Lime and gypsum
- 1. LIME LIME:- Lime is a white caustic alkaline substance consisting of calcium Oxide (CaO), which is obtained by heating limestone and which combines with water with production of much heat. It is also known as quicklime or burnt lime. Types of lime There are many different types of lime 1) Non-hydraulic lime 2) Hydrated lime 3) Hydraulic lime 4) lime sand Non-hydraulic lime (quick lime):- Properties and uses: - Made from limestones containing at least 95% calcium carbonate.
- 2. Calcuim carbonate is burn at 900degree celcius, and carbon dioxide is driven off,leaving calcium oxide(quick lime)in powder form. Water is added to quicklime produce calcuim hydroxide and large amount of heat. It is better for plasters and renders. It is the purest form of Calcium hydroxide. It is the most permeable of all limes. Do not set under water. Non hydraulic lime set by carbonation. It is softer and sets much more slowly. It is used for painting walls. Used to produce medium,coarse and fine set plasters and mortars. Hydrated lime:- Properties and uses:- It is added to cement mortar to increase workability,flexiblity and to increase dry time to avoid cracks. It help to improve moisture damage and freeze -thaw resistence.
- 3. Hydrated lime has low density than quick lime. It is less reactive than quick lime. Used to increase the pH of soil. It is used in white wash mortar and plasters. Hydraulic lime:- Property and Uses:- Produce from limestone containing clay. Set more quickily and harder than other limes. More clay content ,it behave like cement. Hydraulic lime set under water. At 40% silica/alumina,it have maximum strength. It has a low elastic modulus. There is no need for expansion joints. It has lower firing temperature then portland cements. It does not trap moisture in walls. It is very useful damp condition and construction of Bridges,Dams etc. It is used for mortar in thick walls.
- 4. Lime Sand:- Property and uses:- Waste from ground limestone. Fine grade used by for farmers for agricultural lines spread on land to increase pH. It can be used as a sand fraction of mortars. Current market prices:- Rate of lime …… 12/1kg Rate of hydrated lime ……..9/kg
- 5. GYPSUM Gypsum:- Gypsum is a soft white or grey mineral consisting of hydrated calcuim sulphate. It is soft sulphate mineral composed of calcium sulphate dehydrated,with chemical formula CaSO4.2H2O.It is used finishfor walls and ceiling. Properties of gypsum:- It is monoclinic crystaline system. It is may be colorless,white, yellow, blue, grey, reddish brown due to impurities. Its specific gravity 2.31-2.33. It is transparent to translucent with vetrous to pearly lusture. Its surface is abrasion resistance. Gypsum is heated in air it loses water and convert first to calcium sulphate hemihydrate ( Bassanite and plaster) and it heated further to forn anhydrous calcium sulphate (anhydrite) . Gypsum is heated about 300 degree fahrenheit o produce plaster of paris (gypsum plaster). Its hardness coefficient is 2. Its solubility with hot and dilute HCl.
- 6. Its optical property is Biaxial (+). It is flexible and inelastic. Uses of gypsum It is used finishing for wall and ceilings. It is used for manufacturing of wallboard cement plaster of paris. It is used for ornamentel and decoration purpose. It is used for jointing the tiles. It is used for very fine finishing walls. It is used for surgical appliances. It is used for dry wall. It is used for production of plaster of paris. It is used in toothpastes and hair production. Gypsum is used in manufacturing of portland cement. It is used to give color to cosmetics and drugs. Current market prices:- Rate of gypsum……..170/25kg bag