Calcium is the 5th most abundant element in the Earth's crust and limestone/chalk forms 20% of the world's sedimentary rock. Some of the earliest evidence for the use of lime dates back roughly 10,000 years ago.

The Romans used hydraulic lime and lime pozzolan mixtures in many construction projects, including the Appian Way. They developed the technology of lime burning and the use of mortar, cement and concrete, using lime as the binder. They built the first lime factories and discovered that lime also acts as a chemical reagent. In 350BC Xenophon referred to the use of lime for bleaching linen. Almost all of the Mediterranean peoples were familiar with lime as a paint. Lime was also used for tanning leather and was mixed with organic substances to produce putty and glue.

When the Roman Empire fell, however, the Romans took the majority of their technology with them (including the burning of stone) and as a result, the Saxons who followed tended to use large amounts of timber for construction, meaning there was a significant period of time when stones/rocks/lime were rarely used. Lime was finally re-introduced when the Normans arrived and used lime for the construction of a number of religious buildings.

Today, lime products are being used to restore historical buildings back to their former glory, as well as for constructing new build properties.

1. Glass Limestone and lime products are used in the manufacturing process. 2. Buildings Lime can be used in mortar, bricks, blocks and plaster. 3. In Your Kitchen Keeps fruit fresh after it is picked Used in fish farming Used in chicken feed Makes drinking water safe Used in sugar making process

4. Soil Stabilisation Lime is used to treat soils to make them safe to build on 5. In Your Bathroom Makes drinking water safe Treats sewage Is in toothpaste Is in cleaning products 6. Iron and Steel Lime is a key ingredient 7. Asphalt Lime can be used in road surfacing

Acid neutralisation:

Hydrated lime, quicklime or dolomite lime is mixed with water to give an alkaline slurry which neutralises the low pH of acids.

Milk of lime can also be used to avoid the need for slurrying equipment. Often insoluble calcium salt is precipitated during the reaction which can help to remove impurities from the system.

Aerated concrete blocks:

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

The heat generated when quicklime reacts with water and the alkaline conditions combined with aluminium powder generates hydrogen bubbles which cause the blocks to rise. The heat generated subsequently causes the slurry to set. The blocks are then heated in an autoclave, which promotes reactions between calcium and silicates in the sand or PFA and gives extra strength. Dolomite lime and/or modified quicklime can be added to reduce excessive shrinkage or cracking, an issue which is increasingly useful for highly stressed materials, such as busy road junctions.

Agriculture:

Calcium Carbonate, quicklime, dolomitic lime and hydrated lime can all be used to adjust the pH of soils to give optimum growing conditions and hence improve crop yields. The use of quicklime, hydrated lime and/or blends of these with Calcium Carbonate and Magnesium Limestone will help to speed pH adjustment which can help to treat conditions.

Aluminium:

Quicklime can be used as a component of continuous casting lubricants, and slaked lime as a lubricant carrier in wire drawing.

Continuous casting can be used for materials based on different types of metals, such as aluminium. The molten strand passes through a cooled mould, which produces a shell of solidified metal. The skin of the metal is in contact with the mould, but high temperature lubricants prevent the solidified metal from sticking, allowing the molten core to escape. Aluminium based metals can then be used for a range of different purposes – from the construction of aeroplanes to tin cans.

Asphalt:

Hydrated lime can be used as an additive to hot mix asphalt, increasing the resistance of the asphalt to water stripping. Lime also acts as a mineral filler and as an antioxidant.

• Water stripping (also known as water sensitivity) - many asphalt-aggregates mixtures suffer a loss of bond between the binder and aggregate in the presence of water. This results in a loss of strength, causing the mixture to fail prematurely. Therefore, many anti-stripping agents are used, including lime, cement, amines, and diamines. Experience in the USA as shown that lime is the most suitable for the widest range of aggregates and asphalts.
• Mineral filler – hydrated lime added as a mineral filler, has been shown to increase the viscosity of the binder, increase the stiffness, tensile strength, compressive strength and resistance to water stripping. All of which increase the durability of the mix.
• Antioxidant – the addition of hydrated lime has shown to reduce the oxidation of the binder, which causes hardening and stiffening leading to premature failure of hot mix asphalts.

Please refer to the Technical section for more detailed information.

