2. UNIT I CONSTITUENT MATERIALS Cement Different types Chemical composition and Properties Tests on cement-IS Specifications Aggregates Classification Mechanical properties and tests as per BIS Grading requirements Water Quality of water for use in concrete.

3. UNIT II CHEMICAL AND MINERAL ADMIXTURES Accelerators Retarders Plasticisers Super plasticizers Water proofers Mineral Admixtures like Fly Ash Silica Fume Ground Granulated Blast Furnace Slag and Metakaoline Their effects on concrete properties

4. UNIT III PROPORTIONING OF CONCRETE MIX Principles of Mix Proportioning Properties of concrete related to Mix Design Physical properties of materials required for Mix Design Design Mix and Nominal Mix BIS Method of Mix Design Mix Design Examples

5. UNIT IV FRESH AND HARDENED PROPERTIES OF CONCRETE Workability Tests for workability of concrete Slump Test and Compacting factor Test Segregation and Bleeding Determination of Compressive and Flexural strength as per BIS Properties of Hardened concrete Determination of Compressive and Flexural strength Stress-strain curve for concrete Determination of Young’s Modulus.

6. UNIT V SPECIAL CONCRETES Light weight concretes High strength concrete Fibre reinforced concrete Ferrocement Ready mix concrete SIFCON Shotcrete Polymer concrete High performance concrete Geopolymer Concrete

7. TEXTBOOKS: 1.Gupta.B.L., Amit Gupta, "Concrete Technology", Jain Book Agency, 2010. 2.Shetty,M.S, "Concrete Technology", S.Chand and Company Ltd, New Delhi, 2003

8. REFERENCES: 1.Santhakumar,A.R; "Concrete Technology", Oxford University Press, New Delhi, 2007 2.Neville, A.M; "Properties of Concrete", Pitman Publishing Limited, London,1995 3.Gambir, M.L; "Concrete Technology", 3rd Edition, Tata McGraw Hill Publishing Co Ltd, New Delhi, 2007 4.IS10262-1982 Recommended Guidelines for Concrete Mix Design, Bureau of Indian Standards, New Delhi, 1998

10.  Cement is a well-known building material and has occupied an indispensable place in construction works.  A cement is a binder, a substance that sets and hardens and can bind other materials together.  There are variety of cements available in the market and each type is used under certain conditions due to its special properties.

11.  A mixture of cement and sand when mixed with water to form a paste is known as cement mortar whereas the composite product obtained by mixing cement, water and an inert matrix of sand and gravel or crushed stone is called cement concrete.

12.  The cement commonly used is Portland cement and the fine and coarse aggregates used are those that are usually obtainable, from nearby sand, gravel or rock deposits.  In order to obtain a strong, durable and economical concrete mix, it is necessary to understand the characteristics and behaviour of the ingredients.

13.  Portland cement is defined as hydraulic cement, i.e. a cement that not only hardens by reacting with water but also forms a water- resistant product.  The ingredients of concrete can be classified into two groups, namely active and inactive.

14.  The active group consists of cement and water, whereas the inactive group comprises fine and coarse aggregates.  The inactive group is also sometimes called the inert matrix.  Although all materials that go into a concrete mixture is essential, cement is by far the most important constituent because it is usually the delicate link in the chain.

15.  The function of cement is, first to bind the sand and coarse aggregates together and second to fill the voids in between sand and coarse aggregate particles to form a compact mass.  Although cement constitutes only about 10 percent of the volume of the concrete mix, it is the active portion of the binding medium and the only scientifically controlled ingredient of concrete.

16.  Joseph Aspdin patented a similar material, which he called Portland cement, because the render made from it was in color similar to the prestigious Portland stone.

17.  The raw materials used for the manufacture of cement consist mainly of 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 compositions are responsible for influencing the various properties of cement, in addition to rate of cooling and fineness of grinding.

18.  The table below shows the approximate oxide composition limits of ordinary Portland Cement. OxidePercent content CaO60-67 SiO 2 17-25 Al 2 O 3 3.0-8.0 Fe 2 O 3 0.5-6.0 MgO0.1-4.0 Alkalies (k 2 O, Na 2 O)0.4-1.3 SO 3 1.3-3.0

19. Functions of cement ingredients Lime:  Controls strength and soundness. Its deficiency reduces strength and setting time. Silica:  Gives strength due to the formation of dicalcium and tricalcium silicates. Excess of it causes slow setting. Alumina:  Responsible for quick setting. It acts as a flux and lowers the clinkering temperature. If in excess it lowers the strength.

