What are the different types of mixes available for maintaining asphalt pavements?
The pavement mix types targeted are OGFC, SMA, and fine- and coarse-graded dense mixes.
What is AC20 asphalt?
When we talk about Asphalt Surfacing, we used to generally be talking about the use of Stone Mastic Asphalt (SMA) or Hot Rolled Asphalt (HRA). So, for example, what used to be known as a 20mm Dense Bituminous Macadam (DBM) is now termed an AC20 (Asphalt Concrete in 20mm).
What is the mixture of asphalt?
Asphalt mixtures: Asphalt is a mix of sand, gravel, broken stones, soft materials, and asphalt. In Marshall’s Standard Test* for designing asphalt mixtures, it was found that the percentage of asphalt required can be reduced as the density of the mixture increases.
What is AC14?
Type AC14 gradation for granite aggregates and bitumen of penetration type 60/70 were used for this study based on the Public Works Department of Malaysia’s Standard Specification for Road Works. The optimum Cecabase RT additive content was then determined using samples prepared at the optimum bitumen content.
What is the difference between HMA and SMA?
Stone Matrix Asphalt (SMA) 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.
What is the difference between SMA and HRA?
The bitumen content, whilst higher than for SMA is less than used for HRA. The continuous aggregate grading gives high mechanical stability due to the aggregate particle interlock and as such is a more sensible material altogether than HRA which is a gap graded mix more akin to a plum pudding.
What is dense macadam?
Introduction: • Dense Bituminous Macadam (DBM) is a binder course used for roads with more number of heavy commercial vehicles and a close-graded premix material having a voids content of 5-10 per cent. This material has increased in popularity due to durable surface which performs almost well as in all situations.
What are the different grades of asphalt?
There are three different grades available in asphalt. The grades available are I-2, also known as base; I-5, known as top ;and the I-4 or commercial top grades. The difference in the tree grades are that the I-2 or base consists of ¾ inches of stone. The base grade is generally used in corn stabilizing level.
What is asphalt and its types?
Three types of the asphaltic mixture used in roads are: Rolled Asphalt, Mastic Asphalt, Compressed Rock Asphalt .
What is the thickness of asphalt in Australia?
Asphalt 40mm or thicker is required to be a dense graded asphalt (DG14) in accordance with Main Road’s “Standard Specifications Roadworks” c. Asphalt of 30 – 40 mm thickness must be a dense graded asphalt (AC10) in accordance with the Australian Asphalt Pavement Association (AAPA’s) “National Asphalt Specification”
How big is a 9.5 millimeter asphalt mix?
Mix types are distinguished according to nominal maximum size of the aggregate in millimeters, i.e. 9.5 relates to an aggregate size of 9.5 millimeters, or 3/8 inch. Selection guidelines for asphalt pavement presented in two categories, Low to Medium Volume and Medium to High Volume:
How is aggregate gradation determined in asphalt mix design?
Gradation specifications are used to ensure acceptable aggregate gradation. Asphalt binder content . Excess asphalt binder content tends to lubricate and push aggregate particles apart making their rearrangement under load easier. The optimum asphalt binder content as determined by mix design should prevent this.
What should be considered when choosing asphalt mix?
The optimum asphalt binder content as determined by mix design should be high enough to prevent excessive fatigue cracking. The use of an asphalt binder with a lower stiffness will increase a mixture’s fatigue life by providing greater flexibility. However, the potential for rutting must also be considered in the selection of an asphalt binder.