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Articles from RECYCLING (214 Articles)

Two Bondi roads have been constructed with 83 tonnes of RCG – equivalent to over 460,000 stubbies.
Two Bondi roads have been constructed with 83 tonnes of RCG – equivalent to over 460,000 stubbies.
 











Demonstrating the performance, cost-effectiveness of RCG

The quarrying and recycled aggregates industries are not the only sectors doing their part to conserve resources and make the most of recycling construction materials. The beverage sector has also demonstrated the benefits of using recovered crushed glass as a substitute for virgin construction materials.
The Packaging Stewardship Forum (PSF) of the Australian Food and Grocery Council (AFGC) has been working with government and industry partners across Australia to deliver recycling, litter reduction and education programs on behalf of its members, which comprise some of Australia’s major beverage companies and their packaging suppliers. 
 
Formed in 2006, the PSF has partnered with a number of local businesses and local government to deliver outcomes for local communities. Two of the most prominent have been road projects on opposite sides of the continent.
 
CASE STUDY 1: WAVERLEY COUNCIL
Waverley Council’s vision is to be an environmentally sustainable community that manages its energy, waste and water resources efficiently.1 Bondi Beach – Australia’s most famous beach – is located in the municipality, attracting Sydney residents and visitors from Australia and around the world.
 
In 2010 Waverley Council embarked on a trial to utilise glass from kerbside recycling collections in road construction, which avoids the dredging of virgin sand from beaches.
 
In a partnership between Waverley Council, the PSF, the Department of Environment, Climate Change and Water NSW, the Roads and Traffic Authority NSW (now Roads and Maritime Services) and the Roads & Transport Directorate of the Institute of Public Works Engineering Australia, two Bondi roads were constructed using 83 tonnes of recovered crushed glass (RCG) – equivalent to more than 460,000 stubbies.
 
The locations were chosen to provide traffic conditions that would adequately test the pavement and meet the RTA’s requirements:
  • Heavy duty pavement – high vehicle count, high percentage of trucks.
  • 100m trial lengths that were level and straight.
  • Three configurations along the trial length, including a control.
The project used RCG as a sand replacement to demonstrate it is an accepted product for use in NSW roads. The results of the finished pavement indicate no noticeable difference in the performance of the pavement, and the non-flexible concrete pavement with 44 per cent RCG actually improved in performance by four per cent.
 
Since construction the pavements have been monitored to assess performance over time.
 
Table 1. Savings from the Blair Street asphalt project.
Table 1. Savings from the Blair Street asphalt project.
POST-PROJECT TESTING
The RCG concrete mix component materials compare with a normal concrete mix as follows.
 
The pavements in both Blair Street and O’Brien Street were visually inspected within six months of construction. At that time no visual changes were noted. The pavements performed as well as expected across all sections, including RCG and the control section. 
 
As part of the project, the pavement’s performance has been monitored every six months since construction against the following measures:
  • Asphalt concrete pavement – visual inspection, rutting, stripping and skid resistance.
  • Concrete pavement – visual inspection, cracking, skid resistance and strength.
  • Asphalt road – no further deterioration of the pavement noted in the routine “drive by” visual inspections. Three years after construction, close visual inspection noted no discernible difference in performance between the three configurations and, during a drive at low speed and at the speed limit, no difference in the “ride” of the road between the sections. There is also no discernible difference with regard to rutting, stripping and skid resistance since being laid.
CONCRETE ROAD
The pavement in O’Brien Street was visually inspected within six months of construction. At that time no visual changes were noted. The pavement performed as well as expected with no signs of wear or deterioration. Visual inspections at six monthly intervals noted no further deterioration until the second year post-construction, where slight visible changes were evident. 
 
In particular, a small number of cracks had appeared but these could be attributed to points of weakness in the adjoining pavement or penetrations in the slab from service drain covers.
 
The section with the least signs of deterioration was the 44 per cent RCG pavement, which could be attributed to the configuration of the pavement. However, it is possible that this is a result of its higher early strength. The strength of the pavement for each section was recorded at initial testing. The highest strength pavement, after 56 days, was the 44 per cent RCG pavement, while the lowest was the 56 per cent pavement.
 
The pavement was also driven along at low speed and at the speed limit. There was no discernible difference in the “ride” of the road between the sections of pavement. Neither settlement nor further deterioration of the road pavement (except for the cracks) was evident.
 
COSTS, BENEFITS
In summary, the road pavement is performing as well as when it was first constructed and no further testing is considered warranted. It appears that the glass content may have actually improved the quality of the pavement, although quality is influenced by many factors including concrete batch, method and time of construction, weather, etc.
 
Overall, the participants in the trial concluded that glass as a sand replacement in both asphalt and concrete pavements was a viable option that did not compromise the quality of the pavement.
 
In the case of the concrete pavement, it is believed it may even improve performance, provided the percentage of sand replaced by glass is not too high.
 
The total cost of producing two trial pavements was about $140,000, including “start-up” costs such as trial mixes and testing. If the costs associated with the project being a trial were removed, the actual cost is estimated at $125,000.
 
While the benefits of this small scale trial are difficult to see, the benefits of using RCG as part of the normal production process for large scale projects could be significant, reducing the cost of the production of concrete and asphalt, because the cost of RCG is less than buying natural washed sand, transporting it from outside the region as supply reduces2 and paying landfill costs for recovered glass. The Blair Street asphalt project indicates a saving of $190 per tonne by using RCG (see Table 1).
 
As the cost of naturally washed sand in Sydney and the cost of landfill increases, the financial benefits of using glass will increase significantly. The environmental benefit of using RCG is significant and growing. For every tonne of RCG used, there is a potential one tonne reduction of glass to landfill and the need to extract virgin sand is also reduced by a tonne, providing a double benefit.
 
