Limes

Limes- Building Construction Material

1. Limes Building Construction Material

2. Syllabus Lime: Introduction, classification, manufacturing, slacking, properties, tests, handling, storage and uses

3. Introduction Lime is an important cementing material used in engineering construction. A Cementing material may be defined as that material which has capacity of holding structural unit to-geather with sufficient strength . Among this group are included lime, natural cements, gypsum, Portland cement as well as various other synthetic products .

4. Limes

5. Introduction Cementing material: The material which has the capacity of holding structural units (like bricks, stones, aggregate) Examples: Lime, natural cements, gypsum, Portland cement Lime is an oxide of calcium, CaO Uses: . Ordinary buildings, massive monuments, palaces, forts As a Reliable and economical cementing material .

6. Lime : As a Reliable and economical cementing material

7. Classification Lime is available in the market in three main types which are Quick lime, Hydrated lime , Hydraulic lime Classification: based on its composition i) Quicklime ii) Hydrated lime iii) Hydraulic lime

8. Lime Cycle

9. Classification Quicklime: also called Fat lime, Rich lime, Pure lime. In it CaO is greater than (93%) by weight, remaining being MgO and very little clay. Quick lime is Amorphous (shapeless) white material . It has very high affinity for water and carbon dioxide. It Will Absorb the moisture quickly from atmosphere and converting itself to a carbonate of calcium, CaO + CO 2 = CaCO 3 CaO + H 2 O = Ca(OH) 2 Ca(OH) 2 + CO 2 = CaCO 3 + H 2 O

10. Manufacturing Of Fat Lime The essential raw material for the manufacturing of quick lime is a rock called LIMESTONE CaCO 3 . Limestone is a sedimentary rock which occurs in nature in good abundance forming hill ranges, plateaus.

11. Quicklime

12. Classification Hydrated Lime: It is that lime to which sufficient quantity of water has already been added at the manufacturing stage to hydrate (slake) it completely. In composition, it is Ca(OH) 2, In structure, it is in powder form, It comes in ready to use form compared to fat lime that has to be hydrated or slaked before using. Lime can also be converted to hydrated form at the place of construction, the method is called slaking of lime.

13. Hydrated Lime

14. Classification Hydraulic Lime: It is different in chemical composition form fat lime in that it contains a definite amount of clay in addition to CaO, clay content in hydraulic lime may range from 10 to 30% by weight. This clay plus lime composition gives the hydraulic lime a property of hydraulicity .

15. Hydraulic Lime

16. Hydraulic Lime Hydraulicity: The capacity to set and harden even under water and in the absence of air as between very thick walls” The hydraulic lime is further classified into three sub types on the basis of hydraulicity of the lime. Subdivision based on hydraulicity: Class A – Eminently Hydraulic: clay content 21-30%, sets under water in 24 hours Class B – Moderately Hydraulic: clay content 11-20%, sets in water in about a week Class C – Feebly Hydraulic: clay content 5-10%, sets under water within a month or more Class D – rich in magnesium, suitable only for finishing coats, do not possess hydraulicity

17. Classification of Lime

18. Hydraulicity

19. Classification Lime has also sometimes classified on the basis of raw material as Stone lime, shell lime, and kankar lime. Similarly lime is distinguished into building lime and finished lime. The first type is required to possess good strength and ability to mix with sand . It is used in mortar that are used in walls and foundations. The finished lime however, is required to possess sufficient plasticity, good color and quick setting property.

20. Classification

21. Manufacture Of Fat Lime Common lime stone has following Constitution: Constitution of lime stone rock: Calcium Carbonate (CaCO 3 ) – 60 to 65%, The higher percentage of CaCO 3, the better suited for lime stone for manufacturing of fat lime. Magnesium Carbonate Mg(CO 3 ) 2 – 5 to 30%, It is almost a universal component of many limestones for making fat lime, its content should not be greater than 5% Clay - 10 to 30%, for fat lime its content should be less than 10%, Limestone with higher clay content are more suited for hydraulics lime. Iron, alkalis and sulphates – are present in small proportions in many limestone, when their total content is less than 5% and the CaCO 3 is above 90 % the limestone is suitable for flat lime manufacturing. But when present in excess amount, these salts make the lime unsuitable as a raw material. Besides Limestone, sufficient quantity of fuel is also required to manufacturing lime.

