Deformation describes the change in shape and length of materials under load. In concrete demolition, rock excavation, interior demolition, and when separating steel and sheet-metal components, deformation behavior determines whether components crack, cut, split as planned, or break unexpectedly. Those who understand the interaction of material, load type, and tool can use deformation deliberately: concrete structures can be opened in a controlled manner, rock blocks split along existing planes of weakness, and steel sections cut cleanly. Products such as concrete pulverizers, hydraulic rock and concrete splitters, hydraulic power units, steel shears, or tank cutters intervene in the deformation mechanisms in different ways—always with the goal of working the existing structure with minimal secondary breakage and precise force application.
Definition: What is meant by deformation
Deformation is the reversible or irreversible change in the geometry of a body as a result of external actions. A distinction is made between elastic deformation (fully reversible after unloading) and plastic deformation (permanent change in shape). If the demand exceeds load-bearing capacity, fracture occurs, often initiated by crack formation. Concrete exhibits brittle behavior under tension and shear; under compression it shows combined crushing and shear yielding with wedge cracks. Steel behaves ductilely: after reaching the yield strength, the material continues to flow plastically. Rock and natural stone usually deform in a brittle manner, depending on joints, stratification, and water content. Time-dependent effects such as creep and shrinkage (concrete) as well as temperature- and rate-dependent effects additionally influence deformation behavior.
Deformation mechanisms in concrete, steel, and rock
The governing mechanisms are compressive, tensile, and shear deformation, often superimposed by bending and torsion. In concrete, microcracks under tension quickly evolve into macrocracks; under compression, shear-tension cracks and crushing zones form. Reinforcing steel takes tensile forces and enables ductile load-bearing but can locally buckle or yield. Rock shows preferred fracture planes along joints; compression dominates in the core, while edge zones go into tension and open up. In steel structures, yield strength and toughness indicate how far plastic deformation is possible before separation (shear or tensile fracture) occurs. Tools target these mechanisms: concrete pulverizers combine compression and shear; stone and concrete splitters induce controlled tension transverse to the borehole axis; steel shears separate by concentrated shear stresses; tank cutters must account for locally confined heat- and deformation zones with springback.
Load types and their influence on the demolition process
The type of loading determines which deformation dominates and how a component responds.
Compressive deformation
Compression is the dominant load in concrete. Local crushing zones and shear wedges govern the fracture pattern with concrete pulverizers. A stable compression chain reduces secondary breakage, for example through aligned bearing surfaces and coordinated stroke movements. In rock, compression in combination with existing weaknesses leads to split-like openings.
Tensile deformation
Tension causes early cracking in concrete. Stone and concrete splitters exploit this by inducing transverse tension in the borehole field with wedges to create a defined crack plane. In steel, tension leads to reaching the yield point; with thin sheet, springback is to be expected.
Shear deformation
Shear is the principle of steel shears and concrete pulverizers when severing overlays and reinforcing bars. In concrete, combined shear and tensile cracks form; crack propagation is influenced by the geometry of the blades and the support of the component.
Bending and torsion
Bending superimposes tension and compression. In cantilevers during deconstruction it leads to crack openings on the tension side. Torsion is relevant for hollow sections and tanks: unplanned twisting can cause buckling and local instability if cuts are placed asymmetrically.
Deformation of concrete: understanding and using crack formation
Crack formation can be controlled when material, geometry, and load path are known. The goal is directed crack propagation with minimal spalling.
From microcrack to fracture cone
Under tension, microcracks grow along the interfacial transition zone between cement paste and aggregate. Concrete pulverizers generate local fracture cones through concentrated compressive and shear stresses; targeted gripping positions can stabilize the crack trajectory. In splitting processes, microcracks link to form a planar split plane between chains of boreholes.
Reinforcement and ductility
Reinforcement bridges cracks and allows plastic redistribution. During size reduction, residual elongation and the catenary action of bars must be anticipated. Steels can flow locally; a clean cut with steel shears prevents uncontrolled springback when releasing the last ligaments.
Influencing factors
- Strength class, aggregate grading, water content, and age of the concrete
- Reinforcement ratio, bar position, cover depth
- Moisture, temperature, and loading rate (brittleness increases at low temperatures and high loading rates)
- Boundary conditions: supports, restraint, existing cracks and openings
Deformation of natural stone and rock in rock excavation and tunneling
Rock behaves anisotropically. Joints, foliation, and bedding layers guide cracks. Stone and concrete splitters work with wedge forces that generate tension perpendicular to the borehole axis. This allows blocks to be released along natural planes of weakness—a benefit for low-vibration removal in tunneling and special operations.
