In construction, a composite system is understood as a structure or component in which different materials are connected in such a way that they jointly take loads and achieve specific properties. In planning, execution, and especially in deconstruction, this composite has a direct impact on the choice of method: selective separation, the controlled release of adhesive bonds, and the safe separation of components determine tactics, tools, and sequence. Particularly when working with concrete pulverizers, hydraulic rock and concrete splitters, as well as supplementary cutting and shearing tools from Darda GmbH, understanding the composite is crucial—for example, to separate steel and concrete cleanly, achieve controlled crack propagation, and improve recycling fractions.
Definition: What is meant by composite system
A composite system is the purposeful coupling of two or more materials with different properties (e.g., concrete and steel, masonry and insulation, rock and shotcrete) to achieve composite action. This coupling can occur through adhesion, mechanical interlock (e.g., ribs, shear connectors, profiles), or frictional contact. Typical examples include reinforced concrete components, steel–concrete composite beams, composite slabs, bracing with fibre composite material laminates, as well as external thermal insulation composite systems on façades. In deconstruction, composite action leads to specific requirements for the separation cut, splitting technique, and sequence, because the materials must first be released from each other before they can be separated by type and removed.
Typical composite systems in construction and deconstruction
Composite systems occur in many parts of a structure. For the planning of demolition, strip-out, and special deconstruction, it is helpful to know the common types and their separation logic:
- Reinforced concrete and prestressed concrete: Concrete with embedded reinforcement; the high compressive strength of the concrete and the tensile capacity of the steel act together. In deconstruction, concrete pulverizers are often used to remove the concrete, and steel shears to cut the reinforcement separately.
- Steel–concrete composite constructions: Composite beams, composite slabs with shear connectors; particular attention is paid to shear joints and headed studs.
- External thermal insulation composite systems: Multilayer façade assemblies of insulation, plaster, and fastening elements; separation proceeds layer by layer, often with mechanical removal and controlled segmentation.
- Masonry with bonded anchors: Coupled wythes or retrofitted anchored components; anchors and the mortar bond must be deliberately exposed and separated.
- Fibre-reinforced composite strengthening: CFRP/GFRP laminates or fabrics on concrete; the pull-off bond strength of the adhesive layer determines the separation strategy.
- Shotcrete, lattice girders, and anchors in tunneling: Composite of rock mass, shotcrete, reinforcement, and anchors; removal in defined panels with controlled crack guidance.
- Composite pipes and tanks: Multilayer assemblies of metal and coatings; thermal or mechanical separation with consideration of media and safety zones.
Challenges in separating composite systems
Composite systems store forces via adhesive bond and mechanical interlock. In deconstruction these bonds must be released in such a way that uncontrolled load redistribution, spalling, and unintended crack formation are avoided. Different material properties (compressive/tensile strength, toughness, density), layer thicknesses, and installation positions require coordinated steps. Concrete pulverizers enable selective breakout of concrete to expose reinforcement. Rock wedge splitters and concrete splitters generate defined crack lines along the desired separation plane, for example at wall openings or foundation heads. Combination shears, Multi Cutters, and steel shears complement the separation chain for metal components. Hydraulic power units supply the tools with the necessary power, and pressure and oil-flow control increase process safety.
Method selection: mechanical, hydraulic, thermal
The choice of method is oriented to the composite type, boundary conditions (vibrations, noise control, dust), and the objective (segment size, recycling quality). In sensitive environments, low-vibration and low-emission methods have advantages.
- Hydraulic splitting: Rock wedge splitters and concrete splitters transfer the separating energy into the component and generate controlled cracks. Suitable for thick cross-sections, massive foundations, and natural stone.
- Hydraulic crushing: Concrete pulverizers break out concrete with low fines and open cracks while exposing reinforcement; comparable concrete crushers for low fines can achieve similar results; downstream steel shears cut the rebar.
- Cutting and shearing: Multi Cutters, combination shears, and steel shears process sheet metal, profiles, pipelines, and reinforcement—usually after exposure with concrete pulverizers.
- Thermal methods: For tanks and vessels, tank cutters are used where conditions (media, explosion protection) allow; separation is carried out in a structured way with appropriate protective measures.
