Laboratory Tests on Construction materials

Laboratory Tests on Construction materials
Dr.K.Lakshmipathi, Centre Head, Centre for Rural Infrastructure C to 18

. Bricks . Cement . Aggregates . Concrete . Steel
Materials- Bricks Cement Aggregates Concrete Steel C to 18

Tests on common building bricks
Dimensions and tolerances test. Compressive strength test. Water absorption test. Efflorescence test. C to 18 8

Testing of Bricks Before using the bricks for any important engineering work, they should be tested to know their suitability for the work. For testing the bricks, their samples should be taken. In general 50 bricks are selected for every consignment or stacking for 50,000 bricks. C to 18 4

Methods for selection of brick samples:
Sampling in motion Some samples of bricks shall be taken when bricks are being moved as in the case of loading or unloading at regular intervals so as to get a true representation of the whole quantity. C to 18 5

(2) Sampling from a stack
Sample shall be taken out at random from a stack of bricks. The number of bricks required for the test shall be selected from the top, the sides accessible and interior of the stack. C to 18 6

Contd… The sample taken by either of the two methods, shall be
stored in a dry place until the tests are completed. C to 18 7

Compressive strength test
Purpose This test is performed to know the crushing strength of bricks which should not be less than the specified limit. C to 18 9

Method In this test, five bricks out of the samples already taken are
selected at random. They are immersed in water at room temperature for 24 hours. Then ,the bricks are taken out from water and wiped free from surplus moisture at room temperature. C to 18 10

Contd… After this, their frogs and all voids in the bed and face shall
be filled with cement mortar 1:1 (1 cement ,1 clean course sand of grain size 3mm and down ) C to 18 11

Contd… The bricks shall then be stored under damp sacks for 24 hours.
After the expiry of this period, they shall be immersed in water for three days. C to 18 12

Contd… At the end of three days, the samples of bricks shall be
taken out, wiped dry. Then, each brick shall be placed between two or three ply thin polywood sheets, each approximately 0.3 cm thick, with flat surfaces horizontal and the mortar filled face upward. C to 18 13

Contd… This arrangements shall be carefully centered between the
plates of compression testing machine. The load shall be applied at a uniform rate of 140kg/sq.cm per minute until failure occurs. The maximum load at failure divided by the surface area of the brick on which load is acting is taken at it’s compressive strength. C to 18 14

Result The arithmetic mean of the compressive strength of five such
tests shall be taken as the compressive strength of the lot or stack where from the samples have been taken. C to 18 15

Note The compressive strength of any individual brick shall not fall below average compressive strength specified for the corresponding class of brick by more than 20%. C to 18 15

Contd… Common building brick shall have a minimum compressive
strength of 35kg/cm2. C to 18 17

Water absorption test Also known as 24hr, immersion cold water test.
Purpose. This test is performed to know the water absorption capacity of bricks. C to 18 18

Method In this test, five bricks shall be selected at random out of the sample of bricks already taken. They are then dried in a ventilated oven at 105o to 115oc till they attain almost constant weight. C to 18 19

Contd… The specimens shall then be cooled to room temperature and weighed. Let it be W1 un its. The dry and cooled specimens shall be completely immerse in clean water at 27o_ 2oc for 24 hours. + C to 18 20

Contd… Each specimens shall then be removed, the surface water
wiped off with a damp cloth and then weighed. Weighing shall be completed within three minutes after removing the specimen from water. Let it be W2 units. C to 18 21

Contd… Then the water absorption capacity of the specimen is found as given below. Let W1= Weight of dry specimen. W2= Weight after soaking in water i.e., weight of wet specimen. Percentage water absorption ( by dry wt) = W2-W1x 100 W1 C to 18 22

Result The average of the five specimens should be taken as the
water absorption capacity of the lot or stack of bricks from where the samples have been taken. C to 18 23

Note The average water absorption of common building bricks
shall not be more than 20% up to class 1 &2 and 15% for higher class by weight after immersion in cold water for 24 hours. C to 18 24

Tests on Sand Definition:
Sand is an Inorganic Material which is Sharp, Angular and Rounded grains of Silica (SiO2). C303.25to26

