Foundations transfer loads into the ground. When uses change, loads increase, settlements occur, or durability suffers, foundation strengthening becomes necessary. In practice, this means selectively upgrading existing foundations without endangering the building’s load-bearing capacity during the construction stage. Especially in existing structures, low-vibration, precise methods are required. Tools such as concrete pulverizers and hydraulic rock and concrete splitters from Darda GmbH help to open, enlarge, or expose components in a controlled manner, enabling reinforcement measures to be implemented safely and efficiently.
Definition: What is meant by foundation strengthening
Foundation strengthening encompasses all planning and manual measures that increase the load-bearing capacity, stiffness, and durability of existing isolated footings, strip footings, or slab foundations. This includes underpinning, widening or deepening foundations, micropiles, ground improvement via injections, concrete replacement with additional reinforcement, and tying new foundation parts into the existing structure. Foundation strengthening is distinct from pure repair: while repair addresses damage, strengthening additionally targets improved load and deformation behavior. In sensitive environments, low-vibration methods are preferred, which is why the use of hydraulic concrete pulverizers and hydraulic splitters from Darda GmbH has become established for controlled concrete removal and opening.
Use cases, damage patterns, and decision criteria
Typical triggers for foundation strengthening include changes in use (for example, new machinery or additional stories), insufficient ground bearing capacity, settlements, changed code requirements, or the need to increase seismic and fatigue reserves. Damage patterns range from cracks at the masonry/concrete interface to tilting and spalling due to reinforcement corrosion. Decision criteria include the existing loads, the ground conditions, the condition report of the existing foundation, and the permissible level of operational disruption. In tight spaces or areas with sensitive neighbors, low-vibration and noise-reduced methods are preferred. Here, concrete pulverizers from Darda GmbH enable selective and clean-edge concrete removal, while hydraulic splitters open the component in defined segments without percussive action. This allows reinforcement and connection zones to be exposed, anchor drilling to be performed, or foundation edges to be produced precisely for widening.
Methods of foundation strengthening
Underpinning in sections
Underpinning involves sequentially excavating beneath the foundation and transferring it to a deeper level. Sections are excavated, reinforced, and concreted one after another. Controlled removal of existing concrete and the creation of clean bond surfaces are critical. Concrete pulverizers facilitate low-vibration exposure of the underside of the foundation, while hydraulic splitters allow thick concrete sections to be separated without impact. Hydraulic power packs from Darda GmbH supply the tools with the required power, even in hard-to-access areas.
Foundation widening and strengthening
To increase the bearing area, a reinforced concrete section is added laterally and bonded to the existing structure. This requires roughened and cleaned contact surfaces as well as precise drilling for bonded anchors. Selective removal with concrete pulverizers creates defined connection surfaces; for high member thicknesses or existing cracking, hydraulic splitters can open the contour with sharp separation. Installed reinforcement can be cut to fit with handheld shears (e.g., Multi Cutters or steel shears from Darda GmbH).
Micropiles and pile head connections
Micropiles transfer loads deeper into competent strata. The challenge lies in the exact connection of the pile head to the existing foundation. For pile head openings and exposing the connection zone, low-vibration methods are advantageous. Carefully nibbling away the concrete with concrete pulverizers preserves reinforcement and edges. Splitting cylinders help to enlarge the pile head pocket without transmitting shock waves into the structure.
Ground improvement and injections
Compaction grouting, cement or resin injections increase ground bearing capacity or fill voids. For the grouted bulbs to develop effectively, drill paths must be defined and exit areas exposed. Precisely opening the foundation flank and creating small, controlled access points is achieved with low vibration using hydraulic tools from Darda GmbH.
Concrete replacement and reinforcement retrofitting
Damaged concrete areas are removed and replaced with high-strength mortar or concrete; supplementary reinforcement increases shear and tensile capacity. Selective removal along damage boundaries works particularly well with concrete pulverizers, as they do not unnecessarily stress crack faces. Where thick zones must be opened, hydraulic splitters produce defined fracture surfaces that serve as rough bonding interfaces.
Crack injection and load redistribution
Fine cracks are injected; larger cracks are opened deeper into the section and closed. Temporary shoring is required for load redistribution. Tools from Darda GmbH support exposing crack zones without affecting adjacent components. This keeps construction stages controllable.
