PAVEMENT MATERIALS PAVEMENT MATERIALS ENGINEERINGENGINEERING

(CE-862) (CE-862) Lec-01 (Lab 1)

Fall Semester 2016 

Dr. Arshad Hussainarshad_nit@yahoo.com , Office Room#111, Tel:

05190854163, Cell: 03419756251

National Institute of Transportation (NIT)

National University of Science and Technology (NUST)

NUST Campus, Sector H-12, Islamabad

SOIL Testing

•Most common tests include:• Plasticity (Atterbergs limits)• Sieve Analysis• Moisture• Unit Weight• Proctor• CBR

AtterbergAtterberg Albert Atterberg was a Swedish chemist and agricultural

scientist.

Conducted studies to identify the specific minerals that give a clayey soil its plastic nature

Stated that depending on the water content, soil may appear in four states:

Solid (no water) semi-solid (brittle, some water) plastic (moldable) liquid (fluid)

In each state the consistency and behavior of a soil is different and thus so are its engineering properties.

The boundary between each state can be defined based on a change in the soil's behavior.

Atterberg LimitsAtterberg Limits

(Non-Plastic )

Plasticity Index

Wpl wll

Plastic Limit Liquid Limit

Water Content w%=0

Solid LiquidPlasticBrittle

Plastic limitPlastic limit

The plastic limit (PL) is the water content (w%) where soil starts to exhibit plastic behavior.

Liquid limitLiquid limit

The liquid limit (LL) is the water content where a soil changes from liquid to plastic behavior

Determined using a Casagrande cup (lab) or cone penetrometer (field)

Shrinkage limitShrinkage limitThe shrinkage limit (SL) is the

water content where further loss of moisture will not result in any more volume reduction

The shrinkage limit is much less commonly used than the liquid limit and the plastic limit.

Use of Plasticity IndexUse of Plasticity Index

The PI is the difference between the liquid limit and the plastic limit (PI = LL-PL).

The plasticity index is the size of the range of water contents where the soil exhibits plastic properties.

Meaning: ◦ High PI tend to be clay◦ Low PI tend to be silt◦ PI of 0 tend to have little or no silt or clay.

Use of Liquid & Plastic Use of Liquid & Plastic LimitsLimitsUsed internationally for soil

identification and soil classification (AASHTO)

Liquid LimitLiquid LimitProcedures: To perform the liquid

limit test, one must place a soil paste in the cup. A groove is then cut at the center of the soil pat with the standard grooving tool. By the use of the crank-operated cam, the cup is lifted and dropped from a height of 10 mm (0.394 in.). The moisture content, in percent, required to close a distance of 12.7 mm (0.5 in.)

Liquid LimitLiquid Limitalong the bottom of the groove after 25

blows is defined as the liquid limit. 25 blows is defined as the liquid limit. It is difficult to adjust the moisture content in the soil to meet the required 12.7 mm (0.5 in.) closure of the groove in the soil pat at 25 blows. Hence, at least three tests for the same soil are conducted at varying moisture contents, with the number of blows, N, required to achieve closure varying between 15 and 35. 

Liquid LimitLiquid Limitalong the bottom of the groove after 25

blows is defined as the liquid limit. 25 blows is defined as the liquid limit. It is difficult to adjust the moisture content in the soil to meet the required 12.7 mm (0.5 in.) closure of the groove in the soil pat at 25 blows. Hence, at least three tests for the same soil are conducted at varying moisture contents, with the number of blows, N, required to achieve closure varying between 15 and 35. 

Liquid limit (LL) determination

NEED AND SCOPE

Liquid limit is significant to know the stress history and general properties of the soil met with construction. From the results of liquid limit the compression index may be estimated. The compression index value will help us in settlement analysis. If the natural moisture content of soil is closer to liquid limit, the soil can be considered as soft if the moisture content is lesser than liquids limit, the soil can be considered as soft if the moisture content is lesser than liquid limit. The soil is brittle and stiffer.

150g air dry soil passing # 40sieve.

Add 20% of water-mix thoroughly.

Place a small sample of soil in LL device(deepest part about 8-10mm).

Cut a groove(2mm at the base).

Run the device, count the number of blows, N.

Stop when the groove in the soil close through a distance of 12.7 mm

Procedure:-

Take a sample and find the moisture content.

Run the test three times[N~(10-20), N~(20-30) and N~(35-45)].

