Compressive Strength of Hydraulic Cement Mortar | Jameel Academy

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1. University of Duhok
College of Engineering
Civil Department
Concrete Technology – Practical
Concrete Laboratory



A Report About :


Compressive Strength of Hydraulic
Cement Mortar





Submitted By : Jameel Masoud Jameel

Lab. No. : 4
Group Name : B1

Testing Date : 5 / 11 / 2017
Submitting Date : 19 / 11 / 2017

Supervised By : Youkhanna

2017 – 2018

2. References :

1) ASTM C109-07
2) ASTM C305-99




Introduction :

The most commonly used test is Compressive strength in construction
which is the Ability of material (Cement Mortar) to resist axially directed
Compression forces. When the limit of compressive strength is reached,
the material can't resist any force, then the materials are crushed
(damaged). The cube of cement mortar that used in test, which its
dimensions are (5cm × 5cm × 5cm), The compressive strength is used to
determine the hardness of cubical specimens of cement mortar. And to
know the ability of cement mortar to resist a load.







Purpose :

This test method provides a means of determining the compressive strength
of hydraulic cement mortars and results may be used to determine
compliance with specifications.

3. Materials :

1) Potable water.
2) Ordinary Portland cement (OPC).
3) Local sand [similar to Ottawa sand, sized between sieves No.20
(850 micron) and sieve No.30 (600 micron) ].








Equipment :

1) Sensitive balance,
2) Graduate cylinder,
3) Standard molds of (5×5) cm (2”×2”) dimension,
4) Mechanical Mixer,
5) Testing machine,
6) Small trowel,
7) Rubber or Wooden Tamper,
8) Brush,
9) Coating release agents (oils, or greases),
10) Sieves No.20 and No.30, and
11) Hand covers (plastic gloves).

4. Sketches :









Mixer Testing machine Sensitive balance








Graduate Cylinder Standard molds of (5×5) cm

`








hand Cover Sieve No. 20 & 30 Trowel

5. Procedures :

1) The proportions of materials for the standard mortar shall be one part of cement to
2.75 parts of graded standard sand by weight. Use a water-cement ratio of 0.485 for
all Portland cements. Thus, the amount of materials required to produce one set of
three cubes are (400 grams of Portland cement), (1100 grams of Ottawa Sand) and
(194 cc of water).

2) Place the 194 cc of water in the mixing bowl, add the 500 grams of cement, and mix
at a slow speed for 30 seconds.

3) Add the 1100 grams of Ottawa Sand over a 30-second period while continuing to mix
at a slow speed.

4) Stop the mixing, change the mixer setting to medium speed (285 ± 5 rpm), and mix
for 30 seconds.

5) Stop the mixer and let the mortar stand for 90 sec. During the first 15 seconds, scrape
down into the batch any mortar that may have collected on the sides of the bowl.
Cover the bowl for the remainder of the interval.

6) Finish preparing the mortar by mixing for 60 seconds at medium speed.

7) Immediately upon completion of mixing, start molding the specimens by placing a
25 ± mm (1 ± in.) layer of mortar in all of the three cube compartments. Tamp the
mortar layer in each cube compartment with the hard rubber tamper 32 times within
about 10 seconds in accordance with Figure (1) in four rounds. Each round to be at
right angles to the other and consisting of eight adjacent strokes over the surface of
the specimen. Use sufficient tamping pressure to ensure uniform filling of the molds.
Complete the lift in each mold in turn before moving on to the next one.

8) Complete the filling of the molds by adding another layer and duplicate the tamping
procedure. At this point the mortar should be slightly above the top of the molds.
Carefully cut the excess mortar flush with the edge of a steel trowel.

9) Place the completed mortar cubes in a moist closet, protected from dripping water for
20 to 24 hours after which the cubes are to be stripped from the molds.

10) Insert the mortar cubes in a water bath until ready for testing.

11) All specimens should be tested within a specified time period:

Test Age Permissible Time Tolerance
24 hours ± 1/2 hour
3 days ± 1 hour
7 days ± 3 hours
28 days ± 12 hours

6. Calculations and Results :


- We will determine the compressive strength of Cubes by using this Formula :

??????��������??????� ��������=
�????????????��??????� ��??????�
??????����−�������??????� ??????��??????


Area of each cubes : A = 50mm × 50mm = 2500m�
??????


With different Cube we have different Load :

Cube 1 Compressive strength=
Load
Area
=
84100 N
????????????????????????��
??????
= 33.64
??????
mm
2

Cube 2 Compressive strength=
Load
Area
=
84400 N
????????????????????????��
??????
= 33.76
??????
mm
2

Cube 3 Compressive strength=
Load
Area
=
75300 N
????????????????????????��
??????
= 30.12
??????
mm
2

Cube 4 Compressive strength=
Load
Area
=
84400 N
????????????????????????��
??????
= 33.76
??????
mm
2

Cube 5 Compressive strength=
Load
Area
=
87100 N
????????????????????????��
??????
= 34.84
??????
mm
2

Cube 6 Compressive strength=
Load
Area
=
90600 N
????????????????????????��
??????
= 36.24
??????
mm
2


For more details :
Group Cube Area (mm
2
) Load (kN) Compressive Strength (MPa)
B1
And
B2
1 2500mm
2
84.1 33.64
2 2500mm
2
84.4 33.76
3 2500mm
2
75.3 30.12
B3
And
B4
4 2500mm
2
84.4 33.76
5 2500mm
2
87.1 34.84
6 2500mm
2
90.6 36.24
Average 34.45 MPa

Note :
The average of all cubes was (33.73), but all compressive strength that given from test
must be in the range of (33.73 ± 3.37), the cube 3 is not placed in range so we won't use
it in calculating average . therefore the average will be (34.45 MPa).

7. Discussion and Conclusion :

In this test we determine the compressive strength of Cement mortar,
finally we got a result after doing all procedure accurate, that the average
of all cubes are (34.45 MPa) according to standard, we determine the
average compressive strength of all cubes because each cubes have a
different compressive strength, if we compare our result with standard
which is the compressive strength must be greater than (24 MPa) for 7
days. as we know that our result is greater than the standard. it shown
that our cement mortar can be used for construction work. if we have an
errors in this test then we will have them in the processes especially in
the compaction of cement mortar process, but we did the test on 6 cubes
and we got the result, therefore the result will be very accurate.

In conclusion the purpose of this test is to determine the resistance of
cement mortar from compression load and compare the result with
standard, finally we got the result, and the cement mortar that is used in
test can be used in any construction project.