VARIOUS LAB AND SOIL TESTS ...

WATER CONTENT OF SOIL BY CALCIUM CARBIDE METHOD

Water Content of soil is the quantity of soil contained in a sample of soil. Generally this is expressed in ratio.

Here : s-soil (dry), v-void (pores filled with water or air), w-water, a-air. V is volume, M is mass.
Volumetric Water Content is defined by

where V_w is the volume of water and V_T = V_s + V_v = V_s + V_w + V_a is the total volume (that is soil volume + water volume + air space).
Gravimetric water content is expressed by mass (weight) as follows:

where m_w is the mass of water and m_t is the bulk mass. The bulk mass is taken as the total mass, except for geotechnical and soil science applications where oven-dried soil (m_s, see the diagram) is conventionally used as m_t
   We can determine the water content in soil by calcium carbide method as per IS: 2720 (Part II) - 1973.

PRINCIPLE
     It is a method for rapid determination of water content from the gas pressure developed by the reaction of calcium carbide with the free water of the soil. From the calibrated scale of the pressure gauge the percentage of water on total mass of wet soil is obtained and the same is converted to water content on dry mass of soil.

APPARATUS

     i) Metallic pressure vessel, with a clamp for sealing the cup, alongwith a gauge calibrated in percentage water content.
     ii) Counterpoised balance, for weighing the sample
     iii) Scoop, for measuring the absorbent (Calcium Carbide)
     iv) Steel balls - 3 steel balls of about 12.5mm dia. and 1 steel ball of 25mm dia.
     v) One bottle of the absorbent (Calcium Carbide)

PREPARATION OF SAMPLE      Sand - No special preparation. Coarse powders may be ground and pulverized.
     Cohesive and plastic soil - Soil is tested with addition of steel ball in the pressure vessels.
     The test requires about 6g of sample.

PROCEDURE      i) Set up the balance, place the sample in the pan till the mark on the balance arm matches with the index mark.
     ii) Check that the cup and the body are clean.
     iii) Hold the body horizontally and gently deposit the levelled, scoop-full of the absorbent (Calcium Carbide) inside the chamber.
     iv) Transfer the weighed soil from the pan to the cup.
     v) Hold cup and chamber horizontally, bringing them together without disturbing the sample and the absorbent.
     vi) Clamp the cup tightly into place. If the sample is bulky, reverse the above placement, that is, put the sample in the chamber and the absorbent in the cup.
     vii) In case of clayey soils, place all the 4 steel balls (3 smaller and 1 bigger) in the body alongwith the absorbent.
     viii) Shake the unit up and down vigorously in this position for about 15 seconds.
     ix) Hold the unit horizontally, rotating it for 10 seconds, so that the balls roll around the inner circumference of the body. 
     x) Rest for 20 seconds.
     xi) Repeat the above cycle until the pressure gauge reading is constant and note the reading. Usually it takes 4 to 8 minutes to achieve constant reading. This is the water content (m) obtained on wet mass basis. 
     xii) Finally, release the pressure slowly by opening the clamp screw and taking the cup out, empty the contents and clean the instrument with a brush.

REPORTING OF RESULTS
     The water content on dry mass basis,

AGGREGATE IMPACT VALUE TEST

    With Respect to concrete aggregates,toughness is usually considered the resistance of the material to failure by impact.Several attempts to develop a method of test for aggregates impact value have been made.The most successful and known test is described below..

APPARATUS
i) Impact testing machine conforming to IS: 2386 (Part IV) - 1963
ii) IS Sieves of sizes - 12.5mm, 10mm and 2.36mm
iii) A cylindrical metal measure of 75mm dia. and 50mm depth
iv) A tamping rod of 10mm circular cross section and 230mm length, rounded at one end
v) Oven

PREPARATION OF SAMPLE
i) The test sample should conform to the following grading:
- Passing through 12.5mm IS Sieve 100%
- Retention on 10mm IS Sieve 100%
ii) The sample should be oven-dried for 4hrs. at a temperature of 100 to 110^oC and cooled.
iii) The measure should be about one-third full with the prepared aggregates and tamped with 25 strokes of the tamping rod.A further similar quantity of aggregates should be added and a further tamping of 25 strokes given. The measure should finally be filled to overflow, tamped 25 times and the surplus aggregates struck off, using a tamping rod as a straight edge. The net weight of the aggregates in the measure should be determined to the nearest gram (Weight 'A').

PROCEDURE i) The cup of the impact testing machine should be fixed firmly in position on the base of the machine and the whole of the test sample placed in it and compacted by 25 strokes of the tamping rod.
ii) The hammer should be raised to 380mm above the upper surface of the aggregates in the cup and allowed to fall freely onto the aggregates. The test sample should be subjected to a total of 15 such blows, each being delivered at an interval of not less than one second.

REPORTING OF RESULTS i) The sample should be removed and sieved through a 2.36mm IS Sieve. The fraction passing through should be weighed (Weight 'B'). The fraction retained on the sieve should also be weighed (Weight 'C') and if the total weight (B+C) is less than the initial weight (A) by more than one gram, the result should be discarded and a fresh test done.
ii) The ratio of the weight of the fines formed to the total sample weight should be expressed as a percentage.

Aggregate impact value = B/A x 100%

iii) Two such tests should be carried out and the mean of the results should be reported.

A sample proforma for the record of the test results is given below..

    As per IS 283-1970 aggregate  impact value shall no exceed 45% by weight for aggregates used for concrete other than wearing surface and 30% for concrete of wearing surfaces (Run ways,Roads & Pavements)

Soundness Test of Cement

      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 the set and hardened mass.This will cause serious difficulties for the durability of structures when such cement is used.This test is to ensure that cement does not show any appreciable subsequent expansion is of prime importance.

     The unsoundness in cement is due to the presence of excess of lime than that could be combined with acidic oxide at the kiln.This is also due to inadequate burning of insufficiency in fineness of grinding or through mixing of raw materials.It is also likely that too high a proportion of magnesium content or calcium sulphate content may cause unsoundness in cement. For this reason the magnesia content allowed in cement is limited to 6%.

APPARATUS i) The apparatus for conducting the Le-Chatelier test should conform to IS: 5514 - 1969
ii) Balance, whose permissible variation at a load of 1000g should be +1.0g
iii) Water bath

PROCEDURE i) The mould is placed on a glass sheet and it is filled with the cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency.
ii) Then the mould is covered with another piece of glass sheet, a small weight is placed on its covering glass sheet and immediately the whole assembly is submerged in water at a temperature of 27 ± 2^oC and kept it there for 24hrs.
iii) The distance separating the indicator points to the nearest 0.5mm is measured (say d _l ).
iv) The mould is submerged again in water at the temperature prescribed above.The water is bought to boiling point in 25 to 30 minutes and it is boiled for 3hrs.
v) Then  the mould is removed from the water, allowed to cool.The distance between the indicator points is measured (say d ₂ ).
vi) (d ₂ – d _l) represents the expansion of cement.

REPORTING OF RESULTS     The mean of the two values to the nearest 0.5mm to represents the expansion of cement.

Bitumen Content Test

AIM
To determine the bitumen content as per ASTM 2172.

APPARATUS

i) Centrifuge extractor
ii) Miscellaneous - bowl, filter paper, balance and commercial benzene
SAMPLE Take 500g sample

PROCEDURE
i) If the mixture is not soft enough to separate with a trowel, place 1000g of it in a large pan and warm upto 100^oC to separate the particles of the mixture uniformly.
ii) Place the sample (Weight ‘A’) in the centrifuge extractor. Cover the sample with benzene, put the filter paper on it with the cover plate tightly fitted on the bowl.
iii) Start the centrifuge extractor, revolving slowly and gradually increase the speed until the solvent ceases to flow from the outlet.
iv) Allow the centrifuge extractor to stop. Add 200ml benzene and repeat the procedure.
v) Repeat the procedure at least thrice, so that the extract is clear and not darker than the light straw colour and record the volume of total extract in the graduated vessel.
vi) Remove the filter paper from the bowl and dry in the oven at 110 + 5^oC. After 24hrs., take the weight of the extracted sample (Weight ‘B’).

