nac pavements constructions

8/2/2011 Construction Project Management, NAC, Hyd

-- A. Ramesh A. Ramesh M.TECH, MITE (M.TECH, MITE (Ph.dPh.d))

Sr. Asst. Prof, CED,Sr. Asst. Prof, CED,

VNR VJIET, HYDVNR VJIET, HYD

PAVEMENT PAVEMENT CONSTRUCTION


OVERVIEW OVERVIEW

• Introduction on Pavements

• Construction of WBM

• Construction of WMM

• Construction of Bituminous Roads

• Failures in Aspects

• Closing Remarks


TYPES OF PAVEMENTSTYPES OF PAVEMENTS

•Un Surfaced

–Earthen roads

–Gravel roads

•Surfaced

–Bituminous Road

–Cement Concrete Road

•Un Conventional

–Block Pavement


• Flexible Pavements

–Earthen Roads

–Gravel Roads

–Bituminous Roads

• Rigid Pavements

–Reinforced Concrete

–Plane Concrete Roads

FURTHER CLASSIFICATION FURTHER CLASSIFICATION

OF PAVEMENTSOF PAVEMENTS


GRAVEL ROADSGRAVEL ROADS


BITUMINOUS PAVEMENTBITUMINOUS PAVEMENT


CROSS SECTION OFCROSS SECTION OF FLEXIBLE FLEXIBLE PAVEMENTPAVEMENT

Wearing course

Surface course

Base course

Sub-base course (GSB)

Drainage Layer

Subgrade


�Prime coat over granular base/ Tack coat

�Bituminous macadam (BM)

�Bituminous penetration macadam

�Built-up Spray Grout

�Dense Bituminous Macadam (DBM)

�Semi-dense Bituminous Concrete (SDBC)

�Bituminous Concrete (BC)

�Surface Dressing (SD)

�Open graded Premix surfacing

�Closed Graded Premix Surfacing

�Seal Coat

�Mastic Asphalt

�Seal

�Fog Spray

BASES AND SURFACE COURSES


Sub-base non-bituminous)

• Granular sub-base (GSB)

• Lime treated soil for improved subbase /subgrade

Base Course ( non-bituminous)

• Cement Treated soil sub-base/base

• Water Bound Macadam (WBM) base

• Crushed cement concrete sub-base/base

• Wet Mix Macadam (WMM) base

• Crusher run macadam base


Base Courses ( bituminous)

• Bituminous macadam (BM)

• Bituminous penetration macadam

• Built-up Spray Grout

• Dense Bituminous Macadam (DBM)

• Semi-dense Bituminous Concrete (SDBC)


• Surface Dressing (SD)• Open graded Premix surfacing

• Closed Graded Premix Surfacing

• Seal Coat

• Mastic Asphalt

• Chip Seal

• Fog Spray

Surface Course (bituminous) for high volume roads

•Bituminous Concrete (BC)

Wearing Course


Treatment in between two layers

• Prime coat over granular base

• Tack coat


CONSTRUCTION OF WBM PAVEMENT


SubSub--base/ base/ bases bases (non(non--bituminous)bituminous)

• Water Bound Macadam (WBM): work shall consists of clean, crushed aggregates mechanically interlocked by rolling and bonding together with screening, binding material where necessary and laid on a properly prepared subgrade/sub-base/existing pavement.


• Embankment Construction – if required

• Subgrade Construction

• Subgrade: Top 500 mm compacted thickness of native/borrow materialprepared as per standard conditions

Step:1


• Embankment- refers to a volume of earthen material that is placed and compacted for the purpose of raising the grade of a roadway (or railway) above the level of the existing surrounding ground surface.

• A fill refers to a volume of earthen material that is placed and compactedfor the purpose of filling in a hole or depression. material.

embankment


• EMBANKMENT

• Soil survey and identification of borrow areas

– Height of embankment : 0.6m/1m above the

H.F.L. or ground.

– Rolling by 150 to 300 mm compacted thickness

– Materials free of logs, stumps, roots, rubbish

or any other ingredients , LL<70 and PI<45

– Highly expansive clays only at the bottom of

the embankment, no such material placed nor

permitted to remain in the top 500mm


•For identification: Borrow soil sample to be brought at different depths.

