Page 2 - Open Access - Jan 2020

point of view

• slowing resource loops or flows (the retention of products, 3. consIdErIng all IMpacts
and their constituent materials, in the economy for longer
periods). The OECD report provides a useful overview of the “vast
number of Life Cycle Assessments (LCAs) that assess recycling
• narrowing resource flows (generating additional economic relative to other end of life options”. It identifies how few
value from a fixed amount of natural resources)” (p20). consider all impacts, stresses the importance of LCAs
comparing “apples with apples” and highlights the difficulty in
They return to these three mechanisms at key points in the doing this.
report which explores 5 business models:
It is worth considering two examples where all impacts must be
• Circular Supply – close material loops
considered in order to determine the optimum environmental
• Resource Recovery – close material loops outcome: the choice of when and where to use recycled
aggregates and by whom; and, the choice of building design
• Product Life Extension – slow material loops strategy between demountable and durable.

• Sharing – narrow resource flows
Firstly aggregates. Engineers used to contact The Concrete
• Product Services System – narrow resource flow Centre in the UK where I worked wanting to know about
recycled aggregates, and more specifically all the reasons
Readers will be able to identify examples of these models in our they could give clients for NOT using recycled aggregates in
sector. their projects (pre 2006). We observed that this changed over
a couple of years to engineers still wanting to know about
In terms of material production: Circular Supply - recycle recycled aggregates, but now they wanted to use them. No
concrete aggregates to replace virgin aggregates thereby matter the motivation of the query the answer to the underlying
“replacing traditional material inputs”; and, Resource Recovery - question of “Should I specify recycled aggregates in concrete
use of fly ash and ggbs as secondary cementitious materials “to for environmental reasons?” remained the same: it depends.
produce secondary raw materials from waste”.

In terms of design: Product Life Extension – increasing design Academia and industry has and continues to do an excellent
life through specification of concrete, cover and/or non-ferrous job of establishing the concrete technology understanding
reinforcement “to extend product lives”. behind use of recycled aggregates in concrete, ensuring
standards are in place that permit use of recycled aggregates
In terms of asset management, the OECD highlight the AirBnB and equipping the clients, consultants, supply industry and
business model as an example of Sharing which results in contractors to accept, specify, manufacture and build with
“increased utilisation of assets”. An example of Product Services them. This work is ongoing as evidenced in the pages of this
System business model is harder to come by in the cement edition of the journal and the September 2019 edition. This
and concrete industry, but these models are characterised valuable work addresses potential impediments to use of
by application of new technology, retention of ownership recycled aggregates in concrete. It enables the use of recycled
and narrowing resource flows. These three characteristics are aggregates when it will deliver an improved environmental
seen in the ready-mixed industry where in-transit concrete outcome. However, sometimes it gives a better environmental
management through internet connected sensors provide real outcome for available recycled aggregates not to be used in
time monitoring and control and “product ownership remains concrete and for virgin aggregates to be used in the concrete.
with the supplier” – in this case the technology is the product, Additional transportation, additional resources to ensure quality
the supplier might be the admixture company and the narrowing and additional cementitious content in the concrete are all
of resource flow arises from avoidance of over specification. The reasons why use of recycled aggregates in concrete may not be
italicised quotes above are the key characteristics in the OECD the optimum choice. If all potentially recycled aggregates are
report (p25) for each of their business models. being recycled and used in construction, then the aggregates/
concrete industry itself is best placed to determine where the
The OECD report recognises that their 5 business models are recycled aggregates are deployed. The system boundary in LCA
already being applied and explores how they can become terms for concrete and recycled concrete aggregates should be
more widespread? It also considers when their application may the whole aggregates industry, and not the subset of concrete,
not deliver an improved environmental outcome and what to avoid adverse outcomes. The main ambition of the broader
the potential downside might be of rebound effects. Finally it aggregates sector in each geographic area should be to use
recognises that society’s demands cannot be met by reuse and all potentially available recycled and secondary aggregates in
recycling alone and that virgin materials are still needed. place of virgin aggregates.

20 The IndIan ConCreTe Journal | JanuarY 2020