Injection Resins for Concrete: Epoxy, Polyurethane and Acrylic Systems

Injection resins for concrete are low-viscosity epoxy, polyurethane and acrylate liquids, plus chemical grouts and lifting foams, that are pumped into cracks, joints, voids and soil to re-bond concrete, stop water, stabilize ground or lift slabs. Which of the 6 product classes fits depends on one question: does the crack need strength back, or does it need to stop water?

The 6 classes fall into 3 groups: crack injection resins (epoxy and polyurethane), gels and grouts for joints and soil (acrylate gels and chemical grouts), and lifting foam with the packers and ports that every injection job uses. Contractors in the UK and India call the work "injection grouting", UK specifiers also say "resin injection", and German specifications use "Rissinjektion". Injection is one of the 15 families of construction chemicals.

Epoxy is the only class that restores strength: ASTM C881/C881M-20a Type IV, Grade 1 resin re-bonds dormant cracks from 0.05 mm (0.002 in) wide, and ICRI 210.1R-2016 accepts the work when cores show at least 90 % of the crack filled. In Europe the products carry EN 1504-5 categories F, D or S. A 0.3 mm (0.012 in) crack 200 mm (7.9 in) deep holds 0.06 L (0.016 US gal) of resin per meter, theoretical. Installed epoxy crack injection runs USD 250 to 1,000 per crack in the US (Fixr, 2026-02-06).

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 an Injection Resin?#

An injection resin is a reactive liquid of very low viscosity that is pressure- or gravity-fed into a crack, joint or void and cures there to bond the faces, seal out water or fill the space.

Crack injection is the process: ports or packers are set along the crack, the surface is sealed, and resin is pumped in until it appears at the next port. ACI PRC-224.1-07 (formerly ACI 224.1R-07) treats cracks as narrow as 0.05 mm (0.002 in) as injectable with epoxy, so hairline cracks that are barely visible can still be filled and re-bonded.

Injection resin, chemical grout and injection grouting: how the terms differ#

Injection resin names the crack product, chemical grout names a permeation product for soil and water cut-off, and injection grouting is the trade term for the work in the UK and India. EN 1504-5 separates injection products by binder as well: P for reactive polymers such as epoxy, polyurethane and acrylate, and H for hydraulic binders such as microfine cement.

Injection machines and pumps are equipment rather than chemistry, and geotechnical jet grouting, compaction grouting and grout anchors belong to ground engineering, so none of them is covered here.

How Do Injection Resins Work in Cracks, Joints and Soil?#

Injection products work in 3 ways: epoxy re-bonds crack faces and transmits force, polyurethane and acrylate resins seal water as ductile foams or swelling gels, and grouts and lifting foams fill soil and voids. These are the force-transmitting (F), ductile (D) and swelling (S) categories of EN 1504-5, plus soil permeation and void filling, which lie outside that standard.

Force-transmitting injection: re-bonding a dormant crack#

Epoxy injection restores monolithic action because the 100 % solids resin cures by amine-epoxy addition and bonds both crack faces. The cured resin carries load across the former crack, so a cracked beam, wall or slab acts again as one member, and its binders and hardeners are explained under epoxy resins and hardeners.

Monolithic action has a price: cured epoxy has no movement capacity. A crack that is still opening and closing re-cracks beside the repair, because the bonded line is now stiffer than the concrete next to it, and an epoxy grade that is not moisture-tolerant bonds poorly to wet crack faces.

Ductile and swelling injection: sealing water in wet or moving cracks#

Polyurethane prepolymers react with the water in the crack and foam or gel, while acrylate solutions polymerize to an elastic hydrogel that swells with water. The isocyanate-water reaction releases carbon dioxide, which drives the foaming.

