Hydrophobization refers to the targeted water-repellent treatment of mineral construction materials such as concrete, natural stone, or masonry. It plays an important role in planning, maintenance, and deconstruction: it influences water uptake, freeze–thaw resistance, chloride ingress, and the durability of components. In day-to-day practice of concrete demolition and special deconstruction, strip-out and cutting, rock excavation and tunnel construction as well as natural stone extraction, it is helpful to know whether surfaces have been hydrophobized, since this affects, among other things, dust binding, cooling water routing, and the gripping behavior of concrete pulverizers as well as the use of rock and concrete splitters in practice. Tools and systems from Darda GmbH – from concrete pulverizers to stone and concrete splitters and hydraulic power packs through to combination shears, Multi Cutters, steel shears, tank cutters, and stone splitting cylinders – regularly encounter hydrophobized substrates in practice, whose properties influence the approach.
Definition: What is meant by hydrophobization
Hydrophobization is understood to mean the penetration of hydrophobic active agents into the pore spaces of mineral construction materials or the application of a water-repellent layer to significantly reduce capillary water absorption. The pores generally remain vapor-permeable; the measure does not constitute waterproofing. Typical are impregnations based on silanes or siloxanes that increase the contact angle between water and solid so that rain or splash water beads off. The goal is protection against moisture, freeze–thaw damage, and transported contaminants (e.g., de-icing salt chlorides) without significantly altering the appearance and surface texture.
Hydrophobization in construction: functions and limits
Hydrophobizations lower water uptake, reduce the risk of spalling due to frost, and slow down chloride ingress. However, they do not replace waterproofing or coatings with crack-bridging properties. On concretes, natural stones, and calcium silicate bricks, water vapor diffusion generally remains intact. Important is the distinction between hydrophobic impregnations (penetrating into the pores) and superficial coatings (lying on the surface). For deconstruction and cutting work this means: The mechanics in the component core remain unchanged by hydrophobization, while interaction at the surface (water, dust, adhesion) can change noticeably.
Operating principle and materials
Hydrophobic active agents adsorb onto pore walls and lower surface energy. This slows capillary rise. Frequently used systems are:
- Silane impregnations (low molecular size, good penetration depth, particularly on dense concrete)
- Siloxane systems (suitable for more porous substrates, natural stone, brick)
- Silicone resins or combinations (impregnation with slight film formation)
- Other hydrophobic components such as stearates; fluorinated systems are less common
Impregnation versus coating
Impregnations act within the pore system and modify surface wetting without forming significant layer thicknesses. Coatings lie on the surface, can alter hue and roughness, and may be crack-bridging. For deconstruction, it is relevant that impregnations are usually near-surface, while coatings can affect gripping with concrete pulverizers or the marking and preparation of cut edges.
Significance in concrete demolition and special deconstruction
On hydrophobized components, the behavior of water and dust at the surface changes. This has practical consequences for the use of concrete pulverizers, stone and concrete splitters, and supplementary tools:
- Dust suppression: Water beads more strongly. Fine mist or alternative binders can improve the capture of fine dust. Water routing should be optimized so that spray mist adheres to the surface.
- Gripping points: Smooth, water-repellent surfaces can initially offer lower friction. Mechanically robust edges and defined attack areas for concrete pulverizers are advisable.
- Crack formation: Hydrophobization is generally only near the surface. Force transmission into the component core and splitting behavior are usually not significantly affected by it.
- Retained strength: Hydrophobized components may exhibit fewer moisture-related damages over their life cycle. This can lead to higher retained compressive strength and influence the required cutting and splitting parameters.
Strip-out and cutting: effects on sawing and core drilling
During wet sawing and core drilling, hydrophobization can reduce wetting. Cooling and flushing water tends to form droplets; removal of grinding slurry may require adjusted water volumes or nozzles. Markings, temporary adhesives, or dust protection films often adhere more poorly on hydrophobic surfaces. Before installing temporary anchors or applying protective films, localized light grinding or cleaning can improve adhesion.
