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 110oC 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)
Aggregates
Aggregates are inert granular materials such as sand, gravel or crushed stone that are an end product in their own right. They are also the raw materials that, along with water and hydraulic binders, are an essential ingredient in concrete. For a good concrete mix, aggregates need to be clean, hard, strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete.
Aggregates, which account for 60 to 75 percent of the total volume of concrete, are divided into several distinct categories, and are either coarse or fine:
Coarse aggregates
Coarse aggregates are particles greater than 4.75mm, but generally range between 9.5mm to 37.5mm in diameter. They can either be from Primary, Secondary or Recycled sources. Primary, or 'virgin', aggregates are either Land- or Marine-Won. Gravel is a coarse marine-won aggregate; land-won coarse aggregates include gravel and crushed rock. Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder.
Coarse Aggregates
Fine Aggregates
Fine aggregate are basically sands won from the land or the marine environment. They are less than 4.75mm. Fine aggregates generally consist of natural sand or crushed stone with most particles passing through a 9.5mm sieve. As with coarse aggregates these can be from Primary, Secondary or Recycled sources.
Sand
AGGREGATE CRUSHING VALUE
Aggregate Crushing Value Test is for determining the aggregate crushing value of coarse aggregates.
APPARATUS
i) Cylindrical measure and plunger
ii) Compression testing machine
iii) IS Sieves of sizes - 12.5mm, 10mm and 2.36mm
PROCEDURE
i) The aggregates passing through 12.5mm and retained on 10mm IS Sieve are oven-dried at a temperature of 100 to 110oC for 3 to 4hrs.
ii) The cylinder of the apparatus is filled in 3 layers, each layer tamped with 25 strokes of a tamping rod.
iii) The weight of aggregates is measured (Weight 'A').
iv) The surface of the aggregates is then levelled and the plunger inserted. The apparatus is then placed in the compression testing machine and loaded at a uniform rate so as to achieve 40t load in 10 minutes. After this, the load is released.
v) The sample is then sieved through a 2.36mm IS Sieve and the fraction passing through the sieve is weighed (Weight 'B').
vi) Two tests should be conducted.
REPORTING OF RESULTS
Aggregate crushing value = B/A x 100%
The result should be recorded to the first decimal place and the mean of the two results reported.
AGGREGATE ABRASION VALUE
This test helps to determine the abrasion value of coarse aggregates as per IS: 2386 (Part IV) – 1963.
The apparatus used in this test are Los Angles abrasion testing machine, IS Sieve of size – 1.7mm, Abrasive charge – 12 nos. cast iron or steel spheres approximately 48mm dia. and each weighing between 390 and 445g ensuring that the total weight of charge is 5000 +25g and Oven.
Sample Preparation
The test sample should consist of clean aggregates which has been dried in an oven at 105 to 110oC to a substantially constant weight and should conform to one of the gradings shown in the table below:
Procedure to determine Aggregate Abrasion Value
The test sample and the abrasive charge should be placed in the Los Angles abrasion testing machine and the machine rotated at a speed of 20 to 33 revolutions/minute for 1000 revolutions. At the completion of the test, the material should be discharged and sieved through 1.70mm IS Sieve.
Reporting of Results
i) The material coarser than 1.70mm IS Sieve should be washed, dried in an oven at a temperature of 100 to 110oC to a constant weight and weighed (Weight ‘B’).
ii) The proportion of loss between weight ‘A’ and weight ‘B’ of the test sample should be expressed as a percentage of the original weight of the test sample. This value should be reported as,
Aggregate abrasion value = (A-B)/B x 100%.
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
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 110oC 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').
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 110oC 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.
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.
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)
Aggregates
Aggregates are inert granular materials such as sand, gravel or crushed stone that are an end product in their own right. They are also the raw materials that, along with water and hydraulic binders, are an essential ingredient in concrete. For a good concrete mix, aggregates need to be clean, hard, strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete.