FUNCTIONS OF SAND: Reduce the shrinkage of binding material.
Prevents development of cracks in the mortar after drying. Helps in hardening of fat lime. Making mortars of desired grade C303.25to26

Classifications of sand :
NATURAL SAND ARTIFICIAL SAND C303.25to26

Natural sand is of 3 types
1.River sand 2. Pit Sand 3. Sea Sand C303.25to26

RIVER SAND PIT SAND SEA SAND Obtained from beds and bank of rivers.
pits dug. sea shore. 2) These particles are fine, round and polished. consists of sharp angular grains free from salts. consists of fine, round & polish. 3) Colour is white globular shape & smaller in size than pit sand and it is ready to use . 3) It should be screened & washed before using it. 3) It attracts moisture from the atmosphere & cause permanent dampness. C303.25to26

Artificial sand Artificial sand is obtained by crushing stones and
gravels to powder. C303.25to26

Bulking Of Sand: Increase in volume of sand due to presence of
surface moisture is called Bulking of sand. C303.25to26 C-05/C

Percentage of bulkage allowance to be made
In preparing mortars and concrete, it is necessary to determine the percentage of bulking of sand. Accordingly, allowances should be made for the bulkage by adding extra amount of sand. C303.25to26

Bulking of sand various moisture contents
The volume of bulking of sand for various moisture content are given below Bulking of sand various moisture contents Moisture contents percentage by weight Percentage of bulking Fine sand Medium sand Coarse sand C303.25to26

Table ( continued ….) Percentage of bulking 6 37 28 18 8 35 26 16
Moisture contents percentage by weight Fine sand Medium sand Coarse sand Percentage of bulking C303.25to26

C303.25to26

Contd.. When the sand is moistened ,every particle of it gets covered with a thin film of surface moisture . This moisture tends to keep the particles away from one another and cause bulking (increase in volume )of sand C303.25to26

Contd.. It has been observed that with the additions of 5% to
6% of moisture content by weight , the volume of dry sand increases by 18% to 38%. The bulking of fine sand is greater than that of the coarse sand C303.25to26

Contd.. If the percentage of moisture content is increased beyond 10% the bulking of sand starts decreasing and when sand in completely saturated, its volume is equal to that of dry sand C303.25to26

Tests on Cement The cement is obtained by burning at a very high temperature of a mixture of calcareous and argillaceous materials. The mixture of ingredients should be intimate and they should be in correct proportion. The calcined product is known as clinker. A small quantity of gypsum is added to clinker and it is then pulverized into very fine powder which is known as cement. C303.28To29

Contd.. Cement is a fine, soft, powdery-type substance. It is made from a mixture of elements that are found in natural materials such as limestone, clay, sand and/or shale. When cement is mixed with water, it can bind sand and gravel into a hard, solid mass called concrete. C303.28To29

Cement History: In 1824, Joseph Aspdin, a British stone mason, heated a mixture of finely ground limestone and clay in his kitchen stove and ground the mixture into a powder to create a hydraulic cement—one that hardens with the addition of water. C303.28To29

Fig. 1 Construction with cement
continued.. Fig. 1 Construction with cement C303.28To29

Contd.. He took a patent for this cement
A variety of sandstone is found in abundance in Portland in England. Hence it called as “ ORDINARY PORTLAND CEMENT “ ( O P C ) The first cement factory was installed at Tamil Nadu in India 1904 by South India Industry Limited. C303.28To29

Do you know? Four essential elements are needed to make cement. They are Calcium, Silicon, Aluminum and Iron. Calcium (which is the main ingredient) can be obtained from limestone, whereas silicon can be obtained from sand Aluminum and iron can be extracted from bauxite and iron ore, and only small amounts are needed. C303.28To29

CHEMICAL COMPOSITION OF CEMENT
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. C303.28To29

Table 1 Chemical composition of cement
Oxide Percent content CaO (Lime) SiO2 (Silica) Al2O3 (Alumina) Fe2O3 (Iron oxide) MgO (Magnesia) Alkalies(K2O,Na2O) SO3 (Sulphur trioxide) 60-67% 17-25% 5-8% 0.5-6% 0.1-4% % 1-3% C303.28To29

