FIELD TESTS ON AGGREGATE

5 COMMON FIELD TESTS ON AGGREGATE TO CHECK ITS QUALITY

Aggregates influence the properties of concrete/mortar such as water requirement, cohesiveness and workability of the concrete in plastic stage, while they influence strength, density, durability, permeability, surface finish and colour in hardened stage.

FIELD TESTS FOR AGGREGATE

1. SURFACE MOISTURE CONTENT & ABSORPTION

The surface moisture in the aggregate, influences the water cement ratio, strength and durability of the mix. To determine the surface moisture of moist or wet aggregate, method is as follows-

FRYING PAN METHOD

The following apparatus are required:

• A frying pan or metal tray,
• Gas stove or an electric hair dryer,
• A metal or glass stirring rod and
• Scales to measures.

The following procedure is followed during the test

1. For coarse aggregate 2 kg sample is adequate and for fine aggregate 0.5 kg sample is adequate.
2. The wet/moist sample is then weighed wet weight (W)
3. Heated very gently on the frying pan or metal plate and stirred with a glass or metallic rod to maintain uniform distribution of heat, until the sheen disappears from the surface. The fine aggregates become surface dry when it just starts showing free flowing characteristics.
4. The aggregates is then cooled and reweighed. The surface dry aggregate weight (Wsd) is noted. The surface moisture is then calculated as follows-

Surface moisture = [(W – Wsd) / Wsd] x 100%

5. Overheating must be avoided, as it will not give the correct surface moisture.
6. If heating is continued either on the fry pan or in the oven till the aggregate is bone dry aggregate weight is then noted (Wbd) after continuous heating. The absorption (absorbed water content) is then calculated as follows-

Absorption = [(Wsd – Wbd) / Wbd] x 100%

Similarly, if the dry aggregates are received on site and absorption capacity is to be determined then the aggregates are first soaked in water and then the above methods are deployed to determine the absorption capacity of aggregates.

2. SILT CONTENT TEST FOR SAND

Silt content test

The permissible silt content in sand (fine aggregate) must not exceed the values as specified in the standards. However, this method can only be used for natural sand, it should not be used for crushed rock sand.

The apparatus required for this test is only 250 ml glass measuring cylinder.

The silt content determination by volume is done in the following manner:

1. The glass cylinder is filled with salt-water solution (concentration of the solution will teaspoon full of common salt for every 570 ml) upto 50 ml mark.
2. Add sand until the level of the sand is upto 100 ml mark.
3. Add further salt-water solution till 150 ml mark is reached.
4. Place the palm on the mouth of the glass cylinder and shake it vigorously.
5. Place the cylinder on hard levelled surface and tap it all round so that sand is leveled.
6. Wait for three hours for silt to settle on top of sand.
7. Measure the thickness of the silt layer and the height of the sand. The silt content can be calculated as follows:

Silt (%) by volume = [(Thickness of silt layer/ Height of sand + Silt) x 100 %]

If silt content by weight exceeds 3% then washing of sand is necessary. After conducting few tests, a co-relation can be developed for silt layer thicknesses at various intervals of time. The silt content at 10 minutes can be fixed as inspection criteria.

3. BULKING OF SAND

When sand is damp, the water coating on the surface of each sand particle causes separation of particles from one another due to surface tension. This causes sand to bulk. Bulked sand occupies more volume and hence if volumetric measuring is done while proportioning it, bulking correction is necessary.

The bulking test is done as follows:

1. The sand is filled, in loose condition in a box of measured height (H cm).
2. The box is then flooded with water and rodding is done to make the sand settle and consolidate. Care should be taken that sand does not overflow during the flooding and compaction.
3. The sand is then leveled in the box and the drop in height is measured (h cm).
4. Bulking is calculated as: Bulking % = h/H x 100%

Dry sand occupies the same volume as fully saturated sand. The bulking will vary from load to load and day to day depending on the fineness of sand and its surface moisture content. It is there-fore, very essential to make bulking corrections by checking the actual bulking of sand proposed to be used by volumetric batching for mortar or concrete.

