Words can be deceiving. One might assume that hydrodemolition is related to the overall deconstruction of structures, but this technique is rarely used in full demolition projects. As concrete demolition contractors, we study concrete construction and salvaging techniques. Hydrodemolition is a method that contractors primarily use to remove deteriorated concrete, asphalt, and grout prior to resurfacing.
What is Hydrodemolition?
Hydrodemolition is a process for removing concrete, mainly weakened concrete. It may also be used to remove sound concrete, to prepare for cathodic protection (a defense against rebar rusting). Hydrodemolition water pressure levels may be as high as 40,000 PSI, with water jetting forward at 1,500 miles per hour! This highly pressurized water can strip as much as 16 inches of concrete in a single pass. A fine aggregate (often garnet) may be blasted along with the water to assist with cutting.
There are three types of hydrodemolition:
1. Hydroscarification is used to remove the top surface of a road or bridge. It strips away ¼” to ¾” of the surface, so as to create a strong bonding surface for new concrete.
- Partial Depth Removal removes more than ¾” of concrete, grout, and asphalt to a specified depth. This is often used for concrete restoration projects when embedded support structures remain strong enough to use in renovation. Hydrodemolition contractors may use partial depth removal when delamination has occurred in the top mat of reinforcing material, or when the concrete has been chloride contaminated.
3. Full Depth Removal involves the removal of all concrete, stripped back to reveal only support beams and bars. Full Depth Removal may be used when replacing bridge deck concrete, and when removing concrete from beams.
Blasted away materials and water is generally vacuumed up using specialized trucks. Hydrodemolition wastewater is then treated and reclaimed by neutralizing pH levels.
Benefits of Hydrodemolition
• Creates a strong surface for bonding of new building materials, including concrete and coatings. The scarified surface has more surface area than achievable with other forms of concrete removal.
• Does not create structural vibrations as jackhammers do.
• Accelerates concrete removal, minimizing overall project time and cost.
• Prevents micro-fractures (bruising) by avoiding vibrations.
• Allows removal of concrete where jackhammers might otherwise fracture support beams.
• Facilitates the removal of surface coatings without damaging underlying concrete.
• Creates no dust pollution and far less noise pollution than jackhammers.
• Possible to selectively remove weakened, delaminated concrete.
• Hydrodemolition work is often done by robotics, decreasing the chance of worker injuries compared to jackhammers.
• The robotic equipment delivers uniform removal results.
• By eliminating the need for a jackhammer, hydrodemolition avoids worker safety concerns including hand/arm vibration syndrome (HAVS) and Vibration White Finger (VWF).
A hydrodemolition system includes a high-pressure water pump, a robotic cutting tractor, and a support trailer or vehicle. The robotic cutting tractor moves the water jet over the work surface; its job is to control the how much concrete is removed, and where. The water jet’s nozzle may be adjusted to angles between 5 degrees and 30 degrees of vertical. This angle creates a cone shape of demolition. The tractor moves this cone back and forth, on a transverse pattern perpendicular to the direction of the trailer. The depth of concrete removal can be adjusted by changing how many times the tractor moves the water jet across the underlying surface.
The majority of hydrodemolition work consists of parking garage and bridge deck restoration projects. However, the industry is seeing more concrete restoration work in condominiums, silos, tunnels, and high-rise structures (especially in marine locales).
Hydrodemolition is considered a form of green demolition, as it is not as polluting as other forms of concrete removal. While contractors will have to be careful to avoid water damage to the rest of the structure, cutting away concrete with water does cut down on dust and noise pollution.
At $200 to $400 per hour, hydrodemolition does not tend to be the least expensive option. However, it is time-efficient, precise, and effective, even for difficult projects. For example, one unique commercial demolition project in Key Largo, Florida, involved enlarging the porthole windows in a 12-inch-thick concrete aquarium tank. Traditional concrete sawing was attempted, but it was found to be too inaccurate and slow. A hydrodemolition setup was brought in, and a computer controlled the cutting in both X- and Y-axes to precisely, quickly cut the larger portholes without damaging steel reinforcement.
As industrial and commercial contractors operating across the West Coast, we can work with hydrodemolition contractors in multiple states to optimize sensitive concrete removal tasks. Once concrete is removed, we can salvage it for reuse on site, or for resale value for our clients. Call us today to learn whether hydrodemolition would be appropriate for your project.
[Photo by NCDOTCommunications via CC License]