Reinforcement is the load-bearing backbone of reinforced concrete. It imparts tensile capacity and ductility to the brittle material concrete, limits cracks, and enables load-bearing, durable structures. In design, construction, repair, and selective deconstruction, reinforcement influences every work step—from execution and control to demolition. Especially in fields such as concrete demolition and special deconstruction, building gutting and cutting, or rock excavation and tunnel construction, the arrangement and density of the reinforcement determine the choice of suitable hydraulic tools, such as concrete pulverizers or hydraulic rock and concrete splitters from Darda GmbH.
Definition: What is meant by reinforcement
Reinforcement means all tensile-resistant materials embedded in concrete—predominantly deformed steels in the form of bars, meshes, or cages—that develop a load-bearing bond with the concrete. Reinforcement carries tension, shear, and punching forces, controls crack widths, and increases deformability. In addition to unalloyed or corrosion-resistant reinforcement steel, non-metallic armatures (e.g., GFRP) are used in special cases. Reinforcement is effective only in reliable bond with adequate concrete cover and code-compliant anchorage.
Composition, materials, and forms of reinforcement
Reinforcement typically consists of deformed bars (e.g., B500) and factory-welded meshes. It is arranged as longitudinal and transverse steel, stirrups, shear and punching reinforcement, rings, cages, and connection elements. Connections are made by lap splices, mechanical couplers, or welding, depending on design and execution. Concrete cover protects against corrosion and ensures bond. In members subject to dynamic loading or with high crack risk, the reinforcement is spaced more closely to limit crack widths. In refurbishment works, post-installed bonded reinforcement bars and overlays with additional reinforcement are used.
Operating principle: Bond between steel and concrete
The structural behavior of reinforced concrete is based on the mechanical bond between deformed reinforcement steel and the surrounding concrete. The ribs transfer shear stresses, while the concrete cover provides corrosion protection and fire protection. The bond enables tensile forces to pass from the concrete to the steel, keeps cracks finely distributed, and securely anchors bar forces.
Crack-width control and ductility
Fine, well-distributed cracks with small widths improve serviceability and durability. Closer bar spacing, sufficient anchorage lengths, and suitable bar diameters support controlled crack formation and preserve the member’s ductility.
Shear and punching reinforcement
Stirrups, inclined bars, or headed studs prevent sliding of concrete compression struts. In slabs, special reinforcement reduces the risk of punching. These components largely govern, during demolition works, the cutting and separating forces that tools such as concrete pulverizers must apply.
Planning, concrete cover, and execution
Design and detailing of reinforcement follow recognized rules of practice. Key factors include concrete cover, lap splice and anchorage lengths, bar spacings, and detailing rules for support zones, openings, and connection regions. Careful execution—e.g., fixing the bars, avoiding displacement during concrete placement, and adequate curing—is essential for durability and load-bearing capacity.
Concrete cover
The required concrete cover is determined, among other things, by exposure conditions. It protects against carbonation, chlorides, and fire. Shortfalls promote corrosion and reduce bond.
Quality assurance
Inspections include checking position, diameter, spacing, lap splice lengths, and concrete cover. Locating devices and radar help record reinforcement layout in existing structures for interventions and deconstruction.
Reinforcement in concrete demolition and special demolition
In selective deconstruction, reinforcement influences the choice of separating or breaking method. Density, bar diameter, and anchorage determine whether components are crushed with concrete pulverizers, opened with hydraulic wedge splitters, or separated using cutting techniques. Hydraulic power packs supply the tools with the necessary drive power. The goals are low-vibration, low-impact methods with controlled crack propagation, low dust generation, and clean separation of concrete and steel.
Tool selection based on degree of reinforcement
- Low reinforcement ratio: Concrete pulverizers crush concrete economically; exposed bars are then cut with steel shears or combination shears.
