Overview
ISO/TS 21056:2025 - Recycled aggregate concrete (RAC) provides a practical framework and additional provisions for the specification, performance, production and execution of concrete that uses recycled aggregates. Intended as guidance to complement ISO 22965, this Technical Specification covers RAC for structures cast in situ, precast elements and non-structural concrete, and applies to on‑site mixed, ready‑mixed and plant‑produced precast concrete. ISO/TS 21056 aims to promote the safe, consistent and sustainable use of recycled aggregates recovered from construction and demolition waste.
Key topics and technical requirements
The document addresses the full RAC lifecycle with emphasis on materials, testing and workmanship:
- Constituent materials: requirements and quality inspection criteria for recycled coarse and recycled fine aggregates, plus handling, storage and transport considerations (see ISO 18985).
- Performance parameters: guidance on consistence (workability), mechanical properties (compressive strength, elastic modulus), deformation (drying shrinkage, creep), and durability metrics such as carbonation resistance, permeability, chloride resistance and thermal parameters.
- Durability concerns: assessment of alkali–silica reactivity and other long‑term aspects specific to recycled aggregates.
- Mix proportioning: methods for determining target compressive strength, total water content (net vs additional water for saturated surface‑dry condition), cementitious content, and coarse/fine aggregate proportions.
- Production & execution: production controls, mixing procedures, delivery and transport of ready‑mixed RAC, pumping, casting and curing practices tailored for recycled aggregates.
- Testing & compliance: references to relevant test methods (ISO 1920 series, ISO 12439, ISO 19595/96, ISO 22904, ISO 22965 parts 1–2) for sampling, fresh and hardened concrete assessment.
Practical applications and users
ISO/TS 21056 is aimed at professionals implementing RAC in construction projects:
- Specifiers and design engineers - for performance‑based specification and mix design guidance.
- Concrete producers and precast manufacturers - to adapt production processes and quality control when using recycled aggregates.
- Contractors and site teams - for execution practices such as pumping, casting and curing of RAC.
- Testing laboratories and compliance bodies - for verifying RAC performance and conformity with test methods.
- Sustainability and waste‑management planners - to support circular economy goals by reducing landfill and natural aggregate consumption.
Related standards
Keywords: ISO/TS 21056:2025, recycled aggregate concrete, RAC, recycled aggregates, mix proportion, durability, specification, production, execution, sustainable concrete.
Open preview (PDF)Recycled aggregate concrete — Additional provisions and guidance for specification, performance, production and execution