FUNCTIONS OF CEMENT INGRADIENTS:
LIME(CaO): Major ingredient of cement Excess quantity makes the cement unsound If it is less, it decreases the strength and allows the cement to set quickly C303.28To29

Contd.. SILICA(SiO2): An important ingredient which gives strength to cement. If it is in excess allows the cement to set slowly. C303.28To29

Contd.. ALUMINA(Al2O3): This imparts quick setting time to the cement.
If it is in excess quantity weakens the cement. It also lowers the temperature of clinkers. C303.28To29

Contd.. IRON OXIDE(Fe2O3):
It helps the fusion of the raw materials during burning state. It gives colour, strength and hardness to cement. C303.28To29

Contd.. MAGNESIUM OXIDE (MgO):
If present in small quantity, imparts hardness and colour to cement. If in excess quantity, weakens the cement. C303.28To29

Contd.. SULPHUR TRIOXIDE(SO3):
A very small quantity is required in the manufacturing of cement. If it is in excess, it makes the cement unsound. C303.28To29

Contd.. ALKALIES: A small quantity is required.
Alkalies and other impurities present in raw materials are carried by the flue gases during heating. If it is in excess quantity efflorescence is caused. C303.28To29

Laboratory Tests on Cement:
Fineness of cement Consistency of cement Setting times of cement Soundness of cement Compressive Strength of cement Tensile strength of cement C303.32to33

Fineness of cement The fineness of cement is a measure of the size of cement. It is necessary to check the proper grinding of cement, it has a influence on the behavior of cement. C303.32to33

Procedure to find the fineness of cement
Breakdown any air set lumps in the cement sample with finger and mix it uniformly. Weigh 100gm of the cement to the nearest 0.01g and place it on a clean and dry 90 IS sieve with pan attached. Continuously sieve the sample by holding the sieve in both hands for 15 minutes with a gentle motion. 4. While sieving it, ensure that there is no spilling of the cement. C303.32to33

Contd.. Do not use washers, shots and slugs on the sieve.
Slightly brush under side of the sieve after every 5 minutes of sieving. Find the weight of residue on the sieve after the value as a percent of the original sample taken. Fineness of cement in represented as the percent of material passing through the sieve C303.32to33

Specimen calculation:
Weight of cement taken = W g Weight of residue = W g (Fineness of the cement should not more then 10%) Percentage of residue Result: % of passing of given sample = % of residue C303.32to33

Normal consistency of cement
C303.32to33

Definition : Normal consistency is defined as that percentage of water required to produce a cement paste of standard consistency. C303.32to33

VICAT APPARATUS 1 Fig 4 C303.32to33

Procedure to find the normal consistency of cement
Take 300gm of cement sample and place at on a non-absorbent plate. Take 25% of water by weight of cement as first trial and mix it thoroughly with cement using gauging trowels. Ensure that the time of gauging shall be with in 3 to 5 minutes. The time of gauging shall be reckoned from the instant water is added to cement to that paste is filled in the mould. C303.32to33

Contd… Keep mould on a non absorbent plate. Apply a thin coat of oil inside the mould. 4. Fill the vicat’s mould with cement paste at a stretch and tamp the mould so as to make the cement spread uniformly in the mould. Strike off the excess cement plate and level the surface of mould with spatula. 5. Fix the plunger of 10mm dia x 50mm long to the plunger holder of the apparatus. Gently lower the plunger to touch the mould’s top surface and level it quickly. Due to the weight of header and holder the plunger settles to the cement paste. C303.32to33

Contd… Note the plunger penetration reading on the scale of apparatus. The recorder penetration value is reckoned from the bottom of mould. Remove the plunger and cement paste from the mould. Take sample of cement and repeat the entire process with 27% of water and note down the plunger penetration. C303.32to33

Contd… 9. Repeat the above process with varying % of water and
note the penetration of plunger till the penetration value is 5 to 7 mm. measured from the bottom of the mould Note :The standard consistency of ordinary Portland cement is 30 to 35% by weight of cement C303.32to33

