Chemical Anchors and Anchoring Adhesives: Types, Approvals and Installation

Chemical anchors are threaded rods, bars or sleeves bonded into drilled holes in concrete or masonry by a resin or cementitious adhesive, in 5 product classes from epoxy and vinylester injection adhesives to capsules, post-installed rebar systems and anchoring grouts. They carry load without expansion stress, so where do they outperform mechanical anchors, and which approval proves a product can carry a given load?

The same product goes by 6 other names: adhesive anchor in ACI documents, bonded fastener in EOTA documents, resin anchor, chemical fixing, injection mortar and anchoring adhesive. In the US, "epoxy anchor" is used as a generic term even for non-epoxy resins. Chemical anchors form one of the 15 families of construction chemicals.

An adhesive anchor in the US is qualified to ACI CODE-355.4-24 and evaluated under ICC-ES AC308 (24); in Europe it is assessed against EAD 330499-02-0601 and CE-marked through a European Technical Assessment (ETA) under AVCP system 1. Installation follows ACI 318-19: concrete at least 21 days old, and a certified installer with continuous inspection for horizontal or overhead anchors under sustained tension. Cure to full load runs from 45 minutes for a vinylester mortar at 20 °C (68 °F) to 192 hours for an epoxy at 4.4 °C (40 °F), and no VOC rule has an anchoring-adhesive category.

Standards, codes and regulations are checked against their issuing bodies, product values against the named data sheet and prices against the dated source named in the sentence; see our methodology and fact-checking.

What Is a Chemical Anchor?#

A chemical anchor is a steel element, such as a threaded rod or reinforcing bar, fixed into a drilled hole by an adhesive that transfers load to the base material along the bonded length instead of by expansion. The adhesive, steel element and tools form one tested system that carries the design value.

A chemical anchor is qualified when the system holds an evaluation report or an ETA. In the US, ICC-ES issues an evaluation report (ESR) under AC308 (24), published April 2025, after testing to ACI CODE-355.4-24. In Europe, an ETA is issued against EAD 330499-02-0601, cited by Decision (EU) 2024/1944.

What does a chemical anchor system include?#

A chemical anchor system has 5 parts, listed below.

• Adhesive and its packaging, such as side-by-side or coaxial cartridges, foil packs, glass or foil capsules and powder anchoring grouts.
• Mixing nozzle, a static mixer that blends resin and hardener as the adhesive is dispensed.
• Steel element, such as a threaded rod, a reinforcing bar or an internally threaded sleeve.
• Cleaning tools, such as blow pumps, compressed-air nozzles and wire brushes sized to the hole.
• Piston plug or screen tube: the plug lets the adhesive fill horizontal and overhead holes without voids, and the screen tube holds the adhesive in hollow masonry.

Resin can be used with anchor bolts when rod and adhesive are installed as the system named in the evaluation report: ACI 355.4 excludes horizontal or overhead injection without a piston plug.

How Do Chemical Anchors Work?#

Chemical anchors work by adhesion and micro-interlock between steel, adhesive and the wall of the drilled hole, after a resin cures by polyaddition or free-radical polymerization or a cementitious adhesive hydrates. The bond acts along the whole embedment, which is why the hole wall must be clean and the cure complete before load.

Adhesion and micro-interlock along the bonded length#

The adhesive fills the gap between rod and hole wall and transfers tension as bond stress along the embedment, with no expansion force on the concrete (ACI 355.4 R1.2). ACI 355.4 covers anchors of at least 6.35 mm (1/4 in) diameter in holes no wider than 1.5 times the anchor diameter, embedded from 4 diameters, at least 41.3 mm (1-5/8 in), to 20 diameters.

Capacity is read from the evaluation report or ETA for the rod size, embedment, concrete strength and crack state. Bond is only one of the failure modes in that report: steel failure and concrete breakout can govern before the bond fails, so a higher bond value does not always give a higher design load.

Resin cure: amine, peroxide and cement hydration#

Epoxy anchoring adhesives cure by epoxy-amine polyaddition after mixing in a static nozzle, while vinylester and polyester mortars harden by peroxide-initiated polymerization, which also runs at sub-zero base temperatures. The epoxy class is a 2-component bisphenol A/F resin with an amine hardener, mineral filled and 100 % solids. Vinylester and dimethacrylate resins, and unsaturated polyesters, are hardened with dibenzoyl peroxide (CAS 94-36-0).

