Epoxy.com Logo - Epoxy, Polyurethane, Polysulfide, Polyester, MMA - Methyl Methacrylate and other Construction Resin Systems - Over 350 Products- Since 1980
[Contact Us]

Epoxy Injection of Concrete and Wood

Repair of Cracks and Hollow Plains with Epoxy Injection

Epoxy Structural Concrete and Wood Repair / Waterproofing

The following article is written with enough information about resin injection systems to help protect the Owner from the misuse or improper installation of an injection systems.   For more information contact Norm Lambert.

One of the most versatile, problem solving products available in epoxy systems today is Epoxy Injection Resin. Epoxy.com Epoxy Injection of a bridge abutmentStructural restoration of concrete by epoxy injection is very often the only alternative to complete replacement. It therefore results in large cost savings. Injection protects the rebar and stops water leakage.

Epoxy injection of concrete cracks has been used for decades. When properly installed it is still working as well as it did right after it was installed.

Epoxy Injection Resin is a system for welding cracks back together. This welding restores the original strength and loading originally designed into the concrete. Epoxy injection restores the structural qualities the concrete design intended. In other words under most conditions it makes the concrete as good as new. It creates an impervious seal to air, water, chemicals, debris, and other contamination.

Other waterproofing injection systems like urethane resin will seal the crack from water but will not repair the the member structurally.  Not repairing a member structurally makes the member vulnerable to additional structural decay. This structural advantage that an epoxy injection repair gives, makes it the best choice for most situations.

A crack, obviously, is a sign of failure caused by stresses, inadequate design, improper curing, etc. One of the dangers of a structural crack is the effect that it has on the reinforcing bar. The reinforcing represents one of the main structural values of the concrete. Epoxy Injection of concrete

Cracks left unprepared allow moisture, road salts and other contaminants to penetrate and attack the rebar. The rebar deteriorates, losing the structural value. Loosing the entire structure is often the result. You can see this demonstrated in hundreds of neglected bridges across the U.S.

Epoxy injection resin has two purposes. First, it effectively seals the crack to prevent the damaging moisture entry. Secondly, it monolithically welds the structure together. Most people assume that this welding of the structure is the most important result of the repair. Actually what is most important is the sealing the rebar and preventing it from deteriorating.

The sealing properties of the injection prevents premature deterioration of the reinforcing. This can be of equal, or in some cases greater importance than the structural welding. It would theoretically always be desirable to get this welding effect.

Crack Analysis

As with all repair and rehabilitation of concrete, the initial job analysis is by far the most important step. Epoxy Injection Resin will weld concrete cracks but, of course, will not repair the cause of the cracking.

Analyze each potential injection application to determine the exact cause or causes of the cracking. Correcting the cracking problem can be fairly simple, or may be difficult involving design changes.

Consult a structural engineer when design changes are necessary. Do this before starting the injection. Repairing cracks by Injection is effective after these design changes. Prevent future cracks by fixing the original cause of the cracking, when ever possible.

Parking garages are an example of cracking problem that require a structural engineering analysis.Epoxy.com Epoxy Inection Often inadequate design for expansion/contraction is the cause for parking garage structural cracking. Avoid weld injecting a crack if there are not enough expansion joints. Sometimes flexible overlays such as Epoxy.com System # 495 can be used to overcome this defect. This does not however encapsulate the rebar in a way that will totally stop the premature deterioration of the steel. Often times additional joints are needed, thus the analysis of cracking problems is critical.


Injection Preparation

Proper job preparation is essential to insure maximum results. Preparation before injection is even more important. Once the resin is in the crack, there is no turning back. The two most effective systems for setting injection ports:

  • Surface Ports for General Purpose Use
  • Drilled
  • For Special Uses Applications

Port Setting

It is extremely important that if drilling to use the drill type ports that it be done with vacuum attached swivel drill chuck and hollow drill bits. Concrete dust can be detrimental to the injection processes in several ways.

Any dust remaining in the drill hole near a crack can combine with the very low viscosity injection resin, forming a semi-paste. This paste can slow or even block the resin flow. Drilling very tight crack with a solid drill forces dust into the crack. This seals the crack from resin flow. Do not allow shortcuts in the drilling procedures!  However, for most applications the surface port is the easiest and most effective method.

Determining the spacing of ports is done by a highly experience applicator. This spacing is a factor of the tightness of the crack and the depth of the concrete substrate. Spacing is normally between four (4) and eight (8) inches.

Port Setting and Sealing Epoxy Injection Surface Port

Align ports directly over cracks. That allows injection resin to flow into the crack. Seal surface cracks. Sealing the exterior of cracks is done with Epoxy Gel type Bonder.

