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Concrete Technology Unit I

  1. 1. Concrete Technology Module-I
  2. 2. Syllabus • Ingredients of Concrete • Cement- Chemical composition, hydration, heat of hydration, hydrated structure, various types of cement, testing of cement as per Indian standard. • Aggregates-Function in concrete, classification, effect of geometry • texture, strength, mechanical properties, moisture content, water absorption, bulking of sand, deleterious substances, sieve analysis various grading and grading requirements, sampling & testing as per Indian Standards. • Water- General Requirements & limiting values of impurities. • Admixtures- Additives and admixtures, types, need and benefits • Mineral admixture - Fly ash, silica fume, blast furnace slag, and other pozzolanic materials. • Chemical admixtures - Accelerator, retarder, water reducing, elements, plasticizer and super-plasticizer, their functions and dosage.
  3. 3. Concrete • Concrete= Cement + Sand+ Aggregate+ Water+ Admixture+ Air • The mixture of Cement and water is paste. The function of paste is to bind sand and aggregate particles by chemical process of hydration. It also fills the voids between sand and aggregate particles. • The strength of concrete depends upon the property of cement, sand, aggregate, etc.
  4. 4. Concrete
  5. 5. Composition of Concrete • Concrete is composed of, • Concrete= Cement + Sand + aggregate+ water+ admixtures + air • Cement: The funtion of cement is to bind the aggregates. It also fills the void between sand and aggregate. • Aggregate: • The aggregate occupy about 75 % of the volume and hence their influence on various properties of concrete is considerable. Aggregates are generally cheaper than cement and impart greater volume, stability, and durability to concrete. The aggregate generally provides bulk to the concrete.
  6. 6. Composition of Concrete • Water: Water is required for carrying out chemical reactions in cement. If the water content is less the heat of hydration is not possible, hence the strength of concrete will be reduced. If water content is in excess water will cause undesirable capillary cavities and concrete becomes porous. • Admixtures: Admixtures is defined as a material other than the basic ingredient of concrete mixed immediately before or during mixing to modify some properties of concrete in the fresh or hardened state. • The use of admixtures like accelerators, retarders, air- entraining agents, pozzolanic material, water proofing admixtures etc.
  7. 7. Cement
  8. 8. Aggregate
  9. 9. Composition of Concrete • The properties commonly modified using admixtures are setting time, workability, air entrainment, dispersion etc. The admixtures are generally added in small quantity from 0.005 to 2 % by cement weight. Overuse of admixtures have detrimental effect on the properties of concrete. • Air: The voids in the mass of concrete can be classified into two groups • Entrapped air • Entrained air
  10. 10. Composition of Concrete • Entrapped air: The entrapped air is the void present in the concrete due to insufficient compaction • Entrained air: The entrained air is the intentionally incorporated minute spherical bubbles
  11. 11. Entraped Air
  12. 12. Entrained Air Concrete
  13. 13. Admixtures
  14. 14. Admixtures
  15. 15. Ingredients of Concrete
  16. 16. Manufacturing Process of Portland Cement Raw material for cement Calcareous Materials e.g. limestone Chalk marl Argillaceous materials e.g. Clay Shale Calcareous: Composed of or containing calcium or calcium carbonate. Argillaceous minerals: are minerals containing substantial amounts of clay-like components . Argillaceous components are aluminosilicates, and more particularly clay minerals such as kaolinite, montmorillonite-smectite, illite, and chlorite. Claystone and shales are thus predominantly argillaceous.
  17. 17. Manufacturing Process of Portland Cement Calcareous Materials e.g. limestone Chalk marl Argillaceous materials e.g. Clay Shale
  18. 18. Processes of Manufacturing • Wet Process • Dry Process • Semi-Dry Process
  19. 19. Wet Process
  20. 20. Dry Process
  21. 21. Semi-Dry Process
  22. 22. Processes of Manufacturing • Following are three distinct operations are involved in the manufacture of cement. • (i) Mixing of raw material • (ii) Burning • (iii) Grinding • In the wet process, raw materials are mixed wet in required proportions and slurry is formed. While in the dry process raw materials are mixed in required proportions in dry form and dry raw mix is formed. The remaining two operations, namely, Burning, and Grinding are the same for both the processes. • The correct slurry is fed into a rotary kiln from upper end. As the slurry gradually descends, there is rise in temperature and small lumps, known as nodules are formed.
