Your Competitors Are Adopting 3D Asphalt Paving and So Should You

Economic, regulatory and labor conditions favor automation, and progressive contractors need to go the extra mile to compete

Topcon 3d
Topcon Positioning Systems

Conditions are pushing asphalt paving contractors to adopt automation widely in order to meet federal mandates, cope with a labor shortage and just complete the volume of work that will come as a result of the Infrastructure Investment and Jobs Act (IIJA).

The IIJA  increases the national investment by 55% over and above the 2015 Fixing America’s Surface Transportation Act baseline, and the National Asphalt Pavement Association projects that each state will receive more than $1 billion total in Federal Highway Administration (FHWA) funding to repair and improve roads and bridges. Within the IIJA is the Surface Transportation Reauthorization Act of 2021, that allocates a record amount of highway and bridge funding. These dollars will be heavily loaded towards repair of existing assets, making blacktopping and resurfacing core disciplines that will be in demand. The IIJA also includes verbiage that makes clear work performed under the bill should use advanced construction technologies:

“The Secretary shall establish and implement a program under the technology and innovation deployment program established under paragraph (1) to promote, implement, deploy, demonstrate, showcase, support, and document the application of advanced digital construction management systems, practices, performance, and benefits … The goals of the accelerated implementation and deployment of advanced digital construction management systems program established under subparagraph (A) shall include--

(i) accelerated State adoption of advanced digital construction management systems applied throughout the construction lifecycle (including through the design and engineering, construction, and operations phases) that--

(I) maximize interoperability with other systems, products, tools, or applications;

(II) boost productivity;

(III) manage complexity;

(IV) reduce project delays and cost overruns; and

(V) enhance safety and quality;”

Even before passage of the IIJA though, longstanding guidance from the FHWA advocated for the use of automated screed control whenever possible on thin hot-mix asphalt overlay. Recent requests for proposals for highway projects at all levels of government are increasingly also mandating use of pavers with automatic screed controls and sensors on both sides of the paver. The controls, according to some of these mandates, should sense the grade from an outside reference line, sensing the transverse slope of the screen and provide automatic signals that operate the screed to maintain the desired grade and transvers slope within plus or minus 0.1%.

What this means is that 2D automated screed control is almost a no-brainer as each time you adjust the screed manually, it takes several paver lengths to get to the new level. And the operator may not get it right at first, and some titration up and down causes waves in the pavement, which in turn results in expensive grinding and rework.

2D screed control on asphalt pavers has become commoditized, and in order to differentiate themselves, paving contractors may need to adopt even more advanced technology that limits waste and reduces labor requirements as inputs are constrained and rising in cost. Asphalt binder costs have increased 100% between 2020 and 2021, even before the current embargo of Russian oil sent crude prices well over $100 per barrel.  A 2021 U.S. Chamber of Commerce study found that 88% of contractors are facing a labor shortage, forcing them to pull back from projects they otherwise would accept.

3D Paving Automation is the Answer

3D stringless paving is one way asphalt contractors are going one better than their field of competitors while cutting costs and shaving days off the project timeline. 3D paving is now reliable and mainstream, with the technology having been proven in earthworks and then seeing early adoption on high-value paving projects in the early 2000s.

In a 3D paving environment, an array of total stations typically lock onto receivers on 3D paving-equipped machines—pavers, rollers and milling machines—through a prism mounted on each machine. 3D paving controls on each machine contain a digital model of the job, enabling the equipment to deliver on the model automatically including slope, crossfall and even compaction density.

The trailing gate of the paver is also typically sensored, automating as-built inspection and reporting.

“2D grade control is now relatively common,” Trimble General Manager of Civil and Specialty Solutions Kevin Garcia said. “Asphalt paving contractors come to us now to learn about 3D … there is a big differentiator between 3D and things past. With 3D we are talking about variable depth paving, and it can very quickly change the depth of the pavement and conceivably the cross slope if needed, if you are going into a superelevated curve. It does not require paint markings on the ground and is taking the human error of that process out.”

3D paving will become the standard on large or high-value paving projects, according to Flores Automation and Machine Control Vice President Jason Hogue.

“We see it now on big and small projects, just depending on the application,” Hogue said. “Some airports have asphalt 6 inches deep—so in that setting, square footage may not be that great, but accuracy is everything in the world. We are also seeing 3D paving mentioned in RFIs. I have taken calls from a number of DOTs about specifications of our accuracy—some states are thinking about stating these in their state standard provisions. We have already seen this done in a couple projects in Minnesota, but they are only the first. There will be more.”

Trimble 3dTrimble Inc.

3D Paver Options

Paving contractors have a few options when it comes time to outfit their paving, compaction and milling equipment for 3D paving.

Topcon Positioning Systems offers an integrated line of 3D automation tools that can be moved from one machine to the other. Their Millimeter GPS GNSS technology, combined with a land-based laser and the PZS MC compact sensor on the paver toe arm provide vertical accuracy within a few millimeters. The Topcon 3D-MC machine control unit attaches to pavers, compactors and other equipment and the 3D-MC Milling system to millers for grinding or cold planing. Topcon’s C53 System intelligent compaction system capture stiffness, temperature and pass count. When using multiple pavers, millers and compactors on a site, the units connect to the Sitelink 3D product, which captures and cumulative pass count data on all rollers on the project to streamline the workflow and ensure multiple operators do not inadvertently over-compact.

