Alchatek Blog

AT&T Plaza in downtown Dallas had persistent water infiltration issues in its basement and sub-basement levels, resulting in structural concerns and operational disruptions. The building's below-grade concrete walls developed multiple active leaks, allowing groundwater to penetrate the structure and causing dampness at wall-floor transitions, which raised concerns about potential corrosion of the reinforcing steel. Building management required an immediate solution that would effectively seal the leaks while minimizing disruption to commercial operations.

Initial Assessment

Engineering inspections by B|S|A Design Group revealed multiple active leak points throughout the basement and sub-basement concrete walls, with water infiltration occurring through cracks, joints, and penetration points. The moisture intrusion patterns indicated that several leak locations had been active for an extended period. Traditional waterproofing methods would require extensive excavation and reconstruction, making them impractical for a busy downtown commercial building. The assessment concluded that targeted injection would be most effective while allowing the building to remain operational.

Proposed Solution

The engineering team specified Spetec PUR F400, a hydrophobic polyurethane grout designed for water cut-off applications in concrete structures. This single-component material was selected for its ability to react with water to form a flexible, closed-cell polyurethane seal that permanently stops water infiltration. The material's low viscosity allows deep penetration into crack networks while its hydrophobic nature ensures effective sealing in wet conditions. This approach would eliminate disruptive excavation while providing a permanent solution.

Procedures

1. Engineers identified and mapped all visible leak points, prioritizing the most severe infiltration locations.
2. Injection ports were drilled at strategic locations to intersect water migration pathways through the concrete structure.
3. Spetec PUR F400 was mixed with appropriate catalyst ratios and injected using controlled pressure techniques.
4. Technicians monitored for complete crack filling and leak cessation, with post-injection inspections confirming successful sealing.
5. Work was coordinated to minimize disruption to building tenants throughout the process.

Results

The injection process successfully eliminated all water infiltration throughout the treated areas. Post-repair monitoring following significant rainfall events confirmed the complete cessation of leaks, with previously wet areas remaining dry. The project was completed with minimal disruption to building operations. The injection approach achieved 98%+ cost savings compared to traditional excavation and membrane installation methods. Additionally, avoiding a building evacuation prevented an estimated $25,000-$ 50,000 in lost rental income and tenant relocation costs.

Want more information on polyurethane leak seal products?

A persistent water infiltration was observed in a below-grade tunnel in Houston, TX. Staining on the sheetrock ceiling indicated the leak originated at the joint between the tunnel shell and the building wall, specifically at the interface with the flashing. The tunnel was situated on the negative pressure side of the structure, resulting in recurring water intrusion issues. The property management team sought technical advice to resolve the leak without extensive demolition or disruption to the building’s operations.

Initial Assessment

Visual inspection confirmed that water was entering through the wall/flashing joint and migrating into the tunnel ceiling. The stains and moisture patterns suggested a continuous leak path exacerbated by negative hydrostatic pressure. The location and nature of the leak made traditional surface repairs ineffective, as water was entering from behind the structure and not from an exposed face.

Proposed Solution

Alchatek recommended injecting the joint between the tunnel shell and the building wall with Spetec PUR F400, a hydrophobic polyurethane grout. This product was chosen for its ability to react with water and expand, effectively sealing active leaks even under negative pressure. The material’s low viscosity allows it to penetrate tight joints and bond with both concrete and steel, creating a durable, watertight seal. The recommended installation method involved using a Titan 440 electric injection pump, ensuring the grout was injected until the joint could no longer accept any more material.

Procedures

1. The team identified the leaking joint at the wall/flashing interface as the primary injection target.
2. Injection ports were installed along the joint to provide access for the polyurethane grout.
3. Spetec PUR F400 was injected using an electric injection pump, with technicians monitoring for material refusal and observing for any signs of milky fluid or foam, which indicated grout migration.
4. Injection continued until the joint was fully saturated and would not accept additional material, ensuring complete sealing of the leak path.
5. The process required no pre-pumping or removal of water from the joint, as the hydrophobic grout was designed to react in wet conditions.

Results

The polyurethane injection successfully sealed the leak at the tunnel shell/building wall joint. Post-repair observations showed no further water staining or active intrusion in the tunnel ceiling, and the tunnel remained dry even during subsequent rain events. The method enabled targeted remediation with minimal disruption to building occupants and eliminated the need for costly demolition or exterior excavation. The use of Spetec PUR F400 provided a cost benefit of 96% compared to traditional invasive repair methods. The property management team was satisfied with the outcome and the efficiency of the repair process.

