Our customer service department answers many questions regarding our lime products for all the industries we serve. The questions range from lime applications and use to storage, shipping and handling. As a resource to our customers and website viewers, the listing below represents the most frequently asked questions.
Read disclaimer regarding the FAQs on this page
- How many types of lime are there? I am confused by terms like “agricultural lime”, “quicklime”, slaked lime, hydrated lime. Are these all the same?
- What precautions should I take in handling quicklime or hydrated lime?
- What test methods are available to determine quality of lime and lime-based products?
- Where can I find information on physical and chemical properties of lime, bulk handling and storage of lime in bins and silos, solutions to common lime handling and flow problems, and descriptions of lime slaking equipment and lime slurry feeding systems?
- What are some of the typical impurities found in limestone and lime products?
- What types of lime are used for soil stabilization?
- How should lime being used for soil stabilization be specified?
- Can dolomitic lime be used for soil stabilization?
- How is soil tested to determine the proper amount of lime needed for stabilization?
- What technical references and resources are available to help design lime-stabilized soils for long-term strength and durability?
- Where can I find information on lime stabilization construction practices?
- How are soils classified?
- What soils are appropriate for lime stabilization?
- Can lime be used with soils containing soluble sulfates?
- Can lime be combined with fly ash for soil stabilization?
- Why are lime products so dusty?
- Can I store the lime outside?
- What is the shelf life of lime products in a storage tank?
- What is the difference between high calcium quicklime, dolomite quicklime and magnesian quicklime for the steel maker?
- Does the reactivity test for lime indicate how it will react in producing a slag in the electric arc furnace?
- What is typical lime consumption for the electric furnace practice?
- How does lime melt in the furnace when temperatures reach about 3000° F and lime melts at 4,658° F ?
- Why is adding more lime to the BOF a problem when trying to reduce Phosphorous?
- What kind of PPG do my workers need?
- What references are available that describe lime-based and other options for flue gas desulfurization (FGD) and compare costs of leading systems?
- I require FGD, but I have no space on my site for disposal of FGD by-products. Are there lime-based FGD systems that produce by-products which I can sell or provide for beneficial uses?
- What is the difference between wet and dry lime-based FGD systems?
- Are dry FGD systems only suited for smaller industrial applications?
- I have other pollutants in my flue gas that I need to remove in addition to sulfur dioxide. Will a lime-based FGD system remove other pollutants?
- Can I purchase lime already in slurry form to avoid having to purchase, operate, and maintain slaking and slurry making equipment?
- Should I use quicklime, hydrated lime or Milk of Lime?
- What ASTM Specifications does Rockwell's products conform to?
- What is the difference between Type “S” Lime and Type “S” Mortar?
- What advantages does Type “S” Lime add to a Portland/Lime mortar?
- Do cement/lime mortars work with all types of building materials?
- Do mortars made with lime /cement have better potential for reduced water penetration?
- What is Autogenous Healing?
How many types of lime are there? I am confused by terms like “agricultural lime”, “quicklime”, slaked lime, hydrated lime. Are these all the same?
There are several types of products that are referred to as “lime.” Most lime is the natural chemical oxide (CaO), which is commonly referred to as lime, quicklime or burned lime. The name quicklime comes from an old meaning of “quick” as in alive or lively, since quicklime reacts vigorously with water. The name burned lime is used because quicklime is produced by burning limestone quarried or mined from the earth. Quicklime resembles white pebbles and is usually produced in sizes ranging from 1-3/4 inch to 1/8 inch. Agricultural lime is usually ground limestone, which is the natural chemical calcium carbonate (CaCO3). Another type of quicklime is dolomitic lime, which contains about 40% magnesium oxide (MgO) in addition to calcium oxide. Slaked lime, hydrated lime and hydrate refer to products formed from reaction of quicklime with water. Quicklime reacts with water to form calcium hydroxide [Ca(OH)2]. Slaked lime is a fluid mixture of calcium hydroxide and water formed by mixing 1 part of quicklime with about 4 parts of water. Users of lime usually produce this mixture themselves in equipment called lime slakers. Slaked lime resembles a milk shake and is sometimes called “milk of lime.” Hydrated lime or hydrate is a dry powder of calcium hydroxide formed by mixing 1 part of quicklime with ½ part of water. Hydrated lime is produced at lime manufacturing plants and shipped to users in bags or in bulk trucks. Hydrated lime resembles talcum powder.
