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MALLA REDDY ENGINEERING COLLEGE

DEPARTMENT OF CIVIL ENGINEERING

CONCRETE AND HIGHWAY ENGINEERING LAB MANUAL

Maisammaguda, Dhulapally, (Post.Via) Hakimpet, SECUNDERABAD – 500 014 e-mail: mreccivil@yahoo.com

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JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

IV YEAR B.TECH. C.E. I-SEM T P C 0 3 2

CONCRETE AND HIGHWAY ENGINEERING LAB. I. ROAD AGGREGATES: 1. Aggregate Crushing value 2. Aggregate Impact Test. 3. Specific Gravity and Water Absorption. 4. Attrition Test 5. Abrasion Test. 6. Shape tests II. BITUMINOUS MATERIALS : 1. Penetration Test. 2. Ductility Test. 3. Softening Point Test. 4. Flash and fire point tests. III. CEMENT AND CONCRETES : TESTS ON CEMENTS : 1. Normal Consistency of fineness of cement. 2. Initial setting time and final setting time of cement. 3. Specific gravity and soundness of cement. 4. Compressive strength of cement. 5. Workability test on concrete by compaction factor, slump and Vee-bee. 6. Young’s modulus and compressive strength of concrete. 7. Bulking of sand. 8. Non-Destructive testing on concrete (for demonstration) LIST OF EQUIPMENT: 1. Apparatus for aggregate crushing test. 2. Aggregate Impact testing machine 3. Pycnometers. 4. Los angles Abrasion test machine 5. Deval’s Attrition test machine 6. Length and elongation gauges 7. Bitumen penetration test setup. 8. Bitumen Ductility test setup. 9. Ring and ball apparatus 10. Penskey – Morten’s apparatus 11. Vicat’s apparatus 12. Specific gravity bottle. 13. Lechatlier’s apparatus. 14. Slump and compaction factor setups 15. Longitudinal compresso meter and 16. Rebound hammer, Pulse velocity machine.

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CONCRETE AND HIGHWAY ENGINEERING LAB

LIST OF EXPERIMENTS

I.ROAD AGGREGATES: 1.AGGREGATE IMPACT TEST 2.SPECIFIC GRAVITY &WATER ABSORPTION TEST 3.ABRASION TEST 4.FLAKINESS&ELONGATION TEST II.BITUMINOUS MATERIALS: 1.PENETRATION TEST 2.DUCTILITY TEST III. CEMENT AND CONCRETES: TESTS ON CEMENTS: 1.NORMAL CONSISTENCY OF CEMENT 2.FINENESS OF CEMENT 3.SPECIFIC GRAVITY OF CEMENT 4.SOUNDNESS OF CEMENT 5.COMPRESSIVE STRENGTH OF CEMENT 6.WORKABILITY TEST ON CONCRETE BY SLUMP CONE 7.WORKABILITY TEST ON CONCRETE BY VEE BEE 8.COMPRESSIVE STRENTH OF CONCRETE 9.BULKING OF SAND

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Compressive Strength of Cement

