Fluid Residuum
Globally, the ratio of quarry silt from the total extracted material can vary between 5-40% depending on the site geology. Construction industry makes up the 75% of the total sand and gravel demand, which is yearly 37,5 billion tons. Considering 87% of sand and gravel demand is met by mining, avg. 15% of the extracted material corresponds to 4.9 billion tons of by-product.
It is a very fine-grained and homogeneous mineral mixture (grain size smaller than 0.063 millimeter). They consist of finely divided silicates (quartz, feldspar), carbonates (calcite, dolomite) and clay minerals (illite, chlorite, montmorillonite/smectite, kaolinite).
Silt is collected in water and then pumped into lagoons to settle out. Ideally the water is recycled out of the sludge via filter presses. Using filter presses speeds up the process and eliminates the need for settling lagoons. The main use of quarry silt is as landfill material for filling the gap of the quarried space and for road constructions. When used as landfiller, it needs to be mixed with other materials which have bigger grain sizes. Otherwise, it might cause colmation if it reaches river beds and reduce ground permeability.
Investigating into reusing this by-product contributes to more efficient use of resources and revaluation of the overlooked materials, as well as reduces grey energy.
Material: Gravel washing fines (by-product)
Process: Sculpting and kiln firing
Rabius -Graubuenden - CH
Thanks to Beer SA for the support.
Photos by Studio Eidola.