Redi-mix concrete was delivered to the corner of 52nd Street and Park Avenue by Ferrara Bros. Building Materials Corp. in 10 yard transit mixers. The concrete was then chuted below ground approximately 140 feet to the Maxon Maxcrete positioned on the subway rail siding.

At the same time the concrete was chuted into the Maxcrete, the white foaming agent supplied by Cellular Concrete LLC, was simultaneously injected. The agent increased the volume of the concrete by 30% reducing the number of transit mixers loads needed, and provided a low density concrete that after being placed could be easily broken out later on.

The electrically powered Maxcrete was supplied with an operator’s platform, to allow the operator to view the agitator of the Maxcrete while simultaneously controlling both the Maxcrete and the pump. The multi-speed, reversible agitator within the Maxcrete allowed the operator to continuously mix the foam concrete while discharging into the Putzmeister 14000 trailer pump hopper.

The foam concrete was then pumped 1,000 feet to an end section of the previously TBM bored tunnel. Two bulkheads were installed and this end section was filled with the foam concrete. Once the section was backfilled, the JV relaunched the TBM on its new heading. The cured foam concrete allowed the TBM to grip the sides of the cured foam concrete section while allowing the TBM to proceed on its new heading. Once the TBM was clear of the intersecting tunnels, the remaining low density foam concrete was easily cleaned up with a road header.

Upon completing the foam concrete production, the JV continued to utilize the versatile Maxcrete surge hopper in numerous applications including feeding shotcrete and trailer pumps (placing in situ concrete tunnel lining).