Structural Adhesives for Demanding Repairs

Need to rebuild an edge, fill a void or create a rigid structural bond without reaching for an ordinary cement mortar? Sika epoxy repair mortar & structural adhesive systems give contractors, concrete repair crews, maintenance teams & fabricators specialised options for bonding & repairing compatible concrete, masonry, steel & other construction materials.

The real advantage isn't simply “strong epoxy”—it's choosing a resin system that behaves correctly where the repair happens. Industrial Shed's range includes Sikadur structural epoxy products suited to applications such as vertical & overhead repairs, hole & void filling, rigid bonding, edge repairs & compatible damp concrete.

► Structural concrete bonding
► Holes & void filling
► Vertical & overhead repairs
► Corners & damaged edges
► Concrete-to-steel bonding
► Masonry & construction-material bonding
► Non-moving crack & joint-edge repairs

For deteriorated concrete requiring a broader repair system, explore Concrete Repair & Restoration.

What Are Sika Epoxy Repair Mortars & Rigid Bonding Adhesives?

Think of these products as more than glue in a larger container. Sikadur epoxy systems combine resin & hardener to create specialised structural adhesives & repair mortars capable of bonding compatible construction materials while filling, rebuilding or repairing localised areas.

Shape matters just as much as strength when you're working on a wall or soffit. Products such as Sikadur-31 CF Normal are thixotropic, helping the mixed material resist sagging during suitable vertical & overhead applications.

Rigid bonding describes another important part of the category. Instead of accommodating movement like an elastic sealant, these epoxy systems are intended for applications requiring a firm bond between compatible, correctly prepared substrates.

Why Choose Sika Epoxy Repair Products?

A repair product becomes far more useful when it can stay where you put it. Non-sag characteristics make selected Sikadur products practical for vertical surfaces, overhead areas, corners & edges where a free-flowing resin would be difficult to control.

Damp concrete can complicate product selection before work even begins. Sikadur-31 CF Normal is moisture tolerant & can be applied to dry or mat-damp concrete, while Sikadur-33 can also be used on damp concrete within its specified substrate conditions.

Mixed-material repairs often demand more than concrete-to-concrete adhesion. Depending on the selected Sikadur product, compatible substrates can include masonry, hard natural stone, ceramics, steel, aluminium, wood & other construction materials.

Shrinkage is another consideration when the epoxy is filling a defined repair geometry. Both Sikadur-31 CF Normal & Sikadur-33 are documented as hardening without shrinkage.

Common Applications

Concrete Corners & Edge Repairs

Damaged corners are small in area but demanding in geometry. A repair material needs to rebuild the missing section while remaining workable around sharp edges & vertical faces.

Sikadur structural epoxy products can be used for appropriate corner, edge & joint-arris repairs where the substrate has been correctly prepared.

Holes & Void Filling

An empty pocket in concrete or masonry needs more than a cosmetic skim across the opening. Selected Sikadur repair mortars can fill suitable holes & voids while bonding to the surrounding sound substrate.

Repair depth matters here. Check the permitted layer thickness of the selected system rather than assuming every epoxy mortar can be installed to the same depth.

Vertical & Overhead Repairs

Gravity quickly exposes the difference between a flowable resin & a thixotropic repair adhesive. Sikadur-31 CF Normal is designed for non-sag vertical & overhead work, making it relevant where the mixed epoxy needs to remain positioned during application.

Sikadur-33 has a non-sag consistency for suitable vertical & overhead repairs, making it a practical choice where the repair shape & specified application thickness match the job.

Structural Bonding

Sometimes the challenge isn't replacing missing concrete—it's joining two compatible materials securely. Sikadur structural adhesives can provide rigid bonding across selected concrete, masonry, metal & other construction substrates.

The exact product should follow the materials being joined, required layer thickness, substrate condition & application environment rather than simply choosing by pack size.

Concrete-to-Steel Bonding

Concrete beside steel creates a very different interface from concrete beside concrete. Sika lists steel among the compatible substrates for both Sikadur-31 CF Normal & Sikadur-33 when the surfaces are correctly prepared.

Rust, coatings, oil & other contamination can interfere with bonding, so preparation needs to match Sika's current application requirements.

Non-Moving Crack & Joint-Edge Repairs

Not every crack should be treated as a simple gap waiting to be filled. Sikadur products can suit certain non-moving crack sealing & joint-edge repairs, but the condition & cause of cracking should be established first.

Active movement calls for a different repair strategy. Don't substitute a rigid epoxy for a flexible joint system where movement accommodation is required.

