Autoclaved aerated concrete – also known as aerated concrete – is a mineral lightweight construction material with a fine, uniformly distributed pore structure. It combines low bulk density with good thermal insulation and enables precise, economical construction. In existing buildings and during deconstruction, autoclaved aerated concrete places specific demands on separating, opening, and disposal. Depending on component thickness and boundary conditions, tools such as concrete pulverizers as well as rock and concrete splitters are used, as applied in the fields of concrete demolition and special deconstruction as well as strip-out and cutting. The following sections consolidate practical knowledge, contextualize properties, and show how autoclaved aerated concrete can be processed safely and in a controlled manner.
Definition: What is meant by autoclaved aerated concrete
Autoclaved aerated concrete is a steam-cured, porous construction material on a mineral basis. Cement, lime, fine quartz sand, water, and a blowing agent (usually aluminum in very small quantities) form the starting materials. During production, numerous entrapped air pores are created by the gas-forming reaction. The green product is cured in autoclaves under saturated steam and high pressure. The result is a lightweight, compressive, and non-combustible construction material of building material class A1, used as masonry unit, plane element, or large-format wall panel element in load-bearing and non-load-bearing walls.
Material properties and characteristic values of autoclaved aerated concrete
The performance of autoclaved aerated concrete is largely determined by its pore structure. For planning, processing, and deconstruction, the following characteristic values are decisive:
Bulk density and compressive strength
Typical bulk densities are in the range of about 300 to 700 kg/m³. Compressive strength classes often range around 2 to 6 N/mm². This makes autoclaved aerated concrete significantly lighter and less compressive than normal concrete—an aspect that influences the choice of tools during demolition.
Thermal and moisture behavior
Thermal conductivity, depending on bulk density, is approximately 0.07 to 0.16 W/(m·K). Autoclaved aerated concrete is vapor-permeable and capillary-active, can buffer moisture, and contributes to a balanced indoor climate. Persistent moisture penetration should nevertheless be avoided.
Fire protection and sound insulation
As a non-combustible construction material (A1), autoclaved aerated concrete provides very high fire protection. In terms of building acoustics, sound insulation depends on surface mass; massive systems or facing layers improve the sound reduction index.
Workability
Autoclaved aerated concrete can be sawn, milled, drilled, and sanded. This good workability facilitates both the creation of installation chases and the later deconstruction, but requires low-dust working and suitable extraction or wetting measures.
Manufacturing and composition
The starting point is mineral raw materials (quartz sand, lime/cement) and water. The finely ground mixture is homogenized with the blowing agent, poured into molds, and expands there into a green block. After stiffening, the blocks are cut automatically and cured in the autoclave under steam. The microfine pore structure is created in a controlled manner and ensures the favorable relationship between strength, weight, and thermal insulation. Reinforced elements (e.g., floor or wall panels, lintels) additionally contain corrosion-protected steel reinforcement.
Formats, applications, and typical components
Autoclaved aerated concrete is supplied as masonry units, large-format plane elements, U-shaped units, or as reinforced components. Typical applications are exterior walls with monolithic thermal insulation, load-bearing and non-load-bearing interior walls, and details optimized for thermal bridges. Thin-bed mortar ensures very narrow joints and precise geometries. In existing buildings, autoclaved aerated concrete is frequently encountered as a partition wall, as a bracing interior wall, or as a monolithic exterior wall.
Planning in existing buildings: openings, breakthroughs, and adjustments
Changes in existing buildings often concern door openings, service penetrations, recesses, and partial demolitions. Due to the low tensile strength, clean load redistribution and temporary shoring are important. Before intervening, load-bearing function, any reinforcement (e.g., in lintels), and connection details must be clarified. Controlled, low-vibration working methods are particularly advantageous in occupied buildings, hospitals, or sensitive production areas.
Separating and opening autoclaved aerated concrete: tools and procedures
Hand saws and powered saws with extraction are suitable for precise cuts. In deconstruction, selective demolition, and strip-out, methods that work low-vibration and low-noise are preferred. Depending on component thickness, reinforcement content, and the site environment, concrete pulverizers as well as rock and concrete splitters are particularly used.
Concrete pulverizers in autoclaved aerated concrete deconstruction
Concrete pulverizers produce controlled crushing by hydraulic compressive forces at the component edge or within the component zone. In autoclaved aerated concrete this allows you to:
- Bite off wall segments piece by piece without introducing impact energy,
- predefine edges to create intentional fracture lines,
- open reinforced areas (e.g., lintels) when the reinforcement is then separated separately.
Advantages include low vibration, good controllability, and the ability to work in confined interior spaces—a plus in the fields of strip-out and cutting as well as concrete demolition and special deconstruction.
