Recycled construction material is a central pillar of the circular economy in construction. It is produced from processed mineral residuals and replaces primary raw materials such as natural stone aggregates. In concrete demolition, special demolition, and rock excavation, precise dismantling and gentle crushing significantly contribute to the quality of the recycling fractions. Tools such as concrete pulverizers and stone and concrete splitters enable clean separation by material type while also protecting adjacent components—a benefit for the subsequent use of the recovered materials as recycled construction material.
Definition: What is meant by recycled construction material
Recycled construction material refers to mineral construction materials that originate from secondary sources and functionally replace primary construction materials. This includes recycled materials from concrete and masonry debris (e.g., recycled aggregates for base course or concrete), asphalt granulate, processed soils and rocks, as well as industrial by-products suitable for construction purposes. Recycled construction material is obtained and processed in quality-assured procedures and examined for environmental compatibility and technical properties. It is used in road and transport infrastructure construction, civil engineering (underground works), earthworks and utility line installation, in concrete construction with recycled concrete content, and in temporary working layers. Legal and normative requirements may vary depending on material, region, and application scenario and should generally be considered at an early stage.
Material types and properties of recycled construction material
Recycled construction material differs by origin, processing, and target application. Typical groups and their characteristics:
- Recycled materials from concrete and masonry demolition: predominantly mineral aggregates; suitable for base course, frost protection layers and—given adequate quality—as aggregate in concrete.
- Asphalt granulate: reusable in asphalt mixes or as an unbound layer; decisive factors are binder content and grading.
- Processed soils and by-products from crushed natural stone: usable as backfill material, subgrade protection layer, or for backfilling.
- Industrial by-products with construction potential: usable for defined applications depending on origin; suitability tests and environmental assessments are key.
Key properties include particle size distribution, bulk density, water absorption, resistance to frost and de-icing salts, resistance to abrasion and crushing, purity (foreign matter content), and leachate-related parameters. A high initial quality from deconstruction facilitates meeting technical and environmental requirements.
Applications in concrete demolition and special demolition
In deconstruction projects, the choice of method determines the quantity, purity, and grading of the resulting fractions. Concrete pulverizers are suitable for targeted breaking of concrete while simultaneously exposing reinforcement. Stone and concrete splitters allow low-vibration partial deconstruction in sensitive areas. This yields defined blocks and fewer fines—favorable for downstream processing into recycled construction material.
Selective deconstruction and separation by material type
Selective dismantling, separate collection of concrete, masonry, asphalt, and metal, as well as early removal of adherences and contaminants, establish the basis for high-quality recycled aggregates. In areas with dense existing stock, neighboring buildings, or vibration-sensitive installations, splitting methods and precise shear work are advisable to preserve the structure and keep material streams cleanly separated.
Separating reinforcement and pre-crushing
Targeted rebar cutting reduces metal content in the mineral fraction and increases processing quality. In addition to concrete pulverizers, combination shears, steel shears, and multi cutters can be used for cutting steel and sections. With appropriate pre-crushing, size bands are generated that make crushing and screening processes more efficient and increase the share of usable recycled construction material.
Processing: From deconstruction to quality-assured recycled construction material
The production of recycled construction material follows a structured process:
- Pre-separation of foreign materials (metals, wood, plastics), removal of adherences and contaminants.
- Crushing in coordinated stages to achieve targeted particle shape and size distribution.
- Screening and classifying into defined size ranges according to the intended use.
- Metal separation, air classification, and, if necessary, wet cleaning to further enhance quality.
- Intermediate storage by material type, quality, and moisture balance with clear identification.
Contaminant testing and quality assurance
Before placement, depending on the application, material- and environment-related testing is customary. This includes random spot checks, leachate-based assessments, and documentation of origin and processing steps. Such testing is generally carried out according to the respective applicable regional regulations. The information provided here is general and does not replace a case-by-case assessment.
Technical parameters and suitability criteria
Suitability as recycled construction material depends on the intended use. In road and civil engineering, load-bearing capacity, compactibility, and frost resistance are paramount; in concrete construction, particle shape, strength, density, water absorption, and potential alkali-silica reactivity are key. In practice, the following are particularly relevant:
- Particle size distribution and shape for compaction and mortar accessibility in concrete.
- Purity and a low share of soft constituents or contaminants.
- Resistance to frost/de-icing salts, abrasion, and crushing.
- Consistent quality through documented processing and stock management.
Ecological and economic aspects
Recycled construction material saves primary raw materials, reduces the need for landfill capacity, and can lower emissions. Short transport routes, appropriate logistics, and reliable quality assurance are crucial for ecological and economic benefits. Early planning of deconstruction, sorting, and processing increases the yield of high-quality fractions and shortens project timelines.
Recycled construction material in rock excavation and tunnel construction
Rock excavation and tunnel construction generate substantial volumes of rock. Through targeted fragmentation—such as by using stone and concrete splitters or rock wedge splitters—the material can be released so that it can be processed for embankment layers, dam construction, or as frost-insensitive layers. Low-vibration splitting methods are advantageous in sensitive environments and support orderly material logistics from excavation through to reuse as recycled construction material.
Planning, tendering, and execution
To ensure reliable use of recycled construction material, a coordinated approach is recommended:
- Deconstruction concept focusing on selective dismantling and source-separated collection.
- Material register with forecasts of quantities, qualities, and potential use pathways.
- Specifications with application-related quality and testing requirements.
- Construction-phase quality assurance, documentation, and approvals in accordance with applicable regulations.
- Installation control, compaction, and verification according to the intended use.
Storage, transport, and installation
Separate storage in paved, clean areas reduces mixing. Moisture and fines must be controlled to ensure uniform installation conditions. For transport: suitable loading and unloading equipment, covering of sensitive fractions, and clear labeling. Installation is carried out in layers, with appropriate compaction and spot checks of layer thicknesses and densities.
Limits and risks
Not every demolition material is automatically a suitable recycled construction material. Critical issues include, for example, hazardous substance content, unsuitable grading, reactive aggregates, or material-related swelling and shrinkage. Certain industrial by-products may be subject to special requirements regarding aging, storage, and leachate behavior. Careful planning and testing reduce risks and ensure compliant use in line with applicable rules and standards.
Practical relevance to products and application areas of Darda GmbH
In practice, it becomes clear: the more precise the deconstruction, the higher the quality of the resulting recycled construction material. Concrete pulverizers support targeted loosening of concrete and exposing reinforcement in concrete demolition and special demolition. Stone and concrete splitters are used when vibrations must be minimized, for example during building gutting and cutting in existing structures, in rock excavation, or for special operations. By combining these methods with downstream processing, fractions are produced that qualify as load-bearing, environmentally compatible recycled construction material for a wide range of applications.