Calcium Carbonate

Limestone

Limestone (calcium carbonate) is one of the most common types of rock found on the surface of the Earth. About 10% of the land surface of our planet is made of limestone or similar types of rock. More than 40 0f common industries used limestone in various amounts & forms.

Limestone is a rock that contains a significant quantity of calcium carbonate (CaCO3) as a calcite mineral. The remaining constituents may include other carbonate minerals such as dolomite, (CaMg (CO3)2 and less commonly aragonite (CaCO3).

Pure calcite, dolomite, and aragonite are clear or white minerals. However, with impurities, such as sand, clay, iron oxides and hydroxides, and organic materials, the rock can take on a variety of colors. Consequently, limestone is commonly light-colored, usually tan or grey.

Naturally, calcium carbonate occurs in three common forms – chalk, limestone, and marble.

Chalk is a soft rock consisting predominantly of coccoliths (microscopic shells of marine organisms). Chalk occurs over large areas of northern Europe.

Limestone is formed by the accumulation of shells and shell fragments, or by direct crystallization of calcium carbonate from water. Most limestones are of marine origin, formed in shallow water, typically at depths of less than 20 m. A few were formed in lagoons or in fresh water. Limestone can be grouped as constructional, shell, and metamorphic types.

Marble is formed by the metamorphism of limestone. If the limestone contains other materials such as sand and clay, the calcite will react with them to produce calc-silicate minerals such as tremolite, epidote, diopside, and grossular garnet.

Types of calcium carbonate-containing rock are excavated and used by industry. extensively in the construction industry and neutralize acidic compounds in a variety of contexts.

In the chemical industry, large quantities of limestone are heated to ca 1500 K to form calcium oxide, known as quicklime. Water can be added to lime to form calcium hydroxide.

Applications of Limestone

Limestone) Calcium carbonate (is available in many forms according to it its size and processes. A significant amount of global calcium carbonate produced is consumed for the manufacture of paper and plastics. Additionally, calcium carbonate is utilized in a wide range of applications in paints and coatings, in cement for the building and construction industry, and as a calcium supplement in the medical and pharmaceutical industries.

1. Crushed Limestone

1.1 Aggregates

1.1.1 Concrete

Concrete is a composite construction material, composed of cement, aggregate (generally a coarse aggregate made from crushed rocks such as limestone, or granite, plus a fine aggregate such as sand), water, and chemical admixtures.

1.1.2 Construction

Limestone aggregates are used in a variety of ways in construction projects including drainage & pitching, pipe bedding, and foundation footings.

1.1.3 Landscaping

Decorative limestone aggregates, chippings, and grits are used in landscaping projects such as cycling ways and footpaths, driveways, and car parks as well as for ground cover in gardens and rockeries.

1.1.4. Roadstone

Limestone aggregates, chatter, and MOT-type roadstone have long been used as a fill or base for the construction of roads and roadbed foundations.

1.1.5 Roof Chippings

Limestone chippings are widely used as a decorative, protective coating for felt flat roofs. The chippings provide a ‘loading’ weight to prevent the felt from being lifted off by the wind as well as protection from the sun which would otherwise soften and degrade the felt.

1.2 Chemical use

1.2.1 Flue Gas Desulphurization

Limestone is used to neutralize and remove acids (Sulphur dioxide) present in the flue gases of power generating facilities and is used in flue gas desulphurization (FGD) at coal-fired power plants and municipal waste-to-energy plants.

1.2.2 Glass Manufacture

Most commercial glasses consist essentially of silica together with soda (Na2O) and lime (CaO), the lime being partly replaced by magnesia (MgO) depending on the application. Lime is introduced into the glass melt as limestone (CaCO3) and magnesia by adding dolomite [CaMg (CO3)2].

1.2.3 Iron Smelting

In iron and steel manufacture limestone is used to remove impurities (usually in the form of silica or sand) from the molten iron in the blast furnace to form a substance known as slag which is easily removed.