Testing The System

Test cracks that are ill defined, or if dust or debris is in the crack. This testing may be done by injecting water into the crack area.

Water left in the cracks will not effect the injection process or the curing of the Epoxy.com Injection Resin. Heavier injection resin forces the water out the cracks. Water injection helps clean the cracked areas. More important, is that it helps avoid the unexpected. This process of flushing the cracks is commonly skipped by more experience contractors, who can tell if there will be a flow of resin, by just looking at them. However, when in doubt water testing is a must.

If the cracks contain algae, chlorinated water containing copper sulfate is injected. After pumping this mixture is left over night. The next morning the crack is flushed by pumping fresh water, into it. This flushes it out before resin injection begins.

Efflorescence builds up on the bottom of a crack in a horizontal slab. Water in the crack extracting soluble calcium hydroxide is the cause. The water evaporates at the surface leaving the lime, which later reacts with the carbon dioxide in the air to form limestone. The inside of the crack, is frequently free of limestone and making it suitable for injection.

Epoxy Resin Properties Epoxy.com Product #301

Mix Ratio 2:1 By Volume
Viscosity 400-450 cps
Initial Cure 6 - 8 hours (with normal cure hardener)
Final Cure 24 hours
Pot life 30-40 minute (with regular cure hardner)
Packaging (unit size) 3 gal unit, 15 gal unit, 165 gallon unit
Standard Colors clear
Colors Clear - Can be pigmented at an additional charge to make it easier to see when pumping.

Elongation (ASTM D-638) Greater than 10%
Compressive Strength (ASTM D-695) 10,000 PSI (min)
Tensile Strength (ASTM D-790) 3,500 PSI
Concrete Bond Strength (ASTM C-882) 2,290 PSI
Shrinkage (ASTM C-883) Passed Test
Thermal Compatibility (ASTM C-884) Passed Test
Adhesion to Concrete (ACI Committee 403) 250 PSI (concrete fails)


Resin Injection

Epoxy resin injection with any industry standard 2:1 injection machine or Epoxy.com Injection Gun  designed for Epoxy.com Injection resin is the only way of assuring quality installation. Single component caulking guns, pressure pots, or similar batching equipment are not suitable for injection.

Manual Epoxy Injection GunAs an alternative to an epoxy injection machine, Epoxy.com offers 450 ml binary injection system. This uses a binary caulking gun and static mix tubes to inject thisresin.

Epoxy Concrete Injection

Limit pressures to 40 p.s.i for most applications. Excessive pressures can create additional stressing of the crack. It can also cause hydraulic lifting, rupturing of the cracked substrate, or further elongation of the crack. Low pressures allow gradual resin flow into the crack for deeper penetration. On vertical cracks, injection is start at the lowest point, and continue upward on the crack area. While injecting the lowest port, resin will flow to and out of the next higher port.

When pure resin is flowing out the next port cap, plug the current injection port and move to the next port. Then injection continues in the port showing resin flow. This procedure continues until all ports are full.

Epoxy Injection Resin Systems should be of very low viscosity for most applications. That way it will flow in the smallest hair line cracks. Resin can travel several feet from the point of injection. It may take some time before reaching the next port or penetrating through pin holes in the surface. Coring samples have shown that epoxy injection effectively fills cracks including small voids and hairline cracks.

Injection During Extreme Weather Epoxy Injection of Epoxy

A cold substrate will cause an increase in the viscosity of the injection resin. This slows down the rate of injection. A hot substrate results in premature jelling of the resin with sequential loss of penetration. During extremely hot weather an open bridge deck may exceed temperatures as high as 140 Degrees F. Special precautions are necessary before injection work can be done in such weather.

The precaution may be shading the bridge, and water cooling. Always check substrate temperature. The injection machine and its hoses require isolation from extremes of temperature.

Epoxy injection undertaken during cold weather also requires special precautions.

When doing injection work in freezing conditions, determining if there is ice present in the crack is critical. Determining if a cracks inner surfaces are ice coated, is equally important. When injecting under theseClose up of epoxy inection port setting at the Hush House at the Vermont Air National Guard conditions, the resin will not bond to the substrate and no structural rebonding will result. It is usually safer to preheat the portion of the structure you are injecting.

When heating a structure do not overheat it. This closes the crack. When removing heat, the crack may rapidly open. This will rupture the resin before it has a chance to achieve final cure. In most cases, indirect heating is much more desirable than direct heating. Maintain heat for several hours before and after the injection application.


The color of the sealer material used in resin injection is concrete gray. They are difficult to remove. If aesthetics require complete cleaning, the sealing material can be removed by grinding. This is normally done at an additional charge to the OWNER.

