 Carbonization coefficient  
The io dization coefficient for blocks shall be above 0.85.  
6.10 Softening c oefficient  
The softening coefficient of blocks shall be above 0.85.  
6.11 The radionuclide limitations  
It shall comply with the provisions of DUS 2109 . WDUS 2032 : 2018  
© UNBS 2018  – All rights reserved  7 
 7 Test method  
The test for the radi onuclide limitations of blocks shall follow DUS 2109 . Other performance test methods shall 
follow DUS 2107 . If a sample in right angle hexahedron with a n enclosed hole cannot cut from the blocks, the 
strength test can adopt DUS 2107  appendix B. For the blo cks whose length is less than 290mm, the distance 
from the tested block and the portable deformeter during the measurement of linear dryness shrinkage shall 
be 150mm.  
8 Inspection r ules 
8.1 Classification of inspection  
The product inspection includes ex -work inspection and model inspection.  
8.1.1  Ex-factory inspection  
The inspection shall focus on the appearance quality, size tolerance, minimum rib thickness and strength.  
8.1.2  Type inspection  
The inspection conducted shall cover all the inspections list ed in section 6 of the standard. Type inspection 
shall be carried out in any of the following situations.  
a) Putting -into-production or approval appraisal of new product;  
b) After the normal production, when the raw material, recipe and process change;  
c) Once a ye ar during normal production;  
d) When the production resumes after offline for more than 3 months  
e) When the results of delivery inspection have relatively large difference with the results of the last type 
inspection;  
8.2 Batching r ules 
The blocks shall be insp ected and accepted by the type, specification, age and strength. Less than 30,000 
500m3 blocks with the same speciation, age and strength and material shall be considered as one batch. Less 
than 30,000 500 m3 per week.  
8.3 Sampling  
8.3.1  32 samples shall  be selected randomly per batch to inspect size tolerance and appearance.   
8.3.2  For the qualified lot, the following sample size shall be selected to conduct the listed inspection below:  
 
 
 
 
  
8 © UNBS 2018  – All rights reserved  
 Table 7  Sample q uantity  
 
Inspection item  Sample Quantity (Pe r piece of block ) 
（H/B）≥0.6 （H/B）<0.6 
Hole rate  3 3 
External wall and rib thickness  3 3 
Strength grade  5 10 
Water absorption  3 3 
The linear dryness shrinkage  3 3 
Frost Resistance  10 20 
Carbonization coefficient  12 22 
Softening Coefficient  10 20 
Radionuclide Limited Standard  3 3 
The note：H/B（ height and width ratio ）refers to the ratio between weight bearing 
height （H）and minimum horizontal size （B）under the operation condition.  
8.4 Acceptance  rules  
8.4.1  Only when the samples meet the requirem ents in table 3 and 4, the products are considered to be 
qualified.  
8.4.2  Among the 32 samples, when the nonconforming item blocks are more than 7, the batch is 
considered rejected.  
8.4.3  When all the inspection results meet the requirements in section 6 , the batch is considered qualified 
or it will be rejected.  
9 Product certificate, stacking and transport  
9.1 The blocks are allowed to be shipped out of factory when the nursery period turns into 28 days.  
9.2 The shipped blocks shall include a qualifica tion certificate, including  
a) Manufacturer name and trademark;  
b) lot size number and block number(pieces)  
c) Product sequence number and manufacturing date  
d) The ex -work inspection report and model inspection report within the effective date  
9.3 The blocks of th e same sequence number shall be stored together to avoid confusion. 10% of blocks 
shall bear the sequence numbers.  
9.4 Proper water -proof measures shall be taken during the storage, transportation, and construction. The 
blocks shall be packaged with films .  
9.5 During the unloading, care shall be paid to blocks to avoid throwing, dropping. No tipper hopper shall be 
allowed.  WDUS 2032 : 2018  
© UNBS 2018  – All rights reserved  9 
 Bibliography  
[1] GB 8239 -1997, Normal Concrete Small Hollow Blocks  
 
 US nnnn -n: yyyy  
© UNBS 2018  – All rights reserved  11 
 Certification marking  
Products that conform to Uganda standards may be marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licensed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in conjun ction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision, control and testing in accordance with t he 
certification mark scheme of the Uganda National Bureau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 US nnnn -n: yyyy    
 
ICS nn.nnn.nn  
Price based on nn pages  
© UNBS yyyy– All rights reserved