22. Manufacture Of Fat Lime

23. Manufacture Of Fat Lime Calcinations (process of burning): Lime is manufactured by a process of burning or calcinations of limestone in suitable types of kilns. The term calcinations signifies “Heating the material at red heat in the presence of air till it decomposes” Lime stone dissociates when heated at 880⁰ C into its principal constituents; Calcium oxide and carbon dioxide, as per above reaction which is reversible. CaCO 3 ( 880⁰ C) CaO + CO 2 It is essential that, all the carbon dioxide produced during the reaction is removed quickly from the kiln: the dissociation temperature of reaction (880⁰ C ) is not allowed to come down during the burning process.

24. Calcinations

25. Manufacture Of Fat Lime The Burning of Limestone is carried out either in clamps or in kilns. Clamps are temporary, make shift arrangements for burning in an ordinary manner and at a much lower cost. Kilns are, however permanent structures build to carry out the burning operations at a regular intervals or on continuous basis.

26. Clamps & Kilns

27. Manufacture Of Fat Lime – Clamp Burning It is a common method for obtaining small supplies of quick lime. No permanent construction is needed. A Small part of ground is cleared and fuel (wood) stacked in alternate layers with fuel as lower layer. If coal is used as fuel, it is mixed with the limestone instead of stacking in separate layers. The whole heap is covered with mud plaster and small holes are left for escape of carbon dioxide. Clamp Burning

28. Manufacture Of Fat Lime – Clamp Burning Clamp is ignited from the base and allowed to keep on burning for 2-3 days. Burning is discontinued when blue flame disappears at the top and it is allowed to cool for 2-3 days. It is then dismantled. Limestone gets disintegrated into small pieces of small lumps of CaO or lime. Such lumps are separated from the ash by hand picking. Clamp burning is a quick and cheap method for obtaining ordinary type of lime and not suitable for large supplies of fat lime of good quality because; Burning is neither uniform nor complete; Some stones may be over burnt and some may be under burnt resulting in wastage of raw materials; There is considerable Wastage of heat generated by burning of fuel. Some of it escapes from frequent cracking of the plaster on getting heated. Thus this method is not suitable method of producing fat lime on a commercial scale.

29. Manufacture Of Fat Lime – Kiln Burning Most of the Commercial lime is manufactured by burning limestone in kilns, they are Permanent structures, kilns used for manufacturing lime are of great variety and different designs . In principle, however they are either Batch type (intermittent) kiln / Continuous kiln. In the first type of kiln however kilns have to be cooled every time after burning a batch of limestone. The continuous type however are kept in operation all the time unless they are required to be stopped for repair. Further, a kiln may be of mixed type or separate type design. Mixed feed (flame type) kiln – fuel and limestone are in a mixed together batch, burnt lime is obtained mixed with ash and has to be separated from it. Separate feed (flare type) kiln – fuel and limestone are not in contact with each other, fuel is burnt separately, hot gases are allowed to heat limestone and lime is free from ash.

30. Manufacture Of Fat Lime – Kiln Burning Batch type (intermittent) kiln: A typical batch type of lime kiln consist of Permanent brick-walled structure. Its shape size and design may vary from place to place. Rectangular, Oval or Cylindrical shapes are common. The Walls of kiln are generally lined with refractory bricks to save them from disintegration due to repeated heating at high temperatures and cooling. The kiln is provided with Openings for supply of air, permanent roof may or may not be there in kiln. After loading, kiln is ignited at bottom, fire travels upwards and takes 3-4 days for limestone to burn. Thereafter the kiln is allowed to cool by itself and then unloaded and cleaned after which it is loaded with fresh batch of limestone and fuel. Intermittent Kilns

31. Manufacture Of Fat Lime – Kiln Burning (2) Continuous kiln: The essential feature of a continuous lime kiln is that while It is charged regularly from one end with the raw material and the end product is taken out regularly from the other end. As such there is No need to cool the kiln every time after burning a batch of limestone. Naturally its Rate of production of lime is higher than other types of kilns. Continuous kilns are of various Types such as – shaft kiln, rotary kiln, circular kiln etc of these the shaft kiln are most popular. They are made in different design shape and sizes.

32. Manufacture Of Fat Lime – Kiln Burning Mixed feed (flame type) continuous kiln: It may be constructed Partly underground and partly over ground , the kiln consists of a shaft or a cylinder of suitable dimensions, the essential features of which are, Diameter – in middle greatest, at top intermediate and at bottom least Variation in diameter accumulate large amount of limestone in the central part as it is hottest zone and ensures complete calcinations. The shaft is lined internally with refractory bricks A grating plate is at the base of the shaft, which is full of holes to allow the burnt lime pieces to fall down in the collecting chamber. The kiln is provided with a hopper type of arrangement at the top for loading the charge and also draw gates at the bottom for withdrawing the lime after it is cooled. The body of kiln is provided with opening in the lower region for supply of fresh air. It is also provided with observation holes in the middle region for keeping an eye on the reactions. Openings are provided for leading the wastage out of the kiln.

