BITUMINOUS CONCRETE
BITUMINOUS CONCRETE( BC) IS USED FOR WEARING COURSE AND PROFILE CORRECTIVE COURSES.
BC IS GENERALLY LAID IN A SINGLE LAYER ON A PREVIOUSLY PREPARED BITUMINOUS BOUND SURFACE.
THE THICKNESS OF A SINGLE LAYER OF BC SHALL BE 30MM,40MM, AND 50MM.
MATERIALS USED IN BITUMINOUS CONCRETE:-
BITUMEN
HYDRATED LIME
COARSE AGGREGATE
FINE AGGRAGATE
MATERIALS
1. BITUMEN
THE BITUMEN SHALL BE VISCOSITY GRADED PAVING BITUMEN COMPLYING WITH INDIAN STANDARD SPECIFICATION FOR PAVING BITUMEN, IS:73.
THE GRADE OF BITUMEN TO BE USED WOULD DEPEND UPON THE CLIMATIC CONDITIONS AND THE TRAFFIC.
SELECTION CRITERIA BASED ON CLIMATIC CONDITIONS
2. COARSE AGGREGATES
THE COARSE AGGREGATE SHALL CONSIST OF CRUSHED ROCK, CRUSHED GRAVEL, OR OTHER GRAVEL OR OTHER HARD MATERIAL RETAINEDON2.36MM SIEVE.
IT SHALL BE CLEAN, HARD, DURABLE, AND CUBICAL IN SHAPE, FREE FROM DUST AND SOFT ORGANIC AND OTHER DELETERIOUS SUBSTANCES.
WHERECRUSHEDGRAVELIS PROPOSED FOR USE AS AGGREGATE NOT LESS THAN 95% BY WEIGHT OF THE CRUSHED MATERIAL RETAINED ON THE 4.75MM SIEVE SHALLHAVEAT LEAST TWO FRACTURED FACES.
PHYSICAL REQUIREMENTS FOR COARSE AGGREGATE FOR BITUMINOUS CONCRETE
IF THE MIN. RETAINED TENSILE TEST STRENGTH FALLS BELOW 80%, USE OF AN ANTI-STRIPPING AGENT IS RECOMMENDED TO MEET THE REQUIREMENT.
IMPROVE THE ADHESION OF THE BITUMEN FILM ON THE SURFACE OF THE AGGREGATES. MIXED WITH THE BINDER, THEY LOWER THE SURFACE TENSION OF THE BITUMEN.
3. FINE AGGREGATES
IT SHALL CONSIST OF CRUSHED OR NATURALLY OCCURRING MATERIAL, OR A COMBINATION OF THE TWO, PASSING 2.36 MM SIEVE AND RETAINED ON THE 75MICRON SIEVE.
THEY SHALL BE CLEAN, HARD, DURABLE, DRY, AND FREE FROM DUST AND SOFT OR FRIABLE MATTER, ORGANIC OR OTHER DELETERIOUS MATTER.
NOTES:-
NATURAL SAND SHALL NOT BE ALLOWED IN THE BINDER COURSE.
HOWEVER, NATURAL SAND UP TO 50% OF THE FINE AGGREGATES MAY BE ALLOWED IN BASE COURSES.
SAND EQUIVALENT VALUE >50 {IS:2720(PART 37)}
THE PLASTICITY INDEX OF THE FRACTION PASSING THE 0.425MM SIEVE<4 {IS:2720(PART 5)}.
3. FILLER:-
THE FILLER SHALL CONSIST OF FINELY DIVIDE MINERAL MATTER SUCH AS ROCK DUST, HYDRATED LIME, OR CEMENT APPROVED BY THE ENGINEER.
THE FILLER SHALL BE GRADED WITHIN THE LIMITS INDICATED IN THE TABLE BELOW:-
NOTES:-
THE FILLER SHALL BE FREE FROM ORGANIC IMPURITIES.
PLASTICITY INDEX NOT GREATER THAN 4
THE PI REQUIREMENTS SHALL NOT APPLY IF THE FILLER IS CEMENT OR LIME.
WHERE THE AGGREGATES FAIL TO MEET THE REQUIREMENTS OF THE WATER SENSITIVITY TEST THEN 2% BY WEIGHT OF AGGREGATES, OF HYDRATED LIME SHALL BE USED.
AGGREGATEGRADING&BINDERCONTENT
WHEN TESTED IN ACCORDANCE WITH THE WET GRADING METHOD, THE COMBINED GRADING OF COARSE AND FINE AGGREGATE AND FILLER SHALL FALL WITHIN THE LIMITS.