•All clods broken into fine earth(<75 mm size) and spread confining to crown shape

•Select Moisture content that uses least effort for compaction and uniform sprinkling

•Commencement of rolling using 8-10 t roller

•Earth work: Loose thickness of soil layer should not exceed 20cm

EMBANKMENT CONSTRUCTION


Size of coarse material : <75 mm (embankment) and <50 mm when placed in the subgrade

Density requirements

Type of work Max. lab dry unit weight

Embankment (upto 3m) >15.2 kN/ cu.m

Embankment >3 m >16.0 kN/cu.m

Subgrade and earthen shoulders > 17.5 kN/cu.m


General Requirements

Min 95embankment

Min 97 .Subgrade and earthen shoulders

Relative compaction of max.lab dry density

Type of work

Construction

Setting out- Limits of embankment/ subgrade to be marked- pegs

Dewatering- If water is stagnant and possible to remove, remove

Stripping and Storing topsoil- 150 mm top soil- stripped and stockpiled

Compacting ground supporting embankment/subgrade-Original ground to be levelled – scarified, mixed with water and compact


To achieve max. dry density: as required

Diff. Between subgrade top and ground level< 500 mm and ground does not have 97 % relative compaction withrespect to dry density, ground to be loosened upto 500 mm below subgrade and watered and compacted in layers

Spreading materials in layers and bringing to appropriate moisture content

-to be spread in 200 mm compacted thickness- compacted and finished with motor grader.

-Moisture content to be checked prior to compaction. If required to be sprinkled by sprinkler capable of spreading uniform rate


Rolling

• motor grader for spreading

• Roller of 8-10T capacity vibratory roller

• Rolling begins from edges with the roller running forward and backward

• Progress gradually from the edges to centre overlapping uniformly each preceding rear wheel track by one half width

• Rolling continue until the road metal thoroughly keyed with no creeping of metal ahead of the roller

• Slight sprinkling of water

•Rolling not done when the subgrade is soft or yielding or when rolling causes a wave like motion in the subbaseor subgrade

• Checked transversely by template for camber

• Irregularities corrected


Vibratory roller


Sheep foot roller


Compaction requirements for Embankment and Subgrade

Type of work/material Relative compaction as

% max. lab dry density

1. Subgrade & earthen shoulders Not less than 97

2. Embankment Not less than 95

3. Expansive clays

a. Subgrade & 500 mm below subgrade

b. Remaining portion of embankment Not less than 90

Source: Specifications for Roadworks and ridges, MORTH, 2004


Specification for compaction of embankment


Compaction

Process by which soil particles are artificially rearranged and packed together into closer state of contact by mechanical means- to decrease porosity/voids- increase in density

Consolidation- gradual process of volume reduction by means of sustained loading


Compaction (dry unit weight)- increases the strength characteristics of soils, thereby increasing the bearing capacity of “foundations” constructed over them.

Maximum dry density - density at which the volume of air at a specific energy application is kept to a minimum,implying that the soil particles are rearranged to give a minimum volume of air at the compaction energy.

Soil compaction results in

· Higher Strength

· Reduced Settlement

· Reduced Permeability


Factors Affecting Compaction

1. Moisture Content

2. Soil Type

3. Effect of Compaction Effort

3.1 Amount of Effort

3.2 Nature of Effort: Load Duration and Area of Contact


Moisture Content

As the moisture content increases with the same compactive effort, the weight of the soil solids in a unit volume gradually increases.

Beyond a certain moisture content, any increase in the moisture content tends to reduce the dry unit weight because water takes up the spaces that would have been occupied by the solid particles.

Moisture content at which the maximum dry unit weight is attained - optimum moisture content (OMC), when the degree of saturation equals 100%.


Soil Type

Grain size, the shape of the soil grains, the amount and type of clay minerals present and the specific gravity of soil solids, has a great influence on the maximum dry unit weight and optimum moisture content.

Well graded course grain soils attains higher density and lower OMC compared to fine grain grained soils.


Effects of Soil Types on CompactionEffects of Soil Types on Compaction•The soil type-that is, grain-size distribution, shape of the soil grains, specific gravity of soil solids, and amount and type of clay minerals present.

Holtz and Kovacs, 1981; Das, 1998


Effect of Compaction Effort: Amount of CompactiveEffort

Compaction energy per unit volume (E) used for the standard proctor test is described as follows: E = [ (No of blows/layer) x (No of layers) x (weight of hammer) x (drop height of hammer) ] / Volume of the mould.