Rock and concrete splitters for controlled crack formation
Hydraulic rock and concrete splitters act via wedges inserted in predrilled holes and fracture the component by tensile stresses. Autoclaved aerated concrete, whose tensile strength is comparatively low, can thus be separated very controllably. The method is low in vibration and suitable for sensitive environments.
- Drill holes in a defined grid (adapt diameter and depth to component thickness).
- Insert splitting cylinders and gradually increase pressure until cracks connect.
- Remove elements, separate by type, and size them for transport.
The method is suitable for thicker wall panels, massive nodes, or openings where clean fracture lines are required. In areas with reinforcement, after splitting the exposed reinforcement is cut with suitable cutting tools.
Handling reinforcement and embedded parts
In reinforced autoclaved aerated concrete elements (lintels, panels) as well as at connections, steel parts, anchors, rails, or brackets occur. After opening the component, these are cleanly cut with steel shears or multi cutters. With increasing material thicknesses or composite components (autoclaved aerated concrete with reinforced bearing concrete), concrete pulverizers for the concrete matrix and steel shears for the metal parts are a practical combination. The hydraulic energy supply is provided by suitable hydraulic power packs whose pressure and flow rate are matched to the respective tool.
Selective deconstruction: sorting and recycling
Autoclaved aerated concrete can often be collected by material type. This facilitates onward transport and recovery, for example as a mineral aggregate in construction materials or as backfill in accordance with regional requirements. Early separation of metal (reinforcement, embedded parts) using steel shears and piece-by-piece sizing with concrete pulverizers improve recycling quality. When using rock and concrete splitters, defined fragments with low fines are produced.
Emissions, dust, and vibration management
Sawing, milling, and crushing autoclaved aerated concrete generates mineral dust. Since autoclaved aerated concrete contains quartz fractions, a low-dust working method is important. Proven measures include:
- Extraction technology on drilling and cutting tools,
- targeted water wetting where possible,
- shielded work areas and controlled airflow,
- low-vibration methods with concrete pulverizers or rock and concrete splitters instead of percussive tools.
This minimizes dust emissions, noise, and vibrations—an advantage in sensitive environments and a contribution to occupational safety. Legal requirements and limit values must be checked for each project; the following notes are general in nature and not legally binding.
Typical use cases in existing buildings
- Creating new door and window openings in non-load-bearing autoclaved aerated concrete walls: score or pre-saw, then controlled bite-off with concrete pulverizers.
- Deconstruction of large-format wall panels: grid drilling and splitting with rock and concrete splitters, then remove by material type.
- Exposing installation zones: low-dust cutting; localized bite-off along predetermined fracture lines.
- Removing reinforced lintels: pulverizer first for the concrete matrix, then cut reinforcement with steel shears or multi cutters.
- Working in sensitive areas (special deployment): low-noise and low-vibration removal techniques with hydraulic tools, supplied by quiet hydraulic power packs.
Workflow and best practices
- Investigation and planning: record component thickness, reinforcement, services, connections; clarify load redistribution.
- Method selection: saw rather thin, unreinforced components; open or split massive or partially reinforced areas with concrete pulverizers.
- Preparation: protect surroundings, dust and noise protection, provide extraction and wetting technology.
- Execution: start with low pressure stages, control feed, continuously observe fracture behavior.
- Material separation: separate metals immediately; collect autoclaved aerated concrete by material type.
- Documentation: record procedures, material flows, and disposal routes in a traceable manner.
Limits and particularities
Autoclaved aerated concrete is brittle and has low tensile strength. Uncontrolled impact loading can lead to spalling and dust-intensive destruction. Reinforced hybrid areas (e.g., bearings or subsequently grouted connections) require suitable combinations of concrete pulverizers, rock and concrete splitters, and steel cutting tools. For very thin walls, a saw-focused approach is often recommended to avoid unnecessary fracture formation.
Quality assurance, equipment, and power supply
For reproducible results, carefully maintained tools and correctly adjusted hydraulic power packs are crucial. These include:
- regular functional and leak tests,
- correct hydraulic oil, filter, and hose management,
- pressure- and flow-rate matching between power pack and tool,
- documented operator instruction.
Clear separation of work zones and communication pathways on site increase safety and speed, particularly during strip-out and cutting while operations continue.
Legal and organizational notes
Compliance with the relevant standards and codes of practice, official requirements, and occupational and environmental protection regulations must be examined on a project-specific basis. These notes are general and do not replace binding advice. For work on load-bearing components, the structural situation must be assessed in advance; temporary shoring must be provided professionally where required.