Training
Prevent Callbacks for Pavement Slippage T
The theme this month incorporates quality control/quality assurance (QC/QA), which often employs tools to ensure the surface course that you pave is rolled to its best density. No matter how perfectly you match density specs, you can damage a new surface course’s chances for long life if you don’t adhere it to the base correctly. One of the reasons a contractor might be called back to repair a job for the county or other agency is that the new pavement surface is slipping or shoving. Not only does a raveling pavement section look bad for our industry, but it also promises to let moisture into the layers of the pavement structure below. To avoid pavement slippage, the contractor wants the crew to follow best practices from the start of the job to the finish. As with all projects, make sure you wear personal protective equipment (PPE) in the field. I also recommend milling crews use headsets to help with safe and efficient communication.
MILL BEST PRACTICES
Let’s say the project is a mill-and-fill. Before the milling crew even begins the job, members of the crew want to inspect the piece of equipment. Make sure the mirrors are in good condition and the backup camera is working for safe operation. Then check the teeth and cutting drum specifically for wear or missing tools. Make sure all the teeth are the same brand and type/ material to ensure a consistent cut. Look at the entire cutter drum housing. The door behind the cutter moves up and down, similar to an endgate on the paver, to keep the chunks and fines in rotation with the drum. If this door is worn or damaged, material will sneak out, causing more work for the sweeping team than necessary. Also double-check the endgates on the side of the housing to ensure excess material won't bleed out from these areas. You want the frame of the tractor to be tight and in good repair.
18 // September 2021
In this picture, you can see the whole crew is part of the cleaning and routine maintenance of the equipment. Using environmentally friendly release agents to assist, use rags and putty knives to get asphalt and other debris off push rollers, endgates, and all the components that need to move freely and smoothly for best paving performance. Notice also that the milling crew has left a fairly consistent groove pattern for the paving crew to tack and pave on top of. The best way to doublecheck that this milled surface is, in fact, free of dips or slope is to place the straight edge down and do some measuring. The straight edge is your best quality control tool to double-check your numbers and guard your yield on the job. Check out the article “Train Proper Straight Edge Use” for some quick tips on its use. In addition to setting up the cold planer to achieve a surface with the specified grade and slope, the operator will set it up to move forward at a consistent, reasonable speed. We must go at a consistent speed to keep the rotation of the cutter consistent. Altering the rotation by gunning the engine or trying to race the clock will cause the cutter to rip and tear up the pavement instead of cutting a smooth and even groove. The operator also wants to see a guide bar on the mill, just like the paver operator wants a guide bar on the paver. We must follow a straight line when milling down the lane so the grooves follow a straight line. This will make brooming easier. Look to the watering system as well. You want to ensure the tips are all the same and
working correctly for the speed at which you’ll operate. The watering system will be a mist to keep dust down without turning the dust into a coagulated paste that the milling machine can’t pick up and the brooms will have to fight. There are more tips for milling machine maintenance and milling success in the article “Easy Cold Mill Start-up Begins the Night Before” on TheAsphaltPro.com. Once you begin milling, look back every now and then to double-check your work. The readings on the control panel may tell you you’re milling at a depth of 1.5 inches but placing a 4-foot level down and using a ruler or tape measure to check your depth will show whether you’re actually at 1.5 inches or at 2 inches—or worse. Make sure your controls are reading correctly.
