Concrete Road Construction 1

8/3/2019 Concrete Road Construction 1

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CONSTRUCTION

OF

CONCRETE PAVEMENTS

PRIMARY STEPS

Surface preparation

Concrete mixing plant operations

Transport to paver

Preliminary steps prior to paving by machineries

Surface Preparation

Prepare subgrade for new pavement

Soil type

Moisture contentDensity

Preparing an existing pavement surfacefor overlay by removing top layer throughmilling, demolition

Remove pockets of unsuitable materials

Stabilize unsuitable soils


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Prepare granular subbase or basecourse

Similar to subgrade preparation

Usually higher density requirement

Cement-stabilized materials

Placed using slipform or asphalt equipment

Surface Preparation

Almost all PCC intended for pavementuse is ready mixed concrete

Mixing cement, aggregate, water andadmixtures

Plant Operations

Transport

Transportation to paving machinery from batchingfacility via truck mixer or non-agitating truck

Unload quickly upon arrival

Unload as close as possible to final placement

spot Quality control

Synchronisation rates of batching plant production,truck transport and paver

NEXT STEP PAVING

but reinforcement placement also common to both


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TWO KINDS OF PAVINGTECHNIQUES

FIXED FORM PAVING

SLIP FORM PAVING

manual

ALL functions to place reinforcement,strikeoff, spread, compact/consolidate,

finishing, texturing, cure

Fixed Form Paving

Different activitiesdone by separateindependentmachine traveling on

fixed forms (rails)

Slip Form Paving

Different activitiesdone by a single ornot more than 3machines travelingon crawlers


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Manual method - for small jobs

Fixed FormPaving Operations

Paving form is the mould Holds concrete in place

Establishes grade and alignment

Serves as tracks for paving equipment

Forms

Mould that determines

Pavement depth

Pavement width

Pavement smoothness

Made of steel (large job) or timber (small job with

less machineries) and has small side holes for

insertion of tie bars


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Typical SteelForm

Form Lock

Reinforcement

Dowel bars

-

-

-

-

-

Tie bars fixed by hand (FF) or t ie bar inserter(SP)

Mesh reinforcement, if required

Dowel BarsPlaced on a

Lean ConcreteBase in

Advance ofPCC Placement


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End Dump TruckDischarging PCC in Front

of a Paver

End Dump TruckDischarging PCC onto a

Spreader/Placer

InitialLeveling by

VibratingTruss Screed

Traveling CarriageScreed

Roller Screed

Roller screed consists of a steel tube that rotates up to250 rpm in the opposite direction of movement. Thetube strikes off PCC and pushes excess PCC forwardby the rolling action


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Small Hand-Operated Vibrator

Compaction1. Hand-operated vibrators.

2. Screed vibration.

Compacted Concrete in Steel Forms

Finishing and Texturing

Finishing using handfloats to eliminate

high/low spotsTexture types:

Longitudinal

Transverse

20 mm or less spacing

Random Spacing


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Mechaniseddragging artificial

turf

Manual draggingtexturing

Manual Texturing


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Curing

Curing carried out toprevent moistureloss. Ponding wateror cover slab withwater retainingmaterial.

Manually insert dowel bars into the constructionjoint at the end of the work day

Forms Removal Tie Bars Along a Longitudinal Joint

When one lane at a time is paved, tiebars are inserted at mid-slab depthand bent back until adjacent slab is

ready to be paved


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Critical Factors in FixedForm Paving - Ride Quality

Uniform grade - properly compacted Uniform subbase eliminate if subgrade CBR

above 15%

Forms meet specifications

Consistent mix, slump

Placement of reinforcing, dowel baskets

Timely delivery of concrete

Proper placement mix on grade

Critical Factors Fixed FormPaving - Ride Quality

Adequate vibration - compaction

Care in placement and vibration ofreinforcements, dowels

Proper machine adjustments

Steady machine progress

Avoid excessive finishing

Avoid excessive water on surface

Straightedge check of slab

Adequate cure

SLIPFORM

PAVING


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SLIPFORM PAVING

Uses low-slump PCC. Low-slump PCC is

necessary so that the fresh PCC is able to hold itsshape once the slipform paver has passed.

High productivity. Large jobs generally requirehigh production rates in order to be profitable.

Smooth riding surface. Automation and computercontrol allow slipform pavers to produce verysmooth riding surfaces

GENERAL SLIPFORM PAVINGPROCESS

EITHER a single

OR accomplished by 3 separate machineries:

spreader/placer; concrete paver; texturing and

curing machine

Slipform Paving Philosophy

To shape a material

byforcing it through a

mould.


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Extrusion Envelope

Profile Pan levels

concrete to right eleva

Tamper (150 strokes/min)pushes large aggregatebelow surfaceVibrator (group)

Strike Off remove excess

portion of auger-placed PCC

Concrete Head

Profile Pan Batter -Compression-Paver Uplift

FluidizedConcrete

Spread

by auger

Side Form Resistance Batter

Movement 1-2.5 m/min

Excess Concrete

Dowel bar inserter

Slipform

Compaction/consolidation Steel placement Form into a Shape Finish the Surface

SUBGRADE

Proper Compaction

Built to SpecifiedTolerances

Uniform Support

May be Stabilized

Place SUBBASE to Specified Tolerances

Enhance UNIFORMsupport for concrete layer

Working platform for concrete paving

Enhance smoothness

Reduce occurrence of mud pumping


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Track Line

Extend base onemeter beyondoutside edge ofpavement

Durable for pavingtrain

Keep it clean

Pavement Steel

Dowel bars

Tie bars

Reinforcing mesh

Continuous reinforcement

Placing Dowel Bars

Automatic

Manual


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Mechanical method

Hand placing ormanual method

Place PCC infront of paverusing a seriesof conveyorbelts, augersand strikeoff

devices

Discharging

Leveling and Vibration

Initial leveling by strike off screed

Compacting Concrete Mass

Series of vibrators at 7000-9000 VPM


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Vibration

Positioned so that their influence zone overlap by 50-75 mm

Finishing and Curing

As in fixed form paving

Dragging ArtificialTurf behind SP

Groove texture


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Spraying Curing Membrane

Curing

Uniform

Timely

THANK

YOU

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