Construction grouts (structural grouts) are hydraulic-cement or epoxy products placed by flow into confined gaps under baseplates and machinery, in precast connections and in post-tensioning ducts, where they transfer load without shrinking from the steel or concrete above. They come in 3 product classes and 1 installation practice, so which grout fits a column base, a compressor skid or a bridge tendon?
The same materials are sold as cementitious, high-strength, high-performance cementitious, flowable or precision grout. British specifications also say underplate grout, and German practice splits Vergussmörtel (aggregate up to 4 mm) from Vergussbeton (aggregate above 4 mm). Construction grouts are one of the 15 families of construction chemicals.
Each class has its own document: ASTM C1107/C1107M-26 Grades A, B and C for packaged non-shrink cementitious grout, ASTM C579-23 and the C1339/C1339M-24 bearing-area classes (high above 85 %) for epoxy machinery grout, and PTI M55.1-19 or EN 447:2007 for post-tensioning grout. A C1107 pass does not prove zero shrinkage: a 2016 FHWA study measured more than 500 microstrain in grouts that passed. Field strength is tested on 50 mm (2 in) cubes, never cylinders, and two non-shrink grouts sold for USD 14.85 and USD 16.34 to 22.40 per 50 lb (22.7 kg) bag, material only, at US distributors in October 2026.
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 Structural Grout?#
Structural grout is a packaged hydraulic-cement or epoxy material mixed to a plastic, flowable or fluid consistency and placed into a confined gap, which it fills completely to carry load from steel or precast elements into the foundation. Cementitious grouts reach that state with water only, and baseplates also take a dry-pack consistency; the consistency is chosen for the gap and the pour length. The substrates are concrete below and steel or precast concrete above.
Non-cementitious grout in this family means epoxy machinery grout, a 3-component, 100 % solids resin system mixed on site. "High-strength" and "high-performance" describe a value printed on a data sheet, not a product class. The class is set by the governing document, such as an ASTM C1107/C1107M-26 grade for a cementitious grout or a PTI M55.1-19 class for a duct grout.
Structural grout is not tile grout, chemical grout or masonry grout#
Four other products share the word grout, listed below.
- tile grout: the joint filler between ceramic, porcelain and stone tiles, a finishing and sealing product rather than a load path.
- chemical grouting: silicate, acrylate and polyurethane grouts injected into soil and leaking structures for water cut-off.
- cementitious anchoring grouts: poured grouts that set posts, railings and bolts in pockets or oversize holes.
- Masonry grout to ASTM C476, which fills the cores of hollow masonry units, covered as a section of dry-mix mortars.
How Do Structural Grouts Work?#
Structural grouts work in 2 ways: cementitious grouts hydrate with a controlled expansion that keeps them at or above placement height, and epoxy grouts cure by an epoxy-amine reaction that bonds a filled resin with low shrinkage. The expansion offsets settlement, bleed and early shrinkage, while the epoxy bond holds steel and concrete together. Post-tensioning grouts add a third function: they protect prestressing strand inside a duct.
Controlled expansion and low water content in cementitious grouts#
Non-shrink cementitious grouts combine Portland cement, graded quartz or mineral aggregate and an expansive system that acts either before the grout hardens or after it. Pre-hardening expansion comes from gas-forming agents, post-hardening expansion from sulfoaluminate or lime systems, and metallic grouts use iron aggregate; shrinkage-reducing and water-reducing admixtures complete the mix. Low water content gives high early strength and full-contact bearing, so load passes into the foundation through the whole grout pad.
Post-tensioning grouts work differently: they fill the duct to bond the tendon to the structure and keep the strand in an alkaline, passive environment. Bleed resistance matters most here, because strand wicks water upward and the bleed water leaves voids and soft grout at high points. These grouts are Portland cement mixes, sand-free or with aggregate of at most 1 mm.
Why a non-shrink label does not mean zero shrinkage#
A grout can pass ASTM C1107 and still shrink: in a 2016 FHWA study (FHWA-HRT-16-080), non-shrink cementitious grouts that expanded under the C1107 tests showed more than 500 microstrain of sealed shrinkage. The C1107 grades judge height change against the initial placement height, so a pass describes that height, not the whole volume change of the hardened grout.