  23. 23. Processes of Manufacturing • These nodules, reach to the burning zone, where the temperature is about 1500 0C to 1700 0C. In the burning zone, calcinated product is formed and nodules are converted into small hard balls, known as clinkers. • The size of clinkers varies from 3 mm to 20 mm. • Clicker obtained from rotary kiln are finely ground in ball mills and tube mills. A small quantity about 2 to 3 % of gypsum is added to prevent flash-setting of the cement. • The final ground cement is stored in silos. It is then weighted and packed in bags by automatic machine. • Each bag of cement contains 50 kg of about 0.035 m3 of cement.
  24. 24. Oxide Composition of Cement • The raw material used for the manufacturing of Ordinary Portland cement contains mainly lime, silica, alumina, and iron oxide. These oxides interact with one another in the kiln at high temperature to form more complex compounds. The relative proportions of these oxide compounds are responsible for various physical properties of cement. Rate of cooling and fineness of grinding also affect the property of cement.
  25. 25. Oxide Composition of Cement Oxide Content% Lime, CaO 60- 67 % Silica, SiO2 17-25% Alumina, Al2O3 3- 8 % Iron Oxide, Fe2O3 0.5-6 % Magnesia, MgO 0.5- 4 % Alkalies, K2O, Na2O 0.3-1.2 % Sulphates, SO3 1.0 – 3.0 %
  26. 26. Oxide Composition of Cement • IS 269-1989 Specifies the following chemical requirement for 33 grade Cement:
  27. 27. Oxide Composition of Cement • In Terms of Oxide Composition, a high lime content generally increases the setting time and results in higher strengths. A decrease in lime content reduces the strength of concrete. • A high Silica content prolongs the setting time and gives more strength. • The presence of excess unburnt lime is harmful since it results in delayed hydration causing expansion and deterioration of concrete. • Iron Oxide is not a very active constituent of cement, and generally acts as a catalyst and helps the burning process. Owing to the prescence of iron oxide the cement derives the characteristics grey colour. • Magnesia, if present in large quantities, (more than 5 %) causes unsoundness, • Alkali oxide (K2O, Na2O) if present in quantity more than 1%, leads to alkali aggregate reaction, efflorescence and staining
  28. 28. Bogue’s Compounds • As stated earlier the oxides present in the raw materials interact with one another in the kiln at high temperature to form more complex compounds. The identification of the major compound is largely based on the work of R.H.Bogue. And other and so it is often referred as ‘ Bogue’s Compounds’ or Bogue’s Composition’.
  29. 29. Bogue’s Compounds Name of Compound Formula Abbreviation Tricalcium silicate 3 CaOSiO2 C3S Dicalcium Silicate 2CaOSiO2 C2S Tricalcium aluminate 3CaOAl2O3 C3A Tetracalcium aluminoferrite 4CaO.Al2O3.Fe2O3 C4AF Bogue’s Compound Percentage by mass in cement C3S 30-50 C2S 20-45 C3A 08-12 C4AF 06-10
  30. 30. Bogue’s Compounds • In addition to four major compound there exists minor compounds, such as MgO, TiO2, Mn2O3, K2O, Na2O. • Two of the minor compounds of interest are K2O, Na2O, known as alkalies. They have been found to react with some aggregates, the product of this reaction causing disintegration of concrete, and also have been found to affect strength of cement.
  31. 31. Bogue’s Compounds • With The advancement of science and technology. It has become possible to recognise and understand the micro structure of the cement compound before hydration and after hydration. The X-ray florescence method, the X-ray powder diffraction method and use of powerful electron microscope has helped to reveal the crystalline or amorphous structure of the hydrated or unhydrated cement. • Thornbohm and Lechatelier, also observed four different kind of crystal in thin sections of cement clinkers. Thornbohm called these four kind of crystals as alite, belite, Celite and Felite. Thornbohm’s description of the minerals in cement was found to be similar to Bogue’s compound. Hence, Bough’s Compounds C3S, C2S, C3A, C4AF are sometimes called in literature as Alite, Belite, Celite, and Felite.