REPORTING OF RESULTS

Repeat the test thrice and average the results.

Testing of Cement

Testing of Cement can be brought under two categories.
      (a) Field Testing        (b) Laboratory Testing

Field Testing
       It is sufficient to subject the cement to field tests when it is trusted for minor works. The following are the field tests.
(a) Open and the bag and take a good look at the cement. There should not be any visible lumps. The colour of the cement should normally be greening grey.
(b) Thrust your hand into the cement bag. It must give a cool feeling. There should not be any lump inside.
(c) Take a pinch of cement and feel between fingers. It should give a smooth and not a gritty feeling.
(d) Take a handful of cement and through it in to a bucket full of water, the particles should float for some time before they sink.
(e) Take about 100 grams of cement and a small quantity of water and make a stiff paste. From the stiff paste , pat a cake with sharp edges. Put it on a glass plate and slowly take it under water with a bucket.See the shape of the cake is not disturbed while taking it down the bottom of the bucket. After 24 hours the cake should retain its original shape and at the same time it should also set and attain some strength. 
      If a sample of cement satisfies the above field tests it may be concluded that the cement is not bad.The above tests does not really indicates that the cement is really good for important works. For using cement in important and major works it is incumbent on the part of the user to test the cement in the laboratory to confirm the requirements of the Standard Specifications with respect to its physical and chemical properties.The tests which are usually conducted in the Lab to confirm those properties are …

INITIAL AND FINAL SETTING TIME OF CEMENT

Initial and Final Setting Time are two very important properties of  cement which are required  in estimating free time for transporting, placing, compaction and shaping of cement paste.

Initial setting time is the time from mixing dry cement with water till the beginning of interlocking of the gel.
Final setting time is the time from mixing dry cement with water till the end of interlocking of the gel

AIM
To determine the initial and the final setting time of cement as per IS: 4031 (Part 5) - 1988.

APPARATUS

i) VICAT Apparatus.
ii) Digital weighing scale, used to measure the weight of dry cement.
iii) Glass graduates, used to measure the volume of water.
iv) Trowel.
v) Mixing bowl.
vi) Stop-watch.
vii) Portland Pozzolna Cement.
viii) Water.
PROCEDURE
i) Prepare a cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consistency.
ii) Start a stop-watch, the moment water is added to the cement.
iii) Fill the Vicat mould completely with the cement paste gauged as above, the mould resting on a non-porous plate 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.

A) INITIAL SETTING TIME
Place the test block under the rod bearing the needle.Lower the needle gently in order to make contact with the surface of the cement paste and release quickly, allowing it to penetrate the test block. Repeat the procedure till the needle fails to pierce the test block to a point 5.0 ± 0.5mm measured from the bottom of the mould.The time period elapsing between the time, water is added to the cement and the time, the needle fails to pierce the test block by 5.0 ± 0.5mm measured from the bottom of the mould, is the initial setting time.

B) FINAL SETTING TIME
Replace the above needle by the one with an annular attachment. The cement should be considered as finally set when, upon applying the needle gently to the surface of the test block, the needle makes an impression therein, while the attachment fails to do so. The period elapsing between the time, water is added to the cement and the time, the needle makes an impression on the surface of the test block, while the attachment fails to do so, is the final setting time.

REPORTING OF RESULTS
The results of the initial and the final setting time should be reported to the nearest five minutes.

CONCLUSION:
To measure the setting times of cement, we have to do our tests on cement of standard consistency. Normal consistency of standard cement can be gained by using the W \ C ratio and depending on 26%- 33%. The higher rate of water the more initial setting time needed.

U-Box Test

       Like L-box test, U-box test measures the filling ability of self-compacting concrete. The U-box test originally developed in Japan and is sometimes referred to as the box-shaped test. Like other workability tests for self-compacting concrete, the U-box test is also applicable to highly flowable concretes and underwater concretes.

APPARATUS
        As shown in Figure the apparatus consists of a  U-shaped box. Concrete is placed in the left side of the box. An alternative version of the apparatus features a flat bottom instead of a curved bottom. Ideally, the box should be made of clear plastic to permit the observation of the concrete in the box. To start the test, the door dividing the two halves of the box is opened and concrete is allowed to flow from the left half of the box into the right half. Reinforcing bars are placed at the location of the door. Although the spacing of the bars is adjustable, the most common arrangement is 13 mm diameter bars with a clear spacing of 35 mm. The time from the opening of the door until the concrete ceases to flow is recorded. The height of the concrete in each side of the box is measured. A truly self-leveling fluid will rise to the same height on each side of the box. Concrete with good filling ability should reach a height of at least 30 cm on the right side of the box. In some versions of the test, a surcharge load is applied to the concrete on the left side of the box. This surcharge load is unnecessary for self-compacting concrete and is generally not used.
       With both the L-box and U-box tests, it is unknown what significance the effect of friction between the concrete and the walls has on the test results.

L-Box Test

      The L-box test is used to  measure the filling and passing ability of self-compacting concrete.This test was originally developed in Japan for underwater concrete, the test is also applicable for highly flowable concrete. 
        The apparatus consists of an L-shaped box, shown in Figure below. Concrete is initially placed in the vertical portion of the box, which measures 600 mm in height and 100 mm by 200 mm in section. A door between the vertical or horizontal portions of the box is opened and the concrete is allowed to flow through a line of vertical reinforcing bars and into the 700 mm long, 200 mm wide, and 150 mm tall horizontal portion of the box. In the most common arrangement of reinforcing bars, three 12 mm bars are spaced with a clear spacing of 35 mm. Generally, the spacing of the reinforcing bars should be three times the maximum aggregate size. It should be noted that various dimensions for the L-box have been used and no one set of dimensions is considered official; however, the dimensions described above seem to be the most common.

     The time for concrete to reach points 20 cm (T₂₀) and 40 cm (T₄₀) down the horizontal portion of the box is recorded. After the concrete comes to rest in the apparatus, the heights of the concrete at the end of the horizontal portion, H2, and in the vertical section, H1, are measured. The blocking ratio, H₂/H₁, for most tests should be 0.80 to 0.85. If the concrete being tested is truly self-leveling, like water, the value of the blocking ratio will be unity. Segregation resistance can be evaluated visually. A concrete sample with coarse aggregate particles that reach the far end of the horizontal part of the box exhibits good resistance to segregation. The L-box can be disassembled after the concrete has hardened. By cutting out samples of the hardened concrete, additional information about the concrete’s resistance to segregation can be determined, as shown by Tanaka et al. (1993).
        While the test does give valuable information about filling and passing ability, and to a lesser extent, segregation resistance, the test is not as simple as the slump flow test. Since there are no standardized dimensions, results from different test apparatuses cannot be compared directly.

 

Powers Remolding Test

      The Powers remolding test (Powers 1968; Scanlon 1994; Wong et al. 2000) is similar to the Vebe consistometer. The test was develop by Powers and first presented in 1932. The test has been standardized by the US Army Corp of Engineers as CRD C6-74.
       The test apparatus consists of a 12 inch diameter cylindrical mold mounted on a standard drop table, described in ASTM C124 (which was withdrawn in 1973). A separate 8 ¼ inch diameter ring is attached at the top of the cylinder, as shown in Figure below. The concrete sample is compacted in the standard slump cone inside of the inner ring. Like the Vebe consistometer, a clear plate attached to a vertical stem rests on top of the concrete. The number of drops required to remold the concrete to the shape of the outer cylinder is a measurement of the “remolding effort.” The ring attached to the outer cylinder restricts the movement of the concrete and allows for the determination of the plastic shear capacity of the concrete mix. A mix with high shear capacity easily passes under the ring, whereas mixes with low shear capacity tend to clog and result in greater required remolding effort. It is possible that two mixes that require the same remolding effort when the ring is removed require different remolding efforts when the ring is in place. Research has shown that the Powers remolding test is more sensitive to changes in workability than the slump test (Scanlon 1994).

