Concrete Technology Lab Manual - PDF

NATIONAL INSTITUTE OF TECHNOLOGY WARANGAL DEPARTMENT OF CIVIL ENGINEERING CONCRETE TECHNOLOGY LAB MANUAL II B.Tech. I Semester CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL...

NATIONAL INSTITUTE OF TECHNOLOGY WARANGAL DEPARTMENT OF CIVIL ENGINEERING CONCRETE TECHNOLOGY LAB MANUAL II B.Tech. I Semester CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 1  EXPERIMENT NO: 1 (a) FINENESS OF CEMENT BY DRY SIEVING OBJECT: To determine fineness of given cement by dry sieving THEORY: The fineness of cement has an important bearing on the rate of hydration and hence on the rate of gain of strength and also on the rate of evolution of heat. Finer cement offers a greater surface area for hydration and hence faster the development of strength. The fineness of grinding has increased over the years. But now it has got nearly stabilized. Different cements are ground to different fineness. The particle size fraction below 3 microns has been found to have the predominant effect on the strength at one day while 3 - 25-micron fraction has a major influence on the 28 days strength. Increase in fineness of cement is also found to increase the drying shrinkage of concrete. Fineness of cement is tested in two ways: (a) By sieving (b) By determination of specific surface (total surface area of all the particles in one gram of cement) by air-permeability apparatus and is expressed as cm2/g or m2/kg. Generally Blaine Air permeability apparatus is used. APPARATUS: Test Sieve 90 microns, Balance, Gauging Trowel, Brush. PROCEDURE: 1. Fit the tray under the sieve, weigh approximately 10 g of cement to the nearest 0.01 g and place it on the sieve carefully to avoid loss. Fit the lid over the sieve and agitate until most of the material passes through it. 2. Remove and weigh the residue. Express its mass as a percentage, R 1, of the quantity first placed in the sieve to the nearest 0.1 percent. Gently brush all the fine material off the base of the sieve into the tray. 3. Repeat the whole procedure using a fresh 10 g sample to obtain R 2. Then calculate the residue of the cement R as the mean of R1, and R2, as a percentage, expressed to the nearest 0.1 percent. 4. When the results differ by more than 1 percent absolute, carry out a third sieving and calculate the mean of the three values. RESULT: The fineness of given sample of Cement is _________ % REFERRED INDIAN STANDARD CODES: 1. IS 4031 (Part I): 1996 (Reaffirmed 2005) - Indian Standard Method of Physical Tests for Hydraulic Cement – Determination of fineness by dry sieving. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 2  EXPERIMENT NO: 1(b) SPECIFIC GRAVITY OF CEMENT OBJECT: To determine specific gravity of cement THEORY: Specific gravity of cement is normally defined as the ratio between the weight of a given volume of material and weight of a equal volume of water.the one method of determining the specific gravity of cement is by the use of a liquid such as water-free kerosene which does not react with cement. For an Ordinary Portland Cement the specific gravity is 3.15. APPARATUS: Physical balance, specific gravity bottle, kerosene PROCEDURE: 1. Weigh the specific gravity of dry bottle (W1) 2. Fill the bottle with distilled water and weigh the bottle filled with water, (W 2) 3. Wipe dry the specific gravity bottle and fill it with kerosene weight (W3) 4. Pour some of the kerosene out and introduce a weighted quantity of 10 grams of cement into the bottle. 5. Roll the bottle gently in inclined position until no further air bubble rises to surface. Fill the bottle to the top with kerosene and weigh it (W4). OBSERVATIONS AND CALCULATIONS: Sl. No Description Trial – 1 Trail – 2 Trial - 3 1. Wt. of empty bottle (W1) 2. Wt. of bottle + Water (W2) 3. Wt. of bottle + Kerosene (W3) 4. Wt. of bottle + Kerosene + Cement (W4) 5. Wt. of Cement (W5) 6. Specific Gravity of Kerosene 7. Specific Gravity of Cement W3 − W1 Specific Gravity of Kerosene = Sk = W2 − W1 W5  S k Specific Gravity of Cement = Sc = W5 + W3 − W4 RESULT: The Specific Gravity of Cement is _________________ CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 3 PRECAUTIONS: 1 The kerosene used should be free from water. 2 While introducing cement, care should be taken to avoid splashing and cement should not adhere to the inside of the flask above the liquid. REFERED INDIAN STANDARD CODES: 1. IS 2720 Part -3 –1980 (Reaffirmed 2002) Methods of tests for soil – Determination of Specific gravity CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 4  EXPERIMENT No - 2 CONSISTENCY OF STANDARD CEMENT PASTE OBJECT: This method of test covers the procedure for determining the quantity of water required to produce a cement paste of standard consistency. THEORY: The object of conducting this test is to find out the amount of water to be added to the cement to get a paste of normal consistency i.e. a paste of certain standard solidity which is used to fix the