If the compactive effort per unit volume is altered, the moisture unit weight curve is also altered. As the compaction effort increases, the maximum dry unit weight of compaction also increases.

In addition, the increase in compaction effort also causes the optimum moisture content to decrease to some extent.


Effect of compaction energy on the compaction of a sandy clay.


test

1

2

3

2: Standard Proctor test 3: Modified Proctor test

Various types of compactionVarious types of compaction


Test EquipmentTest EquipmentStandard Proctor test equipment

Das, 1998


Variables of CompactionVariables of CompactionProctor established that compaction is a function of four variables:

(1)Dry density (ρd) or dry unit weight γd.

(2)Water content w

(3)Compactive effort (energy E)

(4)Soil type (gradation, presence of clay minerals, etc.)

)ft/lbft375,12(m/kJ7.592

m10944.0

)layer/blows25)(layers3)(m3048.0)(s/m81.9(kg495.2E

33

33

2

⋅

−

=

×=

Volume of mold

Number of

blows per

layer

Number of

layers

Weight of

hammer

Height of

drop of

hammer

× × ×

E =

For standard

Proctor test


Modified Proctor

Modified proctor Standard Proctor

No of Blows 55 55

No of Layers 5 3

Hammer weight 4.536kg 2.495kg

Drop Height 457.2mm 304.8 mm

Volume of mould 2280cm3 2280 cm3


General Compaction MethodsGeneral Compaction MethodsCoarse-grained soils Fine-grained soils

•Hand-operated vibration plates

•Motorized vibratory rollers

•Rubber-tired equipment

•Free-falling weight; dynamic compaction (low frequency vibration, 4~10 Hz)

•Falling weight and hammers

•Kneading compactors

•Static loading and press

•Hand-operated tampers

•Sheepsfoot rollers

•Rubber-tired rollers

Lab

ora

tory

Fie

ld

Vibration

•Vibrating hammer (BS)

(Holtz and Kovacs, 1981; Head, 1992)

Kneading


Subgrade Construction

• Preparation of subgrade- all operations before pavement

structure is laid

• Subgrade- Top 300mm of embankment

• Earth spread to a crown shape in straight reaches and bank profile in curve reaches

• Compacted to a 100% standard Proctor density

• Capping layer of 100 mm with Soil with CBR: 10 when clay is used as subgrade material

• Camber checking- camber board


Stabilization with lime and sand

Stabilization with coal ash

Stabilization with cement etc

Subgrade with stablized earth


Sub-base work with Gravel and Sand admixture


Step: 2

Construction of Sub-base/ bases (non-bituminous)

Water Bound Macadam (WBM): This work shall consists of clean, crushed aggregates mechanically interlocked by rolling and bonding together with screening, binding material where necessary and laid on a properly prepared subgrade/sub-base/existing pavement.


Compaction equipment

Smooth wheeled, vibratory, pneumatic, sheep foot rollers

Field Density measurement

Density measurement-

Nuclear density gauge (gamma rays)

sand replacement method


Nuclear density gauge

Gamma rays- in to soil and detector receive the rays back and density can be calculated.

Neutron radiation- emitted- neutrons lose energy due to collision with hydrogen atoms in soil, detector measures the neutrons that pass through soil and thus moisture content


Sand replacement method for field density


WBM- Materials used: Coarse aggregates (CA) : crushed/broken stone, crushed slag, over burnt brick/ laterite..etc

Specifications of crushed/ broken stone

Test Test Method Requirements

Los Angeles IS:2386(part IV) 40 % (max)

Impact IS: 2386(part IV) 30 % (max)

Combined flakiness+ elongation Index IS:2386(part I) 30 % (max)


Aggregate grading requirements: 3 grades (I, II and III)

WBM Gradation Grading No Size range IS sieve % weight passing

125 100

90 90-100

63 25-60

45 0-15

1

(100 mm)

90 to 45 mm

22.4 0-5

90 100

63 90-100

53 25-75

45 0-15

2

(75 mm)

63 to 45 mm

22.4 0-5

63 100

53 95-100

45 65-90

22.4 0-10

3 (75 mm)

