Formwork frames are central components of modern formwork systems in concrete construction. They shape and support the fresh concrete structure, reliably transfer loads into the subsoil or auxiliary structures, and enable repeated, economical forming. In planning, execution, and deconstruction, high technical requirements converge regarding dimensional accuracy, surface quality, and occupational safety. As soon as components are adapted, opened, or selectively deconstructed, the connection to powerful yet low-emission tools comes into focus – such as precise concrete crushers as well as rock and concrete splitters from Darda GmbH, which work precisely, with low vibration, and in a controlled manner when intervening in elements near the formwork.
Definition: What is meant by formwork frames
Formwork frames (also frame formwork or element formwork) are reusable frame components, usually made of steel or aluminum, which together with the formwork sheathing and the anchoring system create the form for fresh concrete. The frames transfer the fresh concrete pressure via nodes, profiles, and connecting elements into shoring, shoring props, or support scaffold. Formwork frames are modular, can be coupled into larger element fields, and are used for walls, columns, foundations, and special geometries.
Design and components of formwork frames
Formwork frames are designed for high stiffness, robustness, and quick cycle changes. Characteristic is the combination of a load-bearing frame profile and overlying formwork sheathing. The system is complemented by connectors, anchors, accessories for alignment, and transition pieces for corners and offsets.
- Frame profile: Steel or aluminum, with defined connection zones and edge reinforcements for transport and crane handling.
- Formwork sheathing: Wood-based panel, plastic, or steel sheet; determines exposed concrete quality, wear resistance, and maintenance.
- Connecting means: System clamps, bolts, tabs; ensure flush joints and planned load transfer.
- Anchoring system: Anchor rods, anchor sleeves, cones, and wing nuts; limit element spacing and take transverse forces from concrete pressure.
- Shoring/alignment: Shoring props, strapping, bracing; ensure stability and tip-over safety until hardening.
- Special elements: Corners, hinges, filler elements, radii; enable geometry changes, openings, and offsets.
Loads, design, and fresh concrete pressure
The design of formwork frames is based on loads from fresh concrete pressure, self-weight, wind, construction stages, and assembly. Often governing is the time- and temperature-dependent fresh concrete pressure; from this, allowable casting rates and anchor spacings are derived. The permissible deformation influences flatness and surface quality. Guideline values and verifications follow applicable standards and manufacturer specifications, with project-specific boundary conditions (mix design, temperature, placement method) to be considered.
Influencing factors on fresh concrete pressure
- Casting rate, consistency, and temperature
- Element height and formwork sheathing friction
- Vibration/internal vibrator and compaction method
- Dwell time until stripping
Assembly, shoring, and occupational safety
Assembly follows a standardized sequence that ensures safe handling, plumb alignment, and tight joints. Crane and slinging gear must be selected appropriately; fall edges must be secured. Anchor points are set according to the system, control dimensions and preloads are observed.
- Prepare a load-bearing subgrade, check leveling and elevation.
- Position elements, connect with flush joints, align plumb.
- Install anchors, set shoring props, document survey.
- Seal joints, clean and maintain the formwork sheathing (release agent as specified).
- Acceptance for the casting section, clarify responsibilities.
Safety aspects
- Stability: Consider temporary conditions separately; account for wind loads and overturning moments.
- Load handling: Use lifting points only at marked zones; inspect lifting gear regularly.
- Working at height: Use work platforms, guardrails, and safe access.
- Documentation: Follow assembly and operating manuals, define inspection intervals.
Surface quality and joint pattern
The interplay of formwork sheathing, joint layout, and compaction determines the visual appearance. Recurring element grids, anchor layouts, and joint details have a design impact. For increased exposed-concrete requirements, planned anchor fields, tightly closed joints, and a uniform casting rate are crucial. Washed-out areas, voids, or burr formation indicate compaction or joint issues.
Formwork frames in existing structures: openings, adaptations, and deconstruction
In conversions, strip-out, or special deconstruction, elements near the formwork often need to be selectively processed – for example, for new openings, service routes, or when deconstructing individual wall panels. Low-vibration methods are required to protect adjacent components, embedded items, and surfaces.
