1. Unit 1 Concrete Ingredients Cement

2. What is Cement A cement is a binder, a substance used in construction that sets and hardens and can bind other materials together.

3. Use of Cement Cement mortar for Masonry work, plaster and pointing etc. Concrete for laying floors, roofs and constructing lintels,beams,weathershed,stairs,pillars etc. Construction for important engineering structures such asbridge,culverts,dams,tunnels,light house,clocks,etc. Construction of water,wells, tennis courts,septic tanks, lamp posts, telephone cabins etc. Making joint for joints,pipes,etc. Manufacturing of precast pipes,garden seats, artistically designed wens, flower posts, etc. Preparation of foundation, water tight floors, footpaths, etc.

4. Types of Cement Ordinary Portland cement Rapid hardening Portland cement Low heat Portland cement Sulphate resisting Portland cement Pozzolanic cement

5. Ordinary Portland cement Ordinary Portland cement is the most common type of cement This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450°C in a kiln, in a process known as calcination, whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide, or quicklime, which is then blended with the other materials that have been included in the mix. The resulting hard substance, called 'clinker', is then ground with a small amount of gypsum into a powder to make 'Ordinary Portland Cement'(often referred to as OPC).

6. This type of cement use in construction when there is no exposure to sulphates in the soil or ground water. Lime saturation Factor is limited between i.e. 0.66 to 1.02. Free lime-cause the Cement to be unsound. Percentage of (AL 2 O 3 /Fe2O3) is not less than 0.66. Insoluble residue not more than 1.5%. Percentage of SO 3 limited by 2.5% when C 3 A 7%. Loss of ignition -4%(max) Percentage of Mg0-5% (max.) Fineness -not less than 2250 cm 2 /g.

7. RAPID HARDENING CEMENT: Also known as early gain in strength of cement. This cement contains more %age of C3S and less %age of C2S, high proportion of C3S will impart quicker hydration The high strength at early stage is due to finer grinding, as fineness of cement will expose greater surface area for the action of water. The strength obtained by this cement in 03 days is same as obtained by O.P.C in 7 days. Initial and final setting times are same as OPC.ie. 30mins and 10 hrs. And soundness test by Le-Chatielier is 10mm and Autoclave is 0.8%. Greater lime content than OPC

8. LOW HEAT CEMENT Low percentage of tri-calcium aluminates (C3A) and silicate (C3S) and high %age of di-calcium silicate (C2S) to keep heat generation low. Very slow rate of developing strength as rate of C3S Content is low. Heat evolved @ 7 days-66 cal/g and 28 days-75 cal/g initial set time-1 hr, final set time-10 hrs Better resistance to chemical attack than OPC.

9. SULPHATE RESISTING CEMENT It is modified form of O.P.C and is specially manufactured to resist the sulphates. This cement contains a low percentage of C3A and high percentage of C3S This cement requires longer period of curing. It develops strength slowly, but ultimately it is as strong as O.P.C.

10. Portland Pozzolana Cement (PPC) OPC clinker and Pozzolana (Calcined Clay, Surkhi and Fly ash) ground together. Produces less heat of hydration and offers great resistance to attacks of Sulphates. Used in marine works and mass concreting. Ultimate strength is more than OPC. Low shrinkage on drying Water tightness.

11. Grade of Cement Cube 5 cm X 5 cm mortar cube is tested for 28 days strength Grade 33 is that cement, which exhibits strength more than 33 Similarly, when it is more than 43 Mpa when strength is more than 43 And if it is more than 53 Mpa, then it is 53 grade cement

12. Various Brand of Cements

13. Constituents of Cement Portland cement is manufactured by crushing, milling and proportioning the following materials: – Lime or calcium oxide, CaO: from limestone, chalk, shells, shale or calcareous rock – Silica, SiO 2 : from sand, old bottles, clay or argillaceous rock – Alumina, Al 2 O 3 : from bauxite, recycled aluminum, clay – Iron, Fe 2 O 3 : from from clay, iron ore, scrap iron and fly ash – Gypsum, CaSO 4.2H 2 0: found together with limestone

14. Properties of cement compounds Tricalcium aluminate, C 3 A It liberates a lot of heat during the early stages of hydration, but has little strength contribution. Gypsum slows down the hydration rate of C 3 A. Cement low in C 3 A is sulfate resistant. Tricalcium silicate, C 3 S This compound hydrates and hardens rapidly. It is largely responsible for portland cement’s initial set and early strength gain. Dicalcium silicate, C 2 S C 2 S hydrates and hardens slowly. It is largely responsible for strength gain after one week.