20.  Calcium Sulphate: Present in the form of gypsum and its function is to increase the initial setting time of cement.  Iron Oxide: Imparts color and help in fusion of  different ingredients of cement.  Magnesia: Imparts color and hardness. If in excess  causes cracks and makes cement unsound.

21.  Sulphur: A small amount is used in making sound  cement. If in excess causes cement to become  unsound.  Alkalies: If excess in cement, causes alkali- aggregate  reaction (aggregates having silica react with the alkali  hydroxides in concrete, causing expansion and  cracking ), efflorescence and discoloration when used  in concrete.

22.  The oxides present in the raw materials when subjected to high clinkering temperature combine with each other to form complex compounds.  The identification of the major compounds is largely based on R.H. Bogue’s work and hence it is called “Bogue’s Compounds”.  The table below lists the major compounds.

23. Name of the CompoundFormulaAbbreviated Formula Tricalcium silicate3 CaO.SiO 2 C3SC3S Dicalcium silicate2CaO.SiO 2 C2SC2S Tricalcium Aluminate3CaO.Al 2 O 3 C3AC3A Tetracalcium aluminoferrite 4CaO.Al 2 O 3.Fe 2 O 3 C 4 AF It is to be noted that for simplicty sake abbreviated notations are used. C stands for CaO, S for SiO 2, A for Al 2 O 3, F for Fe 2 O 3 and H for H 2 O

24.  In addition to the four major compounds, there are many minor compounds formed in the kiln.  The influence of these minor compounds on the properties of cement or hydrated compounds is not significant.  Two of the minor oxides namely K 2 O and Na 2 O referred to as alkalis in cement are of some importance.

25.  Tricalcium silicate and dicalcium silicate are the most important compounds responsible for strength.  Together they constitute 70 to 80 percent of cement.

26.  Anhydrous cement does not bind fine and coarse aggregate.  It acquires adhesive property only when mixed with water.  The chemical reactions that take place between cement and water is referred as hydration of cement.  The chemistry of concrete is essentially the chemistry of the reaction between cement and water.

27.  On account of hydration certain products are formed.  These products are important because they have cementing or adhesive value.  The quality, quantity, continuity, stability and the rate of formation of the hydration products are important.  Anhydrous cement compounds when mixed with water, react with each other to form hydrated compounds of very low solubility.

28.  The hydration of cement can be visualised in two ways.  The first is “through solution” mechanism.  In this the cement compounds dissolve to produce a supersaturated solution from which different hydrated products get precipitated.  The second possibility is that water attacks cement compounds in the solid state converting the compounds into hydrated products starting from the surface and proceeding to the interior of the compounds with time.

29.  It is probable that both “through solution” and “solid state” types of mechanism may occur during the course of reactions between cement and water.  The former mechanism may predominate in the early stages of hydration in view of large quantities of water being available, and the latter mechanism may operate during the later stages of hydration.

30.  The reaction of cement with water is exothermic.  The reaction liberates a considerable quantity of heat.  This liberation of heat is called heat of hydration.

31.  On mixing cement with water, a rapid heat evolution, lasting a few minutes, occurs.  The heat evolution is probably due to the reaction of solution of aluminates and sulphates (ascending peak A).  This initial heat evolution ceases quickly when the solubility of aluminate is depressed by gypsum(descending peak A).  Next heat evolution is on account of formation of ettringite and also may be due to the reaction of C 3 S (ascending peak B)

32.  The chemical reaction of C 3 S with water can be expressed as  C 3 S + water C-S-H + C-H +Heat  Where C-S-H is calcium silicate hydrate and C-H is calcium hydrate.  C-S-H calcium silicate hydrate constitutes 50-60% of the solids in the paste.  It forms a continuous binding matrix.  It is amorphous and fibrous and hence has a large surface area.  It is an important factor for the strength development of cement paste.

33.  C-H calcium hydrate makes up about 20% of the solids in the paste.  It exists in the form of thick, crystalline hexagonal plates and is embedded in the C-S-H matrix.  Its growth fills the pore spaces.  It does not significantly contribute to strength.  Its leaching causes white patches and efflorescence.

34.  The hydration of C 2 S is similar to the hydration of C 3 S.  The same products are generated.  However, C 2 S reacts slowly and hence generates less heat.  It contributes to strength development at latter stages.

35.  This hydration reaction produces a substance called ettringite as follows:  C 3 A + gypsum + water ettringite +heat  C 3 A+ettringite+water monosulphoaluminate  If the amount of gypsum is too little, C 3 A will react fast and can cause a ‘flash set’.  On the other hand, too much gypsum will delay setting and cause undue expansion.

