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
Scope of Work: Injection of polyurethane chemical grout through probes to rehabilitate and seal below-grade pipes from an exterior application.
Problem: Defects and joints in below-grade pipes allow for the infiltration of water into the pipe. This migration of water through defects that typically occur in pipe joints can cause an array of problems for the soil substrate and above-grade structures such as roadways, sidewalks, bridges and buildings. Access to the pipe is often limited and the rehabilitation or repair process often requires shutting down roadways, excavation and other time consuming options.
Solution: Injecting chemical grouts from outside the pipe is faster, cheaper and less disruptive than excavation and replacement.
IDENTIFY THE DEFECTS
Identifying where the infiltration is occurring is the most important step in a successful rehabilitation application from outside the pipe. In scenarios where the pipe is large enough to access by crew, the identification process can be simple. Entry into the pipe along with a detailed log and measurement of location and the type of leaks present is required. If access by crew is not applicable, secondary techniques will be necessary to identify defects and their location. Video or CCTV can be taken from the interior of the pipe in order to locate and identify defects / leaks. GPR (ground penetrating radar) may also be used as a supplemental tool for locating voids, leaks and defects.
INJECTION PROBE PREPARATION
Once defects / leaks have been identified, probes can be installed to precise locations for the injection of Prime Resins chemical grout. For shallow depths, probes may be as small as 3/8” in diameter. For instances of greater depth or harder, more dense substrates, 1/2” to 3/4” probes may be necessary to effectively drive probes to the defect location.
Probes should be installed to a distance of approximately 6” – 12” from the defect in the pipe. Prime Resins recommends using drive points when installing probes to inhibit soil from blocking the end of the probe. When probes have been installed to depth, lift pipes 1” – 2” to allow for the release of the drive point. This will allow Prime Flex chemical grout to flow freely into the substrate.
PREPARING PRIME FLEX CHEMICAL GROUT
Both Prime Resins hydrophilic and hydrophobic chemical grouts may be used in probe grouting from outside a pipe defect. When using a Prime Flex hydrophilic grout (900 XLV, Hydro Gel SX), the material can be injected directly from its original packaging with a single-component pump. For hydrophobic grouts (910 and 920), a catalyst must be thoroughly mixed into the resin with a rotary drill and paddle mixer. Prime Resins recommends using a minimum 5% by volume amount of catalyst when sealing leaks outside a pipe.
INJECTING CHEMICAL GROUT
Hammer (for driving probes)
Rhino or equivalent pneumatic hammer (for driving probes)