CASE STUDY 2: SHIRE OF MARGARET RIVER
The Shire of Augusta Margaret River is a world renowned wine-producing region and popular holiday destination. An estimated 500,000 people visit the region annually, increasing the volume and complexity of the region’s waste stream. Five years ago the shire identified the opportunity to avoid the quarrying of virgin sand by utilising glass collected from kerbside recycling collections in road construction. 
Feedback from Malatesta during the laying of the RCG asphalt mix in Cowaramup was that it compared favourably with a “normal” mix in workability and performance.
Feedback from Malatesta during the laying of the RCG asphalt mix in Cowaramup was that it compared favourably with a “normal” mix in workability and performance.
 
The shire first undertook an analysis of its waste, which identified a potential local glass resource of 1000 tonnes per annum and a regional potential of 2600 tonnes. Financial analysis showed that local processing of glass and the potential reuse of RCG in civil construction applications would dramatically reduce recovery costs (some glass was previously transported to Perth for recycling, the rest landfilled) and significantly increase recycling. 
 
As a result, the shire received $73,100 in funding from the Australian Packaging Covenant to establish a GM-2 System glass reprocessor to crush glass containers from kerbside and drop-off collections and use the RCG in civil construction. The reprocessor has been operational since October 2009 at the Davis Road disposal site as part of an integrated materials recovery facility (MRF) for processing co-mingled recyclables. 
 
In 2011, with funding from the Packaging Stewardship Forum of the AFGC, the shire commissioned the construction of two sections of asphalt pavement to demonstrate the use of RCG from the Margaret River MRF as a viable medium for use in road pavement construction as a replacement for fine aggregate.
 
The results of the finished pavements using RCG indicate no noticeable difference in the performance of the pavement from standard asphalt.
 
PERFORMANCE AND TESTING 
The two demonstration sites constructed in April 2011 involved two 1200m sections of roadway: one with average suburban traffic volumes in Railway Terrace in the main township of Margaret River and the second at Davis Road and Rosa Glen Road, Cowaramup, which was selected because of its high traffic volumes including large trucks. 
 
The asphalt pavement design using five per cent RCG conforms to the relevant AustRoad specifications and Australian Asphalt Pavement Association requirements. The Margaret River site comprises two lanes in both directions 214m in length and 6.5m wide with an overlay area of about 1400m2. Usage is predominantly light motor vehicles. 
 
The Cowaramup site is at a road intersection with an overlay area of about 1200m2, where usage includes up to 14 B-double transport vehicles per day.
 
Table 2. Cost savings from using RCG in asphalt mix compared with standard asphalt.
Table 2. Cost savings from using RCG in asphalt mix compared with standard asphalt.
The shire contracted asphalt supplier Malatesta to undertake sampling and testing prior to commissioning the RCG asphalt mix, to ensure quality standards could be maintained throughout the process. 
 
The RCG asphalt mix comprised about five per cent RCG (supplied by the Margaret River Glass Reprocessing Plant) and replaced the fine aggregate fraction of the mix that would normally be virgin sand. The asphalt specification conformed to Australian Standard AS2150 for both sections and the design was for an equivalent 10mm size dense graded asphalt mix designed for heavy traffic conditions.
 
Feedback from Malatesta during the laying of the RCG asphalt mix was that it compared favourably with a “normal” mix in terms of workability and performance. The site manager also commented on how well the matrix of the mix bound and compacted under the roller, with less movement during compaction. 
 
Based on performance and results of the RCG asphalt mixes on both sites to date, it has proven suitable for residential streets with medium to heavy traffic or subdivision situations. 
 
Monthly inspections were undertaken for three months after construction was completed. No degradation of the finishes were observed in that time. Both surfaces have performed well, with no discernible difference between the RCG product and standard asphalt. 
 
INPUTS, OUTPUTS
Production costs for the demonstration mix were higher than would normally be expected due to transport logistics and the “one off” nature of the production run. Extra bitumen was also required to reduce air voids and there was some extra mixing of the glass into the sand prior to the final batching. No additional costs would be incurred if RCG was part of the normal mixing process. 
 
A financial analysis of the cost of dealing with glass containers before the glass crusher at 2007 prices and volumes was updated in 2010 to reflect the revised situation. The modelling assumes that the cost of landfill at $47 per tonne has remained constant. 
 
The cost saving from using RCG in the asphalt mix compared with standard asphalt was $3896 (see Figure 2). 
 
The benefits of using RCG as part of the normal production process for large scale projects could be significant, because the cost of RCG is less than mining natural resources and paying landfill costs. 
 
By offsetting the costs of processing an average 1500 tonnes of glass per annum against the cost of disposing of container glass in landfill there is an annual net saving to the shire of $40,010. 
 
As the cost of naturally washed sand in Western Australia and the cost of landfill increases, the financial benefits of using RCG will increase significantly. 
 
MARKETS FOR RCG
The two case studies have shown RCG product available commercially in Australia can be blended with natural and recycled aggregates. It can be used in concrete and asphalt as a fine aggregate material that can be blended with other natural aggregates prior to mixing with the other components in concrete and asphalt. 
 
The maximum recommended blend for sealed and unsealed roads is five to 10 per cent, for heavy duty granular base 15 per cent and 30 per cent for pavement sub-base and light duty roadbase.
 
The product can also be used as engineering fill or blended with natural or crushed sands for use as pipe or bock paving bedding, as defined in the relevant specifications. 
 
Source: AFGC
 
REFERENCES & FURTHER READING


















Monday, 25 June, 2018 02:18am
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