Asphalt Paving Road Construction

Asphalt Paving Job Control

For  effective  control  of  asphalt  paving  works  a  comprehensive  understanding  is necessary of each of the following:-

(1)     Specification requirements,
(2)     Plant capabilities,
(3)     Construction processes,
(4)     Inspection requirements.

When faults occur, it is essential that they are quickly recognized, their cause determined and the necessary corrections made promptly.

 Planning of Supervision of Asphalt Paving

Supervision  commences  prior  to  the  start  of  the  asphalt paving,  when  the  engineer  and  project engineer with  contractor’s  manager, laboratory manager  and  supervisor  to  discuss  plans  and  arrangements  for  the carrying out of the works. Matters affecting the quality and timing of the works and the control of traffic that should be discussed, include:-

•    Rate of delivery of asphalt mix to the site,
•    Sequence of operations and safeguards to ensure continuity,
•    Number and types of rollers needed,
•    Matching of asphalt mix supply and paving speed,
•    The chain of command for giving and receiving instructions,
•    Reasons for rejecting the asphalt mix and/or suspending work,
•    Weather and temperature requirements,
•    Traffic control,
•    Lift thickness,
•    Spreading and rolling sequences,
•    Spreading and rolling temperatures,
•    Planning to minimize joints.

Before Paving Starts

Before  the  paving  operation  begins,  a  check  should  be  made  to  see  that  all  necessary inspections and preparations have been carried out. In particular check that:-

(a)     Base or roadway surface is properly prepared,
(b)     Traffic control arrangements are satisfactory,
(c)     Paving and compaction equipment is in good condition and adjustment,
(d)     Hand tools are available on the job,
(e)     Guidelines are in place,
(f)     Asphalt Paver screed is heated to operating temperature,
(g)     Inspectors and supervisors are familiar with the adjustments and settings of the type of
Asphalt Paver  being  used.

Asphalt Paving Road Construction

Gap Graded Asphalt Concrete

Gap graded asphalt is widely used in Britain where it is known as Hot Rolled  Asphalt Concrete . It’s also popular within South Africa. In certain areas Gap graded combine is recognized as stone filled sheet asphalt.   It’s utilized hot however is usually easier to compact.

On greatly trafficked and high speed highways it requires precoated aggregate rolled in to the surface, following dispersing, to provide skid level of resistance. Gap graded blend relies to some huge extent on the rigidity with the sand/filler/bitumen mortar with regard to stableness. Gap graded mix is sometimes used for surfacing residential streets and car parks in order to satisfy the desire for a very smooth surface look. Skid resistance of the fine distinctive surface can be adequate at lower speeds. Durability of gap graded combines employed for this particular purpose could possibly be improved together with higher deliberation over mix design.

Mix composition the the blend,

By Weight %:
Coarse Aggregate = 30
Fine Aggregate     = 53
Filler                    =  9
Bitumen               =  8

By Volume %
Coarse Aggregate = 25.7
Fine Aggregate     = 46.0
Filler                    =   7.8
Bitumen               =  17.5
Air Voids             =   3.0

Asphalt Paving Road Construction

Open Graded Asphalt Concrete

 Open graded asphalt  is produced from crushed or partly crushed aggregate containing hardly any fine material and incredibly little for filler injections. It is bound together with a relatively small amount associated with bitumen, is dependent mainly on mechanized lock with regard to stability and it has a high voids content. Because of its porosity it is less long lasting than a dense graded mix. Typical blend properties tend to be shown in beneath.

By Weight %:
Coarse Aggregate = 75
Fine Aggregate = 20
Filler = 1
Bitumen = 4.0 ~ 6.0

By Volume %
Coarse Aggregate = 56.3
Fine Aggregate = 14.6
Filler = 0.7
Bitumen = 8.4
Air Voids = 20.0

The open texture offers enhanced skid resistance and that’s why the mix is mainly utilized as a friction course. The porous mix of open graded asphalt enables water to escape through beneath vehicle tyres as well as as a result offers improved moist weather skid resistance from higher rates of speed. See notes 

Asphalt Paving Road Construction

Dense Graded Asphalt Concrete

 Dense graded asphalt  concrete includes a mixture of bitumen along with several levels associated with coarse and fine aggregate and usually a mineral filler such as lime scale, Portland cement or fly ash. Until recently the Division known this material because bituminous concrete. Typical blend properties tend to be shown in beneath.

By Weight %:

Coarse Aggregate = 62
Fine Aggregate     = 28
Filler                    =  5
Bitumen               =  4.5 ~ 5.2

By Volume %
Coarse Aggregate = 54.5
Fine Aggregate     = 24.6
Filler                    =   4.6
Bitumen               =  13.3
Air Voids             =   3 ~ 7

Such a mix depends largely on grading and density for stability and, after becoming compressed, presents a surface area of near texture. It requires careful proportioning associated with materials and the mixer of high effectiveness for uniform layer of all combination contaminants with binder.

The actual workability of a dense graded mix depends largely on its temperature, and it is actually therefore necessary that the blend be spread and compacted in order to it’s final shape while it still keeps adequate warmth.

Under regular conditions thick rated asphalt offers sufficient skid resistance as well as therefore may be the material most utilized by the Department. For this reason this program will be mainly dedicated to  dense graded asphalt concrete .