Crushing describes the targeted reduction of components, structures, and rock into manageable piece sizes. In concrete demolition, building gutting, rock breakout and tunnel construction as well as in natural stone extraction, it is a central work step: structural elements are detached, components are separated, and materials are prepared for transport, recycling, or further processing. In practice, the spectrum ranges from hydraulic splitting through shearing and cutting to crushing. Tools such as concrete pulverizers and rock wedge splitter and concrete splitter from Darda GmbH are typical solution approaches for this, which can be combined depending on material, geometry, and boundary conditions.
Definition: What is meant by crushing
Crushing encompasses all methods used to deliberately reduce the piece size of solid materials—such as concrete, reinforced concrete, natural stone, or steel sheet. This is achieved by splitting, shearing, cutting, crushing, compressing, or removal. The goal is controlled fragmentation with defined edges and the lowest possible energy and emissions. Crushing serves as the connecting element between detaching a component from the composite (deconstruction, dismantling) and material recovery (construction waste sorting, recycling). In construction practice, the focus is particularly on concrete pulverizers for compression- and shear-dominated processes as well as rock wedge splitter and concrete splitter for wedge- and tensile stress–dominated splitting processes.
Technical fundamentals and operating principles of crushing
Physically, crushing is based on stress states in the material. In brittle construction materials such as concrete or natural stone, locally introduced tensile stresses lead to crack formation and fracture. Hydraulically driven splitter systems use wedge and cylinder technology to generate controlled crack propagation along the weakest zones. Concrete pulverizers, on the other hand, apply high compressive and shear forces via massive jaws, break the concrete, and cut or kink reinforcing steel. In ductile material such as steel, shear and cutting forces dominate, as produced by steel shears, combination shears, or multi cutters. The choice of operating principle is determined by material behavior, component thickness, reinforcement level, accessibility, and permissible emissions (vibrations, noise, dust).
Methods and tools at a glance
Depending on the task, methods are used selectively or in combination. With its tool groups, Darda GmbH covers the essential mechanisms of crushing and thus enables a working approach adapted to the material and surroundings.
Concrete pulverizers
Concrete pulverizers operate with high surface pressure and shear action. They break concrete, crush aggregates, and—depending on the design—can cut reinforcing steel; comparable are concrete crushers for controlled compression. Typical applications include biting off walls and slabs, reducing foundation heads, or pre-crushing for downstream sorting applications. Advantages include direct separation of concrete and steel, well-controlled piece sizes, and a comparatively quiet workflow without blasting effects.
Rock and concrete splitters
Hydraulic rock and concrete splitters are wedge-based. After drilling boreholes, splitting cylinders are inserted that generate radial tensile stresses via hydraulic wedges. This creates controlled cracks and defined fracture edges. This method is particularly suitable for massive cross-sections, heavily reinforced concrete (in combination with subsequent steel cutting), and natural stone. It is low in vibrations and often suitable for sensitive environments.
Combination shears and multi cutters
Combination shears and multi cutters combine cutting, crushing, and biting. They are suitable for mixed structures of concrete, masonry, and metal—for example, in the selective deconstruction of plants, when opening channels, or when separating structural steel section in complex nodes.
Steel shears and tank cutters
Steel shears are designed for cut-dominated crushing of steel sections, beams, and sheets. Tank cutters are used when tanks, silos, or tank walls need to be segmented. Both tool types enable controlled disassembly with reproducible cut edges.
Application areas and working methods
Crushing is anchored in different disciplines. The choice of tool follows from the task, building material, and environmental requirements.
Concrete demolition and special demolition
In selective deconstruction, load-bearing and non-load-bearing components are separated, crushed with low emissions, and removed separately. Concrete pulverizers reduce walls, slabs/ceilings, and columns in a controlled manner, while rock and concrete splitters break up massive foundations, abutments, or machine foundations with minimal vibration input. For highly reinforced components, splitting can be done first, followed by segmenting the exposed reinforcing steel with steel shears.
Building gutting and cutting
In building gutting, extensions, service runs, shafts, and secondary components are removed. Multi cutters and combination shears are suitable for mixed materials. Concrete pulverizers produce handy pieces for urban construction logistics. Tank cutters are used when dismantling containers in industrial or plant areas.