Specimen calculation :
Weight of cement taken = g Percentage of water added = % Initial reading on vicat scale in mm = Final reading on vicat scale in mm = Penetration of plunger measured from bottom of mould in mm = C303.32to33

Result : The standard consistency of mould = _____ % C303.32to33

Initial and Final setting time of cement
C303.32to33

Theory : When water is added to cement, the paste starts stiffening and gaining strength, simultaneously loosing its plasticity. Two stiffening states are identified as initial and final setting times respectively. Initial setting time is the interval between the addition of water to cement and the stage when needle ceases to penetrate completely. This time should be about 30 minutes for ordinary cement. C303.32to33

Procedure : Preparation of test block
Prepare a neat cement paste by mixing the cement with 0.85 times the water required to give a paste of standard consistency. 2. Start stop watch at the instant when water is added to cement. Thoroughly mix cement and water using gauging trowels till required uniformity is attained in mixing. C303.32to33

Contd… Fill the mould completely and smoothen the surface of the paste by making it level with the top of the mould. The cement block thus prepared in the mould is the test block. Note : Clean appliance shall be used for mixing. All apparatus shall be free from vibration during the test. Care shall be taken to keep the needle straight. C303.32to33

(B) Initial setting time :
Place the test block with porous plate at bottom, under the rod bearing the needle (c) as shown in the fig. 1 Lower the needle gently until it comes in contact with the surface of test block and quickly release, allowing it to penetration into test block. C303.32to33

Contd… Repeat this procedure at regular intervals of time until the needle, when brought in contact with the test block and released as above fails to pierce the block for 5 to 7 mm measured from the bottom of the mould. 4. The period elapsed between the time when water is added to the cement and the time at which the needle fails to pierce the test block to a point 5 to 7 mm measured from the bottom of the mould shall be reported as initial setting time. Note :The initial setting time of ordinary Portland cement is 30 minutes C303.32to33

(c) Final setting time :
Replace the needle ‘c’ of the vicat apparatus attachment. Prepare the test block according to the procedure given above. 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 while the attachment fails to do so. C303.32to33

Contd… The period elapsing between the time when water is added to the cement and the time at which the needle makes an impression on the surface of the test block while the attachment fails to do so shall be the final setting time. Note :The final setting time of ordinary Portland cement is 600 minutes C303.32to33

Specimen calculation :
Sample : sample of OPC Water required to prepare a cement paste of standard consistency = p Weight of cement required for 1 mould = 300 g Weight of water added to cement =(0.85p x 300g ml) 100 C303.32to33

( A) Initial setting time :
Time elapsed since the water is added to cement = min Initial reading on vicat apparatus in min (a) = Final reading on vicat apparatus in mm (b) = Penetration of vicat needle measured from The bottom of mould in mm (b-a) = C303.32to33

Result : Initial setting time for the given cement sample = __________ min Final setting time for the given cement sample = __________ min Note : The result of initial and final setting time shall be reported to nearest five minutes. C303.32to33

Compressive strength of cement
C303.32to33

Procedure: preparation of test cubes:
As per I.S specification cement mortar of 1:3 is used. The following quantities of materials required for each cube: Cement :185g ii) Standard sand : 555g[185g each of grade-1(Size-2mm to 1 mm), grade-2(Size - 1 mm to 0.5mm), grade-3(Size-0.5 mm to 90 microns)] C303.32to33

Contd… iii) Water : [(P/4)+3.5 ] % of combined weight of cement & sand, where p is the percentage of water required to produce a paste of standard consistency. C303.32to33

Contd.. Weight the cement and standard sand of three grades in required proportion and place them on a non absorbent plate. Mix the ingredients in dry condition with gauging trowels, add the measured quantity of water to the dry matrix and mix them thoroughly applying sufficient pressure till uniform consistency is achieved. Ensure the time taken for mixing shall not exceed 4 minutes. C303.32to33

Contd… 3. place the entire quantity of mortar into the mould and tamp the mould using 12mm dia. tamping rod by 25 times. place the mould on the mould housing unit of the cement mortar vibrator as shown in fig.2 and clamp all the check nuts and spring washers tightly. C303.32to33