2. Dimensional Stone

2.1 Large / Massive

2.1.1 Building and Walling Stone

Limestone is still used as walling stone in house builds and municipal buildings. St Paul’s Cathedral and the Houses of Parliament are built from limestone. Randomly screened limestone is still used for traditional dry stone walling.

2.1.2 Monumental Stone

Limestone blocks and polished panels are a decorative and tasteful choice for architects and builders. The highest grade is monumental stone.

This is a very uniform limestone with few surface imperfections. These properties make it ideal for carving and limestone of this class can hold very fine detail when used in sculpture, headstones, plaques, or ornamental features.

2.1.3 Dimensional Cut Stone

Limestone is easily cut and is used to create a variety of bespoke products used in construction ranging from window cills, mullions, and door sets to steps, flooring, and fireplaces.

2.1.4 Paving Stones

Limestone paving is popular because of its very hard-wearing properties, and its lightly textured surface making it perfect for applications where a flat surface is essential.

2.2 Ground Calcium Carbonate (GCC)

2.2.1 Course to medium ground

2.2.1.1 Agriculture

Calcium Carbonate has long been recognized as a useful addition to soil for agriculture, stabilizing the acidity of the soil, improving crop yields, and minimizing fertilizer use. Calcium carbonate is also used in mushroom growing in the top-dressing applied to the spawn-run compost on which the mushrooms form.

2.2.1.2 Animal & Pet Feeds

GCC is incorporated into animal feedstuffs as a calcium supplement and antacid. High purity limestone, with a low level of acid insoluble compounds, is an essential component of feeds for poultry, pigs, and cattle. Poultry requires grit in the gizzard to assist with digestion and strengthen shells for proper egg production.

2.2.1.3 Asphalt Filler

Asphalt is a mixture of bitumen with sand and aggregate fillers that is used in the construction and repair of roads, car parks, pavements, and driveways. Fine ground limestone (GCCs) is used as a part of the solid aggregate filler mix.

2.2.1.4 Carpet-backing

Limestone is an important filler for strengthening the latex backing of rugs and carpets. Latex-based carpet backing is the coating on the reverse side of a woven carpet that holds the fibers in place and provides a degree of resiliency and stiffness.

2.2.1.5 Ceramics

In low-fire bodies, limestone is sometimes added in small amounts as a filler to reduce fired shrinkage. It is also included in porous earthenware body recipes to prevent moisture expansion (which causes glazes to craze). Limestone is also used as a flux in ceramic glazes.

2.2.1.6 Mining

Powdered limestone is used as a dust suppressant in coal mines and helps provide passive fire protection and prevent explosions underground.

2.2.1.7 Pre-Cast Concrete

The use of ground calcium carbonate (GCC) can improve concrete density, surface finish, and physical properties and gives a lighter colored concrete suitable for architectural applications. It is increasingly being used in applications, such as precast concrete products (block paving, paving slabs, and roof tiles), ready-mixed concrete, and self-compacting concrete (SCC).

2.2.1.8 Synthetic Floor Tiles

Limestone powders are typically used in plasticized PVC and plastisol in applications floor coverings (vinyl flooring, carpet tiles).

2.2.1.9 Water & Waste Treatment

Limestone is used in the treatment of waste and drinking water to remineralize excessively soft water (aggressive to pipes) and to adjust the pH of acidic waters in lakes, waterways, and reservoirs.

2.2.2 Fine/ultrafine ground

2.2.2.1 Adhesives & Sealants

Limestone (GCC) is used as a filler and viscosity control additive in sealants, joint fillers, grouts, and ceramic tile adhesives (CTA’s). Sometimes GCC can constitute up to 80% of the formulation.

2.2.2.2 Food

GCC is used as an inexpensive dietary calcium supplement and antacid. Food grade Calcium carbonate (E 170) is added to all brown and white flour products in the UK.

2.2.2.3 Household Products

Polishing and cleaning products often use limestone as a mild abrasive or inert binder. Finely ground limestone will not scratch glass, ceramics, or steel surfaces.