Hydrophilic polyurethane absorbs water and bonds in wet cracks but shrinks when it dries out. Hydrophobic polyurethane is catalyzed, expands strongly and keeps its volume. Acrylate gel swells reversibly in water and shrinks when dry. None of the 3 restores structural strength, and their isocyanate chemistry is covered under polyurethane resins and prepolymers.

Permeation and void filling in soil and below slabs#

Chemical grouts fill the pores of soil and bind its grains, which raises strength and stiffness and cuts permeability, while lifting foam fills the void under a slab and raises it. Permeation works only where the soil pores are open enough: sodium silicate gels without expansion and does not permeate clays or silts.

Lifting foam is a 2-component closed-cell polyurethane with a density of 32 to 64 kg/m³ (2 to 4 lb/ft³), against about 1,600 kg/m³ (100 lb/ft³) for the cement slurry used in mudjacking. No standard sets a load rating for lifting foam; the soil below governs the capacity of the lifted slab.

6 Types of Injection Products in 3 Groups#

The 6 types of injection products fall into 3 groups: 2 crack injection resins, 2 gel and grout classes for joints and soil, and lifting foam with the packers and ports that every injection job uses. The group table below compares the classes, mechanism and EN 1504-5 role of each group.

1. Crack injection resins (2)#

Crack injection resins are reactive liquids pumped into cracks in concrete and masonry to restore strength or stop a leak; this group has 2 classes: epoxy and polyurethane. The crack condition decides between them.

Epoxy crack injection resins#

Epoxy crack injection resin is a 2-component, 100 % solids epoxy that re-bonds dormant dry or damp cracks. In Europe it carries EN 1504-5:2004 category F; in the US it is specified as ASTM C881/C881M-20a Type IV, Grade 1. Epoxy injection is used to restore load transfer across cracks in walls, slabs, beams and columns.

Hydrophilic and hydrophobic polyurethane resins#

Polyurethane injection resin is a 1-component water-reactive or 2-component elastic prepolymer that seals leaking, wet and moving cracks. The 2-component elastic resins carry EN 1504-5 category D; no ASTM product specification exists for polyurethane injection grouts. ACI PRC-224.1-07 treats polyurethane injection as leak sealing only.

2. Gels and grouts for joints and soil (2)#

Gels and grouts are water-thin solutions or fine suspensions that seal joints and permeate the ground behind or below a structure; this group has 2 classes: acrylate injection gels and chemical grouts.

Acrylate injection gels#

Acrylate injection gel is a 3-component, water-thin monomer solution that polymerizes after an adjustable gel time into a reversible swelling hydrogel. It carries EN 1504-5 category S. Acrylate gels seal construction joints, form curtain injections through a wall into the soil behind it and seal soil around leaking structures.

Silicate, acrylate and microfine cement grouts#

Chemical grout is a sodium silicate, acrylate, polyurethane or microfine cement grout that permeates soil, sewer joints and manholes. Execution follows EN 12715:2020, and US sewer work follows ASTM F2304-22 and F2414-04(2023). Microfine cement is the H binder of EN 1504-5:2013.

3. Lifting foam and injection hardware (2)#

Lifting foam and injection hardware are the products that lift slabs and get resin into the structure; this group has 2 classes: high-density polyurethane lifting foam and packers, ports and capsules.

High-density polyurethane lifting foam#

Lifting foam is a 2-component closed-cell polyurethane foam of 32 to 64 kg/m³ (2 to 4 lb/ft³) injected below a settled slab to fill the void and raise it. Foam samples are tested to ASTM D1621-16(2023), a test method for compressive properties. No standard gives the foam a load rating.

Packers, ports and capsules#

Packers, ports and capsules are the entry points for every injection resin: drilled mechanical packers, hammer-in packers, bonded surface ports and spring or balloon capsules. No product standard covers them. ACI PRC-224.1-07 describes drilled epoxy ports of about 20 mm (3/4 in), and ACI RAP-1 spaces surface ports about 203 mm (8 in) apart.