quantity of water to be added in cement before performing test for compressive strength, setting time and soundness. APPARATUS: Vicat apparatus with Vicat plunger, mould, gauging trowel, 100ml-measuring jar, weighing balance, stopwatch, china dish. DESCRIPTION OF APPARATUS: The Vicat apparatus consists of a frame bearing a movable rod with, at one end, the cap and at the other, one of the following, which is removable. The needle for determining the initial setting time (1mm square in section or of 1.13mm diameter), the needle for determining final setting time (which has the same shape and section of initial setting needle but shall be fitted with a metal attachment hollowed out so as to leave a circular cutting edge 5mm this edge), or the plunger shall be of polished brass 10mm in diameter for determining the normal consistency. The movable rod carries an indicator, which moves over a graduated scale. With all attachments the cap and rod with initial setting, needle or final setting needle or plunger shall together weight 300gms. The mould for cement consists of a split ring of 80mm in diameter 40mm in height, which rests on a non-porous plate. PROCEDURE: The consistency of standard cement paste is defined as that consistency which will permit the Vicat plunger to penetrate to a point 5 to 7mm from the bottom of the Vicat mould when the cement paste is tested as follows: 1. For preparing one mould take 400 gms of cement and prepare a paste of cement with a weighted (measured) quantity of water, taking care that the time of gauging is not less than 3min, nor more than 5min, and the gauging shall be completed before any signs of setting occur. The gauging time shall be counted from the time of adding water to the dry cement until commencing to fill the mould. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 5  2. Fill the vicat mould with this pate resting on a non-porous pate. After completely filling the mould, smooth off the top of the mould. The mould may be slightly shaken to expel the air. 3. Place the test block in the mould together with the non-porous resting plate, under the rod bearing the plunger, lower the plunger gently to touch the surface of the rest block, and quickly release, allowing it to sink into the paste. This operation shall be carried out immediately after filling the mould. 4. Prepare trail test pastes with varying percentages of water (26,28,30,33%) and test until the amount of water necessary for making up the standard consistency as defined is found. Express the amount of water as a percentage by weight of the dry cement. OBSERVATIONS AND CALCULATIONS: Sl. % Water Volume of water Gauging time Reading of Vicat’s No. added (ml) (Sec) Apparatus RESULT: The Consistency of standard cement paste is ______________ PRECAUTIONS: 1. From the instant of adding water into the cement, it should be thoroughly mixed. 2. The consistency plunger should be released immediately on the paste with out pressure and jerk after the rod is brought down to touch the surface of the test block. 3. For each repetition of the experiment fresh cement is to be taken. 4. Plunger should cleaned during every repetition and make sure that it moves freely. REFERED INDIAN STANDARD CODES: 1. IS 4031 (Part – 4) – 1988 (Reaffirmed 1995) – Methods of Physical tests for Hydraulic Cement – Determination of Consistency of Standard Cement Paste. 2. IS 5513– 1996 (Reaffirmed 2005) – Specifications for Vicat’s Apparatus. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 6  EXPERIMENT No – 3 INITIAL AND FINAL SETTING TIME OF CEMENT OBJECT: This method of test covers the procedure for determining the initial and final setting time of cement. THEORY: In order that the concrete may be placed in position conveniently, it is necessary that initial setting time of cement is not too quick (i.e., not less than 30 minutes). Once the concrete is transported, placed, compacted and finished, it shall set early; it is necessary that the final setting time shall not be too late (i.e., not more than 600 minutes). APPARATUS: Vicat apparatus with initial and final setting needles, measuring jar of 100 cc, stopwatch, china dish, trowels. PROCEDURE: 1. Take 400 gm. of cement. 2. Prepare a neat cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consistency (i.e., 0.85P) 3. Start a stopwatch at the instant when water is added to the cement. 4. Fill the vicat mould with cement paste gauged as above, the mould resting on a nonporous plate. 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 in the mould is the test block. PART A - DETERMINATION OF INITIAL SETTING TIME: 1. Place the block confined in the mould and resting on the non-porous plate under the vicat rod bearing initial setting needle. 2. Lower the setting needle gently in contact with the surface of the test block and quickly release allowing it to penetrate into test block. 