Advantages:
• The Powers remolding test is a dynamic test and is suitable for low slump concretes.
• The results of the test are obtained directly.
Disadvantages: • The drop table must be mounted on an object of sufficient mass to absorb vibrations created by the drop table. Accordingly, the device is likely to be too large and bulky for field use.
• The test method is only suitable for low slump concretes.
• No analytical treatment or experimental testing of the test method has been performed to relate the test results to yield stress and/or plastic viscosity

Delivery-Chute Torque Meter

       The delivery-chute torque meter (US patent 4,332,158; Wong et al. 2000) is designed to measure the consistency of concrete as it exits a concrete mixing truck. The intent of the device is to measure slump accurately without having to wait for the conventional slump test to be performed.
      The hand-held device, which is shown in Figure 7, is inserted in flowing concrete in the delivery chute of a concrete mixing truck. The two curved sensing blades are attached to a vertical member that measures torque. The device is inserted in the delivery chute such that the sensing blades are orthogonal to the flow of concrete. The flowing concrete applies approximately
equivalent forces to each of the two sensing blades. These forces create opposing moments on the inner vertical member. Since the length of the moment arm for the right sensing blade is approximately twice that of the moment arm for the left sensing blade, a net torque is applied to the inner vertical member. The operator manually applies an opposing torque to the outer housing to keep the blades orthogonal to the flow of concrete. The magnitude of this applied torque is indicated on the flat circular plate located just above the two sensing blades. The torque measured with the device is correlated to slump, with the appropriate correlation marked on the circular plate. For concretes with different viscosities, different calibrations must be obtained. The geometry of the device allows the device to adjust automatically to changes in flow velocity and height.

Advantages:
• The device measures the workability of the concrete as it exits the mixer before it is placed.
• The torque (and associated slump) is read directly from the device. No computer or other sensing devices are required to determine slump.
Disadvantages: • The torque meter is a single-point test that gives no indication of plastic viscosity. Readings are made at only one shear rate.
• The device must be calibrated for each concrete mixture.

Angles Flow Box Test

       The Angles flow box test (Scanlon 1994; Wong et al. 2000) attempts to simulate typical concrete construction in order to characterize the ease with which concrete can be placed. The test measures the ability of concrete to flow under vibration and to pass obstructions.
        The device consists of a rectangular box mounted on a vibrating table. Two adjacent vertical partitions are placed in the middle of the box to divide the box in half. The first partition consists of a screen of circular bars that are spaced so that the openings between the bars are the size of the maximum aggregate. The second partition is a solid, removable plate that initially holds concrete on one side of the box prior to the beginning of the test. After concrete has been loaded on one side of the box, the solid partition is removed and the vibrating table is started. The time for the concrete to pass through the screen and form a level surface throughout the box is recorded. The amount of bleeding and segregation that occurs during vibration can be observed visually. 
         Very little data is available on the validity of the test and on interpretation of the test results. The test method would not be appropriate for very low slump mixes. For highly flowable concrete mixtures, vibration may be unnecessary. A similar concept is used to test the workability of selfcompacting concrete.
Advantages:
• The test method represents actual field conditions. It is a dynamic test that subjects  concrete to vibration.
• The ability of concrete to pass obstructions and resist segregation is assessed.
Disadvantages:
• The test is bulky and would probably not be appropriate for field use.
• The test result is likely a function of both yield stress and plastic viscosity, although these  values are not directly recorded.

CEMAGREF-IMG

      The CEMAGREF-IMG (Ferraris and Brower 2001) is a large coaxial-cylinders rheometer originally developed to measure mud-flow rheology, but which has also been used to measure concrete rheology. Only one prototype of the device exists.
       Since the CEMAGREF-IMG was not initially intended to measure the rheology of concrete, it is significantly larger than other rheometers. In fact, the large size of the device makes it impractical for measuring concrete. The outer cylinder is 120 cm in diameter and 90 cm tall, while the inner cylinder is 76 cm in diameter. The rheometer holds 500 liters of concrete and is mounted on a trailer. The inner cylinder rotates and measures torque while the outer cylinder
remains stationary. Blades on the outer cylinder and a metallic grid on the inner cylinder reduce concrete slippage. Since the inner cylinder is mounted within the outer cylinder from the bottom instead of from the top, a rubber seal is provided at the base of the inner cylinder to ensure that all concrete remains within the gap between the cylinders. The torque on the inner cylinder at various rotation speeds is logged and used to calculate yield stress and plastic viscosity.
        Although the large dimensions of the CEMAGREF-IMG allow the testing of concrete mixtures with large maximum aggregate sizes, the ratio of the outer radius to the inner radius is too large. As a result, plug flow occurs as the concrete near the inner cylinder is sheared while the shear stress applied to the concrete near the outer cylinder is insufficient to overcome the yield stress
of the concrete. The large size of the CEMAGREF-IMG also makes the device impractical to transport.
Advantages:
• The device measures yield stress and plastic viscosity.
• The size of the device accommodates large maximum aggregate sizes.
Disadvantages:
• The device was not originally designed to measure concrete and is too large for common field use.
• The geometry of the device should be improved to more accurately measure concrete rheology.
• The seals at the bottom of the inner cylinder must be replaced periodically and must be accounted for in the device’s calibration.

Vibrating Slope Apparatus (VSA)

      Originally developed in the 1960s, the vibrating slope apparatus (Wong et al. 2000) was recently modified by the US Army Engineering Research and Development Center (ERDC) for the US Federal Highway Administration (FHWA). The device measures the workability of low slump concretes subjected to vibration at two different shear rates in order to determine a “workability
index” that is related to plastic viscosity and a “yield offset” that is related to yield stress. Researchers at the ERDC selected the vibrating slope apparatus over twenty other workability test devices as a superior choice to measure the workability of low slump concretes in the field.
       The vibrating slope apparatus as modified by the US Army Engineering Research and Development Center is shown in Figure 15. Concrete to be tested is placed in the chute, which can be set at a predefined angle. Three load cells continuously measure the mass of concrete in the chute during the test. Small transverse metal strips reduce slip between the concrete and the
bottom of the chute. A vibrator is mounted to the bottom of the chute. Eight vibration dampers ensure that the vibration is applied to the concrete and that the entire apparatus does not excessively vibrate and interfere with load cell measurements. Readings from the load cells are transmitted to a laptop computer, where the workability index and yield offset are calculated. The entire apparatus is designed to be rugged and easily portable.

      To operate the device, concrete is placed in the chute, which is set at a predefined angle (typically 10-15 degrees). The gate is opened and the vibrator is started, allowing concrete to fall from the chute into a bucket. The data from the load cells is used to calculate the discharge rate. Since the discharge rate generally decreases as concrete flows out of the chute, the maximum discharge rate is recorded. The test procedure is repeated a second time for a different incline angle. The results of the test are plotted as a graph of maximum discharge rate versus discharge angle. The straight line connecting the two data points is defined by Equation [1]:

                                                  R = WA + C                                                     [1]
where R = maximum discharge rate, W = workability index, A = discharge angle, and C = calculated yield offset.

