HYDRODEMOLITION STATE-OF-THE-ART TECHNOLOGY IN CONCRETE REPAIRS
The traditional means of removing deteriorated concrete has included the use of jackhammers and sandblasting equipment. However, a newer and more efficient removal technique has recently been introduced into the North American market. Hydrodemolition is a technique that uses a high pressure water jet to remove areas of loose deteriorated concrete.
The hydrodemolisher is calibrated to remove concrete to a specified depth or specified strength. The specified strength method will automatically remove any unsound material up t a specified strength, regardless of the depth. This often results in higher than-anticipated quantities of removed concrete. The machine has the capacity to remove the complete slab depth, in most cases. The process also removes any corrosion products from the reinforcing steel and thus eliminates the sandblasting process, which is otherwise required. It will not, however, affect sound steel, damage-embedded duckwork, conduit, or electrical wires will generally remain intact.
Hydrodemolition produces an aggressive profile in the concrete, thereby allowing a significantly greater and stronger surface area for bonding. Unlike jackhammering, the surface is not "bruised" by micro-cracking caused by the hammers impact. As sandblasting is not necessary, there is no dust residue which might impede the bond. Also, there is no damage to the concrete due to the vibration of the reinforcement which can occur from jackhammering.
Hydrodemolition eliminates the need for decisions by the operators as to the soundness of material left, since the unsound material is removed according to the calibration of the machine. This process increases the general quality of the repair, while avoiding the unnecessary removal of sound material and the need for sophisticated quality control.
The bond strength achievable after hydrodemolition eliminates the need for bonding agents between the remaining and new material. It can be expected that, by using a cement slurry in place of the epoxy, a three-fold bond strength increase will occur.
One of the most important advantages of the hydrodemolition technique is the relative quietness of the operation. While the noise level at the work site is only marginally less then jackhammering, there is minimal vibration. In other words, the hydrodemolition noise level is dampened, whereas the jackhammering noise level is vibrational and can be heard throughout the building.
A further advantage to the client extends from the speed in which the machine operates. Hydrodemolition can cover 90 to 100 sq. ft. per hour, as opposed to 5 to 10 sq. ft. per hour for each jackhammer. As noise does not restrict the work to specific times of operation, the repairs can be complete quickly and thereby minimize down-time losses and inconvenience to the client.
One of the disadvantages of the process stems from the large quantities of water involved. It is necessary to have a dedicated supply line and sufficient drainage capacity to dispose of the used water. Furthermore, water can have poor effects on the existing concrete as moisture and chloride contaminated in the concrete will create a high potential for corrosion of the reinforcing steel.
Hydrodemolition represents the state of the art in concrete repair technology. It allows for significantly higher bond strengths than those obtained from conventional jackhammering and epoxy bounding. The quietness of this operation and lack of surface bond vibration make hydrodemolition an advantage for noise-sensitive regions such as office buildings and residential apartments. The rapid operation and the possibility of working extended shifts enable the repairs to be completed more rapidly, thereby reducing down-time.
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Walters Forensic Engineering | 277 Wellington
Street West, Suite 800 | Toronto, ON M5V 3H2