Injection resins are a central tool of concrete repair and structural waterproofing. They are used to permanently grout, seal, or consolidate cracks, joints, and voids in concrete, masonry, or rock. Especially in combination with mechanical deconstruction and separation/cutting methods — such as the use of a concrete demolition shear or hydraulic rock and concrete splitters — they enable controlled, safe, and predictable workflows: water ingress can be stopped, structural elements temporarily stabilized, and edge areas secured against spalling. This creates a reliable basis for concrete demolition and special deconstruction, building gutting and cutting, rock breakout and Tunnel construction, natural stone extraction, as well as special operations where safety and precision take priority.
Definition: What is meant by injection resin
Injection resins are reactive, low- to medium-viscosity resin systems — typically based on polyurethane (PU), epoxy (EP), acrylate gel, or silicate — that are introduced into cracks, joints, pores, or voids via packers and a pump. After placement, the components react chemically and cure into a sealing, bonding, or consolidating structure. The objective is either the restoration of watertightness against hydrostatic and non-hydrostatic water, the increase in load-bearing capacity through bonded load transfer, or the consolidation of the substrate in permeable or cracked zones. Depending on the system, rigid, tough, or elastic end products are formed with specific properties in terms of pull-off adhesion, elongation capacity, hydrolysis resistance, and temperature behavior.
Application fields and interfaces with demolition technology
Injection resins directly intervene in the preparation or accompaniment of mechanical methods in many construction workflows. Where a concrete demolition shear or rock and concrete splitters are used, crack injection, joint rehabilitation, and void filling can secure work areas, control moisture ingress, and locally improve the structural bond. This makes dismantling and separation/cutting operations more predictable, can reduce emissions, and minimizes risks from uncontrolled fracture formation.
Concrete demolition and special demolition
Before gripping or shearing components, targeted crack injection enables the temporary stabilization of spalled areas, the sealing of water-bearing cracks, and the filling of voids that might otherwise yield uncontrollably during demolition. In sequenced demolition, sealed construction and expansion joints help create low-water conditions; this allows the concrete demolition shear to be positioned more precisely. Likewise, bonding separation cracks with rigid systems can improve load transfer until controlled dismantling takes place.
Building gutting and cutting
During sawing, drilling, and cutting in existing concrete, water-reactive injection resins prevent the washout of fines and seal cracks against cooling water and groundwater. This reduces water outflow into building areas already cleared during gutting. In front of anchor or bearing points for a lifting device, local void filling can improve load transfer until the component is removed with a concrete demolition shear or a hydraulic demolition shear.
Rock breakout and tunnel construction
In fractured rock, injections serve to consolidate jointed zones and to seal against water-bearing layers. Before controlled splitting with rock and concrete splitters, pre-injection lowers the risk of uncontrolled solution fractures, reduces water ingress into the work area, and enables targeted load decoupling. In tunnel headings and caverns, acrylate gels are often used for temporary curtain sealing so that subsequent mechanical separation and splitting operations can be carried out safely.
Natural stone extraction
With sensitive natural stones, near-edge consolidation of microcracks can limit spalling on exposed faces during the splitting process. Hollow zones behind bed joints can also be filled to make load introduction more uniform when placing splitting cylinders.
Special operations
In damage events — such as leaks in water-bearing structures or underground utility rooms — fast-reacting PU systems enable the rapid interruption of water ingress. This creates conditions under which hydraulic demolition equipment can be used in a controlled manner without other parts of the structure being adversely affected by uncontrolled water.
Material types and properties
The choice of injection resin depends on the objective, substrate, moisture content, crack width, and temperature. Important categories are:
- Polyurethane resins (PU): Water-reactive (single- or two-component), foaming or non-foaming. Suitable for sealing water-bearing cracks, even with strong inflow. Elastic or tough-elastic end products, good crack-bridging.
- Epoxy resins (EP): High pull-off and compressive strengths, mostly rigid. For bonded connections of dry to slightly damp cracks for structural consolidation.
- Acrylate gels: Very low viscosity, excellent penetration, adjustable gel time, high flexibility. For curtain sealing, construction and expansion joints with movement accommodation.
