By: Jim Quinn
A new, patented technology promises to introduce significant cost, labor and time savings—as well as quality and safety enhancements—into the process of retrofitting the nation’s concrete highways with load-transferring dowel bars.
Using an array of precision-controlled water-blast nozzles, a prototype of the Simply Complex machine by WaterWerks Inc. has proved the viability of its design in simultaneously cutting up to six slots in concrete highway sections, enabling the precise placement of steel dowel bars that reinforce and stabilize adjacent pavement slabs. The machine was designed to combine three jobs into one: precision cutting of dowel-bar slots, excavating the cut concrete and vacuuming the water and concrete debris into a storage tank for reprocessing and reuse.
A prototype has been demonstrated in front of the Washington State Department of Transportation, resulting in supportive suggestions to improve the design, as well as an enthusiastic endorsement of the technique from the state DOT’s pavement design engineer. The state DOTs of Washington, California, Texas and Minnesota are studying alternatives for dowel-bar retrofit (DBR). All four states have committed to approve use of the design on projects their DOTs manage when a commercial version is available.
It is estimated that the water-blasting technique could reduce by more than half the cost of cutting and cleaning concrete slots in DBR projects to an average of just $16.25 per slot from the current average of $34 per slot, including the costs of equipment, labor and supplies.
Key to the water-blasting operation will be the use of off-the-shelf microprocessor-based industrial controls programmed to enable the machine operator to cut precise slots straddling two adjacent wheel paths in the concrete pavement.
The system can use high-pressure water-blast nozzles and vacuum equipment utilized up to pressures of 40,000 psi.
Working the slots
In addition to the obvious cost-reduction benefits, the water-blasting DBR system also promises to deliver important technical, maintenance, safety and environmental benefits.
From a technical standpoint, the system takes less than four minutes to produce six dowel-bar slots, typically 21?2 in. wide, 21 in. long and 53?4 in. deep, but fully customizable per state specifications.
