The curb placement was characterized by several obstacles. For instance, several concrete light bases were located only about an inch from the curb, and Green River had to place concrete around them. To do this, the contractor had to swing the sonic sensor away from the stringline, which caused signal loss. The finished curb work did not show any variation in elevation next to the light bases, though. For corner work, the hopper’s 20-inch lift came in handy. The machine slipformed curb up to a corner and backed up, leaving a 90-degree curb for the next section that was placed at a right angle. The machine could then back up to within about a foot of the last placement and resume slipforming.
“The Topcon system was instrumental in maintaining the proper height on the curb,” Taylor said. “Technically, it was a fairly difficult job, given the height of the curb, the fact that it was down in a ditch and the radiuses. The cross-slope varied quite a bit, so we just set the machine at a percentage of slope that would keep the machine auger from touching the pavement and maintain the same profile all the way around the turns.”
Automated grade control was particularly useful in one roughly 100-foot section of the parking lot where 10-foot sections of pavement had been excavated for removal of drainage lines and utilities. Road base material had been placed in the excavated section, but it was raining when the curb installation took place and the grade dropped a couple of inches. The machine was still able to maintain the top of the curb and cross-slope along this section, though.
As it happened, Green River placed an average of 10 feet of curb per minute, although the curb work did not occur continuously. The contractor completed the project in five days, including the day of training for Hawkins. Only one other worker was needed, communicating with the ready-mixed concrete truck driver from the front of the machine.
Don Talend of Write Results Inc., West Dundee, Ill., is a print and e-content developer specializing in covering construction and geospatial topics.