epoxy.com

Choose the repair resin by matching the product form to the defect: low-viscosity epoxy injection for fine cracks that need to be re-bonded and sealed, structural epoxy gel adhesive for vertical or overhead bonding and crack filling where the material must stay in place, and epoxy mortar for spalls, voids, and larger missing sections. Then confirm the resin suits the concrete's moisture condition, gives you enough working time at the site temperature, and is compatible with the substrate and any coating that follows. Epoxy.com's catalog separates these categories — epoxy injection, structural epoxy gel adhesive, epoxy mortars, and joint/crack fillers — which is the right way to start narrowing the choice.

Match the product form to the defect

Structural repair is not one product. The three main forms behave differently and are not interchangeable.

Epoxy.com lists these as distinct lines — "Epoxy Injection," "Structural Epoxy Gel Adhesive," and "Epoxy Mortars" with a "Novolac Epoxy Mortar Resin" and "Chemical Resistant Epoxy Binder" — so treat the catalog category as your first filter, not the brand name.

A common mistake is reaching for a coating or sealer to fix a structural crack. Coatings and sealers are surface materials; they do not restore load transfer. If the crack is moving or the concrete is unsound, a rigid structural resin may not be the right answer at all — that is a condition to flag before buying, not something a product choice can fix.

Decide between injection, gel, and mortar

Use this sequence:

1. Is material missing, or is it just separated? Missing volume (spall, void, broken corner) → epoxy mortar. Separated but intact → injection or gel.
2. How wide and how oriented is the crack? Tight, roughly horizontal or accessible cracks → injection. Vertical, overhead, or wide enough that liquid runs out → structural gel.
3. Does the repair need to carry load across the crack? If yes, use a structural-grade injection resin or gel adhesive, not a filler or sealer. Epoxy.com's "Epoxy Joint Filler," "Crack Filler," and "Joint Water Tight" products sit in the joints category — confirm from the technical data whether a given filler is structural before relying on it for load transfer.
4. Will the repair be coated or overlaid later? Check compatibility with the planned coating or topping; a repair resin that is incompatible with the finish can cause adhesion failure later.

Select for site conditions

• Moisture. Dry concrete and damp concrete are different selection criteria. Epoxy.com's catalog includes a "Wet To Dry Concrete Adhesive" and an "Anti-Moisture Entrapment System," which signals that moisture condition is a real branch point. Do not assume a standard structural resin is suitable for actively wet or damp substrate — verify against the product's technical data.
• Temperature and working time. Cure speed and pot life shift with temperature. A fast-cure gel that is convenient in a cool shop can gel too quickly in a hot space; a slow resin can drain out of a vertical crack before it sets. Pick the cure profile for the temperature you will actually work in, and mix only what you can place within the stated working time.
• Access and method. Injection requires ports, surface sealing, and usually pressure equipment. Gel and mortar are placed by trowel or hand. Choose the method you can actually execute correctly — a poorly executed injection is worse than a well-executed gel repair.
• Chemical exposure. If the repaired area will see chemicals, Epoxy.com's novolac and vinyl ester lines are the relevant families to compare; standard structural resins may not be the right choice there.

Verify before you buy

• Pull the technical data sheet and SDS for the specific product, not just the category page. Confirm viscosity or consistency, cure time at your temperature, compressive/bond strength, and any substrate moisture limits.
• Confirm the primer or surface preparation the data sheet requires. Epoxy.com lists primers and sealers separately ("Epoxy Primer/Sealer," "Chemical Resistant Epoxy Primer"), and some mortars and adhesives call for a primer bond coat.
• Check compatibility with the subsequent coating or overlay, and with the concrete itself (age, condition, contamination).
• Confirm the product is intended for structural repair, not just crack filling or cosmetic sealing.

Common failure causes and how to catch them

• Insufficient surface prep. Dust, laitance, oil, or loose concrete defeats any resin. Roughen and clean per the data sheet; for injection, clean the crack and seal the surface so resin does not escape.
• Wrong mix ratio or incomplete mixing. Two-component systems fail if ratio or mixing is off. Follow the stated ratio exactly and mix the full batch; partial or rushed mixing leaves soft, uncured pockets.
• Crack not cleaned or too narrow for the resin. Match resin viscosity to crack width; a resin too thick for a hairline crack will not penetrate.
• Wrong product for wet conditions. Using a dry-substrate resin on damp concrete is a predictable bond failure — select a product rated for the moisture condition.
• Too much or too little working time. Mixing more than you can place, or working in heat that shortens pot life, produces a repair that never properly consolidates.
• Troubleshooting: if a repair fails to cure, check ratio and mixing first, then temperature and product age. If it cures but debonds, check substrate prep and moisture. If injection does not fill the crack, check surface sealing, port spacing, and resin viscosity.

