What is the standard density of asphalt?
Standard density for asphalt is 145 lb/ft3 (2322 kg/m3). Multiply the volume by the density (in the same units) to get the weight.
What is the typical optimum air voids for asphalt mixtures?
The allowable percentage of air voids (in laboratory specimens) is between 2.0 percent and 4.0 percent for most surface course mixes or as required by the owner. The durability of an asphalt pavement is a function of the air-void content. This is because the lower the air-voids, the less permeable the mixture becomes.
What is mix design of asphalt?
HMA mix design is the process of determining what aggregate to use, what asphalt binder to use and what the optimum combination of these two ingredients ought to be. There are several different methods used to go about this process, of which the Superpave, Marshall and Hveem methods are the most common.
Why is asphalt compaction important?
For asphalt mixtures, compaction locks the asphalt-coated aggregate particles together to achieve stability and provide resistance to deformation (or rutting) while simultaneously reducing the permeability of the mixture and improving its durability.
What happens if VMA is low?
Lower VMA values means that the intergranular space available for asphalt binder is reduced. This reduces the amount of effective asphalt binder that can be used in the mix, which in turns, leads to a lower binder film thickness around the aggregate particles. Film thickness is linked to mix durability.
What is voids filled with asphalt?
The space filled with asphalt is known as VFA (Voids Filled with Asphalt). The remaining space is air voids. VMA is critical to a mixture’s durability and crack resistance. When VMA is lowered, you lower the asphalt binder content for a given air void level (typically 4.0 percent for Superpave mix design).
What is VMA and VFA?
Let’s look at VMA, which stands for “Voids in Mineral Aggregate.” VMA is the space between the rocks that can be filled with asphalt. The space filled with asphalt is known as VFA (Voids Filled with Asphalt). The remaining space is air voids. VMA is critical to a mixture’s durability and crack resistance.
What is mix design?
Mix design can be defined as the process of selecting suitable ingredients of concrete and determining their relative proportions with the object of producing concrete of certain minimum strength and durability as economically as possible.
How can you prevent asphalt compaction?
Take maximum advantage of available roller compactive effort. Rollers can be used where the mat is most receptive to compaction and avoided where the mat is susceptible to excessive shoving. Ensure the mat is compacted to the desired air void content before cessation temperature is reached.
What is the compaction factor for asphalt?
Remember, the compaction rate, as a general rule, is about 6 mm (1/4″) per 25 mm (1″) of screed laid thickness when a vibratory screed is used and about 5 mm (1/5″) per 25 mm (1″) when a tamping and vibrating screed is used. Always verify the compaction rate of the fresh layer when building a longitudinal joint.