ENVIRONMENTALLY SUSTAINABLE USE OF RECYCLED ASPHALT AT OR TAMBO INTERNATIONAL AIRPORT

1. 33rd Annual Southern African Transport Conference 2014 ENVIRONMENTALLY SUSTAINABLE USE OF RECYCLED ASPHALT AT OR TAMBO INTERNATIONAL AIRPORT PRESENTED BY: Moyagabo Makgoka 7 July 2014

2. INTRODUCTION • Bachelor of Technology: Civil: Construction Managementfrom University of Johannesburg • GIBB (Pty) Ltd since 2011 • Assistant Resident Engineer on various Pavement Rehabilitation projects at OR Tambo International Airport

3. PROJECT Landside Pavement Rehabilitation at OR Tambo International Airport (2013) The project involved the rehabilitation of the cargo area at OR Tambo International Airport (ORTIA). The use of this environmentally sustainable technology resulted in massive cost savings to the client and allowed the contractor to effectively work in a highly congested area using conventional asphalt paving and milling equipment.

4. Project Team

5. Locality Map CARGO AREA

6. CARGO AREA • The cargo area used by non South African Airways (SAA) operators. • Made up of two sections: • Outside area where trucks deliver goods to the operators (“landside”) • Inside area where the goods are placed on airside equipment to be moved to the aircraft.

8. Pavement Condition Overview of Design Approach

9. 1. Visual Assessment (Asphalt) Cargo Area (Outside)

10. Visual Assessment (Asphalt) Cargo Area (Inside)

11. Visual Assessment Summary Cargo Outside: Failures similar to the traditional Macadam base failures i.e. potholes occur with loose, large stones exposed. Cargo Inside: The thin surface breaking up and resulting in water ingress to an already poor base. Localised base failures were visible over the whole area.

12. 2. Materials Investigations: Test Pits Cargo Area (Outside) • The crushed stone base was relatively thin (110mm) and a thin asphalt layer (30mm) • Severe crocodile/block cracking in due to aged and brittle surface. • Surface disintegration due to traffic and aged layers • Weakening of upper layers due to water ingress

13. 2. Materials Investigations: Test Pits Cargo Area (Inside) • Very thin asphalt surface layers made up of seal and slurry combination resulting in limited protection of base layers which are weakening as a result of water ingress • Poor subbase of clay-like structure • Severe crocodile cracking in areas due to aged and brittle surface

14. Materials Investigations: FWD Tests

15. FWD results Outside cargo area has one entrance and exit on southern end. Therefore the area closer to the gate was more damaged than the section away from the gate toward the Northern side

16. 3. Traffic • Cargo statistics indicated a current total cargo value of 350 000 tons (200 000 tons imports and 150 000 tons exports) • Daily import volumes estimated at 410 tons per day = 45 fully loaded trucks (2 axles) • Approximately 200 outgoing daily movements • Relatively light air type of cargo resulting in lower traffic in terms of E80s with less than 5000 E80s expected annually. This explaining how the thin flexible pavement structure survived more than 20 years.

17. 4. Limitations • Limited to night work. Less hours in weekdays. • Small areas of work at a time • Budget • Mill & fill operation (area had to be in ‘ride-able’ condition end of each shift) • Level of surface at truck offloading/loading platform to remain unchanged

18. Rehabilitation Options Considered

19. Warm Mix Asphalt with 55% Recycled Asphalt 110 mm Foamed Bitumen Treated Base (+ 55% RA) 30 mm Asphalt Wearing Course

20. Details Standard rehabilitation design approach was followed but not necessarily in the “correct” order. The fast track nature of the design stage (6 weeks allowed) resulted in test pits conducted immediately upon appointment, non-destruction pavement testing next and traffic counts at a later stage Based on standard Bitumen Treated Base (BTB) grading. Special attention give to screening of RA to ensure accurate grading (2% added bitumen), Superheating of virgin aggregate (45%) to ensure proper mixing with RA at correct mixing temperature

21. Details Standard method in paving process, except for reduced temperature No vibratory compaction conducted (Kinematic rollers followed by standard wheel rolling) due to poor subbase/subgrade conditions

22. ACSA CASE STUDIES USING RA Airport Company South Africa (ACSA) as in the case of many road authorities primarily use virgin construction materials. Waste materials (i.e. milled asphalt material) were mostly spoiled or used as unbound selected materials. Since 2005, ACSA has encouraged consultants to be innovative in pursuit of more cost effective design solutions. Using higher quantities of RA being on the forefront of these solutions Various combinations of RA and binder type (standard hot binders, foamed bitumen and emulsion) have been used.

23. ACSA CASE STUDIES USING RA

24. ACSA CASE STUDIES USING RA Projects where RA between 10% -25% was used (Hot mix asphalt) with success on heavy duty code F taxiways including Echo, Hotel, Alpha, Yankeeand Charlie. Up to 35% RA using Foamed Bitumen (Warm mix asphalt). - Shoulder rehabilitation of Kilo and Lima Taxiways (2011). Cost Effective and remains in durable condition. -Whiskey Apron rehabilitation (2011). Foamed bitumen allowed contractor to achieve high densities with limited static roller compaction (poor base conditions)

25. ACSA CASE STUDIES USING RA Up to 80% RA using Emulsion (Cold Mix) and 20% crusher dust. November and Tango shoulder extensions. Small fillet construction (1200m²) in restricted area in limited hours. Projects with 100% RA (Cold mix). Haul Roads and “temporary” Patrol roads. These patrol roads where given a two year service life. 4 years later they were still in impressive condition.

26. Environmental Impact and Sustainability

27. Effects of Asphalt Production on the Environment Published embodied energy and emissions values • G Hammond et Al (2006) Note 1: To be used in pavement design estimates/ # When asphalt is used as waste product i.e. RA incorporated in the mix

28. Effects of Asphalt Production on the Environment Calculated embodied energy and emissions values *Amount of material used x units energy/emission values

29. NOTE • The Environmental Impact can be reasonably accurately estimated using published embodied energy and emissions values of various construction materials. However accuracy is dependant on: • Promoters or manufacturers giving true information. • Evaluation of entire process is required to calculate the cost and environmental benefits • - manufacturing • - transportation of materials (aggregates, bitumen and additives) • - construction • - life cycle (maintenance?) • Example 1: • Promoters of warm mix asphalt have said there is a 10% saving in fuel due to lower temperature usage, however in looking at all components involved as above, it translated to only 2% saving in embodied energy of asphalt. • Example 2: • Environmental Benefits vs Cost Benefits.

30. CONCLUSION In addition to the potential environmental benefits (reduced CO² and energy efficient), the use of Recycled asphalt also has the added benefit of handling heavily trafficked areas requiring fast rehabilitation in a short space of time. With correct quality control measures achieved at the plant, the product has the potential to perform on the same standard and in some instances even better that conventional mixes.

31. THE END THANK YOU