For a specific project, start from the Epoxy.com category that matches the defect — injection, structural gel, or mortar — then confirm moisture suitability, cure profile at your temperature, and primer/coating compatibility against that product's technical data before ordering.

Epoxy is a two-component reactive resin system: a resin and a hardener are mixed in a specified ratio, and the chemical reaction converts the liquid mix into a hard, strongly bonding solid. Choosing the right system means matching three things before you buy: what the epoxy must do (coat, bond, repair, seal, or build a floor), what it must resist (chemicals, moisture, traffic, temperature), and what substrate it goes on. Epoxy.com, a division of Epoxy Systems, Inc. and a Vermont family-owned company operating since 1980, organizes its catalog around exactly this logic — "The Right Product for the Right Job" — with separate families for coatings, adhesives, structural repair, injection, sealers, mortars, and flooring.

How a two-part epoxy system works

The resin and hardener are sold as separate components and only become epoxy when mixed. Three practical consequences follow:

• Mix ratio is part of the product, not a suggestion. Off-ratio mixing leaves unreacted material — tacky, soft, or weak spots that no amount of curing time fixes.
• Pot life and cure time are different numbers. Pot life is how long the mixed batch stays workable; cure time is how long until it hardens and can be walked on, coated, or loaded. Warm conditions shorten both.
• "100% solids" matters for coatings. A 100% solids coating leaves essentially no solvent to evaporate, so one application builds a given thickness without shrinking. Epoxy.com lists 100% solids coatings and 100% solids flooring as distinct catalog categories.

Match the product family to the job

Epoxy.com's catalog separates systems by function. Use this as a starting map:

A single project often needs more than one family — for example, a primer/sealer, then a coating, then a joint filler. The catalog is built to be combined as complete systems as well as bought individually.

Selection factors that decide the outcome

Chemical exposure

If the surface will see solvents, acids, or aggressive spills, standard epoxy coatings may not be enough. Epoxy.com distinguishes standard chemical resistant coatings from highly chemical resistant novolac coatings and flooring, and also offers vinyl ester coatings for severe service. Pick the resistance class from what will actually contact the surface, not from the general label "chemical resistant."

Moisture and substrate condition

Moisture is the most common hidden failure. The catalog includes an anti-moisture entrapment system, a clear moisture vapor system, and an oil stop primer — signals that substrate moisture and contamination need to be addressed before a coating goes down. For bonding to concrete that is still damp, the wet-to-dry concrete adhesive exists precisely for that condition.

Solids content and build

100% solids systems build film without solvent shrinkage and are the default for flooring and wall coatings where thickness and chemical resistance matter. Lower-solids products are used where penetration or a thinner film is wanted.

Cure speed and working time

The catalog spans fast-setting products (super fast cure joint material, semi-flexible fast setting gel for waterproofing) to standard-cure coatings and mortars. Fast cure helps when downtime is short; slower systems give more placement time on large areas. Match this to your crew size and the area you can finish within one pot life.

Traffic and service environment

Garage and residential floors, industrial plant floors, mechanical rooms, and commercial kitchens place different demands. Epoxy.com lists dedicated categories for epoxy garage floor coating, industrial floor coating, mechanical room flooring, and elastomeric decking — use the category that matches the service, not just the color.

Basic application sequence and where it goes wrong

1. Prepare the substrate. Concrete must be clean, sound, and profiled; coatings and adhesives need an open, uncontaminated surface. This step causes most failures, and no epoxy compensates for a weak or dirty substrate.
2. Address moisture and contamination first. Use the primer/sealer or moisture vapor system appropriate to the reading, or the oil stop primer where oils are present.
3. Mix strictly to the stated ratio and use the batch within its pot life. Discard material that has started to gel — do not thin it.
4. Apply in the specified build. For 100% solids coatings, film thickness is set by the amount applied per area, not by repeated thin passes.
5. Respect recoat windows and cure time before foot traffic, vehicles, or a topcoat.