Moisture contents %age by wt.	Bulking % by volume
2	15
3	20
4	25
5	30

 4. SIEVE ANALYSIS

Sieve analysis is done to check the gradation of aggregate. The test is done as follow.

1. Take required amount of aggregate sample (for coarse aggregate take apprx. 2.5 kg and for fine aggregate take 0.5 kg)
2. Arrange the required no of sieves as per the contract or job requirement in an descending manner. (i.e. keep the sieve having largest size opening at the top and the smallest size opening at the bottom)
3. Shake vigorously the sieve set for at least 2 minute.
4. Then measure the weight of aggregate on each sieve and express it as the percentage of passing.

Now compare these values with the recommended values to know whether it falls within the range or not. If not falling within the desired gradation then take necessary action.

Grading limit of coarse aggregate and fine aggregate is given below for reference.

Grading Limit of Coarse Aggregate

Grading Limit of Fine Aggregate

This test is done initially for concrete mix design and later conducted periodically for mix proportion adjustments if it is suspected that the grading of aggregates has changed considerably.

5. FINENESS MODULUS

Fineness modulus is generally used to get an idea of how coarse or fine the aggregate is. More fineness modulus value indicates that the aggregate is coarser and small value of fineness modulus indicates that the aggregate is finer.

1. Sieve the aggregate using the appropriate sieves (80 mm, 40 mm, 20 mm, 10 mm, 4.75 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron & 150 micron)
2. Record the weight of aggregate retained on each sieve.
3. Calculate the cumulative weight of aggregate retained on each sieve.
4. Calculate the cumulative percentage of aggregate retained.
5. Add the cumulative weight of aggregate retained and divide the sum by 100. This value is termed as fineness modulus

Compare the test value with the values given in the following table and you can get an idea about how coarse or fine the sand is.

Only sand between FM 2.6 to 2.9 is considered suitable for nominal mix proportion.

Type of Sand	Fineness Modulus Value
Very fine sand	Below 2.2
Fine sand	2.2 to 2.6
Medium sand	2.6 to 2.9
Coarse sand	2.9 to 3.2
Very coarse sand	Above 3.2

AGGREGATE FLAKINESS INDEX

AGGREGATE FLAKINESS INDEX VALUE (IS:2386-PART 1-1963)

OBJECTIVE

For determination of flakiness index of coarse aggregate, where the  size of the coarse aggregate are larger than 6.3mm . 

REFERENCE STANDARDS

IS : 2386 (Part I) – 1963 – Method of test for aggregates for concrete (Part I) Particle size and shape.

EQUIPMENT & APPARATUS

• Thickness gauge
• Sieves [63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 & 6.3mm]
• Balance [0-10 kg]

  

  Thickness Gauge

PREPARATION SAMPLE

Surface dry samples is used for the test. A minimum number of 200 pieces of any specified fraction is required to do the test. 

PROCEDURE

1. The sample is sieved through IS sieve specified in Table shown below.

   

   Dimension of Thickness and Length Gauge

2. A minimum of 200 pieces of each fraction is taken and weighed.
3. In order to separate flaky materials, each fraction is then gauged individually for thickness on a thickness gauge. 
4. The total amount of flaky material passing the thickness gauge is weighed to an accuracy of 0.1% of the weight of sample. 

CALCULATION

In order to calculate the flakiness index of the entire sample of aggregates, first the weight of each fraction of aggregate passing and retained on the specified set of sieves is noted (Y1, Y2, Y3, Y4…..etc). Each piece of these are tried to be passed through the slot of the specified thickness of the thickness gauge are found and weighed (y1, y2, y3, y4…etc). Then the flakiness index is the percentage of materials passed through the thickness gauge on the various thickness gauges, expressed as a percentage of the total weight of the sample gauged.