Drying added at least 1,000 microstrain in the same FHWA-HRT-16-080 report, published in December 2016. FHWA therefore recommends the ASTM C157 length-change test and the ASTM C1698 autogenous-strain test as supplements to the C1107 series. A non-shrink label is a claim about early height change, not a promise of zero shrinkage over the service life.
Epoxy grouts: resin cure, bond and bearing contact#
Epoxy machinery grouts are 3-component, 100 % solids systems: a resin, an amine or amidoamine hardener and a graded dry aggregate, mixed on site. The resin and hardener react in an exothermic epoxy-amine addition that binds a high aggregate load. Strong bond to steel and concrete, low shrinkage and creep, damping and chemical resistance keep machine alignment under vibration.
Units run from about 11 to 57 L (0.4 to 2.0 ft³) of grout each. Cure slows on cold foundations, which makes foundation temperature part of every placement plan. The binder chemistry behind these properties, from bisphenol epoxy resin to amine hardeners, is covered under epoxy resins and hardeners.
Types of Structural Grout: 3 Product Classes and 1 Installation Practice#
Structural grouts fall into 3 product classes, packaged non-shrink cementitious grouts, three-component epoxy machinery grouts and cement grouts for post-tensioning tendons, plus 1 installation practice, baseplate and equipment grouting, that uses the first two. The table below compares binder, consistency and the governing US and European documents of each.
| Class | Binder and form | Consistency | US basis | EU or German basis |
|---|---|---|---|---|
| Non-shrink cementitious | Portland cement, aggregate, expansive system; 1K powder | plastic, flowable, fluid | ASTM C1107/C1107M-26 Grades A, B, C | EN 1504-6:2006 (DoP); DAfStb VeBMR 2019-07 |
| Epoxy machinery | resin, amine hardener, aggregate; 3K, 100 % solids | flowable | ASTM C579-23 Method B; C1339/C1339M-24 | no harmonized EN |
| Post-tensioning | cement, sand-free or at most 1 mm aggregate; prepackaged or site-batched | fluid | PTI M55.1-19 Classes A to D | EN 447:2007, EN 445:2007, EN 446:2007 |
| Baseplate practice | either cementitious or epoxy class | plastic to fluid, dry-pack | ACI SPEC-351.4-24; ACI PRC-351.1-12 (reapproved 2024) | none stated |
1. Packaged non-shrink cementitious grouts#
Non-shrink cementitious grouts are one-component powders mixed with water only, sold in 25 kg, 50 lb (22.7 kg) and 55 lb (24.9 kg) bags and 1,500 kg (3,300 lb) bulk bags. ASTM C1107/C1107M-26 defines them as packaged dry hydraulic-cement grouts that show no height change below the initial placement height, and sorts them into Grade A (pre-hardening volume-adjusting), Grade B (post-hardening) and Grade C (both). British specifications call the class precision grout, and in the EU it declares performance under EN 1504-6:2006 for lack of a dedicated harmonized standard.
2. Three-component epoxy machinery grouts#
Epoxy machinery grouts are 100 % solids resin grouts for equipment that vibrates, rotates or meets chemicals, tested for strength under ASTM C579-23 Method B and for bearing area under ASTM C1339/C1339M-24. Their benefit is function rather than a strength number: bond, damping and chemical resistance hold a machine in alignment. No harmonized European standard covers machinery grout.
3. Cement grouts for post-tensioning tendons#
Post-tensioning grouts are sand-free or fine (at most 1 mm aggregate) cement grouts pumped into tendon ducts to bond the strand and protect it from corrosion. PTI M55.1-19 sorts them into Class A (nonaggressive exposure), Class B (aggressive exposure), Class C (prepackaged) and Class D (engineer-defined), and Europe uses EN 447:2007 with its test methods in EN 445:2007 and grouting procedures in EN 446:2007. A C1107 baseplate grout never goes into a duct.
4. Baseplate and equipment grouting practice#
Baseplate grouting fills the leveling gap under a plate so load passes through full contact instead of through shims, placed from one side under a hydrostatic head that drives the air out. The cementitious work is specified by ACI SPEC-351.4-24, and ACI PRC-351.1-12 (reapproved 2024) reports on both epoxy and cementitious grouting under equipment. The foundation is roughened to the profile named in the product data sheet, and those profiles are graded under concrete surface profile.
