Crushing force is a central parameter in demolition, splitting, and cutting technology. It describes the compressive force applied by tools to press together, break open, or stabilize materials such as concrete, masonry, natural stone, or metal prior to cutting. In Darda GmbH’s practice, crushing force occurs with concrete crushers, stone and concrete splitters, rock splitting cylinders, combination shears, multi cutters, steel shears, and tank cutters—each adapted to the requirements in concrete demolition and specialized deconstruction, during strip-out and cutting, in rock excavation and tunnel construction, in natural stone extraction, as well as in special operations.
Definition: What is meant by crushing force
Crushing force refers to the compressive force acting on a workpiece, transmitted through jaws, cylinders, wedges, or blades onto a limited area to locally densify material, initiate cracks, and trigger fracture processes. It acts as a compressive force perpendicular to a contact surface and differs from tensile or shear forces. In hydraulic tools, crushing force is generated by system pressure and the effective area of a cylinder and transmitted to the material via levers, joints, or wedge mechanisms. In concrete, crushing force leads to particle rearrangement, microcracking, and ultimately macroscopic fracture; in rock, it opens up bedding planes and joints; in metals, the crushing action often stabilizes the cutting zone or serves as pre-damage prior to shear processes.
Physical principles and units
Crushing force is given in newtons. In hydraulic systems, approximately F = p × A applies, i.e., force equals pressure times piston area. In addition to total load, the decisive factor is the contact stress (force per contact area), which determines whether a material undergoes plastic deformation, microscopic cracking, or brittle fracture. With tools featuring teeth or edges, crushing force is concentrated on small areas; the resulting high contact stress creates targeted crack initiation sites. Wedge and splitting mechanisms convert an axial cylinder force into radially acting crushing forces, for example when stone and concrete splitters are inserted into drilled holes and the borehole wall is loaded evenly. Losses arise from friction, joint play, and elastic compliance; the usable crushing force at the tool tip is therefore below the theoretical cylinder force.
Operating principles in demolition and splitting technology
Concrete crushers: crushing, fragmenting, breaking
Concrete crushers transmit a large, controlled crushing force through two opposing jaws. Concrete is first locally compressed between the teeth, then cracks form and propagate along weak zones such as aggregate interfaces or existing joints. In reinforced members, the concrete compression zone is destroyed, after which shear or cutting zones of the crusher engage the rebar. The crushing action determines how quickly and energy-efficiently components such as slabs, walls, or foundations are fragmented in concrete demolition and specialized deconstruction.
Stone and concrete splitters as well as rock splitting cylinders
Splitters primarily act as wedge systems: a hydraulic cylinder drives wedges or expansion elements apart and generates a radial crushing force at the borehole wall. The high contact stress creates tensile cracks in the material that propagate from the borehole. This method is low-vibration and precise, suitable for rock excavation and tunnel construction, natural stone extraction, and sensitive deconstruction when vibrations or noise must be minimized. Rock splitting cylinders are matched to the borehole geometry to introduce the crushing load safely and repeatably.
Combination shears, multi cutters, steel shears, and tank cutters
With cutting tools for metal, crushing force often serves as a preload: the workpiece is pressed between blade surfaces to minimize play and stabilize the kerf. Only then does shearing begin. With tank cutters, the crushing phase can reduce undesired springback and guide the cutting line. In special operations, e.g., in sensitive areas, a precisely metered crushing action supports safe, controlled separation.
Calculation, design, and key parameters
For technical evaluation, crushing force, compressive strength, tensile or splitting tensile strength, and contact stress are considered together. Design steps can be structured as follows:
- Determine the available system pressure of the hydraulic power pack and the effective piston area.
- Account for lever or wedge ratios and mechanical losses (friction, joints, elastic deformation).
- Estimate the contact area at teeth, edges, or wedge faces to determine contact stress.
- Cross-check against material properties: concrete compressive strength and splitting tensile strength, uniaxial compressive strength of rocks, yield strength and toughness of metals.
- Adjust geometry and process parameters (jaw profile, tooth geometry, borehole spacing and depth, cycle times) to achieve the desired crack propagation.