Aim : - To determine the Compressive Strength of Cement Apparatus: - i) Cast Iron mould 70.6mm x 70.6mm x 70.6mm ii) Non –Porous tray iii) Trowel iv) Balance v) 8mm , Steel rod Theory: - The Compressive Strength of hardened cement is the most important of all the properties . Therefore the cement is always tested for its strength at the laboratory before the cement is used in important works .Strength test are not made on neat cement paste of difficulties of excessive shrinkage and subsequent cracking of neat cement .Strength of cement is indirectly found on cement sand mortar in specific proportions . This sand shall conform to IS 650-1991 . Procedure :- Take 600 gms of standard sand , 200 gms of cement in a non-porous tray and mix them with a trowel for one minute , then add water of quantity (P/4 + 3.0) percent of combined weight of cement and sand .Mix the three ingredients thoroughly until the mixture is of uniform colour .The time of mixing should not be less than 3 minutes nor more than 4 minutes .Immediately after mixing the mortar is filled into the a cube mould of size 70.6mm in three layers ,each layer is compacted by 25 blows with 8mm dia rod or on the vibrating equipment for 2 minutes .In the above manner 12 Cubes are casted for testing at different times . Keep the compacted cube in the mould at a temperature of 250 C to 290 C and at least 90 % relative humidity for 24 hours .Where the facility of standard temperature and humidity is not available , the cubes may be kept under wet gunny bag to simulate 90 percent relative humidity .After 24 hours the cubes are removed from the mould and immersed in clean fresh water until taken out for testing . Three cubes are tested for compressive strength at the period 1 day , 3 days , 7 days and 28 days . The periods being considered from the completion of vibration. The compressive Strength shall be average of the three for each period. Observations & Caculations:- Weight of Cement = Weight of Sand = Weight of Cement for 3 moulds = Weight of Sand for 3 moulds = Amount of Water to be added is ( P / 4 + 3 ) % Of weight of cement + weight of Sand = For 3 moulds = ml Result : - Compressive Strength at 1 day : Compressive Strength at 3 day s : Compressive Strength at 7 days : Compressive Strength at 28 days :

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Compressive Strength of cement at 28 days should be more than the respective grade of cement . Frequently asked Questions :-

1) Early Strength of Cement is due to -------------- 2) What Percentage of Cement Strength is obtained for 28 days --------------

3) Define the Characteristic Strength

4) As per IS. Code method of concrete mix design the target strength of concrete is-----

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Normal Consistency of Cement Aim :- To determine the Normal Consistency of Cement Apparatus : - i) Vicat Apparatus ii) Vicat plunger , 10mm dia , 50 mm long iii) Mould , 80 mm dia , 40mm high iv) Glass plate v) Non – Porous tray vi) Spatula vii ) Balance . Theory :- For finding out initial Setting time , Final Setting time , Soundness of cement and strength a parameter Known as Standard consistency or Normal Consistency is used . The Standard Consistency of a cement paste is defined as percentage water will permit a vicat plunger having 10 mm diameter and 50 mm long to penetrate to a depth of 33-35 mm from the top of the mould . Procedure :- Take about 500 gms of Cement and prepare a paste with a weighed quantity of water ( 24 % by weight of cement ) for the first trail in a non porous tray . The paste must be prepared in a standard manner and filled into the vicat mould within 3-5 minutes after completing filling the mould , shake the mould to expel air .A Standard plunger , 10mm diameter , 50mm long is attached and brought down to touch the surface of the paste by its own weight .Take the reading by nothing the depth of penetration of the plunger . Conduct a second trail ( 26 % Percent of water ) and find out the depth of penetration of plunger . Similarly , conduct trials with higher and higher water / cement ratios till such time plunger penetrates for a depth of 33.35 mm from the top . That particular percentage of water which allows the plunger to penetrate only to a depth of 33.35 mm from the top is known as the percentage of water required to produce a cement paste of Standard consistency , denoted as ‘P This test is conducted in a temperature in the rage of 250 c to 290 c and constant humidity ( 90 % ) . Observations & Calculations :-

Percentage of Water Initial Reading Final Reading Depth of Penetration

Graph :- Plot a graph between Penetration in mm on x-axis and percentage of water on y-axis . Determine the Standard Consistency of Cement . Result :- Report the Standard Consistency of Cement as Percentage .

