Laboratory Tests

1 EXPERIMENTAL  ILLUSTRATION OF EXAMPLE OF FLAKY  AND ELONGATION TEST FOR COARSE AGGREGATE.

• For 10mm sample
• Equipment required

1.    FLAKINESS TEST

• Flakiness guage
• IS Sieve of size 11, 6.3mm, and pan.
• Weighing machine, tray.
• PROCEDURE:-
• The sample should be in dry condition.
• Sieve should be cleaned before used.The sieves are shake by manually and period of time should not be less than 3 minutes.

FLAKINESS GUAGE

• On completion of sieving, the materials retained on sieve were weighed of taking sample of 200 No.
• Weight of sample after weighing = 112 gm.
• No. of aggregate passed in flakiness gauge = 125 no.
• Then the weight of passed aggregate in flakiness guage = 52gm.
• Therefore No. of %age of passed aggregate in flakiness guage, =(52/112*100)

=46.42%

• It is acceptable up to 30%

FIGURE SHOWING FINE COARSE AGGREGATE PASS THROUGH FLAKINESS GUAGE

(2) ELONGATION TEST:-

• Elongation guage
• IS sieve of size 11, 6.3mm and pan.
• Weighing machine , tray.
• PROCEDURE:-
• The sample should be in dry condition.
• Sieve should be cleaned before used.
• The sieves are shake by manually and period of time should not be less than three minutes.

ELONGATION GUAGE

• On completion of sieving the materials retained on sieve were weighed of taking sample o 200 No.
• Weight o sample after weighing =112gm.
• No. of aggregate retained on flakiness guage =44 no.
• Then the wt. of retained aggregate on flakiness guage = 34 gm.
• Therefore ,no. of %age of passed aggregate in flakiness guage,
• =(34/112*100) = 30.35%
• It is acceptable up to 30%.

2 EXPERIMENTAL ILLUSTRATION OF A TYPICAL EXAMPLE TO CALCULATE THE MOISTURE CONTENT OF SAND.

• It is defined as the ratio of the weight of water to the weight of the dry soil grains in a soil mass.
• Equipment Required:-thermostatically controlled oven at temperature between (100 – 110) deg.c, accurate and readable balance.
• Let us have an example:-
• Take sample:-
• Wet = 550 gm
• Dry = 510gm
• Calculation of moisture content
• = (wet weight – dry weight) / dry weight*100
• = (550-510) /510*100 => 7.84%

                       

 THERMOSTATICALLY CONTROLLED OVEN

3 EXPERIMENTAL ILLUSTRATION OF A TYPICAL EXAMPLE OF SIEVE ANALYSIS OF FINE AGGREGATE.

• Sieve analysis helps us to determine the particle size distribution of fine aggregates which is important to find out whether the aggregate is good for mix or not. It is used to determine the grading, fineness modulus, an index to the fineness, coarseness and uniformity of aggregates.
• Equipment required: IS sieve, sieve shaker, weigh balance

                                 

                                                     MECHANICAL SEIVE SHAKER

                                                                                                      

• TEST PROCEDURE:-
• The sample should be in dry condition.
• Sieve should be cleaned before used.
• Sieve of sizes 4.75mm, 2.36mm, 1.18mm, 0.600mm, 0.300mm, 0.150mm were used.
• The sieve shake by mechanical sieve shaker and period of time should not be less than 3 minutes.
• On completion of sieving , the materials retained on each sieve were weighed.
• A typical example to work out F.M (fineness modulus) of sand is illustrated below:-
• Take sample of 1000 gms of badarpur sand.

I.S sieve designation	Wt. of sample taken	Wt. retained on sieve in gms.	Wt. passed in sieve in gms.	%age passing by weight.	%age retained.	Cumulative %age retained.
10mm	1000gms of badarpur sand	----	1000	100%	0	0
4.75mm		33	967	96.7%	3.3%	3.3%
2.36mm		72	895	89.5%	10.5%	13.8%
1.18mm		105	790	79.5%	21.0%	34.8%
600 micron		224	566	56.6%	43.4%	78.2%
300 micron		345	221	22.1%	77.9%	156.10%
150 micron		197	24	2.4%	97.6%	253.70%

Therefore Fineness Modulus = >( 253.70 /100) =2.53

4 EXPERIMENTAL ILLUSTRATION OF TYPICAL EXAMPLE TO  CALCULATE THE FINENESS MODULUS (F.M.) OF SAND.

• F.M is a numerical index of fineness, giving some idea about the mean size of particles in the aggregates .The fineness modulus (F.M) varies between 2.0 and 3.5 for fine aggregate and 5.5 to 8.0 for coarse aggregate.Aggregates, whose F.M is required, is placed on a standard set of sieves(80, 63, 40, 20, 12.5, 10, 4.75, 2.36, 1.18, 0.600, 0.300, 0.150)mm  and the set is vibrated. The material retained on such sieve after sieving represent the fraction of aggregate coarser than the sieve in question but finer than the sieve above

MECHANICAL SEIVE SHAKER

• The sum of the cumulative percentages retained on the sieves divided by 100 gives the F.M
• A typical example to work out F.M of sand is illustrated below:-