The Trimble Roadworks 3D Paving Platform meanwhile combines automated 3D screen control accessed through the Trimble TD520 Display and PCS900 3D with the Trimble SPS930 Total Station. Trimble Roadworks allows the transfer of 3D designs from the office to the machine via the cloud so that the operator is always using the latest design. Trimble Hot Spot automatically transfers control from one Total Station to another, preventing stops as a paving line moves along the linear project. Productivity data collected from the machine is automatically synced back to the office. Paving and compaction machine performance data can be seamlessly transferred to front office applications with the SNM941 Connected Site Gateway, passing on design updates, GNSS corrections, production reporting and enabling in-field technical support.

Leica Geosystems originated 3D mobile control for paving in 1999, and goes to market in North America through Flores Automation & Machine Control, (FAMC), which maintains a sales and technician network nationwide.

The Leica MCP80 machine control panel pairs with a Leica MDS docking station which stays with the machine and retains all machine-specific performance data. So even if the MCP80 is moved from one machine to another, the data for the specific machine remains segregated for later analysis, reporting and decision support. All 3D machine control software solutions are compatible with the MCP80 panel, which serves as the universal interface across all 3D machine control applications, making it interchangeable between any heavy construction machinery. Machine-specific data such as calibration values and hydraulic parameters are stored in the docking station. In this way, the panel can be used on any other machine without the risk of losing machine data even as the MCP80 is moved from one machine to the other. This also means operators need to be trained only on one interface.

Availability of the hardware for 3D paving seems to be fairly good, despite current supply chain challenges.

“I make sure we are ordering a quarter to a quarter-and-a-half ahead to make sure we are ready to meet demand,” Hogue said. “If someone calls right now and wants 200 units, which might be a challenge but for most orders, we can fulfill them and schedule installation for one or two weeks out.”

"Prior to the problems we are seeing now, lead time to delivery was 5-10 days," Garcia said. Now it is in weeks or longer—a lot of people placing orders to get in line. Fortunately, most components are ready, so install could be 80% complete and then just wait for final hard to find components. And our biggest challenge has not been chips, radios or displays, but connector ends--the simple connector at the end of a cable."

Leica 3dLeica Geosystems

Lower Cost and Higher Quality

What 3D paving does, and why it is appealing to both contractors and project owners like federal and state governments, is enable a paving contractor to increase quality, increase margin, lower cost and shorten the timeline simultaneously.

“Most of the time, the hourly rate of an asphalt paving crew is a shockingly high number,” Garcia said. “Every little hiccup is costing you a lot of money—and it takes a lot of coordination to get the paving train moving at the right pace. That includes the plant loading out the mix at the right rate, the trucks coming at the right intervals and not having to stop and park so the mix cools off or getting segregation.”

The goal is to keep the paver moving at a consistent rate as part of a smooth and stable process. “You want to avoid stops as much as possible and changing speeds is nearly always better than stopping,” Garcia said. “The screed floats but a stop lets it sink, driving out the air voids with the weight of the screed. Every time you stop there is a discernable bump in the road. Oftentimes, you will have to come back and grind that bump—bring out the diamond grinder and grind a high spot, particularly if it is next to a low spot. These are incurred costs that you may not have budgeted for and may cause you to exceed your buffer.”

The compactor’s job would seem simpler, but also benefits from 3D technology to monitor the number of passes, degree of compaction and temperature of the asphalt. Too little compaction and the asphalt will contain air pockets, which lead to premature erosion. Too much compaction, as can happen when an operator loses track of the number of passes, they have completed and completes more than is necessary in order to be thorough, and they can crush and break down the aggregate in the asphalt. Overcompaction also, according to Garcia, can have a knock-on effect where the paver pulls further and further ahead of the compactor, which must do its job when asphalt is at the correct temperature. This causes the paver to stop, which again results in uneven spots that must be milled out.

Different 3D Paving Strokes for Different Folks

While 3D paving gives the contractor a great deal of control over quality, it also puts them in the driver’s seat when it comes to how they go about bidding and planning the job. And exactly how this control is leveraged depends on a number of things, including how a contractor is incentivized.

“It differs depending on whether a contractor is responsible for their own mix,” Hogue said. “If you are the sub purchasing the asphalt, you can use 3D paving to keep the general contractor honest. You have the capability to shoot elevations and grade before you pave—killing any argument on the volume of the job.”

“Is this a pay-by-the-ton job or is there a different incentive on this job?” Garcia said. “What sort of technologies do your crews already deploy? And what is the most important thing for your paving crew to achieve when you are on the job site? Do you need to meet the specs of the project, maximize margins on the bid—people tend to act like those things are mutually exclusive, but they don’t have to be. You can still do a really good job and put money back in your pocket if you are deploying things in the right way.”

But Garcia stresses that the contractor should consider their own needs, as well as those of the project owner.

“Is this a pay by the ton job, and if so, what is the max allowable overrun?” Garcia said. “You want to design for the exact tonnage. You want to maximize pay and not place tonnage you will not get paid for. If you produce your own asphalt, maybe want to maximize tonnage.”

Often, exceeding smoothness criteria can bring financial incentives that by themselves can make the technology attractive—over and above other incentives for maintaining the timeline.

“On the job site you have huge savings in timeline, which is important because you cannot go over without paying huge penalty,” Hogue said. The biggest no brainer is in smoothness. If you are getting your ride numbers, you are saving time and dollars for not having to grind after the fact. The second no-brainer is yield—keeping that yield below or under budget.”

Now is the Time

3D asphalt paving will become just as mainstream as 2D paving is today. And the good news is that the 2D asphalt paving systems you have already installed are a prerequisite for achieving 3D control. Automation is advancing, and doing so in a way that rewards earl adopters, extending that early investment for even greater benefit.

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