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Frequently asked Questions :-

1) Vicat’s apparatus are used to perform the following tests on cement a) Consistency b) Setting time c) Soundness d) both a & b

2) As per IS.456 -2000 the minimum amount of cement required in Kg per m3 for concrete mix design is --------------

a) 500 b) 300 c) 200 d) 100

3)Write the Properties of Cement 4) Define the Standard Consistency of a Cement

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Soundness of Cement

Aim :- To determine the Soundness of Cement by Le- Chatlier mould Apparatus :- i) A brass Cylinder 3 cm diameter , 3 cm height ii ) Two glass plates iii) Non- Porous enamel tray iv) Spatula v) Heating device vi ) Scale . Theory :- It is very important that the cement after setting shall not undergo any appreciable change of volume . Certain Cements have been found to undergo a large expansion after setting causing disruption of set and hardened mass . This will cause serious difficulties for the durability of Structures when such cement is used . The testing of soundness of cement , to ensure that the cement does not snow any appreciable subsequent expansion is of prime importance . The Unsoundness in cement is due to the presence of excess of time than that could be combined with acidic oxide at the Klin . This is also due to inadequate burning or insufficiency in fineness of grading or through mixing of raw materials . It is also likely that too high a proportion of magnesium Cement or Calcium Sulphate content may cause unsoundness of cement . to prevent flash set , Calcium Sulphate is added to the Clinker at grinding . The quantity of gypsum added will vary from 3 to 5 % depending upon C3 A content . If the addition of gypsum is more than that could be combined with C3 A, excess of gypsum leads to an expansion and consequent disruption of the set cement paste . Unsoundness in cement is due to excess of lime , excess of magnesia or excessive proportion of Sulphates unsoundness does not come to the surface for a considerable period of time . Therefore , accelerated tests are required to detect it . The Le chatlier test detects unsoundness due to free lime only . This method of testing does not indicate the presence and factor effect of excess of magnesia . Indian standard specification stipulates that a cement having a magnesia content of more than 3 percent shall be tested for soundness by Auto clave test .Which is sensitive to both free magnesia and free lime . Unsoundness due to an excess of calcium sulphate is determined by chemical analysis . Procedure :- Take 100 gms of Cement and add 0.78 times the water required for standard consistency ( 0.78 P ) . This cement paste is filled into the mould kept on a glass plate . The mould is covered on the top with another glass plate . The whole assembly is immersed in water at a temperature of 27 0 c – 32 0 c and kept there for 24 hours .

Measure the distance between the indicator points . Submerge the mould again in water . Heat the water and bring the boiling point in about 25-30 minutes and kept it boiling for 3 hours . Remove the mould from water , allow it to cool and measure the distance between the indicator points . The difference between the two readings represents the expansion of cement . This must be less than 10mm for ordinary Portland cement . If this expansion is more than 10 mm , cement is air dried for one week and the test is repeated . After one week the expansion should be less than 5 mm . If the cement fails in both the cases the cement is said to be unsound . Observations & Calculations :- Initial Reading = Final Reading =

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Difference = Final Reading – Initial Reading Result :- Report the expansion of cement and soundness of cement . Frequently asked Questions :-

`1) The Percentage of water added in soundness test of cement is

a) 0.78P b) 0.88P c) 0.78P d) 0.75P

2)Un soundness in Cement is due to the presence of -----------

3). As per IS 456-2000 the min grade of concrete required for plain concrete in Sea water is ----- 4) Cement Concrete has ------------------- a) High Compressive Strength b) High Tensile Strength c) Both a & b d) None

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Fineness Of Cement

Aim:- To determine fineness of cement using IS-Sieve method.

Apparatus:- IS-Sieve no: 9 i.e 90 microns confirming to IS 460-1962.Tray,Balance with 100 gms weighing capacity and a brush.

Theory: -This test is carried out to check the proper grinding of cement. Fineness of cement has an important bearing on the rate of hydration and hence on the rate of gain of strength and also rate of evolution of heat. Finer cement offers greater surface area for hydration and hence faster the development of strength. Different cements are ground to different fineness. The disadvantage of fine grinding is that it is susceptible to air set and early deterioration. Maximum number of particles in a sample of cement should have a size less than 100 microns. The smallest size should have a size about 1.5 microns.