Aggregates, which account for 60 to 75 percent of the total volume of concrete, are divided into several distinct categories, and are either coarse or fine:
Coarse aggregates
Coarse aggregates are particles greater than 4.75mm, but generally range between 9.5mm to 37.5mm in diameter. They can either be from Primary, Secondary or Recycled sources. Primary, or 'virgin', aggregates are either Land- or Marine-Won. Gravel is a coarse marine-won aggregate; land-won coarse aggregates include gravel and crushed rock. Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder.
Coarse Aggregates
Fine Aggregates
Fine aggregate are basically sands won from the land or the marine environment. They are less than 4.75mm. Fine aggregates generally consist of natural sand or crushed stone with most particles passing through a 9.5mm sieve. As with coarse aggregates these can be from Primary, Secondary or Recycled sources.
Sand
AGGREGATE CRUSHING VALUE
Aggregate Crushing Value Test is for determining the aggregate crushing value of coarse aggregates.
APPARATUS
APPARATUS
i) Cylindrical measure and plunger
ii) Compression testing machine
iii) IS Sieves of sizes - 12.5mm, 10mm and 2.36mm
ii) Compression testing machine
iii) IS Sieves of sizes - 12.5mm, 10mm and 2.36mm
PROCEDURE
i) The aggregates passing through 12.5mm and retained on 10mm IS Sieve are oven-dried at a temperature of 100 to 110oC for 3 to 4hrs.
ii) The cylinder of the apparatus is filled in 3 layers, each layer tamped with 25 strokes of a tamping rod.
iii) The weight of aggregates is measured (Weight 'A').
iv) The surface of the aggregates is then levelled and the plunger inserted. The apparatus is then placed in the compression testing machine and loaded at a uniform rate so as to achieve 40t load in 10 minutes. After this, the load is released.
v) The sample is then sieved through a 2.36mm IS Sieve and the fraction passing through the sieve is weighed (Weight 'B').
vi) Two tests should be conducted.
REPORTING OF RESULTS
Aggregate crushing value = B/A x 100%
The result should be recorded to the first decimal place and the mean of the two results reported.
AGGREGATE ABRASION VALUE
This test helps to determine the abrasion value of coarse aggregates as per IS: 2386 (Part IV) – 1963.
The apparatus used in this test are Los Angles abrasion testing machine, IS Sieve of size – 1.7mm, Abrasive charge – 12 nos. cast iron or steel spheres approximately 48mm dia. and each weighing between 390 and 445g ensuring that the total weight of charge is 5000 +25g and Oven.
Sample Preparation
The test sample should consist of clean aggregates which has been dried in an oven at 105 to 110oC to a substantially constant weight and should conform to one of the gradings shown in the table below:
Reporting of Results
i) The material coarser than 1.70mm IS Sieve should be washed, dried in an oven at a temperature of 100 to 110oC to a constant weight and weighed (Weight ‘B’).
ii) The proportion of loss between weight ‘A’ and weight ‘B’ of the test sample should be expressed as a percentage of the original weight of the test sample. This value should be reported as,
Aggregate abrasion value = (A-B)/B x 100%.
Sample Preparation
The test sample should consist of clean aggregates which has been dried in an oven at 105 to 110oC to a substantially constant weight and should conform to one of the gradings shown in the table below:
Procedure to determine Aggregate Abrasion Value
The test sample and the abrasive charge should be placed in the Los Angles abrasion testing machine and the machine rotated at a speed of 20 to 33 revolutions/minute for 1000 revolutions. At the completion of the test, the material should be discharged and sieved through 1.70mm IS Sieve.
The test sample and the abrasive charge should be placed in the Los Angles abrasion testing machine and the machine rotated at a speed of 20 to 33 revolutions/minute for 1000 revolutions. At the completion of the test, the material should be discharged and sieved through 1.70mm IS Sieve.
i) The material coarser than 1.70mm IS Sieve should be washed, dried in an oven at a temperature of 100 to 110oC to a constant weight and weighed (Weight ‘B’).
ii) The proportion of loss between weight ‘A’ and weight ‘B’ of the test sample should be expressed as a percentage of the original weight of the test sample. This value should be reported as,
Aggregate abrasion value = (A-B)/B x 100%.
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