Optimizing the green compression strength and permeability of green sand made from Epe silica sand
Effect of varying binders (bentonite and dextrin) and water on the properties of recycled foundry sand made from silica sand mined from Ilaro Silica sand deposit in Ogun State Nigeria and have been used in several cycles for production of cast iron was examined. The used sand was washed in hot water, dried and the sieved for grain distribution. Varying bentonite and dextrin contents were added together with water to portions of the silica sand and thoroughly mixed. The moulding sand properties (permeability, green strength, compatibility, shatter index and moisture content) of the recycled foundry sand were determined. It was observed that the recycled Ilaro sand (after several cycle of usage) has grain Fineness Index (GFI) of 50 and that it can still be reused by minimum addition of binders. It was concluded that the optimum green strength and permeability for the recycled sand was achieved when 12g of bentonite, 8g of dextrin and 12cm3 of water were added to 200g of recycled sand.I think the key here is 8 parts dextrin to 12+12+200 parts by weight.
Elsewhere I have read the ratios for such binders is .5 to .75%. The above ratio is 3.6%.
Currently I am having problems with edges and plan on trying to mix a small quantity of facing sand by adding dextrin in the 8/224 ratio. Then applying this sand where I think it is needed.
Adding this tiny amount of dextrin should not significantly effect the sand in future castings.
Placed 262 of green sand in the toaster oven to dry it out. The dextrin will mix better in dry sand. It will be interesting to see what the water ratio is. Have not looked at that in a year. Have been 'adjusting to taste'.
262g x 0.005 = 1.2g
Well that did not got well. The new scale has a 1 gram resolution. Need to use the little precision scale if I make another tiny batch. But its made and it smells like dextrin. Works and feels different. Put it in a zip lock.
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