Procedure:-1. 100 gms of cement is weighed and placed in an IS-Sieve no: 9, breaking down any air set lumps by fingers.

2. Holding the sieve with both the hands, sieve it continuously for 5-10 minutes until all the fine material is passing through. While sieving rotate the continuously taking care that the cement does not spill out.

3. Collect the residue on the sieve and weigh it.

Observations &Calculations :-

Weight of cement taken = W1 =

Weight of residue after sieving = W2 =

% Fineness of cement = (Weight retained/Total weight)*100

Result:

Comments: Frequently asked Questions :-

1) Number of Cement bags required per m3 for Concrete is ------------ a) 5.00 b) 7.72 c) 6.5 d) None 2) The Unit Weight of designed Concrete mix is a) 2.5 t / m3 b) 2.312 t / m3 c) 5 t / m3 d) none

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Slump Cone Test Aim :- To determine the Slump of given Concrete Apparatus :- i) Slump Cone ii ) Base metal plate with handle iii) Tamping rod of 60 cm long and 16 mm diameter vi ) Steel Scale . Theory :- Slump test is most commonly used method of measuring consistency of concrete which can be employed either in laboratory or at site of work . It is not a suitable method for very wet or very dry concrete . It does not measure all the factors contributing to workability , nor it is always representative of placebility of concrete However , it is a control test and gives an indication of the uniformity of concrete from batch to batch . Slump indicates characteristics of concrete . If the concrete slumps evenly it is called true slump . If one half of the cone slides down , it is called shear slump . In the case of a shear slump , the slump value is measured as the difference in height between the height mould and average value of the subsidence . Shear slump also indicates that the concrete is non – cohesive and shows characteristics of segregation . Procedure :- The internal surface of the mould is thoroughly cleaned and freed from super flous moisture and adherence of any old set concrete before commencing the test . The mould is placed smooth , horizontal , rigid and non-absorbent base plate . The mould is filled in four layers , each approximately ¼ th the height of the mould . Each layer is tamped 25 times by a tamping rod taking care to distribute strokes over the cross section . After the top layer is rodded , the concrete is struck off level with a trowel and tamping rod . The mould is removed from the concrete immediately by raising it slowly and carefully in vertical direction . This allows the concrete to subsided concrete is measured . The difference in height in mm . is taken as slump of concrete . Observations & Calculations :- Proportions of the Concrete mix Cement = Sand = Coarse Aggregate = Water = Height of Concrete before Subsidence ; ( h1 ) = Height of Concrete After Subsidence ; ( h2 ) = Slump Value of the Concrete = h1 - h2 Result :- Slump Value of the Concrete = Frequently asked Questions :-

1) Which of the following terms are associated with workability a) Mix ability b) Stability c) Compatibility d) All the above

2) What are the factors Governing Workability ?

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3) The Height of the slump Cone Apparatus is --------- a) 20cm b) 25cm c) 30cm d) 35cm 4) Draw the Diagrams of the True Slump, Shear Slump and Collapse