Contd.. 4. Vibrate the cube for a period of 2 minutes. Remove the mould from the vibrator and keep it on a dry area. Repeat the process for casting nine cubes. Fig 2 Mortar vibrator C303.32to33

Contd.. 5. Demould the cubes after 24 hours and transfer them to curing tank. keep the cubes in curing tank for 28 days and find the compressive strength of cement as per the standard procedure at the age of 3,7and 28days. C303.32to33

U T M C T M Fig. 3 C303.32to33

Specimen calculation:
Area of the cubes (A) 7.07cmx7.07cm = 5000sq.mm Crushing load (W) = Compressive strength (W / A) = N/sq. mm C303.32to33

Result : compressive strength of cement at the age of : 3days =
C303.32to33

Soundness test C303.32to33

4 C303.32to33

Contd.. The apparatus is shown in fig . 4, it consists of a small split cylinder of spring brass or other suitable metal. 2. It is 30mm in dia and 30mm high. 3. On either side of the split are attached two indicator arms 165mm long with pointed ends. C303.32to33

Contd.. 4. Cement Is gauged with 0.78 times the water required
for standard consistency(0.78p) in a standard manner and filled into the mould and kept on a glass plate. 5. The mould is covered on the top with another glass plate. 6. The whole assembly is immersed in water at a temperature of 270C - 320C and kept there for 24 hrs. C303.32to33

Contd.. Measure the distance between the indicator points.
Submerge the mould again in water. heat the water and bring to boiling point in about minutes and keep it boiling for 3hours. 9. Remove the mould from the water, allow it to cool and measure the distance between the indicator points. C303.32to33

Contd.. 10.The difference between these two measurements
represents the expansion of cement. This must not exceed 10mm for ordinary, rapid hardening and low heat Portland cements. 11.If in case , the expansion is more than 10mm as tested above, the cement is said to be unsound. C303.32to33

Workability The strength and quality of concrete depends on w/c ratio
Excess w/c ratio improves workability , but reduces strength and durability Workability is the ease with which concrete is handled , transported and placed in forms with minimum loss of homogeneity C303.45

Hydration of cement When water is added to cement, chemical reaction takes place between water and cement . This reaction is known as hydration of cement Exothermic in nature and releases heat C303.45

Process of hydration is faster in early stages
During curing period of 28 days , 90% of hydration takes place Approximately 50 % of water by mass of cement is required for complete hydration C303.45

Factors influencing rate of hydration
Type of cement Fineness of cement Temperature at the time of mixing C303.45

Water – Cement ratio The ratio of amount of water to the amount of cement by weight is known as water – cement ratio . C303.45

Effects of W/C ratio The strength and quality of concrete depends on w/c ratio Excess w/c ratio improves workability , but reduces strength and durability Addition of extra one lit of water per bag of cement reduces strength of concrete by 1.5 N/mm2 C303.45

Contd W/C ratio for structures exposed to weather should be carefully decided For structures which are regularly subjected to wetting and drying , w/c ratio by weight should be 0.45 to 0.55 For structures which are continuously under water , w/c ratio by weight should be 0.55 to 0.65 C303.45

Advantages of low water/cement ratio:
Increased strength Lower permeability Increased resistance to weathering Better bond between concrete and reinforcement Reduced drying shrinkage and cracking Less volume change from wetting and drying C303.45

Fig.1 Relation between the compressive strength to water cement ratio

Workability Ease with which concrete is handled , transported and placed in forms with minimum loss of homogeneity If more water is added , it improves workability but reduces strength and durability C303.45

Contd. Can be improved by changing the proportions of fine & coarse aggregate Can be improved by adding certain admixtures Can be measured by slump test, compaction factor test C303.45

Fig.2 Measurements of workability : Slump
C303.45

Fig.3 Measurements of workability : Slump
(d) Fig.3 Measurements of workability : Slump C303.45

Tests on Aggregates Types of Aggregates Fine aggregate
Coarse aggregate C303.46

Coarse aggregate Retains on IS sieve 4.75 mm
Stone chips are commonly used C303.46