AGGREGATE GRADING & BINDER CONTENT SIEVE ANALYSIS FOR GRADING I & II
MIX DESIGN BITUMINOUS CONCRETE
THE BITUMEN CONTENT REQUIRED SHALL BE DETERMINED BY FOLLOWING THE MARSHALL MIX DESIGN PROCEDURE
THE FINES TO BITUMEN(F/B)RATIOBY WEIGHT OF TOTAL MIX SHALLRANGE FROM 0.6 TO 1.2.
REQUIREMENTS OF BITUMINOUS CONCRETE
BINDER CONTENT
THE BINDER CONTENT SHALL BE SELECTED TO OBTAIN 4 PERCENT AIR VOIDS IN THE MIX DESIGN.
WHEREMAXIMUMSIZE OF THE AGGREGATE IS MORE THAN26.5 MM, THE MODIFIED MARSHALL METHOD USING 150 MM DIAMETER SPECIMEN SHALL BE USED.
THIS METHOD REQUIRES MODIFIED EQUIPMENT AND PROCEDURES.
WHEN THE MODIFIEDMARSHALL TEST IS USED, THE SPECIFIED MINIMUM STABILITY VALUE SHALL BE MULTIPLIED BY 2.25, AND THE MINIMUM FLOW SHALL BE 3 MM.
JOB MIX FORMULA
THE CONTRACTOR SHALL SUBMIT THIS TO THE ENGINEER FOR APPROVAL AT LEAST 21 DAYS BEFORE THE START OF WORK:-
SOURCE & LOCATION MATERIAL
BINDER TYPE & % BY WEIGHT OF TOTAL MIX
COARSE AGGREGATE/FINE AGGREGATE/FILLER MATERIAL AS % BY WEIGHT OF TOTAL AGGREGATE
PASSING EACH SIEVE FOR MIXED AGGREGATE
ALL RESULTS OF THE MARSHALL TEST
TEST RESULT OF PHYSICAL CHARACTERISTICS
MIXING TEMP. & COMPACTING TEMP.
PERMISSIBLE VARIATIONS IN THE ACTUAL MIX FROM THE JOB MIX FORMULA
LAYING
WEATHER AND SEASONAL LIMITATIONS: BITUMINOUS MACADAM SHALL NOT BE LAID:
IN THE PRESENCE OF STANDING WATER ON THE SURFACE,
WHEN RAIN IS IMMINENT AND DURING RAINS, FOG, OR DUST STORMS,
WHEN THE BASE /BINDER COURSE IS DAMP,
WHEN THE AIR TEMPERATURE ON THE SURFACE ON WHICH IT IS TO BE LAID IS LESS THAN 100 C,
WHEN THE WIND SPEED AT ANY TEMPERATURE EXCEEDS 40 KM/H AT A 2-METER HEIGHT.
TACK COAT:-
IT IS A VERY THIN APPLICATION OF DILUTED BITUMEN EMULSION.
IT CONSISTS OF THE LOW VISCOSITY OF BITUMINOUS MATERIAL TO EXISTING BITUMINOUS, CEMENT CONCRETE, OR PRIME GRANULAR SURFACE.
IT IS USED TO ASSURE A BOND BETWEEN THE PAVED SURFACE AND THE NEW COURSE.
MATERIALS:-
#THE BINDER USED ARE:-
CATIONIC BITUMEN EMULSION (RS-1)
LOW VISCOSITY PAVINGBITUMEN (VG-10)
CUT-BACK BITUMEN (RC-70) – ONLY FOR SITES ATSUB-ZERO TEMP. OR AS DIRECTED BY AN ENGINEER
CONSTRUCTION OPERATIONS FOR TACK COAT EQUIPMENT:-
SELF-PROPELLED OR TOWED BITUMEN PRESSURE SPRAYER EQUIPPED FOR SPRAYING THE MATERIALUNIFORMLYAT SPECIFIED RATE& TEMPERATURE.
HAND SPRAYING SHALL NOT BE ALLOWED EXCEPT IN SMALL AREAS ACCESSIBLE TO THE DISTRIBUTOR.
CONSTRUCTION OPERATION FOR TACK COAT PREPARATION OF ROAD SURFACE:-
THE SURFACE TO BE PRIMED SHALL BE KEPT CLEAN BY A POWER OR MECHANICAL SWEEPER & MADE FREE FROM DUST.
