Check the listing for details. Burnt Rice Husk Ash Compost fertilizer 100% Organic Hydroponic Substrate growing. Condition: New. Listed at 5.00 USD. RICE HUSK ASH Combustion of rice hulls affords rice husk ash (acronym RHA). This ash is a potential source of amorphous reactive silica, which has a variety of applications in materials science. Most of the ash is used in the production of Portland cement.[1] When burnt completely, the ash can have a Blaine number of as much as 3,600 compared to the Blaine number of cement (between 2,800 and 3,000), meaning it is finer than cement. Silica is the basic component of sand, which is used with cement for plastering and concreting. This fine silica will provide a very compact concrete. The ash also is a very good thermal insulation material. The fineness of the ash also makes it a very good candidate for sealing fine cracks in civil structures, where it can penetrate deeper than the conventional cement sand mixture. Rice husk ash has long been used in ceramic glazes in rice growing regions in the Far East, e.g. China and Japan.[2] Being about 95% silica, it is an easy way of introducing the necessary silica into the glaze, and the small particle size helps with an early melt of the glaze. A number of possible uses for RHA include absorbents for oils and chemicals, soil ameliorants, a source of silicon, insulation powder in steel mills, as repellents in the form of "vinegar-tar" release agent in the ceramics industry, as an insulation material. More specialized applications include the use of this material as a catalyst support. Goodyear announced plans to use rice husk ash as a source for tire additive. Rice hulls are a low-cost material from which silicon carbide "whiskers" can be manufactured. The SiC whiskers are then used to reinforce ceramic cutting tools, increasing their strength tenfold.[6]