Plastic formwork refers to formwork systems in which the formwork sheathing or panels consist predominantly of polymer materials. They are used in concrete construction for smooth surface finishes, low water absorption, and reproducible geometry. For deconstruction, this knowledge is relevant: The properties of plastic formwork influence the concrete’s strength, crack pattern, and edge quality—and thus the choice of working methods and tools, for example when using concrete demolition shears or hydraulic splitters such as hydraulic rock and concrete splitters in concrete demolition and special deconstruction by Darda GmbH.
Definition: What is meant by plastic formwork
Plastic formwork means formwork with a sheathing or solid panels made of polymers (e.g., PP, HD-PE, ABS) or fiber-reinforced plastics (GFRP/CFRP). These systems are available as modular panels, as replaceable formwork sheathing on frames (wood, steel, aluminum), as well as lost formwork. The objective is dimensionally accurate shaping, a homogeneous architectural-concrete appearance, and reduced moisture uptake of the sheathing. Plastic formwork can be reused multiple times; the number of possible reuses depends on the material, loading, cleaning, and storage.
Structure, materials, and system types of plastic formwork
Plastic formwork differs by material, composite, and application. Common are:
- Solid-plastic panels made of PP or HD-PE for light to medium loads, often ribbed for stiffening.
- Fiber-reinforced formwork sheathing (GFRP) on support frames, suitable for higher fresh concrete pressures and precise architectural-concrete surfaces.
- Hybrid solutions with plastic formwork sheathing on aluminum or steel frames for modular wall formwork.
- Lost plastic formwork as stay-in-place elements (e.g., ring formwork, corrugated profiles, void former systems) that remain in the component.
- Special forms such as plastic formwork tubes for columns or textured matrices to create relief surfaces.
Material parameters such as modulus of elasticity, temperature behavior, and creep tendency determine permissible fresh concrete pressures and the required shoring. In tunnel construction and special deployments, fiber-reinforced systems are used when corrosion resistance and dimensional stability are the priorities.
Properties and performance characteristics
The following features are crucial for planning and deconstruction:
- Surface appearance: smooth, low-porosity concrete surfaces; well suited for architectural concrete with low grain pattern.
- Moisture uptake: lower than wood; reduced risk of drawing mixing water.
- Temperature and creep behavior: temperature-dependent stiffness; observing operating intervals (e.g., −10 to +40 °C) is advisable.
- Resistance: resistant to many release agents; mechanical damage (notches, scratches) affects the surface appearance.
- Cleaning: usually requires little effort; hard particles can scratch the sheathing.
- Reusability: depends on system and care; performance values vary and should be documented project-specifically.
Influence on concrete surfaces and architectural concrete
Plastic formwork yields homogeneous, often very smooth surfaces. Pore formation depends on concrete composition, compaction, and release agent. Texture matrices create defined reliefs, which can influence the fracture line at edges during later deconstruction. In areas where concrete demolition shears will engage, sharp-edged, dense surfaces are advantageous because demolition edges can be initiated more controllably. With lost formwork, plastic parts remain in the component—this must be considered when selecting the demolition method and planning waste separation.
Relevance for deconstruction, concrete demolition, and special demolition
The type of formwork affects the choice of demolition strategy. Components formed with plastic formwork often have dense edge zones and precise geometries. This supports controlled removal strategies with low vibration, for example when working with concrete demolition shears or during hydraulic splitting using stone and concrete splitting devices by Darda GmbH. In sensitive areas (hospitals, laboratories, occupied buildings), a low-vibration approach helps protect adjacent elements.
Procedure with concrete demolition shears
For walls and slabs with smooth surfaces, concrete demolition shears can engage along edges and openings. The smooth, dense skin increases the stability of the first bites; afterward the tool works through the reinforcement matrix. It is important to identify spacers and remaining plastic parts so the cutting sequence can be adapted. With structured surfaces, the first engagement point should be chosen to prevent uncontrolled breakout of the texture.
Hydraulic splitting in the context of plastic formwork
Hydraulic splitters act via boreholes. With dense edge zones from plastic formwork, crack paths can be predicted well when hole spacing and depth match the component cross-section. Combining pre-cracking by splitting with subsequent targeted removal using concrete demolition shears reduces noise, dust, and secondary damage.