Hybrid mortars add a hydraulic cement component, so cement hydration runs beside the resin cure. Capsules mix in the hole: the rod is spun and driven through the capsule, which breaks and blends resin, hardener and quartz or corundum grit. Skin sensitization comes from epoxy resins and hardeners as well as from peroxide pastes, and hardener chemistry is covered under epoxy resins and hardeners.

5 Types of Chemical Anchors and Anchoring Products#

The 5 types of chemical anchors are epoxy injection adhesives, vinylester, polyester and hybrid mortars, glass and foil capsules, adhesive systems for post-installed reinforcing bars, and cementitious anchoring grouts. They differ in cure chemistry, packaging and the document that qualifies them.

The table below compares the 5 classes by chemistry, form and qualification route.

1. Epoxy injection adhesives#

Epoxy injection adhesives are 2-component epoxy-amine products, 100 % solids, dispensed from side-by-side cartridges. They are qualified under ICC-ES AC308 (24) with ACI CODE-355.4-24 and assessed against EAD 330499-02-0601; in European repair works, EN 1504-6:2006 is the CE route for anchoring reinforcing bars. Their long working time suits deep holes, and their cure slows sharply in cold concrete.

2. Vinylester, polyester and hybrid injection mortars#

Vinylester, polyester and hybrid injection mortars are peroxide-cured vinylester, dimethacrylate or unsaturated polyester resins, and hybrids add cement. In the UK, India and Australia, "chemical anchor" refers by default to this class. Two makers' products install down to -10 °C (14 °F) base temperature, and some polyester mortars are assessed for uncracked concrete or threaded rods only.

3. Glass and foil capsule anchors#

Glass and foil capsule anchors are pre-dosed capsules of resin, hardener and grit that a spinning rod breaks and mixes in the hole. They follow the same AC308 and EAD 330499 routes as injection adhesives. Capsules are not for water-filled holes, and one capsule size fits one hole size.

4. Adhesive systems for post-installed reinforcing bars#

Adhesive systems for post-installed reinforcing bars are qualified systems that develop or splice a bar as if it were cast in. In the US they are evaluated under ICC-ES AC581 (24), published December 2025, with ACI CODE-355.5-24; in Europe under EAD 330087-01-0601 or EAD 332402-00-0601, the latter designed by EOTA TR 069 (2025). Epoxy-coated rebar is a different product and not part of this class.

5. Cementitious anchoring grouts and injection adhesives#

Cementitious anchoring products come in 2 forms: poured rapid-setting grouts that fix posts, railings and bolts in oversize holes or pockets, and 2-component cementitious injection adhesives qualified for post-installed bars. Poured grouts are not AC308 or EAD qualified. Expansive and anti-bleed admixtures for grouts are covered on concreteadditives.net.

Chemical vs Mechanical Anchors: Bond, Expansion and Time to Load#

Chemical anchors bond along the full embedment without expansion stress, while mechanical anchors (expansion, undercut and screw anchors) lock by friction or keying and carry load once set; chemical anchors carry no load until cured. That trade-off between edge freedom and waiting time decides most selections.

The verdict table below compares chemical and mechanical anchors attribute by attribute.

Load transfer, edge distance and expansion stress#

Without radial expansion pressure, an adhesive anchor allows closer edge and spacing distances than an expansion anchor, a qualitative difference the evaluation report turns into design values. An expansion anchor presses outward near its tip, which can split thin members or edges.

Both routes are qualified separately and designed under the same codes. Adhesive anchors follow ACI CODE-355.4-24 and EAD 330499-02-0601; mechanical anchors follow ACI CODE-355.2-24 and EAD 330232-02-0601, cited by Decision (EU) 2025/2355. Design of both runs under ACI 318 Chapter 17 in the US and EN 1992-4:2018 in Europe.

Time to load: cure by chemistry and base-material temperature#

Cure time is product-specific and read from the cure table of the evaluation report at the base-material temperature, so no single figure applies to chemical anchors. The table below gives cure to full load as typical product values from two makers per class; it is not a class requirement.

Capsules and cementitious products: per evaluation report. Capsule cure is not shown (one maker only).

The spread is large. At -10 °C (14 °F), the vinylester and hybrid products still cure in 20 to 24 hours, while the two epoxies list no cure value below 0 °C (32 °F) and 4.4 °C (40 °F). In wet concrete, both epoxy makers double the cure time.