        The intent of the research conducted by the ERDC for the FHWA was simply to determine if the vibrating slope apparatus would operate properly, not whether the device could accurately measure concrete rheology. The results of the preliminary ERDC laboratory testing were compared only to the slump and air content of each concrete mixture. Further, no analytical treatment of the test has been presented. Wong et al. (2000) claims that the y-intercept of the discharge rate versus discharge angle plot is the yield stress and that the slope of this plot is the dynamic viscosity; however, no effort is made to relate these parameters to fundamental units or confirm the validity of the test results. Since the yield stress of vibrated concrete is lower than the yield stress of unvibrated concrete, the yield stress recorded by the vibrating slope apparatus is not equivalent to the yield stress of the unvibrated concrete and is only applicable for the specific vibration applied by the vibrating slope apparatus. Before the vibrating slope apparatus can be used on a wider basis, the validity of the test results must be verified.
        The ERDC researchers encountered multiple problems in developing the vibrating slope apparatus prototype. Many of the problems were trivial and easily corrected. Other problems will require further work to resolve. The test device is large, bulky, and weighs 350 pounds. The ERDC researchers give no cost information in their report and do not compare the cost effectiveness of the vibrating slope apparatus to other test methods.

Advantages:
• Unlike many rheometers, the device measures the workability of low slump concretes.
• The results of the device are given in terms of parameters related to yield stress and
plastic viscosity.
• The device is designed to be rugged for field use.
Disadvantages:
• The results of the device have not been verified analytically or experimentally.
• The device is large, bulky, and heavy.
• Although the researchers have proposed using an embedded electronic device to record test data, the vibrating slope apparatus at this point still requires a notebook computer.
• The results of the test are only applicable for conditions with the same vibration as the vibration applied by the device.
• The shear rate is non-uniform throughout the test. The shear rate decreases as the mass of concrete in the chute decreases.

Vebe Consistometer

       The Vebe consistometer (Bartos 1992; Scanlon 1994; Bartos, Sonebi, and Tamimi 2002) measures the remolding ability of concrete under vibration. The test results reflect the amount of energy required to remold a quantity of concrete under given vibration conditions. The Vebe consistometer is applicable to concrete with slumps less than 2 inches.
       The apparatus, shown in Figure below, consists of a metal cylindrical container mounted on a vibrating table, which produces a sinusoidal vibration. In the version of the test standardized in Europe as EN 12350-3, a slump cone is placed in the center of the cylinder and filled in the same manner as in the standard slump test. After the slump cone is removed, a clear plastic disk is set
atop the fresh concrete. The Vebe table is started and the time for the concrete to remold from the slump cone shape to the shape of the outer cylindrical container is recorded as a measure of consistency. The sliding clear plastic disk facilitates the determination of the end of the test.

 

      Juvas (1994) has presented a modified Vebe test to more efficiently measure low slump concretes that exhibit standard Vebe times greater than 30 seconds. In the modified Vebe test, a 20 kg surcharge is attached to the rod above the clear plastic disk. The remainder of the test apparatus and procedure is unchanged. The modified Vebe test more closely represents the production of precast concrete elements that are both vibrated and pressed.
       ASTM C1170 describes two variations on the procedure described above for use with rollercompacted concrete. Instead of placing concrete in a slump cone in the cylinder, concrete is placed directly into the 9 ½-inch diameter, 7 ¾-inch tall cylinder without compaction. For Test Method A, a 50 pound surcharge is placed on the sliding plastic disk. The vibrator is started and the time for the concrete to consolidate and a mortar ring to form around the plastic disk is recorded. The surcharge is then removed and the concrete is vibrated further until the total vibration time is 2 minutes. The density of the consolidated concrete in the mold is then determined. When the Vebe time by Test Method A is less than 5 seconds, Test Method B should be used. In Test Method B, the surcharge is not used. Both the time for a mortar ring to form around the perimeter of the cylinder and the final density of the compacted concrete are recorded. Both methods are applicable for concretes with maximum aggregate sizes up to 2 inches. A minimum of 50 pounds of concrete is required for each test method.
     Since the test apparatus is large and heavy, it is inappropriate for field use. The vibrating table must be mounted on a large and stable base of sufficient mass to absorb the table’s vibrations. The main use for the test has been in the laboratory and in the precast industry, where low slump concrete mixes are commonly used (Bartos 1992). The apparatus is neither directly related to slump nor plastic viscosity.

Advantages:
• The Vebe consistometer is a dynamic test and can be used on concretes that are too dry for the slump test.
• The test device is standardized in ASTM and identified by ACI Committee 211 (2002) in its guide for proportioning low slump concrete.
• Test results are obtained directly.
Disadvantages: • Due to the need to ensure that all vibration is kept within the test device, the size of the test device makes the Vebe consistometer generally unsuitable for field use.
• The test device only works for low slump concretes.
• No analytical treatment of the test method has been developed. Such treatment would be complex because the shear rate declines during the duration of the test as the concrete specimen changes shape.

Surface Settlement Test

    The surface settlement test (Bartos, Sonebi, and Tamimi 2002) is used to assess the stability of concrete by measuring the settlement of fresh concrete over time. The test is most appropriate for highly fluid and self-compacting concretes; however, it can be used for moderate slump concrete mixtures.
     The test apparatus consists of an 800 mm tall, 200 mm diameter pipe sealed at the bottom. Two longitudinal seams allow the pipe to be removed once the concrete sample has hardened. To perform the test, concrete is filled to a height of 700 mm in the cylinder. Highly fluid and self compacting concretes do not need to be consolidated; however, rodding or vibration is necessary for less fluid concretes. A 4 mm thick, 150 mm diameter acrylic plate is placed on the top surface of the concrete. Four 75 mm long screws extend downward from the acrylic plate and into the concrete. A linear dial gauge or linear variable differential transformer (LVDT) is used to measure the settlement of the acrylic plate over time until the concrete hardens. The top of the pipe is covered during the test to prevent evaporation. In addition to a plot of surface settlement versus time, the maximum surface settlement versus initial concrete height is computed.

Advantages:
• The test is inexpensive and simple to perform.
• The test is appropriate for a wide range of concrete mixtures.
Disadvantages:
• The test does not give a direct result.
• The time required to perform the test is substantially longer than other test methods because the settlement distance must be recorded until the concrete hardens.

Ring Penetration Test

     The ring penetration test consists of a steel ring that is allowed to sink under its own weight into a sample of fresh concrete. To perform the test, mass can be gradually added to the ring until the ring begins to settle into the concrete. The total mass on the ring when the ring begins to penetrate the concrete is related to yield stress. The rate at which the ring settles when a constant mass is present on the ring can also be measured. The method is considered appropriate for grouts and high-workability concretes.

Advantages:
• The ring penetration test is simple and inexpensive to perform.
• The test can be performed on in-place concrete.
Disadvantages:
• The test is only considered appropriate for grouts and highly workable concretes.
• The test is a static test that must be performed on a level concrete surface.
• Large coarse aggregate particles could interfere with the descent of the ring and distort
test results.
• The test is not widely used and the interpretation of the test results is not well known.

Kelly Ball Test

    The Kelly ball test (Powers 1968; Bartos 1992; Scanlon 1994; Ferraris 1999; Bartos, Sonebi, and Tamimi 2002) was developed in the 1950s in the United States as a fast alternative to the slump test. The simple and inexpensive test can be quickly performed on in-place concrete and the results can be correlated to slump.
    The test apparatus consists of a 6 inch diameter, 30 pound ball attached to a stem, as shown in Figure 6. The stem, which is graduated in ¼ inch increments, slides through a frame that rests on the fresh concrete. To perform the test, the concrete to be tested is stuck off level. The ball is released and the depth of penetration is measured to the nearest ¼ inch. At least three measurements must be made for each sample.