15. Hydration of Cement Portland cement is a hydraulic cement, hence it derives its strength from chemical reactions between the cement and water. The process is known as hydration.

16. Physical properties of Cement Fineness Soundness Consistency Setting Time Compressive Strength Heat of hydration Loss on Ignition Specific gravity (Relative density) Bulk Density

17. 1. Fineness Fineness, or particle size of portland cement affects rate of hydration, which is responsible for the rate of strength gain. The smaller the particle size, the greater the surface area to volume ratio, which means more area available for water cement reaction per unit volume. Approximately 95% of cement particles are smaller than 45 micron with the average particle size about 15 micron. Fineness is measured in terms of surface area per unit mass. Fineness can be tested by Wagner turbidimeter test, Blaine Air permeability test, 45 micrometer sieve and electronic particle size analyser

18. 2. Soundness Soundness refers to the ability of a hardened cement paste to retain its volume after setting. Lack of soundness is observed in the cement samples containing excessive amounts offree lime or magnesia. Autoclave expansion test is used to determine soundness of cement.

19. 3. Consistency Consistency of a cement paste refers to its ability to flow. Normal consistency pastes are required to be prepared for testing cement specimens. A paste is said to have a normal consistency when the plunger of Vicat apparatus penetrates it by 10±1 mm. the corresponding watercement ratio is reported.

20. 4. Setting Time Initial setting time is the time that elapsed from the instance of adding water untill the pastes ceases to behave as fluid or plastic. Whereas final setting time referred to the time required for the cement paste to reach certain state of hardness to sustain some load. Setting time is tested by Vicat apparatus or Gillmore needle.

21. 5. Compressive strength Compressive strength of cement is tested by 50 mm mortar cubes made by using standard sand and cured in a prescribed way. The cubes are tested under a compression testing machine. The strength of cement varies with time, therefore in general it is reported as 3 day, 7 day or 28 day strength.

22. 6. Heat of Hydration The heat generated during the reaction of cement and water is known as heat of hydration. The factors affecting heat of hydration are C3A, C2S, water cement ratio, fineness of cement and curing temperature. Conduction calorimeter is used to test heat of hydration.

23. Loss of Ignition A cement sample of known weight is heated between 900-1000° C (1650-1830°F) until a constant weight is obtained. The weight loss of the sample due to heating is then determined. A high loss on ignition (more than 3%) indicates prehydration and carbonation, which may be due to inappropriate storage or adulteration.

24. Specific Gravity (relative density) Specific gravity is generally required in mix proportioning for concrete. The particle density (measured by excluding the air between particles) of OPC is found to be in the range of 3100 to 3250 Kg per cubic meter. The relative density of OPC is assumed as 3.15. The density of cement is determined by Le Chatelier apparatus.

25. Bulk Density The bulk density can be determined by dividing the mass of cement particles and air between particles by the volume of cement sample. Bulk density of OPC ranges from 830 kg/m 3 to 1650 kg/m 3

26. Field Tests for Cement 1. Open the bag and take a good look at the cement. There should not be any visible lumps. The colour of the cement should normally be greenish grey

27. 2. Put your hand into the cement bag. It must give you a cool feeling. There should not be any lump inside.

28. 3. Take a pinch of cement and feel between the fingers. It should give you smooth and not a gritty feeling. 4. Take a handful of cement and throw it on a bucket full of water. The particles should float for some time before they sink.

29. Take about 100 grams of cement and a small quantity of water and make a stiff paste. From the stiff paste, pat a cake with sharp edges. Put it on a glass plate and slowly take it under water in a bucket. See that the shape of the cake is not 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 attain some strength. 5.5.

30. Laboratory Test 1.Fineness Test 2.Standard Consistency Test 3.Setting Time Test 4.Strength Test 5.Soundness Test

31. 1. Finesness Test Fineness of cement is tested in two ways 1.By sieving 2.By determination of specific surface (total surface area of all the particles in one gram of cement) by air permeability apparatus.It is expressed as cm 2 /g or m 2 /kg.