Product Selection Guide

Start With the Repair—Not the Product Name

What exactly has failed? Answering that question first can eliminate unsuitable options before mixing ratios, pack sizes or prices enter the decision.

Identify whether the job involves:

► Structural bonding
► Hole or void filling
► Vertical patching
► Overhead repair
► Corner rebuilding
► Joint-edge repair
► Concrete-to-steel bonding
► Damp concrete
► Non-moving crack sealing

Once the function is clear, match it to the documented uses of the selected Sikadur system.

Compare Sikadur-31 CF Normal & Sikadur-33

Two structural epoxies can look similar on the shelf while behaving differently in the repair.

The takeaway is practical: don't choose between them on brand familiarity alone. Repair geometry, thickness, substrate & installation conditions should drive the decision.

Check Repair Thickness

A few extra millimetres can change which epoxy is appropriate. Sikadur-31 CF Normal has a specified layer range of 2–30 mm, while Sikadur-33 has a specified range of 0.5–10 mm.

Trying to exceed a product's application range isn't a shortcut to completing the repair faster.

For deeper or unusual repairs, confirm the current Sika Product Data Sheet & determine whether another repair mortar or staged approach is required.

Identify the Substrate

Concrete is only the beginning of the compatibility question. Depending on the selected system, Sikadur products can bond to materials including concrete, masonry, natural stone, ceramics, steel, iron, aluminium & wood.

Soundness still matters more than the material name alone.

Loose concrete, laitance, corrosion, coatings, oil, grease & contamination need to be addressed using the appropriate preparation procedure before bonding.

Check Whether the Concrete Is Dry or Damp

A darkened damp surface isn't automatically the same as standing water. Sikadur-31 CF Normal requires dry or mat-damp substrate conditions with no standing water.

Sikadur-33 is moisture tolerant & can also be used on damp concrete within its documented application requirements.

If water is actively present or the repair is submerged, don't assume a damp-compatible epoxy is automatically an underwater repair product.

Think About Orientation

Horizontal repairs get gravity's help; overhead repairs fight it.

For walls, soffits, undersides, corners & vertical faces, look specifically at thixotropic or non-sag characteristics.

Sikadur-31 CF Normal is documented as non-sag on vertical surfaces up to 15 mm thickness, while Sikadur-33 is also non-sag & suitable for overhead work.

Plan Around Pot Life

Once resin meets hardener, the clock belongs to the chemistry.

At approximately +23°C, Sikadur-31 CF Normal has a documented pot life of around 55 minutes, while Sikadur-33 is approximately 60 minutes under its stated conditions.

Warmer conditions generally shorten available handling time.

Prepare the repair area, tools, mixing equipment & access before combining components rather than using valuable pot life to organise the job.

Repair Mortar or Structural Adhesive?

The distinction isn't always as neat as the labels suggest. Some Sikadur systems perform both roles, but the way they're used changes with the repair.

For larger concrete remediation projects, Concrete Repair & Restoration provides a useful next step beyond localised epoxy repair.

Expert Tips

Don't Repair Unsound Concrete

The strongest adhesive on the shelf can't compensate for a substrate that's already breaking apart. Remove loose, weak or contaminated material until the repair is being made against appropriately sound substrate.

Dry & Mat-Damp Aren't the Same as Wet

Moisture terminology matters when you're reading technical data. Where Sika specifies dry or mat-damp concrete with no standing water, don't stretch that definition to include pooled water or submerged conditions.

Use Repair Thickness as a Selection Filter

Depth is one of the quickest ways to narrow down the right product. A 5 mm bonding layer & a 25 mm edge rebuild may sit comfortably within different parts of the range.

Measure first rather than estimating after the epoxy has been mixed.

Prepare Steel Before Bonding

A structural adhesive needs contact with the substrate—not a layer of rust, paint or oil sitting above it. Mechanically prepare steel as required & remove contaminants before applying the selected epoxy.

Mix Only What You Can Place

A large batch can feel efficient until it begins curing in the bucket. Account for ambient temperature, repair complexity & available labour before deciding how much material to mix at once.

Respect the Dew Point

Invisible condensation can undermine an otherwise carefully prepared repair. Sika requires substrate temperature to remain at least 3°C above dew point for Sikadur-31 CF Normal & Sikadur-33 applications.

Treat Overhead Work as Its Own Application

A product being called “epoxy” doesn't automatically make it suitable above your head. Confirm non-sag performance, thickness limits & preparation before beginning soffit or overhead repairs.