Concrete Crack Repair: Crack Types, Causes and Repair Methods

Concrete crack repair restores the structure, the watertightness or the appearance of cracked concrete by injection, gravity filling, routing and sealing, or concrete replacement, and the right method follows from what the crack does, not from how it looks. A dormant, dry crack in a beam and a wet, moving crack in a basement wall need opposite materials, so which one is yours? Cement crack repair, the term many owners search for, covers the same 5 methods, and ACI PRC-224.1-07 treats cracks from 0.05 mm (0.002 in) wide as injectable.

Each crack is matched to a product class by 3 questions: does it still move, is it wet, and does the member depend on it being bonded? Epoxy re-bonds dormant cracks, polyurethane and acrylate resins seal leaks, elastomeric sealants take movement, and repair mortars replace concrete broken by corroding steel. Crack repair is one of the problem areas covered across construction chemicals.

This page sets out why cracks form, how to classify them, the widths and code limits that decide the method, the 14 product classes in job order, repair by structure, acceptance by cores with at least 90 % of the crack filled (ICRI 210.1R-2016), safety and VOC rules, and dated costs such as USD 250 to 1,000 per crack for installed epoxy injection 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 Concrete Crack Repair?#

Concrete crack repair is the selection and placement of a material that bonds a dormant crack back together, seals a wet or moving crack against water, or removes the cause and the damaged concrete around it. The three jobs use different chemistry. Bonding needs a rigid resin that carries load across the crack, such as epoxy; sealing needs a material that reacts with water or stretches, such as polyurethane or acrylate gel; removal needs a repair mortar or added reinforcement. Where the cause of a crack cannot be removed, ACI PRC-224.1-07 gives three routes: rout and seal the crack as a joint, create a joint and inject the crack, or add support or reinforcement.

Why Concrete Cracks Form and Why the Cause Sets the Repair#

Cracks form when tensile stress from drying, temperature change, settlement, load or corroding steel exceeds what the concrete can carry, and each cause leaves a different crack behind. The cause matters more than the width, because a filler placed over a live cause cracks again beside the repair or hides damage that keeps growing. Settlement and thermal cracks, with their patterns and causes, are covered on the page for each crack type.

Two causes set the repair on their own. Plastic shrinkage cracks start in fresh concrete when evaporation outruns bleeding: the ACI nomograph, as cited by FHWA, calls for action above 1.0 kg/m²/h (0.2 lb/ft²/h) and for caution from 0.5 kg/m²/h (0.1 lb/ft²/h). Cracks caused by corroding reinforcement are never epoxy-injected under ACI RAP-1 (2003, reapproved 2009); they go to concrete repair, because the rust keeps expanding behind the resin. Admixtures and fibers that reduce shrinkage cracking are covered on concreteadditives.net. Site conditions before a pour can be checked with the concrete evaporation rate calculator.

Classify the Crack First: Moving or Dormant, Wet or Dry, Structural or Not#

Every crack is classified on three questions before a product is chosen: does it still move, is it wet, and does the member depend on it being bonded? The three questions and the answers that change the product are listed below.

• Moving or dormant: a dormant crack takes a rigid epoxy; a crack that still opens and closes takes an elastomeric sealant or a ductile resin, because epoxy accommodates no later movement and an active crack re-cracks beside the repair.
• Wet or dry: a dry or damp crack accepts epoxy; a wet or leaking crack takes polyurethane or acrylate injection, which reacts with or swells in water.
• Structural or not: a crack in a beam, column or wall that carries load is re-bonded with epoxy; where the crack does not compromise structural integrity, ACI RAP-1 notes that polyurethane grouts or other nonstructural materials may be more suitable.

Crack width is read with a crack comparator, a card of printed lines that ACI PRC-224.1-07 credits with an accuracy of about 0.025 mm (0.001 in). How do you know whether a crack still moves? Width readings at the same marked points over time answer it: a width that changes with temperature or load marks an active crack, and a constant width over the monitoring period marks a dormant one. Movement is measured before the product is chosen, because the choice between a rigid and an elastic material cannot be reversed once the crack is filled.