How to Choose an Injection Resin by Crack Condition#

The crack condition chooses the resin: a dormant structural crack takes epoxy, an active leak takes polyurethane, a moving dry crack is routed and sealed, and a corrosion crack goes to concrete repair. Crack width is read with a crack comparator, which ACI PRC-224.1-07 credits with an accuracy of about 0.025 mm (0.001 in).

A specification should name the crack condition first and the resin second, because the same crack width can call for either resin. Both resins are set side by side, with cure, moisture and cost, under epoxy vs polyurethane crack injection.

Dormant structural cracks#

Epoxy fixes a dormant crack structurally when the crack is dry or damp, at least 0.05 mm (0.002 in) wide and no longer moving. ACI PRC-224.1-07 names ASTM C881 Type IV, the load-bearing type for bonding hardened to hardened concrete, for structural crack injection.

Can epoxy fix every crack? It cannot fix a wet one with every grade: an epoxy that is not moisture-tolerant bonds poorly to wet or silty crack faces, so a crack with standing water should be dried, or treated as a leak and sealed with polyurethane first.

Active leaks and wet cracks#

An active leak takes a water-reactive polyurethane, because water in the crack is what makes the resin foam and bond. Hydrophilic grades bond in wet cracks and stop running water; hydrophobic grades expand strongly and keep their volume.

The hydrophilic grade has one weakness: it shrinks when the crack dries out, so a leak can return after a dry season. A crack with high water flow should be plugged before injection, so the resin is not washed out, and fast-setting plugs are compared under hydraulic cement.

Moving cracks, corrosion cracks and wide crack networks#

Three crack conditions are not injected with epoxy: moving cracks without water, cracks from corroding reinforcement and networks of fine deck cracks. Each has its own method in ACI PRC-224.1-07 and ACI RAP-1.

A moving crack without water should be routed and sealed: ACI PRC-224.1-07 describes a groove 6 to 25 mm (1/4 to 1 in) deep, and an active crack needs a width-to-depth ratio of at least 2 with a bond breaker. A network of fine deck cracks should be gravity-filled with low-viscosity resins, for cracks of 0.03 to 2 mm (0.001 to 0.08 in).

Where the cause of the movement stays, the crack should be routed and sealed as a joint, a new joint should be created and the crack injected, or support should be added. A crack caused by corroding reinforcement should not be epoxy-injected under ACI RAP-1, and section loss and rebar corrosion are covered under concrete repair products.

Where Is Crack Injection Used? Selection by Structure#

Crack injection is used in 5 structure types (basements and foundations, tunnels, tanks and water-retaining structures, floor slabs and masonry walls), and the water load and movement at each decide the resin. The table below matches each structure with its water and movement, the injection classes that suit it and the rule that governs the choice.

Basement walls and foundations#

Basement walls take epoxy where a dormant crack needs strength and polyurethane where the crack leaks. A wall crack injected with polyurethane is sealed, not structurally repaired.

Installed epoxy crack injection costs USD 250 to 1,000 per crack in the US (Fixr, 2026-02-06). Crack widths, causes and repair choices for basement walls are set out under foundation crack repair.

Tunnels, tanks and water-retaining structures#

Tunnels, tanks and reservoirs take polyurethane and acrylate injection for leaks at cracks, joints and segment gaps, many of them under water pressure. EN 1504-5:2013 tests ductile resins for watertightness at 2 × 10⁵ Pa (2 bar, 29 psi) and swelling gels at the same pressure over 500 cycles. Resin in contact with drinking water needs a potable-contact approval for the specific product.

Floor slabs and settled slabs#

Floor slabs take epoxy or gravity-fed resins in cracks and lifting foam where the slab itself has settled. Gravity feeding suits fine slab cracks of 0.03 to 2 mm (0.001 to 0.08 in), while a slab that has dropped needs the void below it filled.