What precautions should I take in handling quicklime or hydrated lime?
Quicklime and hydrated lime are both reactive natural chemicals, and like any chemical have (MSDS) Material Safety Data Sheets that should be referred to prior to use. An MSDS sheet for quicklime and hydrated lime can be obtained in our products listing.
What test methods are available to determine quality of lime and lime-based products?
The two most widely used test methods are from the American Society of Testing and Materials (ASTM) and the American Water Works Association (AWWA). The ASTM Annual Book of Standards Volume 04.01 Cement; Lime; Gypsum is available for purchase from ASTM at www.astm.org. Methods for chemical analysis of lime and lime products are found in method C 25. Physical methods are found in method C 110. The AWWA standard B202-93: Quicklime and Hydrated Lime is available for purchase from AWWA at www.awwa.org
Where can I find information on physical and chemical properties of lime, bulk handling and storage of lime in bins and silos, solutions to common lime handling and flow problems, and descriptions of lime slaking equipment and lime slurry feeding systems?
An excellent guide to solutions on lime handling, storage, and usage is the booklet Lime: Handling, Application, and Storage, available from Carmeuse Lime & Stone. To purchase a copy of the guide go to the publication library available at the The National Lime Association website www.lime.org
What are some of the typical impurities found in limestone and lime products?
Impurities in limestone are a function of the geology of the ore body. They consist of elements within the limestone matrix and other non-limestone materials (“inerts”) that may have been mined along with the limestone. Some common ranges of impurities in typical limestones are:
What types of lime are used for soil stabilization?
Both hydrated lime and quicklime are used. Quicklime will consume more of the soil's moisture as it hydrates, then reacts with the soil. Lime kiln dust is also used, but may require more quantity as it typically consists of 20-25% CaO, while high calcium quicklime consists of about 90% CaO. When using lime kiln dust the quality should be checked regularly.
How should lime being used for soil stabilization be specified?
Lime should meet the requirements of ASTM C-977, “Standard Specification for Quicklime and Hydrated Lime for Soil Stabilization" or AASHTO M 216, “Lime for Soil Stabilization.”
Can dolomitic lime be used for soil stabilization?
Yes. ASTM C-977, “Standard Specification for Quicklime and Hydrated Lime for Soil Stabilization”, allows for the use of dolomitic lime. Both material are effective for soil drying, modification (plasticity reduction) and stabilization. Certain basic chemical and physical differences exist between high calcium lime and dolomitic lime that may affect lime-soil reactivity.
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Pound for pound, high calcium lime provides more free calcium or available calcium (Ca), making it somewhat more effective.
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In some cases, slightly more dolomitic lime may be required for soil stabilization. However, this is very dependent on the soil properties. In many cases, lime quantities do not need to be increased if dolomitic lime is used for soil stabilization.
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When soil stabilization (rather than drying or modification) is the goal, laboratory procedures to determine the mixture proportions should be done using the type of lime that will be used on the job. Such testing will often show that equal quantities of dolomitic and high calcium lime will effectively stabilize a reactive soil.
How is soil tested to determine the proper amount of lime needed for stabilization?
Two ASTM procedures apply – ASTM D-6276, “Standard Test Method for Using pH to Estimate the Soil-Lime Proportion Requirement for Soil Stabilization” and ASTM C-977 (Appendix A). The amount of lime, as a percentage of the soils bulk dry density, needed to maintain a pH level of the moistened soil-lime mixture of at least 12.4 for one hour is determined. Strength tests, generally unconfined compressive tests (ASTM D-5102) are then used to evaluate the long-term and weather resistance properties of the lime-stabilized soil.
What technical references and resources are available to help design lime-stabilized soils for long-term strength and durability?
The National Lime Association's (NLA) website www.lime.org
describes a number of technical publications available on lime stabilization from the NLA. “Evaluation of the Structural Properties of Lime Stabilized Soils and Aggregates”, Volumes 3 and 4 are particularly informative.
Where can I find information on lime stabilization construction practices?
The National Lime Association's publication “Lime Stabilization Construction Manual” can be ordered through the NLA's website www.lime.org
How are soils classified?