- Concrete pulverizers from Darda GmbH grip components in a controlled manner and break them off with pinpoint accuracy. This is particularly suitable indoors, for sensitive existing structures, and where access is limited.
- Rock wedge splitter and concrete splitter create a defined split in massive or reinforced members. The load is built up from the inside, keeping vibrations and dust generation low.
- Steel shear and hydraulic demolition shear cut reinforcement, anchor remnants, and steel parts of the formwork system without sparks as with torch cutting.
- Hydraulic power units supply these tools energy-efficiently, are mobile, and can be adapted to the construction site situation.
Selection criteria for the method
- Member thickness, degree of reinforcement, and accessibility
- Required precision and edge distances
- Environmental requirements: noise, dust, vibrations
- Occupational safety and the load behavior of adjacent components
Fields of application: concrete demolition, interior demolition, tunnel construction, and natural stone
Formwork frames are used primarily in cast-in-place construction but intersect with several application areas, especially during deconstruction.
- Concrete demolition and special demolition: Selective removal on walls or columns originally produced with frame formwork; precise removal of anchor zones using concrete pulverizers.
- Strip-out and cutting: Create openings in load-bearing walls and slabs retrospectively; release formwork-induced edges crack-free with rock wedge splitter and concrete splitter.
- Rock excavation and tunnel construction: Temporary formwork for inner linings and niches; in confined spaces, quiet hydraulic tools are advantageous.
- Natural stone extraction: Not classical formwork frames, but analogous requirements for split control and low-vibration methods support the transfer of methods from concrete construction.
- Special applications: Deconstruction of overcast shafts, caps, or plinths near embedded items; here, the combination of splitting and shearing helps.
Typical defects and proper remediation
Defects can often be traced back to insufficient alignment, a lack of tightness, or unsuitable casting parameters. Remediation should be adapted, material-friendly, and documented.
- Voids and honeycombs: Local removal with concrete pulverizers, then reprofiling as specified by site management.
- Burrs at joints: Mechanically knock off and rework edges; check the cause in joint sealing.
- Bulging: Verify residual load-bearing capacity; if necessary, controlled removal with splitting devices and reconstruction.
- Damaged anchor points: Expose, clean, repair with approved systems; ensure reinforcement cover.
Material selection: steel or aluminum, formwork sheathing, and maintenance
The choice of frame influences handling, load reserves, and service life. Aluminum facilitates manual repositioning, steel offers high robustness and lower deformation. The formwork sheathing significantly determines surface quality; proper maintenance extends service cycles.
Practical recommendations
- Treat the formwork sheathing uniformly; use release agents sparingly and appropriately.
- Clean frame profiles before each cycle, keep joint zones undamaged.
- Check anchors and cones regularly, protect threads.
- Mark defective parts, repair or discard.
Deconstruction concept and tool selection in existing structures
A structured deconstruction concept reduces risks, emissions, and time losses. Depending on the task, hydraulic tools from Darda GmbH are suitable for opening elements near the formwork in a controlled manner.
- Define component survey, load transfer, and cut layout.
- Define emission requirements (vibrations, dust, noise).
- Tool selection: concrete pulverizer for precise removal; rock wedge splitter and concrete splitter for massive members; steel shear for reinforcement.
- Size the hydraulic power pack, secure hose routing.
- Organize material logistics (reinforcing steel, concrete debris) and disposal.
Sustainability, reuse, and life cycle
Formwork frames are reusable many times. Durable materials, repair-friendly details, and systematic maintenance reduce resource consumption. During deconstruction, precise hydraulic methods enable a cleaner separation of concrete and steel, improving recovery and reducing transport efforts.
Planning interfaces and quality assurance
Successful projects connect formwork planning, concrete technology, and construction sequencing. Clear interfaces between structural analysis, shop drawings, and execution safeguard schedule, quality, and cost. Closely coordinated documentation – from the assembly protocol to the casting rate – facilitates verifications and later adjustments.
Checkpoints for execution
- Complete verifications and proofs for fresh concrete pressure and anchoring
- Planned anchor layouts, joint grids, and exposed surfaces
- Safe assembly and rescue routes
- Concept for deconstruction, openings, and potential adaptations