Determination of Bulking of Fine Aggregate

The increase in volume of fine aggregate due to presence of moisture content is known as bulking. Fine sand bulks more as compared to coarse sand. Extremely fine sand particularly the manufactured fine aggregate bulks as much as about 40%.

The moisture present in aggregate forms a film around each particle. These films of moisture exert a force, known as surface tension, on each particle. Due to this surface tension each particles gets away from each other. Because of this no direct contact is possible among individual particles and this causes bulking of the volume.

Note: Fine aggregate do not show any bulking when it is absolutely dry or completely saturated.

AIM:

To determine bulking of a given sample of fine aggregate.

Apparatus:

·         Measuring jar,

·         Taping rod, etc.

FIGURE:

Procedure:

1. Put sufficient quantity of the sand loosely into a container. Level off the top of the sand and pushing a steel rule vertically down through the sand at the middle to the bottom, measure the height. Suppose this is h1 cm.
2. Empty the sand out of the container into another container where none of it will be lost. Half fill the first container with water. Put back about half the sand and rod it with a steel rod, about 6 mm in diameter, so that its volume is reduced to a minimum. Then add the remainder of the sand and rod it in the same way.
3. The percentage of bulking of the sand due to moisture shall be calculated.

CALCULATION:

• Percentage Bulking = [(h1/h2)-1]x100

Conclusion / Result:

• Bulking of a given sample of fine aggregate is found to be ……. %

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1. Determination of Specific Gravity of Fine Aggregate.

2. Determination of Fineness Modulus of Fine Aggregate.

Determination of Specific Gravity of Fine Aggregate

Specific gravity of fine aggregate (sand) is the ratio of the weight of given volume of fine aggregates to the weight of equal volume of water. The specific gravity of sand is considered to be around 2.65.

AIM:

To determine specific gravity of a given sample of fine aggregate.

Apparatus:

·         Balance,

·         Oven,

·         Pycnometer,

·         A tray of area not less than 32cm²,

·         Well-ventilated oven,

·         Taping rod,

·         Filter papers and funnel, etc.

FIGURE:

 

Procedure:

1. Take about 500g of sample and place it in the pycnometer.
2. Pour distilled water into it until it is full.
3. Eliminate the entrapped air by rotating the pycnometer on its side, the hole in the apex of the cone being covered with a finger.
4. Wipe out the outer surface of pycnometer and weigh it (W)
5. Transfer the contents of the pycnometer into a tray, care being taken to ensure that all the aggregate is transferred.
6. Refill the pycnometer with distilled water to the same level.
7. Find out the weight (W1).
8. Drain water from the sample through a filter paper.
9. Place the sample in oven in a tray at a temperature of 100ºC to 110º C for 24±0.5 hours, during which period, it is stirred occasionally to facilitate drying.
10. Cool the sample and weigh it (W2).

CALCULATION:

Apparent specific gravity = (weight of dry sample/weight of equal volume of water )

= W2/(W2- (W-W2))

Conclusion / Result:

Specific gravity of fine aggregate =………………….


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2. Determination of Fineness Modulus of Fine Aggregate.

Determination of fineness modulus of fine aggregate

Particle Size Distribution of Fine Aggregates is the operation of dividing a sample of aggregate into various fractions each consisting of particles of the same size. The sieve analysis is conducted to determine the particle size distribution in a sample of aggregate, which we call gradation. Many a time, fine aggregates are designated as coarse sand, medium sand and fine sand. These classifications do not give any precise meaning. What the supplier terms as fine sand may be really medium or even coarse sand. To avoid this ambiguity fineness modulus could be used as a yard stick to indicate the fineness of sand.

The following limits may be taken as guidance:

Fine sand           : F.M. : 2.2 - 2.6

Medium sand      : F.M. : 2.6 - 2.9

Coarse sand        : F.M. : 2.9 - 3.2

Sand having a fineness modulus more than 3.2 will be unsuitable for making satisfactory concrete.

AIM:

To determine fineness modulus of fine aggregate.

Apparatus:

·         Test Sieves conforming to IS: 460-1962

o   4.75 mm,

o   2.36 mm,

o   1.18 mm,

o   600 micron,

o   300 micron,

o   150 micron

·         Balance,

·         Stop Watch.

FIGURE:

Procedure:

1.   The sample shall be brought to an air-dry condition before weighing and sieving. The air-dry sample shall be weighed and sieved successively on the appropriate sieves starting with the largest. Care shall be taken to ensure that the sieves are clean before use.

2.   The shaking shall be done with a varied motion, backward sand forwards, left to right, circular clockwise and anti-clockwise, and with frequent jarring, so that the material is kept moving over the sieve surface in frequently changing directions.

