CPD SEMINAR ON CLASSIFICATION OF ROAD MATERIALS AND IDENTIFICATION OF INDEGINOUS

QUARRIES

Engr. Zahid Arif, Secretary C&W Department

December 11, 2012

By

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SEQUENCE OF PRESENTATION

INTRODUCTION

IMPORTANCE OF THE SUBJECT

SOIL CLASSIFICATION

SPECIFIED PARAMETERS OF SUB BASE & BASE

MATERIALS

IDENTIFICATION OF INDEGINOUS QUARRIES

QUESTION & ANSWER SESSION3

IMPORTANCE OF THE SUBJECT

Selection of specified materials through:

Visual inspection

Laboratory tests

Economizing the construction cost

Identification of local quarries

Effective supervision and monitoring of developmental projects

Selection of suitable site for Building projects

SOIL CLASSIFICATION

SOIL CLASSIFICATION Soil is defined as a conglomeration consisting of a wide

range of relatively smaller particles derived from a parent rock through mechanical weathering processes of water abrasion, freeze-thaw cycles, temperature changes, and chemical weathering processes like oxidation and carbonation. The density of soil mass can range from very hard to very soft.

Classification is the laboratory-based process of grouping soils with similar engineering characteristics into various categories.

The AASHTO system (M 145) is commonly used for grouping of soils into various categories having similar load carrying capacity for subgrade design of highway projects.

Engineering Classification of Soils

Cassagrande apparatus

WentworthScale

“Gravel”75-2 mm

“Sand”2-0.075 mm

“Silt and Clay”< 0.075 mm

“Cobbles” 75 – 300 mm ( 3 in – 12 in)

Particle Size Definitions

“Boulders” > 300mm(>12 inches)

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Grain Size definitions

Boulders Cobbles Gravel Sand Silt and Clay

Coarse Fine Coarse FineMedium

300 mm

75 mm

19 mm

(No.4)

4.75 mm

(No.10)

2.0 mm

(No.40)

0.425 mm

(No.200)

0.075 mm

Parameters of Soil Classification

For grouping of Soil in various categories, the following soil characteristics are required to be determined first:

Liquid Limit Plastic Limit Plasticity Index (PI)

As water content increases, the shear strength of soil decreases.

Status changes with the increase in Water Content

Liquid Limit Soil is practically a liquid in this

state

Shows minimal shear strength

Defined as the moisture content required to close a distance of 0.5 inch along the bottom of a groove after 25 blows of the liquid limit device.

Plastic Limit Water content at which the soil

becomes plastic Less water content than liquid

limit Wide range of shear strengths

at plastic limit Defined as the moisture

content at which the soil begins to crumble when rolled into 1/8” dia threads

Plasticity Index (PI)

Difference between Liquid Limit and Plastic Limit

Important measure of plastic

behavior

Example:

Liquid Limit = 24%Plastic Limit 14 %

Plasticity Index = 24 – 14 = 10 %

In general….

PI Degree of Plasticity

0 Non-plastic1-5 Slightly plastic5-10 Low plasticity10-20 Medium plasticity20-40 High plasticity40+ Very high plasticity

Procedure for AASHTO Classification

Developed in 1929 as the Public Road Administration Classification Systemmodified by the Highway Research Board (1945)

COARSE-GRAINED SOIL (Sand & Gravel)

STEPS

Determine the percentage of soil passing the #200 sieve

Determine the percent passing the #10 and #40 sieves for Sub grouping.

Determine the liquid limit and plasticity index

THEN, determine soil group or subgroup from Table - 1

For coarse-grained soils (gravel and sand), determine the percent passing #10, #40, and #200 sieves.

CobbleGravelVery Coarse to Medium SandFine/Very Fine SandSilt/Clay

3 in#10#40

#200

#10

#40

#200

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Table-1 : AASHTO Classification for Coarse-grained Soil

FINE-GRAINED SOIL (Silt & Clay)

STEPS

Determine the percentage of soil passing the #200 sieve

Determine the liquid limit and plasticity index

THEN, determine soil group or subgroup from Table - 2

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Table-2 : AASHTO Classification for Fine-grained Soil

To evaluate the quality of a soil as a highway subgrade material, a number called the group index (GI) is also incorporated alongwith the groups and subgroups of the soil.

The group index is written in parenthesis after the group or subgroup designation.

