THE EFFECT OF PAVER SPEED ON ROLLER REQUIREMENTS

THE SPECIFICATIONS OF MANY AGENCIES BASE THE NUMBER OF ROLLERS REQUIRED ON AN ASPHALT PAVING JOB ON THE TONS OF MIX LAID PER HOUR. OTHERS HAVE SHOWN THAT THICK LIFTS ARE EASIER TO COMPACT THAN THIN LIFTS, AND THUS ADDITIONAL ROLLERS ARE NOT NEEDED JUST BECAUSE THE LIFT IS THICK, A COMMON CONDITION THAT PRODUCES A HIGH RATE OF LAYDOWN IN TERMS OF TONNAGE. OTHER AUTHORITIES HAVE NOTED THAT, IF DENSITY IS TO BE OBTAINED DURING ROLLING, THE INITIAL ROLLING, USUALLY CALLED THE BREAKDOWN ROLLING, MUST BE APPLIED BEFORE THE MAT HAS COOLED BELOW A CERTAIN TEMPERATURE. THIN MATS COOL FASTER THAN THICK MATS; ALSO, THIN MATS PERMIT FASTER PAVING SPEEDS THAN THICK MATS FOR A GIVEN NUMBER OF TONS PER HOUR OF PRODUCTION. IT APPEARS LOGICAL THAT ROLLER REQUIREMENTS SHOULD ENSURE THAT THE MAT CAN BE ROLLED BEFORE IT COOLS TOO MUCH. THE TIME REQUIRED TO ROLL A GIVEN AREA OF PAVEMENT WITH A ROLLER OPERATING AT A GIVEN SPEED CAN BE COMPUTED. BECAUSE THE PAVER OPERATION IS CONTINUOUS, THE PAVER MOVES AHEAD WHILE THE MAT JUST LAID IS BEING ROLLED OUT. IF THE PAVER IS MOVING SLOW ENOUGH THE ROLLER CAN KEEP UP, BUT IF THE PAVER IS MOVING TOO FAST IT WILL LEAVE THE ROLLER BEHIND. A FORMULA IS PRESENTED FOR MATING THE PAVER SPEED WITH THE ROLLER SO THAT THE ROLLER CAN JUST KEEP UP WITH THE PAVER. CHARTS ARE PRESENTED, BASED ON THE FORMULA, FOR APPLYING 2, 3, AND 4 PASSES OF BREAKDOWN ROLLING WITH 1, 2, AND 3 ROLLERS WITHIN TIME PERIODS UP TO 18 MINUTES (MOST MATS WILL HAVE COOLED TOO MUCH BY THEN). THE FINDINGS BY OTHERS CITED IN THE PAPER PLUS THE COMPUTATIONS PRESENTED IN THE PAPER JUSTIFY THE CONCLUSION THAT ROLLER REQUIREMENTS SHOULD BE BASED ON PAVER SPEEDS RATHER THAN TONNAGE RATES. /AUTHOR/