Mortars and Plasters

Mortars and Plasters

1. Mortars and Plasters BUILDING CONSTRUCTION MATERIALS

2. Mortars Building mortars are mixtures, used for the joining of bricks and stones. Definition: A paste obtained by adding water to a mixture of fine aggregates such as sand and binding material. The pyramids of Egypt have been built with clay-gypsum , gypsum-lime and lime mortars. The safety, strength and durability of resulting wall or any structure depends on the quality of the mortar used as a binding medium. Plaster: It is a lean mortar that has been prepared for the specific use of providing a protective covering on the inner or outer faces of construction

3. Mortars

4. The Pyramids Of Egypt Have Been Built With Clay-gypsum Mortar

5. Functions It provides binding force or cohesion between the structural units. It act as a medium for distributing the forces throughout the structure uniformly . Additional strength and resistance against rain penetration and other such weathering agencies. In stone or brick masonry, it fills up empty joints; a thin liquid mortar used for such purposes is termed as grout. It does pointing or plastering to the structure.

6. Functions

7. Qualities Or Properties Of Good Mortar The mortar mix should be easily workable – easily transported to the place of application. It should develop adequate strength in tension, compression and bond for the work for which it is used. It should be sufficiently plastic – easily placed on the bed of construction in the form of thin, smooth and uniform layer. It should be capable of retaining sufficient water during its application.

8. Qualities Or Properties Of Good Mortar

9. Qualities Or Properties Of Good Mortar It should be durable and strong in itself on drying and hardening and at the same time , it should not react in any way with the construction units. It should set and harden quickly – construction could be done with speed. It should not develop any cracks on drying and should be able to maintain their appearance for quite a long period. It should be capable of developing the designed stresses. It should be economical to make without compromising on any of the qualities.

10. Qualities Or Properties Of Good Mortar

11. Classification Of Mortars Based On Types Of Binding Material depending on the nature of the job – mortar may be made by using one or more cementing materials. Lime Mortar are mixture of fat lime or hydraulic lime, sand and water. Fat Lime – requires loss of moisture – not suitable for construction in damp and moist conditions, suitable only for thin joints in brickworks Light colour , do not cause efflorescence

12. Lime Mortar

13. Classification Of Mortars Hydraulic lime – suitable for damp situations. Cement Mortar are prepared from Portland cement or its varieties, sand and water. Surkhi Mortar : ordinary type of mortar where sand is partly or wholly replaced by surkhi (crushed burnt bricks) in lime mortar. The ratio of lime to surkhi will depend on the nature of job. It can not be used to make mortar with cement – it is reactive to some cementing materials. Commonly used in foundation works.

14. Cement Mortar

15. Surkhi Mortar

16. Based On Types Of Building Material Gypsum Mortars are prepared from gypsums or anhydride binding materials. rarely used in tough construction – application as plasters. Gauged Mortars are prepared by adding Portland cement and lime together in properly determined proportions as binding materials. Stronger, denser and durable than ordinary lime mortars. Composite Mortars : may be surkhi-motar ( surkhi , lime and water), lime- surkhi -sand mortar, cement-lime mortar and cement-clay mortar.

17. Gypsum Mortars

18. Gauged Mortars

19. Based on Nature of Application Brick Laying Or Masonry Mortar : main mortars used as binding medium between the brick masonry units in the construction of foundation and walls. Finishing Mortars Or Plasters : are lean mortars used for protective covering over walls and also in ornamental work and for architectural purpose. It should be homogeneous mix.

20. Brick Laying Or Masonry Mortar

21. Finishing Mortars Or Plasters

22. Based On Density Of Mortar Heavy Mortars : Bulk Density – greater than 1500 kg/m 3 . Aggregate - Heavy quartz or sand. Use in load bearing constructions Special type of heavy mortar – X-rays shielding mortars - Bulk Density – 2200 kg/m 3 or more. Light Weight Mortars : Bulk Density – less than 1500 kg/m 3 . Aggregate – sands poorer in quartz and also crushed lightweight rock such as pumice, blast furnace slag. Use where structure is to be kept light loaded. Special type of Light weight mortars - Bulk Density – 600 - 1000 kg/m 3 – for making sound proof ceiling and walls.

23. Based On Density Of Mortar

24. Lime Mortars Definition: homogeneous mixes of lime with various proportions of fine sand, surkhi , pumice, ash, in water. Common mortar in ordinary type of building construction work.

25. Lime Mortars

26. Lime Mortars Preparation Selection Of Raw Materials : lime, sand, surkhi , pumice, ash are common materials used in lime mortars. Lime – binding material Sand – more commonly used – may be partly or wholly replaced one or more materials. Fat Lime : used in dry type of construction. Hydraulic Lime: used in water rich areas and damp conditions.

27. Selection Of Raw Materials Sand: Good quality for making strong and durable mortar – pure in composition and free from impurities and sharp grained in structure. Purpose To Add Sand In Mortar: To bear the load – sand + lime (cement) = stone like mass. To resist shrinkage and cracking. To increase bulk of the mortar.

