The addition of water to dolomitic quicklime at atmospheric pressure will hydrate only the calcium oxide portion of the product.
The hydration reaction is:
CaO-MgO + H2O → Ca(OH)2-MgO
The hydration reaction breaks the quicklime down into fine particles of hydrated lime. The sizing of the hydrated lime is further modified by milling the product to ensure consistency. The dolomitic products produced with this process are categorized as Type N hydrated lime as defined by ASTM C206 and C207. The lower molecular weight of magnesium and less chemically combined water result in high neutralizing power for these products as seen by the basicity factor.
Type N dolomitic hydrates are utilized in construction, agricultural and industrial applications.
In construction applications, Type N hydrated lime products must be soaked for a minimum of 16 hours prior to use. The long soak period provides two benefits. First, a long soak time is required to fully hydrate the magnesium oxide portion of the hydrate. Hydration of magnesium oxide is necessary to ensure that expansion does not occur after application of the product. Secondly, soaking the product reduces its particle size. This results in lime putty that has excellent body and workability. Graymont's Grand Prize® Type N Finishing Lime is the only Type N hydrated lime currently produced in the United States for construction applications. This product complies with ASTM C206 and C207 standards for a Type N hydrate, and is available in 50-lb. (22.5-kg) bags.
Graymont's agricultural hydrated lime is a Type N hydrated lime product used to modify soils for agricultural applications. The following benefits can be attained through the use of this product in agriculture:
- Graymont agricultural hydrated lime supplies calcium and magnesium nutrients needed for proper plant growth.
- This product also reduces soil acidity. This improves soil properties and increases crop yields by:
- Speeding decay of organic matter and the liberation of plant nutrients;
- Increasing availability of residual and applied phosphorus;
- Increasing fixation of nitrogen by soil and plant organisms; and
- Reducing activity of injurious substances in the soil;
- Finally, Type N hydrated lime is faster-acting than ag-lime (limestone). Hydrated lime is more soluble, has higher neutralizing power and reacts more quickly.
Graymont agricultural hydrated lime is available in 50-, 25- and 10-lb. bags.
Type N hydrated lime products can also be used for a wide range of industrial applications due to their controlled sizing and high chemical availability. The high neutralizing value of Type N hydrated lime is useful for acid-neutralization applications as well as the treatment of hazardous wastes. Kemidol hydrate is the Type N hydrated lime product produced by Graymont. This product is available in 50-lb. (22.5-kg) bags, one-ton 'supersacks' and bulk.