36. As shown in the figure, ettringite is a crystalline and needle like substance.

37.  It constitutes about 10–20% of the solid content.  It is a long, slender and prismatic crystal and is stable only in the presence of gypsum.  It plays a minor role in strength development but contributes considerably to durability.  Monosulphoaluminate is a stable hydration product.  It is fairly crystalline.

38.  The figure shows thin irregular plates clustered like a flower.  Hence it fills the pores and can reform ettringite in the presence of sulphate ions.

39.  The hydration of C 4 AF is similar to that of C 3 A, the same products are formed.  However, C 4 AF reacts slowly and hence generates less heat and combines well with gypsum.

40.  In summary, the hydration of cement occurs at the surface of the grain.  All the compounds react simultaneously; a compound reaction takes place.  The smaller grains hydrate first and the larger grains become smaller while they hydrate.  Some very large grains never hydrate completely.

41.  The hydration rate has the following hierarchy: C 3 A, C 3 S, C 4 AF and C 2 S  Ettringite is formed first, followed by C-H and C-S-H.  There is no change in the total volume of the cement paste as a result of hydration.  After hydration, the paste composition consists of both the solid and water phases.  Thus hydration is a chemical reaction.  The Bogue compounds react to form C-S-H, C-H, ettringite, monosulphoaluminate and heat.

42.  Ordinary Portland Cement  Ordinary Portland Cement 33 Grade – IS 269:1989  Ordinary Portland Cement 43 Grade – IS 8112: 1989  Ordinary Portland Cement 53 Grade – IS 12269:1987  Rapid hardening cement – IS 8041: 1990  Extra Rapid Hardening Cement  Sulphate Resisting Cement – IS 12330:1998  Portland Slag Cement – IS 455: 1989

43.  Quick Setting Cement  Super Sulphated Cement - IS 6909 :1990  Low Heat Cement – IS 12600: 1989  Portland Pozzolana Cement – IS 1489(Part I) 1991 (Flyash based) IS 1489(PartII) 1991 (Calcined based)  Air Entraining Cement  Coloured Cement : White Cement – IS 8042:1989

44.  Hydrophobic Cement – IS 8043 : 1991  Masonry Cement – IS 3466: 1988  Expansive Cement  Oil Well Cement – IS 8229:1986  Rediset Cement  Concrete Sleeper grade Cement – IRS-T 40: 1985  High Alumina Cement – IS 6452:1989  Very High Strength Cement

45.  Prior to 1987, there was only one grade of OPC which was governed by IS 269-1976.  After 1987 higher grade cements were introduced in India.  The OPC was classified into three grades, namely 33 grade, 43 grade and 53 grade depending upon the strength of the cement at 28 days when tested as per IS 4031-1988.

46.  It has been possible to upgrade the qualities of cement by using  high quality limestone  Modern equipments  Closer on line control of constituents  Maintaining better particle size distribution  Finer grading  Better packing

47.  This is similar to OPC.  As the name indicates it develops strength rapidly and as such it may be more appropriate to call it as high early strength cement.  Rapid hardening cement develops strength at the age of three days, the same strength as that is expected of ordinary portland cement at seven days.

48.  The rapid rate of development of strength is attributed to  the higher fineness of grinding (specific surface not less than 3250 sq.cm per gram)  higher C 3 S  lower C 2 S content  A higher fineness of cement particles expose greater surface area for action of water and also higher proportion of C 3 S results in quicker hydration.

49.  Consequently, rapid hardening cement gives out much greater heat of hydration during the early period.  Therefore, rapid hardening cement should not be used in mass concrete construction.

50.  The use of rapid hardening cement is recommended in the following situations:  In pre-fabricated concrete construction where formwork is required to be removed early for re-use elsewhere.  Road repair works  In cold weather concrete where the rapid rate of development of strength reduces the vulnerability of concrete to the frost damage.

51.  It is obtained by inter grinding calcium chloride with rapid hardening Portland Cement.  The normal addition of calcium chloride should not exceed 2 percent by weight of the rapid hardening cement.

52.  It is necessary that the concrete made by using extra rapid hardening cement should be transported, placed and compacted and finished within about 20 minutes.  It is also necessary that this cement should not be stored for more than a month.  This cement accelerates the setting and hardening process.

53.  A large quantity of heat is evolved in a very short time after placing.  The acceleration of setting, hardening and evolution of this large quantity of heat in the early period of hydration makes the cement very suitable for concreting in cold weather.  The strength is about 25 percent higher than that of rapid hardening cement at one or two days and 10–20 percent higher at 7 days.

54.  The gain of strength will disappear with age and at 90 days the strength of extra rapid hardening cement or the OPC may be nearly the same.  There is some evidence that there is small amount of initial corrosion of reinforcement when extra rapid hardening cement is used, but in general, this effect does not appear to be progressive and as such no harm in using this cement in reinforced work.  However, its use in prestress concrete construction is prohibited.

