Quicklime / Calcium oxide
|Place of Origin: Portugal||Type: Quick Lime||Shape: Powder||Raw Material: Limestone|
Quicklime can be used as a component of continuous casting lubricants, and slaked lime as a lubricant carrier in wire drawing.
Continuous casting can also be used for materials based on different types of metals, such as aluminium. Aluminium based metals possess numerous desirable qualities and are used for a number of different products such as food and drink cans, to the construction of large international aeroplanes.
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.
PVC itself is rated as one of the most valuable products in the chemical industry, and throughout the world over 50% of PVC manufactured is used for construction. As a building material PVC is cheap, durable, cost effective and easy to assemble. The uses of rubber range from household to industrial products, including the eraser on the end of your pencil, to the tyres on your car.
Lime can be used to make fillers and coating products which are used within the paper industry. Hydrated lime is used in the sulphate process during the manufacture of paper and pulp.
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 due to its lower content of organic matter.
The use of lime in the process also reduces the requirement for expensive decolouriser additives.
Iron and steel
In many countries, lime is used more for iron and steel making than for construction and building. Most of the lime used is for removing impurities in the basic oxygen steelmaking (BOS) process. The BOS process is now used for 70% of the worlds steel production, with the remainder being in electric arc furnaces (EAF).
Although widely known as Soil Stabilisation, there are a number of distinct processes which can be carried out by the addition of quicklime to waterlogged, clay bearing or contaminated land. Improvement is the first process step, which is the drying out of water bearing material by the heat generating reaction with quicklime, this also converts some of the free water to hydrated lime. Using this process, it is possible to convert an unworkable site into a solid working platform providing a base for construction development, or alternatively as a potential area for agricultural use.
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.
Current cement-lime mixes provide the most efficient mix in regards to 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:
- 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.
- 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 the healing of cracks, which reduce the strength of the masonry unit and increase water penetration.
- Mortars containing lime absorb carbon dioxide from the atmosphere which dissolves within any water present in the mortar, and reacts with the lime to produce 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.
Mortar is essential in the construction industry, without it we would have nothing to hold the bricks together that form our houses, offices and other buildings.
Limewash is a traditional method of painting walls with a colour base that allows the masonry to breathe, providing both protection and aesthetic appeal.
Limewash is also widely used in agricultural buildings due to its germicidal qualities coupled with its extreme ease of application and low cost.
Often referred to as Stabilisation/Solidification (S/S), lime can also be used for the remediation of land affected by contamination, as commonly found on brownfield land or derelict sites. S/S is a civil-engineering-based remediation technique in which contaminated soil is mixed with lime and cement to improve its engineering properties and immobilise contaminants. The dual action means that it is suitable for both land of poor engineering properties and land affected by contamination. A large majority of derelict and brownfield land sites are made up of poor land containing contaminants and so S/S provides a practical technique that provides cost-effective remediation. In addition, (S/S) is also a useful technique for treating particular wastes before disposal to landfill.
Quicklime 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 will help to speed pH adjustment which can help to treat conditions.
(also calledBordo Mix) is a mixture of copper(II) sulfate (CuSO4) and slaked lime used as a fungicide in vineyards. It is used mainly to control garden, vineyard, cocoa plants, nursery and farm infestations of fungi, primarily downy mildew, which can result from infections ofPlasmopara viticola.
In addition to its use to control fungal infection on grape vines, the mixture is also widely used to control potato blight, peach leaf curl and apple scab. It is approved for organic use, so is often used by organic gardeners where nonorganic gardeners would prefer other controls.
Bordeaux mixture achieves its effect by means of the copper ions (Cu2+) of the mixture. These ions affect enzymes in the fungal spores in such a way as to prevent germination. This means Bordeaux mixture must be used pre-emptively, before the fungal disease has struck.
Bordeaux mixture can be prepared using differing proportions of the components. In preparing it, the CuSO4and the lime are dissolved separately in water and then mixed. Calcium oxide (burnt lime) andcalcium hydroxide (hydrated lime) give the same end result, since an excess of water is used in the preparation.
The conventional method of describing the mixture's composition is to give the weight of CuSO4, the weight of hydrated lime and the volume of water, in that order. The percentage of the weight of CuSO4to the weight of water employed determines the concentration of the mixture. Thus a 1% Bordeaux mixture, which is typical, would have the formula 1:1:100, with the first "1" representing 1 kg CuSO4(pentahydrated), the second representing 1 kg hydrated lime, and the 100 representing 100 litres (100 kg) water. As CuSO4contains 25% copper, the copper content of a 1% Bordeaux mixture would be 0.25%. The quantity of lime used can be lower than that of the CuSO4. One kg of CuSO4actually requires only 0.225 kg of chemically pure hydrated lime to precipitate all the copper. Good proprietary brands of hydrated lime are now freely available, but, as even these deteriorate on storage (by absorbing carbon dioxide from the air), a ratio of less than 2:1 is seldom used, which corresponds to a 1:0.5:100 mixture.