1. M. B Mgangira, S XUNGU and J GIANI
AN INVESTIGATION OF AGGREGATE DEGRADATION IN A HIGH STRESS FIELD
M. B Mgangira, S XUNGU and J GIANI
Southern Africa Transport Conference 2018
CSIR International Conference Centre
10 July 2018

2. DEMONSTRATION RESULTS
PRESENTATION
INTRODUCTION
CONTEXT
CONCEPT
DEMONSTRATION RESULTS
CONCLUDING REMARKS
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3. Thank you INTRODUCTION Background Ultimate goal
Research initiatives on aggregate characterisation
Ultimate goal
Quantify aggregate abrasion resistance and therefore durability solely dominated by particle-to-particle interaction mechanism
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4. Optimisation in the use of aggregates
CONTEXT
Optimisation in the use of aggregates
Impact on long-term stability of pavements
Introduction

5. CONTEXT
Test methods to evaluate the durability or quality of aggregates, resistance to abrasion, involving some form of particle to particle interaction under, for example:
L.A abrasion (LAA)
Aggregate Crushing Value (ACV),
Aggregate Impact Value (AIV),
Durability Mill Index (DMI)
Aggregate Durability Index (ADI)
Micro-Deval (MDE).
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6. CONTEXT
A charge of steel balls is used to induce aggregate wear
The interior of the drum is mounted with a shelf which picks up and drops the aggregates and the steel balls as the drum rotates
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7. CONTEXT
To provide coherent body of knowledge on aggregate degradation solely dominated by particle-to-particle interaction mechanism
Quantify the influence of stress levels on rate of aggregate degradation
Establish an experimental system
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8. Thank you CONTEXT Concept
An experimental system, to assist in the evaluation of aggregate quality, using a customised rolling model drum, in which the aggregate assemblage is subjected to different stress levels
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9. Thank you CONTEXT Concept
Numerical simulations are restricted to spherical particles, mainly because of the high computational costs
Solution available in physical modelling: Increase the self weight of the aggregates
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10. Use of Geotechnical centrifuge to increase self weight of aggregates
CONCEPT
Use of Geotechnical centrifuge to increase self weight of aggregates
Introduction

11. Thank you CONCEPT Concept F = M.a
The magnitude of the induced, normal contact and tangential forces, between the particles are a result of the g-level during the testing
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12. Thank you CONCEPT Granular flow
This will be possible if the behaviour of the mass of the particles in the model drum is further dominated by cascading and cataracting behaviour
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Cascading
Cataracting

13. Thank you CONCEPTS Granular flow Cascading and Cataracting behaviour
Centrifuging

14. CONCEPT
Concept
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15. Longitudinal Cracking
TESTING SYSTEM
Testing
10g
20g
100rev/min
5 minutes
Longitudinal Cracking

16. DEMONSTRATION RESULTS
Sieve analysis
Particle shape analysis
Particle volume (V)
Particle surface area (SA)
Longitudinal Cracking

17. DEMONSTRATION RESULTS
Longitudinal Cracking

18. DEMONSTRATION RESULTS
Longitudinal Cracking

19. DEMONSTRATION RESULTS
Longitudinal Cracking

20. RESULTS

21. CONCLUDING REMARKS
Experimental platform has demonstrated the possibility of quantifying aggregate degradation solely due to particle-to-particle interaction mechanism

22. CONCLUDING REMARKS Future work:
Flow of particles involves complex particle–particle and particle–wall interactions and, depending on the particle physical characteristics and drum operating conditions, can display different flow regimes

23. CONCLUDING REMARKS Future work:
Effect of the pay-load (filling ratio) in the model drum during the testing.
The testing of mixtures of various particle sizes
influence of wet and dry test conditions
Different types of rock samples.

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