Common failure patterns and their usual causes:

• Tacky or soft cure — wrong mix ratio, incomplete mixing, or application below the minimum temperature.
• Coating lifting or blistering — moisture in the slab or poor surface preparation; the moisture-control products above exist for this.
• Poor adhesion on repairs — crack or joint not cleaned and opened enough before injection or filler.
• Short working time on a large floor — batch size too large for the pot life; split into smaller mixes.

Where to verify before ordering

Epoxy.com publishes installation guides, installation tips, guide specifications, and MSDS/technical data alongside the product catalog, plus an ordering information section. Before committing to a system, confirm the specific product's technical data sheet for mix ratio, coverage, cure times, and chemical resistance, and check the ordering page for current terms. For projects with unusual chemical exposure or structural repair requirements, the guide specifications and technical resources are the place to confirm the system meets the service condition.

Epoxy resin is a two-component system: a resin and a hardener that react chemically to cure into a hard, durable solid. Choosing the right system means matching the product to your substrate, chemical exposure, moisture conditions, traffic level, and whether the job is indoors or outdoors. There is no single universal epoxy — Epoxy.com, a division of Epoxy Systems, Inc. operating since 1980, organizes its catalog around this principle with the tagline "The Right Product for the Right Job." The selection sequence below walks you from job conditions to a compatible primer, body coat, and sealer.

How Epoxy Resin Works

When resin and hardener are mixed in the correct ratio, they react and cure — they do not simply dry. The cured material bonds to prepared surfaces and forms a solid film or body. Because the chemistry varies by formulation, different systems produce very different results: a clear coating, a chemical-resistant flooring, a structural adhesive, or an injection resin are all epoxies, but they are not interchangeable.

This is why product selection matters more than brand loyalty. A coating formulated for a garage floor will not perform as a structural adhesive, and a fast-setting injection gel will not work as a floor coating.

Common Epoxy System Categories

Epoxy.com's catalog groups products into families that map to distinct jobs:

Match the System to the Job Conditions

Before choosing a product, identify the conditions the epoxy must survive. The catalog's structure reflects these variables:

• Surface type — concrete, metal, wood, or stone each need a compatible primer and body coat. Concrete crack healing and joint filling are separate steps from coating.
• Chemical exposure — for harsh chemicals, the catalog separates standard chemical-resistant coatings from highly chemical-resistant novolac and vinyl ester systems.
• Moisture — wet or damp concrete calls for moisture vapor systems or anti-moisture entrapment primers; underwater repairs use a dedicated underwater epoxy.
• Traffic — industrial flooring, mechanical room flooring, and residential garage floors are different systems with different durability demands.
• Indoor or outdoor use — UV-resistant acrylic sealer and urethane sealer appear in the catalog for exterior or UV-exposed applications, while standard epoxies may chalk or yellow outdoors.
• Static control — conductive and ESD coatings and flooring are a separate family for electronics or explosive environments.

Why There Is No Universal Epoxy

Wrong product selection is a leading cause of adhesion failure and curing problems. A coating applied over a damp slab without a moisture vapor system may blister. A standard epoxy used where chemical resistance is required may soften. An adhesive used as a coating — or vice versa — may not cure properly or may not bear the load. The catalog's separation of primers, body coats, and sealers exists because each layer has a job, and the layers must be compatible with each other.

A Practical Selection Sequence

1. Identify the substrate and its condition. Note whether it is concrete, metal, wood, or stone, and whether it is dry, damp, or cracked.
2. List the service conditions. Chemical exposure, traffic, moisture, UV exposure, and static-control needs.
3. Choose the system family. Use the table above to narrow to coatings, flooring, adhesives, mortars, sealers, injection, or waterproofing.
4. Select a compatible primer, body coat, and sealer. The catalog groups these as complete systems; mixing families without checking compatibility risks failure.
5. Verify with technical data before ordering. Review the product data sheet, installation guide, and safety data (MSDS/SDS) for mix ratios, cure times, and application limits.

Before You Order

Epoxy.com provides product catalog pages, installation guides, installation tips, guide specifications, and MSDS/technical data sheets. Check the data sheet for the specific product you intend to use — mix ratio, pot life, cure time, and substrate preparation requirements — and confirm the system is appropriate for your conditions before purchase. For complex or high-exposure jobs, the specifier's information and technical resources sections are the place to start.

