CONCRETE PAVING PRODUCTIVITY IMPROVEMENT USING A MULTI-TASK AUTONOMOUS ROBOT
ABSTRACT To improve productivity in conventional concrete construction, autonomous robots that perform specific tasks are being developed. Single-task robots are capable of enhancing specific functions, though their impact on the overall productivity remains unclear. A robot that incorporates each task-specific piece of machinery used in the concrete paving process into one fully autonomous unit is evaluated. Assessing potential productivity from the use of a fully automated process is a required step for developing a full scale-system. With the purpose of identifying productivity benefits in an automated concrete paving operation, two concrete paving processes will be compared using simulation tools. One process is the conventional operation using intensive labour, slip form paving machine and auxiliary equipment. The other process is the automated operation using a fully autonomous robot. Applications of this assessment methodology based in simulation will allow for the determination of productivity indicators of automated operations in hazardous environments, using the respective results to complement prototypical tests.
Stringless Portland Cement Concrete Paving
This paper describes results from a study evaluating stringless paving using a combination of global positioning and laser technologies. A concrete paver manufacturer and a machine guidance solution provider developed this technology and successfully implemented it on construction earthmoving and grading projects. Concrete paving is a new area for considering this technology. A concrete paving contractor in Iowa agreed to test the stringless paving technology on two challenging concrete paving projects located in Washington County, Iowa during the summer of 2003. The research team from Iowa State University monitored the guidance and elevation conformance to the original design. They employed a combination of physical depth checks, surface location and elevation surveys, concrete yield checks, and physical survey of the control stakes and string line elevations. A final check on profile of the pavement surface was accomplished by the use of the Iowa Department of Transportation Light Weight Surface Analyzer. Due to the speed of paving and the rapid changes in terrain, the laser technology was abandoned for this project. Total control of the guidance and elevation controls on the slip form paver were moved from string line to a global positioning system (GPS). Results indicate that GPS control is a feasible approach to controlling a concrete paver. Further enhancements are needed in the physical features of the slip form paver hydraulic system controls and in the computer program for controlling elevation.
Stringline Effects on Concrete Pavement Construction
Modern concrete pavement construction typically uses slipform paving equipment, especially on major highways and airfields. This equipment commonly is guided by its sensing of a stringline set in advance by an engineering survey. Although use of stringline guidance has improved the smoothness of pavement, some limitations of this technique are known to exist. Three of these limitations are explored in detail. The effects on concrete pavement smoothness from the chord effect, the sag effect, and random survey error are described both conceptually and analytically. Of these three effects, random error introduced during the engineering survey is found to be the most pronounced. Furthermore, this analysis shows that contradictions exist within what is sometimes considered good practice for concrete pavement construction; the belief that improved smoothness can be obtained by simply using shorter spacing of the stringline stakes is not always correct. In fact, it is demonstrated that optimum stringline spacing can be realized by recognizing each of the effects described, including the associated costs of mitigation.