1.0
INTRODUCTION
The type of rocks and type of crushing machine highly determine the shape and size of the aggregates produced. Elongated and flack stones are normally not very suitable for road works since the shape and size make them difficult to compact. As such the flakiness and elongation test must be carried out to determine the suitability of the material. The flakiness index of an aggregate is the percentage by weight of particles in it whose dimension (thickness) is less than three fifths of their mean dimension. This test is not applicable to material passing a ¼ inch (6.35 mm) BS sieve. The flakiness index is the total weight of the material passing the various thickness gauges or special sieves, expressed as a percentage of the total weight of the sample with the sieve analysis. If required the weight of each fraction gauged to the nearest whole number and shall be reported together passing the thickness gauge or special sieve shall be reported as a percentage of the weight of the fraction. The elongation index of an aggregate is the percentage by weight of particles whose greatest dimension (length) is greater than 1 4/5 times their mean dimension. Normally, the properties of interest to the engineer are sufficiently covered by the flakiness or angularity tests. The elongation test is not applicable to material passing a ¼ inch (6.35mm) BS sieve. The elongation index is the total weight of the material retained on the various length gauges, expressed as a percentage of the total weight of the sample gauged to the nearest whole number and shall be reported together with the sieve analysis. If required the weight of each fraction retained on the length gauge shall be reported as a percentage of the weight of the fraction.
2.0
OBJECTIVE To determine the flakiness and elongation indices of the given aggregate sample.
3.0
FLAKINESS INDEX Aggregate particles are classified as flaky when they have a thickness (smallest dimension) of less than 0.6 of their mean sieve size. The flakiness index of an aggregate sample is found by separating the flaky particles and expressing their mass as a percentage of the mass of the sample tested. This test is not applicable to aggregate passing 6.30mm sieve and retained as 63.0 mm sieve.
3.1
APPARATUS
3.2
Metal thickness gauge
Test sieve
Balance
Trays
PROCEDURE 1. Weight each of the aggregate which passing sieve 28mm, 20mm, 14mm and 10mm. Each aggregate was weighted according to weight given which are 5000g, 2000g, 1000g and 500g separately. 2. The aggregate was gauge each fraction from the respective slots in the thickness gauge. Put the aggregate in the separate trays for passing the slots and not passing the slots. 3.
Weight each trays and record the data in the table.
4.0
ELONGATION INDEX Aggregate particles are classified as elongation when they have a length (greatest dimension) of more than 1.8 of their mean sieve size. The elongation index is found by separating the elongation particles and expressing their mess as a percentage of the mass of sample tested. The test is not applicable to material passing 6.30 mm sieve or retained on 50 mm sieve. 4.1
4.2
APPARATUS
Metal length gauge
Sieve
Balance
Trays
PROCEDURE 1. Weight each of the aggregate which passing sieve 28mm, 20mm, 14mm and 10mm. Each aggregate was weighted according to weight given which are 5000g, 2000g, 1000g and 500g separately.
2. The aggregate was gauge each fraction from the respective slots in the metal length gauge. Put the aggregate in the separate trays for passing the slots and not passing the slots. 3.
5.0
Weight each trays and record the data in the table.
RESULTS AND DATA ANALYSIS No.
Passing
Retained
Sieve
Sieve
(mm)
(mm)
1
28
20
2
20
3 4
Sample
(
Retained (gm)
(gm) F(Xn)
E
F
E(Yn)
5000
832.5
1040.1
4167.5
3959.9
14
2000
206.7
120.0
1793.3
1880.0
14
10
1000
92.7
940.0
907.3
60.0
10
6.3
500
65.7
440.2
434.3
59.8
Total
8500
1197.6
2540.3
7302.4
5959.7
1. Calculation for Flakiness Index (
Passing (gm)
) )
(
)
2. Calculation for Elongation Index (
)
( (
) )
From our results of flakiness and elongation index, we conclude that the aggregates are suitable to be used as a road base with a reference from JKR SPJ/2008-S4, section 4.2.3.2, item III. The flakiness index when tested in accordance with MS 30 shall not be more than 25%. 6.0
DISCUSSION Determining the flakiness and elongation of the given aggregate sample is simple. The error that may affects the results were considered minor in regards to sensitivity of the balance. Flakiness and elongation gauges are reliable instrument to measure as long as it passes the thickness gauge or retained on length gauge. The objective of the experiment is achieved and used to identify the suitability to be used as crushed aggregate road base. Crushed aggregate road base material shall be crushed rock, crushed gravel or a mixture of crushed rock and gravel, which shall be hard, durable, clean and essentially free from clay and other deleterious materials. The material shall conform to the following physical and mechanical quality requirements which one of it is:1. The flakiness index when tested in accordance with MS 30 shall not be more than 25%.
Flakiness index and elongation index are important physical properties of mineral aggregates which affect the quality of concrete mixes. The presence of flaky and elongated aggregates beyond certain limits decreases compressive strength and causes extreme harshness in concrete mixes. Flaky and elongated particles may have adverse effects on concrete and bituminous mix. For instance, flaky and elongated particles tend to lower the workability of concrete mix which may impair the long-term durability. For bituminous mix, flaky particles are liable to break up and disintegrate during the pavement rolling process. Hence flaky and elongated particles are considered undesirable as they cause weakness of the pavement. Flakiness Index is the percentage by weight of particles in it, whose least dimension (i.e. thickness) is less than three-fifths of its mean dimension. Elongation Index is the percentage by weight of particles in it, whose largest dimension (i.e. length) is greater than one and four-fifths times its mean dimension. 7.0
CONCLUSION Our experiment is successful as we managed to determine the flakiness and elongation index. Its flakiness index is 14% which is way below JKR Requirement for Crushed Aggregate Road base for Paved Roads in section 4 Flexible Pavement. The objective of the experiment is achieved and used to identify the suitability to be used as crushed aggregate road base.
8.0
REFERENCES 1. A Closer Look at Prevailing Civil Engineering Practice – What, Why and How by Vincent T. H. CHU.
2. Standard Specification for Road Works, Section 4 Flexible Pavement, JKR/SPJ/2008-s4, Jabatan Kerja Raya Malaysia, Kerajaan Malaysia
3. http://www.cipremier.com/e107_files/downloads/Papers/100/34/100034046.pdf 4. http://socyberty.com/military/flakiness-and-elongation-test-bs-812-part-iii/
