Recycled construction materials: a purchase specification beats a circularity slogan

Beyond the performance class, several questions determine whether a recycled material can be used at scale on a project, and each is easier to answer before specification than after.

Intended use is the first and frames everything else. A material acceptable in a non-structural fill application may be unacceptable in a structural one, and a material acceptable in an external application may be unacceptable where it is exposed to a particular chemical environment. The application must be stated precisely, because 'recycled aggregate' covers an enormous range of materials of very different quality.

Contaminants are the second. Recycled streams carry the history of what they were before, and that history determines what is in them. The relevant contaminants depend on the source and on the application, and establishing acceptable limits is a specialist question that must be answered by qualified parties for the specific use.

Testing is the third, and it follows from the second. A specification should state what is tested, to what method, at what frequency, by whom, and against what acceptance criteria. A single certificate relating to a single sample does not establish the properties of a continuing supply.

Traceability is the fourth. Knowing where a material came from, and being able to demonstrate it, is what allows a deviation to be investigated and a claim to be substantiated. Traceability also underpins the circularity claim itself: a claim of recycled content that cannot be traced to a source is an assertion.

Consistent supply is the fifth, and it is the one most often discovered late. Recycled streams vary. A material that performed to specification in a trial may perform differently in a later delivery as the source stream changes. The specification should address how variation is managed, what the supplier must notify, and what happens when a delivery falls outside the acceptance criteria.

Transport distance belongs alongside these. A recycled material hauled a long distance to the site may carry a greater transport burden than a locally available primary material, which is why the comparison should be made on a consistent basis rather than assumed to favour the recycled option.

Where a recycled material is specified, the question of who bears the risk if it does not conform is frequently left until it arises, at which point it is expensive to resolve.

The risk is real and it is different in character from the risk attaching to a primary material, because the variability of a recycled stream is inherently greater than that of a controlled primary product. That is not an argument against using recycled materials. It is an argument for allocating the risk deliberately in the contract, in the same way that any material with variable characteristics would be handled.

The allocation should address what evidence the supplier must provide, what happens if a delivery fails to meet the specified criteria, who bears the cost of the investigation and of any replacement, and how a disputed test result is resolved. Settling these in the specification and the contract, rather than when a problem emerges, is what makes using a recycled material a manageable decision rather than an open-ended one.

The Commission published a Construction and Demolition Waste Protocol in 2024, which addresses how construction and demolition waste should be managed, including provisions relating to pre-demolition and pre-renovation audits. [D] It is a useful document and it is relevant to how recovered materials are generated and characterised.

It is important to place it correctly in time. This article covers a reference period beginning in 2022, and the 2024 protocol did not exist then. Where the article refers to it, it does so as retrospective context — an account of how thinking in this area developed — and not as a purported legal requirement applying during 2022. To present it otherwise would be to backdate a requirement, which would misrepresent the position at the time.

The distinction is not pedantic. A reader trying to understand what governed a project in 2022 needs to know what applied then, and a reader considering a project now needs to know what applies now. Blurring the two serves neither, and it is the kind of error that makes a retrospective unreliable.

The analytical discipline set out above — specify by use, establish performance, control contaminants, test, trace, secure supply, allocate risk — transfers between markets without modification. It describes how to specify a material of variable provenance, which is a general problem.

The compliance position does not transfer. Standards, approval routes, testing requirements and the bodies responsible for them differ between the EU and the GCC, and they differ within the GCC between jurisdictions. A material accepted in one market is not thereby accepted in another, and an approval given by one authority has no standing with another.

That means a specification cannot be lifted from one market and applied in another without establishing the local position. The material questions are the same; the answers are jurisdiction-specific, and they should be confirmed for the project and the market rather than assumed from an analogous project elsewhere. The direction of travel in the region is toward more structured waste and materials regulation — Saudi Arabia's environment ministry, for instance, holds the mandate to regulate and supervise waste management and to encourage investment in the sector [E] — but a mandate of that kind establishes the framework, not the specific requirements a project must satisfy.

One further boundary deserves stating. Nothing here constitutes advice on the suitability of any specific material, and nothing here addresses hazardous materials, for which there are specific regulatory requirements and specialist obligations. Where a source stream may contain hazardous constituents, or where the application raises questions of that kind, the assessment must be made by qualified specialists under the applicable regime, and this article should not be read as offering guidance on it.