53 to 22.4 mm

11.2 0-5


Screenings: To fill voids in the CA. Same material as CA/non-plastic material such as moorum/gravel (passing 75 micron does not exceed 10%)

Grading No Size range IS sieve % weight passing

13.2 100

11.2 95-100

5.6 15-35

A

13.2 mm

180 micron 0-10

11.2 100

5.6 90-100

B

11.2mm

180 micron 15-35


Binding material: Filler material to prevent raveling. PI< 6

CONSTRUCTION STEPS

Preparation of Foundation

Existing unsurfaced road

• Surface scarified and reshaped to the required grade, camber and shape

• Weak places strengthened; corrugations removed and depressions, pot holes etc. made good with suitable materials

•Existing black topped surface

• Furrows 50mm x 50mm at 1m intervals 45 0 to the central line


Lateral Confinement of Aggregates

• Construct side shoulders in advance

• Inside edges may be trimmed vertical

• Included area cleaned off all spilled materials

Spreading of Aggregates

• Uniformly and evenly spread

• Twisting motion to avoid segregation

• Proper profile by using templates

• Surface of the aggregate spread trued up and all high or low spots remedied by removing or adding aggregate


Rolling

• Immediately after spreading, compacted to the full width by rolling with either a three wheel power roller of 8- 10T capacity or an equivalent vibratory roller

• Rolling begins from edges with the roller running forward and backward

• Adding screenings simultaneously until edges compacted

• Progress gradually from the edges to centre overlapping uniformly each preceding rear wheel track by one half width

• Rolling continue until the road metal thoroughly keyed with no creeping of metal ahead of the roller

• Slight sprinkling of water


• Rolling not done when the subgrade is soft or yielding or when rolling causes a wave like motion in the subbase or subgrade

• Checked transversely by template for camber

• Irregularities corrected

• In no case use of screenings to make up depressions permitted

CONSTRUCTION STEPS- WBM


Application of Screenings

• Screenings shall be applied gradually over the surface to completely fill the interstices

• Screenings shall not be dumped in piles

• Spread uniformly in successive thin layers

• Spreading motion of the hand, shovels or a mechanical spreader

• Brooming of screening to fill


Sprinkling and Grouting

• Copiously sprinkling with water, swept and rolled

• Sprinkling, sweeping and rolling operation continued and additional screenings applied

• Till a grout is formed of screenings and water that will fill all voids and form a wave of grout ahead of the wheels of the roller


Application of Binding Material

• Suitable binding material applied at a uniform and slow rate in two or more successive thin layers

• Copiously sprinkled with water and resulting slurry swept in with hand brooms or mechanical brooms so as to fill the voids properly

• Surface then rolled by a 8-10 tonne roller

• Spreading of binding material, sprinkling of water, sweeping with brooms

• Rolling continue until the slurry that is formed forms a wave ahead of wheels of moving roller


Setting and Drying

• Allowed to dry over night

• Next morning uneven spot filled with screening or binding material sprinkled with water if necessary

• Rolled

• No traffic allowed on the road until this has set


WBM- rural road


Wet Mix Macadam (WMM)WMM- : This work shall consists of laying and compacting clean, crushed, graded aggregate and granular material, premixed with water to a dense mass on properly prepared subgrade/sub-base/existing pavement (75 to 200 mm thickness).

Materials used: Coarse aggregates (CA) : crushed/broken stone, Specifications of crushed/ broken stone


Aggregate grading requirements: I grade

IS sieve % weight passing

53 100

45 95-100

26.5 -

22.4 60-80

11.2 40-60

4.75 25-40

2.36 15-30

600 micron 8-22

75 micron 0-8


Construction steps:· Preparation of foundation: As per specification with required camber. Irregular surface to rectify by profile corrective course

· Preparation of lateral confinement of aggregates: laying adjoining shoulder material.

· Preparation of mix: Approved mixing plant; OMC as per IS:2720 (part:8) after replacing the aggregate fraction retained on 22.4 mm sieve with 22.4-4.75 mm. No segregation is allowed.

Spreading of mix: uniform spreading- paver finisher (loading hopper and suitable distribution mechanism, tamping and vibrating arrangement for initial compaction) /motor grader( blades have hydraulic control for adjustments)


• Compaction: uniformly compacted to the full depth with suitable roller. 100 mm thick- smooth wheel roller (80-100 kN); 200 mm thick – vibratory roller (80-100kN-static weight); speed-5kmph. Edge to centre- uniform rolling. 98% max. dry density. Irregularies during rolling where 12 mm depth- surface should be loosed and premixed material is added and roller again.

