Introduction to Polyurethane Injection

Polyurethane injection is arguably the most common injection type used for repairing leaks and waterstopping exclusively in poured concrete foundation walls and structures due to its versatility. When a leak repair/waterstopping is required in subway tunnels and mineshafts, the cracks and rock fissures are injected with polyurethane (also referred to as grout). Under certain conditions epoxy crack injection is a viable alternative to polyurethane crack injection.

Polyurethane injection involves the high pressure (typically 1500-3200 psi) injection of activated polyurethane through injection packers hammered into 3/8" drilled holes in the poured concrete structure. Like epoxy, the injected polyurethane travels through the entire thickness of the foundation wall (typically 8") thereby preventing water from entering the crack.

Polyurethane Injection Video

Typical Polyurethane Injection Applications

• Actively leaking cracks;
• Cracks in wet or damp basement walls;
• Previously repaired cracks (internally and/or externally) that are leaking; Note: an epoxy injection is not appropriate for use in the repair of a failed crack injection.
• Wide cracks (generally >1/8" in width);
• Cracks that are full of mud or mineral deposits;
• Cracks caused by corroding reinforcing bars (typically in reinforced concrete slabs);
• Leaking forming tie-rod holes;
• Leaking forming snap rods;
• Leaking I-beam pockets;
• Leaking underground structures in general (such as parking garages);
• Underground penetrations in a wall to accommodate electrical conduits, gas lines, air conditioning lines and pipes;
• Expansion joints;
• Honeycombing;
• Pool bottoms (when access is possible);
• Seams created by a cold pour;
• Overhead concrete structures; and
• Gaps beneath the window frame and the top of the concrete wall cut-out.

Images of Typical Polyurethane Injection Applications

Actively leaking crack	Failed crack injection	Previously repaired crack
Large foundation crack	Crack with mud and mineral deposits	Leaking forming tie-rod holes
Leaking tie-rod hole	Corroded snap rod	Leakage through i-beam pocket
Leaking pipe penetration	Leakage through honeycombing	Pool bottom waterproofing
Pourous poured concrete

The Attributes of Polyurethane Resin

From reviewing the typical applications above, it is clear that polyurethane injection is an extremely versatile waterproofing method that can be used to deal with any leak in a poured concrete structure, under all conditions. This versatility is attributable to the characteristics of our polyurethane resins which are:

• Activated polyurethane typically expands to 5 times it's volume; this is very desirable when filling large cavities or when the size of a cavity is unknown (as in the case of honeycombing);
• The expansive force of polyurethane is significant; consequently, it will fill any and all gaps that it encounters - this is particularly useful when dealing with very porous concrete or when dealing with honeycombing. It will also expand wherever it can; following the path of least resistance, it will fill any and all voids encountered;
• Our polyurethane resins are non-toxic. This makes them suitable for use with potable water systems such as cisterns;
• Polyurethane sets rapidly in the presence of hydrogen. Since hydrogen molecules are a component of water (H2O), the presence of water during an injection actually increases the reactivity of the polyurethane. This makes polyurethane the ideal product to use when active leaks and/or significant hydrostatic pressure, are encountered;
• The polyurethane resins that we use will not freeze and always remain flexible (not an attribute of all polyurethanes); this is desirable when the concrete surrounding it expands and contracts due to thermal cycling;
• Polyurethane sets very quickly. This is essential in stopping leaks where significant hydrostatic pressure is present;
• Polyurethane injections are conducted using hydraulic hoses which provide ease of use when accessibility to the repair area is limited; and
• At AquaGuard Injection & Waterproofing® we use polyurethane resins of varying viscosities; this gives us the ability to deal with any situation, from hairline cracks to large voids.

Note 1: Several technical factors need to be taken into account to determine whether a leak should be injected using epoxy or polyurethane; for example, the effects of tension and compression at the crack location must be factored into the decision on how best to deal with your leak repair. Their is alot of science behind injection repairs; trust our trained technicians to determine which repair type is best suited to your circumstances.

Note 2: Not all Waterproofing Contractors offer polyurethane injection waterproofing repairs. Why? Because it takes skill, knowledge, high quality polyurethane formulations, professional injection equipment and determination to perform a successful polyurethane injection; otherwise the injection will likely fail. As significant training and a commitment to work excellence is crucial, many companies shy away from polyurethane injections because they cannot reliably produce successful results. The demanding nature of polyurethane injection is such that some of our competitors call upon us to perform their warranty repairs!