Silicate concrete

Silicate concrete refers to structural and construction concretes in which silicate phases—from quartz-bearing aggregates to silicate binders and additives—govern the material properties. This orientation influences strength, tightness, abrasion resistance, chemical durability, and fracture behavior. For planning, execution, as well as concrete demolition and special deconstruction, understanding silicate concrete is crucial: it guides the selection of methods and tools, for example the use of concrete pulverizer or stone and concrete splitters during interior demolition and for precise, low-vibration concrete separation/cutting. Silicate-rich structures also play a central role in application fields such as rock excavation and tunnel construction as well as natural stone extraction, since they determine the mechanical behavior during splitting, cutting, or crushing.

Definition: What is meant by silicate concrete

In technical usage, silicate concrete is not a narrowly defined standard term, but a practice-oriented umbrella term for concretes whose binder and/or aggregate side is dominated by silicates. In conventional cement concretes, the load-bearing matrix is formed by calcium silicate hydrates (C-S-H), producing a silicate-governed material. In addition, silicate additives such as microsilica (silica fume), fly ash, or latent hydraulic ground granulated blast-furnace slag can promote matrix densification and increase durability. There are also alkali-activated systems (aluminosilicate-based) that dispense with Portland cement, as well as calcium-silicate–bound lightweight materials cured in an autoclave, such as autoclaved aerated concrete (AAC). What these variants have in common is that the silicate phases shape the microstructure, pore space distribution, and crack behavior. For deconstruction, this means: hardness, brittleness, grain structure, and reinforcement ratio are decisive for choosing the separation principle—such as gripping and crushing with a concrete pulverizer or controlled splitting with stone and concrete splitters.

Material properties and composition

Silicate concretes consist of aggregates (quartz, feldspars, silicate-rich natural stones), a binder (Portland cement or alternative silicate/alkali-activated systems), water, and, where applicable, admixtures and additives. The interaction of these components determines the matrix—from dense high-performance matrices to porosity-optimized lightweight concretes.

Matrix and strength

The C-S-H–dominated phases create a load-bearing yet brittle-elastic matrix. Density, silicate fines content, and degree of hydration influence compressive and splitting tensile strength, while the aggregate grain shape governs crack deflection behavior. Microsilica can reduce capillary pores and increase surface hardness.

Durability and tightness

Finely distributed silicates generally improve chloride and water impermeability. This reduces the corrosion risk for reinforcement, but increases the comminution work during demolition, as fracture surfaces may be smoother and crack propagation energy higher.

Thermal and mechanical behavior

With increasing silicate content, the elastic modulus often rises, making the material stiffer. Under impact loading, crack formation is preferentially initiated at aggregate–matrix interfaces. For selective separation, tools that allow controlled crack initiation are therefore suitable, such as stone and concrete splitters.

Damage mechanisms: ASR, abrasion, chemical influences

The alkali–silica reaction (ASR) arises from the interaction of an alkali-rich pore solution and reactive silica in aggregates. It can lead to gel formation, volumetric expansion, and network cracking. Visible features are dark spalls and fine crack networks, often accompanied by damp patches. Silicate concretes with dense matrices are more resistant to chlorides and sulfates, but can be sensitive to ASR under unfavorable boundary conditions. In deconstruction, ASR-damaged concrete often shows facilitated spalling in edge zones, which can make work with a concrete pulverizer easier. Chemical attack (e.g., acidic media) dissolves silicate structures more slowly than lime-dominated ones; however, the matrix can lose strength. For special demolition in chemically influenced environments, low-vibration methods to protect the surroundings are important.

Production, processing, and quality assurance

A targeted mix design controls the balance of strength, tightness, and workability. Low w/c ratios, suitable grading curves, and silicate fines improve durability but increase demands on compaction and curing. Quality assurance is performed via fresh and hardened concrete tests, microstructural evaluations and—on critical structures—supplementary durability tests. For future deconstruction concepts, it is worthwhile to document reinforcement density, component geometry, and concrete cover, as this information significantly eases the selection of a concrete pulverizer or split cylinders. Recording the strength class (concrete/steel) is also helpful.

Relevance in concrete demolition and special demolition

Silicate concrete exhibits brittle failure behavior with pronounced crack guidance along aggregate–matrix interfaces. This behavior can be purposefully exploited in deconstruction. In interior demolition and when separating load-bearing components, precise, low-vibration solutions are required to protect adjacent structures. Hydraulically operated systems allow controlled force application, minimize secondary damage, and reduce emissions in existing buildings.