    The Kelly ball test provides an indication of yield stress, as the test essentially measures whether the stress applied by the weight of the ball is greater than the yield stress of the concrete (Ferraris 1999). For a given concrete mixture, the results of the Kelly ball test can be correlated to slump.
Equations based on empirical testing have been published for use on specific types of concrete mixtures (Powers 1968). Typically, the value of slump is 1.10 to 2.00 times the Kelly ball test reading. It has been claimed that the Kelly ball test is more accurate in determining consistency than the slump test (Scanlon 1994).
     The Kelly ball test was formerly standardized in ASTM C360-92: “Standard Test Method for Ball Penetration in Freshly Mixed Hydraulic Cement Concrete.” The ASTM standard was discontinued in 1999 due to lack of use. The test has never been used widely outside the United States (Bartos 1992).
    The test is applicable to a similar range of concrete consistencies as the slump test and is applicable to special mixes, such as lightweight and heavyweight concretes. The precision of the test declines with the increasing size of coarse aggregate (Bartos 1992).
Advantages:
• The test is faster than the slump test and can be preformed on in-place concrete to obtain
a direct result quickly.
• It has been claimed that the Kelly ball test provides more accurate results than the slump
test.
Disadvantages:
• Like the slump test, the Kelly ball test is a static test.
• The test must be performed on a level concrete surface.
• The test is no longer widely used.
• Large aggregate can influence the results.

Various Lab Test On Concrete

      There are many tests which are conducted to check the quality of concrete. These tests are basically divided into two categories

1. Various Lab Test On Fresh Concrete.
       a) Slump Test – Workability
       b) Compacting Factor
       c) Vee- Bee Test
2.Various Lab Test On Hardened Concrete.

          There are two kinds of tests which are done on hardened concrete. These are non destructive test and destructive tests. In non destructive test, the sample is not destroyed and this test is very useful in determining the strength of existing buildings or structures where as in destructive test a sample is made and then destroyed to find out the strength of concrete.Compression test is the example of destructive test. Here are the nondestructive tests.

        a) Rebound Hammer Test
        b) Ultrasonic Pulse Velocity Test

Test Methods for Very Low Slump Concrete

     Low slump concrete is desirable when concrete is placed in large open forms, or when the form is placed on a slope. The concrete mix must be designed for these special applications.
Very low slump concretes are typically too stiff to be measured with test methods that consider the ability of concrete to flow. Instead, tests for very low slump concretes generally attempt to simulate the actual placement conditions for low slump concretes and measure more relevant properties like compactability. The proctor test and the Kango hammer test utilize vibration to compact samples whereas the intensive compaction test uses compression and shear forces.
These tests are generally simple to perform, although none can be used as a simple field quality control device.
1.Proctor Test
The proctor test used for soils can also be used for lean, dry concrete mixes The test procedure for concrete is the same test procedure commonly used for soils. Either the standard Proctor test  or the modified Proctor test  can be used. Four to six samples, each with varying moisture content, are compacted in a cylindrical mold using a drop hammer. The unit weight of each compacted sample is plotted against moisture content to determine the maximum dry unit weight and corresponding moisture content.
Advantages:
• The test is appropriate for low slump concrete mixtures that cannot be tested with conventional workability tests.
• The test is simple and well known.
Disadvantages:
• The test does not incorporate vibration, which is commonly used to compact low slump concretes.
• The test is time consuming: performing the test requires four to six samples to be prepared to define the unit weight versus moisture content curve.

2.Kango Hammer Test
The Kango hammer test  attempts to measure workability by simulating the effect of vibration and pressing on low-slump concretes. Concrete is placed in a cubic or cylinder mold in two to three separate layers. A demolition hammer, which is mounted in a frame and equipped with a special bit that fits the shape of the mold, applies a constant pressure and vibration to each layer of concrete. After compaction of all layers, the density of the concrete specimen is
determined. The greater the density of the compacted concrete specimen, the greater will be the compactability and workability of the concrete mix.
The particular demolition hammer typically used for this test method is manufactured by Kango
Advantages:
• By using both vibration and pressure, the test accurately simulates field placement conditions.
• The test is simple and easy to perform.
Disadvantages:
• The particular hammer is not specified, making comparisons of the test results difficult.
• The apparatus is larger than the proctor test and requires electricity.

3.Intensive Compaction Test
The intensive compaction test  is a gyratory compactor used to measure the workability of concrete mixtures with slumps less than approximately 1 cm. The test apparatus is a machine that applies compression and shear forces to a concrete specimen while recording the density of the specimen. To perform the test, the concrete to be tested is placed in a cylindrical mold, which is loaded into the test apparatus. The mold is available in two diameters—a 100 mm diameter mold is used for concretes with maximum aggregate sizes of up to 20 mm while a 150 mm diameter mold is appropriate for maximum aggregate sizes up to 32 mm. Two pistons at either end of the cylinder apply a compressive force to the sample.
Simultaneously, the angle of inclination of the pistons rotates to apply a shearing motion to the concrete. This compaction technique is represented in  the Figure below . The pressure and speed of rotation can be adjusted for each test; however, these variables are held constant during each test. The volume of the sample, which is used to calculate density, is recorded continuously throughout the test. The test is performed in 3-5 minutes.

Figure : Compaction of Concrete Sample in Intensive Compaction Device.

To determine the workability of a concrete mixture, the density of the concrete is plotted versus the number of working cycles of the pistons. Concrete mixes are evaluated by comparing the density after a certain number of cycles under a given pressure. Additionally, the performance of concrete production machines can be evaluated by comparing the density achieved with a particular machine to the density achieved with the intensive compaction test.
After the test, the sample of concrete can be removed from the cylinder mold and tested for compressive or splitting tensile strength either in the concrete’s fresh or hardened state. The results of the intensive compaction test show good correlation to the results of the Kango
hammer test and the Proctor test.

Although the larger 150 mm diameter model is too heavy and bulky for field use, the lightweight version of the 100 mm diameter model weighs approximately 120 lbs and can be transported to a field site. Electricity and compressed air are required to perform the test.
Advantages:
• Research has shown that the test is capable of accurately measuring even small changes in mixture proportions.
• The test accurately simulates placement conditions for low slump roller-compacted concretes.
• The test is fast and computer controlled.
• The test can be used for research, mix proportioning, or quality control. The smaller 100 mm model is feasible for field use.
Disadvantages:
• The equipment is expensive, especially when compared to the proctor test. The 150 mm diameter model is too heavy for field use.
• The test does not incorporate vibration, which is commonly used in the placement of low slump concrete.

SIEVE ANALYSIS of AGGREGATES

      This test is done to determine the particle size distribution of fine and coarse aggregates.

PRINCIPLE
     By passing the sample downward through a series of standard sieves, each of decreasing size openings, the aggregates are separated into several groups, each of which contains aggregates in a particular size range.

APPARATUS

i) A set of IS Sieves of sizes - 80mm, 63mm, 50mm, 40mm, 31.5mm, 25mm, 20mm, 16mm, 12.5mm, 10mm, 6.3mm, 4.75mm, 3.35mm, 2.36mm, 1.18mm, 600μm, 300μm, 150μm and 75μm
ii) Balance or scale with an accuracy to measure 0.1 percent of the weight of the test sample

SAMPLE       The weight of sample available should not be less than the weight given below:-

      The sample for sieving should be prepared from the larger sample either by quartering or by means of a sample divider.

PROCEDURE i) The test sample is dried to a constant weight at a temperature of 110 + 5^oC and weighed.
ii) The sample is sieved by using a set of IS Sieves.
iii) On completion of sieving, the material on each sieve is weighed.
iv) Cumulative weight passing through each sieve is calculated as a percentage of the total sample weight.
v) Fineness modulus is obtained by adding cumulative percentage of aggregates retained on each sieve and dividing the sum by 100.

REPORTING OF RESULTS The results should be calculated and reported as:
i) the cumulative percentage by weight of the total sample
ii) the percentage by weight of the total sample passing
through one sieve and retained on the next smaller sieve, to  the nearest 0.1 percent.
      The results of the sieve analysis may be recorded graphically on  a semi-log graph with particle size as abscissa (log scale) and  the percentage smaller than the specified diameter as ordinate. 