REPORT

Flakiness index is reported in percentage to the nearest whole number

SAFETY & PRECAUTIONS

• Use hand gloves while removing containers from oven after switching off the oven.
• Use safety shoes, mask & aprons at the time of test.
• Thoroughly clean & dry the container before testing.
• Special care should be taken that no outer air enters when using the balance.
• All parts of the equipment should always be kept clean.
• After the end of the test sieve should be clean by smooth brush.

AGGREGATE ELONGATION INDEX

AGGREGATE ELONGATION INDEX VALUE (IS:2386-PART 1-1963

OBJECTIVE

For determination of elongation index of coarse aggregate, where the size of the coarse aggregate are larger than 6.3 mm. 

REFERENCE STANDARDS

IS: 2386 (Part I) – 1963 – Method of test for aggregates for concrete (Part I) Particle size and shape.

EQUIPMENT & APPARATUS

• Length gauge
• Sieves (63mm,50mm,40mm,31.5mm,25mm,20mm,16mm,12.5mm,10mm)
• Balance (0-10kg)
•  Oven (3000c)

  

  Length Gauge

TEST SAMPLE PREPARATION

Surface dry samples is used for the test. A minimum number of 200 pieces of any specified fraction is required to do the test. 

PROCEDURE

1. The sample is sieved through IS sieve specified in Table shown below.

   

   Dimension of Thickness and Length Gauge

2. A minimum of 200 pieces of each fraction is taken and weighed.
3. In order to separate elongated materials, each fraction is then gauged individually for length in the length gauge.
4. The pieces of aggregate from each fraction tested which could not pass through the specified gauge length with its long sides elongated are collected separately to find the total weight of aggregate retained on the length gauge from each fraction.
5. The total amount of elongated material retained by the length gauge is weighed to an accuracy of 0.1% of the weight of sample. 

CALCULATION

In order to calculate the elongation index of the entire sample of aggregates, first the weight of each fraction of aggregate passing and retained on the specified set of sieves is noted (Y1, Y2, Y3, Y4…..etc). Each piece of these are tried to be passed through specified length of the gauge length with its longest side and those elongated pieces which do not pass the gauge are separated and weighed (y1, y2, y3, y4…etc). Then the elongated 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.

REPORTS

Elongation index is reported in percentage to the nearest whole number. 

SAFETY & PRECAUTIONS

• Use hand gloves while removing containers from oven after switching off the oven.
• Use safety shoes, mask & aprons at the time of test.
• Thoroughly clean & dry the container before testing.
• Special care should be taken that no outer air enters when using the balance.
• All parts of the equipment should always be kept clean.
• After the end of the test sieve should be clean by smooth brush.

TESTS ON AGGREGATE TO CHECK QUALITY FOR USE IN ROAD WORK

7 LAB TESTS ON AGGREGATE TO CHECK QUALITY FOR USE IN ROAD WORK

TESTS ON AGGREGATE

Aggregate plays an important role in pavement construction. Aggregates influence, to a great extent, the load transfer capability of pavements. Hence it is essential that they should be thoroughly tested before using for construction. Not only that aggregates should be strong and durable, they should also possess proper shape and size to make the pavement act monolithically. Aggregates are tested for strength, toughness, hardness, shape, and water absorption.

In order to decide the suitability of the aggregate for use in pavement construction, following tests are carried out:

1. Crushing test
2. Abrasion test
3. Impact test
4. Soundness test
5. Shape test
6. Specific gravity and water absorption test
7. Bitumen adhesion test

1.CRUSHING TEST

Fig-1 Crushing Test Setup

One of the model in which pavement material can fail is by crushing under compressive stress. A test is standardized by IS: 2386 part-IV and used to determine the crushing strength of aggregates. The aggregate crushing value provides a relative measure of resistance to crushing under gradually applied crushing load.

