Paving Perfect Residential and Commercial Jobs
BY AsphaltPro Staff
Part Three of AsphaltPro’s “Best Practices for Residential and Commercial Paving” series. Read Part One here, and read Part Two here.
Commercial and residential paving presents its own unique challenges compared to highway paving jobs. Instead of paving long, straight passes, residential and commercial paving crews are often paving short passes and working around parking islands. Although the jobs may be different, there are still best practices to follow when paving residential and commercial jobs to ensure a high quality mat.
At World of Asphalt 2019, Brian Hall presented a seminar of best practices for residential and commercial paving. Hall, a territory manager with LeeBoy, Lincolnton, North Carolina, visits up to a dozen paving jobs each week.
“No matter where you are, there are DOT guidelines of how parking lots should be made, and that’s what we’re following today,” Hall said.
Here, we share some of the insight Hall presented in the final installment of a three-part series devoted to best paving practices for residential and commercial jobs. Read Part One here, and read Part Two here.
Get Depth Done Right
There are three ways to start at the right depth. Skilled operators can start from zero, putting the screed on the ground, letting the asphalt come under it with a positive angle of attack and coming up to the right depth. However, most operators may not be able to do this, so they use a starting pad or starting blocks.
The crew can build a starting pad by dropping enough asphalt for the lute guys to level out to create a pad the same width as the screed and the same depth that the finished product should be. Then, set the screed down on the pad to get started. If using starting blocks, ensure the wood is cut to the exact right depth, float the screed down on the blocks and take off from there. Find the null point in the screed so there’s no pressure on either side, then crank until you feel resistance to introduce some angle of attack.
Any time the speed, angle of attack or head of material changes, it will affect the depth of the mat.
If the speed changes, the shear factor–the point at which the head of material is cut off by the screed–will change, so the depth will change. At an increased speed, the shear factor decreases and the depth decreases. When speed decreases, the shear factor increases, as does the depth.
The angle of attack is the angle at which the screed meets the asphalt. It is adjusted with electric screws, hydraulic screws, or manual screws. If increased, more material passes under and the screed rises. It will then reach an equilibrium and resume the original angle of attack. However, it takes five tow arm lengths for the screed to fully react to the change. While continuously adjusting the screw may make it appear the operator is working hard, Hall said, it’s actually ruining the mat. If the paving speed, mix, and grade doesn’t change, the angle of attack also should not have to change.
Pro Tip: About 60 percent of your change will take place as you travel one paver length of distance. The rest of your change takes the next four paver lengths. Give the change time to occur in your mat.
The head of material is the amount of material ahead of the screed. The correct head of material is usually half of the way up the augers. This creates resistance against the screed. Constant resistance will result in constant depth. If the head of material decreases, the depth decreases. If the head of material increases, the depth increases. That’s why many of today’s pavers have sonic augers and automatic conveyors to help maintain a consistent head of material.
The joint is where the new pass meets the previous pass.
When constructing a hot joint, the roller operator must keep the roller off the edge. Hall recommends a distance about the same width as the endgate shoe. Then, on the following pass, the crew will put the end gate flush on that uncompacted edge of the previous pass. Be sure to spray it first so it doesn’t pick up the material. Raise or lower it according to grade, or use an automatic joint matcher. When the roller hits that joint between the first and second pass, it will knead everything together.
A cold joint is when those adjoining passes are done on two different days. You will need to overlap the edge of the previous pass by a couple inches when rolling. You will need to allow an extra ¼ of an inch depth per inch of compacted depth, since the other pass has already been compacted.
Pave Like a Pro
Paving in a straight line sounds simple, but it’s always important to have help. All paving operators should have a guide to help them drive straight. Hall recommends placing that guide as far out as possible without it getting in the way of the haul trucks so the paver operator has a longer line of sight.
“The farther you’re looking down the road, the straighter you’re going to pave,” Hall said.
Roll & Rock
We roll to achieve the density specified for the project. What you’re looking for is a minimal amount of air voids in the asphalt.
There are three phases to rolling: breakdown, intermediate and final. Breakdown offers primary compaction and aggregate movement, intermediate offers some additional compaction and binder movement, and finish offers minimal additional compaction and a smooth surface. Hall said breakdown and finish rolling is done with steel drum rollers, while the intermediate is done with a pneumatic roller.
Hall recommends using the Minnesota Department of Transportation’s PaveCool 3.0 tool to determine how long after paving before rolling should begin and when it should end. Regardless, roller operators should have a sense of urgency in most instances, Hall said.
Pro Tip: The screed operator for one contractor Hall has worked with attached a string to the screed to set a minimum distance for roller operators to stay behind the screed.
The speed at which the roller operator travels, along with drum and lane width, will impact the number of passes he should make. The example Hall offered is this: to achieve 98 percent density, the operator would need to roll six passes at a speed of 500 feet per minute or two passes at a speed of 300 feet per minute.
When rolling against the curb, Hall recommends keeping the edge of the roller on the curb.
“Originally, I thought the curb would lift the roller up so it wouldn’t get density against the curb,” Hall said. “But since you’re trying to get water to flow to the curb, if you keep the roller off the curb, you’ll create a ridge and the water won’t make it to the curb.”
However, Hall adds, the density at the curb will suffer, so he recommends tilting the paver endgate up a bit to allow a little extra asphalt at the curb.
Before the last load of the day, Hall recommends spraying the paver with an approved release agent. That way, when the last truck full of hot asphalt hits the paver, any stuck asphalt should slip right off.
At the end of the shift, remove all excess asphalt from the paver, clean and spray all components, run the conveyors while spraying with release agent, spray the auger chains and conveyor chains, refuel the machine and grease all parts.
“If you don’t schedule time for maintenance, your equipment will schedule it for you,” Hall said. He also recommends backing the paver onto the trailer and never letting the screed bump the trailer or drag on the ground. Loading boards may be necessary.
Leave Customers Satisfied
“Your company’s success depends on word of mouth,” Hall said. “The customer has questions and you have answers. Involve them in the process.”
He recommends designating one crew member to talk to the customer. If the customer comes out and asks the crew to do something extra and he says they will but doesn’t communicate that to whomever needs to do it, the customer won’t be happy.
The entire crew should respect the property. Keep your tools organized. Respect the people working or shopping at your commercial projects. Keep your trucks clean. They represent your company. Walk or ride the job, make a punch list before the customer does, and follow up to make sure the job is done to the customer’s satisfaction.