Calcium silicate brick is a widely used masonry building material for load-bearing and non-load-bearing walls in building construction. It stands for high dimensional stability, good sound insulation and non-combustibility. In existing buildings it is found from single-family houses to schools, from hospitals to administrative buildings. For planning, processing and deconstruction, it is crucial how the brittle, compression-resistant material responds to cutting, splitting and crushing. Depending on the objective, quiet, low-vibration methods come into play, such as static splitting using hydraulic rock and concrete splitters or controlled removal with concrete shears. The following sections consolidate fundamental knowledge and proven procedures—objective, safety-conscious, and with an eye to Darda GmbH applications in demolition, strip-out and specialized deconstruction.
Definition: What is meant by calcium silicate brick
Calcium silicate brick (also silicate brick, sand-lime brick, abbreviated KS) is a man-made masonry unit produced from quartz sand, lime and water. The mixture is formed under pressure and steam-cured in an autoclave. This creates a solid, dimensionally accurate structure with high compressive strength. Calcium silicate brick is non-combustible, exhibits a relatively high bulk density and thus provides good sound insulation. It is used as standard-size units, blocks, plane elements or large-format panels. Thin-bed joints are typical for plane-element masonry, as are load-bearing and bracing wall panels. The material is brittle and preferentially fractures along targeted stress lines—an aspect that can be exploited when choosing separation and deconstruction methods.
Properties, formats and manufacturing of calcium silicate brick
Calcium silicate brick is produced from natural sand and hydrated lime, which are mixed with water, pressed, and cured under saturated steam. Under the microscope, dense matrices with calcium silicate bonds are visible. This structure explains the high compressive strength but low tensile and flexural tensile strength. Bulk density classes and strength classes cover a broad spectrum—from lightweight units for partition walls to load-bearing elements for multi-storey buildings. Thermal conductivity is higher than in many lightweight materials, fire performance is excellent, and sound insulation is very good due to mass. Water can be absorbed capillarily; from a building physics perspective, plinth detailing and moisture protection must therefore be planned carefully.
Formats and microstructure
- Standard and block formats for conventional masonry
- Plane elements for fast installation with thin-bed mortar
- Solid and perforated units, depending on the desired bulk density and handling
- Factory-made, dimensionally accurate elements facilitate precise separation
Behavior during processing, separation and deconstruction of calcium silicate brick masonry
KS masonry reacts in a brittle manner. It fractures along targeted stress peaks and existing weaknesses (joints, openings, service chases). For controlled interventions, low-vibration methods have proven effective: static splitting using stone and concrete splitters, sectional nibbling of wall edges with concrete shears, and pre-drilling and sawing where precise cut edges are required. The goal is to respect load paths, prevent unintended crack propagation, and protect adjacent components.
Tool selection based on objective and boundary conditions
- Stone and concrete splitters: Introduction of defined tensile stresses via wedges/splitting cylinders; ideal for quiet, low-vibration opening and partial deconstruction of KS walls.
- Concrete shears: Nibbling of masonry, edges and projections; suitable for controlled removal, especially in mixed constructions with ring beams, lintels or concrete components.
- Hydraulic power packs: Power supply for handheld or portable tools where access is tight, in interior spaces and sensitive areas.
- Combination shears and multi-cutters: For mixed materials, e.g., when dismantling built-in components, conduits, or light steel sections adjacent to KS.
- Steel shears: Cutting reinforcement in adjacent concrete components or steel structural parts that brace KS walls.
- Tank cutters: Specifically for sheet metal and hollow bodies; in the KS context mainly relevant for adjacent special tasks, not for the masonry itself.
Selective demolition in existing buildings
For door openings, wall breakthroughs or partial removals, a clear separation joint is crucial. Typical practice: pre-score or pre-drill along the planned cut line, set splitting cylinders to induce directed crack formation, then remove remaining webs with the concrete shear. This keeps vibrations low and protects adjacent surfaces. For KS with ring-shaped concrete components (ring beams, reinforced concrete lintels), the concrete portions can be separated with the concrete shear.
Vibrations and building protection
Calcium silicate brick transmits vibrations in the form of fine crack formation. Static splitting significantly reduces the risk compared to impact or hammer use. In sensitive zones (buildings with high-value finishes, laboratories, clinics) low-vibration methods are standard.
