Tests of aggregates

different types of aggregate tests

1. TEST OF AGGREGATES

2. TESTS OF AGGREGATES AGGREGATE ABRASION VALUE AGGREGATE IMPACT VALUE AGGREGATE CRUSHING VALUE SPACIFIC GRAVITY TEST

3. AGGREGATE ABRASION VALUE AIM :- To determine the abrasion value and hardness property of aggregates as per IS: 2386 (Part IV) - 1963. APPARATUS :- 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 Oven

4. PURPOSE :- Due to the movements of traffic, the road stones used in the surfacing course are subjected to wearing actions at the top. When traffic moves on the road the soil particle (sand) which comes between the wheel and road stone. Abrasion test are carried out to test the hardness property of stones and to decide whether they are suitable for the different road structure. PREPARATION OF SAMPLE :- 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 grading shown in the table below:

5. Sieve size Weight in g of test sample for grade A B C D E F G Passing through (mm) Retained on (mm) 80 63 - - - - 2500 - - 63 50 - - - - 2500 - - 50 40 - - - - 5000 5000 - 40 25 1250 - - - - 5000 5000 25 20 1250 - - - - - 5000 20 12.5 1250 2500 - - - - - 12.5 10 1250 2500 - - - - - 10 6.3 - - 2500 - - - - 6.3 4.75 - - 2500 - - - - 4.75 2.63 - - - 5000 - - -

6. PROCEDURE : - clean and dry aggregate sample confirming to one of the grading A to G is used for the test. Aggregates weighing 5kg for grading A, B, C or D and 10kg for grading E, F or G may be takes as test specimen and placed in the cylinder. The abrasive charge is also chosen in accordance with table no.1 and placed in the cylinder of the machine, and cover is fixed to make dust tight. The machine is rotated at a speed of 30 to 33 revolutions per minute. The machine is rotated for 500 revolutions for grading A, B, C and D, for grading E, F and G, it shall be rotated for 1000 revolution. After the desired number of revolution the machine is stopped and the material is discharged from the machine taking care to take out entire stone dust. Using a sieve of size larger than 1.70mm IS sieve, the material is first separated into two parts and the finer position is taken out and sieved further on a 1.7mm IS sieve. let the original weight of aggregate be w1 gm, weight of aggregate retained on 1.7mm IS sieve after the test be w2 gm.

7. AGGREGATE IMPACT VALUE AIM :- To determine the aggregate impact value of coarse aggregates as per IS: 2386 (Part IV) - 1963. APPARATUS :- Impact testing machine conforming to IS: 2386 (Part IV)- 1963 IS Sieves of sizes - 12.5mm, 10mm and 2.36mm A cylindrical metal measure of 75mm dia. and 50mm depth A tamping rod of 10mm circular cross section and 230mm length, rounded at one end Oven

8. PREPARATION OF SAMPLE The test sample should conform to the following grading: - Passing through 12.5mm IS Sieve 100% - Retention on 10mm IS Sieve 100% The sample should be oven-dried for 4hrs. at a temperature of 100 to 110oC and cooled. 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').

9. PROCEDURE 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. 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.

10. REPORTING OF RESULTS 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. The ratio of the weight of the fines formed to the total sample weight should be expressed as a percentage. Aggregate impact value = x 100% Two such tests should be carried out and the mean of the results should be reported.  

11. AGGREGATE CRUSHING VALUE AIM :- To determine the aggregate crushing value of coarse aggregates as per IS: 2386 (Part IV) - 1963. APPARATUS :- Cylindrical measure and plunger Compression testing machine IS Sieves of sizes - 12.5mm, 10mm and 2.36mm

12. PROCEDURE :- The aggregates passing through 12.5mm and retained on 10mm IS Sieve are oven-dried at a temperature of 100 to 110 for 3 to 4hrs. The cylinder of the apparatus is filled in 3 layers, each layer tamped with 25 strokes of a tamping rod. The weight of aggregates is measured (Weight 'A'). 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. The sample is then sieved through a 2.36mm IS Sieve and the fraction passing through the sieve is weighed (Weight 'B'). Two tests should be conducted.  

13. REPORTING OF RESULTS :- Aggregate crushing value = x 100%  

14. SPACIFIC GRAVITY TEST AIM :- To Determine Specific Gravity and water absorption of aggregate. PURPOSE :- The specific gravity of an aggregate is considered to be a measure of strength or quality of the material. Stones having low specific gravity are generally weaker than those with higher specific gravity value. The specific gravity test helps in identification of stone. Water absorption gives an idea of strength of rock. Stones having more water absorption are porous in nature and are generally considered unsuitable unless they are found to b acceptable based on strength, impact and hardness testes.

15. PROCEDURE :- About 2kg of the coarse aggregate sample is washed thoroughly to remove fines, drained and then placed in the wire basket and immersed in distilled water at a temp between and C and covered of at least 5cm of water about the top of the basket. Immediately after immersion the entrapped air is removed from the sample by lifting the basket 25 mm above the base of the tank and allowing it to drop 25 times at the rate of above one drop per second the basket and aggregate should remain completely immersed in water for a period of 24+1/2 and 24-1/2 hrs afterwards. The basket and the sample are then weighed well suspended in water at a temp of and C in case it is necessary to transfer the basket and the sample to a different tank for weighing, they should be jolted 25 times a described above in the new tank to remove air before weighing. The weight is noted while suspended in water = gm.  

16. The basket and the aggregate are then remove from water and allowed to drain for a few minutes, after which the aggregate are transferred to one of the dry absorbent clothes. The basket is then return to the tank of water, jolted 25 times and weighed in water = gm. The aggregate then placed to direct sunlight or any other source of heat while surface drying. The drying of aggregate must be done naturally. The surface dried aggregate is then weighed = gm. The aggregate is placed in tray and kept tray in an oven at a temperature of C for 24 hrs. and then weighed it = gm.  

17. sr. no Details Test number 1 2 Mean value 1 Weight of saturated aggregate and basket in water = gm 2 Weight of basket in water = gm 3 Weight of saturated surface dry aggregate in natural air = gm 4 Weight of oven dried aggregates = gm 5 Specific gravity = = 6 Apparent Specific gravity = = 7 Water absorption = * 100% sr. no Details Test number 1 2 Mean value 1 2 3 4 5 6 7

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