Where Is Structural Grout Used? Selection by Load and Exposure#
Structural grout is used under steel columns and precast elements, under machinery, in post-tensioning ducts, in marine repairs and in high-strength connections, and the load type sets the class. Static loads should take a cementitious non-shrink grout; rotating, reciprocating, impact and chemical loads should take epoxy; tendon ducts should take a PTI M55.1-19 Class C prepackaged or EN 447:2007 grout. The table below maps each setting to its class and key document.
| Setting | Load and exposure | Grout class | Key document |
|---|---|---|---|
| Steel columns, precast connections and static equipment | static bearing | non-shrink cementitious | ASTM C1107/C1107M-26; ACI SPEC-351.4-24 |
| Machinery foundations | rotating, reciprocating, impact, chemicals | epoxy machinery | ASTM C579-23, C1339/C1339M-24; ACI PRC-351.1-12 (reapproved 2024) |
| bridges, tunnels and marine structures | bonded post-tensioning tendons | post-tensioning | PTI M55.1-19; EN 447:2007 |
| marine concrete repair and protection | submerged, tidal | anti-washout cementitious or epoxy; filled pile jackets | product data sheet |
| UHPC connections and offshore wind (section below) | high-strength connections | hydraulic-cement UHPC and offshore grouts | product data sheet |
Steel columns, precast connections and static equipment#
Column bases, precast pockets and joints, bearing plates and general equipment take cementitious non-shrink grout at a consistency chosen for the gap and the pour length. The two common failures are voids and low bearing area from pouring from two sides or with too little head, and shoulder cracking at the exposed edge of the pad.
Rotating and reciprocating machinery#
Compressors, pumps, engines and other machines that vibrate, rotate or reciprocate sit on epoxy grout, whose bond, damping and chemical resistance hold alignment. The failure points are cracking in long pours without expansion joints, voids and low bearing area, and creep with loss of alignment at high service temperature. Anchor bolts that hold the machine down are a separate product decision, and bolts set in drilled holes are covered under chemical anchors.
Bridges and post-tensioned structures#
Bonded post-tensioning tendons in bridges and buildings are grouted with a PTI M55.1-19 Class C prepackaged grout in the US or an EN 447:2007 grout in Europe. The failure mode is bleed: water collects at high points and anchorages, leaving voids and soft grout that let the strand corrode. Class C grouts carry a robustness test at the minimum, maximum and 1.1 times the maximum water stated on the bag.
Marine and submerged grouting#
Under water, anti-washout cementitious grouts or epoxies are placed by divers, and pile jackets are stay-in-place GRP forms filled with cementitious or epoxy grout. Tidal and splash zones add galvanic protection inside the jacket, a repair system rather than a grout choice.
UHPC connection grouts and offshore wind grouts#
UHPC connection grouts and offshore wind grouts are hydraulic-cement grouts made for very high strength in narrow connections, sold as separate product lines. Their test basis is the product's own data sheet and the project specification, since none of the documents on this page sets their strength or fatigue requirements.
Which Standards Govern Structural Grouts?#
Structural grouts are governed by class: ASTM C1107/C1107M-26 for non-shrink cementitious grout, ASTM C579-23 and C1339/C1339M-24 for epoxy machinery grout, PTI M55.1-19 and EN 447:2007 for post-tensioning grout, and ACI SPEC-351.4-24 for placement under equipment. The US documents are product specifications and test methods; the European ones split between a harmonized repair standard, a tendon-grout standard and a German guideline.
US specifications and reports: ASTM, PTI and ACI#
ASTM C1107/C1107M-26, active since its page update of 2026-09-15, classifies packaged non-shrink cementitious grout as Grade A (pre-hardening volume-adjusting), Grade B (post-hardening) or Grade C (both). Its scope is a packaged dry hydraulic-cement grout for use under applied load, where a height change below the initial placement height is to be avoided, and it needs only mixing water. ASTM Subcommittee C09.43 maintains it, and the grades are never called classes or types.
Epoxy grouts follow 3 ASTM documents. ASTM C579-23 Method B covers compressive strength of resin grouts with aggregate from 1.6 to 10 mm, ASTM C1339/C1339M-24 (2024-08-14) rates effective bearing area as high above 85 %, medium 70 to 85 % or low below 70 % at a 25 or 50 mm (1 or 2 in) pour, and ASTM C1181/C1181M-17 for creep is withdrawn with no replacement. For placement, ACI SPEC-351.4-24 specifies cementitious grouting between foundations and equipment bases and ACI PRC-351.1-12 (reapproved 2024) reports on both types. PTI M55.1-19, cited by Caltrans on 2025-12-29, keeps the Class C robustness test and an annual independent audit of the maker's quality control. The grade definitions and test series are set out under ASTM C1107.