Polyjacking with lifting foam costs USD 86.11 to 269.10 per m² (USD 8 to 25 per ft²) installed, residential, with a job minimum of USD 300 to 700, in the US (slabcalc.co, updated 2026-09-29). Slab cracks by cause are covered under concrete floor and slab crack repair.

Masonry walls#

Masonry walls take crack injection like concrete, while injection against rising damp is a separate damp-proof course treatment. Cracks in brick or block walls accept epoxy for re-bonding and polyurethane for leaks.

Which Standards Govern Injection Resins? EN 1504-5 and ASTM C881#

Injection resins are governed by EN 1504-5 in Europe and by ASTM C881 with the ACI and ICRI injection guides in the US, while chemical grouting follows EN 12715:2020 and the ASTM sewer practices. Product standards set what the resin must achieve; execution standards and guides set how the work is done and accepted.

EN 1504-5: the 2004 CE-marking edition and the 2013 CEN edition#

CE marking of injection products still runs on EN 1504-5:2004, while EN 1504-5:2013 is the current CEN edition with numeric F, D and S thresholds but no harmonized status. The 2004 edition is cited in the Official Journal of the EU under the Construction Products Regulation 305/2011, with assessment under AVCP System 2+ or 4.

Declarations of performance under the 2004 edition state the F bond as "cohesive failure in the substrate". The new Construction Products Regulation (EU) 2024/3110 entered into force on 2025-01-07 and applies from 2026-01-08, and standards cited under 305/2011 keep applying until the family moves. All ten parts are explained under EN 1504.

EN 1504-5:2013, approved on 2013-01-20, sets these thresholds:

• F1: tensile bond at least 3.0 N/mm² (435 psi), lowest reading 2.5 N/mm²; F2 at least 2.0 N/mm² (290 psi), lowest reading 1.5 N/mm²; F3 declared, for voids only.
• D: elongation above 10 %, watertight at 2 × 10⁵ Pa (29 psi), crack filled above 90 % at 0.5 and 0.8 mm.
• S: viscosity at most 60 mPa·s, crack filled above 95 %, watertight at 2 × 10⁵ Pa (29 psi) with 500 pressure cycles.
• Splitting strength above 7 N/mm² (1,015 psi) for P binders and above 3 N/mm² (435 psi) for H binders; pot life is the time to reach 1,000 mPa·s.

ASTM C881 Type IV and the ACI and ICRI injection guides#

In the US, structural injection epoxy is specified as ASTM C881/C881M-20a Type IV, Grade 1, with the class chosen by the temperature of the concrete surface. Type IV is the load-bearing type for bonding hardened to hardened concrete, Grade 1 is the low-viscosity grade at most 2,000 cP (2,000 mPa·s), Grade 2 runs 2,000 to 10,000 cP and Grade 3 is non-sag.

ACI PRC-224.1-07 names Type IV for structural crack injection, ACI RAP-1 (2003, reapproved 2009) is the field guide for the work, and ICRI 210.1R-2016 sets field quality assurance. Types, grades and classes are tabulated under ASTM C881.

Grouting execution and sewer standards#

Soil and sewer grouting follow execution standards, not product standards: EN 12715:2020 in Europe and ASTM F2304-22 and F2414-04(2023) for sewer joints and manholes. EN 12715:2020, published 2020-11-17 by CEN/TC 288, covers permeation, fissure, bulk filling, compaction and compensation grouting, excludes jet grouting and has been under systematic review since 2026-06-26. ASTM F2304-22 covers sewer pipe joints of 150 to 1,070 mm (6 to 42 in) sealed by the packer method and is not a structural repair; F2414-04(2023) covers manholes. ICRI 710.5-2024 is the "Guide for the Selection of Grouts to Control Water Leakage Through Cracks in Concrete Structures". DIN V 18028:2006-06 is a withdrawn German pre-standard and not a current requirement.