An epoxy hardener (also called a curing agent) is the second component of a two-part epoxy system. It reacts chemically with the epoxy resin to turn a liquid into a solid, durable material. You choose the right hardener by matching it to the product system and application: coatings, adhesives, structural repair, or chemical-resistant flooring. The most important rule is to use the hardener supplied with that specific resin and follow the manufacturer's mix ratio exactly. Epoxy.com, a division of Epoxy Systems, Inc., describes its business as providing two-component resin systems and "The Right Product for the Right Job," which reflects this system-matching principle.

How an Epoxy Hardener Works

Epoxy resin alone does not cure. The hardener contains reactive groups that cross-link with the resin's epoxide groups, forming a rigid thermoset network. The ratio of resin to hardener is set by the chemistry of that pair, not by convenience. Changing the ratio does not make the epoxy "stronger" or cure "faster" in a useful way; it leaves unreacted material and produces a soft, sticky, or brittle result.

Two practical consequences follow:

• Mix ratio is system-specific. A 2:1 ratio on one product says nothing about another. Always use the ratio on the product's own technical data.
• Mixing must be thorough. Incomplete mixing leaves streaks or soft spots even when the ratio was correct.

Matching Hardener Choice to the Application

The hardener is part of a formulated system, so the practical choice is usually the system, not a standalone chemical. Epoxy.com's catalog groups products by job, which is a useful way to think about selection:

Within a product line, hardener type and ratio drive cure speed, pot life, and final properties. Faster-curing systems shorten working time; slower systems give more placement time. The product data sheet is the authority for both.

Common Mixing Mistakes and Their Symptoms

• Wrong ratio: soft, tacky, or weeping surfaces that never fully harden.
• Partial mixing: sticky streaks, cloudy patches, or uneven hardness.
• Adding solvent or extra resin to stretch the batch: permanently weak or uncured film.
• Mixing too large a batch for a fast system: material gels in the container before use.

If a cured sample feels rubbery, stays tacky after the stated cure time, or shows visible swirls, suspect ratio or mixing before anything else.

Safety and Handling Basics

Hardeners are reactive chemicals. Follow the product's safety data sheet for gloves, eye protection, ventilation, and skin contact. Avoid breathing vapors in enclosed spaces, and keep resin and hardener away from incompatible materials during storage. For any specific exposure or disposal question, use the manufacturer's SDS rather than general assumptions.

Quick Decision Guide

1. Identify the job: coating, adhesive, structural repair, or chemical-resistant flooring.
2. Select the product system built for that job, using the supplier's catalog categories.
3. Use only the hardener supplied with that resin.
4. Measure by the ratio on the technical data sheet, mix fully, and observe the stated pot life and cure time.
5. Test a small area first on repairs and coatings before committing to the full project.

For projects where chemical exposure, structural loading, or moisture is a factor, confirm the system choice with the manufacturer's technical resources before ordering.

Structural repair epoxy is a load-bearing adhesive system used to restore or transfer force across a concrete repair, while regular epoxy (coatings, sealers, general-purpose glue) is not formulated to carry structural load. Choose a structural product form based on the repair geometry: gel adhesive for vertical or overhead bonding, injection resin for cracks, paste for filling and patching cracks, and mortar for spalls and larger voids. Before selecting, confirm the repair needs structural load transfer rather than cosmetic sealing, and check substrate condition (wet vs. dry), crack width or movement, and cure time against your application limits.

What Makes an Epoxy "Structural"

Structural repair epoxy is judged by what it must do in service, not by the word "epoxy" on the label. A structural repair must:

• Transfer load across the repaired section so the concrete behaves as a unit again.
• Bond to the substrate strongly enough that the bond, not the adhesive, is not the weak link.
• Fill the repair volume completely, with no voids that concentrate stress.

General-purpose epoxy glue, coating epoxy, and sealer are formulated for surface protection or light bonding. They may look identical when mixed, but they are not selected on structural criteria. Epoxy.com's catalog separates these categories explicitly: coatings and sealers sit in one group, while structural products appear under adhesives and repair items such as Structural Epoxy Gel Adhesive, Epoxy Injection, Epoxy Paste, Epoxy Mortar Resin, and Wet To Dry Concrete Adhesive. That catalog structure is the practical signal: if the product is listed as a coating or sealer, do not assume it is a structural repair resin.

The load-transfer question comes first

Ask one question before choosing any product: does this repair need to carry load, or only seal the surface?

• Load transfer needed (structural crack in a slab, beam, wall, or joint; delaminated section; spall in a load path): use a structural repair product form.
• Cosmetic sealing only (hairline crack that is not moving and carries no load, surface blemish): a sealer or coating may be appropriate, and a structural resin is overkill.