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Compaction Factor Test

Aim :- To Determine the Compaction factor for a given Concrete Apparatus :- i) Compaction factor apparatus ii) Trowel iii) Balance iv) Tamping rod , 60 cm long , 10 mm dia . Theory :- The Compacting factor test is designed primarily for use in the laboratory but it can also be used in the field . It is more precise and sensitive than the slump test and it is particularly use full for concrete mixes of very low workability as are normally used when concrete is to be compacted by vibration . Such dry concrete are insensitive to the slump . This test works on the principle of determining the degree of compaction achieved by a standard amount of work done by allowing the concrete to fall through a standard height . The degree of compaction called compacting factor is measure by density ratio i.e ratio of density actually achieved in the test to identify of same concrete fully compacted . This test measures the inherent characteristics of the concrete which relates very close to the workability requirements of concrete and as such it is one of the good tests to depict the workability of concrete . Procedure :- The sample of concrete to be tested is placed in the upper hopper up to the brim . The trap door is opened so that the concrete falls into the lower hopper. Then trap of the lower hopper is opened and concrete is allowed to fall into the cylinder . In the case of a dry-mix , it is likely that the concrete may not fall on opening the trap –door .In such a case , slight poking by a rod may be required to set concrete in motion . The excess concrete remaining above the top level of the cylinder is then cut off with the help of trowel . The out side of cylinder is wiped clean . The concrete is filled up exactly up to the top level of the cylinder . Its weight is measured . The weight is known as “ Weight of Partially Compacted Concrete “ The Cylinder is emptied and then refilled with the concrete from the same sample in layers approximately 5 cm deep . The layers are tamped by tamping rod uniformly giving 25 blows .The top surface of fully compacted concrete is then carefully struck of level with the top of cylinder and weighed . The weight is known as “ fully Compacted Concrete “ Weight of partially Compacted Concrete Compacting factor = ------------------------------------------------- Weight of fully compacted concrete Observations & Calculations :- Proportions of the Concrete mix Cement = Sand = Coarse Aggregate = Water = Weight of Partially Compacted Concrete ( W1) =

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Weight of fully Compacted Concrete ( W2) = Compacting Factor = W1 / W2 Result :- Report the Compacting factor for given concrete mix Frequently asked Questions :-

1) The Angular Aggregates used in Concrete a) Improves bond and decreases Workability b) Improves bond and increases Workability c) Decreases bond and decreases Workability

d) None

2) The Form of Compacting Factor -------- a) Weight of partially Compacted Concrete / Weight of Fully Compacted Concrete b) Weight of Fully Compacted Concrete / Weight of partially Compacted Concrete c) Both a& b d) None 3) The Unit Weight of designed Concrete mix is

a) 2.5 t / m3 b) 2.312 t / m3 c) 5 t / m3 d) none

4)Compaction factor test has been developed by ---------------- 5) What is the object of Compaction of Concrete ?

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Specific Gravity Of Cement

Aim: To determine the specific gravity of the given cement sample.

Apparatus: Specific gravity bottle, sensitive balance, water, kerosene.

Theory: Specific gravity is defined as the ratio of weight of given volume of solids to the weight of equal volume of water at a specified temperature, both weights taken in air.

G = γs / γw

Procedure :- 1.Specific gravity bottle is thoroughly cleaned and dried. Weight of empty specific gravity bottle is taken with stopper as W1.

2. About one third of the bottle is filled with cement and weighed with stopper as W2.

3. Then fill this bottle with kerosene till the neck and shake to fill the voids and weight is taken as W3.

4. Empty the specific gravity bottle and clean it thoroughly. Then fill it with kerosene only and weight is taken as W4

5. Again empty the bottle, clean the bottle and fill it with water weight is taken as W5 .Specific gravity is found by the formula as

Specific gravity of cement = )WW(

)WW( X

)WW()WW(

)WW(

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4312

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−−

−−−−

Observations &Calculations : -

W1 =Empty weight of specific gravity bottle =

W2 =Weight of bottle filled with 1/3 rd of cement sample =

W3 =Weight of bottle + cement +kerosene =

W4 = Weight of bottle completely filled with kerosene =

W5 = Weight of bottle completely filled with water =

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Specific gravity of cement = )WW(

)WW( X

)WW()WW(

)WW(

15

14

4312

12

−−

−−−−

Result :- The Specific Gravity of Cement = Frequently asked Questions :-

1) The General Value of the Specific Gravity Of Cement ----------- 2) The 7 Days Strength of M 30 Concrete mix is ------------- 3) Write the Form of Specific Gravity of Cement 4) Cement Starts losing its Strength if stored for more than -------- months

