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<p>There are three major types of asphalt surfacing, characterized by a mixture of bitumen and stone aggregate.</p>
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
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.