1.0 Introduction
The type of rocks and the type of crushing machine highly determine the shape and size of the aggregates produced. Elongated and flaky stones are normally not very suitable for road works since the shape and the size make them difficult to compact. As such the flakiness and elongation test must be carried out to determine the suitability of the material.
2.0 Objective
To determine the flakiness index of aggregates.
3.0 Apparatus
a. A metal gauge plate
Figure 3.1: A metal gauge plate
4.0 Methodology
a. Three samples of aggregates weighing 2.5kg each are prepared.
i. Aggregates passing 50mm BS sieve and retained on 37.5mm BS sieve.
ii. Aggregates passing 37.5mm BS sieve and retained on 28mm BS sieve.
iii. Aggregates passing 28mm BS sieve and retained on 20mm BS sieve.
b. Each sample is gauge in turn of thickness on metal gauge.
c. The passing material of each sample is weighed.
5.0 Result
PASSING SIEVE (mm) | RETAINED SIEVE (mm) | SAMPLE (kg) | PASSING (kg) | RETAINED (kg) | FLAKINESS INDEX (%) | ELONGATION INDEX (%) |
20 | 14 | 1 | 0.2064 | 0 | 20.64 | 0 |
14 | 10 | 1 | 0.0956 | 0 | 9.56 | 0 |
|
Flakiness index (%) = Nos. passing Total Nos. Aggregate
|
1 = 20.64 %
Average Flakiness Index (%) = Summation of all fractions No. of fractions
= 20.64 + 9.56 2
= 15.1%
Elongation index (%) = Nos. passing Total Nos. Aggregate
|
1 = 0%
Average Elongation Index (%) = Summation of all fractions No. of fractions
= 0 2
= 0%
6.0 Discussion
Road as one of land transportation infrastructure is very important in supporting the economic for both regional and national development. The quality of material for road construction will also influence the road performance. Asphalt concrete as one of road surface material is mainly influenced by the quality of aggregates since aggregate occupies 95% by weight in total mixture. Various shapes of aggregates might be occurred during crushing in the crushing plant starting from rounded to flaky and elongated aggregates. The JKR requirement is not exceed 20% to make sure that the aggregate are suitable for road construction materials.
7.0 Recommendations
a. The more sample weight more difficult to count the aggregate but we can calculated using the right calculation.
b. Sample are not been forced to pass the metal gauge plate. It’s to make sure that we get the accurate data.
c. We the process, we need to have different tray to make sure all aggregate counted and not missed.
8.0 Conclusions
The value that we get from this test is 15.1% for flakiness and not exceeds 20% the JKR requirement. Elongation value is 0% because the aggregate is rounded so no any retain value. Aggregate quality for road construction will also influence the road performance. The flakiness and elongation rocks are not suitable for road construction because this type of rocks will make the road surface not balance and easy to damage.
9.0 Reference
a. Bambang I. , Journal of the Eastern Asia Society for Transportation Studies, Vol. 6, pp. 1302 – 1312. Workability and Resilient Modulus Of Asphalt Concrete Mixtures Containing Flaky Aggregates Shape; 2005. Available from: URL: http://www.easts.info/on-line/journal_06/1302.pdf
b. Muniandy R., Radin Umar Radin Sohadi. Highway Materials, A Guide Book For Beginners. University Putra Malaysia : Penerbit Universiti Putra Malaysia
c. Paul H.W., Karen K.D. Highway USA
d. Construction Quality Assurance. Introduction. 1(1): [8 screen]. Available from: URL: http://www.durocrete.com/Flakiness.pdf
10.0 Appendix
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