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Bulking Of Fine Aggregate Aim: To determine the bulking percentage of the given fine aggregate. Apparatus: Cylindrical container , Balance, Graduated cylinder, mixing tray, Steel rule, Oven. Theory: Free moisture content in fine aggregate results in bulking of volume. The film formed around each particle exerts surface tension force and keeps every particle away from each other. Therefore no point of contact is possible between the particles. This causes bulking of volume. Bulking increases with increase in moisture content up to certain limit and beyond that further increase in moisture content results in decrease in volume and at a moisture content representing saturation point, the fine aggregate shows no bulking. Due to bulking, fine aggregate shows completely unrealistic volume. Therefore it is absolutely necessary that consideration must be given to the effect of bulking in the proportioning of concrete by volume. If cognizance is not given for the effect of bulking, in case of volume batching, the resulting concrete likely to be undersanded and harsh. It will also affect the yield of concrete for a given cement. Procedure: 1.. Put sufficient oven dry sand loosely in to a container, until it is 2/3 full. Level the top of the sand and push a steel rule vertically down through the sand at the middle to the bottom. Measure the height of sand, h1.

2. Empty the sand in to a clean metal tray. 3. Add 1% by weight of water to sand, mix the sand and water thoroughly. 4.Put the wet sand loosely in to the container without tamping it, level the surface and measure retained sand height by a steel rule at the middle,h2.

5. Repeat the experiment with increasing water content by one percent each time. Observations &Calculations : - W1= weight of the mould = W2 = Weight of the mould + sand = (W2-W1 ) = Weight of sand = H = Height of sand =

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S.No

% of water added

Height of the sand after the addition of water,h1

% of bulking ((h1- H)/H )*100

Graph: A graph is plotted between water content and percentage bulking.

Result :-

Comment: Frequently asked Questions :-

1) Final Volume of water to be taken after correction for bulking of sand in m3 is ---- a) 0.2 b) 0.125 c) 0.119 d) none 2) Bulking increases with increases in –----- a) Moisture Content up to certain limit b)Water Content up to certain limit c)Both a & b d)None

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Vee- Bee Consistometer Test

Aim: To determine the workability of concrete by indirect method ( vee bee consistometer)

Apparatus: Vibrating table, A metal pot, Sheet metal cone, A standard iron rod.

Theory:- The wider definition of workability is “ease with which concrete can be compacted hundred percent having regard to mode of compaction and place of deposition . ”For a concrete technologist, a comprehensive knowledge of workability is required to design a concrete mix. Vee Bee Consistometer test is a good laboratory test to measure indirectly the workability of concrete.Vee- bee consistometer method is suitable for dry concrete mixes.

Procedure: 1.Slump test is performed, placing the slump cone inside the sheet metal cylindrical pot of the consistometer.

2. The glass disc attached to the swivel arm is turned and placed on the top of concrete pot.

3. The electrical vibrator is then switched on and simultaneously a stop watch is started.

4. The vibration is continued till such a time as a conical shape of concrete assumes a cylindrical shape.

5. Immediately when the concrete fully assumes a cylindrical shape, the stop watch is switched off.

6. The time required for the shape of concrete to change from slump cone shape to cylindrical shape in seconds is known as “Vee bee Degree”.

Result:

Comment:

Frequently asked Questions :-

1) In Vee- Bee Consistometer method Slump is measured in terms of ------------ 2) Write the advantages of using concrete 3) Write the Disadvantages of using Concrete 4) Write the types of concrete ?

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Modulus Of Elasticity Of Concrete

Aim: To determine the modulus of elasticity of concrete

Apparatus: 1. Compression testing machine (CTM)

2. Compressometer

Procedure: 1. Take a cylindrical shape of 15 cm diameter and 30 cm long from the curing pond , allow it to dry and fix the specimen with compressometer.

2. Keep the specimen on the table of the compression testing machine, taking care that it is exactly at the centre.

3.Apply the load continuously at a rate of 140 kg/cm2 per minute until the average stress reaches at a time ‘t’ of the estimated compressive strength.

