Subgrade Void Stabilization and Geopolymer Concrete Lifting in Cedar Rapids, IA
Challenge
In Cedar Rapids, IA, a residential property exhibited advanced structural distress across its exterior flatwork, characterized by severe slab settlement, differential offset elevation, and localized stress fractures. The homeowner, concerned about physical safety hazards and negative real estate inspection disclosures, requested a structural diagnostic from MidAmerica Basement Systems. Upon site evaluation, System Design Specialist Daniel Kelchen performed a complete subgrade inspection. His diagnosis revealed that sub-slab soil erosion, triggered by poor water runoff management and seasonal freeze-thaw cycles, had created large void networks beneath the concrete. Lacking adequate subgrade support, the heavy concrete slabs settled unevenly under their own weight, creating offset heights of up to two inches, which formed significant tripping hazards and allowed further water infiltration.
To stabilize the flatwork without the high cost, long curing times, and heavy equipment required for a full concrete tear-out and replacement, Daniel Kelchen specified a two-part geopolymer and sealant system. The PolyLevel® geopolymer system was chosen for its fast-curing, high-density properties, allowing it to expand, fill hidden voids, consolidate the loose subgrade, and lift the heavy slabs. To prevent future water from seeping back under the slab, all joint lines and open cracks were specified to be sealed with NexusPro® Joint Sealant, a highly flexible, UV-resistant compound that accommodates natural slab movement and keeps water out.
Solution
Foreman Justin Maddox and technician Devin S. executed the physical leveling process using a precise, non-destructive installation sequence. First, the team drilled a series of small, five-eighths-inch injection ports at strategic intervals across the settled concrete plates. Next, they secured high-pressure injection nozzles into the ports and pumped the two-part liquid polyurethane formulation beneath the concrete. Upon contact with the subgrade, the liquid chemical reaction caused rapid, controlled expansion. The foam quickly filled the void space and compacted the weak soil below, exerting upward force to lift the concrete plates back to a level, flush position..
Once the lifting was complete, the team cleared out all loose debris from the open joints and cracks and applied NexusPro Joint Sealant, tooling it smooth to create a durable, waterproof barrier. They then removed the injection nozzles, filled the small ports with matching concrete patch material, and cleaned the entire workspace. Unlike traditional mudjacking, which uses a heavy slurry of sand and cement weighing over one hundred pounds per cubic foot and taking up to seventy-two hours to cure, the PolyLevel geopolymer weighs only about four pounds per cubic foot, resists water washout, and cures within fifteen to thirty minutes. The completed project successfully resolved the home's safety and financial risks, leaving the homeowner with beautifully level, stable concrete that protects their home's equity.