Biosolids:

A wide number of organic and inorganic sludges can be treated using quicklime or dolomitic lime to increase solids content. Biological sludge can be sanitised by the raise in temperature and pH obtained by adding these materials. Biosolids treatment is achievable with this method.

Please refer to the Technical section for more detailed information.

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 silicates in the sand and gives extra strength.

Building construction:

Initially lime was the main material used for the production of concrete, but was replaced towards the end of the 19th Century by a superior binder known as Portland Cement. Cement had many advantages over lime-based products, being produced from a wide range of raw materials, giving much greater strength, and being more consistent than natural hydraulic limes,

However, lime still plays an important part in the following areas:

• In the drying, improvement and stabilisation of soils.
• As a component of mortars, exterior rendering and interior plasters.
• As an anti-stripping agent in the production of asphalt and tarmac for road construction.
• As a binder in the productions of a range of autoclaved calcium silicate products (including bricks, aircrete, fire resistant board and concrete).

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 silicates in the sand and gives extra strength.

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 is the production of inorganic chemicals or oil additives.

Inorganics:

Lime or its derivatives are essential building blocks in the manufacture of many inorganic salts such as Calcium Phosphate, a toothpaste additive, Calcium Citrate a food and drink additive and Calcium Nitrite an additive for sludge treatment.

Oil additives:

Hydrated lime is widely used in the production of oil additives for lubricants specifically sulphonates, phenates and salicylates. The oil additives are used as detergents and improve the life of engines in cars, ships, etc...

Chicken feed:

Lime from sugar refining plants can be used as one of many ingredients needed to produce vital chicken feed supplements. A mix is created which is subsequently dried and hardened to form pellets. The supplements are given to the chickens to improve and increase the strength of their egg shells. In general, the supplement is simple, efficient and inexpensive to make and use.

In addition, hydrated lime can also be added to chicken litter, used in intensive poultry farms, to extend the life of the litter and provide a degree of protection against parasites and disease.

Contaminated land:

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

Desulphurisation:

Flue gases and acid effluents containing oxides of sulphur can be treated by introducing limestone, chalk, quicklime or hydrated lime as a powder or slurry, promoting a reaction to form insoluble calcium sulphate or gypsum which can then be collected. If carried out under the correct conditions this process can produce a saleable gypsum co-product.

Drinking water:

‘Slaked’ lime is widely used in the production of water for human consumption, in fact in terms of quantity, it even competes with chlorine as the major chemical used in water treatment.

Water treatment is comprised of several basic processes, depending on the impurities that need to be reduced. They are as follows:

• The removal of suspended/colloidal matter (helping to reduce taste, odours and colouration).
• Reducing hardness.
• Reducing the concentrations of dissolved metals.
• Disinfection.
• pH adjustment.

Overall a wide range of chemicals are used in water treatment. Lime is used both as an alkali and as a source of calcium ions.

Effluent treatment:

Lime products are widely used to treat waste and effluent water in order to:

• Neutralise acids
• Adjust pH prior to further treatment or discharge
• Precipitate metals
• Precipitate sulphate and fluoride
• Reduce nutrients (phosphates and nitrogen)
• Modify the characteristics of the sludges produced by the treatment

The greater use of lime than of competitive alkalis reflects its higher cost-effectiveness, its efficiency in removing most heavy metals and the better physical and chemical sludge characteristics that are generally obtained.

Fish farming:

The pH of acidic ponds and lakes can be controlled and raised using hydrated lime. In general terms this creates a more hospitable environment for aquatic organisms, in particular fish. Lime is therefore used by fish farmers to maintain a suitable habitat for breeding fish.

Flue gas treatments:

Lime, being the most cost effective alkali, is widely used in the removal of acidic gases emitted by power stations.

Lime based techniques for the abatement of acidic gases can be divided into 5 groups:

• Wet scrubbing – where gases are treated with milk lime to remove SO₂ (Sulphur Dioxide) and neutralisation products are removed as a suspension.
• Semi-dry scrubbing – where milk of lime is sprayed onto the gases to remove SO₂ (Sulphur Dioxide) and reaction products are removed with a dust collector.
• High temperature (over 850°C) dry injection of hydrated lime – where the hydrated lime calcines and the resulting calcium oxides reacts with the acid gases (SO₂ ). Reaction products are also removed using a dust collector.
• Low temperature (below 300°C) dry injection of hydrated lime – removes HC1, HF and SO₂ . Similarly, reaction products are removed using a dust collector.
• Low temperature (below 300°C) absorption by hydrated lime – in a fixed bed used to remove Hafnium from kilns calcining ceramic products.