MAXIMUM DRY DENSITY AND OPTIMUM MOISTURE CONTENT OF SOIL

     The peak dry unit weight is called the "maximum dry density” and the Optimum Water Content, is the water content at the soil’s maximum dry density.
     Compaction is the process of increasing the bulk density of a soil or aggregate by driving out air. For any soil, at a given compactive effort, the density obtained depends on the moisture content. For any soil, an “optimum water content” exists at which it will achieve it’s maximum density.
      This Test determines the optimum water content and maximum dry density of for a soil as per IS: 2720 (Part 8) - 1983.A required range for moisture is often specified isIe, 3% below and 2% above optimum.For example, if optimum water content is 16%, the acceptable range would be from 13% to 18%.

APPARATUS

     i) Cylindrical metal mould - it should be either of 100mm dia. and 1000cc volume or 150mm dia. and 2250cc volume and should conform to IS: 10074 – 1982.
     ii) Balances - one of 10kg capacity, sensitive to 1g and the other of 200g capacity, sensitive to 0.01g. 
    iii) Oven - thermostatically controlled with an interior of non corroding material to maintain temperature between 105 and 110^oC.
     iv) Steel straightedge - 30cm long.
     v) IS Sieves of sizes - 4.75mm, 19mm and 37.5mm.

PREPARATION OF SAMPLE
     A representative portion of air-dried soil material, large enough to provide about 6kg of material passing through a 19mm IS Sieve (for soils not susceptible to crushing during compaction) or about 15kg of material passing through a 19mm IS Sieve (for soils susceptible to crushing during compaction), should be taken.This portion should be sieved through a 19mm IS Sieve and the coarse fraction rejected after its proportion of the total sample has been recorded.
     Aggregations of particles should be broken down so that if the sample was sieved through a 4.75mm IS Sieve, only separated individual particles would be retained.

PROCEDURE       A) Soil not susceptible to crushing during compaction –
      i) A 5kg sample of air-dried soil passing through the 19mm IS Sieve should be taken. The sample should be mixed thoroughly with a suitable amount of water depending on the soil type (for sandy and gravelly soil - 3 to 5% and for cohesive soil - 12 to 16% below the plastic limit). The soil sample should be stored in a sealed container for a minimum period of 16hrs. 
      ii) The mould of 1000cc capacity with base plate attached,should be weighed to the nearest 1g (W₁ ). The mould should be placed on a solid base, such as a concrete floor or plinth and the moist soil should be compacted into the mould, with the extension attached, in five layers of approximately equal mass, each layer being given 25 blows from the 4.9kg rammer dropped from a height of 450mm above the soil. The blows should be distributed uniformly over the surface of each layer. The amount of soil used should be sufficient to fill the mould, leaving not more than about 6mm to be struck off when the extension is removed.The extension should be removed and the compacted soil should be levelled off carefully to the top of the mould by means of the straight edge. The mould and soil should then be weighed to the nearest gram (W₂).
     iii) The compacted soil specimen should be removed from the mould and placed onto the mixing tray. The water content (w) of a representative sample of the specimen should be determined as in Para 5.1.
     iv) The remaining soil specimen should be broken up, rubbed through 19mm IS Sieve and then mixed with the remaining original sample. Suitable increments of water should be added successively and mixed into the sample, and the above operations i.e. Para ii) to iv) should be repeated for each increment of water added. The total number of determinations made should be at least five and the moisture contents should be such that the optimum moisture content at which the maximum dry density occurs,lies within that range.
     B) Soil susceptible to crushing during compaction –
or more 2.5kg samples of air-dried soil passing through the 19mm IS Sieve, should be taken. The samples should each be mixed thoroughly with different amounts of water and stored in a sealed container as mentioned in Para A) i), above. Follow the operations given in Para A) ii) to iv), above.
     C) Compaction in large size mould – For compacting soil containing coarse material upto 37.5mm size, the 225⁰cc mould should be used. A sample weighing about 30kg and passing through the 37.5mm IS Sieve is used for the test. Soil is compacted in five layers, each layer being given 55 blows of the 4.9kg rammer. The rest of the procedure is the same as in Para A) or B), above.

REPORTING OF RESULTS
      Bulk density γ in g/cc of each compacted specimen should be calculated from the equation,

where, V = volume in cc of the mould.
The dry density γ_d in g/cc is calculated from the equation,

      The dry densities, γ_d obtained in a series of determinations should be plotted against the corresponding moisture contents, w. A smooth curve should be drawn through the resulting points and the position of the maximum on the curve should be determined. A sample graph is shown below:

      The dry density in g/cc corresponding to the maximum point on the moisture content/dry density curve should be reported as the maximum dry density to the nearest 0.01.
The percentage moisture content corresponding to the maximum dry density on the moisture content/dry density curve should be reported as the optimum moisture content and quoted to the nearest 0.2 for values below 5%, to the nearest 0.5 for values from 5 to 10% and to the nearest whole number for values exceeding 10%.

Free Swell Index Determination Test

DEFINITION       Free Swell Index is the increase in volume of a soil, without any external constraints,on submergence in water
It is determined by the following way as per IS: 2720 (Part XL) - 1977.

PRINCIPLE
     Free swell or differential free swell, also termed as free swell index, is the increase in volume of soil without any external constraint when subjected to submergence in water.
APPARATUS i) IS Sieve of size 425μm
ii) Oven
iii) Balance, with an accuracy of 0.01g
iv) Graduated glass cylinder- 2 nos., each of 100ml capacity

PROCEDURE

i) Take two specimens of 10g each of pulverised soil passing through 425μm IS Sieve and oven-dry.
ii) Pour each soil specimen into a graduated glass cylinder of 100ml capacity.
iii) Pour distilled water in one and kerosene oil in the other cylinder upto 100ml mark.
iv) Remove entrapped air by gently shaking or stirring with a glass rod.
v) Allow the suspension to attain the state of equilibrium (for not less than 24hrs.).
vi) Final volume of soil in each of the cylinder should be read out.

REPORTING OF RESULTS

where, V_d = volume of soil specimen read from the graduated cylinder containing distilled water.
            V_k = volume of soil specimen read from the graduated cylinder containing kerosene.

Water Content of Soil by Oven Drying Method

 Water Content of soil is the quantity of soil contained in a sample of soil. Generally this is expressed in ratio.

Here : s-soil (dry), v-void (pores filled with water or air), w-water, a-air. V is volume, M is mass.
Volumetric Water Content is defined by

where V_w is the volume of water and V_T = V_s + V_v = V_s + V_w + V_a is the total volume (that is soil volume + water volume + air space).

Gravimetric water content is expressed by mass (weight) as follows:

where m_w is the mass of water and m_t is the bulk mass. The bulk mass is taken as the total mass, except for geotechnical and soil science applications where oven-dried soil (m_s, see the diagram) is conventionally used as m_t

By Oven Drying Method  we can determine the Gravimetric water content in soil  as per IS: 2720 (Part II) - 1973.

PRINCIPLE
The water content (w) of a soil sample is equal to the mass of water divided by the mass of solids.

APPARATUS

i) Thermostatically controlled oven maintained at a temperature of 110 ± 5^oC
ii) Weighing balance, with an accuracy of 0.04% of the weight of the soil taken
iii) Air-tight container made of non-corrodible material with lid
iv) Tongs

SAMPLE
The soil specimen should be representative of the soil mass. The quantity of the specimen taken would depend upon the gradation and the maximum size of particles as under:

Size of particles 90 percent passing through IS Sieve	Minimum quantity of soil specimen to be taken for test (g)
425μm 2.0mm 4.75mm 9.50mm 19mm 37.5mm	25 50 200 300 500 1000

PROCEDURE
i) Clean the container, dry it and weigh it with the lid (Weight 'W₁').
ii) Take the required quantity of the wet soil specimen in the container and weigh it with the lid (Weight 'W₂').
iii) Place the container, with its lid removed, in the oven till its weight becomes constant (Normally for 24hrs.).
iv) When the soil has dried, remove the container from the oven, using tongs.
v) Find the weight 'W₃' of the container with the lid and the dry soil sample.

