ReCon 2016 was the first national seminar of the year and attracted a wide range of delegates from the built environment sector including engineers, contractors, concrete product manufacturers, material suppliers and more.
The event was held in Somerset West, Port Elizabeth, Durban and Kempton Park
The seminar focused on re-using, reducing and recycling concrete and looked at the topic holistically, covering the status quo in South Africa, a view of the European situation as far as recycling concrete aggregate was concerned, demolition waste; machinery used for recycling, what the local readymix industry is doing on recycling wet concrete, hardened concrete and waste water; current research initiatives and some case studies.
From comments made by delegates and the speakers, it is believed that the content was relevant, useful and up-to-date.
The presentations given were:
Myths and truths around concrete recycling – Bryan Perrie/John Roxburgh, The Concrete Institute
This covered an overview of the reasons why recycling is becoming so necessary, what prognosis might be if the industry does not adopt recycling and some of the myths and truths that prevail. These were quoted as being:
- Concrete cannot be recycled
- Recycled concrete cannot be used in structural concrete
- It is not possible to recycle high rates
- Recycling will reduce carbon footprint
- Recycled aggregate is more expensive
- Cement cannot be recycled
- Demolished concrete is inert
- Recycled concrete can be better than virgin aggregate
- Using recycled concrete reduces land-use impact
- Recycling will not meet aggregate needs
Following a description of the some of the many applications to which recycled concrete can be put, the speaker concluded by stating that:
- There are significant benefits to recycling concrete
- For high volume usage, there is a need for good controls and site sorting
- The industry needs legislation regarding construction and demolition waste in landfills
- There is a need for the design of new buildings to consider reuse and recycling
A secondary materials economy in construction and demolition waste - opportunities and challenges in concrete – Kirsten Barnes, GreenCape
The speaker began by describing who GreenCape were and their role in the industry. GreenCape is a sector development agency of the Western Cape government – their mandate being to stimulate the green economy in the Western Cape, with all activities externally funded (at no cost to industry). They also explore the national context, and assist with networking in other provinces where possible.
The presentation described the main drivers of a secondary materials economy:
- Increasing cost of virgin materials
- Siting new quarries
- Regulation of waste flows through national, provincial and local legislation
- Landfill space – heading for a crisis
A brief look at matching the quality of secondary materials with the retaining highest material quality/value, from backfill to re-concreting.
Re-concreting is the highest value application, but is the lower volume opportunity and seems to have more barriers to uptake than aggregate for construction foundations and roads. The trend is the same globally, with re-concreting a relatively late developer in the growth of a secondary material economy.
Sustainable concrete, the European experience – Mark Tomlinson, LafargeHolcim Group
This guest speaker from overseas presented some insight into the recycling activities by some European countries. It was reported that recycling rates in the EU range from around 10% in Spain, whilst the Netherlands is achieving more than 90% recovery rate.
In the opinion of the presenter the concrete industry needs to improve its sustainability credentials, and the development of recycled concrete is a viable way of achieving this. Recycling can lead to higher profitability through additional revenue and logistics cost savings. It improves resource efficiency and generally improves the competitiveness of concrete (competing materials such as timber, steel and asphalt claim 100% recyclability).
The speaker then went on to report on two research projects currently under way in France. Firstly - Recybéton, with the objective of reusing all the materials obtained from demolished concrete, even the fines, as components of new concretes, and to recycle the fine grain size part of demolished concrete as raw material for the manufacture of cements (either to produce clinker or as an addition into a blended cement). The research programme is scheduled to be complete by mid-2016.
Secondly - the HISER project (Holistic Innovative Solutions for an Efficient Recycling and Recovery of Valuable Raw Materials from Complex Construction and Demolition Waste). The main objective here is to develop and demonstrate novel cost-effective holistic solutions (technological and non-technological) to increase the recovery rates from increasingly complex Construction and Demolition Wastes (C&DW), according to the principles of circular economy approach throughout the whole value chain in the construction sector.
The proposed solutions will be demonstrated in 5 case studies across Europe (Belgium, The Netherlands, Spain, France and Finland) in demolition and recycling projects. Moreover, economic and environmental impact of HISER solutions will be quantified from a viewpoint of lifecycle (LCA / LCCA), and recommendations for European standardization policies and standards for the implementation of the best solutions will be proposed.
