GSB MATERIALS
MATERIALS TO BE USED:- NATURAL SAND, CRUSHED GRAVEL, CRUSHEDSTONE, CRUSHED SLAG OR THE COMBINATION OF THESE DEPENDINGUPON GRADING REQUIRED.
BRICK METAL, KANKAR & CRUSHED CONCRETE SHALL BE PERMITTED IN LOWER SUB-BASE.
THIS WORK SHALL CONSIST OF LAYING & COMPACTING WELL GRADED MATERIALS ON PREPARED SUBGRADE IN ACCORDANCE WITH THE REQUIREMENTS OF THESE SPECIFICATIONS & CROSS-SECTION SHOWN IN THE DRAWING OR AS INDICATED BY ENGINEER-IN-CHARGE.
THE MATERIALS SHALL BE LAID IN ONE OR MORE LAYER AS LOWER SUB BASE & UPPER SUB BASE.
GRADING FOR GRANULAR SUB-BASE MATERIALS
NOTES:-
1. GRADING III & IV SHALL PREFERABLY BE USED AS LOWER SUB- BASE.
2. GRADING V &VI SHALLBE USED AS A SUB-BASE-CUM- DRAINAGELAYER.
3. GRADING TO BE ADOPTED SHALL BE SPECIFIED IN PROJECT
4. WHEN THE SUB-BASE IS IN 2 LAYERS i.e. LOWER & UPPER SUB- BASETHICKNESS OF THE LAYER SHALLNOT BE LESS THAN 150MM.
5. IF THE WATER ABSORPTION OF THE AGGREGATES > 2% THE AGGREGATES SHALL BE TESTED FOR WET AGGREGATE IMPACTVALUE(AIV)
PHYSICAL REQUIREMENTS FOR MATERIALS FOR GRANULAR SUB-BASES
CONSTRUCTION OPERATIONS
PREPARATIONOF SUB-BASE:-
PRIOR TO THE LAYING OF SUB-BASE FOLLOWING APPLICATIONS SHALL BE COMPLETELY FINISHED:-
SUBGRADE SHALLBE PREPARED BY REMOVING ALL VEGETATION & OTHER EXTRANEOUS MATERIALS.
LIGHT SPRINKLING OF WATER
ROLLED WITH 2 PASSES OF 80-100KN SMOOTH WHEELED ROLLER
SPREADING & COMPACTINGOF SUB-BASE:-
1. SUB-BASE MATERIALS & WATER SHALL BE MIXED MECHANICALLYBY SUITABLE MIXER.
2. CONTROLLED ADDITION OF WATER SHALL BE DONE TO OBTAINHOMOGENEOUS & UNIFORM MIX.
3. THE MIX SHALL SPREAD ON THE PREPARED SUB-GRADE WITH THE HELPOF MOTOR GRADER OF ADEQUATE CAPACITY. (HAVINGHYDRAULIC CONTROLS FOR MAINTAING SLOPES )
4. MOISTURE CONTENT OF THE MIX SHALL BE CHECKED IS:2720(II).
5. AT THE TIME OF COMPACTION IT IS FROM 1-2% BELOW THE OPTIMUMMOISTURE CONTENT.
6. AFTER MIXING ROLLING SHALL BE DONE BY APPROVED ROLLER.
SPREADING & COMPACTING OF SUB-BASE:-
•IF THE THICKNESS OF COMPACTED LAYER DOESN’T EXCEEDS 100MM:- 80-100KN SMOOTH TYRE ROLLER
•FOR COMPACTING SINGLE LAYER UPTO 200MM- VIBRATORY ROLLER
7. ROLLING SHALL BE COMMENCED FROM THE LOWER EDGES & PROCEEDS TO WARDS THE UPPER EDGE(CROWN).
8. EACH PASS OF THE ROLLER SHALL UNIFORMLY OVERLAP NOT LESS THAN 1/3RD OF THE TRACK MADE IN THE PRECEDING PASS.
9. ANY HIGH SPOTS OR DEPRESSIONS SHALL BE CORRECTED BY REMOVING & ADDING MATERIALS.
10. THE SPEED OF THE ROLLER SHALL NOT EXCEED 5KM/HR.
11. ROLLING SHALL BE CONTINUED TILL THE DENSITY ACHIEVED IS AT LEAST 98% OF THE DRY DENSITY FOR THE MATERIAL.
12. ALL LOOSE, SEGREGATED OR DEFECTIVE AREAS SHALL BE MADE GOOD TO THE FULL THICKNESS OF THE LAYER AND RE-COMPACTED.
MEASUREMENTS FOR PAYMENT:-
GRANULAR SUB-BASE SHALL BE MEASURED AS FINISHED WORK IN POSITION IN CUM.
NO EXTRA PAYMENT SHALL BE MADE FOR THE PROTECTION OF EDGES OF GRANULAR SUB-BASE EXTENDED OVER THE FULL FORMATION SHALL BE CONSIDERED INCIDENTAL.