3. In the beginning the needle will completely pierce the test block. Repeat this procedure until the needle, when brought in contact with the test block and released as described above, fails to pierce the block for about 5mm measured from the bottom of the mould. 4. The period elapsing between the time when water is added to the cement and the time at which the needle fails to pierce the test block by about 5mm shall be the initial setting time. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 7 OBSERVATIONS AND CALCULATIONS: Time %of water Volume of Reading on Vicat Total time (min) added water (cc) apparatus (mm) taken (min) 0 0.85 P RESULT: The Initial Setting Time of given sample of Cement is ____________ PART B - DETERMINATION OF FINAL SETTING TIME: 1. Replace the initial setting needle of the Vicat apparatus by the needle with an annular attachment. 2. The cement shall be considered as finally set, when upon applying the needle gently to the surface of the test block, the needle makes an impression there on, while the annular attachment fails to do so. RESULT: The Final Setting Time of given sample of Cement is ____________ REFERED INDIAN STANDARD CODES: 3. IS 4031 (Part – 5) – 1988 (Reaffirmed 2000)– Methods of Physical tests for Hydraulic Cement – Determination of Initial and Final Setting times. 4. IS 5513– 1996 (Reaffirmed 2005) – Specifications for Vicat’s Apparatus. 5. IS 269 – 2013 – Ordinary Portland Cement, 33 Grade – Specification 6. IS 8112 – 2013 – 43 Grade Ordinary Portland Cement – Specification 7. IS 12269 – 2013 – Specifications for 53 Grade Ordinary Portland Cement CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 8  EXPERIMENT NO: 4 COMPRESSIVE STRENGTH OF CEMENT OBJECT: To determine the compressive strength of a given sample of cement APPARATUS: Vibration Machine, Poking Rod, Cube Mould of 70.6 mm side (50 sq.cm), Balance, Gauging Trowel, Stop Watch, Graduated Glass Cylinders. THEORY: The compressive strength of hardened cement is the most important of all the properties. Therefore, it is not surprising that the cement is always tested for its strength based on cement mortar in the laboratory before the cement is used in important works. Strength tests are not made on neat cement paste because of difficulties of excessive shrinkage and subsequent cracking of neat cement. PROCEDURE: 1. Preparation of test specimens - Clean appliances shall be used for mixing and the temperature of water and that of the test room at the time when the above operations are being performed shall be 27 ± 2°C. Potable/distilled water shall be used in preparing the cubes. 2. The material for each cube shall be mixed separately and the quantity of cement, standard sand and water shall be as follows: Cement 200 g and Standard Sand 600 g, Water (P/4 + 3) percent of combined mass of cement and sand, where P is the percentage of water required to produce a paste of standard consistency determined as described in IS : 4031 (Part 4)-1988. 3. Place on a nonporous plate, a mixture of cement and standard sand. Mix it dry with a trowel for one minute and then with water until the mixture is of uniform colour. The quantity of water to be used shall be as specified in step 2. The time of mixing shall in any event be not less than 3 min and should the time taken to obtain a uniform colour exceed 4 min, the mixture shall be rejected and the operation repeated with a fresh quantity of cement, sand and water. 4. Moulding Specimens - In assembling the moulds ready for use, treat the interior faces of the mould with a thin coating of mould oil. 5. Place the assembled mould on the table of the vibration machine and hold it firmly in position by means of a suitable clamp. 6. Immediately after mixing the mortar in accordance with steps 1 & 2, place the mortar in the cube mould and prod with the rod. Place the mortar in the hopper of the cube mould and prod again as specified for the first layer and then compact the mortar by vibration. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 9  7. The period of vibration shall be two minutes at the specified speed of 12000 ± 400 vibration per minute. 8. At the end of vibration, remove the mould together with the base plate from the machine and finish the top surface of the cube in the mould by smoothening the surface with the blade of a trowel. 9. Curing Specimens - keep the filled moulds in moist closet or moist room for 24 ± 1 hour after completion of vibration. At the end of that period, remove them from the moulds and immediately submerge in clean fresh water for curing. 