Reinforcing Steel in Concrete Demolition Guide

Reinforcing steel – often also called reinforcement steel or rebar – is the load-bearing counterpart to concrete in the composite material reinforced concrete. While concrete resists compressive forces very well, reinforcing steel transfers tensile, bending and shear forces. In planning, construction and deconstruction, the material determines the choice of working methods and equipment. In selective concrete demolition, in special demolition or during interior strip-out, reinforcing steel influences, for example, whether pieces are first split and then separated, or whether work proceeds directly with concrete pulverizers, steel shears or Multi Cutters. rock and concrete splitters as well as hydraulic power units from Darda GmbH are also established in this interplay, because they operate with low vibration and can expose the steel in a targeted manner.

Definition: What is meant by reinforcing steel

Reinforcing steel is a hot- or cold-worked steel that is placed in bars, rings or mats into fresh concrete. Ribbing or profiling creates a mechanical interlock with the concrete; in addition, bond is provided by the rough surface. This forms the composite material reinforced concrete, which purposefully combines different material properties. Common designations are reinforcement bars (round steel), reinforcing steel mats and stirrups/shear reinforcement. Characteristic parameters are yield strength, tensile strength, proof stress, ductility and weldability. In deconstruction and demolition, it is essential that the steel can still exhibit high residual tensile capacity even after decades – this affects the safe sequence of separating, gripping and splitting.

Material properties and standard classes

Modern reinforcement steels are divided into strength and ductility classes (for example B500 with different ductility classes). Ribbing, carbon equivalent and microstructure influence bendability, weldability and fracture behavior. Important for deconstruction work:

Ductility: Ductile behavior reduces brittle fractures during cutting and lowers the risk of uncontrolled snap-back.
Ribbing and bond: More heavily ribbed steels adhere better in concrete – this makes pulling out more difficult but favors exposure by controlled crushing with concrete pulverizers.
Corrosion state: Corrosion can reduce cross-sections but also induce stresses. Severely corroded bars can sometimes be easier to cut, yet pose breakage risks at unpredictable locations.

The required concrete cover protects the steel in service. During deconstruction, the actual cover (measured or probed) determines a sensible scoring and splitting line as well as the choice of gripping and cutting points.

Roles in structures and reinforcement types

Reinforcing steel acts where concrete reaches its limits:

Longitudinal reinforcement: Takes up tension and bending moments in beams, slabs and columns.
Shear and torsion reinforcement: Stirrups and rings limit shear crack formation.
Crack width control: Fine distributed reinforcement in slabs and walls controls cracks.
Mats and meshes: Area reinforcement in slabs and ground-bearing slabs.

For the practice of demolition and special deconstruction this means: In slabs, mesh reinforcement with frequent laps dominates; in columns, large diameters with tight stirrups are common. This leads to different strategies – for example, pre-splitting concrete surfaces with stone and concrete splitters and then cutting exposed bars with steel shears or Multi Cutters.

Reinforcing steel in deconstruction: Cutting, gripping, splitting

In selective deconstruction, the controlled interplay of multiple methods is decisive. A proven combination is local weakening of the concrete, controlled crushing and subsequent steel cutting:

Concrete pulverizers: Crush reinforced concrete and expose reinforcing steel. Due to high crushing and cutting action, concrete is removed while the steel is bridged and worked out in a targeted manner.
Stone and concrete splitters (including stone splitting cylinders): Create controlled crack patterns in concrete with very low vibration and low noise. The steel acts as crack limitation; exposed bars are then cut or pulled out.
Steel shears and Multi Cutters: Cut exposed reinforcement bars, stirrups and meshes. The choice depends on diameter, bundling and accessibility.
Combination shears: For components with alternating concrete and steel, when frequent switching between gripping, crushing and cutting is required.
Hydraulic power packs: Reliably supply pulverizers, shears and splitters with the required power, especially in confined or sensitive areas where emissions and vibration must be minimized.

Tactics for low-emission special demolition

In noise-sensitive zones or where low-vibration work is required, the concrete is first segmented into manageable pieces using stone and concrete splitters. Then concrete pulverizers are used to peel off residual concrete and expose the reinforcement. Final cutting of the bars is performed with steel shears or Multi Cutters. This sequence reduces sparking, dust and uncontrolled movement of the steel.

Determining the reinforcement before intervention

A robust assessment of the reinforcement reduces risks and saves time:

Exploratory openings and local openings along planned cut lines.
Check reinforcement drawings, if available; otherwise, use low-destructive detection (e.g., locating bar positions).
Consider element-typical patterns: slabs with orthogonal meshes, walls with longitudinal and transverse reinforcement on both faces, columns with large longitudinal bars and tight stirrups, beams with high shear reinforcement.

Impact on equipment selection

Dense stirrup reinforcement in node regions favors a step-by-step approach: first splitting, then pulverizer work, finally steel cutting. For large bar diameters and bundles, steel shears with high cutting force or robust Multi Cutters are appropriate; in lightly reinforced slabs, concrete pulverizers speed up the exposure of the meshes.