55.  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 approximately 227% of the volume of the original aluminates.  Their expansion within the frame work of hardened cement paste results in cracks and subsequent disruption.

56.  Solid sulphate do not attack the cement compound.  Sulphates in solution permeate into hardened concrete and attack calcium hydroxide, hydrated calcium aluminate and even hydrated silicates.  This is known as sulphate attack.

57.  Sulphate attack is greatly accelerated if accompanied by alternate wetting and drying which normally takes place in marine structures in the zone of tidal variations.  To remedy the sulphate attack, the use of cement with low C 3 A content is found to be effective.

58.  Such cement with low C 3 A and comparatively low C 4 AF content is known as Sulphate Resisting Cement.  In other words, this cement has a high silicate content.  The specification generally limits the C 3 A content to 5 percent.  In many of its physical properties, sulphate resisting cement is similar to OPC.

59.  The use of sulphate resisting cement is recommended under the following conditions:  Concrete to be used in marine condition  Concrete to be used in foundation and basement, where soil is infested with sulphates  Concrete used for fabrication of pipes which are likely to be buried in marshy region or sulphate bearing soils.  Concrete to be used in the construction of sewage treatment works.

60.  Portland slag cement is obtained by mixing portland cement clinker, gypsum and granulated blast furnace slag (a waste product from blast furnaces) in suitable proportions and grinding the mixture to get a thorough and intimate mixture between the constituents.  Portland blast furnace cement is similar to OPC with respect to fineness, setting time, soundness and strength.

61.  It is generally recognized that the rate of hardening of Portland blast furnace slag cement in mortar or concrete is somewhat slower than that of OPC during the first 28 days, but thereafter increases, so that at 12 months the strength becomes close to or even exceeds those of Portland cement.  The heat of hydration of Portland blast furnace cement is lower than that of OPC.

62.  So this cement can be used in mass concrete structures with advantage.  However, in cold weather the low heat of hydration of Portland blast furnace cement coupled with moderately low rate of strength development, can lead to frost damage.

63.  Extensive research shows that the presence of GGBS leads to the enhancement of the intrinsic properties of the concrete both in fresh and hardened states.  The major advantages currently recognised are:  Reduced rate of hydration  Refinement of pore structure  Reduced permeability  Increased resistance to chemical attack.

64.  This cement as the name indicates sets very early.  The early setting property is brought out by reducing the gypsum content at the time of clinker grinding.  This cement is to be mixed, placed and compacted very early.

65.  It is used mostly in under water construction where pumping is involved.  Use of quick setting cement in such conditions reduces the pumping time and makes it more economical.  It is also used in grouting operations.

66.  It is manufactured by grinding together a mixture of 80–85 percent granulated slag, 10–15 percent hard burnt gypsum and about 5 percent Portland cement clinker.  The product is ground finer than that of OPC.  Specific surface must not be less than 4000 cm 2 per gm.

67.  It has a low heat of hydration of about 40– 45 calories/gm at 7 days and 45–50 at 28 days.  It has high sulphate resistance.  Because of this property, it is used in foundation and marine constructions.  It is used in fabrication of reinforced concrete pipes which are likely to be buried in sulphate bearing soils.

68.  A low heat evolution is achieved by reducing the contents of C 3 S and C 3 A which are the compounds evolving the maximum heat of hydration and increasing C 2 S.  A reduction of temperature will retard the chemical action of hardening and so further restrict the rate of evolution of heat.

69.  The rate of evolution of heat will, therefore, be less and evolution of heat will extend over a longer period.  Therefore, the feature of low heat cement is a slow rate of gain of strength.  But the ultimate strength is same as that of OPC.

70.  It is manufactured by the intergrinding of OPC clinker with 10 to 25 % of pozzolanic material.  A pozzolanic material is essentially a siliceous or aluminous material which while in itself possessing no cementitious properties, which will, in finely divided form and in the presence of water, react with calcium hydroxide, liberated in the hydration process, at ordinary temperature, to form compounds possessing cementitious properties.

71.  The pozzolanic materials generally used for manufacture of PPC are calcined clay or Flyash.  Calcium silicates produce considerable quantities of calcium hydroxide, which is by and large a useless material from the point of view of strength or durability.

72.  If such useless mass could be converted into a useful cementitious product, it considerably improves quality of concrete.  The use of fly ash performs such a role.  The pozzolanic action is shown below. Calcium hydroxide +Pozzolana+ water C-S-H (gel)

73.  PPC can be used in all situations where OPC is used except where high early strength is of special requirement.  As PPC needs enough moisture for sustained pozzolanic activity, a little longer curing is desirable.