10. The water in which the cubes are submerged shall be renewed every 7 days and shall be maintained at a temperature of 27 ± 2°C. After they have been taken out and until they are broken, the cubes shall not be allowed to become dry. 11. Test three cubes for compressive strength for each period of curing mentioned under the relevant specifications (i.e. 3 days, 7 days, 28 days) 12. The cubes shall be tested on their sides without any packing between the cube and the steel plattens of the testing machine. One of the plattens shall be carried on a base and shall be self-adjusting, and the load shall be steadily and uniformly applied, starting from zero at a rate of 35 N/mm 2 /min. OBSERVATIONS AND CALCULATIONS: S.No. Curing Weight of Load Compressive Average Period cement (kN) Strength Compressive cube (g) (MPa) Strength (MPa) 1 2 7 Days 3 4 28 5 Days 6 The measured compressive strength of the cubes shall be calculated by dividing the maximum load applied to the cubes during the test by the cross-sectional area, calculated from the mean dimensions of the section and shall be expressed to the nearest 0.5 N/mm2. In determining the compressive strength, do not consider specimens that are manifestly faulty, or that give strengths differing by more than 10 percent from the average value of all the test specimens. RESULT: 1. The average 7 Days Compressive Strength of given cement sample is ____ 2. The average 28 Days Compressive Strength of given cement sample is …..….. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 10 REFERRED INDIAN STANDARD CODES: 1. IS 4031 (Part – VI) – 1988 (Reaffirmed 2005) Indian Standard Methods of Physical tests for Hydraulic cement – Compressive Strength of Cement. 2. IS 650 – 1991 ( Reaffirmed 2008) Standard Sand for Testing Cement – Specification 3. IS 12269 – 1987 (Reaffirmed 2004) – Indian Standard Specification for 53 Grade Ordinary Portland Cement CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 11  EXPERIMENT No - 5 SIEVE ANALYSIS OF AGGREGATES OBJECT: To determine fineness modulus and grain size distribution of given (a) Coarse and (b) Fine aggregates. THEORY: Fine aggregate is the sand used in mortars. Coarse aggregate is the broken stone used in concrete. The coarse aggregate, unless mixed with fine aggregate, serves no purpose in concrete works. The size of the fine aggregate is limited to a max of 4.75mm (3/16 in) gauge beyond which if is known as coarse aggregate. Fineness modulus is only a numerical index of fineness, giving some idea of the mean size of particles in the entire body of aggregate. Determination of fineness modulus may be considered as a method of standardization of grading of the aggregates. It is obtained by sieving a known weight of given aggregate in a set of standard sieves and by adding the percentage weight of material retained on all the sieves and dividing the total percentage by 100. The object of finding the fineness modulus is to grade the given aggregate for the most economical mix and workability, with minimum quantity of cement. APPARATUS: Indian standard test sieves (Fine wire cloth) No.480, 240, 120, 60, 30 and 15 and square hole perforated plate 40mm, 20mm, 10mm, weighing balance, trays etc., PROCEDURE: COARSE AGGREGATE: 1. Take 5 kg of coarse aggregate (nominal size 20mm) from a sample of 50 kg quartering. 2. Carry out sieving by hand, shake each sieve in order 40, 20, 10mm and 4.75 mm over a clean dry tray for a period of not less than 2min. the shaking is done with a varied motion backward and forward, left to right, circular, clockwise and anticlockwise and with frequent jarring, so that material is kept moving over the sieve surface in frequently changing directions. 3. Find the weight of aggregate retained on each sieve taken in order. FINE AGGREGATE: 1. Take a 500gms of sand from a laboratory sample of 10 kg by quartering and break clay lumps if any. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 12  2. Arrange the sieves in order of I S sieve 4.75 mm, 2.36 mm, 1.18 mm, 600 , 300 and 150 at the bottom. 3. Keep the sand sample in the top sieve (4.75 mm) carry out the sieving in the set of sieves as arranged before for not less than 10mins. 4. Find the weight retained on each sieve. OBSERVATIONS AND CALCULATIONS (For Coarse & Fine Aggregate): Width of aperture Wt. Retained % wt retained Cumulative % passing % wt retained 40 mm 20 mm 10 mm 4.75 mm 2.36 mm 1.18 mm 600  300  150  PAN Fineness modulus = C * 100 Note: * Sum of the Cumulative percentage of weight retained PRECAUTIONS: 1. The sample should be taken by quartering. 2. The sieving must be done carefully to prevent spilling the aggregate. REFERED INDIAN STANDARD CODES: 1. IS 460 Part 1- 1985 (Reaffirmed 1998) Specification for Test Sieves 2. IS 2386 (Part – I) – 1963 (Reaffirmed 2003) – Methods of test for aggregate for concrete – Particle size and shape 3. IS 383 – 1970 (Reaffirmed 2002) – Specifications for coarse and fine aggregate from natural sources for concrete CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 13  EXPERIMENT No - 6 BULK DENSITY, SPECIFIC GRAVITY, VOID RATIO & POROSITY OF AGGREGATES OBJECT: Determination of the Bulk density, Specific gravity, Porosity, Percentage of voids and void ratio of coarse and fine aggregates. THEORY: 1. BULK DENSITY: The bulk density of an aggregate is used for judging its quality by comparison with normal density for that type of aggregate; it is required for converting proportions by weight into proportions by volume and is used in calculating the percentage of voids in the aggregate. For designing the concrete mix, information on specific gravity of aggregates are necessary. It gives valuable information on the quality and properties of aggregates. 