Thinking Your Way to Optimum Destiny
For both soil and asphalt rollers, today's intelligent compaction (IC) uses machines that sense the degree of compaction beneath the drum, and vary compactive force to get density. Now, this capability is combined with global positioning system (GPS) technology to create a real-time database of densities obtained anywhere on a pass, with the ability to log the number of passes and the temperature of the mat, anywhere on that mat, on any pass. Intelligent rollers have the ability to make and execute an appropriate decision based on the analysis of col-lected information. They measure material stiffness data during compaction, analyze that information, and make a decision how to adjust the vibratory drum to optimize compaction. Conversely, conventional compaction has limitations. It provides little or no feedback on the fly. Corings for den-sity measurement are not analyzed until after compaction, and may not be representative of the entire section. Over-compaction can occur. In the short term, intelligent compaction can improve density for better performance, improve construction ef-ficiency for cost savings, and increase construction infor-mation for better quality control and quality assurance. The Human Factor But the burden of being right still falls on the opera-tor, who must balance the demands of new mixes and equipment technologies against the variables of weather, variations in plant mix, and out of spec mixes caused by everything from plant errors to traffic jams to make a pavement meet density. And while intelligent compaction technology now in development is changing the way rollers will operate in the future, in the quest for optimum density today, there is still no substitute for the kind of human experience that years in the operator's station brings. A well-trained and experienced operator is better able to adjust to the ever-changing conditions encountered on construction projects than the computer-aided compac-tor, says Dale Starry, director, strategic technologies, for Bomag Construction Products. An experienced operator is more adept at adjusting the performance of the com-pactor to achieve needed results, especially when unpre-dicted construction delays are experienced. Just as a seasoned airplane pilot takes command from the auto pilot system when turbulence or other conditions are encountered, Starry continues, an experienced com-pactor operator is able to adjust the operating character-istics of the machine when the changing conditions of the material call on that operator to do so. An experienced operator reacts to jobsite variables and compensates for changes to materials that allow con-struction to continue on schedule, which is important on any high-volume project, Starry says. For example, an experienced operator sees when soils are too dry or too wet and adjusts the operation of the compactor, he says. The experienced operator can also alert other personnel onsite that material modifications are needed. The intelligent compactor does not possess this ability, he says. The computer on the machine can only react based on pre-programmed algorithms, Starry says. If the measured dynamic stiffness modulus for the soil is too low, the intelligent compactor will adjust itself to generate more force, or require additional passes over the material in an attempt to increase its stiffness modulus. If this soil is too wet, more compaction force and more passes only N ew technologies and high-performance compaction equipment are making it easier for roadbuilders to attain optimum density for road bases and asphalt mats without damaging what's below. >>> RoadScienceTutorial Intelligent Compaction (IC) comes from both intelligent machines and intelligent operators. Get Smart By Tom Kuennen, Contributing Editor 20 November 2009 Better Roads Want Optimum Density?