GI is given by the following general Equation: GI = (F-35)[0.2+0.005(LL-40)] + 0.01(F-15) (PI-

10)

Group Index usually reflects the relative strength of material, where low values have greater shear strength

GROUP INDEX

e.g: A-7-5(9)

Determination of Group Index

Example ProblemExamples

Solution

SOFT ROCKThe rock which can be cut by the blade of a 200 HP Bull Dozer is classified as a Soft Rock.

MEDIUM ROCKThe rock which cannot be cut by the blade of a 200 HP Bull Dozer is classified as a Medium Rock.

HARD ROCKThe rock which cannot be cut by the Ripper of a 200 HP Bull Dozer is classified as a Hard Rock.

Engineering Classification of Rocks

SUB BASE

“SUB BASE is the structural layer of road pavement consisting of NATURAL or processed aggregates placed above the Sub grade” The material should comply with the following quality requirements:

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MATERIAL REQUIREMENTS FOR SUB BASE MATERIALS

GRADING REQUIREMENTS

US STANDARD SEIVE SIZE PERCENT PASSING

CLASS A CLASS B

2½” 100 -

2” 90-100 100

1” 50-80 55-85

⅜”- 40-70

No. 4 35-70 30-60

No. 10 - 20-50

No. 40 - 10-30

No. 200 2-8 5-15

QUALITY PARAMETERS

(i) CBR value @ 98% Compaction >50 %(ii) Los Angles Abrasion Value < 50 %(iii) Liquid Limit < 25(iv) Plasticity Index < 6(v) Oversize < 5 %(vi) Sand Equivalent = 25 min 28

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AGGREGATE BASE COURSE

“AGGREGATE BASE COURSE is the basic structural layer of flexible pavement consisting of a mixture of various sizes of crushed Aggregates ranging from 2” to material passing sieve #200”

The material should fulfill the following suitability parameters:

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MATERIAL REQUIREMENTS FOR AGGREGATE BASE COURSE

GRADING REQUIREMENT

US STANDARD SEIVE SIZE PERCENT PASSING

CLASS A CLASS B

2” 100 100

1” 60-80 75-95

⅜” 30-65 40-75

No. 4 25-55 30-60

No. 10 15-40 20-50

No. 40 8-20 12-25

No. 200 2-8 5-10

PHYSICAL PROPERTIES AND QUALITY PARAMETERS

i. Los Angles Abrasion Value < 40 %ii. SOUNDNESS with NA2SO4 <12 %iii. SAND EQUIVALENT < 45 %iv. L.L = 25 % (Max) v. P.I = 6% (Max)vi. CBR at 100 % compaction > 80 % vii. Laminated Particles <15% (By Volume)viii. Round particles < 10 %

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WATER BOUND MACADAM BASE

WBM is the base layer consisting of clean crushed stone

mechanically interlocked by rolling and voids filled with screening materials with assistance of water.

Fine aggregate (also called chocked materials) consists of

crushed stone screenings free from clay lumps with specified gradation.

Following are the quality requirements of WBM and screening

materials :

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GRADING REQUIREMENT

US STANDARD SEIVE SIZE

PERCENT PASSING

CLASS A CLASS B CLASS C

4” 100 - -

3½” 90-100 - -

3” - 100 -

2½” 25-60 90-100 100

2” - 25-75 90-100

1½” 0-15 0-15 35-70

1” - - 0-15

3/4 in 0-5 0-5 0-5

1/2 in - - -

FILLER MATERIAL OR SCREENINGS : Physical Requirements of Coarse Aggregate

SIZE % Passing 3/8” (9.5mm) 100 Los Angles Abrasion value = Max 45%No. 4 (4.75 mm) 85-100 L.L = 25 % (Max) No. 100 (0.15 mm) 10-30 P.I = 6 (Max) CBR >80% Flakiness Index = Max 15% Soundness with (Na2SO4 ) = Max 45%

MATERIAL REQUIREMENTS FOR WBM

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IDENTIFICATION OF INDIGENIOUS QUARRIES

Based on the above characteristics, the following local quarries have been identified for road materials on various District level:

Baisai (Peshawar) for aggregate and WBM

Zangali Khwar(Peshawar) for Sub Base material

Nizampur and Lawrencepur for Coarse Sand

Watarh nullah (Nowshera) for Sub Base material

Palai (Malakand Agency) for aggregate and WBM

Khyali River bed material for filter layers and Granular

backfill

Pir Sabaq (Nowshera) for aggregate and WBM

Sawal Dhair(Mardan) for aggregate and WBM

Pizzu (Sarai Naurang) for aggregate and WBM

Kurram River bed material(Bannu) for filter, Base & Sub

Base.

Margalla (Islamabad) for aggregate and WBM.

THANK YOU

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