Imagine how helpful it would be to win a complex, 18,000 linear foot (5,500m) job where you expect to hand form roughly 200 feet (61m) per day, but then you find a way to slipform that job at 1,500 feet (457m) per day. Mark Bartholomew, Superintendent of A&K Slip Forming, Inc. did precisely that. Their job was on a dangerous parkway, and it included a unique design for safety. The intricate application required a highly customized mold from Power Curbers featuring two hoppers, used on their 5700-C. It took ingenuity, negotiation with the state DOT, and adjustments to the mix design to ultimately reach that peak rate. Bartholomew spoke about the job and their machine, “it put down a nice curb. I was super happy with that.”
At 104 miles (167km) long, the Taconic State Parkway is the longest in New York State. In a 2016 article, travel site Only In Your State outlined that it is also one of the most dangerous New York roads because much of the parkway is narrow, two-laned, and congested to the south with Big Apple commuters. The story also cites frequent poor weather, occasional rock slides, but primarily, reckless drivers for over 2,000 crashes between July 2011 and July 2014.
To increase safety along the route, the NYSDOT requires that all rehab or new curbing installed on the parkway have a high-visibility cap made with a unique grout that is a brilliant white. The only approved sand for the mix, a white sand out of Pennsylvania, is combined with white cement. To increase visibility further, a roller imprints grooves onto the cap like a rumble stripe. It didn’t make sense to pour the entire curb with the unique mix because the cap grout is very expensive compared to the NYSDOT Class J mix, typically used for slipforming. The specs call for most of the curb to consist of Class J while only the small cap uses the white grout. Most importantly, though, no cold joint between the two mixes was allowed.
An industry friend of Bartholomew, Pete Sommerville, had previously experimented with using a slipform technique for the same curb and together they brought it to A&K. The method involves a Power Curber mold with two hoppers. Ready-mix trucks containing Class J mix fed the first like usual. Bartholomew rented a volumetric mixer that he used to feed the second hopper. He could load the volumetric mixer with the dry ingredients for the specialized grout and mix them as needed throughout the day without it setting up. Bartholomew stressed how essential the volumetric mixer was since they went through a yard of the grout for every two trucks of Class J.
The two different mixes were setting at different times, causing problems for early pours. Distance from the batch plant meant the concrete was about 70 minutes old when it arrived. The grout was newer since it was mixed on-site, so the concrete was setting first. That caused cracking in the high-visibility cap. Bartholomew pushed the state to let him adjust the mixes by replacing 20% of the cement with slag and including 5 oz (148mL) of retarder in the Class J mix and removing the grout’s water reducer. Those changes caused the two products to set at roughly the same time eliminating cracking, and Mark expressed, “it’s going awesome now.”
Donna Bartholomew owns A&K Slipforming, where she employs sixty people. A&K has been in business for twenty-three years and complete stamped concrete, brick paver installation, and slipform work throughout New York, and into Vermont, Connecticut, and Pennsylvania. A&K runs seven crews, including the eight-man team that slipformed the Taconic Parkway job. The Power Curber 5700-C is relatively new to the slipform crew, but Mark has been running competitive machines for years. Regarding his new relationship with Power Curbers, he emphasized, “the service has been outstanding. You’ve impressed me with the quality of the mold made, the quality of the machine. I’m impressed with how well it worked.”