Gutting works and cutting
During gutting works, remaining plastic parts in the structure (lost formwork, spacers, anchor cones) can influence saw blade and tool behavior. For clean separation, metal inserts (reinforcement, embedded parts) are cut with suitable cutting tools such as high-precision multi cutters or steel shears before concrete demolition shears or splitting techniques release the concrete. In tanks and shafts with plastic liners, sparks and emissions must be minimized; a step-by-step approach with hydraulic tools can be effective here.
Typical details and connection points
Details relevant to planning, construction, and deconstruction:
- Formwork ties and cones: plastic or fiber composite cones can remain in the component; this affects the waste fraction during demolition.
- Spacers: made of plastic, fiber concrete, or composite materials; distribution along edges is relevant for choosing the bite points of the concrete demolition shears.
- Waterstops and sealing profiles: elastomeric or thermoplastic inserts at construction and expansion joints; they alter crack propagation.
- Surface matrices: reliefs locally redirect stresses; when splitting, the borehole grid should be matched to them.
Planning, quality assurance, and post-treatment
For consistent quality, the following is recommended:
- Apply release agents sparingly and system-compatibly; overdosing causes pores and lowers pull-off bond values.
- Control consolidation at the formwork sheathing; especially with smooth plastic surfaces avoid voids.
- Observe the temperature of the sheathing to prevent creep effects; stage concreting under high pressures.
- Document sheathing condition, cleaning methods, and number of reuses for later assessments during deconstruction.
Safety and environmental notes
Deconstructing components with plastic formwork produces mixed fractions (concrete, reinforcing steel, plastics). Separation by material type reduces disposal costs and environmental impact. Dust and noise protection must be planned organizationally; hydraulic methods with concrete demolition shears and hydraulic splitters can reduce emissions. Legal requirements for waste regulations, occupational safety, and noise are location-dependent; the information provided is general in nature and does not replace a case-by-case assessment.
Practical relevance to application areas
In the application areas of Darda GmbH, the relevance of plastic formwork is particularly evident:
- Concrete demolition and special demolition: Smooth edge zones facilitate controlled removal sequences with concrete demolition shears; pre-cracking by splitting reduces cross-sections for haulage.
- Gutting works and cutting: Lost formwork and plastic inserts require an adapted cutting sequence; separate metals, secure plastic parts, then release the concrete.
- Rock excavation and tunnel construction: Lining components and secondary linings with GFRP sheathing provide dense surfaces; splitting techniques and concrete demolition shears work with low vibration in sensitive tunnel areas.
- Natural stone extraction: Indirect relevance for concrete foundations of plants; knowing the formwork type helps when removing machine foundations.
- Special deployments: Components with remaining plastic elements in corrosion-critical environments require precise material separation during deconstruction.
Checklist: selection and evaluation in the project
For planning and deconstruction decisions regarding plastic formwork, the following questions are helpful:
- Which formwork type is present (solid plastic, GFRP sheathing, lost)?
- Which surface quality and edge-zone density are expected (architectural concrete, relief)?
- Where are the tie locations, spacers, sealing profiles?
- Which borehole grids are suitable for hydraulic splitting to control crack paths?
- Where can concrete demolition shears engage safely and gently (edges, openings, supports)?
- Which waste fractions will be produced and how will they be separated?
- Which emission limits apply at the site and which work steps minimize noise and dust?
Key figures and technical notes
Since systems vary, project-specific data are decisive. Benchmark values:
- Fresh concrete pressure: depends on temperature, casting rate, and system stiffness; in practice, limits are specified by the system supplier.
- Temperature range: many plastic formwork systems operate reliably in moderate temperature ranges; extreme cold or heat affects the modulus of elasticity and thus deflection.
- Reuses: from a few up to several dozen uses are possible; cleaning and storage determine the surface quality of the subsequent element.
- Drillability and crack control during splitting: dense, smooth edge zones allow well-plannable cracks; hole diameter, depth, and spacing must match cross-section and reinforcement.
Application notes for tool selection in deconstruction
For a material- and environment-friendly approach, the following sequences have proven effective:
- Define edges: deliberately notch architectural-concrete edges or matrix borders with concrete demolition shears.
- Pre-cracking: split massive components via borehole rows to crack along planned lines using hydraulic splitters.
- Separate inserts: separate reinforcement steels, embedded parts, and plates with suitable cutting tools.
- Material purity: place plastic residues, concrete rubble, and steel separately; simplify subsequent disposal.
The combination of controlled splitting and precise removal with concrete demolition shears ensures low vibration and predictable fracture behavior—especially for components produced with plastic formwork.