ASPHALT, ASPHALT CONCRETE, BITUMINOUS CONCRETE LAYERS

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ASPHALT, ASPHALT CONCRETE, BITUMINOUS CONCRETE LAYERS

Bituminous Concrete layer

ASPHALT, ASPHALT CONCRETE, BITUMINOUS CONCRETE LAYERS

What is ASPHALT CONCRETE ?:➤

➤Basically Asphalt Concrete is Just Aggregate Coated With Asphalt Cement.. and Then Compacted.

There Are Three Basic Elements To The Compacted Mix.

➱1-Aggregate Particles,

➱2-Asphalt Cement,

➱3-Air Voids,

What is meant by bituminous concrete?
What is the difference between bituminous concrete and asphalt?
What is BM and BC?

INTRODUCTION ➤

➤Asphalt is a Mixture of Bitumen of Tar with aggregate,

➤Bitumen Is an Extract of Petroleum Crude,

➤Crude Oil is formed by the decomposition of dead marine microorganisms in the absence of air or oxygen,

➤Bitumen is waste collected during the distillation of petroleum crude,

ACTIVITIES IN ASPHALT CONCRETE WORK ➤

➤Dense Bituminous Macadam( DBM) Or Bituminous Macadam(BM),

➤Bituminous Concrete(BC) OR Semi Dense Bituminous Concrete(SDBC),

➤Prime Coat – SS 1

➤Tack Coat -RS 1

What is DBM and BC?

What is DBM and BC in road construction?
What is BC layer in road construction?

MATERIALS IN ASPHALT CONCRETE ➤

➤Aggregate,

➤Bitumen,

➤Mineral filler (Lime/Cement/Rock Dust),

➤ Anti-striping Agent,

Asphalt Concrete Materials

MATERIALS PROPERTIES(AS PER BELOW TABLES)

PAVING OPERATION in ASPHALT CONCRETE ➤

CHECKS BEFORE PAVING(PRE-PAVING ACTIVITY)➱

➤Check The Trucks Are Adequate,

➤Check The Production capacity and Paving Capacity is Matching,

➤Check The Rollers Are Adequate,

➤Check The string line, Thermometer, and other tools are ready,

➤Check the screed Of the Paver is Heated As much as Required, (Maximum up to mix Temperature),

➤Check The screed is Blocked to the required loose thickness,

➤Check The Cold Joints are cleaned and applied with a tack coat,

➤Check The Cleaning Should Be done Properly Before Applying tack coat, The Surface Should be Free From loose particles, Dust, Or any other Deleterious Material,
➤Paver Level Sensor To be Set For Required Level Given Of String Wire Or Average Beams,

CHECKS DURING PAVING ➱

➤Tack Coat Should be Applied Uniformly With the rate of Spray of 2.5 to 3 kg per 10 Square meter area,
➤Total Area Should Be covered With Tack Coat,
➤Start The Unloading Of the Truck into the paver, After checking The Temperature Of Mix,
➤Loose Thickness Should Be Checked With a Thickness Gauge Regularly in some Interval of Time, and Length,
➤Check The Camber with line rope, taper.
➤If any Segregated area is Found spread the fines with shovels prior to rolling,
➤Check for Rolling Should Be done As per the Rolling pattern,

SURFACE FINISH ➤

➤The tolerance in level should be in between +/- 6 mm,
➤The Core Density should be 92 % of Lab GMM.
➤Road Unevenness index shall be less than 2000 mm per kilometre for road works,
➤The Mix Binder Content shall be +/- .3% of Designed OBC,
➤Surface Regularity DBM, BC shall be +/- 6 mm , +/- 3 mm,

TRANSVERSE JOINT MATCHING➤

➤The Joint Should be rolled parallel to the joint,

➤These joints are to be Rolled without vibrations,

LONGITUDINAL JOINTS MATCHING➤

➤Compact The joint during breakdown Rolling,

➤If two pavers are Working in echelon ,then the roller in the second lane shall roll the joint,

PLANT OPERATIONS For ASPHALT CONCRETE➤

CHECKS DURING PRODUCTION➤

➤Feed The aggregate to the plant to get the design mix,
➤Maintain The Bitumen Temperature at 150 degrees Celsius,
➤Maintain the aggregate Temperature at 160 to 170 degree Celsius,
➤Ensure The Mix temperature should be Between 140 to 150 degree Celsius,
➤Clean the Vehicles Neatly,
➤Load The mix onto Trucks and Cover it with Tarpaulins and Haul to site,
➤ Check The temperature at plant, and site and record it,

