Concrete Removal and Surface Preparation with High-Pressure Water

Selective concrete removal requires defined removal criteria

In concrete refurbishment, damaged material can be selectively removed to expose sound substrate. Suitable process parameters depend on concrete quality, required depth, reinforcement, area throughput, and the required surface condition.

Why the reinforcement stays undamaged

The high-pressure water jet removes concrete by penetrating pores and micro-cracks and bursting the matrix apart from within. Damaged, carbonated, or cracked concrete has more such flaws than sound concrete and is therefore removed first. The process is inherently selective: it follows the damage rather than working to a fixed depth.

The reinforcing steel remains in place because it is ductile and has no brittle-fracture microstructure for the jet to act on. It is exposed and de-rusted in the process, not weakened.

Comparison with mechanical removal methods
Characteristic	High-Pressure Water Jetting	Chipping and Milling
Working principle	Hydraulic bursting within the pore structure	Impact or cutting action on the surface
Selectivity	Follows the damage pattern	Removes to a fixed depth, regardless of condition
Residual substrate	No new micro-cracks, no vibration	Stress cracks and structure-borne vibration possible in the remaining cross-section
Reinforcement	Exposed and de-rusted	Can be struck or deformed
Substrate afterward	Rough and cleaned, ready for direct coating	Usually requires additional substrate preparation
Side effects	Produces wastewater and concrete sludge	Dust, noise, vibration

Cleaning, roughening, and coating removal are different process goals

Merely cleaning a surface places different demands on the process than deliberately roughening it or removing several millimetres of material. The specification should therefore state, up front, both the current condition and the condition required after processing.

What the regulatory framework requires

Concrete removal and substrate preparation in construction are regulated in Germany independently of the machine safety standard. Working safely under EN 1829-1 does not by itself mean the repair meets code.

TR InstandhaltungTechnical Rule for the Maintenance of Concrete Structures (DIBt)

Applies together with the DAfStb Guideline “Protection and Repair of Concrete Structural Members” (October 2001 edition). Building-code status is established via the Model Administrative Provision on Technical Building Regulations under German state law.

building code (Germany)

ZTV-ING, Part 3Additional Technical Contract Conditions, Structural Engineering

Section 4 governs protection and repair of concrete components on federal highway structures in Germany.

transport infrastructure (Germany)

DBV Technical BulletinHigh-Pressure Water Jetting Technology in Concrete Construction

Guidance bulletin from the German Concrete and Construction Technology Association with practical guidance on cleaning, coating removal, roughening, and concrete removal.

practice guide (Germany)

DIN 18349German Additional Technical Contract Conditions for Concrete Preservation Work

Governs the contractual side of execution under German construction contract law.

contract law (Germany)

Minimum pressure for substrate preparation (German construction codes)
Regulation	Term Used	Minimum Pressure
TR Instandhaltung with DAfStb Guideline	High-pressure water jetting	60 N/mm² – 600 bar
ZTV-ING, 2013 edition	Pressurised water jetting	80 N/mm² – 800 bar
ZTV-ING, 2017 edition	High-pressure water jetting	60 N/mm² – 600 bar, aligned with the guideline

The ZTV-ING was aligned with the guideline in its 2017 edition. For existing contracts, checking the agreed edition matters: the older version states a minimum value 200 bar higher.

Roughness as the acceptance criterion

The TR Instandhaltung generally requires exposing the coarse aggregate in a cusped pattern as evidence of adequate roughness. That is a verifiable outcome at the substrate, not a pressure figure at the equipment — and it is the benchmark against which substrate preparation is accepted.

For the replacement concrete, TR Instandhaltung Part 1 specifies layer thicknesses: at least 30 mm, at most 60 mm, and up to 100 mm when filling localised defects. These figures indirectly determine how deep removal must go. The removal depth is not a free choice for the contractor.

Mechanised tools improve reproducibility and reduce operator burden

Depending on area and accessibility, manual lances, surface cleaners, robotic or remotely operated systems, or specially guided tools are used. At higher power levels, tool guidance, reaction-force control, and operator protection become correspondingly more important.

Removal water and solids are part of the process

The process generates water carrying concrete particles, coating residue, or other material. Collection, separation, and disposal must therefore be planned together with the removal process itself.

Technical references: Hammelmann – Removal and Roughening · KAMAT – Water Jetting.

Wastewater: the underestimated part

The resulting water is not simply dirty water. Dissolved cement paste makes it strongly alkaline, and it carries concrete sludge. Both generally rule out discharge without treatment.

Contain itSeal off the area and collect the water in a controlled manner before it reaches drains or soil.
Settle itSeparate solids in a sedimentation basin or container; the sludge must be disposed of separately.
Neutralise itLower the pH before discharge; the limit value follows the local wastewater ordinance.
Coordinate itClarify discharge with the sewer operator in advance. Requirements are set locally in Germany, not nationally.
Document itWhere coatings contain hazardous substances, the removed material is hazardous waste; evidence of disposal is part of the deliverable.

Frequently asked questions about concrete removal

What does the HDW process mean?

HDW stands for Hochdruckwasserstrahlen — high-pressure water jetting. German construction literature also uses the abbreviation HDWS for Hochdruckwasserstrahlschneiden/-strahlen. Both refer to removing concrete and coatings using pure water at high pressure, without added abrasive.

What pressure is needed for concrete removal?

For substrate preparation, the TR Instandhaltung together with the DAfStb Guideline specifies a minimum pressure of 60 N/mm², or 600 bar. For deeper removal of damaged concrete, work is usually carried out well above that, often between 1,000 and 3,000 bar. What matters is not pressure alone, but the hydraulic power resulting from pressure and flow rate together.

Is the reinforcement damaged?

No. The jet removes the brittle concrete matrix but finds no point of attack on the ductile reinforcing steel. The steel is exposed and de-rusted in the same step. This is one of the main reasons the process is preferred over chipping in repair work.

How does this differ from sandblasting?

In sandblasting, a solid medium removes the material and must then be disposed of together with the debris. In high-pressure water jetting, water is the tool; no abrasive waste is produced, but wastewater carrying concrete sludge is. Sandblasting also generates dust, a significant drawback where old coatings contain hazardous substances.

Hand-held or mechanised?

Hand lances are flexible and indispensable for small or hard-to-reach areas, but are subject to the reaction-force limits of DGUV Rule 100-500. From medium-sized areas upward, robot- or gantry-guided systems become more economical and deliver more uniform removal, because traverse speed and stand-off distance stay constant.

Regulations on concrete removal

Technical Rule “Maintenance of Concrete Structures,” Part 1, German Institute for Building Technology (DIBt) – https://www.dibt.de/fileadmin/dibt-website/Dokumente/Referat/I4/TR_Instandhaltung_Betonbauwerke_Teil1.pdf
DGUV Rule 100-500, chapter 2.36 – Working with Liquid Jetting Equipment, issue March 2017 – https://publikationen.dguv.de/media/pdf/27/3a/6a/R500_236.pdf

Concrete removal and surface preparation with high-pressure water.