The test consists of subjecting the specimen of aggregate in standard mould to a compression test under standard load conditions (See Fig-1). Dry aggregates passing through 12.5 mm sieves and retained 10 mm sieves are filled in a cylindrical measure of 11.5 mm diameter and 18 cm height in three layers. Each layer is tamped 25 times with at standard tamping rod. The test sample is weighed and placed in the test cylinder in three layers each layer being tamped again. The specimen is subjected to a compressive load of 40 tonnes gradually applied at the rate of 4 tonnes per minute. Then crushed aggregates are then sieved through 2.36 mm sieve and weight of passing material (W2) is expressed as percentage of the weight of the total sample (W1) which is the aggregate crushing value.

Aggregate crushing value = (W1/W2)*100

A value less than 10 signifies an exceptionally strong aggregate while above 35 would normally be regarded as weak aggregates.

Also Read: Crushing Test Procedure of Aggregate

Also read: Crushing Value Test Procedure of Aggregates

2.ABRASION TEST

Fig-2 Los Angeles Abrasion Test Setup

Abrasion test is carried out to test the hardness property of aggregates and to decide whether they are suitable for different pavement construction works. Los Angeles abrasion test is a preferred one for carrying out the hardness property and has been standardized in India (IS: 2386 part-IV).

The principle of Los Angeles abrasion test is to find the percentage wear due to relative rubbing action between the aggregate and steel balls used as abrasive charge.

Los Angeles machine consists of circular drum of internal diameter 700 mm and length 520 mm mounted on horizontal axis enabling it to be rotated (see Fig-2). An abrasive charge consisting of cast iron spherical balls of 48 mm diameters and weight 340-445 g is placed in the cylinder along with the aggregates. The number of the abrasive spheres varies according to the grading of the sample. The quantity of aggregates to be used depends upon the gradation and usually ranges from 5-10 kg. The cylinder is then locked and rotated at the speed of 30-33 rpm for a total of 500 -1000 revolutions depending upon the gradation of aggregates.

After specified revolutions, the material is sieved through 1.7 mm sieve and passed fraction is expressed as percentage total weight of the sample. This value is called Los Angeles abrasion value.

A maximum value of 40 percent is allowed for WBM base course in Indian conditions. For bituminous concrete, a maximum value of 35 percent is specified.

Also read: Los Angeles Abrasion Value Test Procedure of Aggregates

3.IMPACT TEST

Fig-3 Impact Test Setup

The aggregate impact test is carried out to evaluate the resistance to impact of aggregates. Aggregates passing 12.5 mm sieve and retained on 10 mm sieve is filled in a cylindrical steel cup of internal dia 10.2 mm and depth 5 cm which is attached to a metal base of impact testing machine. The material is filled in 3 layers where each layer is tamped for 25 numbers of blows (see Fig-3). Metal hammer of weight 13.5 to 14 Kg is arranged to drop with a free fall of 38.0 cm by vertical guides and the test specimen is subjected to 15 numbers of blows. The crushed aggregate is allowed to pass through 2.36 mm IS sieve. And the impact value is measured as percentage of aggregates passing sieve (W2) to the total weight of the sample (W1).

Aggregate impact value = (W1/W2)*100

Aggregates to be used for wearing course, the impact value shouldn’t exceed 30 percent. For bituminous macadam the maximum permissible value is 35 percent. For Water bound macadam base courses the maximum permissible value defined by IRC is 40 percent.

Also read: Impact Value Test Procedure of Aggregates

4.SOUNDNESS TEST

Soundness test is intended to study the resistance of aggregates to weathering action, by conducting accelerated weathering test cycles. The Porous aggregates subjected to freezing and thawing is likely to disintegrate prematurely. To ascertain the durability of such aggregates, they are subjected to an accelerated soundness test as specified in IS: 2386 part-V.

Aggregates of specified size are subjected to cycles of alternate wetting in a saturated solution of either sodium sulphate or magnesium sulphate for 16 – 18 hours and then dried in oven at 105 to 1100C to a constant weight. After five cycles, the loss in weight of aggregates is determined by sieving out all undersized particles and weighing.

The loss in weight should not exceed 12 percent when tested with sodium sulphate and 18 percent with magnesium sulphate solution.