ROLLING PATTERN➤

➱The Rolling process should start 12 to 15 inches from the lower unsupported edge as the un-compacted edge provides the initial confinement during the first pass, thus minimizing lateral movement of the mix. ⇩
➱Succeeding pass should move to the edge once the central portion of the spread is compacted to some degree because the mix will support the roller and allow the edge to be compacted without lateral movement,

REQUIRED MACHINES For ASPHALT CONCRETE➤

Some important machines are required for the Laying of Asphalt concrete, Bituminous Concrete Layer ,

1➮Paver machine

Paver machine

2➮Tendem Rollers

Tandem Roller

3➮Pneumatic Tyre Rollers

PNEUMATIC TYRE ROLLER➤

What is a pneumatic tyre roller?

➤The Pneumatic tyre roller(PTR) is tire mounted roller with having smooth tyre surface,
➤It’s Weight can be adjusted according to the requirement(Generally 16 to 18 mt for bituminous layers rolling is used),
➤It is used for Compaction and kneading action,
➤Longitudinal movement of the mix doesn’t take place unless the dia. is very low,
➤Horizontal forces are minimized with the use of larger diameters.
➤The movement of the mix under the tyre tends to be lateral,
➤The humps created during breakdown are of no significance and can be cleared in subsequent passes,
➤Under normal conditions, when the roller is on top of a firm mat it has no horizontal thrust as the tire flattens on the bottom which permits a 100 % vertical force,

PTR

CONDITIONS FOR PNEUMATIC TYRE ROLLERS TO BE EFFECTIVE➤

➤The most effective pressure is the highest pressure that can be used without overstressing the mix,

➤Pressure for normal Highway work when the tyre is hot is 90 psi and 70-75 psi when the tyres are cold,

➤Nine A wheel roller is used commonly,

➤Weight per wheel should not exceed 2000 to 3000 pounds,

➤Rim diameter for tyre -20 inches,

➤Tire width – 9 or 11 inches,

➤While compacting water should not be used on the tyres,

SUMMARY TABLE OF INFLUENCES OF COMPACTION➤

ITEMS	EFFECTS	CORRECTIONS
AGGREGATE
➮Smooth Surfaced ➮Rough Surfaced ➮Unsound ➮Absorptive	➮Low inter-particle friction ➮High inter-particle friction ➮Breaks under steel-wheeled rollers ➮Dries-Mix difficult to compact	➮Use light rollers, Low mix Temperature, ➮Use Heavy Rollers ➮Use Sound Aggregates, Use pneumatic rollers, ➮Increase asphalt in mix
ASPHALT
Viscosity
➮High ➮Low	➮Particles Movement Restricted ➮Particles moves easily during compaction	➮Use heavy rollers, Increase temperature, ➮Use light rollers
QUALITY
➮High ➮Low	➮Unstable and plastic under roller ➮Reduce Lubrication – difficult compaction	➮Decrease asphalt in mix ➮Increase asphalt in mix,Use heavy rollers
MIX
➮Excess Coarse aggregate ➮Over-sanded ➮Too much filler ➮Too light filler	➮Harsh mix – difficult to compact ➮Too workable – difficult to compact ➮Stiffens Mix-difficult to compact ➮Low cohesion – mix may come apart	➮Reduce coarse aggregate,Use heavy rollers ➮Reduce sand in mix,Use light rollers, ➮Reduce filler in mix,Use heavy rollers ➮Increase filler in mix
MIX TEMPERATURE
➮High ➮Low	➮Difficult to compact-mix lacks cohesion ➮Difficult to compact-mix to stiff	➮Decrease mixing temperature ➮Increase mixing temperature
COURSE THICKNESS
➮Thick lifts ➮Thin lifts	➮Hold heat – more time to compact ➮Lose heat – Less time to compact	➮Roll normally ➮Roll before mix cools, Increase mix temperature
WEATHER CONDITIONS
➮Low air temperature ➮Low surface temperature ➮Wind	➮Cools mix rapidly ➮Cools mix rapidly ➮Cools mix-crusts surface	➮Roll before mix cools ➮Increase mix temperature ➮Increase lift thickness

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