  32. 32. Properties of Bogue’s Compounds • The properties of Bouge’s are as under: • C3S: • It is responsible for early strength • First 7 days strength is due to C3S • It Produces more heat of Hydration • A cement with more C3S content is better for cold weather concreteing. • C2S: • The hydration of C2S starts after 7 days. Hence, it gives strength after 7 days. • C2S hydrates and hardens slowly and provides much of the ultimate strength. • It is responsible for the later strength of concrete. • It produces less heat of hydration.
  33. 33. Properties of Bogue’s Compounds • C3A: • The reaction of C3A with water is very fast and may lead to an immediate stiffening of paste, and this process is termed as flash set. • To prevent this flash set, 2 to 3 % gypsum is added at the time of grinding the cement clinkers. • The hydrate C3A do not contribute to the strength of concrete. • C4AF: • C4AF hydrates rapidly. • It does not contribute to the strength of concrete. • The hydrates of C4AF show a comparatively higher resistance to sulphate attack than the hydrates of C3A
  34. 34. Hydration of Cement • When water is added to cement, ingredients of cement react chemically with water and form various complicated chemical compounds. The chemical reaction that takes place between cement and water is reffered as hydration of cement. • Anhydrous cement does not bind fine and course aggregates. It requires adhesive property only when mixed with water. • The silicates (C3S, C2S) and aluminates (C3A) aluminates of cement react with water and form hydro silicates and hydro aluminates. These products are thick and sticky. It is called gel. Gel posses adhesive property and binds aggregate and sand together. It also fill voids between sand and aggregate.
  35. 35. Hydration of Cement • The hydration process is not an instantaneous one. The reaction is faster in the early stage and continious indefinately at a decreasing rate. Complete hydration cannot be obtained under a period of one year or more unless the cement is very finely ground.
  36. 36. Hydration of Cement
  37. 37. Hydration of Cement
  38. 38. Water Requirement for Hydration • Amount of water required for chemical reactions with Portland Cement Compound is given below: Major Compound % Water by Weight of Cement C3S 24 C2A 21 C3A 40 C4AF 37
  39. 39. Water Requirement for Hydration • It has been estimated that for C3S and C2S compounds, on an average 23 % of water by weight of cement is required for chemical reaction. Thus 23 % of water chemically combines with cement and, therefore it is called bound water. A Certain Quantity of water is inadequate to fill up the gel pores, the formation of gel itself will stop and gel pores will not form. Gel water of about 15 % by weight of cement is required. Therefore, a total 23 + 15= 38 % of water by weight of cement is required for complete hydration. If less than 38 % of water is used than complete hydration is not possible as the volume available is insufficient to accommodate all the product of hydration. Hence, Strength of Concrete will be reduced. • If more than 38 % of water is used, then the excess of water will cause undesirable capillary cavities and concrete becomes porous.
  40. 40. Heat of Hydration • The Reaction of Cement with water is exothermic. The reaction liberates a considerable quantity of heat. • The Quantity of heat (joules)/ gram of unhydrated cement, evolved upon complete hydration at a given temperature is defined as Heat of Hydration. • The Temperature at which hydration occurs significantly affects the rate of heat evolution, which is of more importance than the total heat of hydration. In ordinary Portland cement about 50 % of total heat is liberated between 1 to 3 days, about 75 % in 7 days and about 90 % in six months.
  41. 41. Heat of Hydration of Major Compounds
  42. 42. Setting and Hardening of Cement Setting of Cement Hardening of Cement Setting is the term used to describe the stiffening of the cement Paste Hardening refers to the gain of strength of a set of cement paste It refers to a change from a fluid to a rigid state It refers to formation of solid mass possessing good compressive strength. The setting of Cement Starts after 30 minutes from the instant when water is added to cement and compacted within 10 hours The process of hardening of cement continues for a period more than 1 year. To know the setting of cement, initial setting time test and final setting time test are conducted To know the hardening of cement, compressive strength test is conducted.
