Hydrodemolition (also known as hydro demolition, hydroblasting, hydro blasting, hydromilling, waterblasting, and waterjetting) is a

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

removal technique which utilizes high-pressure water, often containing an

abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...

material, to remove deteriorated and sound concrete as well as

asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

and

grout Grout is a dense fluid which hardens to fill gaps or used as reinforcement in existing structures. Grout is generally a mixture of water, cement and sand, and is employed in pressure grouting, embedding rebar in masonry walls, connecting sect ...

. This process provides an excellent bonding surface for repair material and new coating applications. First developed in Europe in the 1980s, this technology has become widely accepted for concrete removal and surface preparation throughout Europe and North America. Hydrodemolition is not used as much for

demolition Demolition (also known as razing, cartage, and wrecking) is the science and engineering in safely and efficiently tearing down of buildings and other artificial structures. Demolition contrasts with deconstruction, which involves taking a bu ...

as it is for surface restoration and protection projects. When concrete has deteriorated or the reinforcing steel has begun to corrode, it is necessary to remove any unsound concrete and reinforcing bars (rebar) in order to replace it with new concrete and maintain the integrity of the structure. This process has also been used to remove sound concrete that is not compromised in any way. This may be done to install a preventive

cathodic protection Cathodic protection (CP; ) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded "sacrifi ...

system, or to remove concrete in structures in which vibration is a concern. Unlike

jackhammer A jackhammer (pneumatic drill or demolition hammer in British English) is a pneumatic or electro-mechanical tool that combines a hammer directly with a chisel. It was invented by William Mcreavy, who then sold the patent to Charles Brady King ...

s, hydrodemolition does not produce vibrations throughout a structure and therefore does not introduce micro fractures.

Applications

Hydro scarification

The process of hydro scarification (a.k.a. hydroscarification or scarification) uses ultra high pressure water to remove the top surface of a concrete bridge or road surface. Usually the removal is within 1/4" to 3/4" at the most, but can be of any depth above the top layer of

rebar Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. ...

. Removal of this type is done in order to provide a good microfracture-free surface for bonding with new, sound concrete. Much like applying oil and chips to an asphalt road, this helps extend the useful life of the bridge decking and road surface by delaying the need for complete replacement. Another application for hydro scarification is for decontamination, as for example is planned to be used in the

Chernobyl New Safe Confinement The New Safe Confinement (NSC or New Shelter, rarely Arka) is a structure put in place in 2016 to confine the remains of the number 4 reactor unit at the Chernobyl Nuclear Power Plant, in Ukraine, which was destroyed during the Chernobyl disas ...

for the concrete of Unit 4 of the

Chernobyl Nuclear Power Plant The Chernobyl Nuclear Power Plant (ChNPP; ; ), is a nuclear power plant undergoing decommissioning. ChNPP is located near the abandoned city of Pripyat in northern Ukraine northwest of the city of Chernobyl, from the Belarus–Ukraine borde ...

Partial depth removal

Partial depth removal involves the selective removal of deteriorated concrete to a certain depth or of a concrete overlay to a depth exceeding 3/4". It is usually done in the case of concrete restoration projects where embedded objects such as rebar are substantial and need to be preserved. Hydrodemolition is ideal for concrete scarification at precision depths and preserving existing rebar for reuse.

Full depth removal

Complete removal of a concrete deck is done when it is too deteriorated to keep, but the structural concrete is adequate or can be easily repaired after the hydrodemolition has taken place. It can also be a preferred alternative where a bridge deck has been compromised during initial construction but not yet open to traffic. It allows the preservation of the reinforcement while the deck concrete can be fully replaced to meet the design intent and avoid the need for potential future repairs under traffic. Precast concrete beams are often used in structures such as bridges and parking garages. Hydrodemolition has been used successfully to remove concrete over these beams, where alternate methods such as jackhammers might have caused fracture of the beams.

Structures

This technology has been used on the following types of structures: bridge decks and substructures,

parking structures A multistorey car park (British and Singapore English) or parking garage (American English), also called a multistory, parking building, parking structure, parkade (mainly Canadian), parking ramp, parking deck or indoor parking, is a buil ...

dams A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...

and

spillways A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure th ...

water treatment Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, inc ...

facilities,

tunnels A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A Pipeline transport, pipeline is not a tunnel, though some recent tunnels have used ...

and aqueducts,

nuclear power plant A nuclear power plant (NPP) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a generator that produces ...

s, piers and docks,

stadiums A stadium ( : stadiums or stadia) is a place or venue for (mostly) outdoor sports, concerts, or other events and consists of a field or stage either partly or completely surrounded by a tiered structure designed to allow spectators to stand o ...

, warehouses, transfer stations, and

retaining wall Retaining walls are relatively rigid walls used for supporting soil laterally so that it can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to ...

Safety

Any process that is powerful enough to cut concrete can cut skin and bone. Operators of hydrodemolition equipment are required to wear protective equipment. For robotic hydrodemolition equipment, the operator wears steel-toed boots, eye protection, earmuffs and hard hat. Hand lance operators wear steel-toed boots, metatarsals, shin guards and sometimes

body armor Body armor, also known as body armour, personal armor or armour, or a suit or coat of armor, is protective clothing designed to absorb or deflect physical attacks. Historically used to protect military personnel, today it is also used by variou ...

Environmental benefits

Hydrodemolition offers a number of environmental benefits. Hydrodemolition creates no dust pollution, reduces noise pollution, and the water used during the process can be collected after use to minimise any risk of contamination. Recently an innovative technology is available, which allows to clean and reuse the process-water after hydrodemolition. This makes in particular sense, when there is no fresh water access for feeding the high pressure pump. An Austrian company has developed the first mobile, container-based wastewater treatment device, which can be operated directly on site.

Related processes

Hydrocleaning

All types of surfaces can get dirty from excessive use and abuse, water and air pollution, and general exposure to the elements. These surfaces can be hydrocleaned using high pressure water or high pressure water mixed with an abrasive.

Coating and sealant surface preparation

The use of high pressure and ultra high pressure water has been used to clean various coatings on concrete surfaces for the purpose of repair and reapplication. Coatings are used to protect concrete from the elements, rain, salt, and to create a friendlier surface for human use. Concrete can also be covered with carpet or tiles using a heavy duty glue or mastic. High pressure water can be used to clean these materials off when new carpet or tiles are desired.

Airfield rubber removal

Commercial and military airfields are required to maintain certain levels of friction on runways to prevent planes from skidding. Runway design, weather and amount of rubber remaining from tire wear all play a role in the level of friction of a landing strip. If too much rubber is present, the friction of the landing strip will be less, requiring more distance for landings, especially in wet weather. High pressure water can be used to remove rubber and restore required friction.

Cold cutting

Cold cutting can be used to cut steel, concrete and other materials with the addition of an abrasive feed at the nozzle. Cold cutting is especially useful for cutting of pipes, vessels and tanks in areas where there is a requirement for no sparks or heat generated, such as chemical plants, oil rigs, or even residential neighborhoods, due to the lack of explosive force usually required to break concrete.

References

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