European and German documents for grouts#
Europe has no harmonized product standard for precision or machinery grout, so many European precision grouts declare performance under EN 1504-6:2006, the harmonized standard for anchoring reinforcing steel. EN 1504-6:2006 was published on 2006-08-22 and is harmonized under the Construction Products Regulation (EU) No 305/2011, which gives a grout a Declaration of Performance and CE marking.
Post-tensioning grout has its own trio: EN 447:2007 (published 2007-10-02 by CEN/TC 104/SC 2) sets the basic requirements, EN 445:2007 the test methods and EN 446:2007 the grouting procedures; EN 447:2007 replaced EN 447:1996. A CEN systematic review of EN 447 ran from 2025-06-24 to 2026-10-14. 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.
Germany adds the DAfStb guideline for Vergussbeton and Vergussmörtel (VeBMR), edition 2019-07 and current at DIN Media, with a minimum strength class of C50/60. It separates Vergussmörtel, with aggregate up to 4 mm, from Vergussbeton above 4 mm. Each EN 1504 part and its CE route is explained under EN 1504.
Field and qualification tests: cubes, flow and bearing area#
Cementitious grout strength is tested on 50 mm (2 in) metal cube molds per ASTM C942/C942M-21 or the C1107 modification of ASTM C109, never on cylinders. Epoxy grout strength is tested on cubes per ASTM C579-23 Method B.
Consistency is checked at placement. The flow cone of ASTM C939/C939M-22 applies only to fluid grouts with an efflux time of 35 s or less; stiffer mixes go on the flow table of ASTM C230/C230M-23 or ASTM C1437-26 (updated 2026-10-16). Height change is a qualification test, run under ASTM C827/C827M-23 at early age and ASTM C1090/C1090M-23 after hardening, not a site test.
After cure, the pad is sounded for voids, and an epoxy pad's bearing area is qualified against the ASTM C1339/C1339M-24 classes. The cube method itself, its 50 mm (2 in) specimens and the current C109/C109M-26a edition (2026-07-30) are described under ASTM C109 cube test.
VOC Rules and Safety for Structural Grouts#
Cementitious grouts are water-mixed powders and epoxy machinery grouts are 100 % solids, so their safety questions center on wet cement, crystalline silica dust and epoxy sensitization rather than solvent emissions. VOC rules still matter where an air district names grout as a category.
Which VOC rules name grouts#
South Coast AQMD Rule 1168 (amended 2022-11-04) has a Grout category, defined as a cement-based sealant formulated to fill or seal gaps, including those of tile installations, with a limit of 65 g/L (0.54 lb/gal) less water and exempt compounds.
Rule 1168 (j)(7) exempts dry mixes containing no polymer and mixed only with water from the container-labeling requirements of subdivision (g); it is not an exemption from VOC limits. Which category a given structural grout falls under is read from the product's own VOC declaration, and all categories are listed under VOC limits for construction chemicals.
Cement, crystalline silica and epoxy hazards#
Portland cement has no harmonized classification: 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 when hydrated, and the reducing agent works only for the storage period stated on the bag.
Mixing dry grout releases respirable crystalline silica from its quartz aggregate. 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, which amends Directive 2004/37/EC. Quartz (crystalline silica) has no Annex VI entry and no majority ECHA C&L classification, so its classification is product-specific: see the product SDS. California Prop 65 lists "Silica, crystalline (airborne particles of respirable size)" for cancer since 1988-10-01.
Epoxy grouts carry the resin and hardener hazards. Liquid epoxy resin (CAS 25068-38-6) has the harmonized CLP Annex VI classification index 603-074-00-8: H315, H317, H319, H411, and BADGE (CAS 1675-54-3) has index 603-073-00-2: H315, H317, H319. Common amine hardeners carry H314 in their own Annex VI entries: IPDA (612-067-00-9) H302, H314, H317, H318; TETA (612-059-00-5) H312, H314, H317, H412; DETA (612-058-00-X) H302, H312, H314, H317. Formulated grout components: see the product SDS. REACH Annex XVII entry 74 does not apply, because epoxy-amine grouts contain no diisocyanates, and neither the epoxy resin nor BADGE is Prop 65 listed as such, while bisphenol A and epichlorohydrin are.
