Sparrows Point, in Baltimore, Maryland is a brownfield site being redeveloped from steel manufacturing to industrial and logistics use. From it says as a heavy manufacturing facility, there is an extensive freight rail network throughout the site, with many grade crossings subject to significant heavy truck traffic & heavy haul rail traffic.
A precast tub-style grade crossing on a road feeding a metals recycling plant developed a 2.5″ belly. The local FRA inspector instructed the railroad to correct the settlement.
CJGeo performed structural polyurethane grout injection to fill voids below the panels, and then lift them back into their correct alignment. The work was completed in a few hours, without disruption to the rail or auto traffic.
The 11″ thick slab floor of a storage shed at a port facility settled up to 6 inches. Exploratory coring & non-destructive imaging (GPR & microgravity) indicated there were extensive voids below the floor.
Previous work on the adjacent bulkhead uncovered extensive voids below the exterior footings (pile-supported) and multiple abandoned, but unfilled, pipes under the floor.
Due to relatively thin voids, which were all less than 6 inches, and void filling grout had to be highly mobile. However, this posed environmental challenges due should the grout make its way into an unfilled abandoned pipe and into the adjacent waterway. The owner did not want to lift the floor, so grouting had to be sufficiently low mobility to prevent runaways, but also fill all voids at an economical hole spacing.
CJGeo proposed polyurethane grouting for this slab foundation repair project. The original design was for a 50/50 mix of polyurethane and cement grouting, CJGeo proposed a valued engineering proposal to perform all grouting with polyurethane. A high density (3.3PCF free rise, 4PCF in place) TerraThane grout was proposed to balance mobility for completeness of fill and reaction time to avoid any runaway loss into the adjacent waterway.
CJGeo mobilized a two-reactor polyurethane grouting rig and installed approximately 6300lbs of polyurethane grout over a three-day period. Pneumatic rock drills were used to speed drilling.
An area of the floor inside of a produce processing facility experienced water intrusion through joints in the floor. Considerable amounts of process water were dumped on the floor each day, and unsealed joints in the floor allowed water to collect under the floor slab. With dynamic loading from material handling equipment, water was displaced through the joint onto the floor. The facility’s health & safety staff was concerned that the water could introduce contaminants to the food processing area.
The proposed repair had to perform well in saturated conditions, allow for near immediate resumption of material handler equipment, and ensure a long-term fix. Since no settlement had occurred, the grout material had to be able to seal the very small voids, displace water, and not exert any lifting forces on the floor.
The material & process also had to be performed at cold temperatures–the facility is maintained at 34 degrees year-round.
CJGeo proposed chemical grouting using a hydrophilic prepolymer grout. Chemical grouting is ideal for saturated environments and helps to ensure complete stabilization and sealing of floors.
A single CJGeo chemical grouting crew mobilized to the site and performed the work in a few hours. The work started after the second shift and was completed in time for the grout to set and tolerate material handling equipment at the start of the first shift.
The following day, the facility reported no water extrusion under material handler traffic.
The floor of a 105′ diameter grain bin settled. The floor had a bin sweep installed, that was mounted on the top of the unloading tunnel, which ran down the center of the structure. Where the slab floor butted up to the tunnel walls, the floor had settled 2″ on one half, and 3.5″ on the other half. This caused issues with operating the bin sweep because it was designed for a smooth, level floor.
The owner’s alternative was to remove the entire floor and pour a new floor. This would have been incredibly expensive and taken a very long time. The only access into the bin was two 2′ wide by 4′ tall doors, located 5′ above exterior finish grade, and 2′ above the bin floor elevation.
Due to the nature of the commodity business, mobilization and completion of the grain bin floor repair had to be fast. Additionally, the repair had to return the floor to its original profile, along with the turned-down ventilation trenches in the floor. The extensive turned-down ventilation troughs made this floor very susceptible to cracking. The floor was 6″ thick but then went to 24″ thick at the ventilation troughs. Slabs with non-uniform thickness require extreme care and attention to avoid differential lifting.
The design loads for the floor are approximately 3500psf, so the material used for lifting the floor had to be relatively high strength.
CJGeo proposed polyurethane grouting for filling the voids below the floor and lifting them back into place. The minimum bearing capacity of the proposed materials was 5500PSF, ensuring adequate bearing capacity even under full load.
CJGeo mobilized two polyurethane grouting crews to the site. The work was completed over a period of two days, during which more than 7,000 pounds of polyurethane grout were installed using three reactors running simultaneously. Multiple reactors (pumps) helped to ensure thorough lifting of the slab and the ventilation troughs. The crews that completed this job have collectively performed millions of pounds of polyurethane grouting, ensuring the successful completion of this grain bin floor repair job.
25,000 square feet of the industrial floor at a military facility settled up to 4 inches and was affected by sub-slab voids. The affected area also included 250 track feet of embedded rail, which was set in an independent, thickened slab section. The building had been used for warehousing but was being transitioned to light manufacturing/maintenance.
Plans called for a 4” thick overlay slab to be installed, with a vapor barrier, over the existing floor. Geotechnical investigation work determined there were extensive voids below the floor throughout the area affected by settlement.
The proposed repair method had to provide adequate bearing capacity for manufacturing and ensure complete void filling and stabilization.
Polyurethane grouting fills voids under the floor to stabilize against future settlement. Additionally, in areas that had settled, polyurethane grouting was proposed for correcting settlement.
Due to extensive compressive soil layers below the floor, polyurethane grouting was proposed as an alternative to the specified cementitious grout. The specified grout had an in-place density exceeding 115 pounds per cubic foot. The proposed polyurethane grout had a constrained density of 5.5PCF, yet a bearing capacity exceeding 12KSF.
CJGeo mobilized three polyurethane grouting crews to the facility, with a combined pumping capacity exceeding 5,000 pounds per hour. Nearly 2,000 dime-size injection holes were drilled through the slab, and 5,000 cubic feet of polyurethane grout was installed under the floor & section of embedded rail. The void filling was confirmed by visual inspection (material showing at adjacent drilled holes to injection locations), and slab lifting.
In areas that had not settled, 1/8 inches of the lift was used as the benchmark change in elevation to confirm complete void filling. Areas that had settled, including the embedded rail sections, were lifted up to 3 inches above the original elevations.