33. Manufacture Of Fat Lime – Kiln Burning At top hopper type arrangement for loading the charge and at bottom draw-gates are provided for withdrawing the lime after cooling. At lower region opening is provided for supply of fresh air, at middle region holes for observation of the reaction and at top openings is for leading the waste gases out of kiln Continuous Flame-type: Mixed Feed Kiln

34. Manufacture Of Fat Lime – Kiln Burning Alternate layers of limestone and fuel is placed and then ignited through burn holes. Main calcinations reaction takes place in the central burning zone of the kiln. At uppermost zone charge is heated up which helps in its quicker calcinations as it slides down. When limestone in the burning zone is completely converted to lime, it slides down and falls into collecting chamber. Hot lime dropped in the basal zone is first cooled by introducing fresh air. The charging and emptying operations are continued in this manner in a regular sequence

35. Manufacture Of Fat Lime – Kiln Burning The kiln is first loaded with calculated amount of fuel and limestone in alternate layers. It is then ignited through burn holes . Man calcinations reaction takes place in the central burning zone of the kiln. In the uppermost zone, the charge is mostly heated up, this helps in quick calcinations as it slides down after some time , when limestone in the burning zone has been completely converted to lime, the latter slides down and falls into the collecting chamber through the holes in the grating. Raking holes are used to turn about the charges during burning.

36. Manufacture Of Fat Lime – Kiln Burning (B) Separate feed (flare type) continuous kiln: Design is similar to mixed feed type it Consists of shaft made of steel or brick, lined internally with refractory bricks. It has Bigger diameter in the central zone for burning, intermediate diameter in the basal zone and small diameter at top for charging. Such a kiln is provided with Separate fuel chamber which is located within the main body or outside the kiln. In first case, fuel chamber is placed in box type around the periphery of the shaft where fuel is burnt to generate heat which is conducted into kiln. In second case, fuel is burnt outside the kiln and hot gases are allowed to enter into kiln. In any case, there is no contact between the fuel and the limestone. After calcinations of limestone, it is made to fall in the lower cooling zone with help of raking rods. The hot lime is cooled by introducing fresh air in the basal chambers and once it becomes hot rises upward in the burning zone of the kiln. There is therefore Better utilization of heat in this kiln. Continuous Flare-type : Separate Feed Kiln

37. Manufacture Of Hydraulic Lime Hydraulic lime has a Clay content is ranging from 10-30 % For the manufacturing of this type of lime, the process depends upon the type of raw material available. (A) Natural Hydraulic Lime: This is manufactured from a single raw material, an impure limestone rich in clay known as Kankar and occur in nature either in the form of blocks or making lower part of the ground at many places. Kankar contains 10-40 % clay and 60-80 % calcium carbonate. Calcinations of kankar is done in clamp or in kiln in similar manner for fat lime. In case of kankar Temperature is raised to higher degree because of presence of enough clay in it and then cooled and packed.

38. Manufacture Of Hydraulic Lime

39. Manufacture Of Hydraulic Lime ( B) Artificial Hydraulic Lime: In this type of lime two source materials are required – limestone rock, clay. Limestone should be free from impurities and clay should not contain any free silica, oxides of iron, sulphur, alkalis . There are two variations of calcinations for the manufacturing of artificial hydraulic lime depending upon the quality of limestone. Calcinations depends upon the quality of limestone. Limestone is of soft type (e.g. chalk) – such a stone is mixed with clay in powdered form and burn to red head in any type of kiln and then burnt mixture is slaked on cooling before marketing Limestone is of hard type (e.g. compact limestone) – Calcined in kiln to obtain quick lime and then cooled and powdered, mixed with clay (10-30 % by weight) and mixture is converted into ball shaped masses These balls are once again charged into the kiln and burnt to red heat so it is known as Twice Kilned Lime

40. Artificial Hydraulic Lime

41. Properties Of Lime Following are the more important properties that determine the quantity of lime as a building material, Physical state: Lime as obtained from kilns is generally in the shape of solid lump it is termed as lump lime. Lime is crushed to obtain powder of required fineness known as Pulverized lime.

42. Properties Of Lime Slaking of Lime or Hydration: the process of chemical combination of lime ( CaO) with a definite quantity of water so that the end product is hydrated oxide. When lime cannot absorb any more water then the process is said to be completed. The new product, Calcium Hydroxide is formed as per following reaction; CaO + H 2 O = Ca(OH) 2 The above reaction is attended by following processes: Evolution: heat is generated of the order of 227 K-Cal/kg of lime Expansion: volume extent up to 2-3 times Development: hissing and cracking sound due to conversion of water into heat Fat lime hydrates in 3-4 hours and hydraulic lime hydrates 1-3 days. All limes must be slaked before use in building construction.