Tool selection and methods

• concrete pulverizer: Gripping, crushing, and sorting in reinforced silicate concrete; suitable for opening component edges, separating slab strips, and exposing reinforcement prior to cutting with steel shear.
• stone and concrete splitters: Generate controlled crack lines via wedges/cylinders; ideal for low-vibration deconstruction of massive cross-sections, e.g., in foundations or walls, as well as for special operations in sensitive areas.
• hydraulic power pack: Supplies mobile tools consistently and enables reproducible separation operations—important for components made of high-density silicate concrete.
• combination shears and Multi Cutters: Flexible separation when concrete and steel portions alternate; the choice depends on component thickness, reinforcement ratio, and accessibility.
• steel shear: After concrete removal, precise cutting of exposed reinforcement; useful for on-site, single-grade separation.
• tank cutter: For special operations with steel components in industrial plants, when silicate concrete jackets have been selectively removed and steel plates must be cold cut.

Strategy in existing structures

1. Component analysis: concrete age, strength class (concrete/steel), aggregates, reinforcement, crack pattern (e.g., ASR indicators).
2. Choice of separation line: exploit brittle-silicate crack propagation by directing stresses with splitters.
3. Preparation: weaken edges, set core drillings as crack starters, then apply the concrete pulverizer sequentially.
4. Single-grade separation: open concrete and steel with a concrete pulverizer, separate reinforcement with steel shear or Multi Cutters.
5. Minimize emissions: dust suppression, adjusted cutting and splitting speeds, low-vibration work sequence.

Rock excavation, tunnel construction, and natural stone extraction

Many rocks in tunnel faces and quarries are silicate-rich (e.g., granites, gneisses, quartzites). Their fracture behavior partially resembles silicate-dominated concrete: high hardness, brittle crack propagation, pronounced grain structure. stone and concrete splitters optimally leverage these properties through controlled splitting forces, especially when vibrations and noise are to be limited. In natural stone extraction, precisely setting split lines can increase block yield and reduce cutting losses. In tunnel construction, the controlled opening of disturbed zones supports safe advance (tunnel excavation) without weakening surrounding structures.

Interior demolition and cutting in existing structures

In interior demolition, dense, silicate-rich components are common (e.g., slabs, walls, columns). Here, a concrete pulverizer enables sequential opening, while combination shears and Multi Cutters efficiently address alternating material layers (concrete, reinforcement, embedded parts). Hydraulically driven tools are advantageous in confined areas because they are compact, precise, and easily metered. Cutting sequences are planned to preserve load paths and avoid secondary damage.

Identifying silicate concrete on site

Reliable classification is achieved through documentation and testing. Clues are also provided by macro features and simple on-site checks:

• Light, quartz-rich aggregate appearance; hard, glassy fracture surfaces.
• Low water uptake on freshly exposed surfaces in dense matrices.
• Intense sparks during rebar cutting (an indicator of a dense matrix with strong bond).
• Crack patterns: fine crack networks and efflorescence can indicate ASR.
• Drilling dust: fine, light dust with quartz-rich aggregates; indications of abrasiveness.

Occupational safety and emissions

Working silicate-dominated materials generates mineral dust that can contain crystalline silica. Low-dust operation is therefore essential: wetting, point extraction, clean cutting and splitting sequences, and suitable personal protective measures. Vibrations and noise are reduced through controlled splitting and force-regulated hydraulics. In sensitive environments (laboratories, clinics, occupied buildings), low-vibration methods and precise tool guidance are crucial. Implement noise reduction measures and maintain low vibration levels.

Recycling, reuse, and circular economy

Recycled material obtained from silicate concrete can be used as aggregate for unbound base layers, frost protection, or—after processing—as recycled aggregate in concrete, yielding recycled concrete. Dense, silicate-rich concretes often deliver robust, grain-stable recyclates. For high-value applications, grain shape, fines content, and residual mortar content are decisive. On-site single-grade separation—supported by a concrete pulverizer for concrete and a steel shear for reinforcement—improves fraction quality, shortens transport logistics routes, and increases the depth of recovery.

Planning and execution: practical guidelines

Compact procedures have proven effective for handling silicate concrete efficiently:

1. Survey the existing structure: material, reinforcement, construction age, possible ASR damage.
2. Define the objective: interior demolition, selective deconstruction, full demolition, block extraction.
3. Combine tools: stone and concrete splitters for crack initiation, concrete pulverizer for opening and separating, Multi Cutters/steel shear for metal parts.
4. Meter forces: tune the hydraulic power pack to material thickness and material response, define splitting sequences.
5. Control emissions: minimize dust, noise, and vibrations; keep sections small and apply dust suppression and noise reduction measures.
6. Prepare recycling: separate fractions, remove reinforcing steel, plan transport logistics.

Typical application fields with a silicate connection

In concrete demolition and special demolition, dense, silicate-rich components with high strength predominate; precise splitting and crushing are particularly effective here. In interior demolition and cutting, the focus is on selective opening and controlled load redistribution. In rock excavation and tunnel construction, controlled splitting forces support safe advance in silicate-rich rocks. In natural stone extraction, the material behavior is leveraged to release blocks along naturally weaker planes. Special operations require tailored approaches when silicate concrete is processed in combination with steel or tank components.