Characteristics of coarse aggregate :
Angular, dense, free from flaky surface and impurities Should have high strength against crushing Nominal size is 20 mm for RCC works Nominal size is 40 mm for mass concrete C303.46

Functions of coarse aggregate
Makes solid and hard mass of concrete Increases strength of concrete Occupies major space and makes concrete economical C303.46

Water absorption Minute voids are formed in rocks during formation and also due to atmospheric action The pores vary in size and distributed throughout the body of rock Porosity of commonly used rocks varies from 0 to 20 % Percentage of water absorbed by the aggregate when immersed in water is known as Water absorption of aggregate C303.47

Importance of water absorption
Quantity of porosity and water absorption of aggregate will affect water cement ratio Affects workability of concrete When aggregate is dry , hydration will not be complete , lowers the workability and reduces the strength of concrete C303.47

Contd. Contd. If the aggregate is fully saturated , water content in concrete will be more and concrete will become honey combed, reduces strength and density of concrete The knowledge of Water absorption of aggregate is important for concrete mix design calculation C303.47

Bulking of fine aggregate
Increase in volume of fine aggregate caused by presence of water is known as bulking Bulking depends on percentage of moisture and fineness of sand Bulking increases gradually with increase in moisture content up to certain point and decreases to its original volume with further increase in moisture content C303.47

Contd. For ordinary sand bulking varies from 15 to 30%
Finer sand bulks considerably If sand is measured by volume and no allowance is made for bulking, the mix will be richer C303.47

Sieve analysis Is an operation of dividing a sample of aggregate into fractions , each consisting of particles of same size I.S Sieves of aperture size used for sieve analysis are 80mm, 40mm, 20 mm, 10mm, 4.75 mm, 2.36 mm , 1.18mm , 0.6mm, 0.3mm, 0.15mm . C303.47

Contd. From sieve analysis , the particle size distribution is found
Grading pattern of aggregate is assessed Useful in the design of concrete mixes

TESTS ON AGGREGATE

1. SIEVE ANALYSIS OF AGGREGATES
Each type of aggregate test requires a specified aggregate size (E.g mm for crushing test) Each bituminous mix type has a recommended aggregate gradation (% passing 26.5 mm in 55-90 for GSB1) So aggregate is passed through a set of sieves to get material of various sizes Procedure Bring the sample to an air dry condition either by drying at room temperature or in oven at a temperature of 100oC to 110oC.Take the weight of the sample. Clean all the sieves and sieve the sample successively on the appropriate sieves starting with the largest. Shake each sieve separately over a clean tray. On completion of sieving note down the weight of material retained on each sieve. Report the results as cumulative percentage by weight of sample passing each of the sieves. Sieves and Sieve-shaker

Observation Sheet

Test Set-up Significance
Aggregate crushing value provides a relative measure of resistance to crushing under a gradually applied compressive load Aggregates subjected to high stresses during rolling and severe abrasion under traffic Also in India very severe stresses come on pavements due to rigid tyre rims of heavily loaded animal drawn vehicles Test Set-up

Procedure Surface dry aggregates passing 12.5 mm and retained on 10 mm selected 3.25 kg aggregate required for one test sample Cylindrical measure filled with aggregates in 3 layers, tamping each layer 25 times After leveling the aggregates at the top surface the test sample is weighed The cylinder is now placed on the base plate The cylinder with the test sample and plunger in position is placed on compression machine Load is applied at a rate of 4 tonnes per minute upto 40 tonnes The crushed aggregate is taken out, sieved through 2.36 mm IS sieve and weighed to get material passing Aggregate crushing value = W2*100/W W2= Weight of crushed material, W1=Total weight of sample Load Application Sample being loaded in the compression machine at 4 T per minute for 10 minutes (upto 40 T)

Indirect measure of crushing strength
Observation Sheet Discussion Indirect measure of crushing strength Low value indicate strong aggregates Surface course need more strength than base course Should not exceed 30% for cement concrete surface , and 45% for others Specifications