Two systems are generally used to classify soils:
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American Association of State Highway and Transportation Officials (AASHTO) Standard M145.
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American Society for Testing and Materials (ASTM) D-2487. This is commonly called the Unified Soil Classification System.
Particle size, fraction passing the No. 200 sieve (0.074 mm), and plasticity characteristics are the chief characteristics used to classify soils. The AASHTO Classified System groups the soils into seven basic groups, designation A-1 to A-7, with subgroups in some of the groupings. The Unified Classification System groups soils into four major divisions – gravels, sands, silts and clays with liquid limit less than 50, silts and clays with liquid limit 50 or more. These divisions are further separated into 11 groups represented by two letter symbols. For instance, a soil described as “silty sand, sand-silt mixture” would be classified as SM.
In addition to the AASHTO M145 and ASTM D-2487 standards, most soils engineering textbooks provide a good reference for more information.
What soils are appropriate for lime stabilization?
Experience has shown that lime will react with medium, moderately fine and fine grained soils. Generally speaking, those soils classified by the Unified System as CH, CL, MH, SM, GC, SW-SC, SP-SC, SM-SC, GP-GC or GM-GC are potentially capable of being stabilized with lime. The extent to which the soil-lime pozzolanic reaction proceeds is influenced primarily by the natural soil properties.
As a general guide, lime stabilization should be considered for soils that have plasticity indices of 10 or greater along with 25% or more of the soil smaller than the number 200 sieve. Particles smaller than the No. 200 sieve (0.074 mm) are considered to be silt (0.002 to 0.06 mm) or clay (< 0.002 mm). Lime is generally the stabilizer of choice for soils that have plasticity indices above 30 and greater than 25% material passing the number 200 sieve.
Can lime be used with soils containing soluble sulfates?
Particular attention must be paid to the sulfate content of soils when considering lime stabilization. Caution must be used when using lime or any calcium-based stabilizer with soils containing more than 10% clay and 0.2% soluble sulfates when the sulfates are extracted from the soil in a 10 parts water to 1 part soil solution. For more information, see “Technical Memorandum: Guidelines for Stabilization of Soils Containing Sulfates” available from the National Lime Association www.lime.org
Can lime be combined with fly ash for soil stabilization?
The addition of fly ash can significantly increase the compressive strength of a lime stabilized soil. The fly ash provides additional alumina and silica to the mixture made soluble at high pH, reacting with the calcium from the lime to form calcium aluminates and calcium silicates for the pozzolanic cementitious action. This is particularly beneficial for lower plasticity soils with higher silt content. With proper material selection and proportioning, virtually any granular soil can be stabilized with lime-fly ash.
Why are lime products so dusty?
Quicklime products are naturally friable materials.
Can I store the lime outside?
No, quicklime products are very hydroscopic and can react with the moisture in the air. Quicklime products should be stored in silos or at a minimum under roof.
What is the shelf life of lime products in a storage tank?
Quicklime products should be stored in silos or at a minimum under roof. Shelf life depends on the amount of exposure to air and the elements. Products stored in moisture proof silos can last several months or more if air infiltration can be kept to a minimum.
What is the difference between high calcium quicklime, dolomite quicklime and magnesian quicklime for the steel maker?
The chemistry of these limes are related to the natural stone from which they are processed. High calcium quicklime has approximately 97% CaO with MgO less than 3%. High Calcium lime is utilized in the furnace for slag production and in the secondary steelmaking process to promote desulfurization, inclusion entrapment, and insulation against air and to prevent temperature losses. Dolomitic quicklime contains natural combinations of CaO and MgO, with CaO content as low as 60% with a corresponding MgO content of up to 40%. This is used primarily for meeting the MgO requirements of the EAF slag to prevent refractory wear and promote good foaming properties to protect the sidewalls of the furnace. A specific Magnesian quicklime called SteelCal is available from Carmeuse. This product provides natural combinations of Calcium and Magnesium Oxides, ranging from of 5% to 12% of MgO. This product is utilized in the furnace to promote early dissolution of MgO with additional dolomitic lime added later to meet the increasing need of MgO in the slag.
Does the reactivity test for lime indicate how it will react in producing a slag in the electric arc furnace?
