When you need to repair a crack in a concrete structure — such as a foundation or wall — from the inside (negative side) of the structure, there are typically two injection techniques and corresponding product technologies that you need to consider — epoxy resin injection and polyurethane chemical grout injection.
Epoxy injection is typically performed on dry substrates versus polyurethane injection that works very well on wet and actively leaking substrates. Epoxy injection is the preferred method where structural crack repair is desired.
Polyurethane injection is performed to seal active leaks, prevent moisture migration and to protect structures from corrosion and water related decay. Polyurethane injection technology is superior in most wet and actively leaking environments.
Let us compare some of the main characteristics of each type of crack injection, outlining their strengths and their recommended range of applications.
Injection Repair Conditions and Objectives
Epoxies and polyurethanes are chemical resins with different reaction profiles and physical properties.
Epoxy is a strong adhesive or glue that does essentially not expand. While curing epoxy creates a strong bond with the concrete substrate and ultimately provides a repair of high compressive and tensile strength properties.
Epoxy is a two component system, one component is the epoxy resin and the second is the hardener. The components are blended in the static mixer of the injection pump applicator immediately before crack injection. Injection epoxies cure chemically within a specified time and harden further over days and weeks.
Polyurethane injection foam is primarily a water activated sealant or leak-seal grout with expanding properties during reaction. The cured product creates a compression seal of varying flexibility.
Polyurethane foam resin often utilizes an activator or accelerator. Resin and activator are mixed before they are injected. Polyurethane resins are also available in two component chemical cure variants. No moisture needed.
Polyurethanes are extremely versatile. Their chemical and physical properties vary to suit the needs of specific applications and jobsite conditions.
Polyurethane resins vary from rigid and strong to flexible, rubbery and soft. The initial cure time for crack injection polyurethanes is generally 1 – 10 minutes and is influenced by accelerator usage, temperature and moisture availability.
Differences in The Epoxy and Polyurethane Crack Injection Processes
Epoxy crack injections are typically performed at lower injection pressures (20-200 psi) and with surface mounted ports.
Polyurethane crack injection is often performed at higher pressures to move the expanding foam through the cracks with special injection pumps and packers installed into drilled holes. The injected polyurethane is supposed to fill the crack through the entire thickness of the structure thereby preventing water from entering the crack.
Epoxy Crack Injection
Polyurethane Crack Injection
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