Using Recycled construction waste in concrete – a sustainable approach to conserving aggregates through the use of excavated sand, recycled bricks and recycled concrete – Vernon Collis/Kyle Wickins, Collis & Associates
The speaker outlined the various types and status of construction and demolition waste (C&DW) material, particularly in the Western Cape. Landfills were reaching capacity and moving further
from the city in the Cape, and there were dwindling pit sand sources in the region.
A very interesting graph was then shown explaining recycling C&DW in the waste hierarchy – see below:
Identifying components of value
Upcycling – cleaning and reusing material
Downcycling – crushing C&DW for aggregates
How to use in concrete
Results of extensive testing carried out by a Masters student at UCT on site-derived sands were described, and turning this material into a valuable resource was discussed. Several case studies were portrayed utilising these materials and emphasising the need for a different approach to design – i.e. materials first, design second.
Manufacturing quality green, environmentally friendly concrete products: a case study – Anthony Gracie, Cape Brick
This was a fascinating look at recycling in practice by this company which started processing and using their first recycled aggregate in 2000. In 2001 they ran out of waste and then partnered with a demolition company to import demolition material.
Up until the present they have used almost 1 million tons of recycled concrete aggregates in their products, processing around 400 tons per day in the manufacturing process.
Delegates were exposed to the challenges, in some detail, that were faced when sourcing external material, such as:
- The make-up of the material
- Varying types of materials
- Cost versus benefit
- Constant availability
- Material size
- Space to store material
- Local authority issues (waste licences, etc.)
Following a comprehensive description of the block-making manufacturing process, the speaker summarized his presentation with the following checklist:
- Make sure you get the right material
- Crush it properly
- Separate the fractions
- Wet the raw material
- Batch it accurately
- Cut down the variables in the manufacturing
- Employ good “in process” quality controls
- Cure the product properly
- Learn from your mistakes
Equipment for recycling: an overview – Shane Clark, Infinite Group
This presentation comprised a holistic study of the various processes used to create demolition waste – i.e. through explosive, chemical, hydro, cutting or mechanical (everything from a swinging ball to a ‘Mega Muncher’) methods.
Details of the various items of equipment were shared together with the features and benefits of each machine. Various pros and cons of using each method were discussed, depending upon the important things to consider such as location, time, cost, penalties, etc.
Moving on to the recycling of concrete the speaker provided an insight into a specialised mobile crusher that is currently available for producing a very high classification material. It features a small single stage jaw crusher, a magnet for removing steel, a spray nozzle to reduce dust and an on-board weighing machine. It is hydraulically adjustable, lighter and easier to transport and does not require abnormal load permits.
The presentation concluded with a case study demonstrating the features of this unique machine.
Recycling opportunities in the ready-mixed concrete industry – Johan van Wyk, Southern Africa Readymix Association
The focus here was on current practice within the southern African readymix industry when it comes to recycling water, fresh concrete and hardened concrete.
The speaker explained how typically a readymix plant would recover its ‘grey’ water and citing South African specification SANS 51008:2004 Clause A3, which states the limitations on the use of water recovered from processes in the concrete industry. He then described the various tests that are carried on the recovered water, to ensure that good concrete is produced from its use.
Recycled fresh concrete is used for either moulding (into concrete products), paving, redirecting or recovering aggregates. Recycled hardened concrete is used for recovering aggregates through chemical addition. The chemical is added to the truck, agitated and then the mix spread open. The concrete is turned in 24 hours, and can be used in new concrete.
This type of recovered aggregate can increase strengths, due to the improved inter-facial zone.
Recovery can also be achieved by washing out the aggregates. The aggregates can be screened into fractions for use in new concrete batches.
In producing new concrete using recycled materials careful attention has to be paid to grading of the aggregates, replacement rates, mix design and quality/consistency.
Question times in most venues were very vigorous and interactive which clearly illustrated the interest in the subject matter.
Thanks were expressed to Lafarge South Africa as the main sponsor for the national seminar, and to others sponsors at the various venues around the country, namely:
BASF, Chryso-abe, The Concrete Institute, Mapei, PPC, SIKA
Thanks were also expressed at each venue to Natasja Pols and Marike van Wyk from Head Office for organizing such a professional and smooth-running event.