Planning: Consider structure, load paths and temporary states
Before intervening, clarify load transfer, intermediate states and the function of wall panels. Load-bearing KS walls can provide bracing; openings change stiffness. Temporary shoring and the sequence of work steps must be defined accordingly. In moisture-exposed areas, assess material condition and masonry bonds, as saturated units fracture differently.
Dust and noise reduction
- Wet cutting or drilling where technically feasible
- Sectional splitting instead of continuous percussive work
- Dust extraction at drilling points; clear openings promptly
- Covers and partitions in interior spaces
Safety and occupational safety
Hydraulic tools must be operated as intended. For deconstruction work, protective measures apply against crushing, hydraulic leaks, flying fragments and dust. Manufacturer instructions and generally accepted technical rules should be observed.
Cutting, drilling and opening: proven procedures
Precise openings in KS often result from a combination of pre-drilling, static splitting and localized removal. Saw cuts deliver clean edges; where sawing is not possible, splitting cylinders assume crack control. Residual webs and cantilevering areas can be selectively removed with the concrete shear. Hydraulic power packs supply the tools even in areas without a heavy-duty electrical connection.
Typical work steps
- Mark out and assess structurally; install required temporary shoring.
- Pre-drill along the cut line (spacing and diameter matched to the splitting tool).
- Apply stone and concrete splitters to generate a controlled fracture joint.
- Remove webs and edges section by section with concrete shears.
- Secure, extract and separate materials by type.
- Dress edges; if necessary, level the masonry and prepare.
Recycling and disposal of calcium silicate brick
Source-pure KS material can be processed into recycled aggregates, for example for unbound base layers or as aggregate in recycled construction material mixes. Mortar adhesions and impurities (gypsum, wood, plastics, metals) should be minimized. Separate collection of KS, concrete and brick increases the material recycling rate. Legal requirements for waste classification and the use of recycled materials must be observed.
Reuse
Undamaged units can be reused in secondary applications after cleaning, provided load-bearing capacity and serviceability are ensured. Visual quality depends on the removal method; gentle, low-vibration methods promote preservation.
Calcium silicate brick compared with concrete and natural stone in demolition work
Compared to concrete, calcium silicate brick has high compressive strength but low tensile strength. This makes it susceptible to separation cracks through static splitting. Concrete shears are used especially where KS components are coupled with concrete or steel parts (lintels, ring beams, bearing zones). Natural stone exhibits anisotropic fracture surfaces depending on the rock type; KS, by contrast, fractures predominantly along joints and drill lines, making crack control more predictable.
Typical damage patterns and their significance for deconstruction
Hairline cracks, settlement cracks, moisture-related symptoms or frost spalling influence the fracture path. In pre-damaged zones the material may break out irregularly. The placement of splitting points and the sequence of work steps must be adapted accordingly. Preliminary trials in non-critical areas help assess the masonry’s response.
Areas of application and practical uses
In concrete demolition and specialized deconstruction, KS walls are often processed adjacent to reinforced concrete components. Concrete shears separate ring beams and concrete lintels, while stone and concrete splitters open KS surfaces with low vibration. In strip-out and cutting, quiet handheld tools are advantageous, for example in occupied buildings. For special tasks with limited access or restrictions on noise and dust, compact hydraulic systems are a practical solution. For rock demolition and tunnel construction as well as natural stone extraction, KS is not the target material; the splitting and shear principles used there show parallels in controlled crack guidance and can be transferred to KS.
Selection of suitable equipment and parameters
The choice of equipment category depends on wall thickness, bonding, embedded components and accessibility. For splitting, drill-hole diameter, cylinder stroke and splitting force must be coordinated. For concrete shears, jaw opening, blade geometry and force curve are decisive, especially at transitions to concrete.
Notes on sizing
- Match drill-hole diameter to the splitting wedge; select uniform hole spacing.
- Use smaller hole spacing for thin walls to control notch stresses.
- Identify KS/concrete transitions in advance; define the removal sequence.
- Select hydraulic power packs according to the required flow rate and pressure.
Quality assurance and documentation
For sensitive projects, vibrations, crack patterns and dust generation should be documented. Measurement points before and after the interventions provide comparison values. A clear sequence plan with inspection and approval points increases execution safety.
Regulations and permits at a glance
For masonry work, demolition and occupational safety, the relevant technical rules and official requirements apply. These must be reviewed and complied with on a project-specific basis. The information in this contribution is general in nature and does not replace project-specific planning.