sand and silica sand, are all used, but what do they refer to?
It would be safe to assume that “beach sands” originate from coastlines and estuaries. The term “sharp sand” is used to describe coarsely graded sands. These sands would feel quite gritty when rubbed between your fingers. “Soft sand” is a term used to describe finely graded sands, these would feel more silky when rubbed between your fingers. “Silver sand” and “silica sand” are just generic terms used to describe any pale or light coloured sand.
Sand extraction and processing
Sand can be obtained using various extraction methods, including: underground mines, open cast mines (quarries) or dredged from the sea or river beds. The source of extraction will usually determine the impurities present in the final sand grade. For example, sea dredged sands would tend to have higher chloride salt and calcium (lime) content. All sand deposits contain material having a wide range of grain sizes, usually mixed with clay and gravel. These sand deposits will require extensive processing to remove the unwanted stones, oversize grains and clay. There are numerous types of sand
processing equipment available. The most basic process would involve the “as dug” sand passing through a
screener to remove any oversize material (stones or gravel). This would not change the composition or grading of the raw material in any other way. An improvement on this would be a basic wash plant which would, typically, consist of at least one screener combined with some form of holding vessel or open topped tank filled with water. Whilst this process would reduce the silt and clay content, it would not sort the grains or improve the particle size distribution.
Whilst a simple form of processing may be acceptable for some basic building/construction applications, it would not be suitable for sports turf use.
It is essential that sands used for sports turf are processed using a washing plant. Even small amounts of clay will negatively affect the drainage properties of any sand. The most basic washing plant will rinse the material and remove some silt and clay, sometimes these basic wash plants require the sand to be double
washed, or even triple washed, to improve the cleanliness of the finished
product.
Industrial silica sands are processed using sophisticated wash plants. Millions of pounds worth of investment is required for such plants. These will not only wash the sand effectively, they will also separate the incoming sand into two or more different grades. This process is commonly termed “hydro classification”. This plant would usually consist of density separators, cyclones, dewatering screens, numerous pumps and extensive lengths of pipeline and conveyors, large lagoons all operated using sophisticated computer controlled software. Various sand grades, for example “medium-coarse” and “medium-fine”, are produced using a continuous process which utilises gravity to sort sand grain sizes whilst dispersed in water. Coarser (heavier) grains will settle towards the base of the tank for discharge, whilst finer (lighter) grains will remain suspended in water towards the top of the tank. These finer grains are removed as the water overflows. This process will produce consistently graded sand grades, irrespective of fluctuations with the incoming “as dug” material. It will also produce a tightly graded product with uniform sand grain sizes which are ideal for sports turf.
Some industrial sand processing
suitability for use, then you will be in for a few surprises”
Mick Higgins, Technical Manager, Ruffords
“If you rely on particle size distribution alone to determine a sand’s
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