EXPERIMENT : AGGREGATE IMPACT VALUE

OBJECTIVE

To determine the impact value of the road aggregates.To assess their suitability in

road construction on the basis of impact value.This test is done to determine the

aggregate impact value of coarse aggregates.Many tests have been developed to

empirically characterize aggregate properties without, necessarily, strong

relationships to the performance of final products incorporating an aggregate.This

seems to be particularly true for aggregate “toughness and abrasion resistance”

and “durability and soundness.” The objective of this research is to select tests for

characterizing aggregate toughness/abrasion resistance and durability/soundness

that are related to the performance of asphalt concrete pavements.

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THEORY

This lack of understanding has led to the development of design methods

that tended to overemphasize the need for superior aggregate properties, rather

than the development of innovative design methods to accommodate a wide range

of aggregate properties.

. A number of alternative tests have been used to assess the aggregate

breakdown throughout the European Union. Some of these test methods, such as

aggregate crushing value, ten percent fines value, and aggregate impact value, are

included in the British standards 812.

The Aggregate Impact Value (British Standard 812-Part 112) provides a

measure of the resistance of aggregates to impact. To conduct the test, a specimen

is compacted into an open steel cup.The sample is subjected to a number of

impacts from a dropping weight. This action breaks the aggregate to a degree

which is dependent on the impact resistance of the material.

Classification of aggregates using Aggregate Impact Value is as given below:

Aggregate Impact Value Classification

<20% Exceptionally Strong

10-20% Strong

20-30% Satiisfactory for road surfacing

>35% Weak for road surfacing

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SAFETY & HEALTH

The basic purpose of these safety instructions is to protect students, researchers,

technicians and teachers from the many hazards that might be encountered during

the use of the various materials and equipment in the geotechnic laboratory.

Ethics in safety and health is very importance. This is because in order to avoid

any injury occurs.

Before Practical Work

I. Knows locations of first aid and eye station.

II. Wear appropriate clothing for easy work.

III. Follow all instructions lecturer.

During practical work

I. No running, eating, drinking or smoking while conduct practical work.

II. Ensure the equipment used in good condition.

III. Take a reading of the sample correctly.

IV. Wear gloves when entering the sample in oven care for themselves and

friends.

V. Do not joke when using the tools.

VI. Do practical work under the surveillance of lecturer.

After Practical Work

I. Store the equipment after using it carefully.

II. Make sure the hole is dug filled up again to avoid any injury occurring in

the future.

III. Follow further instructions from the lecturer after testing is complete.

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APPARATUS

testing machine weighing

cylindrical steel cup

tup weighing

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cylindrical metal

rod

balance

PROCEDURE

The test sample consists of aggregates sized 10.0 mm.Aggregates may be dried by

heatinf at 100-110˚C for a period of 4 hours and cooled.

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i. Sieve the material through 14.0mm and 10.0mm sieves.The aggregates passing

through 14.0 mm sieve and retained on 10.0 mm sieve and retained on 10,0 mm

sieve comprises the test material.

ii. Pour the aggregates to fill about just 1/3 rd depth of measuring cylinder.

iii. Compact the material by giving 25 gentle blows with the rounded end of the

tamping rod.

iv. Add two more layers in similar manner,so that cylinder is full.

v. Strike off the surplus aggregates.

vi. Determine the net weight of the aggregates to the nearest gram (W).

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vii. Bring the impact machine to rest without wedging or packing up on the level

plate,block or floor ,so that it is rigid and the hammer guide columns are vertical.

viii. Fix the cup firmly in position on the base of machine and place whole of the test

sample in it and compact by giving 25 gentle strokes with tamping rod.

ix. Raise the hammer until its lower face is 380mm above the surface of aggregate

sample in the cup and allow it to fall freely on the aggregate sample.Give 15 such

blows at an interval of not less than one second between successive falls.

x. Remove the crushed aggregate from the cup and sieve it through 2.36mm sieves

until no further significant amount passes in one minute.Weigh the fraction

passing the sieves to an accuracy of 1 gm.Also,weigh the fraction retained in the

sieves .

Compute the aggregate impact value.The mean of two observations,rounded to

nearest whole number is reported as the Aggregate Impact Value.

RESULT

S1 S2

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Total weight of dry sample (W1 g) 629.9 545.1

Weight of portion passing 2.36 mm(W 2g) 65.2 69.4

Aggregate Impact Value (percent)=W2 /W1X

100

16.43% 12.73%

CALCULATION:

S1 = 65.7 / 629.9 x 100 = 10.43%

S2 = 69.4 / 54.51 x 100 = 12.73%

RESULT:

Aggregate Impact Value

(10.43% + 12.73%) / 2 = 11.58%

NOTES

a) Refer to JKR Standart Specification For Roadworks.

b) Classification of aggregates using Aggregate Impact Value is as given below:

Aggregate Impact Value Classification

<20% Exceptionally Strong

10-20% Strong

20-30% Satiisfactory for road surfacing

>35% Weak for road surfacing

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CONCLUSION

Based on the result obtained, the percentage of impact value is

35.71%.Aggregate impact value is used to determine sustainability of aggregate

due to dynamic loading.

As we know, aggregates is an important material used for road

construction, therefore, traffic loading will be the chief loading for a roadway.

Aggregates used for road construction should be able to sustain heavy loading

applied. This parameter is measured by impact test. From the test carried out, we

known that the sample has high impact value. This showns that percentage not

unsustainable to heavy loading.

After carried out impact test, we can conclude that the sample has an

aggregate impact value of 35.71%.The result is under JKR specification that is

25%.So,it is the weak for road surfacing. This showns that the the aggregate are

not be used in road construction because the aggregate fragile and easily broken

when compressed. According to JKR specific aggregate of more than 35% should

not be applied.

Aggregates must be tough and abrasion resistant to prevent crushing,

degradation, and disintegration when stockpiled, fed through an asphalt plant,

placed with a paver, compacted with rollers, and subjected to traffic loadings.

These properties are especially critical for open or gap graded asphalt concrete

mixtures (such as open-graded friction courses and stone matrix asphalt) which do

not benefit from the cushioning effect of the fine aggregate and where coarse

particles are subjected to high contact stresses.

Aggregates which lack adequate toughness and abrasion resistance may

cause construction and performance problems. Degradation occurring during

production can affect the overall gradation and, thus, widen the gap between

properties of the laboratory designed mix and field produced mix.

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REFERENCE

1)Internet

a) www.engineeringcivil.com/aggregate- impact - value .html

b) civilx.unm.edu/laboratories_ss/mechmat/charpy.html

c) fismapedia.org/index.php?title=Term:Moderate- Impact _System

d) sroi.london.edu/Measuring-Social- Impact .pdf

e) ec.europa.eu/culture/key.../study_ impact _cult_creativity_06_09.pdf

2)Book

a) A Guide Book for Beginners,Ratnasamy Muniandy,Radin Sohadi,Penerbit

UPM,2001

3)Library

a) Library Politeknik Sultan Abdul Halim Mu’adzam Shah

b) Perpustakaan Awam Alor Star.

4)Module

a) Highway Engineering CC302.

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