Injection Against A Head of Water Epoxy injection of the Hush House at the Vermont Air National Guard

Injection of Epoxy Injection Resin against a head of water requires a slightly different procedure than normal injection. If water is running from a crack, applying a hydraulic cement (fast setting) seals the cracks and sets the ports. Epoxy pastes will not set up under this type of wet condition. The hydraulic cement seals the cracks and diverts all water flow through the injection ports.

Hydraulic cement is fast setting, but it does not have the strength needed for an Injection Sealer. Epoxy Concrete Bonder can have the strength to prevent blowouts or leaks while injecting. After the hydraulic cement cures applying Epoxy Concrete Bonder. That solves this problem.

The injection process follows the procedures described before. The Injection resin forces the water out of the crack and through the adjacent ports. The resin has an amber color and does not look like water. Pure resin flows from the higher port before capping and moving on. The head of water will require increasing the injection pressure used.


Delamination of concrete structures is an area where injection can also offer selective repair. A prime example is bridge decks or other self supporting structures. The most common delamination is shearing of the concrete. This is commonly at the upper rebar mat.

Another common situation is hollow plane that develop when concrete bridge piers are resurfaced. Old piers are encased in new concrete. Hollow planes in this type of application are common, especially against smooth sections of the old pier. Cracking then occurs on the surface perpendicular to the hollow plane.

These delaminated area is subject to chemical penetration from the surface and moisture which may attack the reinforcing bar. If the delamination is not repaired, traffic will cause the area to pop-out by pounding on the delaminated upper concrete layer. Freeze-Thaw damage will also tear the concrete apart. The greater the number of freeze-thaws, the more water in the cracks during these free-thaws, the greater, and quicker the damage to the concrete.

Map delaminations by drag chain, hammer or sounding device. The damaged area requires no less than four (4) ports drilled for resin flow, depending on the size and shape of the delamination. This prevents the trapping of water that may be present.

The delamination is normally hollow planes that run along the reinforcing bar. When injecting the delamination, the resin will follow these hollow planed areas and can travel several feet in filling the voids.


Epoxy Injection Systems is very effective at repairing concrete cracks, delaminations, and hollow planes when used according to manufacturers recommendations. Job analysis and proper preparation are very important to insuring the maximum performance from the Epoxy Products, or any other concrete repair products. The right equipment is critical. Proper setup continuous mixing epoxy injection machines must always be used with no exception. Injection staff and management must have the training and experience to do the work right the first time. Epoxy injection has to be done right the first time. There is no second chance. So it is critical that your injection work be done by well trained and equipped, experienced personnel.

Epoxy.com Injection Products

Injection Resin

Product #301 Injection Resin, low Modulus - a 100% solids low viscosity epoxy adhesive used to restore cracked structural concrete by the pressure injection method and to grout cracks in a horizontal plane by gravity.

Product #301SC Slow Cure Injection Resin Low Mod is a longer Potlife version of Product #301

Product #301Cold Temperature Cured Epoxy Injection Resin a faster version of Product #301 typically used in Cold Temperature Cure applications, or where a very fast set is needed


Contact Epoxy.com Technical Support Department for more information on Injection and Binary Delivery Systems

  • Manual Injection Pump
  • Injection Ports
  • Binary Tubes 75 ML
  • Binary Tubes 150 ML
  • Binary Tubes 300 ML
  • Static Mixing Tubes for Binary Tubes
  • Manual Gun for Binary Tubes
  • Pneumatic Gun


Proper mixing and installation is critical to the optimal success of all products.  See Installation Tips, Techdata, & MSDS for more details on our products.  Be sure to contact us with any questions and/or concerns that you have.

For more information please contact:

A Division of Epoxy Systems, Inc
A Vermont Corporation

We have products that have passed the test of time as well as the best new Systems available today.

Since 1980 - 40 years of the highest quality products

Hours: 9AM-4PM Eastern Time (6AM-1PM Pacific Time)

Closed for lunch from 12Noon to 1PM

321-206-1833  Customer Service - Ordering and Order Status
                         Katey Lambert-Fontaine, VP - Chief Operations Officer

                        Technical Support
352-533-2167  Norm Lambert, President - Technical Support Director 

352-489-1666  Accounting and Administration
                         Debby Lambert, CEO, and CFO

Copyright © 1994-2023 (providing online information about the right product for the right job for nearly 30 years)  EPOXY.COM a division of Epoxy Systems, Inc. - Florida and Vermont.  All rights reserved.

We accept MasterCard, Visa, American Express, Discover, Wire Transfers, and Cashiers Checks
We accept MasterCard, Visa, American Express, Discover, or Wire Transfers.