Material strength describes a material’s resistance to mechanical loads up to failure. In the context of deconstruction, demolition, and extraction, it is a central planning parameter: from it, suitable methods, tools, and process steps are derived – from hydraulic splitting in concrete and rock to crushing, cutting, and shearing of reinforced components and steel. In practice this means: those who classify material strength correctly can work in a controlled, low-vibration, and efficient manner – for example with rock and concrete splitters, concrete pulverizers, combination shears, Multi Cutters, steel shears, tank cutters, and the appropriate hydraulic power units.
Definition: What is meant by material strength
Material strength is the ability of a material to withstand external forces without breaking, deforming excessively, or shearing off. A distinction is made between compressive strength, tensile strength, flexural tensile strength, and shear strength. The governing parameters depend on the material (e.g., concrete, steel, natural stone), the stress state (uniaxial, multiaxial), the load duration (static, dynamic), and environmental conditions (moisture, temperature). While concrete exhibits high compressive but low tensile strength, steels are ductile and possess high tensile and shear strengths. Rocks vary widely in material strength and anisotropy, depending on fabric, jointing, and mineral composition.
Relevance of material strength in concrete demolition and specialized deconstruction
Material strength governs the choice of method, the sizing of tools, and the sequence of work steps. The low tensile strength of concrete favors hydraulic splitting – here rock and concrete splitters generate controlled tensile stresses that open components along planes of weakness. For massive, reinforced components, concrete pulverizers (also referred to as Concrete Crushers) apply locally high compressive and shear stresses to crumble concrete and expose reinforcement. Combination shears, Multi Cutters, steel shears, and tank cutters are used when metallic components with high tensile strength or tough fracture behavior must be separated. A sound assessment of material strength reduces energy use, vibrations, and dust, and improves the separation rate of concrete and steel – crucial for strip-out, selective deconstruction, rock excavation, tunnel construction, natural stone extraction, and special operations.
Types of material strength in concrete, steel, and rock
The following strength types are particularly relevant for demolition and splitting processes because they directly determine failure mechanisms and thus influence tool selection and process parameters.
Compressive strength
Compressive strength describes resistance to compressive loads. Concrete achieves its highest values here, which vary greatly depending on class and age. With concrete pulverizers, compressive strength is locally exceeded: crushing and wedging effects generate compressive and shear stresses that fragment the concrete. In natural stone, compressive strength depends on fabric, grain bonding, and porosity; where joints are oriented, seemingly high compressive resistance can be effectively overcome by targeted force introduction.
Tensile and splitting tensile strength
Concrete has significantly lower tensile and splitting tensile strength than compressive strength. Rock and concrete splitters exploit this: hydraulic spreading forces create tensile stresses that initiate cracks and drive them forward in a controlled way. This method is low-vibration and suitable for sensitive environments. In rock, joints, bedding planes, and anisotropies act as natural planes of weakness – targeted splitting wedges use these to create defined fracture surfaces.
Flexural tensile strength and shear strength
Flexural tensile strength is particularly relevant for slabs, decks, and cantilevers where loads generate lever arms. Shear strength governs behavior at joints, in wall openings, and at column edges. Concrete pulverizers generate combined flexural and shear stresses, effectively fragmenting components. For precise separation cuts in reinforcement and profiles, shearing processes with shear tools are appropriate.
Yield strength and tensile strength of steel
Steels exhibit ductile behavior: yield strength marks the onset of permanent deformation, tensile strength the maximum load-carrying capacity. For separating rebars, beams, and tanks, shearing or cutting forces must be chosen to load the material safely beyond its capacity. Steel shears, combination shears, Multi Cutters, and tank cutters are selected according to material grade and cross-section.
Rock material strength and anisotropy
The uniaxial compressive strength of rock varies widely. Fissile, jointed, or layered rocks show direction-dependent strengths. For rock excavation and tunnel construction, it is crucial to identify preferred joint orientations and align splitting forces accordingly – this is where splitting cylinders and wedge systems excel, as they introduce forces in a controlled manner.
Influencing factors on material strength
Material properties are not constants. They change with material condition, component geometry, and environment. For a reliable practical assessment, the following factors must be considered:
- Moisture content and temperature: influence hydration, brittleness, and friction at crack surfaces.
