Explain each type in brief?

HMA Mix Types:The most common type of flexible pavement surfacing is hot mix asphalt (HMA). Hot mix asphalt is known by many different names such as hot mix, asphalt concrete (AC or ACP), asphalt, blacktop or bitumen. For clarity, this Guide makes a conscious effort to consistently refer to this material as HMA. HMA is distinguished by its design and production methods (as described in this Guide) and includes traditional dense-graded mixes as well as stone matrix asphalt(SMA) and various open-graded HMAs. Typically agencies consider other types of asphalt-based pavement surfaces such as fog seals,slurry seals and BSTs to be maintenance treatments and are therefore covered in the Maintenance & amp; Rehabilitation section. Reclaimed asphalt pavement (RAP) is generally considered a material within HMA, while forms of in-place recycling are considered separately.Dense-Graded Mixes A dense-graded mix is a well-graded HMA intended for general use. When properly designed and constructed, a dense-graded mix is relatively impermeable. Dense-graded mixes are generally referred to by theirnominal maximum aggregate size and can further be classified as either fine-graded or coarse-graded. Fine-graded mixes have more fine and sand sized particles Purpose:Suitable for all pavement layers and for all traffic conditions. Works well for structural, friction, leveling and patching needs.Materials:Well-graded aggregate, asphalt binder (with or without modifiers), RAP Information: Particulars about dense-graded HMA are covered by the rest of this Guide.Stone Matrix Asphalt (SMA)Stone matrix asphalt (SMA), sometimes called stone mastic asphalt, is a gap-graded HMA originally developed in Europe to maximize rutting resistance and durability. The mix design goal is to create stone-on-stone contact within the mixture. Since aggregates do not deform as much as asphalt binder under load, this stone-on-stone contact greatly reduces rutting. SMA is generally more expensive than a typical dense-graded HMA because it requires more durable aggregates, higher asphalt content, modified asphalt binder and fibers. In the right situations it is cost-effective because of its increased rut resistance and improved durability. SMA, has been used in the U.S. since about1990.Purpose:Improved rut resistance and durability. SMA is almost exclusively used for surface courses on high volume interstates and U.S. roads.Materials:Gap-graded aggregate, modified asphalt binder, fiber filler Information:Other reported SMA benefits include wet weather friction (due to a coarser surface texture), lower tire noise (due to a coarser surface texture) and less severe reflective cracking.Mineral fillers and additives are used to minimize asphalt binder drain-down during construction, increase the amount of asphalt binder used in the mix and to improve mix durability.Open-Graded Mixes Unlike dense-graded mixes and SMA, an open-graded HMA mixture is designed to be water permeable. Open-graded mixes use only crushed stone (or gravel) and a small percentage of manufactured sands. The two most typical open-graded mixes are:Open-graded friction course (OGFC). Typically15 percent air voids and no maximum air voids specified.Asphalt treated permeable bases (ATPB). Less stringent specifications than OGFC since it is used only under dense-graded HMA, SMA or portland cement concrete for drainage.Purpose:OGFC – Used for surface courses only. They reduce tire splash/spray in wet weather and typically result in smoother surfaces than dense-graded HMA. Their high air voids reduce tire-road noise by up to50-percent (10 dBA) (NAPA,1995).ATPB – Used as a drainage layer below dense-graded HMA, SMA or PCC.Materials:Aggregate (crushed stone or gravel and manufactured sands), asphalt binder (with modifiers)Information:OGFC is more expensive per ton than dense-graded HMA, but the unit weight of the mix when in-place is lower, which partially offsets the higher per-ton cost. The open gradation creates pores in the mix, which are essential to the mix’s proper function. Anything that tends to clog these pores, such as low-speed traffic, excessive dirt on the roadway can degrade performance.