Joints, water, and temperature
Water reduces effective stresses but can promote frost wedging. Temperature differences favor the opening of existing joints. The orientation of boreholes should cross the dominant joint set to obtain a clean split plane.
Bore pattern and wedge strategy
Regular bore spacing and sufficient edge distances prevent slabbing. Rock-splitting cylinders are effective when the bore is straight and load introduction is axial. Uneven wedge placement leads to torsion and unwanted spalling.
Deforming and separating steel and sheet elements
Steel exhibits pronounced plastic deformation. Steel shears and multi-cutters use shear loading at blade edges. Yield strength, toughness, and material thickness are decisive. Thin-walled sheet, such as in tanks, tends to buckling and springback; tank cutters must choose cutting sequence and supports to avoid unstable buckling fields.
Work hardening and cut quality
With repeated local forming, strength increases and toughness decreases—the cut becomes harder. Sharp blades reduce the proportion of plastic deformation and burr formation. Controlled feed motion limits heat and scaling.
Time and environmental influences: creep, shrinkage, temperature
Concrete creeps under sustained load and shrinks during drying. These time-dependent deformations open or close cracks and influence the demolition sequence. Temperature increases ductility in steel but lowers strength; in cold conditions steels harden and concrete behaves more brittlely. Moisture promotes alkali-silica reaction (ASR) and can alter crack susceptibility.
Loading rate
Rapid load changes increase the apparent strength of concrete but reduce crack warning. A metered, steady increase in force—e.g., via sensitively controlled hydraulic power units—supports predictable crack formation.
Practical guide: using deformation deliberately
- Pre-investigation: identify material type, reinforcement plan, jointing systems, supports, and restraint; account for moisture and temperature conditions.
- Tool selection: concrete pulverizers for compression- and shear-dominated size reduction; stone and concrete splitters for tension-dominated, defined crack planes; steel shears and multi-cutters for metallic components; tank cutters for thin-walled vessels.
- Plan grip and support points: support the component to create desired tension/compression zones; adapt bore patterns to existing weaknesses for splitting.
- Control force build-up: increase hydraulic pressure stepwise to observe crack initiation and avoid collateral damage.
- Define cutting and splitting sequence: intentionally leave residual sections and release them last to minimize springback and uncontrolled deformation.
- Handle reinforcement: expose reinforcing bars in time and sever with steel shears to avoid catenary action and unintended tension.
Measurement and assessment methods
Assessing deformation supports process control and documentation of work steps.
Visual inspection and crack-width assessment
Cracks preferentially run orthogonal to the maximum tensile stress. Crack widths provide clues to opening and residual load-bearing capacity. Spalling and fracture cones indicate dominant compression and shear components.
Strain and displacement measurement
Dial gauges or deformeters at reference points show whether load paths act as planned. Uniform displacement increase under steady pressure indicates stable crack progression.
Safety and protective measures under strong deformation
Unforeseeable deformations pose risks: entrapment between components, secondary failure with residual capacity, rebounding reinforcement due to springback. Safe zones, defined cutting sequences, and clear lines of communication reduce hazards. For vessels and tanks, internal stresses and residual media must be considered; a symmetrical separation strategy reduces the risk of buckling and tipping.
Typical failure patterns and how to avoid them
- Crushing failure instead of a split plane: wedge forces not introduced transverse to the desired crack plane—correct bore pattern and wedge alignment.
- Tool jamming: underestimated springback or load redistribution—make intermediate cuts, adjust supports.
- Edge spalling: edge distances too small or loading rate too high—build pressure more slowly, reposition gripper surface.
- Uncontrolled steel deformation: residual ligaments not severed deliberately—use steel shears early and plan the cutting sequence.
Application areas: deformation in the practical work environment
In concrete demolition and specialized deconstruction, understanding compression and shear deformation enables components to be reduced in a controlled manner with concrete pulverizers, while stone and concrete splitters create openings with minimal cracking. In interior demolition and cutting, a coordinated cutting sequence ensures low springback and cleanly separated reinforcement. In rock demolition and tunnel construction, the targeted use of tensile deformation along joints guides the split line. In natural stone extraction, blocks are released via defined split planes to minimize material loss. Special operations—such as dismantling tanks—require a combination of controlled plastic deformation and shear-dominated separation to avoid buckling and instability.