Wirtgen Group has announced a major automation upgrade to its SP 1500 slipform pavers, integrating a dual-terrestrial laser scanning system that completely eliminates the need for physical string-lines in concrete barrier and curb construction. Traditional slipforming requires surveyors to install a taut string-line along the entire length of the pour, which the machine's sonic sensors follow to establish the elevation and steering alignment. This string-line is highly vulnerable to wind vibrations, accidental knocks by site vehicles, and thermal expansion, all of which cause visible deviations in the final concrete surface.
Wirtgen's new system replaces the physical line with a digital reference. Two high-speed 2D laser scanners are mounted on the paver's mold, one looking ahead and one looking down. The forward scanner reads the existing milled subbase or adjacent pavement, creating a continuous topographical profile. This data is fed into the machine's 3D control module, which compares the existing surface against the project's BIM (Building Information Modeling) design model.
The control module then makes micro-adjustments to the hydraulic steering cylinders and the mold's elevation cylinders up to 20 times per second. If the scanner detects a localized dip in the subbase, the mold automatically lowers to maintain the exact specified barrier height without operator intervention. The rear-facing scanner simultaneously verifies the profile of the freshly poured concrete, closing the feedback loop to ensure zero deviation.
By removing the string-line, contractors can eliminate days of pre-pour surveying and grading setup. During a recent 12-mile highway median barrier project, the automated slipform paver operated at a continuous 15 feet per minute, achieving a vertical tolerance of less than 3 millimeters without a single physical guide wire in place.