REPORTING OF RESULTS
The water content,  

An average of three determinations should be taken.
A sample proforma for the record of the test results is given below

In-Situ Dry Density by Sand Replacement Method

        This test method sets out the procedure for the determination for the insitu dry density of compacted soils, gravels and crushed rock materials in earth works and pavement layers by the sand replacement method using a sand pouring cone. This test is generally limited to materials with a maximum particle size of 5cm

AIM
To determine the in-situ dry density of soil by sand replacement method as per IS: 2720 (Part XXVIII) – 1974.

APPARATUS

i) Sand-pouring cylinder conforming to IS: 2720 (Part XXVIII) –1974
ii) Cylindrical calibrating container conforming to IS: 2720 (PartXXVIII) - 1974
iii) Soil cutting and excavating tools such as a scraper tool,bent spoon
iv) Glass plate - 450mm square and 9mm thick or larger
v) Metal containers to collect excavated soil
vi) Metal tray - 300mm square and 40mm deep with a 100mm hole in the centre
vii) Balance, with an accuracy of 1gm

PROCEDURE A. Calibration of apparatus
a) The method given below should be followed for the determination of the weight of sand in the cone of the pouring cylinder:
i) The pouring cylinder should be filled so that the level of the sand in the cylinder is within about 10mm of the top. Its total initial weight (W₁) should be maintained constant throughout the tests for which the calibration is used. A volume of sand equivalent to that of the excavated hole in the soil (or equal to that of the calibrating container) should be allowed to runout of the cylinder under gravity. The shutter of the pouring cylinder should then be closed and the cylinder placed on a plain surface, such as a glass plate.
ii) The shutter of the pouring cylinder should be opened and sand allowed to runout. When no further movement of sand takes place in the cylinder, the shutter should be closed and the cylinder removed carefully.
iii) The sand that had filled the cone of the pouring cylinder (that is, the sand that is left on the plain surface) should be collected and weighed to the nearest gram.
iv) These measurements should be repeated at least thrice and the mean weight (W₂) taken.

b) The method described below should be followed for the determination of the bulk density of the sand ( γ_s )
i) The internal volume (V) in ml of the calibrating container should be determined from the weight of water contained in the container when filled to the brim. The volume may also be calculated from the measured internal dimensions of the container.
ii) The pouring cylinder should be placed concentrically on the top of the calibrating container after being filled to the constant weight (W1) as in Para a) i), above. The shutter of the pouring cylinder should be closed during the operation. The shutter should be opened and sand allowed to runout. When no further movement of sand takes place in the cylinder, the shutter should be closed. The pouring cylinder should be removed and weighed to the nearest gram.
iii) These measurements should be repeated at least thrice and the mean weight (W₃) taken.
B. Measurement of soil density
The following method should be followed for the measurement of soil density:
i) A flat area, approximately 450sq.mm of the soil to be tested should be exposed and trimmed down to a level surface, preferably with the aid of the scraper tool.
ii) The metal tray with a central hole should be laid on the prepared surface of the soil with the hole over the portion of the soil to be tested. The hole in the soil should then be excavated using the hole in the tray as a pattern, to the depth of the layer to be tested upto a maximum of 150mm. The excavated soil should be carefully collected, leaving no loose material in the hole and weighed to the nearest gram(Ww). The metal tray should be removed before the pouring cylinder is placed in position over the excavated hole.
iii) The water content (w) of the excavated soil should be determined by the method specified in Para 5.1. Alternatively, the whole of the excavated soil should be dried and weighed (W_d).
iv) The pouring cylinder, filled to the constant weight (W₁) as above, should be so placed that the base of the cylinder covers the hole concentrically. The shutter shoul then be opened and sand allowed to runout into the hole. The pouring cylinder and the surrounding area should not be vibrated during this period. When no further movement of sand takes place, the shutter should be closed. The cylinder should be removed and weighed to the nearest gram (W₄).

CALCULATIONS
i) The weight of sand (W_a) in gram, required to fill the calibrating container should be calculated from the formula:
W_a = W₁ – W₃ – W₂
ii) The bulk density of the sand (γ_s) in kg/m3 should be calculated from the formula:
γ_s = V/W_a×1000
ii) The weight of sand (W_b) in gram, required to fill the excavated hole should be calculated from the formula:
W_b = W₁ – W₄ – W₂
iv) The bulk density (γ_b), that is, the weight of the wet soil per cubic meter should be calculated from the formula:
γ_d=W_w/W_b×γ_s Kg/m³
v) The dry density (γ_d), that is, the weight of dry soil per cubic meter should be calculated from the formula:
γ_d=100γ_b/(100+w) Kg/m³
γ_d=W_d/W_b×γ_s Kg/m³

REPORTING OF RESULTS
The following values should be reported:
i) dry density of soil in kg/m3 to the nearest whole number; also to be calculated and reported in g/cc correct to the second place of decimal
ii) water content of the soil in percent reported to two significant figures.
A sample proforma for the record of the test results is given below..

IN-SITU DRY DENSITY BY CORE CUTTER METHOD

AIM To determine the in-situ dry density of soil by core cutter method as per IS: 2720 (Part XXIX) - 1975.

APPARATUS

i) Cylindrical core cutter
ii) Steel dolley
iii) Steel rammer
iv) Balance, with an accuracy of 1g
v) Straightedge
vi) Square metal tray - 300mm x 300mm x 40mm
vii) Trowel

PROCEDURE
i) The internal volume (V) of the core cutter in cc should be  calculated from its dimensions which should be measured to  the nearest 0.25mm.
ii) The core cutter should be weighed to the nearest gram (W₁).
iii) A small area, approximately 30cm square of the soil layer to  be tested should be exposed and levelled. The steel dolly  should be placed on top of the cutter and the latter should be rammed down vertically into the soil layer until only about 15mm of the dolly protrudes above the surface, care being  taken not to rock the cutter. The cutter should then be dug  out of the surrounding soil, care being taken to allow some soil to project from the lower end of the cutter. The ends of  the soil core should then be trimmed flat in level with the  ends of the cutter by means of the straightedge.
iv) The cutter containing the soil core should be weighed to the  nearest gram (W₂).
v) The soil core should be removed from the cutter and a  representative sample should be placed in an air-tight container and its water content (w) determined as in Para 

REPORTING OF RESULTS

Bulk density of the soil  γ =(W₂ -W₁)/V g/cc
Dry density of the soil γ_d = 100γ/(100+w) g/cc

Average of at least three determinations should be reported to the second place of decimal in g/cc.
A sample proforma for the record of the test results is given below..

PLASTIC LIMIT TEST

Plastic limit is the water content below which the soil stops behaving as a plastic material.The plastic limit is determined by rolling a part of a soil into thread,when the thread begins to crumble at a diameter of 3.18mm or 1/8", the water content at this stage is the plastic limit.

AIM To determine the plastic limit of soil as per IS: 2720 (Part 5)- 1985.

PRINCIPLE The plastic limit of fine-grained soil is the water content of the soil below which it ceases to be plastic. It begins to crumble when rolled into threads of 3mm dia.

APPARATUS i) Porcelain evaporating dish about 120mm dia.
ii) Spatula
iii) Container to determine moisture content
iv) Balance, with an accuracy of 0.01g
v) Oven
vi) Ground glass plate - 20cm x 15cm
vii) Rod - 3mm dia. and about 10cm long

PREPARATION OF SAMPLE Take out 30g of air-dried soil from a thoroughly mixed sample of the soil passing through 425μm IS Sieve. Mix the soil with distilled water in an evaporating dish and leave the soil mass for naturing. This period may be upto 24hrs.