Want more information on crack injection?

At Antwerp Airport, a section of the runway slab had settled by 1–2 inches, creating a hazardous rocking effect that endangered aircraft landing gear and led to grounded flights. Aircraft wheels hitting the depressed area like a pothole generated dangerous jolts. Although the settlement had persisted for years, mounting operational demands finally compelled immediate action.

Initial Assessment

Initial investigations revealed voids beneath the 8-inch-thick concrete slab. Replacing the entire slab proved impractical because it would require a multi-day runway shutdown, extended project timelines, and substantially higher costs.

Proposed Solution

The contractor selected Alchatek’s AP Lift 430 polyurethane foam for its hydro-insensitivity, rapid strength development, 22x expansion ratio, and compressive strength of 7,200 psf. These properties enabled efficient lifting and stabilization with minimal downtime.

Procedures

1. Marked the slab and established 8 injection points in a grid pattern.
2. Drilled through the 8-inch slab and installed injection ports.
3. Injected 16 gallons of AP Lift 430 in staged passes.
4. Monitored elevations with dial indicators.
5. Sealed the drill holes and restored the surface.

Results

• The slab was lifted to specifications, resulting in zero differential settlement with adjacent panels.
• The project was completed in just 4 hours—over 90% faster than a full slab replacement.
• The international airport resumed its full flight schedule the same day, avoiding over $100,000 in losses from runway closures.

Want more information on lifting slabs with polyurethane?

A single-story office building settled over organic soils beneath its post-tensioned slab. With access restricted to the interior, a fast and clean repair was essential. Geotech experts from Helicon were called in to assess the situation.

Initial Assessment

Borings showed dense to very loose strata and differential movement under interior columns and slab zones; uniform densification and code‑level lift tolerance were required. Traditional underpinning inside an occupied shell would extend schedules and raise costs versus targeted polyurethane injection.

Proposed Solution

The contractor selected AP Lift 440 for hydro‑insensitivity, rapid reaction, and ~80 psi compressive strength. This material was ideal to permeate, densify, and lift with minimal downtime.

Procedures

1. Inject 30,000 lbs over 635 interior points per geotech layout.
2. Apply tight grid spacing, pressure/volume control, and real‑time elevation checks.
3. Coordinate QA/QC with the Engineer of Record for sign‑offs.

Results

• Restored slab support and column bearing
• Zero exterior disruption; interior‑only access.
• Approximately 97% cost savings vs interior underpinning/piering, with faster completion.

Want more information on polyurethane concrete leveling?

A critical downtown Houston pedestrian tunnel had persistent water infiltration affecting the ceiling, walls, and floor throughout the structure. The tunnel serves as vital underground infrastructure in Houston's urban core, where any significant disruption would impact pedestrian traffic and building access. Initial observations revealed widespread moisture intrusion, but the full extent of the problem remained unclear until interior finishes could be removed for proper assessment. The facility required a rapid, effective solution that would minimize downtime and restore the tunnel's watertight integrity.

Initial Assessment

Once sheetrock was removed from affected areas, engineers discovered extensive water infiltration through multiple pathways in the concrete structure. Moisture intrusion was occurring through joints, cracks, and penetrations, creating a complex leak pattern that compromised the tunnel's structural integrity and usability. Traditional repair methods would have required extensive excavation from above or complete tunnel closure for membrane installation - both prohibitively disruptive options in Houston's dense downtown corridor. The assessment revealed that targeted injection could address the root cause of infiltration without major structural modifications.

Proposed Solution

Alchatek recommended using Spetec PUR GT350, a hydrophilic polyurethane grout specifically designed for active leak sealing in underground structures. This single-component material was selected for its ability to react with water to form an expanding, flexible foam that creates a permanent, waterproof barrier. The injection approach would allow precise targeting of leak sources while maintaining tunnel accessibility throughout the repair process. The polyurethane's expansion properties would ensure complete void filling and crack sealing, even in areas with irregular geometries or active water flow.

Procedures

1. Mapped all visible leak points and moisture intrusion areas throughout the tunnel structure.
2. Drilled strategic injection ports at locations determined to intercept water infiltration pathways.
3. Injected polyurethane grout through ports using positive displacement pumps, monitoring for material refusal and leak cessation.
4. Conducted systematic injections across all identified problem areas, adjusting techniques based on local conditions.
5. Verified complete sealing through visual inspection and moisture monitoring following cure completion.

Results

The polyurethane injection process successfully eliminated water infiltration throughout the tunnel structure, restoring its watertight integrity without requiring facility closure or major structural modifications. Post-treatment inspections confirmed the complete cessation of leaks, with the tunnel remaining dry even during subsequent heavy rain events. The minimally invasive approach allowed the tunnel to remain operational throughout the repair process, avoiding costly service interruptions. For a typical tunnel section, this represents over 95% cost savings compared to traditional methods. Additionally, avoiding tunnel closure prevented an estimated $10,000 to $ 25,000 in daily economic losses due to disrupted pedestrian traffic and building access, further amplifying the financial benefits of this innovative approach.

Want more information about polyurethane crack injection?

A tunnel structure in the Mobile, Alabama area had persistent water infiltration at the interface between concrete and metal components. The leak was traced to a tight crack at the joint, allowing water to migrate into the tunnel and cause visible staining, as well as potential long-term deterioration. The client sought a solution that would seal the leak without requiring major demolition or extended tunnel closure.

Initial Assessment

Visual inspection and on-site review identified the leak path at the interface between the concrete and metal. The crack width was measured between 0.2 and 0.3 mm, indicating that traditional cementitious grouts or surface sealants would not be effective. The challenge was to deliver a material that could penetrate deep into the joint and expand to form a watertight seal, even in confined spaces and around embedded metal.

Proposed Solution

Alchatek recommended Spetec PUR F400, a low-viscosity, hydrophobic polyurethane grout. Its ability to penetrate narrow cracks and react with water creates a durable, flexible seal. The product’s flow characteristics made it ideal for tight joints, and its expansive properties ensured comprehensive coverage within the voids and cracks. The injection plan called for drilling at the locations marked on the provided site photos, angling back toward the metal at approximately 18 inches deep to intersect the leak path.

Procedures

1. Identified injection points along the crack, using red-dot markings on the structure as a guide.
2. Drilled holes at 45° angle 12-inches apart, reaching approximately 18 inches deep to intersect the metal interface.
3. Injected Spetec PUR F400 polyurethane grout through the drilled ports, using a pump setup suitable for low-viscosity materials.
4. Monitored for material refusal and evidence of grout migration to ensure the joint was fully saturated and sealed.
5. Continued injection until the crack would not accept additional material, confirming a complete watertight barrier.

Results

The injection process successfully sealed the tunnel leak at the concrete-to-metal interface. The approach allowed for precise targeting of the leak path, with minimal disturbance to the tunnel structure and no need for extended closure or demolition. The client was able to resolve the water infiltration efficiently, reducing the risk of future deterioration and avoiding the significantly higher costs and downtime associated with traditional excavation or membrane replacement. This project demonstrates the effectiveness of modern polyurethane injection in addressing challenging below-grade leak scenarios, particularly where access is limited and the leak path is confined.

Want more information about sealing cracks with polyurethane?

After the removal of a wooden deck, dangerous voids under the brick pavers were revealed in a luxury apartment pool deck, threatening its integrity and safety. The property owner contacted Helicon, a trusted foundation repair company.

Initial Assessment

Subsurface investigation confirmed extensive voiding with no practical access for excavation during occupancy. Demolition/replacement would take weeks, cost tens of thousands, and the pool would need to be closed during peak season.

Proposed Solution

The contractor selected AP Lift 440 for its hydro‑insensitivity, ~15‑minute cure, and ~80 psi compressive strength. This material was ideal for increasing the soil's bearing capacity and restoring the pool to its correct state.

Procedures

1. Map the void locations using ground-penetrating radar and probing.
2. Establish an injection grid targeting the largest voids first.
3. Drill strategic injection ports through pavers to void spaces.
4. Inject AP Lift 440 to refusal using calibrated pressure monitoring.
5. Allow 15-minute cure
6. Seal injection ports and restore surface aesthetics.

Results

• Structural integrity fully restored with 1,200 lbs of AP Lift 440, filling all voids.
• Zero operational downtime; pool deck remained accessible throughout repair.
• Approximately 70-90% cost savings compared to demolition/replacement alternatives.

Want more information on Alchatek geotechnical products?

A Tennessee state correctional facility had a significant infrastructure failure when newly installed plumbing beneath a concrete slab malfunctioned. In an attempt to address the issue, the original contractor backfilled the entire plumbing system with concrete. When this approach proved unsuccessful, a second contractor was brought in to demolish the concrete and properly repair the plumbing systems. This process left a substantial void beneath the slab that required immediate filling to restore structural integrity and minimize facility downtime.

Initial Assessment

Following the plumbing repairs, engineers assessed a void measuring approximately 200 square feet in area and 4-5 feet in depth, totaling roughly 800-1,000 cubic feet of empty space beneath the concrete slab. The prison's security restrictions severely limited access to equipment, making traditional concrete replacement a challenging and time-consuming process. The facility required a solution that would minimize disruption to operations while providing structural support equivalent to the original concrete base.

Proposed Solution

Working with Alchatek, Mid-South Concrete Lifting recommended using  AP Fill 420, a two-component structural polyurethane foam, to fill the substantial void. This approach offered several critical advantages for the correctional facility environment. The material could be applied through a simple hose system, eliminating the need for heavy concrete trucks and mixing equipment that would be difficult to maneuver through security checkpoints. The foam's rapid curing time would significantly reduce the project timeline, and its structural properties would provide adequate load-bearing capacity for the slab above.

Procedures

1. Security clearance and equipment inspection were completed to bring polyurethane application equipment into the facility.
2. The void was accessed through existing openings created during the concrete removal process.
3. AP Fill 420 was applied using a free-shooting technique.
4. Material application was monitored to ensure complete filling and proper expansion throughout the space.

Results

The void filling was completed in 3 hours versus an estimated week for concrete replacement. AP Fill 420 polyurethane foam successfully filled the entire void space and provided adequate structural support. Prison officials expressed satisfaction with the efficiency and minimal operational disruption, leading the contractor to look at another similar project at a different state facility.

The polyurethane approach delivered 65-75% cost savings compared to traditional concrete replacement when accounting for materials, equipment, labor, and reduced facility disruption. The accelerated timeline also eliminated the extended security coordination costs typically associated with longer construction projects.

Want more information on geotech products and equipment?

Fifteen, two‑unit condominium buildings exhibited differential settlement and interior slab movement from loose organics and voiding, risking structural performance and livability. Continuous occupancy required a rapid, low‑disruption remediation strategy that delivered durable lift and stabilization. The job was completed by foundation repair specialists at Helicon.

Investigations confirmed loose to very loose near‑surface soils, voids at 3–8 ft below the surface, and active settlement beneath slabs and footings under service loads; full replacement was not viable due to resident displacement, extended schedules, and higher cost risk.

Proposed Solution

The experts at Helicon selected AP Lift 440 for its hydro‑insensitivity, rapid reaction, and ~80 psi compressive strength to permeate, densify, and lift with minimal downtime.

Procedures

1. Grid the interiors; mark piles, grout points, and quality control benchmarks.
2. Inject low‑mobility compaction grout to seal limestone and pre‑densify.
3. Install underpinning to ~36 ft, using predrill/sleeves to bypass clays.
4. Inject AP Lift 440 at 8/5/3 ft below land surface to lift slabs and encapsulate organics.
5. Monitor elevations/pressures; proof‑load and video‑verify.

Results

• Restored slab elevations and footing support with no resident displacement.
• Completion in days to weeks vs months for replacement.
• Approximately 80-90% cost savings versus full demolition/rebuild approaches.
• Durable, closed‑cell, water‑resistant stabilization for long‑term performance.

Want more information on polyurethane slab lifting?

A south Georgia roadway developed a sinkhole over a double 48-inch RCP storm line about 10 feet deep, threatening lane safety and mobility. Replacement costs were prohibitive and would require extended closure and excavation.

Initial Assessment

The pipe exhibited joint leakage and surrounding soil loss, creating voids under pavement and shoulder with settlement risk across the travel path. Traditional open-cut replacement would demand deep shoring, traffic detours, and high restoration costs, making trenchless stabilization preferable. SiteMix Pressure Grouting LLC was called in to do the work.

Proposed Solution

The contractor selected AP Lift 475 for hydrophobic chemistry, industrial strength, and rapid set to encapsulate pipe exteriors, seal soil paths, and rebuild bearing capacity with minimal downtime.

Procedures

1. Lay out three rows on 3-foot centers around both barrels.
2. Inject at 6 lb per vertical foot to refusal for soil reconsolidation.
3. Pull the injection tubing vertically while injecting to form grout columns.
4. Encapsulate/seal pipe perimeter and monitor lift response.
5. Verify surface support and closure readiness.

Results

• Completed in one day with 1,400 lbs placed; roadway lifted and voids eliminated.
• Zero excavation and minimal traffic disruption during work.
• Approximately 95% cost savings compared to pipe replacement.

Want more information on lifting slabs with polyurethane?