  43. 43. False Set • A phenomenon of abnormal premature stiffening (hardening) of cement within a few minutes of mixing with water, is termed as false set. It defers from flash set in that no appreciable heat is evolved, and remixing the cement paste without addition of water restores plasticity of the paste until it sets in the normal manner and without a loss of strength. • Some of the cause of false set are to be found in the dehydration of gypsum when interground with too hot a clinker. • False set can be due to the activation of C3S by aeration at moderately high humadities. Water is adsorbed on the grains of cement and these freshly activated surface can be combined very rapidly with more water during mixing; this rapid hydration would produce false set. • Another cause of false set may be associated with the alkalis in the cement. During storage they may carbonate, and alkali carbonate react with Ca(OH)2 liberated by the hydrolysis of C3S to form CaCO3. This precipates and induce a rigidity of the paste.
  44. 44. Types of Cements • Ordinary Portland Cement (OPC) • Rapid Hardening Cement (RHC) • Extra-rapid Hardening Cement • Quick Setting Cement • Low Heat Cement • Sulphate Resisting Cement • Super Sulphated Cement • Portland Pozolana cement • Portland slag cement • Colored cement
  45. 45. Types of Cements • Hydrophobic Cement • Air Entraining Cement • Masonry Cement • Oil Well Cement • Expansive Cement • High Alumina Cement • Concrete Sleeper Grade Cement • Waterproof Cement • Rediset Cement • Very High Strength Cement
  46. 46. Types of Cements • Ordinary Portland Cement (OPC): • This is by far the most common cement in use: about 70 % of all cement used in India is of the ordinary type. • Prior to 1987, there was only one grade of OPC governed by IS 269: 1976 After 1987 higher grade of cement. The OPC was classified into 3 grades as 33 grade, 43 grade, 53 grade. In modern construction activities, higher grade cement have become so popular that 33 grade of cement is almost out of the market. • Although OPC are little costlier then low grade cement; they offer many benefits like 10 – 20 % saving in cement consumption, faster rate of development of strength and higher strength. • OPC are generally recommended when there is no exposure to sulphates in the soil or in ground water.
  47. 47. Ordinary Portland Cement (OPC)
  48. 48. Types of Cements • Rapid Hardening Cement (RHC) (IS 8041: 1990) • As the name implies, it develops strength rapidly and therefore can be called as high early strength cement. The rate of setting is same as that of ordinary Portland cement. • The strength of RHC at the age of 3 days is equal to the 7 days strength of OPC with the same w/c ratio. The increased rate of gain of strength of RHC is achieved by a higher C3S Content and by finer grinding of clinker. • The rapid gain of strength is accomplished by a high rate of heat development and hence it should not be used in mass concrete constructions like concrete gravity dam, concrete retaining walls. • The Use of RHC is recommended in the following situations • In pre-fabricated concrete construction • For Road repair works • Where form-work is required to be removed early for re-use elsewhere. • In Cold weather concreting • Wall Sealing
  49. 49. Rapid Hardening Cement (RHC)
  50. 50. Types of Cements • Extra Rapid Hardening Cement: • This cement is obtained by intergrading calcium chloride with RHC. The quantity of calcium chloride should not exceed 2 %. It is necessary that the concrete made by using extra rapid hardening cement should be transported, placed, compacted, and finished within 20 min. The cement must be stored under dry conditions and should generally be used within one month of dispatch from the factory. • This type of cement is suitable for cold weather concreting. It is suitable where a very high early strength is required.
  51. 51. Extra Rapid Hardening Cement
  52. 52. Types of Cements • Quick Setting Cement: • This cement sets very early but does not gain strength early. The early setting property is brought out by reducing the gypsum content at the time clinker grinding. Sometimes aluminum sulphate is added to accelerate the setting process. It contains higher percentage of C3A. It is required to be mixed, placed and compacted very early. • The use of quick setting cement is recommended under the following conditions: • Under Water Construction • Grouting operations.
