Rice husk ash is used in the steel industry for producing high-quality flat steel, a plate product or a hot rolled strip product usually used in automotive body-panels manufacturing. The ash also finds application as an excellent insulator, having fine insulating properties including low thermal conductivity, a high melting point, low bulk density and high porosity. It is used as a "tundish powder" to insulate the tundish--a container for pouring molten metal into a mold--enabling prevention of rapid cooling of the steel and ensuring uniform solidification in the casting process.
Rice husk ash is used in the manufacturing of low-cost building blocks and in the production of high-quality cement. Ordinary Portland cement is one of the most expensive components of concrete; the replacement with rice husk ash of a proportion of Portland cement offers improved concrete affordability, particularly for low-cost housing. Adding rice husk ash to cement speeds up setting time of the cement, although the water requirement is greater than ordinary cement. At about 35 percent replacement, the ash cement has improved compressive strength because of a higher percentage of silica. The ash cement has improved resistance to acid attack as compared to ordinary Portland cement.
Rice husk has a high ash content, varying from 18 to 20 percent. Silica is the major component of rice husk ash; with such a large silica content in the ash, the extraction of silica is economical. Silica also may be precipitated in customized forms to meet the requirements of various uses. Some of the uses of silica are in the rubber industry as a reinforcing agent, in cosmetics, in toothpastes as a cleansing agent and in the food industry as an anti-caking agent.
Rice husk ash is used in the manufacture of refractory bricks because of its insulating properties. It has been used in the manufacture of low-cost, lightweight insulating boards. Rice husk ash has been found to be effective as an oil spill absorbent, and for use in waterproofing chemicals, flame retardants, and as a carrier for pesticides and insecticides.