California Bearing Ratio Test

Parez Abdullah Mohammed
Iraq-Ranya

1. 1


University of Raparin
Civil Engineering Department
Third Stage (2018–2019)


CE304
Highway Engineering Laboratory
California Bearing Ratio Test (C.B.R.)
(ASTM D 1883 – 07, AASHTO T 193 – 99)
Laboratory Report # 5



Group: B

Name: Parez Abdullah Mohammed



Lab Performed on 5 /1/19 and Submitted on 12 /1/19

2. 2

Contents
Introduction: ..........................................................................................................................3
Apparatus:..............................................................................................................................4
Standard Reference: ................................................................................................................4
Procedure ...............................................................................................................................5
datasheet ................................................................................................................................6
Calculation:............................................................................................................................7
For Mold #1 ........................................................................................................................7
Density...............................................................................................................................7
Graph #1 ............................................................................................................................8
For Mold #2 ........................................................................................................................9
Density...............................................................................................................................9
Graph #2 ............................................................................................................................9
Discussion:........................................................................................................................... 10
Reference:............................................................................................................................ 12

3. 3

Introduction:
This document reports a test about California Bearing Ratio Test
(C.B.R.) which is operated in The University of Raparin Engineering
Laboratory. The test is an empirical test which gives an indication of the
shear strength of a soil. The great value of this test is that it is comparatively
easy to perform and because of its wide use throughout the world, there is a
vast amount of data to assist with the interpretation of results. The CBR test
is essentially a laboratory test but in some instances the test is carried out on
the soil in-situ.
There are a variety of different benefits to the CBR test, including:
determining how much the soil did is holding loads. Because if a soil field is
not holding loads well, then it would face embankment and stuff like that.
The laboratory CBR test consists essentially of preparing a sample of
soil in a cylindrical steel mold and then forcing a cylindrical steel plunger, of
nominal diameter 50 mm, into the sample at a controlled rate, whilst
measuring the force required to penetrate the sample.
CBR values may vary from less than 1% on soft clays to over 150% on
dense crushed rock samples.

4. 4

Apparatus:
1. Compaction Mold
2. Water
3. Wrench
4. Shovel
5. Scraper
6. Hammer
7. Spacer Disks
Standard Reference:
1. ASTM D1883 – 07
2. AASHTO T 193 – 99

5. 5

Procedure
1. First, we need to bring the soil and condition it until it reaches its
maximum moisture content by adding water to it, and then we should
mix it until it is totally mixed.
2. After that, the compaction starts. First we should remove the screw
from the compaction mold.
3. Remove the main mold from the platform.
4. Place the spacer disk and the filter paper on the top of the mold.
5. Return the mold to its platform.
6. Add the soil to the compaction mold and compacted into 3 layers
using 58 blows.
7. Reattach the upper portion of the compaction mold for the third layer.
8. Remove the upper portion of the mold. And, scrape of any remaining
soil.
9. Remove the compaction mold from the platform.
10. Weigh the compacted soil + mold
11. Reattach the mold to the platform without the spacer disk
12. Then place the mold onto the machine.
13. Load the disks and turn on the detection.
14. Start the test and get the data.
15. After all, remove the soil from the mold and take samples from the
soil.
16. Find out the moisture content by the methods you have learned before.
17. The end!

6. 6

datasheet

7. 7


Calculation:
For Mold #1

CBR =
���� ����??????�� �?????? ����??????���� �� ���??????��� ��������??????��
���� ����??????�� �?????? �������� ����ℎ�� ����� ������ ��������??????��
* 100%
penetration load Standard Load CBR Formula CBR
0 0 0 =
����
??????������
*100% 0
0.5 1.6 1.6
=
����
??????������
*100%
100
1 2.8 3.5 =
����
??????������
*100% 80
1.5 3.38 5 =
����
??????������
*100% 67.6
2 3.94 11.5
=
����
??????������
*100%
34.26086957
2.5 4.45 13.43 =
����
??????������
*100% 33.1347729
3 4.91 15.9 =
����
??????������
*100% 30.88050314
4 5.6 17.6
=
����
??????������
*100%
31.81818182
5 6.13 20.15 =
����
??????������
*100% 30.42183623
7.5 7.16 24.6 =
����
??????������
*100% 29.10569106
10 7.87 30.3
=
����
??????������
*100%
25.97359736
12.5 8.44 36.6 =
����
??????������
*100% 23.06010929
Density
Mass of soil = (Mass of mold + mass of soil) – mass of mold
= 7917-4078
= 3839
Bulk Density =
���� �� ��??????�
??????�����

=
3839
2124
= 1.807 kg/cm
3

Dry Density =
??????��� ??????���??????�??????
1+??????

=
1.807
1+0.078
= 1.676 kg/cm
3

8. 8

Graph #1
0
1
2
3
4
5
6
7
8
9
0 2 4 6 8 10 12 14
Load
Penetration
Load-Penetration Relationship Graph

9. 9


For Mold #2

CBR =
���� ����??????�� �?????? ����??????���� �� ���??????��� ��������??????��
���� ����??????�� �?????? �������� ����ℎ�� ����� ������ ��������??????��
* 100%
CBR2.5 =
6.85
13.43
*100 = 50.47%
CBR5 =
8.59
20.15
*100 = 42.61%
Density
Mass of soil = (Mass of mold + mass of soil) – mass of mold
= 18728-15081
= 3647
Bulk Density =
���� �� ��??????�
??????�����

=
3647
2124
= 1.72 kg/cm
3

Dry Density =
??????��� ??????���??????�??????
1+??????

=
1.72
1+0.078
= 1.6 kg/cm
3
Graph #2

-2
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14
Load
Penetration
load

10. 10

Discussion:
We did this test in University of Raparin about California
Bearing Ratio Test (C.B.R.). California Bearing Ratio Test (C.B.R.) testing
can be performed in a lab. The California Bearing Ratio (CBR) test is a simple
strength test that compares the bearing capacity of a material with that of a
well-graded crushed stone (thus, a high-quality crushed stone material should
have a CBR 100%).
We took the examples 2.5mm and 5mm as it represents all of them to
find out the C.B.R. Generally, the C.B.R. value at 2.5 mm will be greater that
at 5 mm and in such a case/the former shall be taken as C.B.R. for design
purpose. If C.B.R. for 5 mm exceeds that for 2.5 mm, the test should be
repeated. If identical results follow, the C.B.R. corresponding to 5 mm
penetration should be taken for design. But in our test the C.B.R. for 2.5 mm
was greater than the C.B.R. for 5 mm, so we do not need to repeat the test
again.
The first graph which is for the first mold is going very well and does
not need any correction, so I used it for calculation. However, the second
graph which was for the second mold test that is done by the other group of

11. 11

students needed correction because it had an S shape curve. Therefore, I did a
correction for it to calculate the data. The correction is done on the graph #2.
We had some error sources. For example the students were not careful
enough about weighing the mass of the soil. I observed some different
numbers but they did not listen to me. Also, the machine was not working
properly. The teachers spend half an hour till they made the machine to work.
It finally worked, but it was just an assumption according to my observation
in the lab.
In conclusion, the test was very important and useful for us as engineer
students to test a soil sample to fine out the C.B.R.

12. 12

Reference:
1. https://www.astm.org/Standards/D1883.htm
2. http://www.rhd.gov.bd/Documents/ContractDocuments/StandardTestProcedur
es/California%20Bearing%20Ratio(CBR)%20Test.pdf
3. ASTM D1883 – 07
4. AASHTO T 193 – 99