  53. 53. Quick Setting Cement
  54. 54. Types of Cements • Low Heat Cement: • The reaction of cement with water is exothermic and produces a considerable quantity of heat. The rise in temperature in the interior of a large concrete mass due to the heat of hydration. Can lead to serious cracks. • A low heat evolution is achieved by reducing the content of C2S and C3A which are the compound evolving the maximum heat of hydration and increasing C2S. For low heat cement the rate of gain of strength is slow but the ultimate strength is the same as that of ordinary Portland cement. • The use of low-heat cement is recommended in the following situations: • Mass Concrete Construction • Where it is necessary to produce resistance to sulphate attack. • Hot weather concreting.
  55. 55. Low Heat Cement
  56. 56. Types of Cements • Sulphate Resisting Cement (IS 12330:1988) • Ordinary Portland Cement is susceptible to the attack of sulphates, in particular to the action of magnesium sulphate. Sulphates react both with the free calcium hydroxide in set cement to form calcium sulphate and with hydrate of calcium aluminate to form calcium sulphoaluminate, the volume of which is about 227% of the volume of the original aluminates. Their expansion within the framework of hardened cement paste results in cracks and subsequent disruption. This phenomenon is known as sulphate attack.
  57. 57. Sulphate Resisting Cement
  58. 58. Types of Cements • Sulphate resisting cement is very similar to OPC except the quantity of C3A which is the least stable compound is strictly limited to about 5 %. The low C3Acontent and comparatively low C4A content in sulphate resisting cement give it a high strength but the early strength is low. The heat of hydration is not much higher than that of low heat cement. • The use of Sulphate resisting cement is recommended under the following conditions • Concrete to be used in marine conditions • Concrete to be used in the construction of sewer treatment plant. • Concrete used for fabrication and basement where soil is infested with sulphates. • Concrete to be used in the construction of chemical industry.
  59. 59. Types of Cements • Super Sulphated Cement: • This cement is manufactured from well-granulated slag and hard burnt gypsum together with 1 to 2 % of Portland cement the mixture is ground finer than that of Portland cement. Its setting action is different from the other cements and admixtures should not be used with it. If used with R.C.C work a minimum cover of 35 mm is necessary. It should not be mixed with either ordinary Portland cement or high alumina cement since the action will be different. It is highly resistant to chemical attack. It cured in air, the surface gets softened by atmospheric CO 2. Hence, minimum 3 days of water curing is preferable. • The use of super sulphated cement is recommended under the following conditions: • In foundations, where chemically aggressive condition exists. • In marine works. • RCC pipes likely to be used in sulphate bearing soils. • Mass Concreting.
  60. 60. Types of Cements • Portland Pozzolana Cement (IS 1489:1991): • Portland Pozzolana Cement is manufactured by intergrading of OPC clinker with 15 to 35 of pozzolanic material. The pozzolanic materials used for manufacturing of Portland Pozzolana Cement (PPC) are fly ash and claimed clay. The pozzolanic material are essentially a siliceous or aluminous material which itself possessing no cementations properties, which will. In finely divide form and in the presence of water, react with calcium hydroxide, liberated in the hydration process, to form compounds possessing cementations properties.
  61. 61. Portland Pozzolana Cement
  62. 62. Portland Pozzolana Cement (IS 1489:1991) • The hydration of C3S and C2S produce considerable quantity of Calcium hydroxide [Ca(OH)2], which is by are large and useless material from the point of view of strength or durability. if such useless mass could be converted into a useful cementations product, it considerably improves quality of cement. • Ca(OH)2 + fly ash or claimed clay + water C-S-H (Gel) • It is important to note that the addition of pozzolana does not contribute to the strength at early ages, but gives later strength similar to OPC. However, in India there is an apprehension in the minds of the users to use the PPC for structural works. If PPC is manufactured by using right type of reactive pozzolana, it will not in any way inferior to OPC
  63. 63. Types of Cements • Advantages of PPC: • It is economical, as costly clinker is replaced by cheaper pozzolanic material. • Pozzolanic material converts soluble Ca(OH)2 into insoluble cementations products. Hence, durability and permeability of concrete are improved. • It generates low heat of hydration. • As the flyash is finer and of lower density, the bulk volume of 50 kg bag is slightly more than OPC therefore OPC gives more volume of mortar than OPC. • Uses of PPC: • For Hydraulic Structures • For marine structures • For mass concrete structures like dam, bridge piers, and raft foundation. • For sewer and sewage disposal works etc.
