# The weight of gravel becomes more variable with increasing grain size

The weight of gravel is calculated from the amount of bulk material that fits into a specified volume. The rough average density of 1750 kilograms per cubic meter can vary even with identical gravel with coarser grain size by the random bed.

### Gravel "falls" irregularly

Grains between 32 and 63 millimeters are defined as gravel. Since the designation in the construction trade is always based on the largest grain size available in a sorting, the majority of the grain content often consists of chippings. For "real" crushed stone with the smallest grain sizes of 32 millimeters, a relatively coarse random drop pattern results when pouring. The irregularly shaped quarry stones come to rest after the bed and when one cubic meter is filled, the amount of ballast is weighed. This density determined in this way can produce a result that deviates by up to ten percent in the case of a second pouring operation with the same or the same ballast. The larger the grain size, the more dependent is the density and thus the weight of the ballast from the lying position of the individual grains. This can be illustrated with the idea that several large boulders are accidentally thrown into a pit. Depending on the shape, they tilt sooner or later, and for gravel with grain sizes of more than 500 millimeters, the number of chunks varies with each throw and pile up, which fit into one cubic meter of pit.

### Weight of the starting material

Another crucial weighting factor is the source material that makes up the ballast. Lava rock itself has a much lower weight than, for example, granite. As a result, the range of possible weights is limited, may arise in the deviations due to infill. Typical density and weight ranges are:

• Recycling gravel from blast furnace slag 1000-1400 kg / m³
• Lava gravel 1200-1400 kg / m³
• Limestone gravel 1550-1750 kg / m³
• Basalt gravel 1500-1800 kg / m³
• Recycled brick ballast 1400-1700 kg / m³
• Granite Otter 1700-2000 kg / m³

From the density specification, the weight of the individually required ballast is calculated by multiplying the measured volume in cubic meters by the weight from the density specification.

### Tips & Tricks

If you buy gravel with chippings, the variability due to the gravel and fall behavior of the ballast plays a minor role, because the smaller grains in the interspaces always distribute themselves in a similar way.