asphalt Archives - Civil Engineering Tips

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

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 .