  64. 64. Types of Cements • Portland Slag Cement: (IS 455:1989) • This type of cement is made by intergrading Portland Cement Clinker, Gypsum and granulated blast furnace slag. The quantity of blast furnace slag mixed with Portland clinker will range from 25 to 65 %. Blast furnace slag is a waste produce consisting of a mixture of lime, silica, alumina obtained in the manufacturing of pig iron. The slag can also be used together with limestone as a raw material for the conventional manufacture of Portland Cement resulting in clinker which when grouped gives Portland Slag Cement. • The Portland Slag Cement (PSC) has low heat of hydration and better resistance to chlorides, sulphates or alkalis and acidic water. Therefore it can be used in marine works.
  65. 65. Portland Slag Cement
  66. 66. Types of Cements • Advantages of PSC: • Low Heat of Hydration • Better resistance to Chloride, Sulphate, Alkalis. • Low permeability • Good resistance to acidic waters. • Refinement of pore structure. • Uses of PCS: • For mass concreting works • For marine work.
  67. 67. Types of Cements • Colored Cement (White Cement) IS 8042: 1989 • The Grayish color of Portland is due to the presence of Iron Oxide. The Process of manufacturing of white cement is the same as that of Portland cement but the amount of iron oxide is limited to less than 1 %. The kind of limestone required for manufacturing white cement is only available near Jodhpur in rajastan. The raw material used are high purity lime stone (96 % CaCO3 and less than 0.07 % iron oxide) • For manufacturing of various colored cements either Grey Portland Cement or White Cement is used as a Base. With the use of Grey cement only red or brown cement can be produced. Colored cement consists of Portland Cement with 5 -10 % of pigment. For proper mixing of pigment, it is usual to grind pigment and cement clinkers together. • The following are the use of White/ Colored Cement: • To fill joints of Glazed tiles in W.C. Bathrooms, kitchens etc. • To fill joints in flooring.
  68. 68. Colored Cement (White Cement)
  69. 69. Types of Cements • Hydrophobic Cement (IS 8043:1991): • Hydrophobic Cement is obtained by adding water repellant file forming substances such as oleic acid, stearic acid and boric acid to OPC clinkers at the time of grinding. The water-repellant film formed around each grain of cement, prevents the entry of atmosphere moisture and reduces the rate of deterioration of the cement during long storage, transport or under unfavorable conditions. The film is broken out when the cement and aggregate are mixed together at the mixer exposing the cement particles for normal hydration. • The film forming water-repellant substance will entrain certain amount of air in the body of concrete which will improve the workability of concrete.
  70. 70. Types of Cements • Air entraining cement is made by mixing a small amount of an air- entraining agent with OPC clinkers at the time of grinding. The main air-entraining agent used are: • Alkali salts of wood resins. • Calcium salts of glues and other proteins. • Animal and vegetable fats, oils etc. • Bleaching Powder. • Hydrogen Peroxide, Aluminum Powder.. • The air entraining agents may be used in powder or in liquid forms to the extent of 0.025 – 1.0 percent. Air-entraining agents will produce at the time of mixing, tiny discrete non-coalesceing air bubbles in the mass of concrete which will modify the properties of plastic concrete with respect to workability, segregation and bleeding. It will modify the properties of hardened concrete with respect to resistance in frost action and reduction in density. • This Cement is used to produce light weight Concrete.
  71. 71. Hydrophobic Cement
  72. 72. Types of Cements • Masonry Cement: (IS 3466: 1988): • Ordinary Cement, when used in masonry, gives a harsh mortar and because of the sucking of water by masonry, often results in poor bond. To avoid this, masonry cement is now used which is made of Portland Cement Clinkers, limestone, gypsum and air-entraining agent. • The masonry cement should be workable, adhere to the surface help the grinding and the plasticity, workability and the water retentive property. It reduces shrinkage too.