If you cannot answer this question confidently, treat the repair as structural until an engineer or the product technical data says otherwise. The cost difference between a sealer and a structural resin is small compared with a repair that fails because the wrong product was used.

Match the Product Form to the Repair Situation

The table below maps common concrete repair situations to the product forms Epoxy.com lists. Use it to narrow the catalog before checking technical data.

Two practical notes on this table:

• Gel vs. injection vs. paste are not interchangeable. A gel adhesive is for bonding surfaces and holding position; an injection resin is for penetrating and filling a crack; a paste is for filling and shaping. Choosing the wrong consistency means the product either runs out of the repair or never reaches the crack tip.
• Mortar is a system, not a single can. Epoxy mortar resin is combined with aggregate to build volume. Check the technical data for the mix ratio and aggregate requirement before ordering.

Check Substrate and Crack Conditions Before You Buy

Product form is only half the decision. The repair conditions determine whether a given product will perform.

Wet vs. dry concrete

Standard structural epoxies generally require a dry substrate for bonding. If the concrete is damp or wet, a standard adhesive may not develop its intended bond. Epoxy.com lists a Wet To Dry Concrete Adhesive for exactly this condition, which tells you the catalog treats substrate moisture as a product-selection criterion, not an installation detail. Confirm the substrate condition on site before ordering, and if it is wet, select the product rated for it rather than trying to dry the surface and hope.

Crack width and movement

• Cracks that are not moving can be filled and bonded with injection resin, paste, or gel depending on orientation and access.
• Cracks that are moving (active cracks, joints with expected movement) are a different problem. A rigid structural epoxy will not accommodate movement; the catalog includes joint and crack products such as Epoxy Joint Filler, Epoxy Novolac Chemical Resistant Crack Filler, and Semi-Flexible Fast Setting Gel for situations where rigidity is not appropriate. If the crack is active, do not default to a rigid structural resin.

Cure time and application limits

Cure time affects when the repair can be loaded, coated, or returned to service. The catalog includes fast-cure options (for example, Super Fast Cure products and a Semi-Flexible Fast Setting Gel), which matter when the repair must be returned to service quickly or when temperature affects cure. Check the technical data for the specific product's cure schedule and application temperature range before committing to a schedule. A product that cures too slowly for your window, or too fast to place, is the wrong product even if the chemistry is right.

A Worked Example

Suppose a concrete wall has a vertical crack that must be bonded so the wall acts as one section again, and the crack is dry and not moving.

1. Confirm load transfer is needed. The crack is in a wall that must behave as a unit, so yes.
2. Note the orientation. Vertical surface, so a low-viscosity injection resin may run; a gel adhesive is the better fit for holding position on vertical work.
3. Check substrate. Dry, so a standard structural adhesive is acceptable; no need for the wet-to-dry product.
4. Check movement. Not moving, so a rigid structural product is appropriate.
5. Select the form. Structural epoxy gel adhesive, with technical data checked for cure time and application temperature.

If the same crack were in a floor slab and needed full-depth penetration, the injection resin would be the better form. If the wall had a spalled area rather than a crack, the mortar system would be the choice. The decision process is the same each time: load transfer, orientation, substrate, movement, cure.

Common Pitfalls

• Using coating epoxy as a structural adhesive. Coatings are formulated for surface protection; they are not selected on structural bonding criteria. Check the catalog category before assuming.
• Using a gel where injection is needed, or vice versa. Consistency determines whether the product reaches the crack tip or stays where you put it.
• Ignoring substrate moisture. A dry-substrate adhesive on damp concrete may not develop its bond. Match the product to the condition on site.
• Treating a moving crack as a rigid repair. Rigid structural epoxy does not accommodate movement; use a joint or semi-flexible product where movement is expected.
• Skipping the technical data. Cure time, mix ratio, and application temperature are product-specific. The catalog listing tells you the category; the technical data tells you whether it fits your schedule and conditions.

Bottom Line

Choose structural repair epoxy when the repair must carry load, and choose the product form by repair geometry: gel for vertical and overhead bonding, injection resin for crack penetration, paste for crack filling, mortar for spalls. Confirm substrate condition (wet vs. dry), crack movement, and cure time against the product's technical data before ordering. If the repair is cosmetic only, a sealer or coating may be the correct and less expensive choice.