Material:- coarse sand

I.S seive	Wt. retained in gram	Commulative wt. in gram	% wt. retained	% cumulative weight retained	% passing	% allowable	Remarks
4.75mm	-	31	-	6.2	93.8	90-100	-
2.36mm	-	83	-	16.6	83.4	75-100	-
1.18mm	-	147	-	29.4	70.4	55-90	-
.600mm	-	217	-	43.4	56.6	35-59	-
.300mm	-	345	-	69	31	8-30	-
.150mm	-	475	-	95	5	0-10	-
.075mm	-	-	-	-	-		-
pan	-	500	-	100	0		-

• Fineness Modulus (F.M) =  cumulative % of sand retained/100
• =(6.2+16.6+29.4+43.4+69+95)/100
• =2.569

5 EXPERIMENTAL ILLUSTRATION OF TYPICAL EXAMPLE TO CHECK THE TENSILE STRENGTH OF STEEL BAR.

• The purpose of performing the test is to determine the tensile strength of steel.
•   EQUIPMENT REQUIRED:- Measuring tape, weighing machine,bars, universal testing machine. (UTM)
• Limitation:
• It works for tension aswell as compression.
• Capacity – 1000KN.
•  Check the tensile strength of steel of diameter up to 40mm.

                                  Types of steel test

a.       Physical test.

b.      Chemical test.

                                          Types of physical test                 

             a.       Check for tensile strength.

             b.      Check for bent and re-bent.

             c.       Check for unit weight.

• Formula required:

            1)      Area = w(kg)/((.00785)*L)(mm)

            2)      Strength = load(KN)/Area(mm2)

• Passing limits = 545N/mm2(minimum)
• Taking sample

         a.   Length of bar— 1.075m.

             b.  Diameter of bar – 16mm

            c. Weight – 1.78kg.

         d. Taking Fe 500 tmt bar of SAIL.

         e.  Note—Generally breaking point of 16mm diameter of bar is 110KN.

         f.  In case of coupler welding is required minimum 125% of limit value is taken (545N/mm2).

6 EXPERIMENTAL ILLUSTRATION OF TYPICAL EXAMPLE  OF SILT ANALYSIS OF SAND.

•  The purpose of performing the test is to determine the % of silt content in sand.
•  Equipment required:250ml measuring cylinder,tray, water,etc.
•  First of all take the measuring cylinder and also the sample of sand and it inserted in the measuring jar.
• Water is added as per requirement and temperature of water should be 27*c.
• Iodine is added or better setting time.
•  The jar shake slowly.
• After 15 minutes different layer of the actual sand, silt and water have been seen.
• Calculation of silt content: Height of silt divided by the total sand filled height and multiply by 100 for %
• Least count should be 2, reading = 6
• (6/100*100) = 6%
• NOTE: on site, If the value is more than 8%, then it is not acceptable.

MEASURING CYLINDER

7 EXPERIMENTAL ILLUSTRATION OF A TYPICAL EXAMPLE OF A SLUMP TEST

• The slump test is used to ensure uniformity for different batches of similar concrete under field conditions and to ascertain the effects of plasticizers on their introduction.
• This test is very usefull on site as a check on the day to day or hour to hour variation in the materials being ed into the mixer.An increase in slump may mean that the moisture content of aggregate has unexpectedly increased.
• Too high or too low slump gives immediate warning and enables the mixer operator to remedy the situation.
• APPARATUS REQUIRED:

1)    Slump cone,

2)    Scale for measurement,

3)    Temping rod (steel)

• PROCEDURE:

1)    The mold for a slump test is a frustum of a cone ,300mm (12in) of height. The base is 200 mm(8in)in diameter and it has a smaller opening at the top of 100mm (4in).

2)    The base is placed on a smooth surface and the container is filled with concrete in three layers, whose workability is to be tested.

3)    Each layer is tampered 25 times with a standard 16mm(5/8in) dia steel rod, rounded at the end.

4)    When the mould is completely filled with concrete,the top surface is struck off(leveled with mold top opening)by means of screaning and rolling motion of the temping rod.

5)    The mold must be firmly held against its base during the entire operation so that it could not move due to the pouring of concrete and this can be done with the means of handles or foot-rests brazed to the mould.

6)    Immediately after filling is completed and the concrete is leveled,the cone is slowly and carefully lifted vertically,an unsupported concrete will now slump.

7)    The decrease in the height of the centre of the slumped concrete is called slump.

8)    The slump is measured by placing the cone just besides the slump concrete and the tempting rod is placed over the cone so that it should also come over the area of slumped concrete.

9)    The decrease in height of concrete to that of mold is noted with scale (usually measured to nearest 5mm(1/4 in)).

10)    The slumped concrete takes various shapes like collapse, shear, and true slump.

Degree of workability	Slump (mm)	Slump(in)	Compacting factor	Use for which concrete is suitable
Very low	0-25	0-1	0.78	Very dry mixes,used in road making
Low	25-50	1-2	0.85	Low workability mixes used for foundations with light R/F
Medium	50-100	2-4	0.92	Medium workability mixes, manually compacted flat slabs using crushed aggregates.normal R/F concrete manually compacted and heavily R/F sections with vibrations.
High	100-175	4-7	0.95	High workability concrete or sections with congested R/F not normally suitable for vibration.

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PRECAUTIONS:-

In order to reduce the influence on the slump of the variation in the surface friction, the inside of the mould and its base should be moistened in the beginning  of every test, and prior to lifting of the mould the area immediately around the base of the cone should be cleaned from concrete which may have dropped accidentally.