DOWNLOAD LINK Grimsby Operations: flue gas treatment - 28 kb

Fruit farming:

As apples and other fruit ripen, they emit carbon dioxide. When in storage, the carbon dioxide lowers the level of oxygen in the atmosphere and accelerates the rate of deterioration of the fruit. By circulating air around the fruit and over hydrated lime, the level of carbon dioxide is reduced and the fruit remains fresh and useable for longer.

Residues from processing citrus are mixed with lime, dried, and sold as cattle feed. Lime can also be used to neutralise waste citric acid and to raise the pH of fruit juices to stabilise the flavour and colour.

Glass manufacture:

Although limestone is generally more cost effective in the production of glass, dolomitic and high calcium lime in finely ground forms can also be used under specific circumstances. Burnt lime often provides greater transparency to the glass than limestone on account of:

• Its lower content of organic matter.
• The iron oxide being present in the ferrous rather than the ferric form.

Both of the benefits, also reduce the requirement for costly decolouriser additives. In glass processes using medium to fine grained materials, the replacement of limestone by burnt lime has been reported to increase solution rates and reduce heat requirements, therefore increasing the production capacity of a furnace.

Incineration:

The continuing demand for power has resulted in an increase in the burning of fossil fuels. Many such fuels contain sulphur and the resultant emissions into the atmosphere are the principal cause of acid rain. Other sources of acid rain can be incinerators whether they burn municipal or industrial waste, clinical waste, animal carcasses or natural fuels. Almost all incinerators around the world have utilised lime as a means of removing harmful gases for many years and proved lime to be cost effective, efficient and sustainable.

Lime is sprayed into the flue gas stream in the form of a dry powder or as a suspension in water. It then reacts with the pollutants to form an insoluble salt which is easy to dispose of. In the case of desulphurisation it is possible to produce quality gypsum (calcium sulphate) which can be used as a raw material in plaster or plasterboard.

Iron and steel manufacture:

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. Lime is also used in similar quantities in the following:

• The sinter strand process for the preparation of iron ore.
• In the desulfurisation of pig iron.
• As a fluxing agent in other oxygen steelmaking process.
• In the electric arc steelmaking process.
• In many of the secondary steelmaking processes.

In fact, the BOS process replaced the Bessemer and open hearth steelmaking processes during the 1960’s and caused some major changes in both the steel and lime industries. The process is now used for 70% of the worlds steel production, with the remainder being in electric arc furnaces (EAF).

Please refer to the Technical section for more detailed information.

Leather tanning:

Hydrated lime helps to de-hair and "plump" hides before the tanning process is completed.

Lime Concrete:

Lime concrete or "limecrete" is made by mixing controlled amounts of sand, aggregate, binder and water. Portland Cement is normally used as the binder, although nowadays hydraulic lime or hydrated lime plus a pozzolan can also be used.

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.

Limewash is also widely used in agricultural buildings due to its mild germicidal qualities coupled with its ease of application and relatively low cost. In addition, it has also been recommended by the Building Research Establishment (BRE) for use on bituminous surfaces, such as flat roofs to reduce radiant heat absorption from sunlight.

Mortar:

Similar to the production of concrete and plasters, lime was the initial ingredient that was slowly replaced by Portland Cement that proved to be more beneficial due to its consistency and rapid development of strength. These cement-sand mortars however, proved to be almost too strong for most purposes, and the introduction of cement-lime mixes were proposed in the late 1800’s. This mix provided an even more efficient mix possessing both good ‘soft’ properties as well as controlled strength.

The benefits of using lime and lime-cement mortars can be divided into two categories; ‘soft’ and ‘hard’ characteristics. They are as follows:

Soft characteristics:

• They have high workabilities.
• Their water retentivities are very high, making them particularly suitable for use with absorptive units.
• The set times and 7 day strengths of lime-cement-sand mortars can be controlled by the amount and type of cement.