Concrete age is a separate limit: ACI 318-19 26.7.2(f) requires concrete at least 21 days old when adhesive anchors are installed, unless otherwise permitted. Hole cleaning decides whether the cure table means anything, because 77 % of field installations did not follow the manufacturer's printed installation instructions (Grosser, Fuchs and Eligehausen, Concrete International, January 2011). The reference cleaning minimum is 2 blow, 2 brush, 2 blow, and AC308 treats concrete as dry when it has not been exposed to water for 14 days. These steps, with dispensing and proof loading, are set out under chemical anchor installation.

Where Are Chemical Anchors Used? Selection by Base Material and Load#

Chemical anchors are used in 4 settings: buildings, bridges and tunnels, repair works and masonry, and base material, crack state and load duration set the class and approval needed. The table below maps each setting to its classes and key rule.

Building structures and steel connections#

In buildings, adhesive anchors fix steel connections, brackets and railings to cracked or uncracked concrete, and the evaluation report states which crack state a product is qualified for. ACI CODE-355.4-24 qualifies products for uncracked concrete only, or for cracked and uncracked concrete, and sorts them into Anchor Categories 1, 2 and 3. A specification for a cracked tension zone should name a product qualified for cracked concrete.

Bridges, tunnels and overhead fixings#

Overhead and horizontal anchors under sustained tension need a creep-qualified adhesive, a certified installer and continuous inspection (ACI 318-19 26.7.1(l), 26.13.3.2(e)). Overhead work should also use piston plugs, since ACI 355.4 excludes overhead injection without one.

The rule has a history. NTSB report HAR-07/02, adopted 2007-07-10, found that the ceiling collapse in the Interstate 90 connector tunnel in Boston on 2006-07-10, which killed one person, was caused by an epoxy anchor adhesive with poor creep resistance under sustained load.

Concrete repair and strengthening#

In repair works, bars anchored into existing concrete follow EN 1504-6:2006 in Europe and the post-installed rebar route (ICC-ES AC581 (24), ACI CODE-355.5-24) in the US. EN 1504-6 is the harmonised standard for anchoring products in concrete repair, while AC581 qualifies the bar system for development and splice design.

Masonry: solid and hollow units#

Chemical anchors in hollow masonry need a screen tube that holds the adhesive in the cavity, and solid units take injection directly. Without the tube, the adhesive runs into the voids and no bonded length forms.

Masonry has its own qualification documents. In the US, ICC-ES AC58 (24), 2nd Edition, published April 2025, covers adhesive anchors in cracked and uncracked masonry. In Europe, EAD 330076-01-0604 (Decision (EU) 2023/910; variant v01 cited by Decision (EU) 2025/2623) assesses injection anchors for masonry, and EOTA TR 054 (2026) gives the design method.

Hollow units should not be hammer drilled where the installation instructions forbid it. Bond values in masonry depend on the unit, the grout fill and the masonry strength, so they are read from each product's evaluation report, not from a class figure.

Which Approvals and Standards Govern Chemical Anchors?#

Chemical anchors are governed in 3 layers: qualification documents (ICC-ES AC308, AC581, EAD 330499), design codes (ACI 318 Chapter 17, EN 1992-4:2018) and installation and site-testing rules (ACI 318-19 Chapter 26, BS 8539:2012+A1:2021).

US qualification: ICC-ES AC308, AC581 and ACI 355.4#

In the US, an adhesive anchor is qualified by testing to ACI CODE-355.4-24 and evaluated by ICC-ES under AC308 (24), published April 2025, which issues an evaluation report (ESR) with design data. AC308, titled "Post-installed Adhesive Anchors and Reinforcing Bars in Concrete Elements", incorporates ACI 355.4-11 and ACI 355.4-19. ACI CODE-355.4-24 runs to 127 pages, is written for ACI CODE-318-25 and sorts products into Anchor Categories 1, 2 and 3 for uncracked, or cracked and uncracked, concrete. It excludes open-container bulk adhesives, surface-bonded elements, fatigue and shock loads. IAPMO UES evaluation reports that use ACI 355 data are an alternative to ICC-ES reports.

Post-installed bars have their own route: ICC-ES AC581 (24), "Post-installed Reinforcing Bars in Concrete Elements", published December 2025, incorporates ACI CODE-355.5-24 (89 pages). AC308 alone no longer covers new post-installed rebar evaluations. Each document's editions and test series are listed under anchor approvals.

