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HIGHWAY MATERIALSPart 2

Compaction and CBR

Mr Che Ros Ismail| Dr Norhidayah Abdul Hassan

Faculty of Civil Engineering

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  How to determine the

strength or bearingcapacity of soil?

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Two major processes

Compaction test

(determine Maximum DryDensity, MDD and Optimum

Moisture Content, OMC)

California Bearing Ratio test

(determine CBR value)

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Compact ion

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Data and analysis

Calculate dry density andmoisture content (plot DD vs. MC)

Determine MDD and OMC

Compaction of sample

Tools: mold 2.3L, hammer 4.5 kgProcedures: compacted for 5

layers, 62 blows/layer

Sample preparation

dry soil (particle size ≤ 20mm) 5 different moisture contents

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1

2

Compaction steps

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Compaction steps

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3

4

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4

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Compaction steps

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Example Data:

Compaction data:

Moisture content data:

Sample1

Sample2

Sample3

Sample4

Sample5

Mass of mould (g)

Mass of mould + compacted sample (g)

Mass of compacted sample (g)

Bulk Density (Mg/m3)

Dry density (Mg/m3)

Sample

1

Sample

2

Sample

3

Sample

4

Sample

5

Mass of container (g)

Mass of container + wet sample (g)

Mass of container + dry sample (g)

Moisture content (%)

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Dry Density vs. Moisture Content

Moisture Content

Dry Density

Compaction

CurveMDD

OMC

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CBR Test

Data and analysisDetermine dry density, Plot Load (kN)

vs. Penetration of Plunger (mm)Determine Top and bottom CBR

values at 2.5 and 5 mm pen.

Compaction of sampleTools: mold 2.3L, hammer 4.5

kgProcedures: 3 samples, compacted for 5 layers,65, 35, 15 blows/layer, soaked in water for 4 days

Sample preparation

dry soil (particle size ≤ 20mm) optimum moisture content

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Top

Bottom

Soaked CBR

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CBR Testing

Sample

Penetration

dial gauge

Loading

dial gauge

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CBR 1

0 2 4 6 8

0

2

4

6

8

10

12

Penetration, mm

    L   o   a    d ,    k

    N

2.5 5.0

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CBR 2

0 2 4 6 8

0

2

4

6

8

10

12

Penetration, mm

    L   o   a    d ,

    k    N

2.5 5.0

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CBR 3

0 2 4 6 8

0

2

4

6

8

10

12

Penetration, mm

    L   o   a    d ,    k

    N

0 2.5mm 5.0mm

Tangent line

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CBR analysis

1. Calculate CBR values of top and bottom @ 2.5 and 5.0mm:

CBR@2.5mm = load at 2.5mm/13.24 x100

CBR@5.0mm = load at 5.0mm/19.96 x100

2. Report the highest CBR values for top and bottom and dry

density for all 3 samples

3. Plot CBR values versus dry density and determine CBR at

95% compaction (95% MDD)

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CBR vs . DD Data

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CBR vs. DD

95% compaction = 95% MDD

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I n-situ CBR

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THANK YOU