32. IS code for Fineness test IS 4031(Part 1):1996 Methods of physical tests for hydraulic cement: Part 1 Determination of fineness by dry sieving IS 4031(Part 2):1999 Methods of physical tests for hydraulic cement: Part 2 Determination of fineness by specific surface by Blaine air permeability method

34. Apparatus for Fineness test Blaine air permeability apparatus Sieves

35. Procedure For Fineness Test by Seiving Agitate the sample of cement to be tested by shaking for 2 minutes. Stir the resulting powder gently using a clean dry rod in order to distribute the fines throughout the cement. Attach a pan under the sieve to collect the cement passing the sieve. Weigh approximately 10 g of cement to the nearest 0.01 g and place it on the sieve. Fit the lid over the sieve. Agitate the sieve by swirling, planetary and linear movement until no more fine material passes through it. Remove and weigh the residue. Express its mass as a percentage (R 1 ) of the quantity first placed in the sieve. Repeat the steps 3 to 5 with a fresh sample to obtain R 2. Note : If R 1 & R 2 differ by more than 1%, then carryout a third sieving and calculate R 3. Calculate the residue of cement R as the mean of R 1 & R 2 (or R 1, R 2 & R 3 ) in %, expressed to the nearest 0.1%.

37. Place the perforated disc on the ledge at the bottom of the cell and place on it a new filter paper disc. Place the weighed quantity of cement, m1, in the cell. Place a second new filter paper disc on the levelled cement. Insert the plunger and press it gently but firmly until the lower face of the cap is in contact with the cell. Slowly withdraw the plunger, rotate it through 90 ° and press once again. The bed is now compacted and ready for the permeability test. Test is performed on the Blaine apparatus. It is practically manometer in the U-tube form. One arm of the manometer is provided at the top with conical socket to form an airtight fit with the conical surface of the cell.

38. The same arm has four etched lines M1 to M4 and T-joint, which lead to an airtight stopcock beyond which is attached aspiration rubber bulb. Manometer is filled to the level of the lowest etched line with non- volatile, non-hygroscopic liquid of low viscosity and density (such as light mineral oil). Insert the conical surface of the cell into the socket at the top of the manometer. Open the stopcock and with gentle aspiration raise the level of the manometer liquid to that of the highest etched line. Close the stopcock and the manometer liquid will begins to flow. Start the timer as the liquid reaches the second etched line and stop it when the liquid reaches the third etched line. Record the time, t, and the temperature, T. The procedure repeats three times Calculate three values of the specific surface and the mean of them.

40. 2. Standard Consistency Test (IS:4031-PART4-1988) Standard consistency of a cement paste is defined as that consistency which will permit a vicat plunger having 10 mm dia and 50 mm length to penetrate to a depth of 33-35 mm from top of the mould.

42. Procedure 1.Take 400 g of cement and place it in the enameled tray. 2.Mix about 25% water by weight of dry cement thoroughly to get a cement paste. Total time taken to obtain thoroughly mixed water cement paste i.e. “Gauging time” should not be more than 3 to 5 minutes. 3.Fill the vicat mould, resting upon a glass plate, with this cement paste. 4.After filling the mould completely, smoothen the surface of the paste, making it level with top of the mould. 5.Place the whole assembly(i.e. mould + cement paste + glass plate) under the rod bearing plunger. 6.Lower the plunger gently so as to touch the surface of the test block and quickly release the plunger allowing it to sink into the paste. 7.Measure the depth of penetration and record it. 8.Prepare trial pastes with varying percentages of water content and follow the steps (2 to 7) as described above, until the depth of penetration becomes 33 to 35 mm.

43. Calculation Calculate percentage of water (P) by weight of dry cement required to prepare cement paste of standard consistency by following formula, and express it to the first place of decimal. Where, W=Quantity of water added C=Quantity of cement used

44. 3. Setting Time Test (IS:4031-PART 5-1988) Initial setting time is that time period between the time water is added to cement and time at which 1 mm square section needle fails to penetrate the cement paste, placed in the Vicat’s mould 5 mm to 7 mm from the bottom of the mould. Final setting time is that time period between the time water is added to cement and the time at which 1 mm needle makes an impression on the paste in the mould but 5 mm attachment does not make any impression.

46. Procedure (A)TEST BLOCK PREPARATION 1.Before commencing setting time test, do the consistency test to obtain the water required to give the paste normal consistency (P). 2.Take 400 g of cement and prepare a neat cement paste with 0.85P of water by weight of cement. 3.Gauge time is kept between 3 to 5 minutes. Start the stop watch at the instant when the water is added to the cement. Record this time (t 1 ). 4.Fill the Vicat mould, resting on a glass plate, with the cement paste gauged as above. Fill the mould completely and smooth off the surface of the paste making it level with the top of the mould. The cement block thus prepared is called test block.