ACI 318 design, installation and inspection rules#

IBC 2024 and current evaluation reports reference ACI 318-19, whose Chapter 17 designs adhesive anchors and whose Chapter 26 sets 3 installation rules. Concrete is at least 21 days old at installation (26.7.2(f)). Horizontal or upwardly inclined adhesive anchors under sustained tension are installed by a certified installer (26.7.1(l)) and inspected continuously (26.13.3.2(e)).

ACI CODE-318-25 was released in February 2025, while IBC 2024 still references the 2019 edition. The ACI Adhesive Anchor Installer certification combines a written exam of 75 questions in 90 minutes with a 74 % pass mark and a performance exam in vertical-down and overhead piston-plug injection; it is valid for 5 years. Tension and shear tests of anchors in concrete follow ASTM E488/E488M-22.

European assessment: EAD 330499, ETA and EN 1992-4#

In Europe, a chemical anchor is CE-marked through a European Technical Assessment (ETA) issued against EAD 330499-02-0601, cited by Decision (EU) 2024/1944, under AVCP system 1. The document is titled "Bonded fasteners and bonded expansion fasteners for use in concrete", and its predecessor 330499-01-0601 (Decision (EU) 2020/1574) is superseded.

The variant 330499-02-0601-v01 is cited by Decision (EU) 2025/2623. The EAD assesses a working life of at least 50 years and covers seismic categories C1 and C2 and fire. Under Regulation (EU) 2024/3110, in force since 2025-01-07 and applicable since 2026-01-08, Delegated Regulation (EU) 2026/1310 (adopted 2026-06-11, published 2026-08-28, in force 2026-09-17) places chemical anchoring kits under AVS 1. ETAs already issued under Regulation (EU) 305/2011 remain the basis of current CE marks, and dates and AVCP rules are explained under EU Construction Products Regulation.

Design follows EN 1992-4:2018, which superseded EOTA TR 029; a revision, prEN 1992-4:2026, is planned for publication on 2027-05-27. EAD 330499 itself replaced the older TR 018, and EOTA TR 055 (2018) covers design for fasteners assessed under EAD 330232, 330499 and 330747.

EN 1504-6 and BS 8539 for repair works and UK site testing#

EN 1504-6:2006 is the harmonised standard for anchoring products that fix reinforcing bars in concrete repair, with a pull-out displacement limit of 0.6 mm (0.024 in) at 75 kN (16,860 lbf). The test follows EN 1881, and the standard was published on 2006-08-22.

EN 1504-6:2006 also limits creep to 0.6 mm (0.024 in) at 50 kN (11,240 lbf) over 3 months (EN 1544) and chloride content to 0.05 %, and requires a polymer glass transition temperature of at least 45 °C (113 °F) or 20 K above the service temperature. In the UK, BS 8539:2012+A1:2021, published 2021-03-31, governs selection, installation and site testing of post-installed anchors. The other repair parts of the series are compared under EN 1504.

Sustained load, creep and service temperature#

Adhesive anchors creep under permanent tension, so ACI 318 limits sustained tension to 0.55 φNba, a factor that represents 50 years at 21.1 °C (70 °F) or 10 years at 43.3 °C (110 °F). Bridge design is stricter: AASHTO LRFD 8th edition (2017), Article 5.13.2.2, uses 0.50, representing 100 years at 21.1 °C (70 °F) or 20 years at 43.3 °C (110 °F).

Service temperature sets a second limit. Each ETA declares bond per temperature range, for example 24/40 °C (75/104 °F), 50/80 °C (122/176 °F) and 72/120 °C (162/248 °F) long-term/short-term. US evaluation reports use ranges A, B and C, defined product by product, so a façade or roof fixing in sun needs the range that matches its surface temperature.

VOC Limits and Safety Rules for Chemical Anchors#

No VOC rule has an anchoring-adhesive category: South Coast AQMD Rule 1168 sets adhesive limits from 30 g/L (0.25 lb/gal) to 250 g/L (2.09 lb/gal), EPA sets none, and the EU paints directive excludes adhesives. Safety rules follow the resin, hardener and drilling dust.

VOC limits by jurisdiction#

South Coast AQMD Rule 1168 lists no anchoring-adhesive category, so the rule's general and substrate-specific adhesive limits are shown in the table below. Every category of every rule is listed under VOC limits for construction chemicals.