- Silicate and microcement systems: Mineral alternatives for soil or rock consolidation and for void filling; temperature-resistant, compatible with mineral substrates.
Decisive parameters include viscosity (penetration capability), reaction time or pot life (working window), final elasticity (movement accommodation), and chemical resistance. Moisture and temperature significantly influence both reaction and adhesion.
Injection technology: methods and parameters
Proper execution determines the success of the measure. A systematic approach includes:
Survey and objective definition
Crack mapping, moisture testing, assessment of crack causes (e.g., shrinkage, settlement, dynamic effects), measurement of crack widths, and inspection of water flow. Clarify whether sealing, bonded structural repair, or consolidation is targeted.
Drilling pattern, packers, and sealing
Define drilling angles and spacing depending on crack path and component thickness. Select suitable packers (mechanical or adhesive packers) with an appropriate sealing range. Cracks and joints must be surface-sealed to achieve controlled filling.
Pumping technology and pressure ranges
Low-pressure injection for fine cracks and sensitive areas; higher pressures for deeper voids and dense matrices, always while observing the structural behavior. The injection pressure is based on member thickness, objective, and material; it must be selected so that no widening or secondary cracking occurs.
Mixing technique, pot life, and reaction control
Exact component mixing ratio is crucial. Short pot lives require swift work; longer gel times enable better penetration. Logged pre-trials help adapt material behavior and reaction times to site conditions.
Quality assurance and documentation
Track resin egress across packer rows, control material quantity per packer, and record pressure, time, and temperature. Final checks (e.g., tapping, endoscopy, moisture measurement) demonstrate fill level and tightness.
Interfaces with rock and concrete splitters and a concrete demolition shear
The combination of injection technology and mechanical separation opens pragmatic solutions in complex existing structures:
- Water control prior to demolition: Sealing water-bearing cracks creates dry attack points for the concrete demolition shear and reduces contamination and hazards.
- Edge stabilization: Local consolidation minimizes spalling when forces are introduced pointwise.
- Void filling: Prevents sudden yielding behind facings or in shells, which facilitates gripping and controlled splitting.
- Temporary securing: Short-term elastic systems bridge movements until final removal of elements with rock and concrete splitters.
The coordinated sequence is important: first seal or consolidate, then carry out the mechanical intervention. This helps avoid work interruptions due to water ingress or unforeseen fractures.
Planning, work organization, and quality
Robust planning includes the selection of the injection resin system, the sequencing of work sections, the specification of injection points, and coordination with the subsequent steps of deconstruction. Quality assurance includes trial areas, logged pressure and material data, visual and functional checks, and adapted occupational safety.
Occupational safety and health protection
During processing and reaction, substances may be released that require protective measures. Personal protective equipment, good ventilation, and low-exposure work organization are essential. Observe manufacturers’ information on hazards and handling; legal requirements and limit values must be complied with.
Practical tips for the jobsite
- Clarify the cause: Assess crack causes and structural movements before any injection.
- Select the right material: Seal elastically, bond rigidly—depending on objectives and moisture.
- Adapt the drilling pattern: Short packer spacing for fine cracks; staggered arrangement for changing crack courses.
- Control pressure: As low as possible, as high as necessary—continuously observe the structure’s response.
- Use the pot life: Expect accelerated reaction in warm environments; mix material fresh.
- Plan for follow-up work: Remove packers, close drill holes, perform a tightness test.
- Prepare demolition: After injection, wait for drying or curing times, then deploy the concrete demolition shear or splitters.
Limits, risks, and environmental aspects
Injection resins cannot accommodate movement joints without limits; for dynamic joints, choose elastic systems or structural solutions. Strong hydrostatic pressure requires adapted concepts. Chemical incompatibilities with certain substrates or moisture levels are possible. Handling reactive components requires care; emissions and residual materials must be handled and disposed of properly. These statements are general and do not replace project-specific planning.
Standards and technical fundamentals (general)
For planning and execution, relevant standards for concrete repair, structural waterproofing, and injection technology must be consulted. These include European and national standards as well as bulletins of the relevant professional bodies. Decisive are the requirements regarding adhesion, watertightness, durability, and documentation. Project participants should consider the current editions and interpret them specific to the project.