2.2.2.4 Paper

Fine grades of GCC are used extensively in paper manufacturing. Consistent particle sizing and color are essential. As an alkali material, it reduces the acidity of paper, improving the durability of printed material.

2.2.2.5 Paints

GCC is used as a functional filler and pigment extender in a variety of coatings including decorative paints, industrial coatings, road-marking paints, protective coatings, textured finishes, plasters, and wood finishes.

2.2.2.6 Pharmaceuticals

Calcium carbonate is used as an inert filler in tablets and as a base carrier for veterinary products.

2.2.2.7 Plastics

GCC is widely used as a functional filler in plastic products, comprising up to 25% of the volume, adding density, improving rheology, and reducing cost. GCC is often blended or “coated” with additives such as stearates to aid bonding within the plastic.

2.2.2.8 Rubber

GCC is useful as an extender and in controlling the flow properties of products that are to be molded or extruded.

3. Calcined Limestone

3.1 Lime (Burnt lime, quicklime)

3.1.1 Aerated Concrete Blocks

Quicklime is mixed with cement, sand, water and aluminum powder to give a slurry that rises and sets to form honeycomb structured blocks that have excellent thermal and sound insulation properties.

3.1.2 Contaminated Land

Contaminated land can be treated using lime, dolomitic lime, and/or lime binder mixes to adjust Ph. and immobilize sulphates, phosphates, and heavy metals

3.1.3 Calcium Silicate Bricks

Calcium Silicate Bricks are made by mixing quicklime or hydrated lime with silica sand. The bricks are pressed into shape and then heated in an autoclave, which promotes reactions between calcium and sili-cates in the sand and gives extra strength.

3.1.4 Chemicals

One of the main applications of lime, dolomitic lime, and their derivatives is as a raw material in the manufacture of commonly used chemicals. The two main areas of usage of lime are the production of inorganic chemicals or oil additives.

3.1.5 Biosolids

A wide number of organic and inorganic sludges can be treated using quicklime to increase solids content. Biological sludge can be sanitized by the rise in both temperature and pH, obtained by the addition of lime. Biosolids treatment up to ‘Advanced Treated’ is achievable with this method.

3.1.6 Iron and Steel Manufacture

Lime products are widely used to treat waste In many countries, lime is used more for iron and steel making than for construction and building. Most of the lime used is for fluxing impurities in the basic oxygen steelmaking (BOS) process.

3.1.7 Limewash

Limewash is a traditional form of paint, used for the internal decoration of buildings with solid walls but without damp-proof courses. The moisture content of such walls is frequently high and varies with the seasons, meaning any wall decoration has to be porous.

3.1.8 Motor Oil Additives

Certain oil additives (including those used for motor vehicles) are produced by reacting hydrated limes with alkyl phenates or organic sulfonates. The resulting calcium soaps act as wear inhibitors, helping to reduce sludge build-up and neutralize acidity from products of combustion.

3.1.9 Plastics

Quicklime reacts with any water present to form hydrated lime. This can be useful when dealing with products that are heated during the manufacturing process, such as plastic.

3.2 Hydrated Limestone

3.2.1 Seawater, magnesia water purification

Removing calcium and magnesium ions from water is carried out by water softeners. These are ion exchangers that usually contain Na+ ions, which are released and substituted by Ca2+ and Mg2+ ions. Calcium compounds may be applied for wastewater treatment. Drinking water pH and hardness may be altered by means of calcium carbonate and calcium hydroxide.

3.2.2 Swage & Effluent Treatment

Hydrated limestone is used to remove fats, oil, grease, and suspended solids from wastewater. Removing oil from the wastewater effluents from oil refineries, petrochemical, and chemical plants, natural gas processing plants, and similar industrial facilities throw using the property of precipitation.

Hydrated limestone can be used in industrial wastewater treatment to soften process or boiler feed water, precipitate metals, and non-metals, and adjust pH with membrane treatment.