Hard characteristics:

• The compressive strength of lime-cement mortars can be adjusted to the required level by the selection of the mix design.
• Incorporating lime in mortar improves adhesion and reduces rain penetration.
• The presence of lime can often increase the resistance of mortar to attack by sulphate.
• It confers autogenous healing of cracks, which reduce the strength of the masonry unit and increase water penetration.
• Mortars containing lime induce carbon dioxide from the atmosphere which dissolves in the water in the mortar and reacts with the lime to produce insoluble calcium carbonate crystals. These crystals form in available spaces such as cracks and grow, thereby sealing the cracks. This ‘self healing’ characteristic reduces water penetration and increases durability.

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 neutralise acidity from products of combustion.

Paper manufacture:

By using the lime cycle, we can increase the purity and consequently the brightness of a calcium carbonate by calcining, hydrating and then re-carbonating back to calcium carbonate. This process is used to make fillers and coating products which are used within the paper industry.

The caustic properties of hydrated lime are used in the sulphate process during the manufacture of paper and pulp. About 250kg of quicklime per tonne of pulp are required for causticisation.

Plaster:

Internal plastering is used to cover up differences in level and to provide a surface which is suitable for the final decorative finish. Until the late 1800’s, internal plasters were predominantly lime based until the advantages of gypsum and cement became apparent. These binders gave faster setting and higher crushing strengths than the traditional lime plasters.

It was subsequently found however, that the use of lime gauged with cement or gypsum, to obtain the required setting time and strength, improved both the handling characteristics and the durability of plaster. Other benefits are described as follows:

• Plasters containing lime have excellent workabilities, are highly cohesive and eminently suitable for mechanical plastering techniques.
• Setting times and crushing strengths can be controlled by selecting the most appropriate mix design.
• The high water-retentivity of lime based plasters, coupled with their high workability, ensures a good bond to the background material (particularly beneficial with porous backgrounds).
• The ability of lime to promote autogenous healing of cracks helps to ensure its durability by reducing water penetration.
• The high alkalinity of the plaster inhibits the growth of mould and the corrosion of iron and steel.

In general the benefits raised from the addition of lime in the plaster, far outweigh the small increase in raw material costs.

Plastics:

Quicklime reacts with any free water present to form hydrated lime. This removes water from the system and can be useful when dealing with products that are heated during the manufacturing process, such as plastic. When making plastic, if any potential water is not removed then steam bubbles may occur in the finished product, which can affect its strength and appearance. Quicklime is therefore often used in PVC and rubber manufacturing processes.

Renders

External rendering mortars are used to enhance the appearance of buildings and to make the structure waterproof. Lime renders help by acting like a sponge, absorbing rainfall then allowing it to evaporate rather than soak into the wall.

As with many lime applications, the use of lime was almost made redundant by the introduction of cement in the late 1800’s. However, it was discovered that excessively high cement contents caused problems and that the use of cement-lime mortars gave significant improvements in both the ‘soft’ and ‘hard’ characteristics.

Overall renders and plasters can be applied to a variety of backgrounds including earth (which should nearly always be rendered), stone and brick. Lime based renders now offer the best performance possible, benefits include; vapour exchange, water resistance, elasticity, compatibility with all types of background and even eco friendliness.

Restoration:

Buildings pre 1900 would not have been built with cement (with few exceptions in the late 19th century) but with a lime mortar. Therefore in order to conserve these buildings it is essential to use similar materials when doing so. To introduce cement or cementitious mortar would cause decaying due to the difference in chemical composition of cement and inevitably result in irreversible damage. Lime mortars, lime plasters and renders and lime putty are therefore all used for the restoration of the UK and the majority of Europe’s built heritage.

DOWNLOAD LINK Devonshire hospital - 28 kb

Sewage works:

Sewage generally consists of both domestic and trade effluent. It contains suspended solids, dissolved colloidal organic matter, nutrients (phosphate and ammonia) and even heavy metals (particularly from trade effluents).

Lime products have been used extensively in the treatment of sewage for over one hundred years. Its roles have included the following:

• The adjustment of the pH of the incoming sewage.
• Coagulation and flocculation of the solids.
• Removal of metals and nutrients.
• Disinfection.
• Conditioning the sludge for agricultural use or as a landfill.