74.  Use of PPC would be particularly suitable for the following situations:  For hydraulic structures  For mass concrete structures like dam, bridge piers and thick foundation  For marine structures  For sewers and sewage disposal works etc.

75.  This cement is made by mixing a small amount of an air-entraining agent with OPC clinker at the time of grinding.  The following types of air-entraining agents could be used:  Alkali salts of wood resins

76.  Synthetic detergents of the alkyl-aryl sulphonate type  Calcium lignosulphate derived from the sulphite process in paper making  Calcium salts of glues and other proteins obtained in the treatment of animal hides.

77.  For manufacturing various coloured cements either white cement or grey Portland cement is used as a base.  The use of white cement as a base is costly.  With the use of grey cement only red or brown cement can be produced.  It consists of Portland cement with 5–10 percent of pigment.

78.  The raw materials used for manufacture of white cement are high purity limestone (96% CaCO 3 and less than 0.07% iron oxide).  The other raw materials are china clay with iron content of about 0.72 to 0.8%, silica sand, flourspar as flux and selenite as retarder.  Sea shells and coral can also be used as raw materials for production of white cement.

79.  It is obtained by grinding OPC clinker with water repellant film-forming substance such as oleic acid and stearic acid.  The water–repellant film formed around each grain of cement, reduces the rate of deterioration of the cement during long storage, transport, or under unfavourable conditions.  The film is broken out when the cement and aggregate are mixed together at the mixer exposing the cement particles for normal hydration.

80.  The film forming water-repellant material will entrain certain amount of air in the body of the concrete which incidentally will improve the workability of concrete.  The properties are same as the OPC except that it entrains a small quantity of air bubbles.

81.  Ordinary cement mortar, though good when compared to lime mortar with respect to strength and setting properties, is inferior to lime mortar with respect to workability, water-retentivity, shrinkage property and extensibility.  Masonry cement is a type of cement which is particularly made with such combination of materials, which when used for making mortar, incorporates all the good properties of lime mortar and discards all the not so ideal properties of cement mortar.

82.  This kind of cement is mostly used, as the name indicates, for masonry construction.  It contains certain amount of air-entraining agent and mineral admixtures to improve the plasticity and water retentivity.

83.  Concrete made with OPC shrinks while setting due to loss of free water.  This is known as drying shrinkage.  Cement used for grouting anchor bolts or grouting machine foundations or the cement used in grouting the prestress concrete ducts, if shrinks, the purpose for which the grout is used will be to some extent defeated.

84.  The type of cement which suffers no overall change in volume on drying is known as expansive cement.  Cement of this type has been developed by using an expanding agent and a stabilizer very carefully.  About 8–20 parts of the sulphoaluminate clinker are mixed with 100 parts of the Portland cement and 15 parts of the stabilizer.

85.  It is manufactured as per specification laid down by ministry of railways under IRS – T40: 1985.  It is a very finely ground cement with high C 3 S content designed to develop high early strength required for manufacture of concrete sleeper for Indian Railways.  This cement can be used for prestressed concrete elements, high rise buildings and high strength concrete.

86.  The desired properties of oil-well cement can be obtained in two ways:  By adjusting the compound composition of cement or  By adding retarders to OPC  The retarders are starches or cellulose products or acids.

87.  These retarding agents prevent quick setting and retains the slurry in mobile condition to facilitate penetration to all fissures and cavities.  Sometimes workability agents are also added to this cement to increase the mobility.

88.  A new product was needed for use in the precast concrete industry, for rapid repairs of concrete roads and pavements and slip- forming.  Associated Cement Company of India have developed this cement.

89. Properties of Rediset Cement  The cement allows a handling time of just about 8 to 10 minutes.  The strength pattern is similar to that of OPC.  It releases a lot of heat which is advantageous in winter concreting but excess heat liberation is detrimental to mass concrete.  The rate of shrinkage is fast but the total shrinkage is similar to OPC.  The sulphate resistance is poor.

90. Rediset can be used for  Very high early (3 to 4 hours)strength concrete and mortar.  Patch repairs and emergency repairs  Quick release of forms in the precast concrete products industry.  Slip-formed concrete construction  Construction between tides.

91.  High alumina cement is obtained by fusing or sintering a mixture, in suitable proportions, of alumina and calcareous materials and grinding the resultant product to a fine powder.  The raw materials used for the manufacture of high alumina cement are limestone and bauxite.

