Incinerator Bottom Ash Aggregate (IBAA):
A Proven Sustainable Aggregate for UK Construction
Why Do Sustainable Aggregates Matter?
The UK construction industry is under pressure to reduce carbon emissions, preserve natural resources, and adopt more sustainable aggregates. Traditional quarrying for primary aggregates is resource-intensive, but recycled construction materials like Incinerator Bottom Ash Aggregate (IBAA) provide a practical solution.
Produced from the residue of Energy-from-Waste (EfW) plants, IBAA is now widely accepted across the UK as a low-carbon construction material. This article explains how IBAA is made, its uses as a Type 1 sub-base and 6F4/6F5 capping layer, and the benefits it offers as part of the shift towards circular economy aggregates. Where helpful, we reference Ecoblend®, Day Aggregates’ family of blended, spec-compliant products, so specifiers can see exactly how IBAA is delivered to site in practice.
From EfW to Construction: How IBA Becomes IBAA
When household or commercial waste is burned in EfW facilities, a mineral residue remains, known as Incinerator Bottom Ash (IBA). This ash contains glass, ceramics, metals, clinker, and stone.
At specialist recycling facilities such as those operated by Day Aggregates in Avonmouth, Brentford, Greenwich, and Wellingborough, IBA is transformed into IBAA – a high-quality secondary aggregate that Ecoblend uses within its Type 1 and 6F4/6F5 blends.
The production process includes:
- Aging – IBA is stockpiled outdoors to stabilise chemically and reduce lime reactivity
- Metal Recovery – Magnets and eddy current separators remove ferrous and non-ferrous metals for recycling
- Crushing and Screening – The mineral fraction is processed into graded, construction-ready aggregate
- Blending and Refinement – IBAA may be combined with other aggregates to meet strict performance standards. Ecoblend uses controlled formulations (e.g., Ecoblend MA and Ecoblend CA) to deliver consistent, spec-compliant materials.
The result is a granular, stable material that resembles quarried materials, ideal for use as IBAA sub-base and capping layers in road and infrastructure projects. Ecoblend formulations are produced under factory production control to ensure uniformity, traceability, and reliable on-site performance.
Is IBAA Safe?
IBAA is routinely classified as non-hazardous, provided it is processed according to industry standards.
- Only IBA classified as non-hazardous (waste code 19 01 12) is accepted for recycling
- Processing removes contaminants and stabilises the ash
- Testing (pH, leachability, heavy metals) confirms safety for construction use
While regulators still technically define IBAA as “waste” until formal End-of-Waste criteria are finalised, it is widely recognised as a safe, durable recycled construction material suitable for approved applications. Ecoblend supplies are accompanied by compliance documentation and guidance on appropriate locations and uses, so designers and site teams can specify with confidence
Where to use IBAA in Construction
IBAA is one of the most versatile secondary aggregates in the UK. Common applications include:
- Type 1 Sub-Base (SHW Clause 803) – Used under roads, highways, car parks, non-residential foundations. Ecoblend Type 1 incorporates IBAA to deliver consistent grading, compaction and bearing performance
- Capping Layers (SHW Clause 613) – As a 6F4 or 6F5 capping material to build up ground or stabilise weak soils; Ecoblend 6F4 and 6F5 is engineered for dependable platform construction
- General Fill and Platforms – For embankments, industrial yards, and hard standings. Ecoblend’s controlled blends help achieve predictable compaction across larger footprints
- Specialised Bound Uses – In hydraulically bound mixtures or asphalt base courses (niche but proven in trials)
Important: IBAA should not be left exposed; it must be covered with asphalt, concrete, or block paving to comply with Environment Agency RPS 247 guidance. Ecoblend’s technical team can advise on build-ups, over-build requirements and finishing options
Environmental Gains You Can Measure
IBAA is at the heart of the UK sustainable aggregates movement. Its benefits include:
- Landfill Diversion – Every tonne of IBAA represents ~530 kg of waste saved from landfill
- Preserving Natural Resources – Each tonne of IBAA used saves 1.1–1.3 tonnes of quarried stone
- Lower Carbon Footprint – With local EfW plants near cities, IBAA often travels shorter distances than primary aggregates, with fewer lorry movements required reducing haulage emissions
- Circular Economy – IBAA transforms a by-product into a valuable aggregate, directly supporting recycled construction materials UK strategies
Choosing Ecoblend helps clients evidence these outcomes, as supply data, origin, and tonnages can be collated for sustainability reporting and project audits.