Sewage treatment currently uses a combination of mechanical, biological and chemical processes to produce a discharge of the required standard at the lowest possible price. In most countries, the requirements for the discharged water is becoming more and more stringent, causing rapid changes in the industry which may well present huge opportunities for increased lime scales.

Sludge treatment:

A wide number of organic and inorganic sludges can be treated using quicklime or dolomitic lime to increase solids content. Biological sludge can be sanitised by the rise in temperature and pH obtained by adding these materials.  Biosolids treatment is achievable with this method.

Please refer to the Technical Section for more detailed information.

DOWNLOAD LINK Strategic use of liquid lime in sludge treatment - 139 kb

Soil stabilisation:

Lime treatment for soils, often involves the use of quicklime, or slaked lime, either as powdered hydrated lime, or as milk of lime. The effect of adding lime to soils can be divided into three distinct stages; drying, modification, and stabilisation.

• Drying- occurs when quicklime is used. The quicklime hydrates, absorbing water and generating heat, which in turn causes some of the water to evaporate. Total water moisture loss can be up to double that required to hydrate the quicklime. The drying process occurs almost immediately with reactive quicklimes.
• Modification - occurs with both quick and slaked lime, which rapidly enter into the physio-chemical reactions with any clay minerals present. The resulting changes include ion exchange and can occur within 6 hours, dramatically reducing the plasticity of the soil but increasing its workability and improving its compaction characteristics.
• Stabilisation - is often a much slower, occurring overall several months it involves the reaction of lime with the siliceous and aluminous components of the soil. The addition of lime raises the pH of the soil to above 12, resulting in the formation of calcium silicates and aluminates. These are believed to form initially as gel, which coats the soil particles, and subsequently crystallises as calcium silicate/aluminate hydrates. Those hydrates are cementitious products, similar in composition to those found in cement paste. The resulting gain in strength is progressive.

After the drying and modification stages, water is added to obtain required moisture content for consolidation. The soil is then compacted to reduce the level of air voids to no more than 5%, ensuring that the stabilisation reaction proceeds in the compacted state and results in a homogenous, impermeable and stable layer. The stabilised layer has a low and acceptable shrink-swell potential, and improved compressive, tensile and flexural strengths. It also reduces the susceptibility of the stabilised layer to frost damage.

Please refer to the Technical Section for more detailed information.

Sugar processing:

• Sugarbeet - The production of sugar from sugarbeet requires approximately 200kg of quicklime per tonne of sugar. The raw beet is washed and chopped and treated with hot water to extract the sugar. The sugar solution also contains dissolved, suspended and colloidal matter. The extract is initially treated with excess lime, which raises the pH and precipitates insoluble calcium salts of both organic and inorganic acids. Carbon dioxide (CO₂) is then passed through the suspension to precipitate excess lime as calcium carbonate (CaCO₃). The precipitation process removes suspended and colloidal matter as a ‘carbonation sludge’ which is then removed by filtration. The filtrate is a solution of sugar and is recycled. Many sugarbeet processing plants operate their own lime kilns on site in order to produce the quicklime and CO₂ needed for the process.
• Sugarcane - ‘Slaked lime’ is used in the production and refining of sugar. Sugarcane is cut, shredded and treated with water to produce raw juice with a pH of 4 to 5. The juice is treated with lime to raise the pH and heated to approximately 70-75°C to destroy invertase and other enzymes. Roughly 2-5kg of hydrated lime is used per tonne of sugar produced.
• Sugar from other plants - Sugar is also extracted commercially from certain species of palm, from the sugar maple and from sweet sorghum. Lime is used to purify the extracts before evaporation.

Wildlife sanctuaries:

Old quarries are restored using inert waste. Restored land often maintains a higher level of biodiversity than the area did prior to quarrying. In fact, the majority of restored sites are now categorised as ‘National Nature Reserves’ or ‘Wildlife Sanctuaries.’  A number of old quarries also transform into shallow wetlands which provide habitats for a wide array of rare and endangered bird species. Over 700 Sites of Special Scientific Interest (SSSI’s) have been designated on former quarries, a large number of which were used to quarry limestone/chalk.

Wire drawing:

Hydrated lime suspensions or milk of lime is used to neutralise and coat wire after it is acid cleaned. This acts as a slip agent to reduce friction during the drawing process and helps protect the wire during storage.