Crack Widths and Code Thresholds That Decide the Repair#

Crack repair runs on published widths: injection reaches cracks from 0.05 mm (0.002 in), gravity filling covers 0.03 to 2 mm (0.001 to 0.08 in), and design codes cap crack width by exposure. Code limits such as the AASHTO values are design criteria for new structures, not repair triggers: a crack wider than the limit calls for an evaluation, and the repair still follows the crack condition. Table N1 lists the thresholds, what each one governs and the document and edition it comes from.

EN 1504-5 and ASTM C881: The Product Standards for Injection Resins#

Injection resins are specified to EN 1504-5 in Europe and, for epoxies, to ASTM C881/C881M-20a in the US, and the two describe different properties. EN 1504-5:2004 is the CE-marking edition, cited in the Official Journal under the Construction Products Regulation 305/2011 with assessment under AVCP System 2+ or 4, while EN 1504-5:2013 is the current CEN edition without harmonized status. EN 1504-5 sorts injection products into 3 categories: F (force-transmitting), D (ductile) and S (swelling), each with a reactive polymer (P) or hydraulic (H) binder. EN 1504-5:2013 sets F1 at a tensile bond of at least 3.0 N/mm² (435 psi) and F2 at least 2.0 N/mm² (290 psi); category D needs elongation over 10 % and watertightness at 2 × 10⁵ Pa (2 bar, 29 psi); category S needs a viscosity of at most 60 mPa·s and a crack filled over 95 %.

ASTM C881/C881M-20a classifies epoxy systems by type, grade and class rather than by job. ACI PRC-224.1-07 names Type IV, the load-bearing type for bonding hardened to hardened concrete, Grade 1, for structural crack injection, and Grade 1 means a viscosity of at most 2,000 cP (2,000 mPa·s) against 2,000 to 10,000 cP for Grade 2. Classes follow the hardened concrete surface temperature: A below 4 °C (40 °F), B from 4 to 15 °C (40 to 60 °F) and C above 15 °C (60 °F). Injection resins are one product family inside a ten-part European series, and every part and its status are listed under EN 1504.

The harmonized EN 1504 parts are EN 1504-2:2004, -3:2005, -4:2004, -5:2004, -6:2006 and -7:2006. 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 stay valid until a product family moves under the new regulation.

Which Repair Methods and Products Fit Which Crack?#

Five methods match five crack conditions: epoxy injection for dormant structural cracks, polyurethane or acrylate injection for leaks, gravity filling for fine dormant cracks, routing and sealing for moving cracks, and concrete repair for corrosion or overload cracks. A specification should name the crack condition first and the product class second, because one crack width can call for opposite materials. Table S1 lists the 14 product classes in job order, from stopping running water to strengthening, and ends with the products that are not the answer.

Epoxy Injection to Restore Dormant Structural Cracks#

Epoxy injection bonds the faces of a dormant crack back together so the member acts as one piece again, and it works only when the crack has stopped moving. The cured resin carries load across the former crack, which is why ACI PRC-224.1-07 names ASTM C881 Type IV for structural injection. A crack that still opens and closes re-cracks beside the bonded line, because the repair is now stiffer than the concrete next to it.

Fine cracks need a thin resin: ACI RAP-1 calls for a viscosity of at most 500 cP (500 mPa·s) for cracks up to 0.3 mm (0.010 in). The crack face is cap-sealed, surface ports are set about 203 mm (8 in) apart, and resin is pumped in until it appears at the next port. Cracks caused by corroding steel are excluded, since epoxy seals the rust in without stopping it. Port types, capsules and the chemistry of each resin class, with epoxy, polyurethane and acrylate systems compared, are set out under injection resins for concrete.

Polyurethane and Acrylate Injection to Stop Leaking Cracks#

Polyurethane and acrylate injection seals cracks that carry water, but neither restores structural capacity. ACI PRC-224.1-07 treats chemical grouts as leak sealing, with low bond strength to the crack faces. Both resins reach cracks from 0.05 mm (0.002 in), the same minimum as epoxy.