Applications in the fields of use
Concrete demolition and special deconstruction
In reinforced concrete, reinforcement density, concrete cover, and composite joints are decisive. A common sequence: pre-separation with rock wedge splitters and concrete splitters, removal with concrete pulverizers in partial areas, exposing the reinforcement, and subsequently cutting it with steel shears. In composite beams, shear connections are deliberately released to separate steel and concrete in a controlled manner.
Strip-out and cutting
In multilayer assemblies (e.g., interior fit-out, façades with composite systems) removal proceeds layer by layer. Concrete pulverizers are used to open load-bearing layers; Multi Cutters and combination shears process fixtures, lines, and metals. The sequence minimizes spring-back and prevents residual composites from cracking uncontrollably.
Rock excavation and tunneling
The composite of rock mass, shotcrete, meshes, and anchors requires a controlled approach. Rock splitting cylinders set defined cracks in the rock; concrete pulverizers remove shotcrete panels section by section. Where anchors hold the composite, they are deliberately cut after exposure before the next panel is processed.
Natural stone extraction
Natural joints and bedding form the composite in the rock. Rock splitting cylinders exploit these weak zones for dimensionally accurate blocks. When releasing backside bonds or consolidations, pull-off bond strength must be checked to adjust the split line and force demand.
Special operations
In areas with sensitive media or strict emission control, low-noise and low-vibration methods are preferred. Tank cutters structure cutting sequences on vessels, while Multi Cutters and steel shears separate fixtures and beams. Hydraulic power packs with fine pressure control support safe work in the composite.
Planning and structural analysis: understanding composite action
Composite constructions transfer forces via shear and adhesion. In deconstruction these paths must be identified in advance to avoid unintended redistributions. Load release, temporary shoring, and step-by-step separation are part of a structure-appropriate strategy. Statements regarding load-bearing capacity and the regulatory framework are always to be understood as general; the specific assessment lies with those responsible in planning and execution.
Material separation and recycling
Single-grade separation increases recovery rates. Concrete pulverizers generate aggregate with low oversize and facilitate the separation of reinforcement, which is then cut into transportable lengths with steel shears. For façade composite systems, layer-by-layer dismantling is recommended to avoid mixing. Early exposure of the composite reduces rework, dust, and costs in processing.
Practical procedure in composite systems
- Existing-condition analysis: drawings, site visits, material samples; identification of composite joints, reinforcement zones, anchors.
- Risk assessment: residual stresses, media, emissions; definition of protective and safety measures.
- Pre-separation: placing splitting wedges or splitting cylinders to initiate cracks along defined lines.
- Selective removal: concrete pulverizers for concrete, steel shears/Multi Cutters for metals; step-by-step release of composite interfaces.
- Segmentation: cutting to lifting and transport sizes; use of combination shears on mixed profiles.
- Separation and logistics: collect by type, intermediate storage, haulage to recovery.
- Inspection: visual check of separation surfaces, rework residual composites if necessary; documentation.
Technical parameters and selection criteria
Key parameters for method selection include the pull-off bond strength of composite layers, shear capacity at connectors, component thicknesses, degree of reinforcement, material toughness, and accessibility. Environmental requirements (noise, vibrations, dust) influence the decision between splitting, crushing, cutting, and thermal methods. Concrete pulverizers and rock wedge splitters/concrete splitters show their strengths when controlled crack formation, low side effects, and clean separation surfaces are required. Hydraulic power packs are sized so that pressure, flow rate, and cycle time match the component and the desired segment size.
Quality assurance and documentation
Complete documentation supports verification and recycling. Practical measures include photo documentation of separation joints, logs of cutting and splitting sequences, and mass balances of the fractions. For critical composites, simple checks (e.g., tapping, trial slot, local pull-off tests) can help verify assumptions and adjust the sequence.
Terminology: composite, adhesion, and shear connection
Composite describes the interaction of the materials. Adhesion refers to bonding between layers, while shear connection denotes force transfer transverse to the member axis (e.g., via connectors). For deconstruction it is crucial whether the composite acts predominantly through adhesion, mechanical interlock, or friction—this determines the approaches for splitting, crushing, and cutting.