Autoclaved aerated concrete (AAC), often also referred to as aerated concrete or cellular concrete, is widely used in new builds and existing structures. The deconstruction of these light, porous components places special demands on planning, tool selection and dust management. In AAC demolition, precise separation, low vibration levels and clean separation of material streams take center stage. In everyday construction practice, this touches the fields of concrete demolition and special demolition, building gutting and cutting as well as selective interventions in existing structures. Tools such as concrete demolition shear and hydraulic rock and concrete splitters from Darda GmbH enable controlled, material-appropriate work—especially at connections, transitions to reinforced concrete, or when working near load-bearing neighboring components to be preserved.
Definition: What Is Meant by AAC Demolition
AAC demolition refers to the controlled, selective release, downsizing and removal of components made of autoclaved aerated concrete (AAC), such as walls, lintels, slab edges or infill masonry. The goal is low-damage separation of the elements, taking into account the low bulk density, brittle structure and possible embedded parts such as anchor, U-sections with reinforcement or installation rails. The demolition is carried out as manual demolition work, machine demolition, or a combination—depending on component thickness, accessibility, connection details and requirements for noise and vibration control.
Material Properties of AAC and Their Significance for Deconstruction
AAC features a low bulk density and a porous, capillary-active structure. This results in good breakability but also increased fine dust release. Compressive strength typically lies—depending on density class—in the lower single-digit N/mm² range; components are therefore light but brittle. Mortar joints (thin-bed or conventional mortar), plaster layers and embedded reinforcement patches influence separation behavior. Moisture content, building age and freeze-thaw effects can change fracture patterns, which must be considered when selecting tools.
Methods and Tools in AAC Demolition
The choice of method is guided by structural considerations, component dimensions, required vibration and noise control, and the desired reusability of adjacent components. A combination of manual pre-work and hydraulically assisted separation is often proven.
Manual Release and Selective Dismantling
For non-load-bearing, thin AAC walls, manual release along the joints is suitable. Before the actual demolition, services are exposed and plaster layers are scored to avoid uncontrolled spalling. Smaller elements can be stripped out and removed in manageable pieces.
Mechanical Separation with Concrete Demolition Shear
Concrete demolition shear is particularly suitable for precise interventions in AAC when connections to reinforced concrete, ring beams or reinforced bearings must be separated. Through controlled crushing and shearing movements, transitions can be released without percussive impacts. In building gutting and special demolition, concrete demolition shear reduces vibrations, protecting adjacent components and installations.
Low-Stress Demolition with Hydraulic Wedge Splitter
Hydraulic wedge splitter work with hydraulically generated splitting forces that are introduced into drilled holes. In AAC this allows the creation of defined fracture lines, for example to form wall openings or to detach larger wall panels in a way that preserves adjacent structures. This method is low in vibration and supports clean cuts for subsequent adjustments.
Combined Methods with Multi Cutters and Combination Shears
In mixed masonry, lath/plaster carriers, light steel profiles or reinforcement inserts, Multi Cutters and combination shears can support separation. They are used when non-AAC embedded parts hinder dismantling or when components are tied into load-bearing structures.
Detaching Steel Components with Steel Shear
Steel shear is used to cut through mounting brackets, installation rails, reinforcement connections or window/door frames that are holding AAC parts back. This enables clean separation of material fractions and facilitates disposal.
Hydraulic Power Pack and Control
The hydraulic power pack supplies concrete demolition shear, splitting cylinders and other hydraulic tools; finely controllable hydraulic power units are crucial for precise pressure build-up and sufficient flow rates to ensure uniform splitting or shearing. In sensitive areas, a gentle ramp-up at low speed is recommended to guide cracks in a controlled manner.
Planning and Construction Sequence in AAC Demolition
A systematic sequence increases safety, quality and cost-effectiveness. Before starting, perform an inventory with a focus on material, connections and service routing.
- Survey: Visual inspection, locating utilities, clarifying bearing and connection details (ring beam (tie beam), lintels, U-sections).
- Temporary safeguarding: Shoring when intervening in load-bearing or bracing elements; define the deconstruction sequence.
- Dust and noise control: Plan barriers, negative-pressure zones and targeted wetting.
- Pre-dismantling: Remove finishes, plaster layers in the separation zone and release fixings.
- Mechanical separation: Use concrete demolition shear at connections; splitting technique for defined cracks.
- Pure material separation: Construction waste separation of AAC, plaster, mortar, metal and wood.
- Quality assurance: Visual checks of cut edges, documentation and safeguarding of adjacent components.
Dust and Emissions Management
Because of the fine pore structure, AAC demolition generates a lot of fine dust. An effective dust concept is therefore central.
