Coarse Aggregate Test
Aggregates are the most basic material used in construction. Whether you’re constructing a parking lot, driveway, or sidewalk, the foundation of the infrastructure requires high-quality aggregate. Aggregates are a raw material used extensively in the construction of streets, concrete, tiles, bridges, and beyond.
They provide the foundation for roads, bridges, and buildings, while also making up over 90% of asphalt pavement and up to 80% of a concrete mix. On average, 38,000 tons of aggregates are necessary to construct one lane mile of interstate highway. Construction of the average home requires 400 tons of aggregate, while the average size school or hospital requires 15,000 tons.
Why Aggregate Testing Is Important?
Aggregates play an important role in the construction sector and can be used for different projects. Aggregates are an important element in the making of concrete and offer several benefits. Their primary use is to strengthen concrete, strengthening its structure and thus minimizing instances of cracks.
Therefore, before utilizing aggregates for construction purposes they must be tested and checked for quality. Many kinds of research on aggregate reveal that the quality of aggregate has a major factor in the quality of concrete and ultimately the construction.
Aggregate used in construction are tested for the following parameters,
The aggregates are tested to determine their properties like,
- Water Absorption etc.
A good coarse aggregate should possess the following characteristic,
- It should be angular or cubical in shape.
- It must be sound & durable.
- A Good Coarse Aggregate should be absolutely clean and free from any organic matter, chemicals and coating of clay.
- It should be hard and tough.
List of Aggregate Test
- Impact Test on Aggregates
- Crushing Test on Aggregates
- Abrasion Test on Aggregates
- Soundness Test on Aggregates
- Shape Test on Aggregates (Elongation & Flakiness Index)
- Specific Gravity and Water Absorption Test on Aggregates
- Bitumen Adhesion Test on Aggregates
Various Test on Aggregate
The following are the aggregate testing methods,
1. Impact Test on Aggregates
What Is Impact Value Of Aggregate?
It is the ability of aggregates that resist sudden impact or shock load on it. Also, it can be defined as the resistance of aggregate to failure by impact load is known as the Impact Value of Aggregate.
Importance of Impact Test on Aggregates
The impact test on aggregate is carried out to know the response of aggregates to different kinds of loads that the aggregates will be subjected to during their service life.
The need for impact value test is used to measure the toughness of aggregates which is nothing but the ability of aggregates to resist the sudden loading or impact loading.
Apparatus for Impact Test
- Aggregate impact apparatus,
- IS sieves (12.5 mm, 10.0 mm and 2.36 mm),
- Cylindrical measure and cylindrical cup,
- Weighing balance,
- Tamping rod.
Maximum Allowable Impact Value of Aggregate for Different Types of Pavements
|Sr. No.||Types of Pavements||Aggregate Impact Values (Max.)|
|1||Water Bound Macadam (WBM) Sub- Base Course||50|
|2||Cement Concrete, Base Course||45|
|3||i) WBM base course with bitumen surfacing||40|
|ii) Built up- Spray grout, base course|
|4||Bituminous macadam, base course||35|
|5||i) WBM, surface Course |
ii) Buit-up spray grout, surface course
iii) Bituminous penetration macadam
iv) Bituminous macadam, binder Course
v) Bitumen surface dressing
vi) Bitumen carpet
vii) Bituminous / Asphaltic concrete
2. Crushing Value Test of Aggreagte
What Is Crushing Value?
Aggregate Crushing value is a relative resistance of aggregates to crushing under gradually applied compressive load.
Aggregate Crushing Value Test is important to test to be performed on aggregate. The strength of aggregate parent rock is determined by preparing cylindrical shape specimens of size 25 mm diameter and 25 mm height.
IS Code For Crushing Value Test
Aggregate Crushing value test IS Code is 2386-4 (1963): Methods of Test for Aggregates for Concrete
Aggregate Crushing Value Apparatus
- A 15 cm dia. Steel cylinder with plunger and base plate.
- A straight metal tamping rod 16mm diameter and 45 to 60 cm long rounded at one end.
- A Weigh balance of accuracy up to 1 gram.
- IS sieves of sizes 12.5 mm, 10mm, and 2.36 mm.
- A compression testing machine.
- Cylindrical measure having a diameter of 11.5 cm and 18 cm height.
- A compression testing machine having a loading capacity of 40 tones and which can be operated to give a uniform rate of loading so that the maximum load is reached in 10 minutes.
Aggregate Crushing Value Limits for Road Pavement
|Types of Roads / Pavements||Aggregate Crushing Value Limit|
|Water bound macadam||40|
|Bituminous surface dressing or thin premix carpet||30|
|Dense mix carpet||30|
|Other than wearing course||45|
|Surface or Wearing course||30|
3. Abrasion Test Of Aggregate
What Is Abrasion Test?
Abrasion Test is the measure of aggregate toughness and abrasion resistance such as crushing, degradation and disintegration. This test is suggested by AASHTO T 96 or ASTM C 131: Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in Los Angeles Machine.
IS Code For Abrasion Test of Aggregate Test
Apparatus used for Abrasion Test
- Los Angeles abrasion machine
- Abrasive charge balls: Cast iron or steel balls, approximately 48 mm in diameter and each weighing between 390 to 445 gm; six to twelve balls are required.
- Sieve: 1.70mm , 2.36mm, 4.75mm, 6.3mm, 10mm, 12.5mm, 20mm, 25mm, 40mm, 50mm, 63mm, 80mm IS Sieves.