  73. 73. Types of Cements • Oil Well Cement( IS 8229: 1986): • In drilling of oil wells, cement is used to seal off the annular space between steel casing and rock strata and also to seal off any other fissures or cavities in the rock strata. • The desired properties of oil well cement can be obtained in two ways, by adjusting the compound composition of cement (to have very little C3A) and by adding retarders to ordinary Portland cement. Retarders prevent quick setting and retains the slurry in mobile condition to facilitate penetration to all fissures and cavities.
  74. 74. Oil Well Cement
  75. 75. Types of Cements • Expansive Cement: • Concrete shrinks while getting due to loss of free water. This is known as drying shrinkage. The important property of expansive cement is that it suffers no overall change in volume on drying. Such type of cement is made by using an expanding agent and stabilizers very carefully, Generally about 8-20 parts of the sulphoaluminate clinkers are mixed with 100 parts of the Portland cement and 15 parts of the stabilizer • Uses of expansive Cement are: • Grouting anchor bolts. • Grouting machine foundation. • Grouting prestress concrete ducts.
  76. 76. Types of Cements • High Alumina Cement (IS 6452:1989): • High alumina cement is obtained by fusing or sintering of limestone and bauxite. It is also known as aluminious cement or aluminate cement. It has good resistance to attack of gypsum bearing water and chemical attack. This cement is very different in its composition and also in some properties from Portland cements so that its structural use is severally limited but the concreting techniques are similar.
  77. 77. High Alumina Cement
  78. 78. Types of Cements • Concrete Sleeper Grade Cement (IRS-T 40: 1985): • This Cement is a special high strength cement manufactured as per specification laid down by the ministry of Indian Railway under IRS –T 40:1985. The use of this cement is restricted to the production of railway sleepers. It is very fine ground cement with high C3S content. No accelerating agent are added. This cement can be used for prestress concrete.
  79. 79. Types of Cements • Waterproof Cement: • This cement is manufactured by adding waterproofing compounds like calcium separate, aluminum separate and gypsum treated with tannic acid to ordinary Portland Cement at the time of clinker grinding. • It is used for waterproofing of terrace, water tanks, W.C. bathrooms etc.
  80. 80. Waterproof Cement
  81. 81. Types of Cements • Rediset Cement: • Associated Cement Company (ACC) of India have developed a cement, which could yield high strengths in a matter of hours, without showing any retrogression of strength. It is known as rediset Cement. • Importance properties of Rediset Cement: • Its Initial Setting time is about 8 to 10 minutes • It liberates more heat of hydration • The sulphate resistance is very poor. • Application of Rediset Cement: • Repairs of Concrete roads and pavements • Quick removal of forms in precast concrete product industry • Slip formed Concrete construction • Paslletisation of iron ore dust.
  82. 82. Rediset Cement
  83. 83. Types of Cements • Very High Strength Cement: • Very High Strength cement is required for special application like repairs of air fields runways. Launching pads, expressway pavement repair etc. This cement can be manufactured by different ways under different names as follows: • High early Strength Cement: This can be achieved by using lithium salts as accelerators. It gives very high strength with a marginal reduction in later strength. • Magnesium Phosphate Cement (MPC): This cement can be used for rapid repair of damaged concrete roads and airfield pavements. • Pyrament cement: Some Cement Companies in USA have developed very high strength cement under a trade name pyrament cement. It is a blended Hydraulic Product. No Chlorides are added. • The Associated Cement company in collaboration with R & D engineers, Dighi, Pune have developed similar very high strength for repair of air field pavements
  84. 84. Field Testing of Cement The following field tests are necessary to perform, to ascertain the quality of cement at site. • Open the bag and take a good look at the cement. There should be no visible lumps. • The colour of the cement should be greenish grey • When hand is inserted in cement bag it should feel cool. • Take a pinch of cement and feel between fingers. It should give a smooth feeling and not a gritty feeling. • Take a handful of cement and throw it on a bucketful of water, the particles should float on water for some time before they sink. • Take about 100 gms of cement, add some water and prepare a stiff paste. From stiff paste, pat a cake with sharp edges. Put it on a glass plate and slowly take it under water in a bucket. The shape of the cake should not be disturbed, while taking it down to the bottom of the bucket. After 24 hours the cake should retain its original shape and at the same time it should also set and gain some strength.