Polyurethane comes in 2 forms. Hydrophilic resin absorbs water and bonds in wet cracks but shrinks when it dries out, so a leak can return after a dry season; hydrophobic resin is catalyzed, expands strongly and keeps its volume. Acrylate gels swell reversibly with water, which earns them EN 1504-5 category S, and shrink when dry. Acrylamide grout is a separate case in the EU: REACH Annex XVII entry 60 (Regulation (EU) No 366/2011) bans grouting products with 0.1 % by weight or more acrylamide after 2012-11-05.

ICRI 710.5-2024, the Guide for the Selection of Grouts to Control Water Leakage Through Cracks in Concrete Structures, is the selection guide for leak-sealing grouts. A dormant crack that leaks raises the hardest question, strength or watertightness first, and the decision between the two is set out under epoxy vs polyurethane crack injection.

Gravity Filling of Fine Cracks in Slabs and Decks#

Gravity filling pours a very low-viscosity resin over a horizontal surface so that it runs into cracks between 0.03 and 2 mm (0.001 and 0.08 in) wide. The method suits slabs and bridge or parking decks with networks of fine cracks, where setting ports along every crack would cost more than the repair.

Three resin groups are used: high-molecular-weight methacrylate (HMWM), urethanes and low-viscosity epoxies, with ASTM C881/C881M-20a Types I and II Grade 1 for epoxy fillers. A gravity-fed resin bonds the crack faces at the surface but carries no claim to restore a structural member. A rigid filler in a moving crack re-cracks, so gravity filling is reserved for dormant cracks.

Routing and Sealing Cracks That Keep Moving#

A crack that still opens and closes is treated as a joint: it is routed to a groove 6 to 25 mm (1/4 to 1 in) deep and sealed with an elastomeric sealant. ACI PRC-224.1-07 sets a width-to-depth ratio of at least 2 for active cracks, with a bond breaker at the bottom so the sealant bonds to the two sides only. ASTM C920-18(2024) rates elastomeric sealants in movement classes 100/50, 50, 35, 25 and 12.5, and ASTM C1193-25 is the guide for joint design and field adhesion. Movement classes and joint types are compared under construction sealants.

Two older methods remain in the guide for special cases. Overbanding seals the surface with a band 25 to 75 mm (1 to 3 in) wide on each side of the crack and a coating 1 to 2 mm (0.04 to 0.08 in) thick. Drypacking rams a stiff mortar into a slot about 25 × 25 mm (1 × 1 in), for dormant cracks only.

Cracks From Rebar Corrosion, Overload or Settlement#

When the cause of a crack is still active, the repair removes or carries the cause first, because filling the crack alone leaves the stress or the corrosion in place. ACI PRC-224.1-07 gives three options when the cause cannot be removed: rout and seal the crack as a joint, create a joint and inject the crack, or add support or reinforcement.

Each cause has its own route. Corrosion cracks are broken out and patched with an EN 1504-3:2005 structural mortar: R4 needs compressive strength of at least 45 MPa (6,527 psi) and bond of at least 2.0 MPa (290 psi), R3 at least 25 MPa (3,626 psi) and 1.5 MPa (218 psi). Overload cracks need added capacity, for example FRP designed to ACI PRC-440.2-23. A settled slab is re-supported before its cracks are sealed. Mortars, anodes and inhibitors are compared under concrete repair products.

Epoxy Concrete Crack Repair: What Two-Part Epoxy Can and Cannot Do#

Two-part epoxy is the right crack repair only for a dormant crack that is dry or damp; it bonds the faces but takes no later movement and stops no running water. An epoxy that is not moisture-tolerant bonds poorly to wet crack faces, so a leaking crack is sealed first or treated with polyurethane.

What should a label or data sheet show before an epoxy goes into a crack? The four items below identify a structural injection epoxy without relying on a brand name.

• ASTM C881 type: Type IV for load-bearing structural injection (ASTM C881/C881M-20a).
• ASTM C881 grade: Grade 1, at most 2,000 cP (2,000 mPa·s), for injection.
• ASTM C881 class: A, B or C to match the concrete surface temperature on the day of work.
• EN 1504-5 category: F on the declaration of performance for a CE-marked product.

Concrete Crack Repair by Structure: Foundations, Floors, Decks and Tanks#

The same crack calls for a different repair route in a basement wall, a slab on ground, a parking deck or a water tank, because water, traffic and access change at each one. Table A1 matches 7 structures and topics with their crack condition, the first repair route and the key document.

