Hydrodemolition, faster than a jackhammer, produces a better surface for concrete repair and protective coatings. Most hydrodemolition work is on parking garage and bridge deck restorations. But concrete restoration of condominiums, high-rise buildings (especially in salt environments), silos, and tunnels is also increasing. The use of water-jetting equipment is fast, worker friendly, and nonpolluting.
Removing paint, epoxy, and other coatings from concrete surfaces is easy with hydrodemolition equipment. Sometimes coatings can't be removed by any other means.
Concrete as thick as 5 feet can be cut in one pass with water-jet cutters. Costs typically run between $200 and $400 per hour, making this a more expensive option than sawing. For this reason, cutting with water is often reserved for difficult projects where other solutions are impractical or not possible.
Scarifying is becoming more popular with contractors. A single-jet nozzle traveling at a rate faster than that for hydrodemolition provides a good bonding surface for new concrete. The rough, irregular profile cut by the water produces a superior mechanical bond, and there is no microcracking (or bruising) caused by the demolition.
Hydrodemolition to prepare concrete for restoration work has been available for about 20 years in the United States. Water pressures ranging from 10,000 psi to 40,000 psi at 15 to 100 gallons per minute provide the cutting power. A typical hydrodemolition project requires 2 to 4 inches of concrete removal. At present there is no consensus whether or not this process should be performed on post-tensioned structures.
Cleanup and water disposal are the biggest problems of hydrodemolition. The depth of demolition is another sensitive area requiring better definition. Dependable schedules are important to specifiers. And there must be understanding, before the job begins, about how to handle noise from the truck-mounted pumps and demolition nozzles if and when it becomes an issue.