Rock breakout and tunnel construction
In rock, splitting cylinders are frequently used because they act in boreholes and open the rock along natural weak zones. This reduces vibrations and allows controlled detachment of blocks in areas with strict requirements or low overburden.
Natural stone extraction
In natural stone extraction, splitters create defined separation joints along bedding or joint systems. This produces blocks with dimensionally accurate fracture edges that are then further dressed. Avoiding blasting can minimize quality loss due to microcracks and increase recoverability.
Special applications
For sensitive assets, densely built-up areas, near vibration-sensitive installations, or where there are structural constraints, hydraulic splitting and jaw-based methods often offer advantages. The work can be planned in stages and adapted to the respective situation.
Process planning, drilling patterns, and piece sizes
Careful planning determines performance and results. In splitting, borehole diameter, hole spacing, embedment depth, and wedge orientation are decisive. The fracture joint should run in the load direction and use existing weak zones. For concrete pulverizers, jaw opening, jaw geometry, attack points, and work sequence influence piece size and the sharpness of separation between concrete and steel.
- Material parameters: compressive strength, tensile strength, grain structure, moisture content
- Component geometry: thickness, edge distance, restraint, bond to adjacent components
- Reinforcement: location, diameter, mesh or bar geometry
- Accessibility: clearances, approach angle, position of the power unit
- Emissions: permissible vibrations, noise and dust limits
- Logistics: target piece sizes for removal, interim storage, and recycling
Hydraulic power packs, power supply, and interfaces
Hydraulic power packs provide volume flow and pressure for splitting cylinders, concrete pulverizers, and shears. For stable operation, hydraulic pressure, flow, and temperature management must match the tool size. Important factors include suitable couplings, hose lengths, clean hydraulic fluid, and hydraulic control tuned to the application. In alternating operation, a clear sequence is recommended to avoid pressure spikes and energy losses.
Emissions, occupational safety, and environmental protection
Crushing generates noise, dust, and vibrations. Hydraulic splitting is often low in vibrations, while shearing and crushing methods can generate structure-borne sound. Water misting, extraction, and coverings reduce dust. Rebound protection and safe standing areas mitigate hazards from pieces breaking out. Legal requirements and local regulations must always be observed; a project-specific hazard analysis and appropriate protective measures are essential.
Quality assurance, maintenance, and service life
The tool service life depends on correct application and maintenance. For concrete pulverizers, jaws, blades, and bearing points must be checked; for rock and concrete splitters, wedges, tie rods, and seals. Regular inspections of hoses, couplings, and hydraulic fluid maintain performance. Wear parts should be replaced in good time to ensure clean fracture surfaces and consistent forces.
Recycling and recovery
Clean separation is the key to high-quality recovery. Concrete pulverizers can expose reinforcement; steel shears and multi cutters segment reinforcement and profiles. Adapted splitting produces pieces that are easy to sort and transport. Processed concrete debris can serve as recycled concrete aggregate, steels return to the metallurgical cycle, and natural stone is often reused.
Key parameters, performance, and cost-effectiveness
Essential key parameters are splitting force, jaw opening, cutting force, cycle time, hydraulic pressure, and volume flow. Actual performance results from the interaction of tool, power pack, material, and work sequence. A method is economical if it delivers reproducible piece sizes with the lowest possible emissions and acceptable energy input—while ensuring safe and plannable execution.
Practice-oriented procedures
For massive foundations, a combination of borehole drilling, hydraulic splitting, and subsequent cutting of reinforcement is recommended. For wall and slab elements, a concrete pulverizer with targeted attack points achieves rapid fragmentation. Tanks and steel construction are segmented into transportable sections with steel shear or tank cutters. In complex deconstructions, a graduated sequence—detaching, crushing, sorting, and haulage logistics—provides clarity and safety.
Typical mistakes and how to avoid them
- Inappropriate drilling patterns for splitting: adjust hole spacing, depth, and orientation to material and geometry.
- Excessive piece size: match piece size to lifting and transport equipment, define dimensions early.
- Neglected reinforcement: locate steel runs and plan cutting steps instead of overloading the jaws.
- Undersized hydraulic supply: size pressure and volume flow to the tool’s demand.
- Insufficient emission controls: provide dust suppression, noise control measures, and ground vibration monitoring in good time.