- High reinforcement ratio or massive nodes: Hydraulic wedge splitters or rock wedge splitters initiate controlled cracks to weaken cross-sections; afterward, the reinforcement is cut with steel shears or Multi Cutters.
- Confined areas during building gutting and cutting: Compact concrete pulverizers with sensitive hydraulics facilitate selective removal without damaging adjacent components.
Safety with prestressed concrete
Special caution is required for prestressed concrete. The uncontrolled release of prestressed elements can be hazardous. Measures are planned project-specifically and executed by qualified personnel using appropriate methods and protective measures.
Exposure, separation, and clean sorting
Efficient deconstruction uses knowledge of reinforcement to plan the sequence: first weaken concrete cross-sections, then cut steel, and separate materials by type. This supports recycling streams and reduces transport volumes.
- Locating reinforcement layers and determining concrete cover.
- Crack initiation with hydraulic wedge splitters along weaker zones to open the concrete.
- Crushing remaining cross-sections with concrete pulverizers to expose bars.
- Cutting the reinforcement with steel shears, combination shears, or Multi Cutters.
- Organized material logistics for concrete debris and reinforcement steel.
Special deployments
In industrial facilities or during the deconstruction of strengthened pedestals and foundations, special tasks can arise, such as cutting thick-walled steel and composite sections. Depending on the specific situation, in addition to concrete pulverizers, other cutting devices such as tank cutters may be considered, provided this is technically and safely indicated.
Reinforcement in rock excavation and tunnel construction
In tunnel construction and shotcrete linings, meshes, lattice girders, and anchors are used as reinforcement. During deconstruction or during breakthroughs through shotcrete tunnel shells, these armatures influence the approach. Hydraulic wedge splitters enable low-vibration opening, while concrete pulverizers remove reinforced shells in a targeted manner. The choice of sequence takes into account rock-mass behavior, support systems, and the position of the reinforcement.
Reinforced shotcrete
Fiber and bar reinforcement act in combination. During intervention, sparks, dust, and rebound should be minimized; extraction and shielding are organized accordingly.
Building gutting and cutting in existing structures
During building gutting in existing buildings, different reinforcement layers coincide with installations and fit-out. Compact, precisely guided concrete pulverizers supported by suitable hydraulic power packs allow selective removal without overstressing adjacent structures. Preparatory core drilling can define cut edges and reveal the reinforcement layout.
Openings and breakthroughs
For new openings in slabs and walls, the reinforcement layout around cutouts must be considered. Separation cuts are placed so that reserve capacity is maintained and load redistribution proceeds in a controlled manner.
Typical reinforcement damage and its significance in deconstruction
Concrete carbonation, chloride contamination, and moisture promote corrosion. Rust leads to expansive stresses, spalling, and loss of bond. In practice, this often means: the concrete can be opened more easily, while the residual load-bearing capacity is more uncertain. Deconstruction concepts take this condition into account to establish safe work sequences and appropriate tool loads.
Repair-adjacent interventions
In partial deconstruction for strengthening, concrete pulverizers are used to remove concrete in a controlled manner and expose the reinforcement without unnecessarily damaging it. Subsequently, post-installed reinforcement can be placed and integrated to achieve a load-transferring connection.
Locating, documentation, and occupational safety
Before interventions, reinforcement layers are located and documented using suitable methods. This prevents unintended cutting of load-bearing steel and increases execution safety. Dust and noise reduction, spark avoidance, shielding, and coordinated hydraulics and energy management are key parts of occupational safety.
Documentation
Traceable documentation of reinforcement layout, interfaces, and separation sequences facilitates team coordination and subsequent disposal. Materials separated by type improve recycling.
Sustainability and resource efficiency
Reinforcement steel is highly recyclable. Methods that separate concrete and steel early reduce disposal effort and increase the recycling rate. Low-vibration methods with concrete pulverizers and hydraulic wedge splitters reduce emissions and protect adjacent structures, which is particularly relevant in inner-city deconstruction and sensitive special deployments.