Also Read: Soundness Test Procedure of Aggregates

5.SHAPE TESTS

Fig-4 Flakiness Gauge

The particle shape of the aggregate mass is determined by the percentage of flaky and elongated particles in it. Aggregates which are flaky or elongated are detrimental to higher workability and stability of mixes.

The flakiness index is defined as the percentage by weight of aggregate particles whose least dimension is less than 0.6 times their mean size. Flakiness gauge (see Fig-4) is used for this test. Test procedure had been standardized in India (IS: 2386 part-I).

The elongation index of an aggregate is defined as the percentage by weight of particles whose greatest dimension (length) is 1.8 times their mean dimension. This test is applicable to aggregates larger than 6.3 mm. Elongation gauge (see Fig-5) is used for this test. This test is also specified in (IS: 2386 Part-I). However there are no recognized limits for the elongation index.

Fig-5 Elongation Gauge

Also Read: Aggregate Flakiness Index Value Test Procedure

Also Read: Aggregate Elongation Index Value Test Procedure

6.SPECIFIC GRAVITY AND WATER ABSORPTION

The specific gravity and water absorption of aggregates are important properties that are required for the design of concrete and bituminous mixes. The specific gravity of a solid is the ratio of its mass to that of an equal volume of distilled water at a specified temperature. Because the aggregates may contain water-permeable voids, so two measures of specific gravity of aggregates are used:

1. Apparent specific gravity and
2. Bulk specific gravity.

Apparent Specific Gravity, Gapp, is computed on the basis of the net volume of aggregates i.e the volume excluding water-permeable voids. Thus

Gapp = [(MD/VN)]/W

Where,

MD is the dry mass of the aggregate,

VN is the net volume of the aggregates excluding the volume of the absorbed matter,

W is the density of water.

Bulk Specific Gravity, Gbulk, is computed on the basis of the total volume of aggregates including water permeable voids. Thus

Gbulk = [(MD/VB)]/W

Where,

VB is the total volume of the aggregates including the volume of absorbed water.

Water Absorption: The difference between the apparent and bulk specific gravities is nothing but the water permeable voids of the aggregates. We can measure the volume of such voids by weighing the aggregates dry and in a saturated surface dry condition, with all permeable voids filled with water. The difference of the above two is MW.

MW is the weight of dry aggregates minus weight of aggregates saturated surface dry condition. Thus,

Water Absorption = (MW/MD)*100

The specific gravity of aggregates normally used in road construction ranges from about 2.5 to 2.9. Water absorption values ranges from 0.1 to about 2.0 percent for aggregates normally used in road surfacing.

Also read: Specific Gravity & Water Absorption Test Procedure of Aggregates

7.BITUMEN ADHESION TEST

Bitumen adheres well to all normal types of road aggregates provided they are dry and free from dust. In the absence of water there is practically no adhesion problem of bituminous construction.

Adhesion problem occurs when the aggregate is wet and cold. This problem can be dealt with by removing moisture from the aggregate by drying and increasing the mixing temperature. Further, the presence of water causes stripping of binder from the coated aggregates. This problem occurs when bitumen mixture is permeable to water.

Several laboratory tests are conducted to arbitrarily determine the adhesion of bitumen binder to an aggregate in the presence of water. Static immersion test is one specified by IRC and is quite simple. The principle of the test is by immersing aggregate fully coated with binder in water maintained at 400C temperature for 24 hours.

IRC has specified maximum stripping value of aggregates should not exceed 5%.

LIST OF IS CODES RELATED TO AGGREGATE TESTING

Tests for Aggregates with IS codes
Property of Aggregate	Type of Test	Test Method
Crushing strength	Crushing test	IS : 2386 (part 4)
Hardness	Los Angeles abrasion test	IS : 2386 (Part 5)
Toughness	Aggregate impact test	IS : 2386 (Part 4)
Durability	Soundness test	IS : 2386 (Part 5)
Shape factors	Shape test	IS : 2386 (Part 1)
Specific gravity and porosity	Specific gravity test and water absorption test	IS : 2386 (Part 3)
Adhesion to bitumen	Stripping value of aggregate	IS : 6241-1971

SPECIFIC GRAVITY & WATER ABSORPTION OF AGGREGATE

SPECIFIC GRAVITY & WATER ABSORPTION OF AGGREGATE (IS:2386-PART 3-1963)

OBJECTIVE

For determination of specific gravity & water absorption of aggregates. 

