Protecting concrete usually means shielding it from the elements of nature or from harsh manmade chemicals. But it’s not just concrete that needs such protection. Corrugated metal pipe, steel surfaces, material hoppers, rail cars and masonry all can come in contact with corrosive or abrasive materials or harsh conditions.
The geotechnical needs of DOTs and other agencies responsible for roads and bridges are vast. Issues include: Culvert repair Soil stabilization Void filling Concrete slab lifting Sinkhole remediation Slope control Slough control in tunneling
Contractor: Merco Geopolímeros
Client: Major beverage manufacturing and bottling facility, Porto Alegre, Brazil
PROBLEM: Merco Geopolímeros of Brazil was hired by a major beverage manufacturer to fix a situation in one of its facilities: a section of the concrete floor was sinking, causing huge tanks to tilt. A drainage trough runs between rows of tanks used to make beverages. Caustic soda is used to clean the tanks, so the water flowing through the trough contains some of this substance. The drainage trough had been overflowing, sending fluid up underneath damaged concrete abutting the trough into the subgrade. This caused the floor of the facility to settle 8-10 inches, resulting in two of the 3300-gallon tanks tilting dangerously close together. In fact, the transport tabs near the top of the tanks were actually touching.
A penetrometer reading was done in advance, which indicated there were no voids. Upon arrival at the site, however, an overview survey showed there were 24- to 30-inch voids in the area near the tank settlement. Why the discrepancy? The penetrometer test done by an independent engineering firm was done 20-30 feet from the settled area, resulting in an incorrect reading. Further, a Prime Resins technical consultant on site was able to push a 10-millimeter rod by hand 16 feet into the ground. This indicated that the subgrade had turned to mush after years of soaking with water containing some caustic soda.
SOLUTION: Replacing the floor was not an option the client could consider. The downtime needed to move the tanks, demolish the floor, replace the subgrade, replace the concrete floor and return the tanks would have been weeks, a prospect they simply couldn’t afford. According to the approved plan to use polyurethane grouts to solve the problem, 130 gallons of Prime Flex 920 were pumped 3 feet into the subgrade to stabilize the base for the lifting operation. Prime Flex 920 is a hydrophobic, single-component polyurethane structural foam used for soil stabilization, leak sealing and void filling. Another contractor was called in to fill the void with a flowable fill concrete, which was unsuccessful at filling the entire void because it did not flow properly. The next step was to inject Precision Lift 4.0#, a two-component structural polyurethane foam that generates hydraulic lift. Because the cementitious material did not completely fill the void, the Precision Lift served as soil stabilizer—compacting the mushy subgrade enough to provide a solid base—a void filler and a lifting agent to lift the concrete floor.
Approximately 400 gallons of Precision Lift were injected over two days using a low volume pump. The concern was that injecting such a large volume of expansive foam could break the concrete slabs, hence the cautious approach. The void filling was done the first day with a bit of lift happening as well. The second day’s injection resulted in returning the floor to its original position, resulting in tanks that were properly vertical and parallel. An added benefit was that the Precision Lift foam encased the trough system, sealing the leakage points, reducing further degradation of the subgrade.
All the work was performed under the strict supervision of safety and engineering officials. Plant production was shut down for two days.
Photos are copyright of Prime Resins and are not for re-use.
Why did Merco Geopolímeros choose Prime Resins?
“We did more than a year of research across Europe and the United States before choosing Prime Resins. We are now business partners and official distributors of Prime Resins products and solutions for Brazil since January 2015,” said Paulo Fernando Romeiro Santiago, director of commercial operations. “We have confidence in the company and its good and experienced technicians.”
OUTCOME: Despite the unexpected void, Merco was able to solve both the settling problem and lift the concrete floor slabs back to their proper position with minimum disruption to plant operations.
“The results were much better than expected,” said Santiago. “This client has already invited us to perform more work immediately in some of the 49 other facilities they have in Brazil. This method was a success and broke paradigms in Brazilian engineering.”