Tanks and reservoirs are designed to EN 1992-3:2006 tightness classes. In class 1, through-cracks are limited to wk1 = 0.2 mm (0.008 in) where the ratio of water head to wall thickness (hD/h) is up to 5, falling to 0.05 mm (0.002 in) at 35 and above, with linear interpolation between them; these are recommended values and a national annex may differ. Liners and coatings lie outside the scope of EN 1992-3, so a flexible lining over an injected crack is chosen on its own standard, and a rigid slurry is never placed over a moving crack.

How Is a Crack Repair Tested and Accepted?#

An epoxy crack injection is accepted on evidence: cores showing at least 90 % of the crack filled (ICRI 210.1R-2016), backed by records of mix ratio, pressure and gel time from each shift. ICRI 210.1R-2016 replaced ICRI 03734 (1998) and groups quality assurance into visual checks, laboratory tests, field tests of ratio, pressure and gel time, cores and nondestructive testing.

Cores under ACI RAP-1 are 50 mm (2 in) in diameter and are cut across the crack where the engineer selects. Each core shows how deep the resin reached, and cores can also be tested in splitting tension to ASTM C496 or for strength to ASTM C42. Nondestructive methods cover the length between cores: ultrasonic pulse velocity (UPV), impact echo and spectral analysis of surface waves (SASW) find unfilled zones without cutting the structure.

Leak-sealing injection has a different test. ICRI 210.1R-2016 is written for epoxy injection, so a polyurethane or acrylate seal is judged by whether the crack stays dry under water load, and the specification states when and how the wall is inspected. The EN 1504-5:2013 filling test, over 90 % filled at 0.5 and 0.8 mm crack widths, is a laboratory test of the product in a test specimen, not a site acceptance test. Product tests prove what a resin can do; site records and cores prove what the crew achieved.

Safety and VOC Rules for Injection Resins and Crack Sealants#

Crack repair products carry three main hazard groups, diisocyanates in polyurethane resins, epoxy resins and their hardeners, and cement and silica dust from cementitious materials and drilling, and each has its own rule. Polyurethane injection resins and sealants with 0.1 % by weight or more diisocyanates need a label statement since 2022-02-24 and documented training before industrial or professional use since 2023-08-24, renewed at least every 5 years (REACH Annex XVII entry 74, Regulation (EU) 2020/1149). The monomer 4,4'-MDI (CAS 101-68-8) is harmonized under CLP Annex VI index 615-005-00-9 with H315, H317, H319, H332, H334, H335, H351 and H373; polyurethane resins as a class have no Annex VI entry, so see the product SDS. EU exposure limits and training content are set out under diisocyanates rules.

Liquid epoxy resin (CAS 25068-38-6) is harmonized under CLP Annex VI index 603-074-00-8 with H315, H317, H319 and H411; for amine hardeners, see the product SDS. Cement-based plugs and mortars carry the portland cement line "No Annex VI entry; ECHA C&L notified classification: H315, H317, H318, H335"; see the product SDS. REACH Annex XVII entry 47 limits soluble Cr(VI) to 2 mg/kg (0.0002 %) of the total dry weight of the cement. Drilling ports and routing grooves raises respirable crystalline silica, which OSHA 29 CFR 1926.1153 limits to a PEL of 50 µg/m³ as an 8-hour TWA, with an action level of 25 µg/m³, effective 2016-06-23.

South Coast AQMD Rule 1168 (amended 2022-11-04) has no injection-resin category, so a resin falls under the category it is sold and labeled as, with reactive products measured after cure: All Other Architectural Sealants 50 g/L (0.42 lb/gal), All Other Adhesives 250 g/L (2.09 lb/gal), or Grout (cement-based sealant) 65 g/L (0.54 lb/gal). Outside the South Coast, the federal EPA AIM rule (40 CFR 59 subpart D) sets no VOC content limit for adhesives or sealants.

