How to Pave on a Moving Surface
BY John Ball
Earlier this summer, I worked with the fantastic SECON crew in Alaska to help them fine-tune existing skills and develop new skills to enhance their overall performance. The company asked me to observe and assist the crew during its execution of a paving project on a barge in Gastineau Channel, and it started with a curve ball that the crew handled with professionalism. Let’s look first at the oversized trench the crew took care of, then walk through the steps to pave on a not-so-steady surface for top quality paving. Check out the pictures on the next few pages for a deep dive into the details.
Fill the Trench
Part of a working dock system is the electronics. For this project, the owner needed an electrical trench completed. Originally, they thought it would be a little extra mix in a trough. Not so much. When the crew arrived, the owner had put a large electrical cable in deep trench and filled in 2 inches of aggregate. That left 10 inches for us to fill with hot-mix asphalt (HMA). It took about 20 tons.
- First, we hand-swept and cleaned off the dirt and dust with a leaf blower to get the sides of the trench clean.
- Next, because the distributor truck we had on the project was not equipped with a spray wand, we heated up tack in a kettle and used this to tack the sides.
- Then, we used an attachment from Road Widener on a skid steer to convey HMA into the trench. We placed it 5 inches deep and compacted that lift with a plate compactor.
- Finally, we used that same attachment to place the top 5 inches and compacted that with a tandem steel-drum roller.
- For this trench-fill, Roller Operator Vickie Brown pinched both sides of the trench, sealing the sides, before rolling down the middle for final compaction. You can read more about Brown in the October Women of Asphalt feature.
Prep the Deck
One of the first steps to any quality paving project is to clean the surface to be paved, and this was true for the barge deck in Gastineau Channel as well.
Unlike a typical paving project, we had to be extra careful with the material we swept up to ensure no dirt accidentally fell into the water. To get the deck clean in a safe way, we carefully broomed all dirt, dust, leftover aggregate, and so on into rows. Next, we brought in a skid steer to scoop up and carry away material. What material the skid steer couldn’t carry away, we captured with a vacuum sweeper.
Water was an integral part of keeping dust down, so blowing the deck dry was the final step before tacking the surface.
A surprise that made this deck different from a parking lot was the steel girder sticking up from the floor. Over the years, the concrete deck had worn and spawled to the point the steel had been exposed to the wheel loader buckets that moved material on and off the barge. Sometimes, that equipment would snag on exposed steel and cause the unsafe protrusion of girders. To keep that from causing a dangerous situation, we cut it flush with the surface with a saw.
Just as you would with a parking lot, we mapped out the best way to apply tack to avoid tracking or overcoating. We tacked the deck in long passes from the back of the barge toward the front, stopping at obstructions. We then tacked across the front from the sides toward the center to make sure all areas including the front loading area were tacked. The final pass with the tack wagon moved from the center straight off the barge.
This is the same basic layout we used to pave a leveling course and then a top lift of asphalt.
Pave it Black
The leveling course required approximately 2 inches of HMA, which we placed with a brand new 8-foot Weiler P385B tracked paver. We extended the screed to 10 feet and pulled six passes across the 60-foot deck of approximately 210 tons. I say “approximately” because this was a base course that needed to fill in some holes and crevices where the concrete had failed or where the concrete plates were not level with one another. This course lived up to its name as “leveling.”
The 2-inch surface course required 210 tons of HMA.
In almost every article I share with you, I remind you to double-check the slope and levelness of your mat with a four-foot level. When you’re on a ship docked on the water, this isn’t possible. Even with “calm seas,” there’s movement that will affect your instruments. For example, the tide rose while we were paving, lifting the barge. In this situation, you trust your equipment and your teammates to perform at their best. You can read about best practices for starting the paving day here or take a full online course for back-to-basics paving here.
Compact with Care
To achieve compaction on a concrete deck above a hollow ship’s hold, we elected to use oscillation in the breakdown rolling position and static rolling for all other compaction. The Cat CB34B that Brown used has a 51-inch drum and achieved compaction beautifully. Look at the smoothness and lack of lines this crew achieved. You can find more tips about sensitive rolling zones here.
When all was said and done, paving on a barge took attention to details like ambient temperature, extra environmental stewardship, removing broken rebar, carefully lining out the job, achieving density over a hollow ship, and so on. But the crew was up to the task and have the pictures to show how it can be done.
John Ball is the proprietor of Top Quality Paving & Training, Manchester, New Hampshire. He provides personal, on-site paving consulting services around the United States and into Canada. For more information, contact him at (603) 493-1458 or firstname.lastname@example.org.