Can you make epoxy injection repaired cracks in concrete disappear? This is a difficult challenge,...
Do you always consider alternative porting methods as you prepare to execute an epoxy crack injection repair project?
Maybe not. Yet the method selected by your field technician may make a significant difference in the quality, linear footage productivity and job profitability. Many crack injection specifications intentionally leave port selection and type as a field selected option to be determined by the practical experience and judgment of the concrete repair contractor. Some epoxy injection specifications call for a minimum of 90% of the crack length to show epoxy and some specifications require proof by examination of cored specifications, so port selection is often more critical for these specifications.
With a goal of filling (injecting) a crack with epoxy quickly, neatly, and completely, several factors to consider are:
- Crack width and substrate thickness
- Application temperature and moisture
- Orientation (ceiling, wall or floor)
- Gross linear footage
- Access limitations
- Surface appearance after repair
- Average time duration on port
- Choice of surface seal material (epoxy vs. other)
Many of our concrete restoration contractors use a combination of several porting methods:
Taped surface ports
Low cost ports are quickly established as gaps in the epoxy surface seal with quarter inch masking tape applied at the proper interval prior to the surface seal. The tape is pulled before the seal hardens completely. Using hand pressure, the injection mix head directly contacts the open gaps left by the tape though a compressible rubber grommet or rubber tip such as our part # B07 which is available in two sizes (see next image below). After the port is filled, soap or wax is manually rubbed over the crack to seal the port. Some of the long time specialty concrete repair contractors insist that this method is the most efficient practice for most crack injection projects. This method is illustrated in the top image for use on an industrial floor and in the second image (to the left) in conjunction with our peelable surface seal StripSEAL.
Rubber tips, pins, wire, (finishing) nails, straws, golf tees and toothpicks
These alternatives to tape often require no drilling. Sometimes they are used in combination. For example, rubber tips (such are our part # B07-3 or B07-12) can be located along the crack with toothpicks, (or pins or nails) prior to the seal application. To inject, the toothpicks are withdrawn and the mix head nozzle is inserted into the tip. Conical shaped golf tees work better than standard tees (because of their thicker shaft) but are hard to find.
Injection molded of PE plastic or nylon, surface ports for crack injection
have become very popular in the last 10 years. These consist of a flat base flange perpendicular to a small diameter tube for easy connection to the injection equipment using a 1/8” NPT press-to-fit connection. Although more costly from a disposable parts cost standpoint, field technicians appreciate the benefit of not having to manually hold the injection head against the port, particularly on ceilings or overhead cracks or when time on each port will be high.
Packers, Zerk fittings and grease fittings
These port options for epoxy injection are popular when high pressures are used and are standards for use with chemical grouting, a term usually affiliated with polyurethane (PU) injection. PU chemical grouting is a viable material option for waterproofing and leak-proofing but is usually not considered for structural repairs because it does not meet structural load bearing requirements such as ASTM C881, Type IV. Almost always these types of port connections are a most expensive cost option and are used with a drilled hole (see below). These connectors are often self-sealing with a spring loaded ball so the field technician doesn’t have to worry about material leaking from an uncapped port.
Drilled Injection Ports
Port connections for drilled holes can be made by the contractor at low cost by cutting sections from 1/4 or 3/8” polypropylene supply hose (same as used for the water supply line for an icemaker), purchased as pre-molded units or supplied as a tapered Semko® tip. This method is one of the first choices when injection flows are obstructed by the type of crack, surface obstructions, plugging, or for accessing voids under a sound surface (such as a de-bonded topping slab). If the crack is narrow, a 1/2" diameter water-flushed core bit is far superior to an impact bit for drilling port holes as it is less likely to pack the crack around the hole with drill fines (leading to more obstruction).