Plot number of blows vs moisture content and determine the liquid limit(LL)( moisture content at 25 blows).

Procedure:-

OBSERVATIONSDetails of the sample:.......

Natural moisture content:........                Room temperature:..............

Determination Number

1 2 3 4

Container number  

Weight of container  Weight of container + wet soil  Weight of container + dry soil  Weight of water  Weight of dry soil  Moisture content (%)  No. of blows  

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COMPUTATION / CALCULATION

Draw a graph showing the relationship between water content (on y-axis) and number of blows (on x-axis) on semi-log graph. The curve obtained is called flow curve. The moisture content corresponding to 25 drops (blows) as read from the represents liquid limit. It is usually expressed to the nearest whole number.

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Flow curve for liquid limit determination of a clayey silt:-

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Plastic LimitPlastic LimitIn the laboratory, the plastic limit

is defined as the moisture content (%) at which a thread of soil will just crumble when rolled to a diameter of 1/8in. (3.18 mm). 

Plastic Limit (PL)The plastic limit (PL) is defined as the moisture content (%) at which the soil when rolled into threads of 3.2 mm in diameter , will crumble. It is the lower limit of the plastic stage of soil.

Procedure:Take 20g of soil passing # 40 sieve into a dish.

Add water and mix thoroughly.

Prepare several ellipsoidal-shaped soil masses by quizzing the soil with your hand.

Put the soil in rolling device, and roll the soil until the thread reaches 3.2mm.

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Continue rolling until the thread crumbles into several pieces.

Determine the moisture content of about 6g of the crumbled soil.

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Grain Size DistributionGrain Size Distribution

To know the relative proportions of different grain sizes.

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An important factor influencing the geotechnical characteristics of a coarse grain soil.

Not important in fine grain soils.

Significance of GSD:

S.N.P.I.T.& R.C.

Grain Size DistributionGrain Size Distribution

In coarse grain soils …... By sieve analysis

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Determination of GSD:

fine grain soils …... By hydrometer analysisIn

Sieve Analysis

Hydrometer Analysis

soil/water suspension

hydrometer

stack of sieves

sieve shaker

S.N.P.I.T.& R.C.

Sieve AnalysesSieve Analyses

27S.N.P.I.T.& R.C.

Sieve AnalysisSieve Analysis

28S.N.P.I.T.& R.C.

Sieve Designation - LargeSieve Designation - Large

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Sieves larger than the #4 sieve are designated by the size of the openings in the sieve

S.N.P.I.T.& R.C.

Sieve Designation - SmallerSieve Designation - Smaller

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10 openings per inch

# 10 sieve

1-inch

Smaller sieves are numbered according to the number of openings per inch

S.N.P.I.T.& R.C.

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Sieving procedure(1) Write down the weight of each sieve as well as the bottom pan to be used in the analysis.

(2) Record the weight of the given dry soil sample.

(3) Make sure that all the sieves are clean, and assemble them in the ascending order of sieve numbers (#4 sieve at top and #200 sieve at bottom). Place the pan below #200 sieve. Carefully pour the soil sample into the top sieve and place the cap over it.

(4) Place the sieve stack in the mechanical shaker and shake for 10 minutes.

(5) Remove the stack from the shaker and carefully weigh and record the weight of each sieve with its retained soil. In addition, remember to weigh and record the weight of the bottom pan with its retained fine soil.

S.N.P.I.T.& R.C.

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S.N.P.I.T.& R.C.

33S.N.P.I.T.& R.C.

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Data Analysis:(1) Obtain the mass of soil retained on each sieve by subtracting the weight of the empty sieve from the mass of the sieve + retained soil, and record this mass as the weight retained on the data sheet. The sum of these retained masses should be approximately equals the initial mass of the soil sample. A loss of more than two percent is unsatisfactory.

(2) Calculate the percent retained on each sieve by dividing the weight retained on each sieve by the original sample mass.

(3) Calculate the percent passing (or percent finer) by starting with 100 percent and subtracting the percent retained on each sieve as a cumulative procedure.

S.N.P.I.T.& R.C.

Sieve SizesSieve Sizes

35(Das, 1998) (Head, 1992)

S.N.P.I.T.& R.C.

36S.N.P.I.T.& R.C.

37S.N.P.I.T.& R.C.