- Age and curing: maturity of the concrete, carbonation, and microcracking.
- Aggregates, grading, fabric: determine load-sharing, porosity, and anisotropy.
- Reinforcement, prestressing, bond: increase reserves in tension and flexural tension, alter fracture patterns.
- Damage and fatigue: pre-damage lowers effective strength, cracks guide fracture paths.
- Stress state and boundary conditions: multiaxial loading and supports shift failure thresholds.
Testing and measurement methods in deconstruction
Systematic determination or estimation of material strength is the basis for safe work plans. Combinations of destructive and low-destructive methods deliver robust results.
Destructive tests
Core sampling followed by compressive or splitting tensile testing provides reference values. Orientation, diameter, and storage of cores influence results. These tests also serve to calibrate indirect methods.
Low-destructive and indirect methods
Rebound hammer for estimating surface strength, ultrasonic pulse velocity for assessing homogeneity and cracking, pull-off tests for bond tensile strength and surface layer strength. Individual values must be interpreted in context.
On-site interpretation
The combination of several methods increases reliability. Coupled measurements (e.g., rebound plus ultrasound) and plausibility checks through cores lead to realistic strength intervals instead of single values.
Material strength and tool selection: from splitting to cutting
Correct mapping of strength type to method reduces energy demand and risk. Decisions are guided by component geometry, material mix, and boundary conditions.
- Splitting: exploits the low tensile strength of concrete and rock; rock and concrete splitters apply controlled spreading forces in drill holes.
- Crushing and size reduction: concrete pulverizers use local compressive and shear stresses for selective deconstruction and exposing reinforcement.
- Shearing and cutting: steel shears, combination shears, Multi Cutters, and tank cutters overcome the tensile and shear strength of metallic components.
- Hydraulic power units: supply pressure and flow rate influence force, speed, and cycle; they must be matched to workpiece strength and the work objective.
Planning, safety, and environmental protection
Robust planning considers material strength as well as safety and environmental impacts. Legal requirements depend on location and application; the following points serve as general guidance.
- Pre-investigation: material analysis, reinforcement detection, component condition, environmental conditions.
- Method selection: prioritize low-vibration, noise-reduced methods in sensitive surroundings; splitting instead of impact energy, crushing instead of blasting.
- Parameterization: drill pattern, splitting spacings, engagement points for concrete pulverizers, shear paths for steels.
- Monitoring: force/pressure control, crack propagation, settlements, dust and noise mitigation.
- Documentation: measurements, sequence, demolition states, and separation rate for recycling and proof of compliance.
Examples from application areas
In concrete demolition and specialized deconstruction, massive walls are often first opened with rock and concrete splitters to generate controlled crack patterns; subsequently, concrete pulverizers fragment components and expose reinforcement. In strip-out and cutting, shear tools enable separate removal of metallic installations. In rock excavation and tunnel construction, hydraulic splitting utilizes existing joints; defined fracture surfaces are produced with low vibrations. In natural stone extraction, blocks are detached along natural planes of weakness. Special operations – for example with high-strength, tough materials or restricted access – require precise adaptation of tools and forces to the prevailing material strength.
Distinction from related parameters
Material strength is not the same as hardness, toughness, or stiffness. Hardness describes resistance to indentation; toughness the ability to absorb energy up to fracture; stiffness the relationship between stress and strain (modulus of elasticity). In practice these quantities interact: a hard, brittle material can have high compressive strength but low toughness – ideal for splitting processes. A ductile, tough steel, on the other hand, requires adapted shearing or cutting forces.
Assess technical parameters in practice
For operational decisions, ranges are more useful than single-point values: depending on class, age, and condition, concrete can exhibit compressive strengths from about 20 to well over 60 MPa, while splitting tensile strength is typically a fraction of that. Rocks range from soft, porous sedimentary rocks to high-strength igneous rocks. Steels range from low to very high strength classes. From these intervals, one derives drill patterns, splitting paths, engagement points for concrete pulverizers, and shearing and cutting parameters. The combination of visual inspection, low-destructive testing, and spot-check reference tests yields a robust decision basis that is flexibly adapted to local conditions.