Asphalt pavers are essential tools in modern road construction, helping ensure pavements are laid precisely and quickly. However, understanding their inner workings may be challenging. The Amazing fact about Fairfax asphalt.
Rubber-tracked pavers use rubber-tracked pavers to spread, shape, and compact “asphaltic concrete,” made up of various formulations of graded aggregate and liquid asphalt. A conveyor tunnel and auger system move hot mix asphalt (HMA). Additionally, they utilize a roller to compact HMA before surface finishing and compaction.
Tractor
Asphalt pavers are an integral piece of machinery in any paving job, responsible for spreading and leveling asphalt across any project site. Therefore, understanding this piece of machinery is of great significance for professionals working on pavement jobs.
Pavers use either tires or tracks to self-propel across surfaces, and most models feature two parts—the screed and tractor—that work together. The tractor controls the movement of the paver while its screed shapes and compacts the asphalt layer—many are capable of laying up to 7.5 feet of asphalt in one pass!
A hopper acts as temporary storage for hot mix asphalt (HMA) delivered by transport vehicles, accommodating fluctuating material needs arising from changes to road grades, utility access openings, or intersection shapes. When equipped with inserts to expand capacity for HMA storage needs caused by changing road grades or utility access openings, this device can accommodate fluctuating material demands through changing road grades, utility access openings, or intersection shapes.
Once the hopper has been filled, feeder conveyors transport it directly to the paver’s back for distribution via augers. You can customize their width according to application – for instance, a pathway requires narrower augers than wide roads for optimal results. Some asphalt pavers even come equipped with front or rear-extender options to create more even surfaces.
Safety requires familiarizing oneself with an asphalt paver’s functions. Furthermore, it is paramount to be aware of one’s environment on the worksite and take precautions against potential hazards like moving traffic. Thus, before operating any piece of paving equipment, it is necessary to follow the guidelines set out in the paver operator manual and receive training.
Along with routine maintenance, it is also vital to regularly inspect a paver for any issues that might arise. For instance, dirty, improperly adjusted, or poorly lubricated hopper or conveyor chain components could result in damage; regular inspection and upkeep will reduce this risk as well as enhance performance on job sites.
Screed
Asphalt pavers are driven by either a diesel, gasoline, or electric engine. Wheeled or tracked tractor components power the screed, which levels and shapes the asphalt mixture as it’s being laid down—moldboards, vibrators, endplates, and slope sensors all work as part of its design. A paver’s hopper holds asphalt mix as it comes from trucks through conveyor systems before reaching its end destination—the screed.
Maintaining consistent asphalt mat leveling during paving is vital to meeting project specifications and providing maximum quality. Control systems like mechanical sensors, ultrasonic non-contact sensors, laser systems, and 3D leveling were created to help maintain an even layer of material; however, mistakes still happen occasionally.
One of the more costly mistakes is running low on material in your auger chamber (commonly referred to as “diving”). This occurs when the crew operates the screed with an inadequate head of material, resulting in an irregular dip of bitumen. This dip limits how much material your paver can lay out and creates an uneven mat surface.
Other factors which may contribute to inconsistency in asphalt leveling include:
Hopper & Conveyor System
An asphalt paver’s hopper is a large container located at its front that stores hot mix asphalt before being transferred by conveyor chains to its screed for spreading onto roadways. This hopper can be filled either from truck deliveries or through its feeder; when needed, its hydraulically folding wings expand capacity by making room for dump trucks passing underneath it.
The conveyor system consists of heavy-duty chains and flight bars connected by belts that transport asphalt mix from its hopper to a screed. This system is controlled via paddles or switches for automated feed control. The conveyor system must be monitored closely to ensure accurate metering of asphalt mix to the screed to maintain a uniform mat. Furthermore, providing the hopper does not empty during paving is of critical importance. Doing so may cause any remaining cold, large aggregate in the hopper to slide onto a conveyor in an uneven mass before dispersion into the mat, creating texture differences, premature wear on plates, and isolated low areas in its final product.
Hopper & Conveyor System
An asphalt paver’s hopper and conveyor system stores and delivers paving material to augers and screeds. A hopper serves as a receiving bin for asphalt from external sources like dump trucks. From there, it travels via conveyor to its final destination in the rear of the machine, where it will be used during paving processes.
The conveyor system consists of heavy-duty chains and flight bars that move asphalt material along tracks across the width of a paver’s pave bed. Distributing augers attached to this conveyor are responsible for evenly dispensing asphalt material across its width across paved surfaces; depending on their design, they can either operate independently or jointly.
Precise material flow is critical for achieving the desired thickness and finish of an asphalt surface, and modern paving machines feature advanced electronic systems designed to monitor material flows and adjust them as necessary to ensure consistency and prevent issues like aggregate segregation that could otherwise lead to bumpy and wavey final pavement surfaces.
Vibrations and jostling from vehicle transportation tend to separate coarse and fine fractions of asphalt within the truck bed, leading to temperature variations throughout the paving mixture. This ultimately diminishes the quality of finished pavements. While some material transfer vehicles contain mechanisms for re-mixing and heating their asphalt loads, segregation remains an issue on many projects.
Once the asphalt has been loaded into a hopper, it is then heated to its ideal temperature for paving using either propane burners or electric heaters. Furthermore, both the hopper and conveyor systems contain controls to monitor and regulate asphalt distribution across surfaces being paved; automated systems detect any clogs or jams and help eliminate waste or delays on job sites. Additional automation features may include a mobile reference system – typically consisting of either an attached beam or tube that travels with the paver vehicle and measures road elevation using either physical touches or ultrasonic pulses to determine distance – for measuring road elevation measurement purposes.
Manual Grade Manipulation
A paver utilizes several systems that work together to lay HMA on the road, such as its hopper, conveyors, augers, screed, depth crank, heater, and vibrator. The hopper is filled with mix and then distributed across the screed’s front to form a mat. A combination of conveyors and augers on either side of the paver determines how much material is being applied at any one time. To ensure optimal placement and compaction, the hopper must remain full to provide enough head of mix against the screed for adequate placement and compaction. If too much mix drops off suddenly, segregation could occur, and its wings folded to move material from sides to center, but this should only be done sparingly as this will cool its head of material over time.
Temperature monitoring on asphalt being placed by pavers can be accomplished using either thermal profiles or non-contact sonic sensors, which use sound pulses to identify elevation. If a paver stops for an extended period, its asphalt may cool significantly, making it harder for restarted machines to achieve adequate density levels.
Some areas of pavement will be too thick for a paver to lay, necessitating manual placement of the mix. Any lumps or crusts formed should be broken up prior to hand placement. In areas that the paver cannot reach due to obstructions in expected wheel paths, warning signs and flaggers must be placed to deter traffic away from these locations while work continues.
HMA paving aims to complete construction as quickly and as closely as possible to achieve an optimum design in one pass, so the entire operation must run in unison between tractor, screed, and conveyor system synchronization – any deviation will lead to inferior finished products.