Rock excavation, tunnel construction and natural stone extraction
Hydrophobization is rare in the rock excavation itself. For quarried natural stone blocks, facade or landscape stones, hydrophobic protection is more common. When splitting or positioning with stone and concrete splitters and stone splitting cylinders, note: Water runs off faster, surfaces dry more quickly, which can be advantageous when sweeping off drill dust and when marking. Coating-like systems can slightly change friction between grippers and stone; accordingly, clean, dust-free gripping zones are advisable.
Identifying hydrophobized surfaces on site
For work preparation, it is helpful to identify hydrophobized components. Indicators include:
- Drop test: Water droplets bead with a high contact angle.
- Color tone: Occasionally a slightly deepened color tone or darker wetting edges.
- Karsten tube principle: Low water uptake over defined time periods (qualitative).
If in doubt, small test areas provide information on water uptake and adhesion behavior—e.g., for planned markings, temporary adhesions, or gripping with concrete pulverizers.
Quality assurance and testing approaches
Hydrophobizations are typically evaluated via water uptake, penetration depth, and visual criteria. In practice, a stepwise approach has proven effective:
- Inventory: Surface condition, visible coatings, previous repairs.
- Sampling: Clean small areas, assess wetting behavior.
- Field trials: Adjust water mist, nozzles, gripping points, and process parameters.
- Documentation: Photos, brief measurement logs, definition of the working method.
Application in existing structures: procedure for hydrophobization
If hydrophobization is newly applied—e.g., to protect fair-faced concrete surfaces or natural stone—clean, dry, and load-bearing substrates are important. The measure influences later deconstruction work: cut edges remain dry longer, surfaces shed water, and cleanability improves.
Substrate preparation
Remove loose layers, cement laitance, and contamination; perform a test spray to estimate absorbency. Very dense or polished surfaces are less receptive.
Application and curing
Apply evenly to saturation; remove excess. Observe temperature and humidity conditions. After curing, the water-repellent effect and improved drying after precipitation become apparent.
Post-treatment
Verification through wetting tests. For later work (e.g., drilling, cutting, gripping), hydrophobic zones can be locally ground or cleaned to deliberately increase adhesion and friction.
Influence on tool handling and process parameters
When working with concrete pulverizers, combination shears, Multi Cutters, steel shears, and tank cutters, a hydrophobic surface can reduce initial static friction on smooth edges. In practice, defined, cleaned attack areas are effective. For stone and concrete splitters the splitting force acts internally; hydrophobization primarily affects the surface environment (dust, moisture, film residues), not the splitting mechanism. Hydraulic power packs such as mobile hydraulic power units provide the required pressures independently of hydrophobization; however, drier, dustier conditions may require finely tuned dust suppression.
Material selection, environmental aspects and reuse
Water-based systems are low-odor and vapor-permeable; solvent-based variants can achieve deeper penetration. In deconstruction and recycling, hydrophobized concrete is generally recyclable without issues. Careful separation of coated surfaces can facilitate processing. From an environmental perspective, sparing dosage, suitable application methods, and low-emission products are advantageous.
Safety and health protection
When handling hydrophobic systems, observe the respective safety data and general protective measures. For deconstruction work on hydrophobized surfaces: route dust and spray mist so that they bind effectively without generating unnecessary aerosols. Personal protective equipment should be selected according to the task.
Avoiding common misconceptions
Hydrophobization is not waterproofing and not structural reinforcement. It reduces water uptake, generally allows water vapor to pass, and does not alter the load-bearing capacity of the component. Visible gloss or film formation tends to indicate a coating. For work planning with concrete pulverizers and stone and concrete splitters, the distinction is essential.
Practical notes for the application areas of Darda GmbH
In concrete demolition and special deconstruction, early identification of hydrophobic zones facilitates the choice of gripping points and coordination of dust suppression. In strip-out and cutting, wetting and slurry removal should be adjusted. In natural stone extraction and rock excavation, hydrophobization primarily plays a role on already treated components—such as coping stones, parapets, or facade panels. Special operations benefit from test areas to quickly understand the interaction of surface, water, and tool.