REFERENCE STANDARDS

IS : 2386 (Part 3) – 1963 – Method of test for aggregates for concrete (Part I) Particle size and shape.

EQUIPMENT & APPARATUS

• Wire basket
• Oven (3000c)
• Container for filling water and suspending the basket
• An air tight container
• Balance[0-10 kg]
• Shallow tray & absorbent clothes. 

PREPARATION OF SAMPLE

The sample to be tested is separated from the bulk by quartering or by using sample divider.

PROCEDURE

1. About 2kg of  the aggregate sample is washed thoroughly to remove fines, drained and then placed in the wire basket and immersed in distilled water at a temperature between 22 to 320C with a cover of at least 50 mm of water  above the top of the basket
2. Immediately after the immersion the entrapped air is removed from the sample by lifting the basket containing it 25 mm above the base of the tank and allowing it to drop 25 times at the rate of about one drop per second. The basket and the aggregate should remain completely immersed in water for a period of 24±0.5 hours afterwards.
3. The basket and the sample are then weighed while suspended in water at a temperature of 22 to 320C. The weight is noted while suspended in water (W1) g.
4. The basket and the aggregate are then removed from water and allowed to drain for a few minutes, after which the aggregates are transferred to one of the dry absorbent clothes.
5. The empty basket is then returned to the tank of water, jolted 25 times and weights in water (W2) g.
6. The aggregates placed in the dry absorbent clothes are surface dried till no further moisture could be removed by this clothe.
7. Then the aggregate is transferred to the second dry cloth spread in a single layer, covered and allowed to dry for at least 10 minutes until the aggregates are completely surface dry. 10 to 60 minutes drying may be needed. The surface dried aggregate is then weighed W3 g.
8. The aggregate is placed in a shallow tray and kept in an oven maintained at a temperature of 1100C for 24 hours. It is then removed from the oven, cooled in air tight container and weighed W4 g. 

CALCULATION

Weight of saturated aggregate suspended in water with basket = W1 g

Weight of basket suspended in water = W2 g

Weight of saturated aggregate in water = (W1-W2)g = Ws g

Weight of saturated surface dry aggregate in air = W4 g

Weight of water equal to the volume of the aggregate = (W3-Ws) g

 SAFETY & PRECAUTIONS

• Use hand gloves while removing containers from oven after switching off the oven.
• Thoroughly clean & dry the container before testing.
• Special care should be taken that no outer air enters when using the balance.
• Use apron & safety shoes at the time of testing.
• All parts of the equipment should always be kept clean. 

CLASSIFY AGGREGATE ACCORDING TO ITS SHAPE

HOW TO CLASSIFY AGGREGATE ACCORDING TO ITS SHAPE?

AGGREGATE CLASSIFICATION [BASED ON SHAPE]

According to shape the aggregate is classified as

• Rounded aggregate
• Irregular or partly rounded aggregate
• Angular aggregate
• Flaky aggregate
• Elongated aggregate
• Flaky and elongated aggregate

Aggregates of different shape

1. ROUNDED AGGREGATE

The aggregate with rounded shape has the minimum percentage of voids ranging from 32 to 33%. It gives minimum ratio of surface area to given volume and hence requires minimum water for lubrication. It gives good workability for the given amount of water and hence needs less cement for a given water cement ratio. The only disadvantages is that the interlocking between its particles is less and hence the development of bond is poor. This is why rounded aggregate is not suitable for high strength concrete and for pavements subjected to tension.