Hydrated limestone is also used in industrial wastewater treatment to stabilize biosolids by killing pathogens, and viruses and reducing vector attraction to produce high-quality agricultural fertilizer.

Finally, lime products are used in industrial wastewater treatment for nutrient control of phosphorus, as lime precipitates phosphorous to very low levels without biological treatment.

3.3 Precipitated Calcium Carbonate (PCC)

3.3.1 Paper industry

Precipitated calcium carbonate (PCC).improves the optical properties of paper and decreases the amount of pulp needed to make paper, subsequently reducing the number of trees needed. Filling of paper, especially in cases requiring high brightness. Rosette-type PCC is used in applications requiring opacity improvements and maintenance of caliper at specified levels of weight and smoothness. Rhombohedral PCC products have effects more similar to those of ground CaCO3 products

3.3.2 Paints

3.3.3 Rubber

3.3.4 Plastics

3.3.5 Food & drinks

The small particle sizes and special particle shapes contribute to the development of good-tasting calcium-fortified foods and beverages.

3.3.6 Pharmaceutical

An effective acid neutralizer, PCC is often used in calcium-based antacid tablets and liquids. Being high in calcium content, PCC enables the formulation of high dosage calcium supplements and multi-vitamin/mineral tablets.

3.3.7 Polymers

In rigid polyvinyl chlorides (PVC), such as vinyl siding and fencing, PCC increases impact strength with some of the smaller particles able to replace expensive impact modifiers. Nano PCCs (less than 0.1 microns in size) control viscosity and sag in automotive and construction sealants, such as PVC plastisols, polysulfides, urethanes, and silicones.

3.4 Calcined Limestone with Clay

3.4.1 Cement industry

Chemical Analysis

Physical Characteristics

Limestone in Egypt

From about 10 km south of Luxor up to the area of Cairo, the river Nile is flanked by escarpments of Eocene Limestone of quite varying consistency. The limestone varies from marly, dense rocks with many flint-nodules in the vicinity of Luxor (Thebes Formation) to did not reveal an identified quarry, but only many loose blocks occurring along the Sakkara plateau. Thus, it might be concluded that a limited occurrence of this limestone material was totally mined out, and only remaining loose blocks witness its former existence in this area.

From the time of King Snofru onwards, due to a lack of this high-quality source, the next best quality limestone from the eastern flank of the Nile valley was exploited for casing material of the pyramids. These fine limestones were also mined for many different purposes during the entire Egyptian history, until today, when they mainly supply the extensive lime and cement industries of Tura and Helwan. The ancient gallery quarries, driven deeply into the escarpment serve today in most cases as safe military ordnance depots, unfortunately, off-limits for both archaeological and scientific investigations.

The entire region of the Gizeh plateau up to the escarpments of Sakkara and Mokatam-Tura-Maasara belongs stratigraphically to the Mokatam Group, which is subdivided into quite a number of diverse members and facies, all of them belonging to the upper Lutetian.

The amount of limestone mined in ancient Egypt is in the order of some 20 million tons, bearing in mind that the Cheops pyramid alone contains 2.7 million m3 of almost exclusively limestone of local and Tura-Mokattam provenance. Egypt is a country rich in stone and was sometimes even referred to as the “state of stone”. In particular, Egypt has a great quantity of limestone formation, which the Egyptians called “white stone” because during the Cretaceous period Egypt was covered with seawater.

Limestone seems to have first been employed in the area of Saqqara, where it is of poor quality but layered in regular, strong formations as much as half a meter thick. This limestone is coarse-grained with yellow to greenish-gray shading. The layers are separated from each other by thin layers of clay and the coloration may vary according to layer. It could often be quarried very near the building sites, and quarries have been found at Saqqara, Giza, Dahshur, and other locations.

Presence of huge outcrop calcium carbonate reserve in El Minia areas with high purity CaCO3 “99.65%” content suitable for industrial purposes. The brightness ranges from 91 to 93.5% which is suitable for paper pigment fillers.