APPLICATIONS OF BITUMINOUS PRIMER:-
# IT DEPENDS UPON THE
TYPE OF EQUIPMENT USED
SIZE OF NOZZLE
PRESSUREATSPRAYBARS
SPEED OF FORWARDING MOVEMENT
NO HEATING OR DILUTION OF RS1 BITUMEN EMULSION & SHALL BE PERMITTED AT SITE
# SPRAYING TEMPERATURE:-
BITUMINOUS EMULSION – 20-70 °C
CUTBACK – 50-80 °C
RATE OF APPLICATION OFTACKCOAT
QUALITY CONTROL AND TEST FREQUENCY FOR TACK COAT
MEASUREMENTS FOR PAYMENT:-
TACK COAT SHALL BE MEASURED IN TERMS OF SURFACE AREA OF APPLICATION IN SQUARE METER
MIXING & TRANSPORTATION OF MIX
MIXING, LAYING, AND ROLLING TEMPERATURES FOR BITUMINOUS CONCRETE
SPREADING:-
EXCEPT IN AREAS WHERE PAVER CAN NOT HAVE ACCESS, BITUMINOUS MIXTURE SHALL BE SPREAD, LEVELLED, AND TAMPED BY A SELF-PROPELLED HYDROSTATIC PAVER FINISHER PREFERABLY EQUIPPED WITH A SENSOR.
AS SOON AS POSSIBLE AFTER ARRIVAL AT THE SITE THE ASPHALT MIX SHALL BE SUPPLIED CONTINUOUSLY TO THE PAVER AND LAID WITHOUT DELAY.
THE RATE OF DELIVERY OF MATERIAL TO THE PAVER SHALL BE REGULATED TO ENABLE THE PAVER TO OPERATE CONTINUOUSLY.
THE TRAVEL RATE OF PAVER AND THE METHOD OF OPERATION SHALL BE ADJUSTED TOENSUREEVEN AND UNIFORM FLOW OF BITUMINOUS MATERIAL ACROSS THE SCREED, FREE FROM DRAGGING, TEARING, AND SEGREGATION
WHEN LAYING BITUMINOUS CONCRETE NEAR THE EXPANSION JOINT, THE MACHINE LAYING SHALL BE STOPPED ABOUT 300 MM SHORT OF THE JOINT.
THE REMAINDER OF THE PAVEMENT UP TO THE JOINT AND THE CORRESPONDING AREA BEYOND IT SHALL BE LAID MANUALLY.
COMPACTION:-
THE INITIAL OR BREAKDOWN ROLLING SHALL BE DONE WITH AN 8 TO 10 TONNES DEAD WEIGHT SMOOTH WHEEL ROLLER THE INTERMEDIATE ROLLING SHALL BE DONE WITH 8 TO 10 TONNES DEAD WEIGHT OR VIBRATORY ROLLER WITH AN AMPLITUDE OF 0.3MM TO 0.8 MM AND FREQUENCY BETWEEN 30 TO 50 HZ. OR WITH A PNEUMATIC ROLLER OF 12 TO 15 TONES, WITH A TIRE PRESSURE OF AT LEAST 0.56 MPA.
THE FINISHED ROLLING SHALL BE DONE WITH 6 TO 8 TONNES SMOOTH WHEEL ROLLER.
ROLLING SHALL CONTINUE UNTIL AT LEAST 98% OF THE LAB DENSITY OBTAINED IN THE MARSHALL MOULD MADE USING APPROVED GRADATIONANDBITUMENCONTENTISACHIEVED
NOTES:-
THE BC SHALL BE ROLLED IN THE LONGITUDINAL DIRECTION WITH THE ROLLER AS CLOSE TO THE PAVE AS POSSIBLE.
THE OVERLAP ON SUCCESSIVE PASSES SHOULD BE AT LEAST ONE-THIRD OF THE WIDTH OF THE REAR ROLL OR IN THE CASE OF PNEUMATIC WHEELED ROLLERS, AT LEAST THE NOMINAL WIDTH OF 300MM.
THE ROLLER SHOULD MOVE AT A SPEED OF NO MORE THAN5 KM/HOUR. THE ROLLER SHALL NOT BE PERMITTED TO STAND ON PAVEMENT, WHICH HAS NOT BEEN FULLY COMPACTED
MEASUREMENTS FOR PAYMENT:-
BITUMINOUS CONCRETE SHALL BE MEASURED AS FINISHED WORK EITHER IN CUBIC METRES, TONNES OR BY SQUARE METER AT A SPECIFIED THICKNESS AS INDICATED IN THE DRAWING, CONTRACT, DOCUMENTS OR AS SPECIFIED BY THE ENGINEER-IN CHARGE.