Polyurethane grouting uses expanding grouts to fill voids, correct settlement, densify soils, and stop leaks. From commercial floors to interstates, and everything in between, polyurethane grouting is economical, fast and effective for correcting settlement and instability.
How Polyurethane Grouting Works
Two polyurethane liquid components are mixed and injected (hence also being called polyurethane injection) under pressure below the area or structure being repaired. The two liquids react with each other, expand and harden, like the foam you get in a can to seal around windows. Our polyurethane grouts stay a liquid for a few seconds before expanding. This helps them spread out from the exact spot they’re injected, but then get harder much faster, and can exert much more force during expansion. We have developed our own line of polyurethanes, CJGrout. CJGrout polyurethane grout formulations are based on CJGeo’s extensive polyurethane grouting experience.
Advantages of Polyurethane Grouting
Polyurethane grouting excels compared to cement-based grouting primarily due to cleanliness, speed and control. These combine to reduce overall costs compared to cement-based grouting. Grouting with CJGrout geotechnical polyurethanes can be used in place of cement-based grouts for processes such as compaction grouting, slabjacking, void filling and leak sealing. Polyurethane grouting is…
- Polyurethane grouting is the cleanest concrete lifting and stabilization process. Because the injection equipment is mechanically connected to the slab or structure, and mechanical seals engage when not injecting material, no loose material is introduced to the repair area. Extruded material is easy to clean up because it cures very quickly.
- Polyurethane grouting is the quietest and fastest process for stabilizing and raising settled concrete slabs. Drilling is fast and quiet, and there is virtually no noise associated with the injection process itself. The equipment for polyurethane grouting is self-contained in a box truck. Equipment can be parked up to 400 feet away from any injection point.
- Foot traffic during work is functionally OK, and immediate resumption of vehicular traffic after work is completed can be expected. Polyurethane grouting is not affected by foot traffic during the injection process. Vehicular traffic may resume immediately after work is completed. This includes heavy loading such as trucks and industrial equipment like fork lifts, and even trains.
- CJGeo’s grouting crews can lift up to 12 times faster than standard slab jacking or mud jacking crews. Because of the small hole size and ability to lift larger areas per hole, polyurethane grouting is much quicker than slab jacking. Because of the equipment design, upon arriving on a job, polyurethane grouting crews are typically actively lifting slabs within 10 minutes of arrival for typical repairs.
- Lightweight material reduces the overburden on underlying soils, reducing the chances for resettlement. Even the highest density polyurethane foams used for polyurethane grouting are significantly lighter than alternative lifting and stabilization materials. This reduces the amount of additional burden weight placed on the underlying soils. Geotechnical polyurethanes are an excellent choice for lightweight fills, because of their exceptionally low unit weights (down to 2 PCF) and fast cure times (few minutes).
- High density polyurethane is waterproof, so treated slabs are thoroughly undersealed. Polyurethane can also be installed directly into water. So flow testing or water stop applications with active flows are not a problem. Because of the near-immediate curing, water stopping jobs are fast and easily tested on site to ensure efficacy of the repairs.
What Polyurethane Grouting Is Best For
There are many times when polyurethane grouting is the only repair process that will address a problem. Here are some of the times when polyurethane grouting is best:
- Large slabs (typically bigger than 100 square feet) are best repaired with polyurethane grouting. Polyurethane can travel under the entire slab from just one or two injection holes. This creates a more diffuse lifting force than cementitious grout. This speeds up work and lessens the chance of cracking.
- Faster reacting lower density foams typically start to expand within a few seconds of injection. They are good for concentrated lifting. Slower reacting, higher density foams can travel as a liquid for up to 45 seconds before starting to expand and harden. This allows them to lift extremely large areas. CJGrout is injected at 1100 psi, which forces it into what can be very small spaces under the slab.
- Because of its high expansion force and ability to spread under large areas of slabs and structures before expanding, high density polyurethane can lift extremely heavy slabs with ease. These include roadway slabs, bridge approaches, rail crossings and slabs with heavy loads, such as machinery bases and floors with backup battery power packs.
Areas where cleanliness is important
- Due to the small, infrequent holes, dustless drilling is easy. There is a mechanical connection between the injection equipment and the slab. Automatic, mechanical valves on the injection equipment prevent leakage of material when not injecting. We use special dustless drilling equipment for most interior jobs.
Load sensitive areas
- The most common cause of slab settlement is inadequate compaction or bearing capacity of the underlying soils. Because geotechnical polyurethane is lightweight (typically 2.5 to 6 pounds per cubic foot), there is very little additional weight transferred to the underlying soil as part of repairs. This helps to minimize the chances of resettlement. Sand-based and cementitious grouts used for slab jacking or pressure grouting typically weigh more than 100 pounds per cubic foot. The weight savings with polyurethane grouting are significant.
- High density geotechnical polyurethane is stored and transported as a liquid. It expands onsite as part of the injection process. A single non-CDL box truck can easily transport more than 100 cubic yards of expanded material. The equivalent for slab jacking grout would require more than 6 large dump truck loads and onsite handling equipment. Raw polyurethane material is transported in standard IBC totes. So is easily transported, stored and handled on job sites.
Materials Used For Polyurethane Grouting
CJGeo uses CJGrout polyurethane grouts.
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