2. IRREGULAR OR PARTLY ROUNDED AGGREGATE

The aggregate with irregular shape has higher percentage of voids ranging from 35 to 37%. It gives lesser workability than rounded aggregate for the given water content. Water requirement is higher and hence more cement is needed for constant water cement ratio. The interlocking between aggregate particles is better than rounded aggregate but not adequate to be used for high strength concrete and pavements subjected to tension.

3. ANGULAR AGGREGATE

The aggregate with angular shape has the maximum percentage of void ranging from 38 to 45%. It requires more water for lubrication and hence it gives least workability for the given water cement ratio. For constant water cement ratio and workability the requirement of cement increase. The interlocking between the aggregate particles is the best and hence the development of bond is very good. This is why angular aggregate is very suitable for high strength concrete and for pavements subjected to tension.

4. FLAKY AGGREGATE

The aggregate is said to be flaky when its least dimension is less than 3/5th (or 60%) of its mean dimension. Mean dimension is the average size through which th particles pass and the sieve size on which these are retained. For example, mean size of the particles passing through 25 mm sieve and retained on 20 mm sieve is (20+25)/2=22.5 mm. if the least dimension is less than 3/5 x (22.5) = 13.5 mm, then the material is classified as flaky. Flaky aggregate tends to be oriented in one plane which affects the durability.

5. ELONGATED AGGREGATE

The aggregate is said to be elongated when its length is greater than 180% of its mean dimension.

6. FLAKY & ELONGATED AGGREGATE

Aggregate is said to be flaky and elongated when it satisfies both the above conditions. Generally elongated or flaky particles in excess of 10 to 15% are not desirable.

CLASSIFY AGGREGATES ACCORDING TO SIZE

HOW TO CLASSIFY AGGREGATES ACCORDING TO SIZE?

According to size the aggregates are classified as:

• Fine Aggregate
• Coarse Aggregate
• All in Aggregate

FINE AGGREGATE

It is the aggregate most of which passes 4.75 mm IS sieve and contains only so much coarser as is permitted by specification. According to source fine aggregate may be described as:

• Natural Sand– it is the aggregate resulting from the natural disintegration of rock and which has been deposited by streams or glacial agencies
• Crushed Stone Sand– it is the fine aggregate produced by crushing hard stone.
• Crushed Gravel Sand– it is the fine aggregate produced by crushing natural gravel.

According to size the fine aggregate may be described as coarse sand, medium sand and fine sand. IS specifications classify the fine aggregate into four types according to its grading as fine aggregate of grading Zone-1 to grading Zone-4. The four grading zones become progressively finer from grading Zone-1 to grading Zone-4. 90% to 100% of the fine aggregate passes 4.75 mm IS sieve and 0 to 15% passes 150 micron IS sieve depending upon its grading zone.

COARSE AGGREGATE

It is the aggregate most of which is retained on 4.75 mm IS sieve and contains only so much finer material as is permitted by specification. According to source, coarse aggregate may be described as:

• Uncrushed Gravel or Stone– it results from natural disintegration of rock
• Crushed Gravel or Stone– it results from crushing of gravel or hard stone.
• Partially Crushed Gravel or Stone– it is a product of the blending of the above two aggregate.

According to size coarse aggregate is described as graded aggregate of its nominal size i.e. 40 mm, 20 mm, 16 mm and 12.5 mm etc. for example a graded aggregate of nominal size 20 mm means an aggregate most of which passes 20 mm IS sieve.

A coarse aggregate which has the sizes of particles mainly belonging to a single sieve size is known as single size aggregate. For example 20 mm single size aggregate mean an aggregate most of which passes 20 mm IS sieve and its major portion is retained on 10 mm IS sieve.

ALL IN AGGREGATE

It is the aggregate composed of both fine aggregate and coarse aggregate. According to size All-in-aggregate is described as all-in-aggregates of its nominal size, i.e. 40mm, 20mm etc. For example, all in aggregate of nominal size of 20mm means an aggregate most of which passes through 20 mm IS sieve and contains fine aggregates also.