Redi-Fill

The City of Chicago Bureau of Streets turned to Prairie last fall for help in its vaulted sidewalks rehabilitation program. The vaulted sidewalks are a remnant of Chicago's past when the streets and sidewalks throughout the city were raised to be at the same elevation above sea level and to accommodate modern utilities. In some neighborhoods that meant raising the street more than six feet, creating a void under the sidewalks. The city is slowly filling in the voids, while raising the sewer lines and gas lines closer to the street surface. With more than 1,000 miles of streets affected, the project will take decades to complete.

The standard backfill procedure has been to place truckloads of granular fill and in 18" lifts, compacting and testing between each lift. In the past, the entire process took two or three days per vault, a crew of three or more workers and required the use of expensive compacting equipment.

Initial testing proved to the Bureau of Streets that Prairie's proprietary, self-leveling Redi-Fill™ mix met design expectations, increased crew efficiency, and eliminated the need for granular fill and compacting equipment. A typical void could be filled in three hours rather than three days.

The city has opted for a hybrid approach that uses granular fill for two-thirds of the void and tops off the final third with Redi-Fill. “We love the stuff,” says the Bureau of Streets’ Dale Ansel. “But with budget cuts and the long term nature of the project, we found it can still save us time and resources to use less of it. We save at least one day per vault now.” An added bonus is that Redi-Fill stabilizes and reinforces the existing sidewalk, eliminating one of the key problems of just patching up the infrastructure.

Prairie Material has used a different form of Redi-Fill for more than 7 years in the Indianapolis area to backfill street cuts, pipe trenches, underground tanks and foundation walls. During that time, there have been no reported failures and the savings in manpower, repair time and public annoyance have been outstanding.