4. Maintain the stress for at least one minute and the CTM and compressometer readings are noted again.

5. Apply the load second time at the same time till the average stress of (c + 1.5) kg/cm2 is reached .Note down corresponding readings.

6. Repeat the above procedure.

7. Note concrete loading beyond (c + 1.5) kg/cm2.

8.. Note the loads at fixed intervals of strain to plot ‘stress- strain curve’.

Observations &Calculations :-

Calculations are done for getting strains at various loads, in two cylinders and plot the stress and strain in the graph. Draw straight line through the point of each cycle and fix the slope of each cycle and fix the average value. If the difference between the individual values is less than 15% of average values, the average value expressed in kg/cm2 to the nearest 1000 kg/cm2 be recorded. If the difference is more than 15% specimen is removed from the machine and the test is repeated.

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Plot a graph between stress-strain readings observed beyond one third of average compressive strength which gives a S-S graph.

Result :-

Comment : -

Frequently asked Questions :-

1) The Poisson’s ratio for Concrete ------ 2) Poisson’s ratio increases as the modulus of elasticity --------

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Compressive Strength Of Concrete

Aim: To determine the compressive strength of concrete conducting tests on cube and cylindrical samples and comparing them.

Apparatus: A Compression testing machine of 2000kN capacity, concrete cube specimen of 15 cm* 15 cm * 15cm and cylindrical specimen of 15 cm diameter and 30 cm height cast and cured for 28 days.

Theory:-Compression test develops a rather more complex system of stresses. Due to compression load, the cube or cylinder undergoes lateral expansion owing to poisson’s ratio effect. The steel platens do not undergo lateral expansion to the some extent of concrete, with the result that steel restrains the expansion tendency of concrete in the lateral direction. This induces a tangential force between the end surfaces of concrete specimen and adjacent steel platens of the testing machine. Due to this platen restrains the lateral expansion of the concrete in the parts of the specimen near its end.

It is interesting to note that the restraining effect of the platens of the testing machine extends over entire height of the cube but leaves unaffected a part of test cylinder because of greater height. It is, therefore the strength of cube made from identical concrete will be different from the strength of cylinder. Normally strength of cylinder is taken 0.8 times strength of the cube, but experiments shown that there is no unique relationship between strength of the cube and strength of cylinder. However cylinder is less affected by the end restrains caused by platens and hence seems to give more uniform results than cube.

Procedure: 1. Take out the cube and cylinder specimen from water before testing. The samples should be tested when they are still wet.

2. In case of cube samples the specimen should be kept in the machine in such a manner that the load should be applied to the opposite sides of the cubes as cast, that is not to the top and bottom.

3. Align the axis of the specimen with the centre of thrust of the spherical seated platen. Rotate the movable portion gently by hand to obtain uniform seating.

4. Adjust the loading continuously through the rate control value by hand to 140 kg/cm2 per minute or 32 t per minute for cube and 25 t per minute for cylindrical specimen.

5. Increase the load until failure and note the maximum load.

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Observations and Calculations :-

CUBE CYLINDER Identification Date of test Date of casting Weight of the specimen, N Dimensions of specimen Cross sectional area Maximum load, N Ultimate compressive strength ,N/mm2

Ratio of cylinder strength to cube strength

Result:

Comment:

Frequently asked Questions :

1) Write the Types of Concrete ? 2) A lean mix is a concrete mix having 3) Concrete is week in ----------

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Initial and Final Setting Times Of Cement

Aim: To determine the initial and final setting times of cement.

Apparatus: Vicat’s apparatus with needles for initial and final setting , tray, measuring jar, balance, stop watch, weigh box, glass plates.

Theory: Time lag between the time at which water is added to the cement and the time at which the needle fails to pierce the test block by 5+0.5 m.m. from the bottom of the mould 0r 33-35 m.m from the top, will be the initial setting time of cement. This test is used to detect the deterioration of cement due to storage.