47. Procedure (B)INITIAL SETTING TIME 1.Place the test block confined in the mould and resting on the non-porous plate, under the rod bearing the needle. 2.Lower the needle gently until it comes in contact with the surface of test block and quick release, allowing it to penetrate into the test block. 3.In the beginning the needle completely pierces the test block. Repeat this procedure i.e. quickly releasing the needle after every 2 minutes till the needle fails to pierce the block for about 5 mm measured from the bottom of the mould. Note this time (t 2 ).

48. Procedure (C)FINAL SETTING TIME 1.For determining the final setting time, replace the needle of the Vicat’s apparatus by the needle with an annular attachment. 2.The cement is considered finally set when upon applying the final setting needle gently to the surface of the test block; the needle makes an impression thereon, while the attachment fails to do so. Record this time (t 3 ).

49. 4. Strength Test (IS:4031-PART 6-1988) Compressive strength of cement is determined by compressive strength test on mortar cubes compacted by means of a standard vibration machine. Standard sand (IS:650) is used for the preparation of cement mortar. The specimen is in the form of cubes 70.6mm*70.6mm*70.6mm.

50. Procedure Take 200 g of cement and 600 g of standard sand and mix them dry thoroughly. Add (P/4 + 3)% of water (where P is % of water required for preparing paste of standard consistency) to the dry mix of cement and sand and mix thoroughly for a minimum of 3 minutes and maximum of 4 minutes to obtain a mix of uniform colour. If even in 4 minutes uniform colour of the mix is not obtained reject the mix and mix fresh quantities of cement, sand and water to obtain a mix of uniform colour. Place the thoroughly cleaned and oiled (on interior face) mould on the vibrating machine and hold it in position by clamps provided on the machine for the purpose. Fill the mould with entire quantity of mortar using a suitable hopper attached to the top of the mould for facility of filling and vibrate it for 2 minutes at a specified speed of 12000±400 per minute to achieve full compaction. Remove the mould from the machine and keep it in a place with temp of 27±2 0 C and relative humidity of 90% for 24 hours.

51. At the end of 24 hrs remove the cube from the mould and immediately submerge in fresh clean water. The cube be taken out of the water only at the time of testing. Prepare at least 6 cubes in the manner explained above. Place the test cube on the platform of a compressive testing machine without any packing between the cube and the plates of the testing machine. Apply the load steadily and uniformly, starting from zero at a rate of 35 N/mm 2 /minute

52. Calculation Where, P=Maximum load applied to the cube. (N) A=Cross sectional area (Calculated from the mean dimensions) (mm 2 )

53. Compressive strength is reported to the nearest 0.5 N/mm 2. Specimens that are manifestly faulty, or that give strengths differing by more than 10% from the average value of all the test specimen should not be considered. Test three cubes for compressive strength for each period of curing.

55. 5. Soundness Test (IS:4031-PART 3-1988) In the soundness test a specimen of hardened cement paste is boiled for a fixed time so that any tendency to expand is speeded up and can be detected. Soundness means the ability to resist volume expansion.

56. Procedure 1.Before commencing setting time test, do the consistency test to obtain the water required to give the paste normal consistency (P). 2.Prepare a paste by adding 0.78 times the water required to give a paste of standard consistency (i.e. 0.78P). 3.Lightly oil the Le-chatelier mould and place it on a lightly oiled glass sheet. 4.Fill the mould with the prepared cement paste. In the process of filling the mould keep the edge of the mould gently together. 5.Cover the mould with another piece of lightly oiled glass sheet, place a small weight on this covering glass sheet. 6.Submerge the whole assembly in water at a temperature of 27 ± 2 0 C and keep there for 24 hours. 7.Remove the whole assembly from water bath and measure the distance separating the indicator points to the nearest 0.5 mm (L 1 ). 8.Again submerge the whole assembly in water bath and bring the temperature of water bath to boiling temperature in 25 to 30 minutes. Keep it at boiling temperature for a period of 3 hours. 9.After completion of 3 hours, allow the temperature of the water bath to cool down to room temperature and remove the whole assembly from the water bath. 10.Measure the distance between the two indicator points to the nearest 0.5 mm (L 2 ).

57. CALCULATIONS Soundness/expansion of cement = L 1 -L 2 L 1 =Measurement taken after 24 hours of immersion in water at a temp. of 27 ± 2 0 C L 2 =Measurement taken after 3 hours of immersion in water at boiling temperature. Calculate the mean of two values to the nearest 0.5 mm.