Rule 1168 has no anchoring-adhesive category; (d)(2)(A) assigns an unlisted adhesive the substrate-specific limit of each substrate claimed on its label, the higher one for dissimilar substrates.

The federal EPA rule for architectural coatings, 40 CFR 59 subpart D, sets no VOC content limit for adhesives. EU Directive 2004/42/EC covers paints, varnishes and vehicle refinishing products only.

Resin, hardener and drilling dust hazards#

Liquid epoxy resin carries a harmonised classification (CLP Annex VI index 603-074-00-8: H315, H317, H319, H411), and the amine hardener isophorone diamine carries H302, H314, H318 and H317 (index 612-067-00-9). BADGE (CAS 1675-54-3) carries H315, H317 and H319 under index 603-073-00-2. REACH Annex XVII has no epoxy-specific restriction, and entry 74 on diisocyanates does not apply to epoxy-amine systems. Formulated cartridges carry their own classification: see the product SDS.

Vinylester and methacrylate mortars are classified per substance: 1,4-butanediol dimethacrylate (CAS 2082-81-7) carries H317 (Annex VI index 607-766-00-0), and dibenzoyl peroxide carries H241, H317, H319, H400 and H410. Styrene (CAS 100-42-5), the reactive diluent in some polyester and vinylester grades, carries the harmonised set H226, H315, H319, H332, H361d and H372, and styrene-free grades are on the market.

Cement-based anchoring grouts carry the cement line: No Annex VI entry; ECHA C&L notified classification: H315, H317, H318, H335; see the product SDS. REACH Annex XVII entry 47 caps soluble chromium (VI) at 2 mg/kg (0.0002 %) of the total dry weight of the cement. Drilling concrete releases respirable crystalline silica: OSHA 29 CFR 1926.1153 sets a PEL of 50 µg/m³ and an action level of 25 µg/m³ (8-h TWA, effective 2016-06-23), and the EU binding limit is 0.1 mg/m³ under Directive (EU) 2017/2398.

Complete List of Chemical Anchor Product Classes: All 5 Classes#

The complete list below gives all 5 chemical anchor product classes with their chemistry, form, US and European qualification route, typical use and applicator need.

This page gives no installed price per anchor or per dowel, because no dated public range exists; a quote follows from the number, diameter and embedment of the anchors, the orientation, the inspection required and the access. Installation practice, from hole cleaning to proof loading, has its own page.

Which Chemical Anchor Is Strongest?#

No chemical anchor is strongest in general: capacity is read from the evaluation report or ETA for the rod size, embedment, concrete strength, crack state and temperature range. Steel failure or concrete breakout can govern before bond, so a stronger resin does not raise the design load once another failure mode controls. A fair comparison takes the design tension of two qualified products for the same rod, embedment, edge distance, crack state and service temperature range, read from each ESR or ETA.

How long does a chemical anchor last?#

EAD 330499 assesses bonded anchors for a working life of at least 50 years, an assessment assumption, not a guarantee. In the US, the ACI 318 sustained-tension factor of 0.55 represents 50 years at 21.1 °C (70 °F).

Is an anchoring adhesive the same as crack injection epoxy?#

No: an anchoring adhesive is a filled, thixotropic product qualified to hold steel in a hole, while crack injection resins are low-viscosity products for sealing or bonding cracks.

Low-viscosity crack resins are compared under injection resins for concrete.

Does a chemical anchor need a certified installer?#

Yes for horizontal or upwardly inclined adhesive anchors under sustained tension: ACI 318-19 26.7.1(l) requires a certified installer and 26.13.3.2(e) continuous inspection. The ACI Adhesive Anchor Installer certification is valid for 5 years.

Can chemical anchors carry load in a fire?#

Only within an assessed fire performance: EAD 330499 includes fire assessment, and EOTA TR 082 (2024) covers bonded fasteners in fire. Resin bond falls as temperature rises, so the fire value comes from the ETA, not from the ambient design value.

Is anchor grout the same as non-shrink grout?#

No: a poured anchoring grout fixes posts and bolts in oversize holes or pockets and is not AC308 or EAD qualified, while non-shrink grout fills under baseplates.

Non-shrink grades for baseplates are covered under construction grouts.

Do EU VOC rules cover anchoring adhesives?#

No: Directive 2004/42/EC covers paints, varnishes and vehicle refinishing products, not adhesives. No EU-wide VOC content limit applies to anchoring adhesives.