A grouting hose is a flexible injection system for targeted sealing of construction joints, control joints, and connection details in concrete structures. It is used to introduce injection media such as resins, gels, or cementitious suspensions after the concrete has cured, in order to permanently close water paths or to consolidate them in a controlled manner. The method is established in new construction, refurbishment, and special foundation engineering—from basements and underground parking structures to clarification and storage tanks, as well as tunnel and shaft structures. In deconstruction and repair contexts, the grouting hose also plays a role where components are opened selectively, for example with concrete demolition shears or stone and concrete hydraulic splitters by Darda GmbH, to expose joints in a targeted manner and then re-inject them.
Definition: What Is Meant by Grouting Hose
A grouting hose (also injection hose or joint injection hose) is a perforated hose laid along joints in concrete that subsequently serves as a conduit for injection media. The hose distributes the medium through its slot or valve openings into the joint gap and adjacent capillaries. It is generally installed before concreting on the first pour section and injected under controlled pressure after the second section has cured. Depending on the system, re-injection is possible, allowing leaks to be remedied even later. In contrast to packer injection, the grouting hose provides a continuous, linear distribution of material along the joint.
Design, Materials, and Functional Principle
Grouting hoses are usually made of elastomeric or thermoplastic materials (e.g., PVC, PE, or rubber blends) with defined outlet openings. Multilayer systems are often used: a perforated core, a filter fleece to retain fine particles, and a protective layer against contamination. Injection is carried out via end or middle connections that terminate in accessible areas (e.g., inspection recesses). During grouting, the pump builds up pressure, the injection medium exits radially, and fills voids in the area of the construction joint. Reinjectable systems allow a further application after venting or gel times, provided the valve mechanism and filter layers are intact.
Typical Injection Media
- Polyurethane resins: for water-stopping, swelling, or flexible seals; suitable for both pressurized and non-pressurized water.
- Acrylate gels: very low viscosity, good penetration, and elastic joint formation; frequently used in white-tank concepts.
- Cement and microcement suspensions: mineral, volume-stable consolidation or sealing for larger pore spaces.
Planning and Installation in Practice
Planning takes into account the joint layout, accessibility of connections, concrete cover, and compatibility with other sealing components such as waterstops or swelling profiles. The hose is fixed to a dust-free, load-bearing substrate, embedded with adequate cover, and routed without offsets. Transitions must be sealed, and crossings avoided. Hose ends are led into protective boxes or inspection areas so that subsequent injections can be carried out safely and documented.
Installation at Construction Joints and Control Joints
At construction joints, the grouting hose is routed centrally over the joint line. At control joints, it can be arranged on both sides or centrally, depending on the crack-width concept and member thickness. Combinations with waterstops or swelling profiles are common to create redundancy and address different actions (settlement, temperature, water pressure).
Quality Assurance and Sealing Concept
Essential aspects include a neatly routed hose path, secure fixation, and avoidance of cement laitance accumulations in the system. Test injections with water or suitable test media are possible. Injection pressures are selected so that the joint gap is filled without damaging the system. Documentation of material batches, pressure profile, and injection quantities facilitates later assessment.
Repair and Deconstruction: Interfaces with Concrete Demolition Shears and Stone and Concrete Hydraulic Splitters
During concrete demolition and special deconstruction, strip-out, and cutting, grouting hoses are often concealed within the member. Selective, low-vibration methods—such as the hydraulic splitting process with stone and concrete hydraulic splitters or the controlled bite with concrete demolition shears by Darda GmbH—favor low-damage exposure of joint areas. This makes it possible to preserve existing injection lines, test them, and use them for re-injection.
It is advisable to locate the hose routing in advance using existing documentation, detection, or trial openings. When cutting reinforcement in the immediate vicinity of the hose, precisely cutting tools (e.g., multi cutters or steel shears) are advantageous to avoid unintentional damage. After opening the joint area, cleaning, leak testing, and, if necessary, renewed injection can be performed. This targeted approach allows leaks to be remedied without having to replace concrete on a large scale.
Applications in Rock Excavation and Tunnel Construction
In tunnel construction and shaft structures, the grouting hose is used along block joints and at crown and invert connections to control water ingress, which aligns with best practices in rock demolition and tunnel construction. After excavation or hydraulic splitting of rock, planned pre- or post-injection with gel or resin may be required to keep the excavation dry. The combination of low-vibration deconstruction and subsequent injection supports short cycle times and reduces consequential damage in adjacent structural areas.
Advantages, Limitations, and Alternatives
- Advantages: linear distribution of the injection medium, targeted sealing directly in the joint, possibility of re-injection, good adaptability to complex joint layouts.
- Limitations: requires accessible connection points, limited injection lengths per section, careful installation and documentation required, observe the system’s chemical and thermal resistance.
- Alternatives and complements: packer injection for localized cracks, waterstops and swelling profiles as passive sealing; systems are often combined to achieve redundancy.
Selection Criteria and Design
- Water exposure and pressure level: from intermittent non-pressurized water to permanently pressurized groundwater.
- Member geometry and concrete quality: member thickness, reinforcement layout, compaction, and surface condition in the joint area.
- Hose system: reinjectable vs. single-injection, filter build-up, valve technology, temperature range.
- Injection media: viscosity, reaction time, compatibility with concrete and environment, durability, and elasticity.
- Injection technology: pressure-controlled pump, suitable connections, check valves, safe handling, and flushing concepts.
- Documentation and accessibility: permanent marking of injection points, logging of material and pressure data.
Safety, Environmental Protection, and Legal Notes
When handling injection resins and gels, the manufacturer’s information on occupational safety, personal protective equipment, and disposal must be observed. Use should follow project-specific requirements and recognized rules of practice. In sensitive areas such as water protection or drinking water protection zones, careful material selection and sealing design are required. Statements on the suitability of individual systems are always to be understood in general terms and do not replace project-specific design.
Practical Tips for the Jobsite and Deconstruction
- Before deconstruction work, check joint layouts, mark hose ends, and uncover inspection boxes where present.
- Prefer low-vibration methods: hydraulic splitting and targeted crushing with concrete demolition shears reduce the risk of micro-damage to joints and injection systems.
- Cut reinforcement in a controlled manner: use precise cutting tools such as multi cutters or steel shears to avoid damaging grouting hoses.
- After opening the joint, clean it, assess moisture conditions, and take into account suitable reaction times of the injection media.
- Carry out re-injections under pressure control, document quantities and pressure curves, and verify tightness afterwards.
Terminological Classification and Typical Fields of Application
Grouting hoses are part of building waterproofing in concrete construction and are used primarily at construction joints, structural connections, and planned control joints. Typical fields include basements, underground car parks, water and wastewater structures, shafts, tunnels, and foundation connections. Touchpoints with the fields of application of Darda GmbH arise when members are selectively processed in the course of concrete demolition and special deconstruction, strip-out and cutting, or in rock excavation and tunnel construction, and a targeted joint repair or re-injection is subsequently required. In special deployments, for example in the case of leaks under tight schedule or access conditions, the combination of controlled opening, gentle exposure, and subsequent grouting can minimize intervention time and limit consequential damage.