Reservoir aggregate

For advice on decorative surface aggregates see Stone
Gravel for underdrains and underground infiltration structures should be 20 - 50 mm, uniformly-graded, clean (maximum wash loss of 0.5%), crushed angular stone that has a void ratio of 0.4 (40%).
The uniform grading and the angularity are important to maintain pore throats and clear voids between particles. (i.e. achieve the void ratio).
The clean wash is to prevent rapid accumulation of fines in the base of the reservoir.

Gravel with structural requirements should also meet the following criteria:

• Minimum durability index of 35
  
• Maximum abrasion of 10% for 100 revolutions and maximum of 50% for 500 revolutions

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A broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.

The void ratio (e) of a mixture is the ratio of the volume of void-space to the volume of solids. It is closely related to the concept of porosity (n) where porosity is the ratio of the volume of void-space to the total or bulk volume of the mixture. e = Volume of voids/Volume of solids = n/(1-n)

Soil particles with a diameter less than 0.050 mm.

The porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e)