3. Aggregate Impact Test Test Set-up Significance
This test assesses the suitability of aggregate as regards the toughness for use in pavement construction Road aggregates subjected to pounding action due to traffic loads so possibility of breaking Should be tough enough- so proper aggregates to be used Suitability to be checked by laboratory tests Procedure 1. Aggregate passing through 12.5 mm IS sieve and retained on 10 mm sieve is filled in the cylindrical measure in 3 layers by tamping each layer by 25 blows. Determine the net weight of aggregate in the measure(W1) 2. Sample is transferred from the measure to the cup of aggregate impact testing machine and compacted by tamping 25 times The hammer is raised to height of 38 cm above the upper surface of the aggregates in the cup and is allowed to fall freely on the specimen. After subjecting the test specimen to 15 blows, the crushed aggregate is sieved through IS 2.36 mm sieve 5. Weigh the fraction passing through IS 2.36 mm sieve(w2) Aggregate impact value = w2/w1*100 w2 = Weight of fines passing 2.36 mm w1 = Weight of sample 7. Mean of the two values reported. Test Set-up

4. Los Angeles Abrasion Test
Significance It is resistance to wear or hardness of aggregates Road aggregates at the top subjected to wearing action Under traffic loads abrasion/attrition action within the layers as well To determine suitability, tests have to be carried out Procedure 1. Aggregates dried in oven at °C to constant weight conforming to any one of the gradings E.g gm of mm, 1250 gm of mm, 1250 gm of mm, 1250 gm of mm, with 12 steel balls 2. Aggregate weighing 5 kg or 10 kg is placed in cylinder of the machine(W1gms) Machine is rotated at rpm for 500 revolutions Machine is stopped and complete material is taken out including dust. 5. Sieved through 1.7 mm sieve 6. Weight passing is determined by washing the portion retained, oven drying and weighing (W2 gms) 7. Aggregate abrasion value is determined A.A.V. = W2/W1*100 W2 = Weight of fines passing 1.7 mm, W1 = Weight of the sample Test Set-up

Discussion Select a grading close to the project for testing Simulate both abrasion and impact due to wheel loads It determines the hardness of the stone

5. Shape Tests on Aggregates
a. Flakiness Index b. Elongation Index c. Angularity Number Significance Shape of crushed aggregates determined by the percentage of flaky and elongated particles Shape of gravel determined by its angularity number Flaky and elongated aggregate particles tend to break under heavy traffic loads Rounded aggregates preferred in cement concrete pavements as more workability at less water cement ratio Angular shape preferred for granular courses/flexible pavement layers due to better interlocking and hence more stability

Procedure (Flakiness Index)
Flakiness Index: The flakiness index of aggregates is the percentage by weight of particles whose least dimension is less than three-fifths (0.6) of their mean dimension. Applicable to sizes>= 6.3 mm. 1.The sample is sieved through IS sieve sizes 63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3 mm 2. Minimum 200 pieces of each fraction to be tested are taken and weighed (W1 gm) 3. Separate the flaky material by using the standard thickness gauge. 4. The amount of flaky material is weighed to an accuracy of 0.1 percent of the test sample 5. If W1,W2,W3,…. are the total weights of each size of aggregates taken and w1,w2,w3,….. are the weights of material passing the different thickness gauges then: Flakiness Index = (w1+w2+w3+….)*100/(W1+W2+W3+….) = 100*w/W % Where, W = Total wt of material taken in gms, w = Total wt of material passing in gms

Elongation Index Elongation Index: The percentage by weight of particles whose greatest dimension is greater than one and four fifth times (1.8 times) their mean dimension. Applicable to sizes >=6.3 mm. Procedure: 1. The sample is sieved through sieve sizes, 50, 40, 25, 20, 16, 12.5, 10 and 6.3 2. Minimum 200 pieces of each fraction to be tested are taken and weighed (W1gm) 3. Separate the elongated material by using the standard length gauge 4. The amount of elongated material is weighed to an accuracy of 0.1 percent of the test sample 5. If W1,W2,W3,…. are the total weights of each size of aggregates taken and w1,w2,w3,….. are the weights of material retained on the different length gauge slots then: Elongation Index = (w1+w2+w3+….)*100/ (W1+W2+W3+….) = 100*w/W percent Where, W = Total wt of material taken in gms w = Total wt of material retained in gms