28. Purpose To Add Sand In Mortar

29. Selection Of Raw Materials Pozzolana Materials : natural or artificial materials that exhibits some binding properties when used with cement or lime. – pumice, cinder, surkhi and ash. Surkhi – finely grinding well-burnt bricks. Cinder – fine residue from the burning of coals in railway engines. Suitable for making lightweight mortars. Pumice – natural highly porous volcanic rock formed by accumulation and compaction of ash from volcanoes. Suitable for making lightweight mortars. Water : which is suitable for drinking purpose. Water should be free from alkalies , acids and organic residues.

30. Proportioning Of The Raw Materials Aim: to fix such ratios of the ingredients that gives a mortar of desired qualities (strength, durability, finish and cost). Mortar used in different places in a construction are subjected to different forces – no general rule for proportioning a mortar mix can be framed. Additional facts should also be remember while selecting ratio. If more sand is added than recommended – short in workability, difficult to place. If less sand is added than recommended – very stiff and will stick – show considerable shrinkage on drying. When In doubt – add a little more (not less) The amount of water - carefully fixed after trials – neither too lean and nor too stiff.

31. C. Mixing Of Raw Materials Mannual Mixing : common method for ordinary construction. Done either on a watertight platform made of masonry or in tank of suitable dimensions dug in the ground. First place measure volume of lime on platform and mix it properly. Water is added in small quantities a time. Mixing is continued till a mortar of uniform consistency is obtained. Mortar Mill Mixing : mechanical device for grinding the mortar ingredients in the presence of water. Either run by an animal (lime chakki ) or by motor power (grinding mill).

32. Mannual Mixing

33. Mortar Mill Mixing

34. Properties Of Lime Mortars Quite plastic and workable when wet Good working qualities if made from high calcium limes Develop strength very slowly but gain continuous strength over long periods Do not set but stiffen as water is lost by absorption by units or blocks in contact and by evaporation. Provide a fairly strong surface when used for plastering Provide enough bond when used for masonry joints

35. Uses Of Lime Mortars For Foundation Works: fat lime mortar can be used in all types of foundation work in dry sub grade – water table is 2.4 m below the foundations level. For All Masonry Works: loading – 20 to 60 tonnes /m 2 (light and medium loading) Fat lime and hydraulic lime, both are suitable. Lime mortar can be replaced by cement mortar. To bind stones, bricks or concrete blocks together Lime mortar can not be applied when: Sub grade soil is moist – water table is within 2.4 m. Heavy loading is expected. Construction is massive and very thick.

36. Uses Of Lime Mortars

37. Hardening Of Lime Mortars  

38. Precautions Mortars with hydraulic lime – should be used within 4 hours after mixing. Lime mortars with surkhi – should be used within 24 hours after mixing. Composite (lime and cement) mortars – should be used within 2 hours after mixing. All lime mortar shall be kept wet after grinding. The workers who are to handle lime mortar should protect their skin by using oil rubber gloves etc.

39. Cement Mortars Cement mortar is homogeneous paste of fixed proportion of cement, sand and water. Strongest type of mortar so preferred for use in construction of structure subjected to heavy loading

40. Cement Mortars Preparation: Selection Of Raw Materials : the Portland cement must be pure, undamaged. Ordinary Portland cement is most suitable. Sand: Good quality for making strong and durable mortar – pure in composition and free from impurities and sharp grained in structure. Must be thoroughly clean before using. No other aggregate can replace sand completely in cement mortars.

41. Cement Mortars B. Proportioning Of The Raw Materials . For ordinary masonry work – 1 cement: 3 sand to 1 cement: 6 sand For reinforced brick work & work in moist condition - 1 cement: 2 sand to 1 cement: 3 sand For Architectural work – 1 cement: 3 sand For load bearing structures - 1 cement: 2 sand to 1 cement: 3 sand For plaster work, it provides a water proof layer and protects the element from weathering effects

42. Cement Mortars C. Mixing Of Raw Materials . ( i ) Hand Mixing : For small quantity of mortar First clean dry sand is spread on a pucca platform and cement of required quantity is spread over it. Whole mass is mixed dry by spades and required quantity of water is added. This mix can be used before the initial setting time of cement (ii) Machine Mixing: For large quantity of mortar required continuously at a fast rate Cement and sand in specified proportion are put into the drum of the mixer and required quantity of water is added. Drum is revolved for a sufficient period to form uniform mixture of required consistency.

43. Cement Mortars

44. Precautions The setting process starts even within the first hour of its preparation - should be used within 30 minutes after adding water to the cement and sand mixture. The Structural Units – bricks and stones must be soaked in water before laying on the wall . If dry units, it will absorb moisture quickly. If Cement Sand Mortar – place should be kept wet at least for seven days.

