METHODOLOGY OF SEMI DENSE BITUMINIOUS CONCRETE (SDBC)

 

         METHODOLOGY OF SDBC

SDBC is used as wearing course in road construction depending upon enviormental coodition & type of road.Mostly used in smaller roads .This course directly laid on WMM  (Wet Mix Macadam).             

 

SCOPE:    This work shall consist of construction in a single course of Semi Dense Bituminous Concrete (SDBC) binder / wearing course a previously prepared bituminous base to the requirement of the specifications.

 

MATERIAL:       

(i) Binder:  -         The Bitumen shall be paving Bitumen of suitable penetration grade 80/100 as per IS : 73. (IS-Indian Standards)

 

(i) Coarse Aggregate:  - The aggregate shall  consist of Crushed Stone, Crushed gravel / shingle or other stones. They shall be clean, strong, durable and free from disintegrated pieces, organic or other deleterious matter and adherent coating.  It shall use as per MORTH (Ministery of Road, Transport & Highways) specifications clause 504.2.2.

 

(iii) Fine Aggregate :  - Fine aggregate shall be the fraction passing 2.36 mm sieve and retained on 75 micron sieve, consisting of Crusher – run severing gravel, sand or a mixture of both. These shall be clean, hard, durable, uncoated, dry and free from any injurious, soft or flaky pieces and organic or other deleterious substances.

 

(iv) Filler:  -          Filler shall consist of finely divided mineral matter such as rock dust, hydrated lime or cement as approved by the Engineer.

                                    The filler shall be graded within the following limits.

IS Sieve	Percentage passing by weight
600 micron 300 micron 75 micron	100 95 – 100 85  - 100

                                    The Filler shall be free from organic impurities and have plasticity index not greater than 4. The plasticity index requirement shall not apply if filler is cement or lime. When the course aggregate is gravel 2 percent by mass of total aggregate of Portland cement or hydrated lime shall be added and the percentage of fine aggregate reduced accordingly. Cement or hydrated lime is not required when the gravel is lime stone.

 

(v) Aggregate Gradation:  - The mineral aggregates including filler shall be so graded or combined as to confirm to the grading set forth in table 500-20 of MORTH (Ministery of Road, Transport & Highways) specification Clause 511.2.5.

 

(vi) Mix Design:  - As per Engineer approval.

 

(vii) Binder Content: - The Binder content shall be so fixed as to achieve the requirement of the mix set forth in table 500-21 of MOST (Ministery of Road, Transport & Highways) specifications Clause 511.3.1. Marshal Method for arriving at the binder content shall be adopted.

 

(viii) Preparation of base:  - The base on which SDBC is to be laid shall be prepared, shaped and conditioned to the specified lines, grades and as directed by the Engineer.

 

(ix) Tack Coat:  - A tack coat as per clause 503 of MORTH (Ministery of Road, Transport & Highways) shall applied on the base.

 

(x) Preparation of Mix:  - Clause 507.4.4 of MORTH shall apply.

 

(xi) Rolling:  -       Clause 507.4.6 of MORTH shall apply.

 

(xii) Opening of traffic:  - Traffic may be allowed after completion of the final rolling when the mix has cooled down to the surrounding temperature.

 

(xiii) Surface finish and quality control of work:  - The surface finish of construction shall confirm to the requirement of Clause 902 of MORTH(Ministery of Road, Transport & Highways).

 

(xiv) Arrangement for traffic   :  - During the period of Construction, arrangement of traffic                                             shall be done

 

(xv) Environment:  -     As the mix to be used for laying is a hot mix plant & laying will mechanical Paver. So Contractor will take necessary action to prepare the mix at an isolated place so that smoke and dust will not affect the local people as well as the traffic using the road. The construction people handing the hot mix plant will be provided with helmet, hand gloves and hunter shoes.

 

(xvi) Measurement and Payment:  -  SDBC concrete shall be measured a finished work in cubic meter