Aggregate Impact Value

Centre for Diploma Studies (CeDS) Department of Civil Engineering Title: Aggregate Impact Value

Date: 17 October 2016

1.0 Introduction Impact value of an aggregate is the percentage loss pf weight of particles passing 2.36mm sieve by the application on load by mean of 15 blows of standard hammer and drop under specified test condition. The aggregate impact value gives a relation measure of the resistance of an aggregate to sudden shock or impact, which in some aggregates differs from their resistance to a slowly applied compressive load. General: Normally the aggregate impact value of base course is 30, bituminous bound macadam is about 35 and the cement concrete base course is 30. Significance: The test gives an idea of toughness of the aggregate to resist facture under the impact of moving loads. 2.0 Objectives To determine the aggregate impact value in the laboratory. 3.0 Apparatus 1. Impact Testing Machine: Its consists of a cylindrical hammer of 13.5 kg. (30Ibs) sliding freely between two vertical supports (called guides). Its fall is automatically adjusted to a height of 38cm. There is a brass plate over which an open cylindrical steel cup of internal diameter 10.2cm and 5cm depth is placed and fixed to the brass plate. 2. Measure: A cylinder of internal diameter 7.5cm and 5cm deep for measure aggregate. 3. Tamping rod of I cm diameter and 23cm long rounded at one end and pointed at the other end. 4. Sieves: 12.5mm, 10mm and 2.36mm opening. 5. Balance: 5000g capacity. 6. Laboratory oven capable of maintaining a constant temperature up to 1100C.



Apparatus for the Aggregate Impact Value Test 4.0 Procedure 1. Sieve the aggregate and obtain the portion passing 12.5mm and retained on 10mm sieve. 2. Wash and dry this aggregate at a constant temperature of 1050C to 1100C and then cool the sample. 3. Fill this aggregate in the cylindrical measure in 3 layers, tapping each layers 25 times with the tamping rod. Level the surface tamping road as a using the straight edge. 4. Weight the aggregate in the measure. This weight of the aggregate is used for the duplicate test on the same material. 5. Transfer the aggregate from the cylindrical measure to the cup in 3 layers and compact each layer by tamping in 25 strokes with the tamping rod. 6. Release the hammer for fall freely on the aggregate. The test sample is subjected to a total of 15 blows. 7. Remove the aggregate sample from the cup and sieve through 2.36 mm sieve. 8. Weight the fraction passing the sieve. 5.0 Forms and Calculation

Weight Sample

Of Cup (Gm)

Weight Before Crush (Gm)

Weight Retained

Weight Passing

2.36 Mm Sieve

2.36 Mm Sieve

(Gm)

(Gm)


A

0.78

B

0.78

1.08 – 0.78 = 0.30 1.07 – 0.78 = 0.29

Average


0.521 – 0.38 = 0.141

0.304 – 0.24 = 0.064

0.576 – 0.38 = 0.196

0.324 – 0.24 = 0.084

0.169

0.074

0.295

Weight Loss × 100 ( Initial Weight )

Percent Wear ( Average ) =

× 100 ( 0.0074 0.315 )

Percent Wear ( Average ) =

= 23%

Percent Wear (Average)

23 %

6.0 Discussion The experiment indicated a few improvements to the problem state: a) The distance of the person hand while tamping may cause different result. Tamping layer also can affect the error reading because it’s done manually and not consistence with the others. b) The brass plate are not closed may cause reduction to the weight of sample after being crushed. The aggregate will fall out from brass plate because of the hammer



was released freely and fall on the aggregate. The height of hammer and brass plate can also be the factor to the error data. 7.0 Conclusion Base on the experiment, the value percentage wear (average) was 23%. The value from the experiment is more than the requirement of JKR’s; 15%. The aggregate physical property must lower Aggregate Impact Value, AIV because is tougher and resistance to crushed. These experiments are successful because its exceed the JKR’s requirement 8.0 References 1. Aggregate Testing: Aggregate Impact Value & Flakiness and Elongation lab sheet. 2. https://www.scribd.com/doc/86556593/Aggregate-Impact-Value

Aggregate Impact Value

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