Safety and occupational safety (general, not legally binding)

Reinforcing steel can relax suddenly when cut. Principles for safe work:

Never cut steel under tension; unload the element and assess relaxation paths.
Secure gripping and cutting areas; account for kickback and whipping.
Reduce dust, noise and fragments (covers, water mist, coordinated cutting sequence).
Depressurize hydraulic connections and secure before changing tools.
Use grounded work areas near potential ignition sources; avoid sparking where possible, prefer shearing over abrasive cutting methods.

Material separation, logistics and recycling

After breaking down the reinforced concrete elements, steel and concrete must be cleanly separated. Consistent exposure with concrete pulverizers and subsequent cutting with steel shears or Multi Cutters enables pure fractions:

Concrete: Process by crushing and screening; usable as recycled concrete material.
Steel: Collect by grade and feed into the scrap cycle; clean cut edges facilitate marketing.

Clear separation logistics reduce disposal costs and lower the carbon footprint. The fewer concrete residues remain on the steel, the more efficient the recycling.

Specifics in application areas

Concrete demolition and special deconstruction

Massive components with high reinforcement density benefit from a sequential approach: crack induction using stone and concrete splitters, exposure with concrete pulverizers, steel cutting with steel shears. Combination shears are helpful when frequent switching between gripping and cutting is necessary.

Strip-out and cutting

In interior spaces, low emissions and compact tools are crucial. Targeted creation of slab openings or wall chases is achieved by careful splitting and subsequent peeling with concrete pulverizers. Mesh and stirrup steel are then cut with Multi Cutters or steel shears. Where steel structures or vessels connect to reinforced concrete, tank cutters are additionally used; the reinforcement in the adjacent concrete is exposed in parallel and cut separately.

Rock demolition and tunneling

In tunneling, shotcrete with mesh or anchor reinforcement is encountered. Stone and concrete splitters allow controlled cracking in the lining concrete with low vibration; anchor heads and reinforcement can then be cut with steel shears or Multi Cutters. Confined workspaces favor compact, hydraulically driven hand tools with an external hydraulic power pack from Darda GmbH.

Natural stone extraction

In natural stone quarries, splitting rock is the focus. Reinforcing steel is encountered at foundations, pedestals or with subsequent concrete additions (e.g., machine foundations). After exposure using stone and concrete splitters, the existing bars are cut with steel shears.

Special operations

Special tasks such as deconstruction of reinforced security areas or remediation after damage events require flexible concepts. Combination shears and concrete pulverizers for exposure, supplemented by Multi Cutters and steel shears for steel cutting, enable versatile approaches. Where thick-walled steel tanks or pipelines are present near reinforced concrete, these can be processed with tank cutters while the reinforcement of the concrete elements is cut separately.

Technical details: diameter, bundling and cutting strategy

The choice of cutting tool is primarily based on bar diameter, accessibility and stress state.

Single layers up to medium diameters: Expose with concrete pulverizers, cut with Multi Cutters or light steel shears.
Large diameters/bundles: Prefer splitting and pulverizer work to relieve stresses, then use more robust steel shears.
Dense stirrup reinforcement: Peel off in sections, cut stirrups one after another to avoid jamming.

Sequence and force introduction

A favorable approach is to cut from points with the least residual tension. Where possible, relieve the bar with two cuts before removing the middle piece. When working with stone and concrete splitters, a splitting line transverse to the main reinforcement helps expose the steel without overstretching it uncontrollably.

Corrosion, coating and bond issues

Passivated steel in concrete is protected by alkalinity. Chloride contamination and carbonation can weaken the bond. For deconstruction this means:

Corroded areas provide starting points for rapid exposure with concrete pulverizers.
Local cross-section reductions increase the risk of sudden fractures – plan the cutting sequence carefully.
Coated or galvanized steels behave similarly during cutting but require attention to fumes and particles; shearing methods are advantageous.

Planning, documentation and quality

Clean documentation of reinforcement layers, cutting points and the sequence of work steps increases execution safety and traceability. Photographic interim states, markings of main bars and clear allocation of cut steel fractions simplify removal and recycling. Hydraulic tools from Darda GmbH have proven to be reliable components here, as they enable reproducible, controlled interventions.

Typical error patterns and how to avoid them

Cutting under tension: Unload the element first, then cut.
Cutting stirrups too early: Expose main bars first to prevent jamming and uncontrolled shifts.
Insufficient exposure: Remove enough concrete with concrete pulverizers so the shears can seat cleanly.
Material mixing: Consistent separation into pure fractions improves disposal and recycling.

Alternatives and additions

Diamond drilling and sawing cut reinforced components very precisely, but generate slurry and require extensive equipment. In many projects they are a sensible addition to the low-vibration strategy of stone and concrete splitters, concrete pulverizers and steel shears. Where, alongside reinforced concrete, thick-walled steel parts are present (e.g., tanks or pipelines), tank cutters can be used in parallel; the concrete reinforcement remains unaffected and is cut separately with shears.

Practical guide: from element to cut

A proven workflow for processing reinforcing steel in reinforced concrete is:

Inspect the element, probe reinforcement layers, secure load paths.
Depending on the environment, split (stone and concrete splitters) or crush (concrete pulverizers) the concrete to expose the steel.
Position reinforcing steel with minimal stress, apply pre-cuts if necessary.
Cut bars, meshes and stirrups with steel shears or Multi Cutters.
Separate fractions and document; depressurize hydraulic power packs and check tools.