Angularity number The angularity number measures the percent voids in excess of 33 percent which is obtained in the case of the most rounded gravel particles. Ranges from 0-11 (rounded gravel-crushed angular). The cylinder is calibrated by determining the weight of water at 27oC required to fill it 2. Aggregate is sieved through 20, 16, 12.5, 10,6.3 and 4.75 mm IS sieves 3. About 10 kg of the predominant size should be available. 4. The sample of single-size aggregate is dried in an oven at 100oC to 110oC for 24 hours and then cooled 5. The scoop is filled with aggregate which is allowed to slide gently into the cylinder from the lowest possible height 6. The aggregate is filled in three layers, tamping each layer evenly 100 times with a tamping rod 7. After the third layer is tamped, the aggregates are struck off level with the help of tamping rod and surface finished 8. The aggregate with cylinder is now weighed to the nearest 5 g. The mean weight of aggregate is found.

Calculations and Observation Sheet
Angularity number = *W/C*G where, W = mean weight of aggregates in the cylinder, C = Weight of water required to fill the cylinder, G = Specific gravity of aggregate Discussion Elongated, flaky and angular materials decreases the workability of the mix, and not preferred in cement concrete. Angular aggregates are preferred in flexible pavement at WBM/WMM Angularity number ranges from zero for perfectly rounded aggregate (rounded pebbles) to about 11 percent for freshly crushed aggregates But for DBM & BC mix design may be modified to incorporate high angularity number.

Testing steel rod for tensile strength

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Thickness of flaky material is less than
Flakiness Index Test IS: 2386 part 1 Thickness of flaky material is less than 0.6 times mean size IS sieves: 63,50,40,31.5,25,20,16,12.5,10 and 6.3mm

Elongation gauge

Aggregate Impact test IS; 2386 part 4
material passing 12.5 mm sieve and retained on 10 mm sieve is placed in mould in 3 layers by tamping 25 times for each layer. After 15 blows, material passing 2.36 mm sieve is weighed and compared with sample weight in %. Mould

In a 250 ml cylinder pour damp sand duly shaking upto
200 ml mark. Fill cylinder with water sufficient to submerge sand fully and stir the sand well It can be seen that sand surface is below original level y Bulkage of sand=100(200-y)/y

Fill 200 ml jar up to 100 ml level with sand.
Silt content test Fill 200 ml jar up to 100 ml level with sand. Pour water up to 150 ml level and shake vigorously . Allow it for 3 hours Silt content = h/H х 100 H h

Test for Initial setting time
Vicat Apparatus Plunger for consistency: If penetration is 5 to 7 mm from bottom of mould (40mm), water added is of correct quantity for standard consistency. 1 mm square needle for IST: Initial setting time is time between addition of water to cement and when the needle ceases to penetrate completely (about 5 mm from bottom of mould). Needle with annular collar: Final setting time after water is added to cement and when needle makes an impression but not the collar on cement mould.

compressive strength in
Strength test on 70.6mm 1:3 cement mortar cubes to determine the grade of cement sand shall be as per IS:650 Grade number is 28 days’ compressive strength in Mpa or N/mm2 1Mpa=10.21 Kg/cm2

3 specimens of 150 mm cubes from the same concrete are to be tested for compressive strength
Cube after failure Average value of 3 specimens represent a sample result. If the results of 3 specimens show more than 15 % variation with average value, it be ignored

Testing steel rod for tensile strength

Water absorption < 20% Dry bricks for 4 hours at 100 to
Size, shape, free from cracks and sharp square edges. Bricks shall not break when dropped from 1m height, shall give ringing sound when struck with each other and leave no impression with finger nails Water absorption < 20% Dry bricks for 4 hours at 100 to 110º C, weigh,(W1) immerse in water for 24 hours at 27 ± 2º C and weigh again(W2) WA = (W1-W2) ÷ W1 х 100

Compressive strength Grind the 2 long faces, apply cement mortar, wrap with gunny bag for 24 hours, immerse in water for 3days. Measure the brick and place it in testing machine with 3mm plywood planks on top & bottom

Laboratory Tests on Construction materials

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