Once the pavement was cleaned, the Brooks crews worked four days installing 1400 tons of either full-depth or partial-depth patching, primarily to repair the ruts. He says 100 tons of full-depth patching was done on the road, 200 tons of full-depth patching was done on the shoulder, and the remaining 1100 tons was partial-depth patching (4 inches).
“In Indiana we do the patching before the milling because you get a better overall job,” Koble says. “Once the patches are milled, any deviation or undulations in the patches get smoothed out and the finished paving job is that much better and much smoother.”
Once the pavement was patched, a subcontractor using a Wirtgen machine milled 1 ½ inches off both the main road and the shoulder, and Koble says the work day restrictions were felt most at this stage of the job. He says Indiana requires milled pavement to be overlaid within five days so the contractor couldn’t allow the milling to get too far ahead of the paving.
“This is where the nearby job really came in handy because we were able to work both jobs back and forth.”
Paving with Steel Slag
Once the crew was able to start paving, they used what Koble says is the contractor’s typical paving approach: A Roadtec 2500 shuttle buggy transferred the mix to a CAT 1055-D paver. That was followed by a three-roller train with a Dynapac CC722 vibratory roller in the breakdown phase, an Ingersoll-Rand DD130 in the intermediate phase, and a Hamm HD120 DO as the finish roller.
All work was done amidst live traffic – buggy and otherwise – with flaggers regulating flow. Koble says that only one problem occurred when a horse, spooked possibly by a truck when halted by a flagger, took off and had to be reigned in by a Brooks worker.
Koble says the bid for the job specified use of steel slag in the hot mix, particularly on the shoulders, to help the pavement last longer and delay rutting caused by horse and buggies. This job called for CAPP (Certified Aggregate Producer Provided) steel slag #11 coarse aggregate and #24 CAPP steel slag sand.
“Normally you use the lower grade mix on the shoulders and the higher grade mix on the road because you don’t expect the shoulders to get that much traffic. But in this case it was flip-flopped,” Koble says. “The slag creates an abrasive mix so they are probably going through more horseshoes than they did before.”
He says that mix with steel slag had been a premium product, partly because it had to be hauled in from steel mills in the Chicago area. But because new smaller local steel mills have contracted with Brooks to provide steel slag and steel slag sand, the product can be supplied locally so it is more cost-effective and is no longer considered a premium-priced product in the northeastern Indiana market.
Koble says the mix featuring steel slag is a denser mix that weights more per square yard than a conventional mix. He says that because the slag doesn’t absorb the asphalt cement as readily as other aggregate, the percentage of asphalt cement in the mix is less than a conventional mix, making the mix slightly less costly.
“Because it’s heavier than a conventional mix, you are actually placing more tonnage than the bid calls for, so you have to adjust the bid accordingly,” he says.
He says the state of Indiana allows a mix adjustment factor of +/- 2% of what’s called for in the bid, which Brooks accounted for in the bidding to make sure the job would be profitable. “If the job calls for 165 lbs. per square yard, and because the mix is more dense, you are actually placing 175 lbs. per square yard, you need to account for that in the bid. And not just in material cost but in the hauling, placement and compaction too.”
But he says the difference in mixes has little to no impact in the field. In fact, he says the only change in the field is in the tender zone of compaction, but Brooks always places a 300-ton test strip at the job location in advance of the work to make sure to get compaction right.
“We do it on every road job and on every commercial job where density is specified,” Koble says. “We take a day, lay 300 tons and leave and wait for the test results. That way we know the passing results before we start full production.”