Thank you Mr Jaafar

There are three main layers of asphalt concrete that must be carpeted for the purpose of paving the road, namely: -

1. Base layer:-  minimum thickness10 cm and a minimum aggregate size  38 mm.

2-Bond layer has minimum thickness of5 cm, as well as min. aggregate size  25 mm 

Surface layer has minimum thickness5 cm as well as minimum aggregate size19 mm3  

 

Thank you my dear friend for invitation ,,, The three major types of asphalt surfacing, characterized by a mixture of bitumen and stone aggregate .Are: Dense Graded asphalt (DGA); Stone Mastic Asphalt (SMA) and Open Graded Asphalt (OGA).The Asphalt surfacing differ by the proportion of different size aggregate, the amount of bitumen added and the presence of other additives and material.The first aim of this study is to provide an updated systematic review of the evaluation of stone mastic asphalt in construction. This paper entitled “Stone Mastic Asphalt.” aims studying Objectives, construction material composition, economy achieving by using waste materials and advantages over the conventional mixes. Accurate quantification of aggregate gradation is essential for a better understanding of its effect on the load-carrying capacity of an asphalt mixture and Volumetric analysis of the aggregate. study investigates the benefits of stabilizing the stone mastic asphalt (SMA) mixture in flexible pavement with shredded waste plastic and use of baggase in the SMA. Stone mastic asphalt (SMA) is a stone-on-stone like skeletal structure of gap graded aggregate, bonded together by mastic, which actually is higher binder content, filler and fiber to reduce the binder drain. This structure improves the strength and the performance of SMA even higher than the dense graded and open graded asphalt mixtures. High percentage of binder content is important to ensure the durability and laying characteristics of SMA.

SMA is best explained as two-component hot mix asphalt HMA which comprises a coarse aggregate skeleton derived from a gap-graded gradation and a high bitumen content mortar. Since1960s, Stone Mastic Asphalt (SMA) pavement surfaces have been used successfully in Germany on heavily trafficked roads. In recognition of its excellent performance a national standard was set in Germany in1984. Since then, because of its excellent performance characteristics, the use of SMA increased in popularity amongst the road authorities and asphalt industry.

These two components combined address the concerns of both mixture stability and durability. SMA can provide an extremely high rut resistant and durable HMA mixture as compared with dense-graded asphalt mixture. This improvement is realized through the formation of a stone-to-stone aggregate skeleton in SMA. Based on many research reports and engineering case studies has on road surfaces can achieve better rut-resistance and durability. The SMA mixtures are designed to have high aggregate content, high asphalt content typically5.5–7% and high filler content. For ordinary SMA, the use of unmodified bitumen together with fibrous material as a drainage inhibitor is sufficient. Under high temperatures and heavy loading, a harder bitumen grade will also suffice .And now we will see the Difference Between SMA & Conventional Mixes 

SMA is successfully used by many countries in the world as highly rut resistant bituminous course, both for binder (intermediate) and wearing course. The major difference between conventional mixes and SMA is in its structural skeleton .The SMA has high percent about70-80 percent of coarse aggregate in the mix .This increases the interlocking of the aggregates and provides better stone to stone contact which serves as load carrying mechanism in SMA and hence provides better rut resistance and durability. On the other hand, conventional mixes contain about40-60 percent coarse aggregate. They does have stone to stone contact, but it often means the larger grains essentially float in a matrix composed of smaller particles, filler and asphalt content .The stability of the mix is primarily controlled by the cohesion and internal friction of the matrix which supports the coarse aggregates .It can be followed from diagram of the grain size distribution of the mixes given below.

The second difference lies in the binder content which lies between5-6 percent for conventional mixes. Below this the mix becomes highly unstable. Above this percent will lead to abrupt drop of stability because the binder fills all the available voids and the extra binder makes the aggregates to float in binder matrix. The SMA uses very high percent of binder >6.5 percent which is attributed to filling of more amount of voids present in it, due to high coarse aggregate skeleton. The high bitumen content contributes to the longevity of the pavements.

The third difference is the use of stabilizing additives in SMA which is attributed to the filling up of large no of voids in SMA so as to reduce the drain down due to presence of high bitumen content. On the contrary, there is no stabilizing agent in conventional mixes since the bitumen content is moderate, which only serves the purpose of filling the moderate amount of voids and binding the aggregates 

Eng.Jafar answered the Q completely..

So I am with his answer.

there  is  some intermixing of terms  such as bitumen and  asphalt. different countries  attach different   meanings to  these term.

may  by  type  are :

1-tar-bitumen 

2-asphalt concrete 

3-stone mastic asphalt

Thanks for the invitation

Good question

But i am so sorry i can,t answer it as

this question outside the area of  my

professional specialization.

time waste, material waste is self explanatory