Concrete Compression

1. Modus Operandi Of Concrete Test
By Design & Contracts Dept.

2. Page 1 of 12
1. Introduction
A concrete test is performed to learn more about the properties of a specific sample of
concrete and to determine compressive strength of concrete. Because concrete is an
important structural element, testing is mandatory in many reasons. Test Result are also
kept in file in case a problem develops in the future. Concrete Compression Strength
report is required for various purposes including the following
 To identify and compliance of actual strength compared with Design Strength.
 To make Decision by the Designer if unusual cases.
 Safe guard to construction companies and legal documents to show to Government
authorities (If required)
2. Existing Policy on Concrete Compressive Strength Tests & Re-Bar Tensile
Strength test of at different Phase of Construction (Memo dt 13/11/2010):
SL
NO
Construction
Phase
Test Number of
Sample Set
Testing Laboratory
1 Pile Concrete
Cube
As per
requirement
1.*BRTC(1-set)
2.**ACL(at every 40 piles
intervals)
2 Pile Cap Concrete
Cube
01+01 BRTC & ACL
3 Footing Concrete
Cube
01+01 BRTC & ACL
4 Ground Floor
Column
Concrete
Cube
01+01 BRTC & ACL
Reinforcement 01 BRTC
5 All others Floor
Column
Concrete
Cube
01 ACL(Three successive floor
intervals)
6 Basement Roof Concrete
Cube
01+01 BRTC & ACL
7 Ground Floor
Roof
Concrete
Cube
01+01 BRTC & ACL
8 All other Roof
Slabs
Concrete
Cube
01 for each 1.ACL(For all roof slab)
2.BRTC(Three successive
roof slabs intervals)

3. Page 2 of 12
3. Modus Operandi
1) PIC will collect and necessary preparation of cube/cylinder Mold as described in the
‘’Cube making Procedure” in Anuxiure-1.
2) Sample collection, preservation and send to relevant lab in due time by PIC. In this
regard PIC ,Concerned AH will fill up the enclosed checklist annexed as “Annexure-
2” and forward to GM-PO
3) PIC will send samples to ACL, BUET, RMC lab in due time as per Memo dt
13/11/2010.
4) PIC will inform DCD for testing during submission of the samples in case of ACL
testing.
5) DCD concerned will ensure testing of samples in time and prepare the report in case
of testing in ACL lab.
6) DCD will preserve all the original report in H/O file and forward the copy to AMD for
his perusal in case of failure reports. One set of photocopy will forward to projects.
7) Further DCD will study all the reports and consult with our consultant for specific
and required cases (if any).
8) PIC will ensure timely testing in RMC lab/BUET lab test and original set will forward
to DCD.
9) DCD will also monitor and compliance project base testing and preserve all original
documents.
10) Concerned officials from respective Departments :-
a) Concerned official of DCD Technical team
i. Engr. Md Mominur Rouf (AGM-DC)
ii. Engr. Laila Noor (SrM-SD)
iii. Engr. Mohsinul Azad (SrEXC-SD)
iv. Engr. Abir Hossain (EXC-SD)
v. Engr. Farhat Aziz Sheen (EXC-SD)
b) Laboratory-in-Charge
i. Accountant (Central Store)
c) Laboratory Assistant
i. Site Assistant (Central Store)
d) Maintenance Works
i. Electrical maintenance support will be provided by EWD Maintenance wing prior
receiving the requisition from DCD. Necessary cost up to Tk.1500/- will be
borne by Project pretty cash where the Lab is attached & relevant approval
may be taken from concerned RH.

4. Page 3 of 12
ii. Mechanical & others maintenance support will be provided by MRD prior
receiving the requisition from DCD. Necessary cost up to TK.2500/- will be
borne by Project pretty cash where the Lab is attached & relevant approval
may be taken from concerned RH..
iii. Calibration & other up gradation (if any) will be performed by external agencies
prior Management approval through DCD.
iv. Hydraulic oil for machineries and other routine maintenance items will be
supplied by IM section prior requisition from DCD.
v. Routine maintenance will be done by Lab In Charge. DCD will monitor.
11) Responsibilities in Details:
a) Responsibilities of Lab In-Charge:
i. To manage overall activities of the Lab.
ii. To maintain all records, Files, Registry book of the Lab.
iii. To receive Specimen from projects and ensure specification(quality of sample)
requirements.
iv. To co-ordinate with the Technical Team.
v. Report Disbursement.
vi. To supervise Lab Assistant activities.
vii. To ensure due maintenance of the equipments.
b) Responsibilities of Technical Team [DCD]:
i. To perform the test with the help of Lab Assistant.
ii. To prepare the Test Report.
iii. To prepare Testing Schedule.
iv. To ensure timely performing tests.
v. Technical vetting of reports (if required) through Consultants.
vi. To preserve the original Reports in respective File of DCD.
c) Responsibilities of Lab Assistant:
i. To operate the Machine.
ii. To preserve cylinders.
iii. To perform Curing.
iv. Tested Cylinders disposal.
v. To provide necessary supports to the Lab-in-Charge and the Technical Team.
vi. To ensure Security of the Lab.

