Cargill Feed Mill July 2004, Young love Construction

A continuous concrete pour lasting almost 10 days has been one of the highlights of construction activity on a 190-foot feed mill silo being built just outside Janesville, Wis.

The rectangular silo measures 60 feet by 100 feet and extends 170 feet above ground and 20 feet below. It will house 80 separate ingredient and process slip-form bins with multiple-bottom elevations.

The feed mill is being constructed at the Cargill Animal Nutrition facility in Milton, Wis., five minutes north of Janesville. When completed, the mill will have annual output capacity of 140,000 tons of animal feed, an increase of more than 40 percent from existing area mills.

Cargill hired Younglove Construction Co., Sioux City, Iowa, as its design-build contractor based on the contractor's expertise in slip-form construction. Younglove relied on Gordy's Concrete Pumping, Sussex, Wis., for concrete pumping.

The project began with the pouring of a 600-cubic-yard mat foundation for a partial section of the silo using Gordy's 52Z-Meter Putzmeister pump. The remainder of the foundation was placed three weeks later.

The Challenge

Then the greatest challenge came, a continuous pour for 9-1/2 days beginning Sept. 11.

A slip-form process was used in conjunction with a 500-ton hydraulic jacking system.

First, concrete was pumped from ground level, upward to a special hopper.

From this hopper, buggies placed the mix into a 42-inch-high form at a thickness of 7 inches. The form was filled at a rate of 8 inches an hour. This allowed the concrete to harden at the bottom, as the form was raised and new concrete poured on the top.

"A slip form process offers a quicker and more structurally sound approach to jobs such as this one," Michael Bangert, project superintendent, said.

Such jobs typically require use of two concrete boom pumps to maintain continuous pumping. One unit usually pumps while the other is shut down for cleaning out the build-up that occurs when a pour is so slow that concrete begins to cure in the hopper and valve.

Gordy's Concrete Pumping devised an alternative system.

Its Thom-KattŽ TK 50 trailer pump and Putzmeister 52Z-Meter truck pump worked in tandem, with the trailer pump directly feeding the boom pump through the deck pipe of the 52Z.

This eliminated any need for a reduction boom pipe because the trailer pump had 5-inch pistons that connected directly to the boom's 5-inch line.

Jim Walters Jr., owner of Gordy's, said, "With the joint trailer and boom pump approach, there was no reduction and no dead spots in the hopper for build-up to occur, so we never had to stop to clean out. It avoided a lot of aggravation and hassle and it kept things moving right along. It couldn't have been more perfect."

The trailer/boom pump combination eliminated the need for having another boom pump on-site, an expense that is difficult to justify for both a budget-conscious contractor and a busy pumping company.

Pump outputs averaged only about 12 yards an hour on the pour. Although this was not a high-volume job (the best application for a larger boom pump) the Putzmeister 52Z-Meter was needed for its 180-foot reach and flexibility to maneuver five uniquely designed boom sections.

In confined areas, the first three sections could be extended vertically, the next section positioned horizontally and the remaining section placed vertically, again for maximum reach.

"You can't get that kind of reach with only a four-section, 52-meter boom," Walters said.

If needed, the 52Z pump, or a crane and bucket on-site, could have been used for backup. But because of the reliability of the pumping equipment, no problems were experienced in the 270 hours of concrete placement.