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About Lime
LIMESTONE: All lime products evolve from limestone. Limestone is formed by the compaction of the remains of coral animals and plants on the bottoms of oceans around the world. Limestone is a sedimentary rock composed of the mineral calcite (calcium carbonate) and/or the mineral dolomite (magnesium carbonate) along with small amounts of other minerals. Types of limestone are defined by their magnesium carbonate (MgCO3) concentrations (ASTM C 51):
Dolomitic limestone consists of 35 to 46% magnesium carbonate.
Magnesian limestone consists of 5 to 35% magnesium carbonate.
High calcium limestone contains less than 5% magnesium carbonate.
Limestone is crushed and screened to serve a wide variety of applications including:
pH adjustment (aglime, water treatment)
Formulated product filler (masonry cements, ready mix concrete, asphalt, joint compounds, etc...)
Flue gas desulfurization
Production of stone blocks
Quality considerations for stone products include their purity, color and sizing. Graymont Dolime (OH) Inc. quarries a high purity dolomitic limestone, specifically Lockport (Niagaran) dolomite, which was formed during the Silurian period. The purity of the dolomitic deposits in Northwest Ohio is well known. This area is still one of the select areas of the world for the production of lime for plaster applications due to the bright white color of the hydrated lime.
QUICKLIME: Lining fire pits with rocks, ancient man discovered that the heat turned limestone into a new and different material. The rocks, now soft and white, reacted with water to give off heat. Today, properly sized limestone is converted to quicklime through calcination in rotary or vertical kilns. The following chemical reaction takes place in the kiln with dolomitic limestone:
CaCO3 + MgCO3 + HEAT = CaO + MgO + 2CO2
Heat is created in the kiln by burning pulverized coal, natural gas or oil. Kilns are normally operated at temperatures of 2000 �F or higher to drive carbon dioxide from the limestone.
Quicklime products have high chemical availabilities. Quicklime is used for a wide variety of industrial applications. Major uses of quicklime are found as a fluxing agent in the steel industry and in flue gas desulfurization. Often quicklime is mixed with water in "slakers" prior to use in industrial applications.
Quicklime has been used in the past as a building product (ASTM C 5). Quicklime slaked (soaked in water) on the job, however, requires a long soak period. The quality of slaked quicklime is dependent on a number of factors including degree of burn, water temperature and purity. Quicklime is very seldom used for building applications today.
HYDRATED LIME: Quicklime can be converted into a dry powder called hydrated lime by adding water under controlled conditions. The exothermic chemical reactions which occur under this process include:
CaO + H2O = Ca(OH)2 + HEAT MgO + H2O = Mg(OH)2 + HEAT
The hydration of calcium oxide occurs readily at atmospheric pressure. Magnesium oxide, however, requires long reaction time and/or a high pressure levels to completely hydrate.
For building lime, two different types of dolomitic hydrated lime products are defined.
Type N or Normal hydrated lime products are only partially hydrated and/or have poor workability. Additional additives and/or long soak periods are required for these products to perform effectively in masonry applications. At least a 24 hour soak period is required before Type N dolomitic hydrate can be used acceptably for masonry or plaster applications. High calcium hydrated lime products normally are classified as Type N hydrates due to their poor water retention. ASTM C 270 (Mortar for Unit Masonry) states that if a Cement/Lime blend contains Type N hydrates, the blender must show through performance or testing that the Type N product is not detrimental to the soundness of the mortar. Grand Prize� is a Type N Finishing Lime product.
Type N dolomitic hydrates are often used in industrial applications such as water or waste treatment or in agriculture. Since Type N dolomitic hydrates are hydrated under atmospheric pressure, water is only combined with the calcium portion of this product. Since there is less chemically combined water, this product has higher neutralizing value than pressure hydrated dolomitic lime. Graymont Dolime Agricultural Lime, Limoid� N and Kemidol� Hydrate are excellent Type N hydrated lime products.
Type S or Special hydrated lime products are a combination of calcium and magnesium hydroxides. In building applications, Type S dolomitic hydrated lime products have high hydration levels and controlled plasticity (water retention). This allows for minimal soak periods prior to application. Snowdrift�, Ivory� , Super Limoid� S and Mortaseal � are all popular Type S building limes used throughout the U.S. and Canada.
In industrial applications, the high surface area of Type S hydrated lime is desirable for sorbent applications. Kemidol� Superhydrate and Limoid� S are the Graymont Dolime (OH) Inc. Type S Industrial lime products. Air entrainment additives can be added to either category of hydrated lime product.
Air entrained products are defined as Type NA or Type SA in ASTM C 207. ASTM C 207 limits the amount of air content for Cement/Lime (PCL) mortars to 12% for a Type M or S mortar and 14% for Type N and O mortars. If the application involves structural reinforcement, air content cannot exceed 12% in any type of PCL mortar. Air entrainment additives enhance the workability of the mortar blend. As air content increases, bond strength of the mortar decreases. Bondcrete � Mason's and Stucco Lime and Super Limoid� SA are popular Type SA hydrated lime products