PROCEDURE i) Take about 8g of the soil and roll it with fingers on a glass plate. The rate of rolling should be between 80 to 90 strokes per minute to form a 3mm dia.
ii) If the dia. of the threads can be reduced to less than 3mm, without any cracks appearing, it means that the water content is more than its plastic limit. Knead the soil to reduce the water content and roll it into a thread again.
iii) Repeat the process of alternate rolling and kneading until the thread crumbles.
iv) Collect and keep the pieces of crumbled soil thread in the container used to determine the moisture content.
v) Repeat the process at least twice more with fresh samples of plastic soil each time.

REPORTING OF RESULTS The plastic limit should be determined for at least three portions of the soil passing through 425μm IS Sieve. The average water content to the nearest whole number should be reported.

LIQUID LIMIT TEST

The lowest water content at which the soil is in a liquid state is called the liquid limit.At liquid limit, the clay is practically like a liquid but possesses a small strength.It is primarily used by civil and geotechnical engineers as a physical property of a soil.  The liquid limit allows engineers to classify soils into their applications.For determining Liquid Limit the most popular test is Casagrande,s Liquid Limit Test.

AIM To determine the liquid limit of soil as per IS: 2720 (Part 5)- 1985.

PRINCIPLE The liquid limit of fine-grained soil is the water content at which soil behaves practically like a liquid, but has small shear strength. It's flow closes the groove in just 25 blows in Casagrande’s liquid limit device.

APPARATUS

i) Casagrande’s liquid limit device
ii) Grooving tools of both standard and ASTM types
iii) Oven
iv) Evaporating dish
v) Spatula
vi) IS Sieve of size 425μm
vii) Weighing balance, with 0.01g accuracy
viii) Wash bottle
ix) Air-tight and non-corrodible container for determination of moisture content
PREPARATION OF SAMPLE i) Air-dry the soil sample and break the clods. Remove the organic matter like tree roots, pieces of bark, etc.
ii) About 100g of the specimen passing through 425μm IS Sieve is mixed thoroughly with distilled water in the evaporating dish and left for 24hrs. for soaking.

PROCEDURE i) Place a portion of the paste in the cup of the liquid limit device.
ii) Level the mix so as to have a maximum depth of 1cm.
iii) Draw the grooving tool through the sample along the symmetrical axis of the cup, holding the tool perpendicular to the cup.
iv) For normal fine grained soil: The Casagrande's tool is used to cut a groove 2mm wide at the bottom, 11mm wide at the top and 8mm deep.
v) For sandy soil: The ASTM tool is used to cut a groove 2mm wide at the bottom, 13.6mm wide at the top and 10mm deep.
vi) After the soil pat has been cut by a proper grooving tool, the handle is rotated at the rate of about 2 revolutions per second and the no. of blows counted, till the two parts of the soil sample come into contact for about 10mm length.
vii) Take about 10g of soil near the closed groove and determine its water content.
viii) The soil of the cup is transferred to the dish containing the soil paste and mixed thoroughly after adding a little more water. Repeat the test.
ix) By altering the water content of the soil and repeating the foregoing operations, obtain at least 5 readings in the range of 15 to 35 blows. Don’t mix dry soil to change its consistency.
x) Liquid limit is determined by plotting a ‘flow curve’ on a semi-log graph, with no. of blows as abscissa (log scale) and the water content as ordinate and drawing the best straight line through the plotted points.
xi) Water content corresponding to 25 blows, is the value of the liquid limit.

REPORTING OF RESULTS Report the water content corresponding to 25 blows, read from the 'flow curve' as the liquid limit. A sample ‘flow curve’ is given below.

PERMEABILITY TEST

       Permeability of concrete is important when dealing with durability of concrete particularly in concrete used for water retaining structures or watertight sub-structures.Structures exposed to harsh environmental conditions also require low porosity as well as permeability. Such adverse elements can result in degradation of reinforced concrete, for example, corrosion of steel leading to an increase in the volume of the steel, cracking and eventual spalling of the concrete. Permeability tests measure the ease with which liquids, ions and gases can penetrate into the concrete. In situ tests are available for assessing the ease with which water, gas and deleterious matter such as chloride ions can penetrate into the concrete.

PROCEDURE
     A comprehensive review of the wide range of test methods is given in the Concrete Society Technical Report No. 31. Two of the most widely established methods are the initial surface absorption test (ISAT) and the modified Figg air permeability test. The former measures the ease of water penetration into the surface layer of the concrete while the latter can be used to determine the rate of water as well as air penetration into the surface layer of the concrete which is also called the covercrete. Another newly developed technique uses modification of the laboratory test to determine chloride ion permeability. All the site tests emphasize the measurement of permeability of the outer layer of concrete as this layer is viewed as most important for the durability of concrete.

EQUIPMENTS

1. Initial surface absorption test
      Details of the ISAT is given in BS 1881:Part 5 which measures the surface water absorption. In this method, a cup with a minimum surface area of 5000 mm2 is sealed to the concrete surface and filled with water. The rate at which water is absorbed into the concrete under a pressure head of 200 mm is measured by movement along a capillary tube attached to the cup. When water comes into contact with dry concrete it is absorbed by capillary action initially at a high rate but at a decreasing rate as the water filled length of the capillary increases. This is the basis of initial surface absorption, which is defined as the rate of water flow into concrete per unit area at a stated interval from the start of test at a constant applied head at room temperature.

2. Modified Figg permeability Test
      The modified Figg permeability test can be used to determine the air or wate permeability of the surface layer of the concrete. In both the air and water permeability test a hole of 10 mm diameter is drilled 40 mm deep normal to the concrete surface. A plug is inserted into this hole to form an airtight cavity in the concrete. In the air permeability test, the pressure in the cavity is reduced to –55 kPa using a hand operated vacuum pump and the pump is isolated. The time for the air to permeate through the concrete to increase the cavity pressure to –50 kPa is noted and taken as the measure of the air permeability of the concrete. Water permeability is measured at a head of 100 mm with a very fine canula passing through a hypodermic needle to touch the base of the cavity. A two-way connector is used to connect this to a syringe and to a horizontal capillary tube set 100 mm above the base of the cavity. Water is injected through the syringe to replace all the air and after one minute the syringe isolated with a water meniscus in a suitable position. The time for the meniscus to move 50 mm is taken as a measure of the water permeability of the concrete.

3. In situ rapid chloride ion permeability test
     This method was originally designed for laboratory application but has been modified for in situ use. The procedure for the laboratory test is given in AASHTO T277 and ASTM C1202. The technique is based on the principle that charged ions, such as chloride (Cl- ), will accelerate in an electric field towards the pole of opposite charge. The ions will reach terminal velocity when the frictional resistance of the surrounding media reaches equilibrium with the accelerating force. This is the basis of “electrophoresis”, which is utilized in many chemical and biological studies.
      A DC power supply is used to apply a constant voltage between the copper screen and the steel reinforcement. The total current flowing between the mesh and the reinforcing bar over a period of six hours is then measured. The total electric charge (in coulombs) is computed and can be related to the chloride ion permeability of the concrete.

APPLICATIONS
       The methods described do not measure permeability directly but produce a ‘permeability index’, which is related closely to the method of measurement. In general, the test method used should be selected as appropriate for the permeation mechanism relevant to the performance requirements of the concrete being studied. Various permeation mechanisms exist depending on the permeation medium, which include absorption and capillary effects, pressure differential permeability and ionic and gas diffusion.
        Most of these methods measure the permeability or porosity of the surface layer of concrete and not the intrinsic permeability of the core of the concrete.  The covercrete has been known to significantly affect the concrete durability since deterioration such as carbonation and leaching starts from the concrete surface. This layer thus provides the first defense against any degradation.

RANGE AND LIMITATIONS
      For the ISAT, tests on oven dried specimens give reasonably consistent results but in other cases results are less reliable. This may prove to be a problem with in situ concrete.
      Particular difficulties have also been encountered with in situ use in achieving a watertight fixing. The test has been found to be very sensitive to changes in quality and to correlate with observed weathering behaviour. The main application is as a quality control test for precast units but application to durability assessment of in situ concrete is growing