2. SPECIFIC GRAVITY: The specific gravity of an aggregate is generally required for calculations in connection with cement concrete design work for determination of moisture content and for the calculations of volume yield of concrete. The specific gravity also gives information on the quality and properties of aggregates. 1. Bulk density of unit weight is the weight of material per unit volume 2. Percentage of voids or porosity is the volume of voids to the total volume of a sample of an aggregate. 3. Void ratio is the ratio of volume of voids to the volume of solids in an aggregate. 4. Specific gravity is the weight of aggregate relative to the weight of equal volume of water. APPARATUS: 10 Kg. capacity balance with weights, cylindrical containers 1 ltr and 5 ltrs capacities, measuring jar of 1000 cc capacity, pycnometer. PROCEDURE (For Coarse and Fine Aggregate): 1. Weigh the dry empty container of 5 ltr capacity (W1) 2. Fill the container to the top level by coarse aggregate by discharging from a height not exceeding 5 cm above the top of the container (W2) 3. Pour water slowly into the container just to fill the voids completely in the aggregate and weigh it (W3) 4. Empty the container, clean it and fill with water and weigh it (W4) CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 14 OBSERVATIONS AND CALCULATIONS: Sl. No. Description Trial – 1 Trial – 2 Trial - 3 1. Wt of empty container ( W1) 2. Wt of container with material ( W2 ) 3. Wt of container + material + water (W3) 4. Wt of container + water (W4) 5. W 2 − W1 Bulk Density = = gm/cc W 4 − W1 6. Percentage of voids (Porosity) W3 −W 2 =  100 W 4 − W1 7. W3 −W 2 Void Ratio = (W 4 − W 1) − (W 3 − W 2) 8. W 2 − W1 Specific Gravity = (W 4 − W 1) − (W 3 − W 2) Volume of Voids Note: 1. Percentage of Voids or Porosity =  100 Volume of Voids + Volume of Soilds Volume of Voids 2. Void Ratio = Volume of Solids SPECIFIC GRAVITY OF FINE AGGREGATE USING PYCNOMETER: PROCEDURE: 1. Take a clean and dry empty pycnometer and weigh (G1). 2. Fill it full with clean water and weigh (G2). 3. Fill 1000 grams of dry sand into pycnometer and fill it with clean water (while filling with water, keep the pycnometer inclined and roll it on the table to expel the air bubbles and weigh it (G3). 1000 Specific Gravity of Fine Aggregate = (G 2 − G1) − (G3 − G1 − 1000) REFERED INDIAN STANDARD CODES: 4. IS 2386 (Part – III) – 1963 (Reaffirmed 2002) Methods of test for aggregate for concrete – Specific Gravity, Density, Voids, Absorption and Bulking. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 15  EXPERIMENT No - 7 WORKABILITY OF CEMENT CONCRETE MIX OBJECT: To determine the workability of the given concrete mix by (i) Slump Test, (ii) Compaction Factor and (iii) Vee-Bee Consistometer. APPARATUS: Iron pan to mix concrete, weighing machine, 30 cm scale, tamping rod ( 16mm dia, 0.6 m long ), slump test apparatus, compaction factor apparatus, vee-bee consistometer. PREPARATION OF CONCRETE MIX: A concrete mix of 1:2:4 with a w/c = 0.5 and 0.7 are prepared first to find its workability as follows: 1. Take 2.5 kg of cement, 5 kg of sand, 10 kg of coarse aggregate 2. Take water of weight 0.5 x 2.5 = 1.25 kg. 3. Mix the dry constituents thoroughly to get a uniform colour and then add water. Given concrete mix is prepared first and then its workability is determined by various methods as follows. 1.SLUMP TEST: THEORY: Unsupported concrete when it is fresh will flow to the sides and a sinking in height will take place. This vertical settlement is known as slump and in this test fresh concrete is filled into a mould of specific shape and dimensions and measure the settlement or slump when supporting mould is removed, slump increases with water cement ratio. For different works different slump values have been fixed. Slump is a measure of indicating the consistency or workability of cement concrete and also slump gives an idea of water cement ratio needed for concrete to be used for different works. A concrete is said to be workable if it can be easily mixed and easily placed, compacted and easily finished. PROCEDURE: 1. Place the mixed concrete in the cleaned slump cone in 3 layers, each approximately 1/3 of the height of the mould. 2. Strike off the top with a trowel or tamping rod so that the mould is exactly filled. 3. Remove the cone immediately, raising it slowly and carefully in the vertical direction. 4. Measure the subsidence of concrete in centimeters, which will give the slump. 