92.  An important use of high alumina cement is for making refractory concrete to withstand high temperatures in conjunction with aggregate having heat resisting properties.  RC is used for foundations of furnaces, boiler settings.  It is also used in fire pits, construction of electric furnaces, kilns etc.

93. Macro-defect-free cements(MDF)  MDF refers to the absence of relatively large voids or defects which are usually present in conventional mixed cement pastes because of entrapped air and inadequate dispersion.  In this process, 4–7% of one or several water soluble polymers (such as hydroxypropylmethyle cellulose, polyacrylamide of hydrolysed polyvinylacetate) is added as rheological aid to permit cement to be mixed with very small amount of water.

94. Densely packed system (DSP)  Normal Portland cement and ultra-fine silica fume are mixed.  The size of cement particles may vary from 0.5 to 100  and that of silica fume varies from 0.005 to 0.5 .  Silica fume is generally added from 5 to 25%.  A compressive strength of 270MPa have been achieved with silica fume substituted paste.

95. Pressure densification and warm pressing  A new approach has been developed for achieving very high strength by a method called “warm pressing” (applying heat and pressure simultaneously) to cement paste.  Compressive strength as much as 650MPa and tensile strength upto 68MPa have been obtained by warm pressing Portland and calcium aluminate cements.

96. High early strength cement  Lithium salts have been effectively used as accelerators in high alumina cement.  This has resulted in very high early strength in cement and a marginal reduction in later strength.  Strength as high as 4MPa has been obtained within 1 hour and 27MPa has been obtained within 3 hours time and 49MPa in one day.

97. Pyrament cement  Some cement industries in USA have developed a super high early strength and durable cement called by trade name “pyrament cement”.  This product is a blended hydraulic cement.  In this cement no chlorides are added during the manufacturing process.  It produces a high and very early strength of concrete and mortar which can be used for repair of Air Field Run-ways.

98. Magnesium Phosphate Cement (MPC)  It has been developed by Central Road Research Institute, New Delhi.  This is an important development for emergency repair of airfields, launching pads, road pavements suffering damage due to enemy bombing and missile attack.

99.  MPC has been found to possess unique hydraulic properties, controlled rapid set and early strength development.  MPC is prepacked mixture of dead burnt magnesite with fine aggregate mixed with phosphate.  It sets rapidly yields durable high strength cement mortar.

100.  Testing of cement can be brought under two categories:  Field testing  Laboratory Testing

101.  It is sufficient to subject the cement to field tests when it is used for minor works.  The following are the Field tests:  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.

102.  Thrust your hand into the cement bag. It must give you a cool feeling. There should not be any lump inside.  Take a pinch of cement and feel between the fingers. It should give a smooth and not a gritty feeling.  Take a handful of cement and throw it on a bucket full of water, the particles should float for some time before they sink.

103.  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.

104.  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.

105.  The following tests are conducted in the laboratory:  Fineness test  Soundness test  Setting time test  Strength test  Heat of hydration test  Chemical composition test

106.  The fineness of cement has an important bearing on  the rate of hydration  Rate of gain of strength  Rate of evolution of heat  Finer cement offers a greater surface area for hydration and hence faster the development of strength.

107.  Maximum number of particles in a sample of cement should have a size less than about 100 microns.  The smallest particle may have a size of about 1.5 microns.

108. Fineness of cement is tested in two ways:  By sieving – IS 4031(Part I) : 1996  By determination of specific surface (total surface area of all the particles in one gram of cement) by air-permeability apparatus. Expressed as cm 2 /gm or m 2 /gm. Generally Blaine Air Permeability apparatus is used - IS 4031(Part 2) : 1999

109. DETERMINATION OF FINENESS BY DRY SIEVING  To determine fineness of cement and particle size of cement.  Sample size – 100gms; sieving period – 15 minutes.  The standard sieve size used is 90 .  The % residual (retained) of cement on 90  sieve shall not exceed 10%.

110. Sieve used for determining Fineness of Cement

111. DETERMINATION OF FINENESS BY BLAINE AIR PERMEABILITY METHOD Specific surface test(Blaine Test)(Air Permeability Test)  To determine fineness of cement (particle size of cement) (5 to 30  ).  The fineness of cement is expressed in specific surface of cement i.e. cm 2 /gm or mm 2 /gm.  It is determined by Air Permeability test or Lea-nurse test.  The specific surface of cement shall not be less than 2250 cm 2 /gm or 225000 mm 2 /gm, for OPC.  For rapid hardening cement (RHC), it shall not be less than 3250 cm 2 /gm.

113. Consistency Test (Vicat Apparatus Test) IS : 4 0 3 1 ( Part 4 ) - 1 9 8 8  To determine standard quantity of water to produce standard cement paste.  The Vicat apparatus is used where the penetration of plunger in standard cement paste kept in Vicat mould shall be in a range of 33 to 35 mm from the top of the mould (5 to 7 mm from the bottom).