  85. 85. Field Testing of Cement
  86. 86. Storage of Cement The following points should be observed while storing Cement. • Bagged Cement should be stored in waterproof shed with non porous walls and floors. • The plinth level should be well above ground level. • Number of opening like doors, windows and ventilator should be minimum and kept tightly shut. • Drainage should be provided if necessary to prevent accumulation of water in the vicinity of the shed. • Cement should be kept 30 cm away from walls. • To reduce air circulations no gap is desirable between rows of cement bags. • In moist area cement bags should be placed on wooden planks kept above floor. • Old bags should be used first for beams and slabs casting use fresh bags. • Once the cement has been properly stored it should not be disturbed until it is to be used. The practice of moving and restacking the bags, exposes fresh cement to air.
  87. 87. Storage of Cement
  88. 88. Physical Properties of Portland Cement • The important physical properties of cement are: • Fineness • Standard Consistency • Initial and final setting time • Compressive strength • Soundness
  89. 89. Physical Properties of Portland Cement • Fineness: • The fineness of a cement is a measure of the size of the particle of cement, and is expressed in terms of specific surface of the cement. Since the hydration starts at the surface of the cement particles, it is the total surface area of cement that represents the material available for hydration. For a given weight of cement, the surface area of cement is more for a finer cement than for a coarser cement. The finer the cement, the higher is the rate of hydration as more surface area is available for chemical reaction. This results in the early development of strength. Moreover, fine cement bleeds less than coarse one. • Fineness of cement can be determined by two tests: • By Sieve Test • By Air Permeability Test
  90. 90. Fineness of cement can be determined by two tests Sieve Test Air Permeability Test Air Permeability Test Sieve Test
  91. 91. Physical Properties of Portland Cement • Standard Consistency Test: • The Standard consistency of cement paste is defined as that consistency which will permit a Vicat Plunger having 10 mm diameter and 50 mm length to penetrate to a depth of 33 to 35 mm from the top of the mould of 40 mm height. • The standard consistency of the cement paste is some time called as normal consistency test. The standard consistency parameter is used to determine, initial setting time, final setting time, soundness of cement and compressive strength of cement.
  92. 92. Standard Consistency Test
  93. 93. Physical Properties of Portland Cement • Initial and Final Setting Time • When the cement is mixed with water to make a soft paste, it becomes gradually less plastic and finally becomes a hard mass. In this process of setting, a stage is reached when the cement paste is sufficiently rigid to withstand a definite amount of pressure. The time to reach this stage is termed as setting time. The setting time is divided into 2 parts, namely initial setting time and final setting time. • The period elapsing between the time when water is added and the time at which the cement paste start loosing plasticity is termed as Initial Setting Time. • The period elapsing between the time when water is added to the cement and the time at which the cement paste completely loose its plasticity is termed as final setting time. • For ordinary Portland cement Initial setting time is 30 min and final setting time is 600 min (10 Hrs).
  94. 94. Initial and Final Setting Time
  95. 95. Physical Properties of Portland Cement • Compressive Strength Test: Compressive strength is one of the important properties of cement. Cement mortar (1:3) cubes having an area 50 cm2 are used for the determination of compressive strength of cement. • The test is carried out as per IS 4031 (Part VI): 1988
  96. 96. Compressive Strength Test
  97. 97. Physical Properties of Portland Cement • Soundness Test: • Undesirable expansion of some of the constituents of cement after setting is known as unsoundness. • The unsoundness in cement is due the presence of excess of free lime, magnesia, and calcium sulphate • The unsoundness of cement may be reduced by: • Limiting the magnesia content to less than 6 % • Through mixing • Fine grinding • Allowing the cement to aerate for several days. • Two main tests for determining soundness are Le Chatelier Test and the Auto Clave Test.
  98. 98. Le Chatelier Test
  99. 99. References • Concrete Technology by: R.P. Rethaliya • Concrete Technology by . M.S. Shetty • Internet websites •
  100. 100. Thanks….