Hydrodemolition

Hydrodemolition (also known as hydro demolition, hydroblasting, hydro blasting, hydromilling, waterblasting, and waterjetting) is a concrete removal technique which utilizes high-pressure water to remove deteriorated and sound concrete as well as asphalt and grout. This process provides an excellent bonding surface for repair material and new coating applications. First developed in Europe in the 1970s, 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 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 system, or to remove concrete in structures in which vibration is a concern. Unlike jackhammers, hydrodemolition does not produce vibrations throughout a structure and therefore does not introduce micro fractures.

Applications

Hydrodemolition can be used for horizontal, vertical, and overhead concrete removal and surface preparation on reinforced and non-reinforced structures. It is effective in removing concrete from around embedded metal elements such as reinforcing steel, expansion joints, anchorages, conduits, shear connectors, and shear studs. Hydrodemolition can be used for localized removals where deterioration is confined to small areas and for large area removals in preparation for a bonded overlay. This technology can also be used to remove existing coatings from concrete. (International Concrete Repair Technical Guidelines No. 03737)

Hydro scarification

The process of hydro scarification uses 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. Removal of this type is done in order to replace the top of a bridge deck or road surface 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.

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.

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. 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.

tructures

This technology has been used on the following types of structures: bridge decks and substructures, parking structures, dams and spillways, water treatment facilities, tunnels and aqueducts, nuclear power plants, piers and docks, stadiums, warehouses, transfer stations, and retaining walls.

afety

Any process that is powerful enough to cut concrete can cut skin and bone. Operators of hydrodemolition equipment are required to wear many types of 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.

Related processes

Hydrocleaning

Surfaces of all types can get dirty from excessive use and abuse, water and air pollution and general exposure to the elements. These surfaces can be cleaned using high pressure water (hydrocleaning) 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 airports are required to keep certain levels of friction on the landing strips in order to prevent planes from sliding off. Runway design, weather and amount of rubber on the runway 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 lower requiring more distance for the plane to land, especially in wet weather. High pressure water can be used to remove rubber left from airplane tires and restore required friction levels.

ee also

*Hydraulic mining

References

* International Concrete Repair Institute. (2004). "Guide for the Preparation of Concrete Srfaces for Repair Using Hydrodemolition Methods - Guideline No. 03737". Des Plaines, IL: ICRI.

External links

* [http://www.rampart-hydro.com/how_it_works.htm How hydrodemolition works]
* [http://www.rampart-hydro.com/clean_up.htm Clean up after the process]
* [http://www.rampart-hydro.com/dry-hydrodemolition-video.htm Video of dry hydrodemolition]
* [http://www.icri.org/ International Concrete Repair Institute]
* [http://www.icri.org/publications/search_details.asp?ProductID=448 G03737-Guideline for the Preparation of Concrete Surfaces for Repair Using Hydrodemolition Methods]