115. DETERMINATION OF INITIAL AND FINAL SETTING TIMES Initial setting time test (Vicat Apparatus) IS : 4031 (Part 5) – 1988 (Reaffirmed 2000)  To determine the time required by cement paste to loss its plasticity.

116.  The Vicat apparatus is used to determine initial setting time of cement where the penetration of the needle in the cement paste kept in Vicat mould (40 mm height) shall be in a range of 33 to 35 mm from the top.  It shall not be less than 30minutes(≥30min) for normal cement, 60 minutes for low heat cement and 5 minutes for rapid hardening cement.

117. Final setting time of cement (Vicat Apparatus)  The time required by cement paste to gain the proper shape and becoming hard considering from the instant of adding water is called final setting time.  i.e., the time elapsing from the instant of adding water to the cement and the instant when paste becomes hard(solid) is known as final setting time which is determined by Vicat apparatus where the enlarge needle should not penetrate the specimen of cement.  Final setting time shall not exceed 10hrs for normal cement, 30 minutes for rapid hardening cement.

118. DETERMINATION OF SOUNDNESS Lechatelier Test IS 4031 (Part 3 ) – 1988  To determine the soundness or unsoundness of cement due to presence of free lime only.  The expansion of cement paste specimen in Lechatelier mould shall not exceed 10mm.

120. Autoclave test  To determine soundness or unsoundness of cement due to presence of magnesia.  Due to presence of steam around the specimen expands caused by magnesia.  It shall not exceed 0.8% for soundness of cement.

121. Autoclave for determining soundness

122. Compressive Strength Test IS : 4031(Part 6):1988  To determine compressive strength of cement where the specimen is made up of 1:3 (cement : sand) proportion i.e. 185 gm cement and 555gm sand or 200gm cement and 600gm sand.

123.  The specimen is tested under compression machine at an age of 1 day, 3, 7 and 28 days.  The compressive strength of rapid hardening cement at 1 day curing shall not be less than 16 MPa and at an age of 3 days it shall not be less than 27.5 MPa.

125. Briquette Test  To determine strength of cement or concrete where the specimen is made in dumbbell shape (Zig Zag).  The tensile force is applied in the lab on the specimen till the specimen fails in tension.  The tensile strength shall be of 10% of compressive strength.

127. DETERMINATION OF HEAT OF HYDRATION Test for Heat of Hydration IS : 4031 ( Part 9 ) – 1988.  To determine the heat of hydration, especially for low heat cement.  A calorimeter is used in the lab.  The heat of hydration of low heat cement shall not exceed 75 cal/gm at 28 days.

128. Hydration Test Apparatus

129. Chemical Composition Test  Ratio of percentage of lime to percentage of silica, alumina and iron oxide, when calculated by the formulae Not greater than 1.02 and not less than 0.66.  The above is called lime saturation factor per cent.

130.  The aggregate is a relatively inert material and it imparts volume stability.  The aggregate provide about 75% of the body of the concrete and hence its influence is extremely important.  An aggregate should be of proper shape and size, clean, hard and well graded.  It must possess chemical stability and it must exhibit abrasion resistance.

131. Functions of Aggregate  It provides bulk to the concrete  It increases the density of the concrete mix.  It imparts volume stability.  It imparts durability to the concrete.  It is an inert material and is cheaper than cement.

132.  The functions of Fine aggregate are  To assist in producing workability and uniformity in the mix.  To assist the cement paste to hold the coarse aggregate particles in suspension.  To promote plasticity in the mixture and prevent possible segregation of paste and coarse aggregate.

133.  The natural source of aggregate is obtained from Igneous rocks (Granite, Basalt).  They are normally hard, tough and dense.  But the metamorphic rock (marble) is not suitable for aggregates.  The most widely used artificial aggregates are (i) clean broken bricks (ii) blast furnace slag.  The crushing strength of brick shall not be less than 30 to 35 MPa.

134. Classification of Aggregate Based on Size Fine Aggregate  It is the aggregate, most of which passes through a 4.75mm IS sieve.  The lowest size of sand is about 0.07 mm.  The fine aggregate may be natural sand, crushed stone sand or crushed gravel sand.  According to IS 383-1970, there are 4 grading zones of the fine sand, grade 1, grade 2, grade3 and grade 4.

135. Coarse Aggregate  The aggregates, most of which are retained on 4.75mm IS sieve are termed as coarse aggregates.  The coarse aggregates may be  Crushed stone  Uncrushed gravel  Partially crushed stone or gravel.