How Is Concrete Crack Repair Bought? Scope, Specification and Cost#

Concrete crack repair is bought per crack or per meter of crack, and a usable quote names the crack map, the method, the product standard, the acceptance test and the access. The crack map is the base of every price: each crack with its length, its widest width, whether it is wet and whether it moves. Two contractors pricing the same wall without a shared map price different jobs.

Two dated public ranges exist. Installed epoxy crack injection costs USD 250 to 1,000 per crack in the US (Fixr line item, updated 2026-02-06). Installed crack filling or sealing on flatwork costs USD 1.64 to 9.84 per m (USD 0.50 to 3 per linear ft) in the US (HomeGuide, 2025-12). No dated public range covers routing and sealing per meter, gravity filling per square meter or FRP strengthening, so those jobs are priced from the crack map, the access (scaffold, lift or confined space), the water state, the cure window and the number of cores the acceptance test calls for.

A specification that lets quotes be compared names the items below.

• Method per crack: epoxy injection, leak-sealing injection, gravity filling, rout and seal, or concrete repair.
• Product standard: EN 1504-5 category, or ASTM C881/C881M-20a type, grade and class for epoxy; ASTM C920-18(2024) class for sealants.
• Acceptance: cores with at least 90 % of the crack filled under ICRI 210.1R-2016, the number of cores, and the shift records.
• Repair guide: ACI PRC-546-23, Concrete Repair Guide, for surface preparation and repair of the surrounding concrete.
• Access and cure: working hours, closure time and the concrete surface temperature that sets the ASTM C881 class.

Who Applies Concrete Crack Repair?#

Structural injection, leak sealing and routing and sealing are applicator work; cosmetic filling of a dormant crack is the part owners take on themselves. A cosmetic latex filler is neither waterproof nor structural, so any crack that leaks, moves or carries load goes to an injection applicator with pumps, ports and records.

Quality control on concrete repair has its own credential: the ICRI Concrete Surface Repair Technician (CSRT) certification is a QC/QA and inspector credential, valid 5 years, not a requirement for the applicator crew. In the EU, every worker who handles polyurethane resins with 0.1 % by weight or more diisocyanates needs the documented REACH entry 74 training, renewed at least every 5 years.

Is It Worth Repairing a Concrete Crack?#

Yes, when the crack leaks, keeps moving, weakens the member or comes from corroding steel; a dormant, dry hairline crack that does none of these needs no structural repair. Such a crack is measured and its width recorded, so that a later reading shows whether it has started to move. A sealer is no substitute for repair: penetrating water repellents seldom stop water through cracks wider than 0.5 mm (0.02 in), per BIA Technical Note 6A (August 2008). Basements, decks, tanks, facades and the other structures and problems are listed under construction chemicals by application.

What is the best way to fix cracked concrete?#

There is no single best way: the method follows the crack, with epoxy injection for dormant structural cracks, polyurethane for leaks and routing and sealing for moving cracks. Fine dormant cracks in slabs take gravity filling, and corrosion cracks take concrete repair. A product chosen before the crack is classified is a guess.

What is the best filler for concrete floor cracks?#

On a floor, a dormant fine crack takes a gravity-fed low-viscosity resin, and a routed crack under wheeled traffic takes a semi-rigid filler that supports the crack edges. Crack fillers and floor crack repair are covered on their own pages, listed in the tables above.

Can new concrete be poured over cracked concrete?#

An overlay over a dormant crack can work, but a moving crack reflects through any bonded topping, so the crack is routed and sealed or injected first. Thin bonded toppings are covered under concrete resurfacers.

When does a concrete crack need a structural engineer?#

A crack needs an engineer when it is wider than the design limit for its exposure, still growing, or caused by load, settlement or corroding steel. AASHTO limits of 0.30 or 0.38 mm (0.012 or 0.015 in) by exposure, as cited in ACI PRC-224.1-07, are one reference point for that judgment.

Does a penetrating sealer seal concrete cracks?#

No: penetrating water repellents seldom stop water through cracks wider than 0.5 mm (0.02 in) (BIA Technical Note 6A, August 2008). Penetrating sealers protect the uncracked surface; a crack still needs its own repair.

Are asphalt driveway cracks repaired the same way?#

No: asphalt pavement crack sealers are a different product family, covered on asphaltadditives.net.