3.   Material shall not be forced through the sieve by hand pressure. Lumps of fine material, if present, may be broken by gentle pressure with fingers against the side of the sieve.

4.   Light brushing with a fine camel hair brush may be used on the 150-micron and 75-micron IS Sieves to prevent aggregation of powder and blinding of apertures.

5.   On completion of sieving, the material retained on each sieve, together with any material cleaned from the mesh, shall be weighed.

Observation:

I S Sieve	Weight Retained on Sieve (gms)	Percentage of Weight Retained (%)	Percentage of Weight Passing (%)	Cumulative Percentage of Passing (%)	Remark
4.75 mm
2.36 mm
1.18 mm
600 micron
300 micron
150 micron
Total

CALCULATION:

Fineness modulus is an empirical factor obtained by adding the cumulative percentages of aggregate retained on each of the standard sieves ranging from 4.75 mm to 150 micron and dividing this sum by anarbitrary number 100.

Finess Modulus, FM = (Total of Cumulative Percentage of Passing (%) / 100)

Conclusion / Result:

I.        Fineness modulus of a given sample of fine aggregate is _________ that indicate Coarse sand/ Medium sand/Fine sand.

II.        The given sample of fine aggregate is belong to Grading Zones I / II / III / IV.

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Flakiness and Elongation Index of Coarse Aggregate

Particle shape and surface texture influence the properties of freshly mixed concrete more than the properties of hardened concrete. Rough-textured, angular, and elongated particles require more water to produce workable concrete than smooth, rounded compact aggregate. Consequently, the cement content must also be increased to maintain the water-cement ratio. Generally, flat and elongated particles are avoided or are limited to about 15 % by weight of the total aggregate.

AIM:

To determination of Flakiness Index and Elongation Index of Course Aggregates.

Apparatus:

• Standard thickness gauge.
• Standard length gauge.
• IS Sieves of size 63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 & 6.3mm.
• Balance.

FIGURE:

Procedure:

1.   Sample - A quantity of aggregate shall be taken sufficient to provide the minimum number of 200 pieces of any fraction to be tested.

2.   Sieving - The sample shall be sieved in proper manner with the sieves specified in Table.

3.   Separation of Flaky material- Each fraction shall be gauged in turn for thickness on a metal gauge of the pattern shown in Fig. 1, or in bulk on sieves having elongated slots. The width of the slot used in the gauge or sieve shall be of the dimensions specified in co1 3 of above Table for the appropriate size of material. 

4.   Weighing of Flaky Material - The total amount passing the gauge shall be weighed to an accuracy of at least 0.1 percent of the weight of the test sample.

5.   The flakiness index is the total weight of the material passing the various thickness gauges or sieves, expressed as a percentage of the total weight of the sample gauged.

6.   Sieving - The sample shall be sieved in proper manner with the sieves specified in above Table.

7.   Separation of Elongated Material- Each fraction shall be gauged individually for length on a metal length gauge of the pattern shown in Fig. 2. The gauge length used shall be that specified in co1 4 of above Table for the appropriate size of material.

8.   Weighing of Elongated Material - The total amount retained by the length gauge shall be weighed to an accuracy of at least 0.1 percent of the weight of the test sample.

9.   The elongation index is the total weight of the material retained on the various length gauges, expressed as a percentage of the total weight of the sample gauged.

OBSERVATION:

1.   Total weight of course aggregate____________ g. (Flakiness Index)

Size of Aggregate Thickness		Thickness Gauge mm	Weight Retained on Thickness Gauge	Percentage of Weight Retained (%)	Remark
Passing through IS Sieves	Retained on IS Sieves
63 mm	50 mm	33.90
50 mm	40 mm	27.00
40 mm	25 mm	19.60
31 mm	25 mm	16.95
25 mm	20 mm	13.50
20 mm	16 mm	10.80
16 mm	12 mm	8.55
12.5 mm	10 mm	6.75
10 mm	6.3 mm	4.89
		Total

 2.   Total weight of course aggregate________ g. (Elongation Index)

Size of Aggregate Thickness		Length Gauge mm	Weight Retained on Length Gauge	Percentage of Weight Retained (%)	Remark
Passing through IS Sieves	Retained on IS Sieves
63 mm	50 mm	--
50 mm	40 mm	81.0
40 mm	25 mm	58.5
31 mm	25 mm	--
25 mm	20 mm	40.5
20 mm	16 mm	32.4
16 mm	12 mm	25.6
12.5 mm	10 mm	20.2
10 mm	6.3 mm	14.7
		Total

CALCULATION:

The Flakiness index= Total of Percentage of Retained on Thickness Gauge (%)/100

The elongation index= Total of Percentage of Retained on Length Gauge (%)/100

 RESULT:

The flakiness index of a given sample of aggregate is _______ %

The elongation index of a given sample of aggregate is_______ %