Helping You Hit Carbon and Procurement Targets
Using IBAA can help construction projects hit carbon reduction targets and score higher in schemes like BREEAM.
- Replacing high-embodied-energy quarry stone with IBAA lowers overall project carbon
- IBAA is lighter by volume, so fewer truckloads are required
- Public authorities often mandate a percentage of recycled aggregates – IBAA helps meet those targets
For contractors seeking low-carbon construction materials, IBAA is a proven, measurable solution.
Performance, Durability and In-Situ Behaviour
In unbound layers, IBAA performs as well as, and sometimes better than primary quarried stone.
- Strength – Compacts to meet SHW Type 1 and capping specifications; Ecoblend Type 1 is designed for high and consistent CBR
- Durability – Glass, ceramics, and stone are inert and resilient
- Frost Resistance – Properly compacted IBAA resists frost heave
- Pozzolanic Properties – IBAA can mildly self-cement, increasing stability over time
With over 20 years of use in highways and infrastructure, IBAA is proven as a durable, long-term recycled aggregate. Ecoblend’s production control and testing regimes underpin dependable field performance.
Standards, Specifications, Compliance, and Acceptance
IBAA is explicitly recognised under UK and European standards and related specifications, including:
- BS EN 13242 – Aggregates for unbound and hydraulically bound layers
- BS EN 13285 – Mixtures such as Type 1 sub-base
- SHW Clause 803 – Type 1 unbound sub-base specification
- SHW Clause 613 – Requirements for 6F4 and 6F5 capping
Ecoblend products are produced to meet these standards and specification and provides supporting documentation. This helps engineers, contractors, and local highway authorities sign off materials with confidence and ensures smoother compliance checks on site.
Material Efficiency and Cost Benefits
IBAA’s lower density means you need 10–15% less tonnage compared with primary aggregates to achieve the same coverage.
Other cost advantages often include:
- Lower per-tonne prices than natural aggregates
- Exemption from the Aggregates Levy
- Reduced transport costs from local sourcing
Combined, these make IBAA one of the most cost-effective sustainable aggregates in the UK. Ecoblend’s Material Calculator can help you estimate volumes, lorry movements, and potential savings with greater accuracy. Try it here, and find out how much you could save.
Practical Handling and Installation Guidance
On site, IBAA is used much like primary aggregates however for successful handling and installation it should be:
- Delivered slightly damp for easier compaction
- Spread in 150–250mm layers and compacted with standard plant
- Apply dust suppression (recommended in dry weather)
- Always covered with asphalt, concrete, or paving
For Ecoblend products you can access method guidance and typical compaction parameters, helping site teams meet density and CBR targets consistently across platforms, access roads, and hard standings.
Regulation and RPS 247
In England, Environment Agency RPS 247 sets out how IBAA can be used without a waste permit.
Key points:
- Must be non-hazardous and fully processed
- Permitted uses include road sub-bases, capping, and structural fill
- Must not be used in sensitive areas like floodplains or groundwater zones
For most standard applications, no special permit is needed if RPS 247 conditions are followed. Specifically, for Ecoblend, advice on RPS 247 and appropriate usage scenarios is given.
Industry Acceptance and Track Record
IBAA is now mainstream in the UK:
- Over 3 million tonnes used annually
- Widely specified by National Highways and local authorities
- Proven on major projects including the London Olympic Park and numerous highway schemes
Ecoblend aggregates are used across housebuilding, logistics platforms, highway works and public-realm projects, with case studies available to illustrate performance and programme benefits.
MIBAAA and Industry Governance
The Manufacturers of IBA Aggregates Association (MIBAAA) oversees quality and best practice.
- Publishes codes of practice
- Works with regulators on End-of-Waste criteria
- Ensures member companies deliver safe, consistent, compliant aggregates
Sourcing IBAA from MIBAAA members provides extra assurance of quality. Ecoblend is produced within this governance landscape, aligning with recognised standards and contributing to the responsible growth of recycled aggregates in UK construction.
To learn more about MIBAAA and the role they play in the construction industry, visit their website.
Conclusion: IBAA as a Sustainable Aggregate for the Future
As the UK moves towards low-carbon construction materials and circular economy practices, IBAA stands out as a proven solution.
- Meets recognised specifications
- Cuts carbon and landfill
- Delivers material efficiencies and savings
- Widely accepted and trusted
Through high-quality products like Ecoblend, IBAA is already helping contractors across the UK build stronger foundations – both for projects and for a more sustainable future.