Grout mortar is a precise construction material for structurally bonded undergrouting, anchoring, and leveling layers. It permanently connects components, reliably distributes loads, and securely closes voids. In combination with tools and equipment from Darda GmbH—such as concrete pulverizers or hydraulic wedge splitters—it enables clean interfaces between demolition, deconstruction, and the subsequent structural build-up. This allows foundations to be undergrouted, anchors to be set, or boreholes to be sealed without jeopardizing the dimensional accuracy or durability of the overall structure.
Definition: What is meant by grout mortar
Grout mortar is a highly flowable, usually cementitious or resin-modified mortar for void-free casting of joints, cavities, and bearing surfaces. Typical characteristics include a low-shrinkage to shrinkage-compensated formulation, a self-leveling consistency, and defined early and final strength. Grout mortar is primarily used for undergrouting machinery and power units, for grouting anchor rods, for the structurally bonded leveling of uneven bearings, and for sealing boreholes and core drill holes. In demolition and deconstruction processes, it creates the connection between the existing structure and new components or temporary auxiliary structures.
Properties and composition
Depending on the application, composition and performance profile vary. Cementitious systems are universally applicable, robust, and economical. Resin-modified or purely resin-based systems provide increased pull-off values, chemical resistance, and rapid curing, for example under dynamic loads. Important parameters include:
- Workable, flowable to highly flowable consistency for void-free flow
- Shrinkage compensation to minimize edge spalling and stress cracking
- Defined early strength for rapid loadability, for example in tightly scheduled deconstruction sequences
- Good pull-off/bond strength on sound, roughened concrete substrates
- Resistance to oil, fuels, or de-icing salts—depending on the system
- Low permeability to limit ingress of moisture
Fields of application and interfaces in deconstruction
In concrete demolition and special deconstruction, grout mortar forms a precisely fitting connection between substrate and component—temporary or permanent. During building gutting and cutting, bearings for shoring are leveled, core drill holes are grouted after cable or pipe installation, and new anchors are installed for load transfer. In combination with concrete pulverizers, torn edges and bearings can be made planar after demolition using grout mortar. When working with hydraulic wedge splitters, boreholes can be purposefully filled, sealed, or used as anchor points with grout mortar after controlled splitting to ensure subsequent work.
Relation to concrete pulverizers
Where concrete pulverizers selectively break down load-bearing components, irregular bearings often remain. A precise undergrout fills these uneven areas, restores load transfer, and prevents edge bearing pressures. In addition, embedded anchors, rails, or brackets can be grouted with grout mortar to receive new components or temporary shoring.
Relation to hydraulic wedge splitters
The splitting technique follows defined borehole grids. After splitting, bores are either permanently closed or used as load-bearing anchorage. Grout mortar seals bore channels, minimizes water paths, and allows the void-free embedding of threaded rods and anchor sleeves for subsequent installation work.
Material selection: cementitious or resin systems
The choice depends on loading, environmental conditions, and construction sequencing:
- Cementitious grout mortars: universal, economical, applicable in layer thicknesses from a few millimeters to several centimeters; suitable for foundations, undergrouting of power units, and anchor grouting.
- Resin-based systems: rapid curing, high adhesion, and chemical resistance; useful when downtime is limited or in areas exposed to oils/chemicals.
For dynamically loaded bearings, for example under Hydraulic Power Units, vibration-appropriate, shrinkage-compensated systems with defined elasticity and high fatigue resistance are suitable.
Substrate preparation and application
The quality of the substrate determines bond performance. Practical principles generally include:
- Expose sound concrete, remove weak zones, roughen the surface
- Clean thoroughly (dust- and grease-free), form defined edges
- Depending on the system, pre-wet the substrate, but avoid standing water
- Produce formwork that is tight, dimensionally stable, and suitable for removal
- Mix mortar homogeneously, adhere to the manufacturer’s water addition
- Place continuously from one side, minimize air entrapment
- Cure and protect from drafts and drying
Temperature, humidity, and component geometry significantly influence flow behavior and strength development. Follow the instructions of the respective product data sheets.
Grout mortar in rock excavation and tunnel construction
In rock excavation, grout mortar stabilizes temporary anchor points, fixes inclined supports, and seals boreholes to limit water paths. In rock demolition and tunnel construction, cable penetrations, anchor sleeves, and built-in components are structurally bonded by grouting. When using splitting cylinders for rock, precise grouting supports the safe load transfer of auxiliary structures and facilitates controlled follow-up work with concrete pulverizers or steel shear.
Natural stone extraction
In natural stone extraction, rows of boreholes are used. After blocks are freed, fixtures, lifting points, or rails can be secured with grout mortar to safely move or edge material before it is further reduced.
Integration of other tools and equipment
Grout mortar accompanies numerous work steps with tools from Darda GmbH:
- Hydraulic demolition shear and multi cutters: After separating components, openings, chases, or bearing surfaces are set flush and strengthened with grout mortar.
- Steel shear and tank dismantling: When removing tanks or steel sections, bearings and brackets often need to be subsequently underpinned or anchors grouted to be leak-tight.
- Hydraulic power packs: Foundations and machine baseplates are grouted void-free to reduce vibrations and introduce loads evenly.
Normative guidance and quality assurance
Recognized codes exist for grouting and anchoring mortars that describe requirements for material properties, adhesion, and durability. Typical performance documentation covers compressive strength, pull-off strength, tendency to effloresce, shrinkage behavior, resistances, and temperature ranges. Project-specific verification of suitability, test certificates, and accompanying documentation is advisable. Trial areas, fresh mortar checks (consistency, working time), and documented curing increase execution reliability.
Sizing and consumption
Demand is determined by the volume of the joint or cavity. In practice, the following has proven effective:
- Determine geometry (length × width × thickness)
- Consider infeed allowances and the formwork edge
- Include a material reserve for losses
For large-area undergrouting, a conveyance-suitable subdivision into fields with a defined flow path is recommended to avoid air inclusions.
Avoid common pitfalls
- Excessive water addition—reduces strength and promotes segregation
- Insufficient substrate preparation—reduces pull-off strength and bond
- Lack of curing—increases the risk of shrinkage cracking
- Too little head height or interrupted pour—promotes voids
- Unsuitable temperature control—affects curing and final strength
Occupational safety and environmental aspects
Grout mortar is alkaline in the fresh state. Personal protective measures, low-dust mixing, and controlled cleaning of tools are recommended. Wash-out water and residual quantities must be handled according to local requirements; discharge into soil or water bodies must be avoided. For interior work, dust extraction and orderly logistics support execution safety.