Complete List of Structural Grout Classes: All 4 Entries#
The complete list below gives the 3 structural grout classes and the baseplate grouting practice with their chemistry, US and European documents, typical use, applicator need and a dated material price where two products publish one.
| Class | Chemistry | US basis | EU basis | Typical use | Applicator | Material price (dated) |
|---|---|---|---|---|---|---|
| non-shrink grout | Portland cement, aggregate, expansive system; 1K powder | ASTM C1107/C1107M-26 Grades A, B, C | EN 1504-6:2006 (DoP); DAfStb VeBMR 2019-07 (DE) | columns, precast, general equipment | depends | USD 14.85 (one product) and USD 16.34 to 22.40 (one product) per 50 lb (22.7 kg) bag; USD 0.65 and 0.72 to 0.99 per kg; material; US distributors; 2026-10 |
| epoxy machinery grouts | 3K 100 % solids epoxy and aggregate | ASTM C579-23 Method B; C1339/C1339M-24 | no harmonized EN | rotating and reciprocating machinery | yes | not given (one product published) |
| post-tensioning grouts | cement, sand-free or at most 1 mm aggregate | PTI M55.1-19 Classes A to D | EN 447:2007 (EN 445, EN 446:2007) | bonded post-tensioning tendons | yes | not published |
| grouting baseplates and column bases | either class | ACI SPEC-351.4-24; ACI PRC-351.1-12 (reapproved 2024) | none stated | leveling gaps under plates | yes for machinery; concrete contractor for columns | no public installed cost |
Prices are US distributor material prices for two products, October 2026, before freight and tax; per-kg values are calculated from the 50 lb (22.68 kg) bag.
No public dated source gives an installed cost per baseplate or per tendon, so a quote follows from the gap, the area or volume, the access and the class. A price per kg also needs the yield per bag before two grouts can be compared on volume.
Which Structural Grout Is Strongest?#
No grout class is strongest by definition: strength is a data-sheet value at a stated age, temperature and consistency. Two makers' epoxy machinery grouts list 96.6 to 100 MPa (14,000 to 14,500 psi) at 7 days, against 51.7 to 68 MPa (7,500 to 9,860 psi) at 28 days for two makers' cementitious grouts, each on the maker's own test basis. These are typical product values, not standard minimums, and the consumer comparison of tile grouts is under epoxy grout vs cementitious grout.
How much does structural grout cost?#
Two non-shrink cementitious grouts sold at US distributors in October 2026 for USD 14.85 and USD 16.34 to 22.40 per 50 lb (22.7 kg) bag, material only (ccssstore.com, emisupply.com). Per kilogram, that is USD 0.65 and USD 0.72 to 0.99 per kg before freight and tax. Volume sets the bag count: 1 m³ fills 40 m² at 25 mm, and 1 ft³ fills 12 ft² at 1 in, before waste. Epoxy machinery grout prices are not given here, because only one product publishes one.
How do you check a non-shrink claim on a data sheet?#
Check which ASTM C1107/C1107M grade the data sheet declares and at which consistency it was tested, not the brand name. A brand question, such as whether a retail bag is a non-shrink grout, is answered the same way: the declared grade, the edition and the test consistency on the sheet decide it.
Can structural grout fill cracks in concrete?#
No: structural grout fills gaps under and around elements, while cracks are classified first and then injected or sealed.
The methods for each crack type are compared under concrete crack repair.
How is grout different from mortar and concrete?#
Grout is placed by flow into a confined gap, while mortar is troweled and concrete is compacted. German practice draws the line between Vergussmörtel and Vergussbeton at 4 mm maximum aggregate, so a grout with coarser aggregate is classed as a grouting concrete.
Does structural grout need a specialist applicator?#
It depends on the class: machinery and epoxy grouting is done by specialist grouting contractors or millwrights, column grouting by concrete contractors, and post-tensioning grouting by post-tensioning specialists. Precision grouting under equipment falls with the machinery trades.
Does cold weather slow epoxy grout cure?#
Yes: epoxy grout strength gain drops sharply on cold foundations, so cure and return-to-service times are read from the data sheet at the foundation temperature. A contact thermometer on the foundation and the baseplate gives that temperature.