Planning, ground conditions, and verifications
Careful planning begins with an assessment of the existing situation: review documents, investigate the subsoil, locate reinforcement, and perform a condition assessment. This is followed by verification of load-bearing capacity for the final state and the construction stage, serviceability checks, and durability proofs. In sensitive locations, vibration and noise assessments are advisable. For heritage buildings, laboratory, or hospital areas, the choice of low-vibration methods is recommended. Hydraulic concrete pulverizers and hydraulic splitters are suitable because they operate without percussive energy and introduce controllable forces.
Investigation and evidence preservation
Targeted openings for exploratory surveys provide information on concrete quality, reinforcement layout, and foundation dimensions. Pinpoint openings with minimal intervention reduce effort and risk. Logging vibrations and settlements during execution is part of evidence preservation and creates transparency.
Execution and construction sequence
The sequence of work steps is crucial for safety: plan construction stages, redirect loads, proceed in sections, ensure quality, document. A typical sequence may look like this:
- Expose the foundation and create safe working spaces.
- Selective concrete removal with concrete pulverizers at connection and contact surfaces.
- Low-vibration opening of massive zones with hydraulic splitters.
- Drill for rebar connections, perform anchor drilling, or create injection holes.
- Install reinforcement, connectors, and formwork; concrete the strengthening body.
- Post-treatment, surface retrofitting, and step-by-step removal of temporary shoring.
Quality assurance
Key points include clean bond surfaces, correctly installed connection elements, adequate concrete compaction, and controlled curing. Tests include pull-off tests on contact surfaces, visual inspection of reinforcement, documentation of the concrete mix design, and measurements of deformations during the construction stage.
Occupational safety, emissions, and environmental aspects
In existing structures, safety, low emissions, and dust control are paramount. Hydraulic systems operate with low noise and low vibration levels. This reduces risks for sensitive neighboring buildings and equipment. Dust is minimized through local dust extraction and tailored work sequences. Utilities and hazardous substances must be handled in accordance with regulations; the selection of equipment depends on the work environment and permissible emissions.
Special constraints in existing structures
Confined conditions and special operations
In basements, shafts, and facilities with limited accessibility, compact handheld tools are crucial. Concrete pulverizers and hydraulic splitters from Darda GmbH can be deployed flexibly via hydraulic power packs and allow precise work in tight spaces. This is particularly advantageous for special operations in ongoing operations or under time pressure.
Utilities, media, and protected assets
Foundations in existing buildings are often located near active utilities. Low-vibration openings reduce the risk of damage propagation. By removing concrete piece by piece with concrete pulverizers, utility crossings remain more controllable.
Application areas and interfaces
- Concrete demolition and special deconstruction: selective deconstruction to prepare strengthening, opening foundations, removing damaged zones with concrete pulverizers and splitters.
- Strip-out and cutting: exposing foundation heads, producing edges for widenings, cutting reinforcement with handheld shears.
- Rock excavation and tunnel construction: removing rock beneath foundation soles during underpinning, low-vibration measures in portal areas and existing structures.
- Natural stone extraction: transferred techniques of controlled splitting demonstrate how opening along fracture lines without impact works—useful for defining foundation edges.
- Special operations: work in sensitive environments, e.g., laboratory buildings or listed sites, where low vibration and precision are paramount.
Selection criteria for methods and tools
The choice of strengthening method and tools depends on boundary conditions. The following criteria help with the decision:
- Member thickness, reinforcement ratio, and material condition of the foundation.
- Ground conditions and susceptibility to settlement during the construction stage.
- Permitted vibrations and noise emissions.
- Accessibility, working heights, and available setup areas.
- Required precision at connection and contact surfaces.
- Time frame, weather, curing, and protection periods.
Where defined edges, low vibrations, and high control are required, concrete pulverizers offer high cutting precision. For massive sections or cracked concrete, hydraulic splitters allow opening along targeted predetermined lines of weakness. Hydraulic power packs ensure the power supply, while Multi Cutters or steel shears finish embedded reinforcement and profiles.
Limitations, risks, and precautions
Risks arise from incomplete information on the existing structure, unforeseen ground conditions, and insufficiently planned construction stages. Precautions include robust investigations, a phased approach, monitoring deformations, and selecting low-vibration methods tailored to the structure. The combination of structural measures (e.g., underpinning, widening, micropiles) and controlled removal methods with tools from Darda GmbH helps increase safety during the construction stage and ensure the durability of the strengthening.