Field quality control: cores, ratio and pressure tests#

Epoxy injection is accepted on cores: ICRI 210.1R-2016 treats a core with at least 90 % of the crack filled as adequate penetration, and ACI RAP-1 takes cores of 50 mm (2 in). ICRI 210.1R-2016 replaced ICRI 03734 of 1998 and does not require a 100 % fill.

The checks named in ICRI 210.1R-2016 are listed below.

• Visual inspection of the sealed and injected crack.
• Laboratory tests on the resin.
• Field tests each shift: mix ratio, pump pressure and gel time.
• Cores and nondestructive tests: impact echo, ultrasonic pulse velocity (UPV) and spectral analysis of surface waves (SASW).

For hairline cracks, ACI RAP-1 describes an injection pressure of about 1.38 MPa (200 psi) held for 5 minutes.

How Much Resin Does a Crack Take? Crack Volume, Viscosity and Temperature#

A crack takes its own volume in resin plus waste: a 0.3 mm (0.012 in) crack 200 mm (7.9 in) deep holds 0.06 L (0.016 US gal) per meter of length, theoretical. Viscosity and temperature decide whether the resin reaches that full depth.

Crack volume and resin consumption#

Resin consumption equals crack volume, width times depth times length, plus the resin left in ports, hoses and mixers. The volume is theoretical, because real cracks vary in width along their length and depth.

Worked example, theoretical:

• Crack width: 0.3 mm (0.012 in).
• Crack depth: 200 mm (7.9 in), the full thickness of a 200 mm wall.
• Crack length: 1,000 mm (1 m).
• Volume: 0.3 × 200 × 1,000 = 60,000 mm³ = 0.06 L (0.016 US gal) per meter of crack, with 1 US gal = 3.79 L (231 in³).

Foam and gel consumption follows other rules: polyurethane expands with water and acrylate gel also fills joints and soil, so their consumption depends on expansion and on the water in the structure, and no volume formula applies.

Viscosity grades and cure temperature classes#

Viscosity decides which crack a resin enters, and thinner resin travels further into fine cracks before it gels. ASTM C881 Grade 1 is at most 2,000 cP (2,000 mPa·s), ACI RAP-1 asks for at most 500 cP for cracks up to 0.25 mm (0.010 in), and EN 1504-5:2013 swelling gels are at most 60 mPa·s.

ASTM C881/C881M-20a sets cure classes by the temperature of the hardened concrete surface: Class A below 4 °C (40 °F), Class B from 4 to 15 °C (40 to 60 °F) and Class C above 15 °C (60 °F). EN 1504-5:2013 grades injectability for P binders by time: class 1 below 4 minutes at 0.1 mm, class 2 below 8 minutes at 0.2 mm and class 3 below 12 minutes at 0.3 mm.

VOC Limits and Safety Rules for Injection Resins#

Injection resins have no VOC category of their own, so South Coast AQMD Rule 1168 limits them by how they are sold: 50 g/L (0.42 lb/gal) as a sealant or 250 g/L (2.09 lb/gal) as an adhesive. Safety rules add the EU diisocyanate training duty for polyurethane resins and foams.

VOC limits by product labeling#

South Coast AQMD Rule 1168 assigns an injection resin by how the product is sold and labeled, and the manufacturer makes that call. The table below gives the 3 categories an injection resin can fall into, and every category is listed under VOC limits for construction chemicals.

Rule 1168 has no injection-resin category; the manufacturer assigns the category by labeling. Outside the South Coast air district, the federal EPA architectural coatings rule (40 CFR 59 subpart D) sets no VOC content limit for adhesives or sealants.