2.COMPACTION FACTOR TEST: THEORY: Compaction factor test is adopted to determine the workability of concrete, where nominal size of the aggregate does not exceed 40 mm. It is based upon the definition that workability is that property of the concrete, which determines the amount of work required to produce full compaction. This test consists essentially of applying a standard amount of work to standard quantity of concrete and measuring the resulting compaction. The test is carried as per specifications of IS 1199-1959 to find the workability of freshly prepared concrete. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 16 Workability gives an idea of the capability of being worked that is idea to control the quantity of water in cement concrete mix to get uniform strength. PROCEDURE: 1. Fasten the hopper doors of the compaction factor apparatus. 2. Weigh the empty cylinder accurately and note down the weight (W1 ) 3. Fill the freshly mixed concrete in the upper hopper gently and carefully with hand scoop without compaction. 4. After two minutes release the trap door so that the concrete may fall into the lower hopper bringing the concrete into standard compaction. 5. Immediately after the concrete has come to rest, open the trap door of the lower hopper and allow the concrete to fall into the cylinder bringing the concrete into standard compaction. 6. Remove the excess of concrete above the top of the cylinder and clean the cylinder from all sides and take the weight of the partially compacted concrete thus filled a cylinder (W2 ) 7. Refill the cylinder with a same sample of concrete in approximately 5 cm layers with a tamping rod (or vibrating each layer heavily so as to expel all the air and to obtain full compaction of concrete). Level up the concrete surface and take its weight of the cylinder with the compacted concrete (W3). Wt. of Partially Compacted Concrete W2 − W1 8. Compaction factor = = Wt. of Fully Compacted Concrete W3 − W1 3.VEE-BEE CONSISTOMETER TEST: THEORY: The Vee-Bee consistometer will be used to determine the time required for transforming by vibration, a concrete specimen in the shape of a conical frustum into a cylinder. PROCEDURE: 1. Fill up the cone in the sheet metal cylindrical pot of the consistometer with the required concrete mix. 2. Lift the cone and place the disc attached to the swivel arm just on the top of the concrete, which is in the shape of a conical frustum. 3. Start the electrically operated vibrator and allow the concrete to spread out in the cylindrical pot. 4. Continue the vibration until the whole surface uniformly adheres to the bottom of the disc. Note the time taken with a stopwatch in seconds. 5. The consistency of the concrete shall be expressed in V-B degrees, which are equal to the time in seconds. REFERED INDIAN STANDARD CODES: 1. IS 1199 - 1959 Methods of sampling and analysis of concrete’ (Reaffirmed 2004) CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 17  EXPERIMENT No – 8 TESTS ON HARDENED CONCRETE OBJECT: To find the Tensile Strength of Concrete by Conducting a Split Test on a standard cylinder, Modulus of Rupture and Compressive Strength of concrete. APPARATUS: Scale, Tinius Olsen Testing Machine. PROCEDURE: TO DETERMINE THE TENSILE STRENGTH OF CONCRETE BY SPLIT TEST: This test is to be done on a standard 150 mm diameter, 300 mm high cylinder, which is, loaded in compression along two axial lines 180 degrees apart. Narrow strips of plywood are used as cushioning material along the load lines. 2P The splitting tensile strength = DL Where, P = Maximum applied load; L = length of the cylinder; D = Diameter of cylinder FLEXURAL TEST ON CONCRETE BEAM TO GET MODULUS OF RUPTURE: This test is done on standard prism of dimensions 100 mm  100 mm  400 mm. The test specimen is subjected to third point loading. The test specimen should be turned on its side with respect to its position as molded and centered on bearing blocks. The load applying blocks shall be brought in contact with the upper surface at the third points between the supports. The strength in bending is the extreme fiber stress on the tensile side at the point of failure. WL a) If failure occurs with in middle third of the span then f = 2 bd 3Wa b) If failure occurs outside the middle of span f = bd 2 c) If failure occurs outside the middle third by more than 5% of span, the results shall be disregarded. Where, f = modulus of rupture; W = load applied; b = width of the beam L = effective span; d = depth of the beam; a = distance from fiber point to the nearest support measured along the center line of the tensile failure CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 18 TO DETERMINE THE COMPRESSIVE STRENGTH OF C.C. CUBES: The compressive strength of concrete is found by testing standard cube of dimensions 150  150  150 mm under axial compression. The cube must be placed in the testing machine so that the load is applied to the opposite sides as cast and not on to the top and bottom as cast. The specimen must be accurately placed so that it is truly concentrated with the spherical seat of the upper platen. Determine the average load of three specimens. Calculate the compressive stress. 