5. Page 4 of 12
12) Responsibilities of Area Head(AH) & Project in Charge(PIC)
i. To ensure proper sampling, preservation and timely send the sample to
concerned Lab as in this manual. [as per Internal memo on 13/11/10)
ii. To fill up the checklist as Annexure-1 and sent to GMPO with a copy to AGMDC.
14) Cube Making Apparatus:
i. Cube moulds of (15 X 15 X 15) cm size [minimum 3 no for each set]
ii. Trowel
iii. Sampling Scoop
iv. (25X25X400)mm square steel tamping rod with lower end flat / STEEL BAR 16MM
DIA AND 60CM LONG
v. 15cm long MS flat bar
vi. Wooden/rubber Hammer
vii. Wrench
viii. Steel BRASH
ix. Scraper
x. STEEL SCALE
xi. STEEL PAN
xii. MIXTURE MACHINE
xiii. Mould releasing oil ETC.

6. Page 5 of 12
CUBE MOULD TROWEL
SCOOP TAMPING ROD
RUBBER HAMMER WRENCH

7. Page 6 of 12
STEEL BRUSH SCRAPER
STEEL SCALE STEEL PAN
MIXTURE MACHINE MOULD RELEASING OIL

8. Page 7 of 12
15) Cube Making Procedure:
i. Separate the mould assembly and clean all interior faces, base with scraper to
remove rust/cement coating.
ii. Assemble cube moulds checking every dimension with steel scale /15cm long MS
flat bar.
iii. Oil the interior surface of the mould with mould releasing oil to prevent adhesion
of concrete. Don’t use excess oil.
iv. Sample should be true representative of concrete being used.
v. For site mixing, mixing time should be at least one minute or 20 revolutions of the
mixer from adding all aggregates to obtain a homogeneous mix.
vi. For ready mix concrete, before collecting concrete it should be mixed properly in
the mixer truck.
vii. Sample collecting pan should be near, clean and free from any loose material.
Collecting pan may be slightly moist with water but staking of water should be
avoided.
viii. At least one set (3cubes) sample should be taken from the same batch / mix.
ix. Fill the concrete in the molds in layers approximately 5 cm thick (total 3 layers).
x. Cube moulds of (15 X 15 X 15) cm size [minimum 3 no for each set].
xi. Each layer should be compacted BY 35 STROKES with tamping ROD [STEEL BAR
16MM DIA AND 60CM LONG, BULLET POINTED AT LOWER END] OR 25STROKES
WITH TAMPING BAR [25MM SQUARE AND 400MM LENGTH, lower end flat]
xii. Concrete should poured in the mould and tempered properly so as not to have
any voids.
xiii. The top surface of the specimen should be made even and smooth. This is done
by putting cement paste and spreading smoothly on whole area of specimen and
smoothen it with trowel.
xiv. Vibrate the mould using rubber / wooden hammer to remove air content/ voids
from concrete.
xv. Store the cube moulds in a place which is free from vibration and cover the
surface of the concrete with a piece of damp sacking for initial 16 to 24 hours.
xvi. After 24 hours of casting cubes, remove cubes from moulds. For ready mix
concrete sometimes it may take more than 24 hours to harden the concrete in
that case wait until concrete gains sufficient hardness.
xvii. After removing from mould mark casting date and name of structure for which
concrete being used on the cubes with a permanent marker. Submerge cubes
under clean water for curing.

9. Page 8 of 12
xviii. After 28 days take out cubes from curing tank.
xix. Send to laboratory / testing Authority for test.
xx. During transportation care should be taken to avoid any damage (broken edge) of
cubes.
16) Common Reasons behind the Failure of Concrete Test RESULTS:
i. High Water Cement Ratio.
ii. Use Inferior quality as well as improper gradation of stone chips / brick chips.
iii. Insufficient FM & poor gradation of Sand.
iv. Quality of Cement.
v. Inappropriate mixing procedure & timing.
vi. Faulty sampling.
vii. Inadequate and inaccurate time of curing.
viii. Adulteration of coarse and fine aggregate such as mud, clay, coal, wood or other
organic materials etc.
ix. Unskilled operation, handling and transportation.
x. Calibration of Machineries.
xi. Carelessness during testing like sample placement and loading.
xii. FEW PRACTICAL Problems observed in different Projects:
 Cubes are not found uniform size and shape.
 Too many pores in cube surfaces.
 Sending cube to lab without SSD condition(Saturated surface dry
Condition)
 Broken edges
 Surface undulation(not leveled and smooth) etc.

10. Page 9 of 12
Cubes not having uniform shape

11. Page 10 of 12
Having pores at cube surface
Cubes not in “SSD” condition

12. Page 11 of 12
Undulation surface
Broken Edges

13. Page 12 of 12
ANNEXURE-1
Asset Development & Holdings Ltd.
91 Gulshan,Dhaka
Cube Sent for Testing to BUET & ACL Checking Form
Project: Address:
Sl Structural
Item to be
Checked
Sample list for BRTC &
ACL
Date Checked
& signed
by PIC
Checked by AH Remarks
Sign Date
1 Pile BRTC(1 set)
ACL(at every 40 piles
intervals)
2 Pile Cap BRTC(1 set)
ACL(1 set)
3 Footing BRTC(1 set)
ACL(1 set)
4 Ground
Floor
Column
BRTC(1 set)
ACL(1 set)
5 All others
Floor
Column
ACL(Three
successive
floor
intervals)
1st
Floor
4th
Floor
8th
Floor
6 Basement
Roof
BRTC(1 set)
ACL(1 set)
7 Ground
Floor Roof
BRTC(1 set)
ACL(1 set)
8 All other
Roof Slabs
BRTC(Three
successive
roof slabs
intervals)
1st
Floor
4th
Floor
8th
Floor
ACL(For all
roof slab)
1st
Floor
2nd
Floor
3rd
Floor
4th
Floor
5th
Floor
6th
Floor
7th
Floor
8th
Floor