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Crack Injection

Green Mountain Strong

An Overview Of Crack Injection

Water can find its way through the tiniest of cracks and concrete patches simply do not stand the test of time. Polyurethane crack injection is the most common and most effective repair technique for sealing cracks and stopping water leaks, both in the United States and abroad. Whether it is a crack in a major city’s subway system or in a residential basement, the method for pumping and sealing the crack is essentially the same.

Mountain Grout Polyurethane Resin is injected into cracks via a high pressure pump to fill and seal the cracks and cease water infiltration.

The basic steps are as follows:

Safety First: Read the Safety Data Sheet (SDS) and follow all precautions. Ensure that all present are wearing necessary Personal Protective Equipment (PPE) for the job.

Drill Holes: Installers use a hammer drill to bore holes in a stitching pattern at a 45 degree angle to intersect the crack at the midway point. The drill bit should be the same size as the diameter of the injection packer of choice. Spacing for the injection packers can be anywhere between six inches and twenty-four inches, depending on crack size.

Flush Holes: Flush the bore holes with water to remove concrete dust and ensure the entire area to be grouted is wet. The concrete that the installer has just drilled through is presumably dry, so wetting the area ensures that the polyurethane resin will foam in the bore hole and not just the crack. The flushing of the bore hole also cleans out dust that could inhibit the travel of the urethane resin and negatively impact performance.

Install Packers: Place high pressure injection packers into the holes. Mountain Grout offers 3/8” Tap-in Packers, ½” Mechanical Packers, 5/8” Mechanical Packers, as well as other custom sizes. The ball valve (grease fitting) on the end of the packer allows the resin to pump through the packer, into the bore hole, and ultimately into the crack. The packers act as a bulkhead for the bore hole, stopping foam from traveling back out the same hole into which it was just pumped.

Pump Resin: Polyurethane resin is pumped until it is seen at the crack face, then the installer moves to the next bore hold and repeats the process. The polyurethane resin reacts with the water in the crack to form a flexible, water tight foam. Installers will see the foam forming in a matter of minutes (in some cases, seconds) and the foam is fully cured in approximately 24 hours.

Remove Packers (if desired): Packers can be removed or left in the concrete as a reference point, depending on the owners’ preference. They can be knocked off flush with the concrete or drilled out if necessary.

Patch Bore Holes (if desired): If packers are removed, bore holes can be covered with mortar patches to provide a smooth, finished look to the concrete wall.

Polyurethane crack injection is the method of choice for sealing cracks in dams, tunnels, parking garages, elevator pits, wastewater treatment tanks, swimming pools, man holes, foundations, basement walls, and anywhere else concrete and water meet.

Polyurethane Crack Injection 

Part I – General

This specification is to detail the process of sealing cracks and/or joints with Hydrophobic Polyurethane Chemical Grout (HPCG).

  • A. Work Included: Include all materials, labor, tools, and equipment to perform repair of cracks/joints in concrete.
  • B. Delivery, Storage and Handling: 1. Deliver the specified product in original, unopened containers with the supplier’s name, product labels, product identification, MSDS, and batch numbers. 2. Store and condition the specified product as recommended by the supplier.
  • C. Job conditions: Precautions should be taken to avoid damage to any surface near the work zone due to mixing, handling, and/or placement of the specified materials.

Part II – Prepartation

The surfaces of floors, walls, etc. to be treated shall be cleared of all debris and attachments to allow free and clear access to the work, and also open access for monitoring of grout travel.

Part III – Application

A. Material
  • a. Hydrophobic Polyurethane Chemical Grout shall be Mountain Grout Flexible as supplied by Green Mountain International, Inc, 235 Pigeon St., Waynesville, NC 28786 (800-942-5151) or equal.
  • b. HPCG must be shipped as non-hazardous and contain no solvents or VOC’s.
  • c. HPCG must have been tested for potential leachate of heavy metals (soil contamination) under TCLP Extraction method 1311, Metals Method 6010 and Manual Cold Vapor Technique, Method 7470. Methods supplied by the USEPA office of Solid Waste and Emergency Response. d. HPCG pump cleaner/flush must be solvent free and non-flammable.
B. Application:

1. All cracks and/or joints shall be sealed with the HPCG.

  • a. Preparation: Holes shall be drilled at an approximate 45 degree angle, offset to intersect the joint/crack at approximate mid-depth or to a maximum of 18”. In thin concrete sections holes may be drilled directly into the joint/crack.
  • b. Application: Holes and Packer Devices: 2 styles of packers are acceptable, both available from Green Mountain International, Inc. i. 5/8” diameter holes shall be drilled for Mechanical Type Packers, which are inserted into the drilled hole and secured into place by an expandable rubber section as the packer is tightened. ii. 3/8” diameter holes shall be drilled for “bang-in” type packers, which are hammered into the drilled hole.
  • c. Hole Spacing: Holes shall be placed at appropriate intervals typically 12” apart to ensure full infiltration of the joint/crack with the HPCG. In narrow (hairline) cracks holes will be closer together. In wide cracks they may be farther apart. Visually monitor grout flow from outside of crack.
  • d. Mixing Procedure: HPCG shall be mixed by very gradually pouring component “B”, accelerator, into component “A” while carefully stirring so as to not entrain air into the mixture.
  • e. Placement: HPCG shall be pumped through a piston pump capable of producing discharge pressures of >250 psi.f. Crack may be actively leaking at time of application. This is, in fact, preferred. Pumping shall proceed from packer to packer, with multiple passes on each hole until either stall pressure is achieved or raw grout flow is observed from the crack/joint subsequent to pumping upon that hole.

2. Cleaning All excess HPCG shall be cleaned from the area and properly disposed. Leave finished work and work area in a neat, clean condition. (To be used as a general guideline. All projects are unique.)

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Green Mountain Grout International LLC, Member of the ICRI & Member of the ASDSO.