45. Uses Of Cement Mortars Use where high strength is required and in structures which are subjected to wet condition such as piers, dams, deep foundation etc. Use for external plastering and pointing work Use for damp proof course below ground level Use in exposed work such as exterior walls and parapets, engineering construction with bricks of high strength Use in concrete as cement mortar binds the particles of coarse aggregate into one solid mass

46. Uses Of Cement Mortars

47. Gauged Mortars Cementing material – cement and lime both Lime – for economical purpose and cement – for strength. Methods For Making Gauged Mortars The three ingredients: lime, cement and sand are mixed together in dry condition in predetermined volume (1 cement, 1 lime,1 sand or 1 cement, 2 lime, 6 sand etc) Then add small quantity of water, increase the quantity of water gradually – mixing is continued till homogeneous paste of desired consistency is obtained. Lime Sand Mortar: predetermined volume of cement is added in dry state then mix thoroughly. Add small quantity of additional water. Cement Sand Mortar : same as lime sand mortar but use slacked lime in finely powered form.

48. Plasters Lean mortars used mostly for covering masonry surfaces. Lean mixes of cementing materials with fillers such as sand, surkhi and crushed stones. Jaggery , white of eggs and soured curd are also added for special effects Protective Plasters – saves the brick or stone from direct and destructive attacks of atmosphere and also from wind, rain and harmful industrial gases, used on the exterior walls Decorative Plasters – appealing shades and finish designs to the construction, used on the interior walls

49. Plasters

50. Objects of Plastering To provide a true, even, smooth and finished surface to the work and improve the appearance. To protect the surface from atmospheric influences To cover defective workmanship To provide a covering for the unsound and porous materials

51. Types Of Plasters Lime plaster, cement plaster, gypsum plaster etc. Lime Plasters: mixing thoroughly slaked lime and sand in ratio of 1 lime and 2-3 sand surkhi by volume with good quantity of water till homogeneous lean paste is obtained. Specially useful as protective plasters on the inner side of the walls. Moghul plaster – 1 lime : 3 sand : 1 surkhi to which some Jaggery , white of eggs have been also mixed. These later materials improve the adhesive property, strength and beauty of plaster. Lime should be thoroughly slaked and free from unburnt lime, grit and pebbles.

52. Lime Plasters

53. Types Of Plasters Cement Plaster: lean mix of Portland cement and sand with water. Suitable for all type of plastering works. Proportion for all purpose – 1 cement : 3 sand Apply in single coat. The surface of the plaster is kept wet for at least 3 days after application by sprinkling water on it at regular intervals.

54. Cement Plaster

55. Types Of Plasters Common ratio are: 1 cement: 1 lime: 6 sand for external plasters, below damp proof course 1 cement: 2 lime: 9 sand for external plasters on walls Guniting Plaster: 1 cement: 3 sand which is applied under great pressure – 2.5 kg/cm 2 with the use of special gun. From gun, thoroughly mixed plaster is thrown out on the surface of application with the help of compressed air. Gypsum Plaster : binding material – gypsum. Used for making architectural fancies and decorative designs on walls and roofs. Properties Of Gypsum Plaster: Great resistance to fire Set and harden quickly Undergo very little expansion or contraction

56. Guniting Plaster

57. Gypsum Plaster

58. Sand Rock particles that ranges in grain size between 2 mm and 1/16 mm. In composition, an oxide of silica (SiO 2 ) . Mostly broken grains of mineral quartz (SiO 2 ) produced as result of breakdown of granites, sandstone and similar rocks by natural process of weathering and erosion.

59. Sand

60. Sand Classification: According to mode of origin: Pit sand, stream sand and marine sand. Pit Sand: generally sharp and angular – deposited by wind and form accumulations in soil. Sand when cleaned and washed makes good mortar. River Sand: occur as accumulations of great extent along the base and banks of rivers shape – almost round. Generally free from clay, salt and organic impurities. Most commonly used for making mortars, plasters and concrete.

61. Classification of Sand

62. Sand Marine Sand: occur on beaches and along sea shore. Shape – rounded grains of quartz Covered with the salts which are not easily separable. If used in mortar, concrete – salts react with the binding material. Marine sands are considered of inferior quality and should be better avoided. If it is only source available – must be used after thoroughly washed. According to composition: clean sand, silty sand and clayey sand.

63. Marine Sand

64. Sand Clean Sand: well graded-mostly quartz particles in wide range of grain size. Clean sand must be used for making mortar plaster and concrete. Silty Sand: poorly graded – considerable proportion of silt (1/16 to 1/256 mm size) and other non-plastic fines. Clayey Sand: poorly graded – prominent clay fraction (below 1/256 mm size) and also plastic fines. Sand is also obtained artificially by crushing natural quartzite rock to the required grain size. According to grain size: course sand – 2-1 mm, medium sand – 1-0.25 mm and fine sand – 0.25 – 0.15 mm.

65. Sand

66. Bulking Of Sand Volume of sand will be more when water is present in it even in small quantities. Volume of moist sand is more than dry sand. Bulking of sand: the change or increase in volume of sands on getting moist. Important in construction. All the mix design denotes the proportion of sand in essentially dry state. Factors affecting on rate of bulking: Percentage of moisture content – bulking effect is maximum when moisture content in sand is between 4 to 6 %. As water-content percentage increasing – this effect goes on decreasing. Grain size of sand particles – fine sand shows higher bulking rate as compared to coarse sand.

67. Bulking Of Sand

68. Bulking Of Sand

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

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