136.  Sometimes combined aggregates are available in nature consisting of different fractions of fine and coarse aggregates, which are known as all in aggregate.  The all in aggregates are not generally used for making high quality concrete.

137. Classification of Aggregates according to Shape Rounded Aggregate  The aggregate with rounded particles (river or sea shore gravel) has minimum voids ranging from 32 to 33%.  It gives minimum ratio of surface area to the volume, thus requiring minimum cement paste to make good concrete.

138.  The only disadvantage is that the interlocking between its particles is less, and hence the development of the bond is poor, making it unsuitable for high strength concrete and pavement.

140. Irregular aggregates  The aggregate having partly round particles (pit sand and gravel) has higher percentage of voids ranging from 35 to 38 %.  It requires more paste for a given workability.  The interlocking between particles, though better than that obtained with the rounded aggregate, is inadequate for high strength concrete.

142. Angular aggregates  The aggregate with sharp angular and rough particles (crushed rock) has a maximum percentage of voids ranging from 38 to 40%.  The interlocking between particles is good, providing a good bond.  The aggregate requires more paste to make workable concrete of high strength.  The angular aggregate is suitable for high strength concrete and pavements subjected to tension.

144. Flaky and elongated aggregates  An aggregate is termed flaky when its least dimension (thickness) is less than three-fifth of its mean dimension.  The particle is said to be elongated when its greatest dimension (length) is more than nine- fifth (1.8 times) of its mean dimension.

146. Classification based on Unit Weight Normal Weight Aggregate  The commonly used aggregates i.e. sand, gravel, crushed rocks such as granite, basalt, sandstone (sedimentary) and limestone which have specific gravities between 2.5 and 2.7 produce concrete with unit weight ranging from 23 to 26 kN/m 3 and crushing strength at 28 days between 15 to 40 MPa are termed Normal weight aggregate.

147. Heavy Weight Aggregate (High Density aggregate) Heavy weight aggregates are  Baryte(G s = 4 to 4.6)  Ferrophosphorus (G s = 5.8 to 6.8)  Haematite (G s = 4.9 to 5.3)  Magnetite (G s = 4.2 to 5.2)

148. Scrap Iron and Iron Shots (G s = 6.2 to 7.8)  Heavy weight cocnrete is produced from heavy weight aggregate, which is more effective as a radiation shield.  The unit weight of concrete varies from 30 to 57 kN /m 3.

149. Light weight Aggregate  The light weight aggregates have unit weight upto 12 kN/m 3.  These aggregates are obtained from pumice, volcanic cinder, Diatomite, blast furnace slag, fly ash etc,.  The weight of concrete (structure) is reduced to a great extent and it provides better thermal insulation and improved fire resistance.

150. Fineness Modulus  The fineness modulus is a numerical index of fineness, giving some idea of the mean size of the particles present in the entire body of the aggregate.  The fineness modulus is the sum of the cumulative percentages retained on the sieves divided by 100.

151.  According to IS 2386-1963, the sieves that are to be used for the sieve analysis of the aggregate for concrete are 80mm, 40mm, 20mm, 10mm, 4.75mm, 2.36mm, 1.18mm, 600 , 300  and 150   The fineness modulus can be regarded as a weighted average size of a sieve on which material is retained.

152.  For example, a fineness modulus of 6 can be interpreted to mean that the sixth sieve, i.e. 4.75 mm is the average size.  The value of fineness modulus is higher for coarser aggregate.  The fineness modulus for fine sand varies between 2 and 3.5, for coarse aggregate it varies between 5.5 and 8, for all in aggregate it varies from 3.5 to 6.5.

153.  Any sand having FM more than 3.2 will not be suitable for making satisfactory concrete.  The object (purpose) of finding FM is to grade the given aggregates for the most economical mix for the required strength and workability with minimum quantity of cement.  If the test aggregates gives higher FM, the mix will be harsh and if on the other hand gives a lower FM, it produces an uneconomical mix.

154.  Gradation  Gradation refers to the particle size distribution of aggregates.  The gradation of coarse aggregate plays an important role in workability and paste requirements.  The gradation of fine aggregate affects the workability and finishability of concrete.

155.  Types of gradation  Uniform grading  All particles are of same size.  It produces a large volume of voids irrespective of particle size.  Hence the paste requirement for this concrete is high.

156.  Continuous grading  Incorporates a combination of particles of many sizes.  Hence, it minimises the volume of voids but increases the particle surface area.  This is the preferred gradation.

157.  Gap gradation  This involves grading in which one or more sizes are omitted. This type of concrete is generally for architectural or aesthetic purposes.

159.  Water