Dust Reduction
- Targeted wetting in the separation zone without soaking the material.
- Locally extracted work areas, if necessary with negative pressure (use dust extraction).
- Prefer low-dust methods: splitting technique and shear-based separation instead of breaker hammer.
Noise Control and Vibrations
- Use shears and splitters instead of impact tools, especially in building gutting.
- Low-load, stepwise separation sequences to limit secondary breakage.
Selective Deconstruction, Disposal and Recycling
AAC can generally be separated by material type. Pure fractions can be recycled depending on regional options or used as backfill and lightweight aggregates. Plasters, setting and thin-bed mortars as well as adhering insulation materials must be handled separately. Metallic inserts are exposed on site with steel shear or concrete demolition shear and likewise collected separately. Disposal routes should be agreed in advance; specific requirements and limit values are project-specific and must comply with generally applicable regulations.
Areas of Application and Typical Use Cases
AAC demolition appears in various fields of application:
- Building gutting and cutting: Removal of non-load-bearing AAC walls, openings in existing walls, adjustments for new service routes. Concrete demolition shear provides clean edges at connections, splitters provide defined fracture lines.
- Concrete demolition and special deconstruction: Selective separation at ring beams, reinforced concrete columns or slab connections; splitting and shear techniques reduce vibrations and protect adjacent components.
- Special use: In vibration-sensitive areas, such as near listed buildings or in ongoing building operations, low-vibration methods with hydraulic wedge splitter are particularly suitable.
- Rock excavation and tunnel construction / natural stone extraction: Although material-wise different, the process principle is related: Controlled crack initiation using splitting cylinders is known from the rock and natural stone sector and can be transferred to AAC components where defined crack paths are required.
Tool Selection by Component Thickness and Connection Details
The optimal choice of tools depends on wall thickness, reinforcement content and the required edge quality.
- Thin, non-load-bearing walls: Manual demolition work, supported by small concrete demolition shear for connection areas.
- Medium wall thicknesses: Splitting technique via drilling patterns, followed by shear-based gripping and setting down of larger segments.
- Areas with steel content: Combination of concrete demolition shear, steel shear and, where applicable, Multi Cutters.
- Large components with preservation requirements for adjacent structures: Priority for hydraulic wedge splitter with gentle pressure build-up via hydraulic power pack.
Best Practices for Efficiency and Protection of the Substance
- Score joints and plaster layers before separating to avoid spalling.
- Preset fracture lines with drilling patterns and position splitting cylinders precisely.
- Build up forces in a metered way: increase the working pressure slowly at the hydraulic power pack for controlled crack guidance.
- Segment and set down components instead of bringing down large areas.
- Separate material streams early to simplify disposal and recycling.
Common Mistakes and How to Avoid Them
- Uncontrolled fractures caused by impact tools: avoid them; instead use splitting or shear techniques.
- Underestimating dust generation: missing wetting and compartmentalization increase health and cleanliness risks (dust protection, dust exposure).
- Overlooked connections: clarify hidden anchors, reinforcement or installation rails with detection and trial openings.
- Missing shoring: even light AAC walls can act as bracing; secure them temporarily.
Technical Key Parameters at a Glance
Typical guide values (to be verified for the project): bulk density classes around 0.35–0.70 kg/dm³; compressive strength often in the range of approx. 2–6 N/mm²; moisture content depending on use climate and building age. These parameters influence fracture pattern, dust generation and the selection of splitting forces and shear jaw pressure. The figures are non-binding and serve as a rough orientation for planning.
Quality Assurance and Documentation
Gapless documentation of deconstruction is helpful for evidence, billing and occupational safety. Photos of separation points, logs of dust and noise control measures, equipment logbooks of the hydraulic power pack, and proofs of clean material separation in disposal support transparency. Final visual checks of cut edges and adjacent structures conclude each work section.
Cut-Outs, Openings and Adjustments in Existing Structures
When creating new openings in AAC walls, a step-by-step approach is recommended: mark out, score from both sides, set a targeted drilling pattern and then split. Concrete demolition shear take over gripping and setting down of the segments, which improves edge quality and dimensional accuracy. Where steel beams, ring beams or installation rails intersect the opening, steel shear are additionally used.
Role of Special Equipment in the Project Environment
Various tasks often coincide on complex deconstruction sites. While AAC demolition is carried out with low-vibration splitting and shear techniques, tank cutters or tank cutting systems may be needed elsewhere, for example during tank dismantling in the same building. A coordinated equipment fleet enables parallel processing of different trades without impairing AAC demolition.