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For example: Total mass = 500 g,

Mass retained on No. 4 sieve = 9.7 g

For the No.4 sieve:

Quantity passing = Total mass - Mass retained

= 500 - 9.7 = 490.3 g

The percent retained is calculated as;

% retained = Mass retained/Total mass

= (9.7/500) X 100 = 1.9 %

From this, the % passing = 100 - 1.9 = 98.1 %

S.N.P.I.T.& R.C.

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Grain size distributionGrain size distribution

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

S.N.P.I.T.& R.C.

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Grading curves

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

W Well graded

U Uniform

P Poorly graded

C Well graded with some clay

F Well graded with an excess of fines

S.N.P.I.T.& R.C.

Proctor Compaction TestProctor Compaction TestTest developed to

help specify levels (%) compaction (1933).

Ralph R. Proctor first defined this standard compaction test in Engineering News Record

Proctor Compaction Proctor Compaction ProcedureProcedure

Soil is air dried, pulverized & passed thru #4 sieve.

Separated into 4 to 6 samples.

Adjust the water content of each sample by adding water.

Using the proctor mould (1/30th cubic foot) place & compact soil in 3 layers.

Each layer should receive 25 drops of the compaction hammer.

Proctor Compaction Proctor Compaction ProcedureProcedure

Proctor Compaction Proctor Compaction ProcedureProcedure

After the last layer, use a straight edge to trim the excess soil leveling to the top of the mould.

Proctor Compaction Proctor Compaction ProcedureProcedureDetermine the weight of the mould

with the compacted moist soil.

Extrude from mould and collect a sample for water content determination.

Repeat for each sample over a range of moisture contents.

Proctor Compaction Proctor Compaction ProcedureProcedure

After collecting all pertinent weights, calculate dry density and plot vs. water content

Typical Proctor DataTypical Proctor Data 1 2   3  4  5  6  7  8  9

Mold (lbs)Mold + Wet Soil (lbs) Moist Soil (lbs)

Moist Unit Wt. (pcf)

Mass of Can (g)

Mass Can + Moist Soil (g)

Mass of Can + Dry Soil

Moisture Content Dry Unit Wt.

9.31 13.23 3.92 117.60 61.00 273.50 249.70 0.13 104.43

9.20 13.60 4.40 132.00 61.00 280.00 249.20 0.16 113.44

9.31 13.52 4.21 126.30 61.00 242.90 214.90 0.18 106.86

9.30 13.34 4.04 121.20 61.00 306.70 265.60 0.20 100.93

9.20 13.25 4.05 121.50 61.00 222.60 190.20 0.25 97.14

9.31 13.16 3.85 115.50 61.00 212.20 178.10 0.29 89.45

(Line 3)/(1/30) (Line 4)/(1+Line 8)

Graph from Proctor DataGraph from Proctor Data

CALIFORNIA BEARING RATIO (CBR) METHOD

Typical Testing Machine

IntroductionIntroductionThe California Bearing Ratio devised by

engineers of the California Division of Highways in nine years period to 1938.

Most universally accepted pavement design methods.

A standard penetration-type load-deformation test is carried out, and using the values obtained from the test from an empirical design chart, the pavement thickness are calculated.

CBR LABORATORY TESTCBR LABORATORY TESTSpecimen may be

•Prepared•In-situ

Mould •150mm diameter•127.3mm height•Separate base plate•A collar

The specimen is soaked and the expansion is measured.

Load is applied by the loading frame through a cylinder plunger of 50mm diameter and penetration is measured.

Rate of penetration is maintained at 1.25mm/minute.

Loads are recorded for 2.5 and 5.0mm.Load is expressed as a percentage of

the standard load at the respective deformation level, and is known as the CBR value.

CBR EquipmentCBR Equipment

Typical Testing Machine Soaking Samples

CBR Test – Load-Penetration Measurement

CBR Test – Sample Preparation

CBR EquipmentCBR Equipment

California Bearing Ratio California Bearing Ratio (CBR)(CBR)

Load a piston at a constant rate

See what load it takes to make it penetrate a known amount

CBR EquationCBR Equation

yxCBR 100

x = material resistance or the unit load on the piston (pressure) for 2.5 mm or 5 mm of penetration

y = standard unit load (pressure) for well graded crushed stone. For 2.5 mm of penetration = 1000 psi For 5.0 mm of penetration = 1500 psi

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