- The balance of capacity 5 kg or 10 kg is used.
- Oven Drying.
- Miscellaneous elements like a tray.
IS Recommended Los Angeles Abrasion Value of Aggregate for Pavements
4. Shape Test on Aggregates (Elongation & Flakiness Index)
Flakiness and Elongation Index Test are very important tests to be performed on aggregate in the laboratory. This test gives the percentage of flaky and elongate aggregate present in the total aggregate sample.
The flakiness index of aggregate is the % by weight of the particles (aggregates) whose thickness is less than 3/5th(0.6 times) of their mean dimension.”
The Elongation index of aggregate is the % by weight of the particles (aggregates) whose length is greater than 1 and 4/5th (1.8 times) of their mean dimension.”
IS Code For Test
Elongation and Flakiness Index Test is conducted as per IS 2386 (Part 1) – 1963 PDF.
- Metal gauge
- The IS Sieves: 63 mm, 50 mm, 40 mm, 31.5 mm, 25 mm, 20 mm, 16 mm, 12.5 mm, 10 mm, 6.3 mm.
IRC recommended the Flakiness Index Value
IRC recommended the Flakiness index value for road construction is below 35%.
|SR NO.||TYPE OF CONSTRUCTION||ALLOWABLE FLAKINESS INDEX|
|lower granular layer||15%|
|4||Two coat bituminous surface dressing||25%|
|6||Dense bituminous macadam||35%|
5. Specific Gravity and Water Absorption Test of Coarse Aggregate
Specific gravity and Water Absorption Test of Aggregates are major important tests to be performed on aggregate. These two parameters or properties of aggregate play an important role in the mix design of concrete. As we know that aggregate occupies 70 to 80% volume of concrete, its testing becomes essential before use.
“Specific Gravity is defined as the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water.”
The specific gravity is usually showed the strength and quality of the material. The specific gravity of aggregates test is usually used for the identification of stones or aggregates.
Water absorption of aggregates is the % of water absorbed by an air-dried aggregate when immersed in water at 27°C for a period of 24 hours.
Reference IS Code Test
Reference:- Specific Gravity of Fine Aggregate as per IS Code 2386 (Part 3) – 1963 PDF
Reference: Water absorption test for coarse aggregate Is Code 2386 (Part 3) – 1963 PDF
Apparatus For Test
- Wire Basket
IS Reccomanded Values
- The specific gravity of coarse aggregate as per IS code is 2.5 to 3.
- The water absorption of aggregate ranges from 0.1 to 2%.
6. Soundness Test on Aggregates
The soundness of aggregate refers to the durability of an aggregate in terms of the resistance to the action of weather and is an indication of the resistance to weathering of fine and coarse aggregates.
Soundness is the % loss of material from an aggregate blend during the sodium or magnesium sulphate soundness test. This test, which is specified in ASTM C88 and AASHTO T104, estimates the resistance of an aggregate to in-service weathering. It can be performed on both coarse and fine aggregate.
The test is performed by exposing an aggregate sample to repeated immersions in saturated solutions of sodium or magnesium sulphate followed by oven drying. One immersion and drying is considered one soundness cycle.
During the drying phase, slats precipitate in the permeable void space of the aggregate. Upon reimmersion, slat rehydrates and exerts internal expansive forces that simulate the expansive forces of freezing water.
The rest result is total percentage loss over various sieve intervals for a required number of cycles. Maximum loss values typically range from 10% to 20% for five cycles.
IS Code for Soundness Test of Aggregate
Followings are the standard guidelines for the soundness test on aggregates:
Apparatus for Soundness Test
- Sodium Sulphate or Magnesium Sulphate Solution,
- Weighing Balance
- IS Sieves
- Weight Balance
7. Bitumen Adhesion Test
The adhesion between mineral aggregates and bitumen is an important criterion that describes the quality of the asphalt mixture, asphalt pavement performance, and resistance to distress. The lack of bonding can lead to significant asphalt pavement damage.
For the evaluation of the adhesion behavior between bitumen and aggregates, used in road construction, many test methods are known. Therefore, it is important to assess the most appropriate test method for bitumen adhesion properties.
Standard Code For Test
Following IS Code used for the bitumen adhesion test on aggregates.
- IS:6241- 1971
Apparatus of Bitumen Adhesion Test
- Water Bath,
- Mixer to mix aggregate and bitumen.
Bitumen Adhesion Test Procedure
- Take a sample of 200 gm of dry aggregates passing a 20mm sieve and retained on 12.5mm sieve and 5 % by weight of bitumen binder.
- Mix the binder and the aggregates till they are fully coated.
- Then transfer the mixture into a 500ml beaker and allow to cool at room temperature for about 2 hours.
- Next, add distilled water and immerse the coated aggregates.
- Cover the beaker and keep in a water bath for 24 hours.
- Now take the beaker out and let it cool at room temperature.
- The uncovered area needs to be observed visually.
You May Also Like
- Aggregate Impact Value Test | Impact Test of Aggregate | Impact Value | AIV Test
- Aggregate Crushing Value Test – Procedure and Result
- Abrasion Test on Aggregate | Los Angeles Abrasion Test
- Flakiness and Elongation Index Test of Coarse Aggregate | Flakiness Index | Elongation Index | Result
- Specific Gravity and Water Absorption Test of Coarse Aggregate | Specific Gravity of Coarse Aggregate