Procedure: Take about 500 gms of cement and prepare a cement paste of 0.85 times water required for normal consistency. Place the Vicat’s mould on a non-porous plate and place the cement paste in the mould and level the surface.

For determining the initial setting time , the needle of 1 mm2 or(1.13 mm diameter is fitted to the Vicat’s apparatus)Place the mould filled with cement paste under the needle. Lower the needle gently to touch the surface at the cement and allows it to penetrate in to the paste. Repeat the procedure at regular intervals till the needle stops penetrating 5 mm from the bottom of the paste mould. The period of time between which the needle fails to pierce the test block by 5 mm is the “initial setting time”.

For determining the final setting time fix an angular ring to the mould rod, release the needle gently and note down the time when the needle gently makes an impression on the mould surface and the angular ring fails to do so. In other words paste has attained such hardness that the centre needle does not pierce through the paste more than 0.5 mm. The final setting time is the time elapsed between the time of addition of water to the cement and the time at which needle makes an impression on the surface of the sample and the angular ring fails to do so.

Calculations:

Weight of cement taken =

Water required for standard consistency (p) =

Weight of water taken for preparing the specimen=0.85 p =

S.No %Water added Volume of water ,ml Time,sec Penetration,mm

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Precautions: 1. Conduct the experiment at 25o to 30o c at a regular humidity of 90%.

2. After adding water, mix thoroughly for a minute.

3. Clean the needle after every penetration during every observation.

Result:

Comments:

Frequently asked Questions : -

1) Define Water Cement ratio ? 2) The Initial Setting time of cement is ----- 3) The final Setting Time of cement ----- --

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NON DESTRUCTIVE TEST OF CONCETE

-Rebound hammer test

Aim:To determine the compressive strength of concrete using rebound hammer.

Apparatus:Concrete test rebound hammer,carborundum stone calibration chart.

Theory:The type N concrete test hammer is intended for non destruction testing quality of concrete in the finished structure. When testing the concrete rebound number which depend s on the strength of the mortar close to the surface.Since the strength of mortar as arule determines the strength of concrete, the rebound number gives an indication of the strength of concrete.The correlation between the rebound number and strength of concrete is derived from a number of hammer tests on cubes and then by crushing the cube under the compression testing machine immediately after the hammer test.

Procedure: 1.Select suitable points on the surface to be tested.Usually vertical surface of concrete are preferred.

2. Remove any plaster or coating from the surface to be tested. Smoothen any slightly un level surfaces caused by unplanned forces using the carborundum stone.

3. If the test is to be conducted on old concrete surface remove excessively hard surface layer to a depth of approximately 12.5 mm, using a light weight, high speed hand grinder.

4. Release the plunger of the hammer by lightly pressing on the head of the impact plunger.

5. Press the plunger against the spot of the concrete surface to be tested. Just before it disappears in the housing release the hammer by slowly increasing the pressure on the housing. At the moment of impact the hammer should be held exactly at right angles to the surface and the push button should not be touched.

6. After the impact the hammer rebound mass rebounds by a certain amount which is indicated on the scale by a rider.

7. Determine the compressive strength of concrete using the calibration chart corresponding to the rebound number is recorded.

8. After finishing the test block the plunger with its guide bar and guide disk in the rear position by means of the push button.

9. When the test hammer is to be used an inclined or horizontal surface the rebound value R should be corrected as given below.

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Rebound value Correction for inclination angle, α Upwards Downwards +900 +450 -450 -900

10 +2.4 +3.2 20 -5.4 -3.5 +2.5 +3.4 30 -4.7 -3.1 +2.3 +3.1 40 -3.9 -2.6 +2.0 +2.7 50 -3.1 -2.1 +1.6 +2.2 60 -2.3 -1.6 +1.3 +1.7

Observations and Calculations:

Sample1 Sample2 Sample3

Rebound value

Result: