How to Seal Leaks | Repair Cracks in Shotcrete
How to Seal Leaks and Repair Cracks in Shotcrete
Shotcrete is a versatile and durable material widely used in construction for creating complex structures, including decorative elements in zoos and theme parks.
However, like any other material, it is prone to developing cracks and leaks over time. Addressing these issues promptly is crucial to maintain the integrity and appearance of the structures. This article outlines a practical example of how the SealBoss Water Stop System was effectively used to repair a decorative shotcrete structure at the Omaha Zoo.
Shotcrete Water Intrusion: Why Risk Is Higher than CIP and How Injection Mitigates It
Shotcrete is a workhorse for tunnels, basements, shafts, tanks, and slope stabilization. But compared with well‑vibrated cast‑in‑place (CIP) concrete, shotcrete has a higher risk of water intrusion—not because the material itself is inferior, but because placement variables (nozzle technique, rebound, and bonding) can create porous zones, laminations, and honeycomb voids.
The good news: injection grouting precisely targets those leak paths without demolition.
Common Leak Sources in Shotcrete
- Rebound pockets & laminations behind the finished face or around congested steel
- Honeycombs/voids near corners, embeds, and penetrations
- Cold/day joints with incomplete bonding between lifts
- Interfaces at shotcrete‑to‑rock or shotcrete‑to‑existing concrete
- Cracks (shrinkage, thermal, or flexural) that become water carriers
Summary – TL;DR
- Shotcrete is more sensitive to workmanship than CIP. That sensitivity increases the odds of rebound pockets, laminations, and honeycombs that become water pathways.
- The fastest, least disruptive fix: chemical injection—spot seal and stop active water with hydrophobic/hydrophilic polyurethane (PU) foam injection, or for large scale porosity in below grade structures seal with low viscosity PU foam or ultra‑low‑viscosity acrylate gel (curtain injection) as needed.
- Use epoxy only if structural crack repairs are specified and after water control.
- Use lowest possible, controlled injection pressure, tight port patterns, and clear pass/fail criteria.
How to Seal Leaks and Repair Cracks in Shotcrete – The Challenge
Leaks and Cracks in Decorative Shotcrete
The Omaha Zoo faced a significant challenge when a decorative shotcrete structure, an integral part of the zoo’s aesthetic appeal, began showing signs of deterioration.
Cracks and leaks had developed, primarily due to an irrigation system installed above the structure. Water seepage through these fissures threatened the durability and appearance of the faux rock face, necessitating an urgent and effective repair solution.
The Solution: SealBoss 1510 Foam and P2002 Polyurethane Pump
To address the leaks and repair the shotcrete structure, a technical representative from SealBoss was called upon. The solution proposed involved the use of the SealBoss Water Stop System, specifically the 1510 Water Stop / Leak Seal Foam and the compact P2002 Injection Pump, along with SealBoss Evolution AL Packers (1/2″, 5/8 BH/Zerk).
The objective was clear: Seal the leaks in the shotcrete and repair the cracks effectively without compromising the structure’s aesthetic value. The SealBoss system was chosen for its proven efficiency in such scenarios.
The Process: Hydro Active Foam Injection Technique
The shotcrete leak seal repair process began with a thorough assessment of the structure to identify all visible voids and cracks. The SealBoss team then employed the hydro active foam injection technique, using the P2002 drill injection machine along with 1/2 AL & 5/8 injection packers.
SealBoss 1510 was injected into the shotcrete cracks until visible penetration was observed on the face of these cracks. This process required multiple injections at various points to ensure that the foam traveled deep into the cracks, forming a dense, closed-cell compression seal upon expansion. One of the remarkable observations during the process was the expanding foam pushing out from the cracks, indicating its excellent travel and coverage within the network of fissures.
The Outcome: A Leak-Free, Restored Structure
Following the injection process, the structure underwent a rigorous inspection to ensure that all leaks were sealed. The SealBoss system proved its efficacy, as the structure passed the inspection with no signs of leakage. The aesthetic integrity of the structure was maintained, with minimal visible impact from the repair process.
Training and Support
SealBoss offers in-person and video training for those interested in learning more about their products and techniques. This training is invaluable for professionals looking to enhance their skills in leak sealing and crack repair in shotcrete structures. Additionally, SealBoss provides access to regional technical representatives who can offer insights into the full range of system solutions and offerings.
Conclusion
The successful repair of the decorative shotcrete structure at the Omaha Zoo is a testament to the effectiveness of the SealBoss Water Stop System. This case study highlights the importance of choosing the right materials and techniques for repairing shotcrete structures. With the right approach, it is possible to extend the life of these structures while maintaining their aesthetic and structural integrity.
For those facing leaking shotcrete challenges, consulting with a SealBoss technical representative can provide tailored solutions to effectively address leaks and cracks in shotcrete.
SealBoss® provides PU water‑stop resins, acrylate gel systems, injection pumps, mechanical packers, and training to execute the sequences above. Share your drawings, leak rates, and access constraints—we’ll assist in proposing a port layout, gel‑time schedule, and material takeoff tailored to your project.
SealBoss ® P2002 Drill Operated Injection Pump Advantages
- Polyurethane Grout Injection Pump
- Polyurethane Foam Injection Pump
- Easy To Use
- Easy To Cean
- Easy To Maintain
- Modular, Compact &
- Sturdy Design
- Single Component
- Electric Drill Operated
- Heavy Duty For Daily Use
- Pressure Gauge, Hose Set, Hopper Included
- Recommended For Beginners & Injection Pros
- > 5000 PSI Injection Pressure Possible
Seal Leaks and Repair Cracks in Shotcrete – Frequently Asked Questions
Is shotcrete inherently leaky?
No. Properly placed shotcrete can be watertight. But its placement method increases the odds of defects (rebound pockets, laminations, honeycombs) that raise the risk of leakage versus CIP. Injection addresses those specific pathways.
Will PU alone fix my problem?
PU foam is ideal for stopping active water quickly. If the wall is generally permeable or seepage is diffuse, add an acrylate gel curtain to create a continuous barrier.
When should I consdider epoxy?
Only if specified and after water is controlled. Epoxy is for structural crack repair and requires dry conditions to bond properly.
What injection pressures should I use?
Start low and increase only as necessary. The goal is flow‑based infiltration along leak paths, not fracturing the concrete.
How will I know it worked?
No visible flow, a dry face after 24–72 hours, and no damp telegraphing beyond the grid.
In below grade structures damp spot or wet areas may show up later if water table rises or dried out soil becomes saturated. Water may migrate to areas that have not been treated.