Setting and drying: 24 hours and allowed for traffic


Construction of Bituminous layers


References:

MORTH- Specifications for roads and bridge works, 2004

Construction of Hot Mix Asphalt Pavements, Ms series 22, Asphalt Institute


Some of the bituminous layers

·

Prime coat over granular base

Tack coat

Bituminous macadam (BM)

Bituminous penetration macadam

Built-up Spray Grout

Dense Bituminous Macadam (DBM)

Semi-dense Bituminous Concrete (SDBC)

Bituminous Concrete (BC)

Surface Dressing (SD)

Open graded Premix surfacing

Closed Graded Premix Surfacing

Mastic Asphalt

Fog Spray

Seal Coat


� To plug the capillary voids

� To coat and bond loose materials on the surface

� To harden or toughen the surface

� To promote adhesion between granular and the bituminous layer

PURPOSE OF PRIMING


� Depends on porosity

� Depends on type of bitumen viscosity

� MORTH specifies emulsion (IS8887)

� Sub zero temperature cutback (IS217)

Materials


� Self heating arrangement

� Suitable pumping

� Compressors

� Spraying biers with nozzles

� Speed of the vechicle

� Opening of nozzle

EQUIPMENT


Application of single coat of low viscosity

bitumen on a porous granular surface

Prime Coat


Purpose of Tack Coat:

� To ensure a bond between the new construction and the old surface

Use of Cutback:

� It should be restricted for sites at subzero temperatures or for emergency applications

TACK COAT


� Single coat low viscosity bituminous binder

� To provide bond between old & new surface

• Materials

• Emulsions → (IS – 8887: 2004)

• Cutback → (IS – 217)

(in sub-zero temperature)


� Weather & seasonal limitations

bituminous primer should not be applied on

a wet surface or during dust

strom,weather is foggy rainy and windy

� when emulsion is used then surface can be

damp but no standing water

CONSTRUCTION


� Shall be clean and free from dust, dirt and any extraeous material

� Surface shall be swept clean with a mechanical and high pressure air jet

PREPARATION OF BASE


Typical Application

Application of Tack Coat


Application of Tack Coat

ProperCoverage


WRONG PRACTICE OF TACK COATWRONG PRACTICE OF TACK COAT


Bituminous Concrete pavement construction


Bituminous ConcreteBituminous Concrete

• Used for wearing / profile corrective course

• Work may require single or multiple layers

• Thickness of a single layer is

25-100mm


FAILURES IN PAVEMENT FAILURES IN PAVEMENT

• Major are two in category

– Fatigue

• Fatigue cracking - series of interconnecting cracks on the pavement surface caused by repeated traffic loading

• Fatigue occurs at places of bituminous layer

– Rutting

– It is called permanent deformation because it represents an accumulation of small amounts of unrecoverable deformations

– under the channelized repeated wheel loads


FATIGUE FATIGUE


Fatigue crackingFatigue cracking


RUTTINGRUTTING

Rutting in wheel paths


Reflection cracking at PCC Reflection cracking at PCC JointsJoints


• Subgrade - Core Cutter Method or Sand Replacement Method

• Overlays - Benkelman Beam Deflection

» In combination with roughness (5th towed wheel bump Integrator)

FIELD EVALUATION FIELD EVALUATION


SAND REPLACEMENT SAND REPLACEMENT


BITUMEN EXTRACTION BITUMEN EXTRACTION


FIFTH TOWED WHEEL BUMP FIFTH TOWED WHEEL BUMP INTEGRATOR INTEGRATOR


Road work is under progress under Road work is under progress under PMGSYPMGSY


Strengthening of rural infrastructure through construction of roads under PMGSY


Connectivity with urban areas through road constructed under PMGSY


CLOSING REMARKSCLOSING REMARKS

All roads need maintenance

Several types of maintenance works

Timely maintenance measures avoids severe damage

and saves lot of money

Quality control measures during selection of pavement

materials and construction always lessen the

maintenance


QUESTIONS AND DISCUSSIONQUESTIONS AND DISCUSSION

nac pavements constructions

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