43. Slaking of Lime or Hydration

44. Methods Of Slaking Tank Slaking (Making Lime Putty): Two brick tanks of suitable dimensions are constructed adjoining to each other and with a difference in level. The first tank is about 45 cm deep and made at a height, second tank is 60-75 cm deep and made at a lower level. Water is filled in the upper tank to ¾ th of its depth. Fat lime is gradually added to it in small amounts, water is constantly stirred during the addition of lime. The slaking reaction takes place in this tank, which can be observed by evolution of heat and hissing and cracking sound. 3-4 hours for complete hydration The lime on reaction with excess water forms milk of lime. Screening tap called strainer (with openings of 0.25mm) is opened and the hydrated lime allowed to pass into the lower tank. It is allowed to stay in second day for 2-3 days where it matures itself to the desired consistency. This is ready as Lime Putty and is taken out for use of making mortars and plasters. Tank Slaking

45. Tank Slaking (Making Lime Putty)

46. Methods Of Slaking Precautions Only lime should be added to water not water to lime . Keep water stirring and hoeing for sometimes more even after the boiling and hissing sounds are over in the tank. Lime Putty should be taken out as soon as it becomes mature in the tank it should not be allowed to stiffen and harden before use.

47. Methods Of Slaking Platform Slaking (For powder slaked lime): water-tight platform of masonry or cement-concrete Fat lime is spread in the form of a thin layer of about 15 cm height. Small quantity of water is sprayed. During the water-sprinkling process, lime heap is turned over and over again using spades. When apparent slaking is complete (as indicated by absence of further hissing and cracking sound ), no further water is added. The heap is covered with boards so that any further heat liberated on slacking is used by the lime for its complete disintegration. It is left for 24 hours during which time slaking may be completed. Lime is turned into a powder form of hydrated lime which is screened through 0.25 mesh sieve and ready for use of making mortars and plasters. Platform Slaking

48. Slacking of Hydraulic Lime Slacking of Hydraulic Lime It is done by following three methods Platform slacking Slacking under pressure Slacking by hydrators The basic difference in the slacking of Fat lime and Hydraulic lime lies in the fact that the latter is generally slow slacking and require less water as compared to fat lime.

49. Properties Of Lime Plasticity: It is defined as the ability of the lime to spread evenly during application it is observed that ; Limes contains some magnesium oxide – more plastic, spread smoothly and easily in comparison to Limes rich in calcium oxide Limes rich in calcium oxide – pure fat lime, hard to work, sticky and stiff quickly Sand carrying capacity: When lime is used in mortar or plaster sand has to be mixed with it due to following reasons ; To control shrinkage of lime on setting To prepare a properly plastic mix of desired strength Limes mix with the definite quantity of sand is known as sand carrying capacity of lime. Calcium limes are said to have good sand carrying capacity than magnesium limes

50. Plasticity

51. Properties Of Lime Setting: The setting of fat lime in free state or in mortar is essentially a chemical process which involves following reactions Dehydration – loss of water from the hydrated lime by evaporation Ca(OH) 2 = CaO + H 2 O (b) Carbonation – combining of atmospheric carbon dioxide into lime, forming once again the original material i.e. limestone CaO + CO 2 = CaCO 3 The net result of setting is that it us again converted into hard substance, calcium carbonate this carbonate act as a binding material when used as mortar.

52. Properties Of Lime Setting: The setting of hydraulic lime is a complex process. This is due to the fact that hydraulic lime contains besides oxides of calcium and magnesium, silicates and aluminates of calcium and some oxides of iron. During their setting these compounds get further hydrated and form crystalline structure. It is for this reason hydraulic lime can set under water also. It is more like Portland cement then fat lime. Hydrated fat lime sets slowly compared to pure fat lime. Rate of setting of hydrated lime can be increased by drying air and charging it with CO 2. Shrinkage takes place in lime on setting which can be overcome by mixing sand or surkhi.

53. Handling And Storage Of Lime Handling and storage of lime: Lime in its raw form requires careful handling to avoid accidents and losses Quick lime – should be protected from water, as it will start getting hydrated with the evolution of heat that can cause burn injuries of various serious nature. If it is stored in wooden barrels and it comes in contact with water, so much heat may be evolved to burn barrel, store house or the wagons/trucks in which it is being transported. Fat lime – must be protected from direct contact with atmospheric moisture and carbon dioxide which starts setting and gets converted to a useless hard material having no binding properties. It is therefore required to convert the lime into lime putty as soon as possible and stored into a compact heat covered with a thick layer of lime dust which saves the attack of moist air. (iii) Hydraulic lime – safer in transport and can be stored for longer period as compared to fat lime.