In concrete, compressive strength is often significantly higher than tensile strength; crushing force is therefore used to overload compression zones first and then initiate tensile cracking. In rock, anisotropy (bedding, joints) governs crack direction, which is why borehole patterns and positioning of splitting cylinders are used to purposefully steer the crushing action.
Factors influencing the crushing action
Tool geometry and contact areas
Tooth geometry, tip, edge radius, and jaw profile influence contact stress. Sharply contoured teeth increase local stress and facilitate crack initiation, while broader areas promote more uniform load distribution and controlled fracture patterns. Tool wear enlarges the contact area and reduces the effective crushing action; regular retipping or replacement of wear parts stabilizes performance.
Hydraulic power packs and system condition
The available crushing force depends on system pressure and flow rate. Pressure level dictates maximum force, volumetric flow the operating speed. Temperature, oil quality, filter condition, and hose cross-sections influence dynamics. A stable hydraulic pressure is essential for repeatable crushing processes; pressure drops lead to longer cycle times or incomplete crack formation.
Material properties and component geometry
Concrete age, moisture content, aggregate, and reinforcement ratio alter fracture behavior. In high-strength or fiber-reinforced concrete, higher contact stresses and longer hold times are required. In natural stone, grain bonding and joints determine the necessary borehole geometry for splitting cylinders. Component thickness and edge distance control whether cracks run in depth or spall laterally.
Environmental and boundary conditions
Temperature, humidity, frost, and dirt on contact surfaces influence friction and thus effective crushing force. In sensitive environments, low-vibration procedures with splitters enable precise, controlled interventions, for example in specialized deconstruction or during strip-out.
Areas of application and typical uses
- Concrete demolition and specialized deconstruction: Concrete crushers crush concrete bodies, open cracks, and produce manageable fragment sizes for subsequent steps. Crushing sequences can be planned to avoid overloading load-bearing areas.
- Strip-out and cutting: Before separating profiles or sheets, crushing force ensures a secure material closure. With tank cutters, pressing stabilizes the cutting zone.
- Rock excavation and tunnel construction: Stone and concrete splitters convert cylinder force into radial crushing loads in the borehole. This opens joints and dislodges blocks in a controlled manner with low vibrations and reduced secondary damage.
- Natural stone extraction: Rock splitting cylinders use crushing force to split along natural weak zones, producing defined blocks with minimal material loss.
- Special operations: In confined spaces or sensitive zones with strict emission or vibration limits, crushing-force-based methods enable controlled work with high precision.
Practical execution and quality assurance
Measurement and verification of crushing force
The applied crushing force is estimated using pressure gauges on the hydraulic system, known piston areas, and known transmission ratios. In addition, trial loading on reference components, imprints on contact surfaces, or documented crack patterns provide indications of the actual crushing action. Regular calibration and functional checks ensure reproducible results.
Occupational safety and precautions
Crushing processes generate high local stresses and potential springback. Safety clearances, appropriate personal protective equipment, secure supports, and a clear communication routine are essential. In the vicinity of utilities, embedded parts, or tanks, additional hazard assessments are advisable. Instructions in operating manuals must be observed; legal requirements may vary by location and are general in nature.
Best practices for efficient crushing operations
- Select suitable application points: edges, joints, and weak zones accelerate crack formation.
- Match jaw and tooth geometry to the material and task; monitor wear condition.
- Keep hydraulic pressure stable; operate oil temperature and flow rate within allowable ranges.
- For splitters, design borehole diameter, depth, and spacing to the rock and the desired block size.
- Work sequentially: first initiate (high contact stress), then maintain hold time, then reapply.
- Account for reinforcement: with concrete crushers, combine crushing and cutting effectively.
- Keep contact surfaces clean to ensure friction and force transmission.
Limitations and alternatives
Pure crushing methods reach limits with extremely tough or highly ductile materials as well as with very thick cross-sections. Then combining with cutting, drilling, sawing, or waterjet is sensible. In high-strength concrete or dense igneous rocks, optimized borehole patterns and longer hold times improve the effectiveness of splitting cylinders. The choice of the appropriate tool—e.g., concrete crushers in secondary demolition or stone and concrete splitters in massive rock—depends on material, component geometry, environmental constraints, and quality requirements.