𝑃 The compressive strength = 𝐴 Where, P = Maximum applied load, A = cross sectional area of specimen REFERED INDIAN STANDARD CODES: 1. IS: 516-1959 ‘Methods of Tests for strength of concrete’ (Reaffirmed 2004) 2. IS: 5816 – 1999 ‘Splitting Tensile Strength of Concrete – Method of test. (Reaffirmed 2004) CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 19 CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 20  EXPERIMENT NO: 9 MODULUS OF ELASTICITY OF CONCRETE OBJECT: To draw a stress-strain curve for cement concrete by testing standard concrete cylinder and find the E of concrete. APPARATUS: Scale, Compressometer (or extensometer), Tinius Oslen Testing Machine THEORY: The typical stress strain curve of concrete at a certain speed of loading is shown in the following fig.1. The maximum stress corresponding to point Z on the curve (at a strain of 0.2% nearly). The actual collapse occurs when the concrete attains an ultimate strain of about 0.4%. It will be seen that the curve is not a straight line even at lower stresses and so the value of Young’s modulus E which gives the rate of increase of stress with strain, changing from point to point. The slope of the line OA is called as the secant modulus. The slope of the Es = Secant modulus line, which is drawn tangential at any Eo = Initial tangent modulus Et = Tangent modulus point B on the curve, is called as the tangent modulus. The slope of the line tangential at the initial point of the curve is called as the initial tangent modulus. It is the secant modulus that Fig 1:analysis. is used in case of reinforced concrete structural Stress strain curve for concrete PROCEDURE: 1. The three test specimens for compressive strength shall first be test in accordance with code and the average compressive strength shall be recorded. Immediately on removing the cylinder or prism from the water and while it is still in a wet condition, the extensometers shall be attached at the ends, or on opposite sides of the specimen and parallel to its axis, in such a way that the gauge points are symmetrical about the center of the specimen and in no case are nearer to either end of the specimen than a distance equal to half the diameter or half the width of the specimen. 2. The load shall be applied continuously and without shock at the rate of 140 kg/ cm2/ min., until an average stress of (C + 5) kg/cm 2 is reached, where C is 1/3rd of the average compressive strength of the cubes calculated to the nearest 5 kg/ cm2. The load shall be maintained at this stress for at least 1 minute and shall then be reduced gradually to an average stress of 1.5 kg/ cm 2 when extensometer readings shall be taken. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 21 3. The load shall be applied a second time at the same rate until an average stress of (C+1.5) kg/ cm2 is reached. The load shall be maintained at this figure while extensometer readings are taken. The load shall again be reduced gradually and readings again taken at 1.5 kg/ cm2. 4. The load shall then be applied a third time and extensometer readings taken at 10 approximately equal increment of stress up to an average stress of (C+1.5) kg/ cm2. Readings shall be taken at each stage of loading with as little delay as possible. 5. If the overall strains observed on the second and third readings differ by more than 5%, the loading cycle shall be repeated until the difference in strain between consecutive readings at (C+1.5) kg/ cm2 does not exceed 5%. CALCULATIONS: 1. The strains at the various loads in the last two cycles shall be calculated separately for each extensometer and the results shall be plotted graphically against the stress. 2. Straight lines shall be drawn through the points for each extensometers; the slopes of these two lines shall be determined and from them the average value shall be found if the difference between the individual values is less the 15% of the average value, expressed in kg/ cm2 to the nearest 100 kg/ cm2 shall be recorded as the modulus of elasticity of the concrete. 3. If the difference is greater than 15%, the specimen shall be centered in the testing machine and the test is repeated. OBSERVATIONS & CALCULATIONS: Cross sectional area of the specimen = (  152)/4 = 176.71 sq. cm. If the value of C is assumed as 50 kg/ cm 2, the load corresponding to different load levels is calculated in the following table Load Corresponding to Load (kg) Load (lb) C + 5 = 55 9719.3 21431 1.5 265.07 585 C + 1.5 = 51.5 9100.8 20067 140 24740 54552 a. Least count of loading machine: b. Least count of Compressometer: c. Gauge length: CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 22  Table I Test cycle Compressometer Reading no. Beginning of the cycle End of the Cycle 1st cycle 2nd cycle 3rd cycle Table II Readings taken during the 3rd cycle of loading Load Sl. no. Compressometer reading lbs. kg 1. REFERRED INDIAN STANDARD CODES: 1. IS: 516-1959 (Reaffirmed 2004) Indian Standard Methods of Tests for Strength of concrete. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 23  EXPERIMENT NO: 10 NON DESTRUCTIVE TEST OF CONCRETE OBJECT: To determine the non destructive evaluation of concrete with i) Rebound Hammer ii) Ultrasonic Pulse Velocity (UPV) APPARATUS: Schmidt Rebound Hammer, Ultrasonic Pulse Velocity (UPV) SCHMIDT REBOUND HAMMER (IS 13311 Part II – 1992) The Schmidt hammer is a spring-operated hammer assembly used in estimating the near-surface strength of concrete members. The body of the gauge includes a spring-driven hammer which, upon impact, rebounds and moves a slide indicator making a record of the rebound distance. Fig 1 shows the operation of Rebound hammer and Fig 2 depicts a commercially available Schmidt hammer. The rebound number ranges from0 to 100 and may be correlated to apparent near-surface strength. Various correlation charts are provided that take the orientation of the hammer into account. The method is a good first indicator, but is subject to variables such as presence of a surface hardener, machine/hard troweled finishes, finished versus formed surface, presence of delaminations, carbonation of the surface, and moisture content, just to name a few. In summary, the Schmidt hammer is a good first indicator of near-surface concrete. It is ideal as an initial scan tool; however, an engineering assessment rarely relies on Schmidt hammer values alone and generally involves verification of in-situ strength by way of core strengths. The results are significantly affected by the following factors: 1. Mix characteristics: a. Cement type, b. Cement Content, c. Coarse aggregate type: 2. Angle of Inclination of direction of hammer with reference to horizontal (Figure 3) 3. Member Characteristics, a. Mass, b. Compaction, c. Surface type, d. Age, rate of hardening and curing type, e. Surface carbonation, f. Moisture Condition, g. Stress state and temperature. Since each of these may affect the readings obtained, any attempts to compare or estimate concrete strength will be valid only if they are all standardized for the concrete under test and for the calibration specimens. CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 24  Fig 1 Schematic diagram of operation of the rebound hammer Fig 2 Schmidt Hammer Fig 3 Cube Compressive strength is N/mm2 plotted against the rebound number CONCRETE TECHNOLOGY LABORATORY, CED, N I T WARANGAL 25 a) Strength Assessment This test is conducted to assess the relative strength of concrete based on the hardness at or near its exposed surface. Carrying of periodic calibration of rebound hammer using standard anvil is desirable. However for new concrete construction, rebound hammer is calibrated on concrete test cubes for a given source of constituent materials(viz. cement, sand and stone aggregate), this calibration data can be used with reasonable accuracy in arriving at equivalent in-situ cube strength of relatively new concrete ( i.e. not more than three months old concrete). This calibration exercise may be carried out in a concrete lab by casting cubes of designed mix and testing these under controlled condition with rebound hammer as well as test to destruction in compression. Calibration graphs then can be drawn. Large number of readings is desirable to reduce the effects of variability in readings due to various localized as well as instrument factors. This method may give highly erroneous results for concrete whose surface is exposed to atmosphere for longer periods say more than three months. This is due to hardening of concrete surface due to carbonation, which may cause overestimation as much as50% for old structure. Hence Strength assessment by Rebound Hammer Test should generally be restricted to relatively new structures only. b) Survey of Weak & delaminating Concrete As the test requires a flat surface and large number of readings to reduce variability, this test is not generally suitable for use on spalled concrete surfaces of distressed structures. However, comparison of Rebound numbers, which indicate the near surface hardness of the concrete, will help to identify relative surface weaknesses in cover concrete and also can be used to determine the relative compressive strength of concrete. Locations possessing very low rebound numbers will be identified as weak surface concrete and such locations will be identified for further investigations like corrosion distress, fire damage and/or any other reason including original construction defects of concrete. This survey is to be carried out on each identified member in a systematic way by dividing the member into well-defined grid points. The grid matrix should have a spacing of approximately 300mmx 300mm. Table 1 gives guidelines for qualitative interpretation of rebound hammer test results with reference to quality. Table 1: Quality of Concrete from Rebound Values Comparative Hardness Average Rebound Quality of Concrete >40 Very Good 30-40 Good 20-30 Fair