No. The reactivity test uses water to determine a rate of temperature rise within a given time period. This is useful for chemical applications and soil applications. However, in the high temperature chemistry reactions seen in the EAF there is very little correlation to the lime quality as related to the reactivity test. Important factors for lime are the sulfur content, silicon content, LOI and lime sizing. What makes lime go into solution quickly is the fluxing agents that react with lime in this environment. FeO is the primary fluxing agent with silicon and aluminum acting to help also flux lime.
What is typical lime consumption for the electric furnace practice?
Lime consumption depends on the material input and quality of the material which contains acidic compounds such as silicon and aluminum. To maintain the proper B3 ratios of 1.5 to 1.9 depends on the steel quality being produced and the balance of fluxes with the material quality that is added to the furnace. Lime consumption can therefore range from 50 lbs per ton of steel to 110 lbs per ton of steel.
How does lime melt in the furnace when temperatures reach about 3000° F and lime melts at 4,658° F ?
Key requirements involved are the generation of iron oxide (FeO) as the primary fluxing agent, MgO content which along with temperature and slag basicity influences a reduction in the melting temperature of the lime.
Why is adding more lime to the BOF a problem when trying to reduce Phosphorous?
Basicity is an important factor in reduction of phosphorous in the BOF. However, the increasing amount of lime usage will increase the basicity to a point that without any fluxing agents present the slag will become crusty and will not mix with the steel to promote phosphorous removal in the steel. Silicon content of the metal provides the fluxing of the lime since FeO is extremely low in BOF slags as compared to EAF slags. Alternate materials could be used to lower the basicity ratio so that a creamy slag can react during mixing for phosphorous removal.
What kind of PPG do my workers need?
Always wear safely glasses preferably with side shields. Other PPG includes long sleeve shirts, long pants, high topped boots, dust masks and gloves. Quicklime is a caustic chemical and can dry out and irritate the skin. Eye wash stations are also a good idea in case quicklime accidentally infiltrates the eyes.
What references are available that describe lime-based and other options for flue gas desulfurization (FGD) and compare costs of leading systems?
A good general reference produced by US EPA, Controlling SO2 Emissions: A Review of Technologies, is available through the National Technical Information Service ([EPA/600/R-00/093, Order No. PB2001-101224; Telephone: 703-605-6000; 800-553-6847 U.S. only]. Leading FGD systems for large industrial or power generating plants are wet lime FGD, dry lime FGD, and wet limestone FGD. Lime-based systems have lower equipment costs than limestone-based systems. Wet lime systems are suited for flue gases with all ranges of sulfur dioxide content up to 10000 parts per million by volume of sulfur dioxide and where up to 99% sulfur removal is required. Dry lime systems have the lowest equipment costs and are suited for flue gases with less than 1500 parts per million by volume of sulfur dioxide and where up to 94% sulfur removal is required.
I require FGD, but I have no space on my site for disposal of FGD by-products. Are there lime-based FGD systems that produce by-products which I can sell or provide for beneficial uses?
Yes. Lime-based systems can produce by-products both for sale and for a number of beneficial uses. Wet lime systems produce gypsum (calcium sulfate), a beachsand-like product which is purchased by building products manufacturers for production of plasterboard. Gypsum is also used by cement manufacturers as a set retarder. In some areas of the US, agricultural soils are deficient in sulfur or high in alkali, and gypsum is used as a soil amendment to increase crop yields. Dry lime FGD systems produce dry by-products rich in alkali which have also been used for soil amendment. Additional beneficial uses for lime FGD by-products include structural fill, mining mortars, and production of lightweight aggregate.
What is the difference between wet and dry lime-based FGD systems?
