HIGHWAY ENGINEERING PRACTICAL REPORT ON PROCTOR AND UNSOAKED CBR TESTSPROCTOR TESTMoisture content the mass of water in the soil expressed as a percentage of the dry mass of soil.

Optimum moisture content (OMC) the amount of water required to lubricate the soil particles and enable maximum tight packing under compaction.

Maximum dry density (MDD) the maximum mass of material that can be packed tight in a unit volume by compaction (normally plotted at the pick of the curve).

Reference: BS 1377, AASHTO T99 and T180

Equipment used

1 literMould 4.5 kg rammer

Containers

Trays

20mm sieve

Balance

Oven

Procedure

6Kg of an air dried sample which passed through the 20mm sieve and quartered was obtained.

The mould was weighed together with its base plate and weight was recorded

The soil was put on a tray and mixed thoroughly with water in volumes from 100-500ml.

The mould + base were put on a solid base, the collar fixed and the soil was filled and compacted in the mould in 5equal layers.

The blows (27) were distributed uniformly over the surface and of each layer and the last layer was at most 6mm over the mould.

The collar was removed, the excess soil over the edge trimmed and the weight of the mould+base+soil measured and recorded.

The mould was placed in a tray, the soil removed and a small portion was removed and measured for moisture content. The small portion was oven dried for 24 hours and then weighed. The difference between the two weights was the Natural Moisture Content (water).

The above procedure was repeated with a different amount of water.

A graph of dry density against moisture content was drawn. Its peak was the MDD value while the corresponding value on the moisture content axis was the OMC.

Mass Wet soil = Mass of mould + sample Mass of mould

Wet/bulk density =Dry density =m is moisture content.

m =MDD and OMC = peak of the curve (MDD) and the corresponding value on the horizontal scale (OMC)

Sample Number1234

Volume of water/ml120250300450

Percentage of water12253045

Mass of mould/g4487448744874487

Mass of mould +compacted specimen6207636563766328

Mass of compacted specimen1720187818891841

Bulk Density/g/cm1.721.8781.8891.841

Mass of container/g3.583.53.5

Mass of container + wet sample/g257.2427491.590.5

Mass of container + dry sample/g244.24246.58175.5

Mass of water/g1327.510.515

Mass of dry sample/g240.74238.577.572

Moisture content/%5.4011.5313.5520.83

Dry density1.631.681.661.52

Graph of dry density against moisture content

OMC %10.0%

MDD g/cm31.69

CBR TEST FOR AN UNSOAKED SAMPLE

CBR in full is California Bearing Ratio. This the basic test used to measure the strength (bearing capacity) of soil for pavement construction. It involves the penetration of a moulded soil sample with a cylindrical plunger at a constant rate of 1mm/min. the force corresponding to a penetration of 2.5mm and 5.0mm are computed and then compared with the standard force (normally reported as a percentage).

References: CML TEST 1.11, BS 1377: Part 4:1990 Equipment used;

Mould of vol. 2000cm3 2.5 kg rammer

Containers

Trays

Balance

Oven

Plunger dial gauge

Procedure

1. 5.458Kgs of material which passed through the 20mm sieve were used.

2. The Optimum Moisture Content (OMC) of the material was obtained from the proctor test.

3. The amount of water, m to be added to the soil so as to reach the OMC was calculated as follows;

OMC = 10%

= 545.8 cm3 of water.4. The weight of the mould + base plate was measured and recorded.

5. The soil was put on a tray and thoroughly mixed with water.

6. With the filter paper already in the mould, the mould was filled with the mixed soil in 3 equal layers. Each layer was given 65 blows courtesy of a 2.5Kg rammer.

7. After compaction the collar was removed, excess material removed and the weight of the mould + sample was measured, bulk density as well as the dry density was also calculated. A portion of the material was oven dried to check the moisture content.

8. The sample was then penetrated using plunger on the CBR machine.

9. The load at penetrations 0-7.5mm in 0.5mm intervals was recorded.

10. A ring factor of 0.0265KN/div was used to calculate the Equivalent load.

11. A graph of Equivalent load against penetration was plotted.

Calculations

Equivalent load = 0.0265 % dry density or relative compaction =CBR at 2.5mm =CBR at 5.0mm = Wet density = Dry density =m is moisture content.

m =Compaction effort3*65

wt. of sample + mould (g)8689

wt. of mould (g)4770

wt. of sample (g)3919

volume of mould (cm3)2000

wet density (g/cm3)1.9595

wt. of container (g)5

wt. of container + wet sample (g)75

wt. of container + dry sample (g)68.64

wt. of water (g)6.36

moisture content 9.994%

dry density (g/cm3)1.781

compaction informationMDD (g/cm3) = 1.69

OMC (%) = 10

Penetration of plunger(mm) 3*65

Dial gauge readingEffective load/KN

TOPBOTTOMTOPBOTTOM

00000

0.522150.5830.3975

150581.3251.537

1.581962.14652.544

21181223.1273.233

2.51501403.9753.71

31741524.6114.028

3.5194160.55.1414.25325

4208168.55.5124.46525

4.5220175.55.834.65075

5231181.56.12154.80975

5.5240187.56.364.96875

62481936.5725.1145

6.52551986.75755.247

72602036.895.3795

7.52652067.02255.459

CALICULATION OF CBR %3*65

TOPBOTTOM

CBR @ 2.5mm29.226.2

CBR @ 5 mm3125.25

1

_1517957796.xlsChart1

00

0.5830.3975

1.3251.537

2.14652.544

3.1273.233

3.9753.71

4.6114.028

5.1414.25325

5.5124.46525

5.834.65075

6.12154.80975

6.364.96875

6.5725.1145

6.75755.247

6.895.3795

7.02255.459

Penetration of plunger (mm)

Equivalent load (KN)

CBR CHART FOR AN UNSOAKED SAMPLE

Sheet1

Penetration of plunger(mm)3*65

Dial gauge readingEffective load/KN

TOPBOTTOMTOPBOTTOM

00000

0.522150.5830.3975

150581.3251.537

1.581962.14652.544

21181223.1273.233

2.51501403.9753.71

31741524.6114.028

3.5194160.55.1414.25325

4208168.55.5124.46525

4.5220175.55.834.65075

5231181.56.12154.80975

5.5240187.56.364.96875

62481936.5725.1145

6.52551986.75755.247

72602036.895.3795

7.52652067.02255.459

Compaction effort3*65

wt of sample + mould (g)8689

wt of mould (g)4770

wt of sample (g)3919

volume of mould (cm3)2000

wet density (g/cm3)1.9595

wt of container (g)5

wt of container + wet sample (g)75

wt of container + dry sample (g)68.64

wt of water (g)6.36

moisture content10.01

dry density (g/cm3)1.781

compaction informationMDD (g/cm3) = 1.69

OMC (%) = 10

CALICULATION OF CBR %3*65

TOPBOTTOM

CBR @ 2.5mm29.226.2

CBR @ 5 mm3125.25

Sheet1

Penetration of plunger (mm)

Equivalent load (KN)

CBR CHART FOR AN UNSOAKED SAMPLE

Sheet2

Sheet3