Diisocyanate, epoxy, acrylamide and cement rules for applicators#

Polyurethane injection resins and lifting foams with at least 0.1 % diisocyanates by weight need a label statement since 2022-02-24 and documented training before professional use since 2023-08-24 (REACH Annex XVII entry 74). The training is renewed at least every 5 years under Regulation (EU) 2020/1149. Directive (EU) 2024/869 sets an EU limit of 6 µg NCO/m³ (8-h) and 12 µg NCO/m³ short-term, with 10 and 20 µg NCO/m³ until 2028-12-31; in the US, the OSHA PEL for MDI is a ceiling of 0.02 ppm (0.2 mg/m³) and the NIOSH REL is 0.005 ppm TWA.

Polyurethane resins and prepolymers have no Annex VI entry as a class; see the product SDS. Their monomer 4,4'-MDI is harmonized under CLP Annex VI index 615-005-00-9 with H315, H317, H319, H332, H334, H335, H351 and H373. Liquid epoxy resin (CAS 25068-38-6) is harmonized under index 603-074-00-8 with H315, H317, H319 and H411; for amine hardeners, see the product SDS.

Acrylamide (CAS 79-06-1) carries the harmonized CLP Annex VI codes H301, H312, H315, H317, H319, H332, H340, H350, H361f and H372 and has been on the REACH Candidate List since 2010-03-30; for acrylate gels, see the product SDS. Microfine cement grouts carry the cement line "No Annex VI entry; ECHA C&L notified classification: H315, H317, H318, H335; see the product SDS", and REACH entry 47 limits soluble Cr(VI) to 2 mg/kg (0.0002 %). EU exposure limits and US rules are compared under diisocyanates rules.

Complete List of Injection Resins and Grouts: All 6 Classes#

The complete list below gives all 6 injection product classes with their chemistry, European and US standards, use, structural role, applicator need and a dated installed cost where one is published.

CE marking uses EN 1504-5:2004; the 2013 edition is CEN current and not harmonized. "Not published" means no dated public range exists, and the price then follows from crack length, access, water flow and the number of ports.

Chemical grouting has no dated public cost, because soil, depth and water flow set the price of each job. Injection machines and pumps are equipment and are not listed as a product class.

Which Injection Resin Is Best for a Crack?#

No injection resin is best for every crack: epoxy answers strength in a dormant crack, polyurethane answers water in an active one, and a specification names the resin by EN 1504-5 category or ASTM C881 type, not by brand. Integral crystalline admixtures that reduce the permeability of new concrete are covered on concreteadditives.net.

How much does crack injection cost?#

Installed epoxy crack injection costs USD 250 to 1,000 per crack in the US (Fixr, 2026-02-06). Polyjacking costs USD 86.11 to 269.10 per m² (USD 8 to 25 per ft²) installed, with a job minimum of USD 300 to 700 (slabcalc.co, 2026-09-29). Both lifting methods are priced under mudjacking vs polyjacking.

How long does crack injection last?#

Crack injection lasts as long as the crack condition it was chosen for: epoxy fails when a crack keeps moving, and hydrophilic polyurethane lets the leak return when it dries and shrinks. No standard or guide cited on this page gives a fixed number of years.

Can polyurethane injection restore structural strength?#

No: ACI PRC-224.1-07 treats polyurethane and acrylate injection as leak sealing, not structural repair. A crack that needs its strength back takes epoxy to ASTM C881 Type IV, Grade 1, once the leak is stopped.

Is acrylamide grout still allowed?#

Not in the EU: REACH Annex XVII entry 60 bars acrylamide at 0.1 % by weight or more in grouting after 2012-11-05. The restriction comes from Regulation (EU) No 366/2011 and covers acrylamide only, not acrylate gels.

Does crack injection need a specialist applicator?#

Yes: ACI guidance states that epoxy injection needs a high degree of skill, and EU users of diisocyanate resins need documented training. All 6 classes on this page are applicator-installed, from the packers and pumps to the core samples that prove the fill.

Is resin injection the same as a chemical damp-proof course?#

No: injecting a damp-proof course into masonry against rising damp is a separate treatment from crack injection in concrete. Crack resins fill and bond a crack; a damp-proof course treats capillary moisture in the wall.