54. Handling And Storage Of Lime

55. Handling And Storage Of Lime Precautions to handle lime: Workers handling lime must be asked to use goggles, respirators, rubber gloves and gum boots for protection of eyes, respiratory system, hands and feet respectively. Thorough bath should be taken after working with lime . Any inflammable material should never be kept near a heap or bag of lime or where lime is being hydrated to avoid any accidental fires.

56. Uses Of Lime Uses of lime : Lime is very useful material that finds extensive applications in building construction, industry and agriculture. (a) As a construction material : Lime was used as main binding material in all types of construction till 19 th century. Even now lime can compete with Portland Cement in many types of construction. as a mortar (lime-mortar) mixed with sand or surkhi. as a plaster as a whitewash which gives sparking white finish at a very low cost as a lime-concrete similar to cement concrete made by mixing lime, sand and coarse aggregate in proper proportions as sand-lime bricks which are quite popular in many countries

57. Uses Of Lime

58. Uses Of Lime

59. Uses Of Lime (b) As an industrial material: In industries lime find use as A flux in the metallurgical industry as a refractory material for lining metallurgical furnaces as a raw material for the manufacture of glass (c) An agricultural input: Lime is used to to improve productive qualities of soil and added to the poor soils to enrich their lime content Lime has also been used for soil stabilization.

60. Uses Of Lime

61. Comparative Study Of Fat Lime And Hydraulic Lime Properties Fat Lime Hydraulic Lime Colour White colour Greyish white Composition CaO with subordinate amount of clay CaO with 10-30% clay Slaking qualities Slakes vigorously Enough heat is liberated that creates hissing and cracking sounds Expands 2-3 times Slaking time 3-4 hours Slakes gently Not much heat is liberated, so no hissing sounds Expands 1-2 times Slaking time 24-48 hours Setting Setting involves absorption of carbon dioxide from atmosphere resulting in calcium carbonate. It cannot set under water as it does not have property of hydraulicity Has double setting action. CaO content may set as fat lime and clay forms hydrated aluminates and silicates of calcium similar to cement on setting. It can set under water as it has property of hydraulicity Strength Not very strong in mortar so may not be used where high strength binders are required Quite strong mortars so can be used in foundation and wall in place of Portland cement Uses White-washing, plastering , making mortars Use as a flux in industry and for soil improvement Use for making mortar in load bearing construction for underground and over-ground superstructures

62. Tests For Lime Building lime required to satisfy a number of tests before it is approved for use in construction work. 1. Chemical Composition: Lime is tested To determine ratio of different components such as CaO, MgO, SiO 2 , AlO 2 and iron oxides. The limits of component should be as per IS:712-1973 2. Fineness: To determine the fineness of grain size by sieve analysis The residue is weighed after the test and should not exceeds the specified limits.

63. Tests For Lime 3. Soundness: It is defined as The capacity of lime to resist expansion on setting It is tested with the help of Le Chatelier apparatus. Lime is mixed with sand and water and filled in mould of the apparatus. The distance between the indicator points is noted and after one hour placed in a steam boiler for three hours. After the boiling action, the distance between the indicators is noted once again. Difference between the two readings gives a measure of soundness which should be within prescribed limit.

64. Soundness of Lime

65. Tests For Lime 4. Setting Time: The time that elapses between the preparing of lime paste of standard consistency and setting of the same paste after it has been filled in a standard mould (Vicat Mould) to a minimum specified depth. Initial setting time : The time that elapses from the gauging to the penetration of the Vicat needle in the paste up to a specified depth – 35mm Final setting time : The time that elapses from the gauging to a time when Vicat needle can no more penetrate the paste (because it is already set) and makes only a mark on the surface.

66. Setting Time

67. Tests For Lime 5. Strength: Tested by preparing specimens of standard sand-lime mortar, For compressive strength – average of 12 specimens, tested on standard testing machine on specimens taken after 14 days and 28 days For transverse strength – average of 6 specimens, tested on standard transverse strength testing machine The setting time and strength tests are recommended for hydraulic limes only.

68. Tests & Specifications for Lime IS: 712:1973

69. Tests & Specifications for Lime IS: 712:1973

70. Tests & Specifications for Lime IS: 712:1973

71. Tests & Specifications for Lime IS: 712:1973

72. References Building Construction : Dr B.C. Punmia Civil Engineering Material : Prof. Singh Internet Web Sites

73. Thanks…