Wet and dry systems are distinguished mainly by the type of by-product produced immediately after capture of sulfur dioxide. In dry lime FGD, the product of reaction of lime with sulfur dioxide is a dry powder. In wet lime FGD, the reaction product is a liquid. In dry FGD, milk of lime is sprayed directly into hot flue gas containing sulfur dioxide. Sulfur dioxide reacts directly with lime, and the heat of the flue gas evaporates water in the milk of lime, leaving a dry by-product. The by-product is removed from the gas using either fabric filters in a so-called baghouse or in an electrostatic precipitator. In wet lime FGD, sulfur dioxide is removed from flue gas using a two-step chemical process, compared with dry FGD which is a one-step process flue gas containing sulfur dioxide flows into the side of and up through a cylindrical vessel called an absorber (see figure). A liquid mixture of water, products of previous reaction of sulfur dioxide and lime, including an alkaline salt (magnesium sulfite), is sprayed into the gas from above. Sulfur dioxide is grabbed by the alkaline salt and is absorbed into the liquid mixture (step 1). The liquid mixture containing sulfur dioxide falls into the bottom of the absorber, where a pool of the liquid mixture is held. The sulfur dioxide, which is acidic, lowers the pH of the liquid pool. Milk of lime is then added to the pool to raise pH to about 6. Calcium hydroxide in the lime reacts with most of the sulfur dioxide to form a solid by-product, and magnesium hydroxide reacts with the remainder of the sulfur dioxide to replenish the alkaline salt (step 2). The replenished liquid mixture is then available to be sprayed again into the top of the absorber tower to remove sulfur dioxide from additional flue gas.
Are dry FGD systems only suited for smaller industrial applications?
Dry lime-based FGD systems are suitable for both small industrial applications and large applications including coal and oil-fired power generating systems.
I have other pollutants in my flue gas that I need to remove in addition to sulfur dioxide. Will a lime-based FGD system remove other pollutants?
Lime will remove additional acid gases such as hydrogen chloride (HCl), hydrogen fluoride (HF) and sulfur trioxide (SO3). Wet lime and dry lime systems achieve over 95% removal of HCl and HF, and dry lime systems also achieve over 95% removal of SO3. Sulfur trioxide in combination with moisture produces acid mist, which produces a dark brown or bluish plume and greatly increases visual opacity of flue gas. Mercury is also efficiently removed by lime-based systems. Dry lime FGD in combination with activated carbon is a proven technology for removal of more than 70% of mercury from flue gases produced by incineration and other industrial facilities. Wet lime scrubbers efficiently remove water-soluble forms of mercury.
Can I purchase lime already in slurry form to avoid having to purchase, operate, and maintain slaking and slurry making equipment?
Ready made lime slurry products (Milk of Lime) are available from Carmeuse under the product name “Aquacal” from certain production locations. We would be pleased to hear from you regarding your Aquacal requirements.
Should I use quicklime, hydrated lime or Milk of Lime?
This will depend on factors like whether you already have good reliable storage and handling equipment, the quantity of lime you require, and the amount of labor available to manage the process. Milk of lime is delivered as a ready-made slurry requiring only a slurry storage system. No storage silos or slaking equipment is needed. This product has the highest direct cost, but no costs associated with silo storage and slaking. After that hydrated lime then quicklime reduce in overall product cost, but increase in handling costs.
What ASTM Specifications does Rockwell's products conform to?
C-207 – Standard Specification for Hydrated Lime for Masonry Purposes
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Miracle Morta-Lok – Type “S” Masons Lime – Bagged/Bulk
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Miracle E-Z Spread – Type “SA” Stucco Lime – Bagged/Bulk
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Miracle Lime –Cote – Type “S” Finish Lime – Bagged/Bulk
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Miracle Tiger Airo – Type “SA” Stucco Lime – Bagged/Bulk
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Miracle Tiger Jiffi Soak – Type “S” Finish Lime – Bagged/Bulk
C-206 – Standard Specification for Finish Hydrated Lime
What is the difference between Type “S” Lime and Type “S” Mortar?
Type “S” mortar is a blend of cement, lime, and sand either by proportion or property that meets Standard C-270 where Type “S” lime is just one of the ingredients of the mortar.
What advantages does Type “S” Lime add to a Portland/Lime mortar?
Do cement/lime mortars work with all types of building materials?
Lime/Cement mortars have excellent compatibility with all types of clay bricks and concrete masonry units.
Do mortars made with lime /cement have better potential for reduced water penetration?
Studies have shown that lime/cement mortars minimize the potential for water penetration. (A copy of these studies available upon request) through better extent of bond and autogenous healing.
What is Autogenous Healing?
When hairline cracks develop in the mortar hydrated lime reacts with carbon dioxide in the atmosphere. This reaction produces limestone which helps to seal the crack and fill the voids in the mortar. This explains the increased moisture resistance noted after six months of curing in two studies.
