Percentage of air voids

The percentage of air voids (n ) is defined as the ratio of air voids (V ) to the total volume (V) and is determined from the equation 

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Marshall test specimens of asphalt mixtures were prepared with the asphalt content varying at 0.5 percent intervals within the range of 4.5 to 6.5 percent. Density, stability and flow value of the specimens were measured to calculate the percentage of air void and voids filled with asphalt and to determinate the design asphalt content. 

Specimen bulk density is determined with the respective method depending on the expected percentage of air voids. 

Particularly, if the percentage of air voids is expected to be <7%, the specimen bulk density is determined following procedure B of CEN EN 12697-6 (2012). During this procedure, the mass of the saturated surface dry specimen, in grams, is taken into account to calculate the specimen volume. 

For the determination of the optimum binder content in mix, apart from stability (corrected stability) and flow, the following volumetric properties should be calculated bulk density (pb) or bulk specific gravity the percentage of air voids (Vj), the percentage of voids... 

The air voids in a compacted bituminous mixture consists of the small air spaces among the coated aggregate particles. The percentage of air voids in the compacted bituminous mixture is calculated by the following equation ... 

Material and Ball Charges The load of a grinding medium can be expressed in terms of the percentage of the volume of the mill that it occupies i.e., a bulk volume of balls half filling a mill is a 50 percent ball charge. The void space in a static bulk volume of balls is approximately 41 percent. The amount of material in a mill can be expressed conveniently as the ratio of its volume to that of the voids in the ball load. This is known as the material-to-void ratio. If the solid material and its suspending medium (water, air, etc.) just fill the ball voids, the MA ratio is 1, for example. Grinding-media loads vary from 20 to 50 percent in practice, and MAT ratios are usually near 1. 

The voids in the mineral aggregate (VMA) are defined as the void space between the aggregates in a compacted bituminous mixture that includes the air voids and the effective bitumen content, expressed as a percentage of the total mix volume. 

Porosity—The ratio of the volume of air or other gases contained within the boundaries of a material to the total volume (solid material plus air or void), expressed as a percentage. 

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