Question

1. How does the toughness of road aggregates differ from their compressive strength? Can you write a mathematical relationship, if any?
2. A test group of the class used an old aggregate impact test machine. The weight of the hammer was about 1 kgf lower than the standard weight. Determine the percentage error in the impact value of the aggregate.
3. Should a poor-quality road aggregate give a low impact value? Justify your answer.
4. The Los Angles abrasion test is applied to natural aggregate particles used in construction of pavements. Is it true? Justify your answer.
5. Discuss the effect of the number of revolutions of the rotating drum used in the Los Angeles abrasion test on the Los Angeles value.
6. A test group A used 11 steel balls while another test group B used 9 steel balls for conducting the Los Angeles abrasion test of aggregates. Compare the Los Angles values obtained by these two groups in terms of percentage difference.
7. Based on your laboratory test report, select the type of aggregates for their use in Perth. Also report the values of the aggregates as you select.
8. The impact value test has been explained in the video demonstration as available at the BB unit site. Do you think all the groups will get the same value of impact value of the aggregate? Justify your answer.
9. You have prepared the laboratory test report for all the tests as planned for this unit, and so you have now enough experience of conducting the tests. In future, you may establish your own pavement consultancy company. Write the proper order of tests in decreasing importance as you may need to prepare for the clients. Also, provide the cost in AUD of each test as you would like to charge for these tests, including GST.
10. Write the values of water absorption and particle density of aggregates as you reported in your laboratory report. Compare these values with those for aggregates used in making the bituminous concrete in Perth.
11. Is there any relationship between the particle density and specific gravity of aggregate particles? Explain briefly.

Answer 1

Toughness is the ability of aggregate to absorp energy and to deform plastically without rupture i.e it is the ability of aggregate to resist impact which is created by tyre wheels in the road where compressive strength is the ultimate force/ load that an aggregate can sustain before failure.

Toughness can be determined by integrating the stress strain curve.

General hammer weight = 14.5 kg

Given hammer force = 1 kgf less than stadard weight

Free fall of hammer = 380 mm= 0.38 m

Error = 1*0.38/100 = 0.0038%