Smooth and level pavement surfaces are critical.
This article is the first of a four-part series on paving provided by Volvo Construction Equipment.
Successful asphalt paving projects don’t happen by accident. They are the result of careful planning and proper preparation. From proper paver setup to achieving optimum mat temperature and conducting the rolling pattern at just the right time — each step in the process will affect the next. And attention to detail throughout the process can mean the difference between getting a bonus and being delayed.
In this four-part series, key considerations will be addressed throughout each step of the paving process, starting with paver setup. Ensuring that the paver is ready to work and in top condition is key to the overall success of a roadbuilding project.
Proper Paver, Smooth Pavement
Smooth and level pavement surfaces are critical. In fact, many paving projects awarded by agencies across the United States and Canada include bonuses for achieving specified pavement surface smoothness. This is why it’s essential to visually inspect the paving machine and components to look for any issues that could affect operation or safety before the hot mix goes into the hopper.
Prior to start-up, check all fluid levels. Start up the paver and then check all gauges. Apply a release agent or coating solution to any components that come into contact with asphalt. This lubricant helps prevent asphalt from sticking to bare metal parts.
Some paver manufacturers have developed integrated coating systems that can be operated through the machine, as well as biodegradable lubricants. Volvo pavers, for example, utilize Blaw-Kote, an environmentally friendly protective coating system that can be used on the complete machine and if equipped can be applied to the tracks with the push of a button.
This coating should be applied to all areas that come in contact with asphalt, including the hopper, conveyors, auger, screed extensions and end gates. This important step should be repeated throughout the day — before beginning operation, when switching mix types and at the end of the workday.
Proper machine preparation and screed setup can save time and effort. Set up the screed paving components to the project specs — width, mat thickness, crown or slope.
Preheat the screed to prevent mat sticking and dragging. A temperature range of 225 to 275F (107 to 135C) is appropriate to prevent most material from sticking and causing damage to the screed plate, frame and other parts often caused by excessive overheating.
“There is a misconception that hotter is better when it comes to heating the screed,” said Chris Connolly, operator training specialist of Volvo Construction Equipment. “If you’re overheating the screed, you’re putting immense wear on the machine, as well as using extra fuel.”
Best practices call for the range of 225 to 275F when using most common mixes.
Angle of Attack
Establish the screed-plate “angle of attack” by rotating the depth cranks up or down to achieve the desired paving depth. The angle of attack determines the mat thickness. Adjusting the screed — raising or lowering — will increase or decrease the mat thickness. The mat depth is established by a project engineer who determines the estimated usage and traffic volume for the intended pavement.
Adjust augers to a minimum of 2 in. (5 cm) above the top of the mat to be paved. Most highway-class pavers are equipped with adjustable auger height.
“You want the auger slightly higher than the mat you’re laying so the auger isn’t digging into the material that’s passing under the screed,” said Connolly. “This will prevent shadowing, some other mat defects or a rough texture from occurring.”
Remove the slack between the paver tractor and screed by moving the paver ahead slightly until the screed moves in tow.
At this point, the material transport vehicle (MTV), dump truck, or belly dump and windrow elevator supplies hot mix material to the hopper and the feed system is activated. A hopper that is at least a third full of hot mix material at all times is ideal.
“Having the hopper at least a third full gives you a little buffer,” said Connolly. “If you get below that level, you could run out of material very quickly. Then the screed will drop, you’ll have a hole in the mat and you’ll have to start over again.”
Communication between the paver operator and truck driver is essential to maintaining an appropriate level of material in the hopper.
With setup complete and hot mix material in the hopper, paving can begin.
Part 1: Precision Paving Begins With Proper Equipment Setup
Part 2: Precision Asphalt Paving 101: Laying a Quality Mat
Part 3: Precision Asphalt Paving: Best Practices for Compaction
Part 4: Precision Asphalt Paving — Rolling Pattern, Safety
Part 5: Past, Present and Future of Intelligent Compaction