Which documents govern repair mortars
Mortars and concretes for reinstating the section and the cover are covered by the European standard EN 1504-3:2005 “Structural and non-structural repair”: it specifies how a product is to be identified, which performance characteristics, including durability, are to be confirmed by testing and which safety requirements are to be met. In Russia the national standard GOST R 56378-2015 applies; it was drawn up on the basis of EN 1504-3 with a non-equivalent degree of correspondence (NEQ).
| Document | Details |
|---|---|
| GOST R 56378-2015 “Materials and systems for the protection and repair of concrete structures. Requirements for repair mortars and adhesive bonds of the contact zone in the restoration of structures” | Approved by Rosstandart (Russia’s Federal Agency on Technical Regulating and Metrology) Order No. 214-st of 03.04.2015, in force since 01.09.2015. Amendment No. 1 (Order No. 583-st of 07.07.2022) has applied since 01.09.2022: text corrections and updated references — in particular, GOST 31356-2007, which is no longer in force in Russia, was deleted and GOST R 58277-2018 was introduced |
| Scope of GOST R 56378-2015 | Mortars with cementitious, polymer-cement (polymer-modified cement) and polymer binders, and their bond to the concrete of the structure being restored — structural and non-structural; structures in the open air, underground and underwater, new and in service. Special cases — work in extreme environmental conditions, for example at very low temperatures, unforeseeable actions and seismic loads — are outside the scope of the standard |
| EN 1504-3:2005 | European product standard for structural and non-structural repair |
There is no interstate standard for repair mortars in the series “Materials and systems for the protection and repair of concrete structures”: in the Rosstandart register this subject is covered only by GOST R 56378-2015.
Structural and non-structural repair
The dividing line is whether the restored area takes part in the structural behaviour. In structural repair, the volume structure of the concrete is restored: the mortar replaces the lost section of a load-bearing member, carries the design forces together with the old concrete and becomes the cover to the reinforcement. Classes R4 and R3 are intended for this. In non-structural repair, the geometry and the surface are restored — spalls, blowholes, levelling layers through which no load is transmitted; these are classes R2 and R1.
In the terms of GOST 32016-2012, repair mortars serve above all principle 3 “concrete restoration” — methods 3.1 (hand application), 3.2 (casting) and 3.3 (spraying) — and also method 4.4 (adding concrete or mortar in strengthening) and methods 7.1 and 7.2: increasing the cover and replacing contaminated or carbonated concrete. For sprayed concrete, the catalogue of standards of the research institute for technical norms and standardization of the Ministry of Construction includes O’zMSt EN 14487-1:2025, an identical adoption of EN 14487-1:2022.
Requirements for classes R1–R4
The main properties to GOST R 56378-2015. The strength of mortars is determined by the GOST 30744 procedure and that of concretes to GOST 10180; bond is tested on reference concrete substrates with an abrasively prepared surface, as described in the annexes to the standard.
| Property | Method | R4 | R3 | R2 | R1 |
|---|---|---|---|---|---|
| Compressive strength | GOST 30744, GOST 10180 | ≥ 45 MPa | ≥ 25 MPa | ≥ 15 MPa | ≥ 10 MPa |
| Chloride ion content | GOST 5382 | ≤ 0.1 % | ≤ 0.1 % | ||
| Bond strength to the substrate | per the standard | ≥ 2 MPa | ≥ 1.5 MPa | ≥ 0.8 MPa | |
| Bond after the restrained shrinkage or expansion test | annex to the standard | ≥ 2 MPa | ≥ 1.5 MPa | ≥ 0.8 MPa | no requirement |
| Carbonation resistance (CO₂ permeability) | GOST 31383-2008, Section 6 | effective diffusion coefficient no higher than that of the reference concrete | not applicable for protection against carbonation | ||
| Elastic modulus in compression | GOST 24452 | ≥ 20 GPa | ≥ 15 GPa | no requirement | |
| Bond after cycling: freeze–thaw with salts (50), in air (30), “thunder-shower” thermal shock (30) | annex to the standard | ≥ 2 MPa | ≥ 1.5 MPa | ≥ 0.8 MPa | visual inspection |
| Coefficient of linear thermal expansion | GOST 32618.2 | the declared value is stated; no test is needed if the mortar has passed the cyclic tests for bond durability | |||
| Capillary absorption | per the standard | ≤ 0.4 kg/(m²·√h) | no requirement | ||
Notes to the table that matter at acceptance:
- For classes R2 and R1, if the specimen fails within the repair material itself rather than at the interface, a tensile strength of at least 0.5 MPa is sufficient.
- For bond after the shrinkage and cyclic tests, the requirement applies to the mean result, and any individual result must reach at least 75 % of the minimum declared by the manufacturer.
- R2 and R1 mortars do not protect against carbonation: if it threatens the reinforcement, a surface protection system to GOST 32017-2012 is needed over the repair.
- If a mortar has withstood 50 freeze–thaw cycles with salts, the requirements for the other two types of cycling are deemed to be met.
- The strength in the table is the value declared by the manufacturer; it amounts to up to 80 % of the strength obtained in the identification tests.
- Not every row applies to every mortar: the coefficient of thermal expansion is specified for polymer-bound mortars, capillary absorption for cementitious and cement-polymer mortars. The applicability of each row follows the footnotes to the table in the standard.
The values are taken from the text of GOST R 56378-2015. Amendment No. 1 replaced some of the referenced test methods, including those for determining bond, so check test reports against the current edition.
A GOST class and an EN class are confirmed differently
The class designations R1–R4 in GOST R 56378-2015 and EN 1504-3 are the same, but the test methods differ and individual requirements may differ too — this follows directly from the NEQ degree of correspondence. So “R4 to EN 1504-3” and “R4 to GOST R 56378-2015” are confirmed by different test reports. In the design, state the class together with the document, and at acceptance require test reports to that very document. A summary of the EN 1504-3 requirements that manufacturers quote in their technical data sheets is in our “Concrete repair and protection” guide, and the types of mortar and how to choose them are on the “Concrete repair mortars” page.
What to specify in the design and check on site
- The mortar class and the document to which it is confirmed; for load-bearing members, R3 or R4 as calculated.
- The application method — by hand, by pouring into formwork or by spraying — and the permissible layer thickness according to the material documentation.
- Substrate preparation: removal of weakened and contaminated concrete, exposing and cleaning the reinforcement, the required roughness, the pre-wetting regime for cementitious mortars.
- Compatibility of the repair material with the old concrete in strength and elastic modulus: the mortar is selected to suit the properties of the substrate, not on the principle of “the stronger, the better”.
- On-site bond testing by the pull-off method; in Uzbekistan there is a national test method standard for this, O’zMSt EN 1542:2025.
- Curing of the fresh mortar, and surface protection if an R1 or R2 mortar has been used or the damage was caused by carbonation and chlorides.
- Documents for each batch: declared values and test reports to the chosen document.
What applies in Uzbekistan
GOST R 56378-2015 is a national standard of Russia; in Uzbekistan it is applied when the design or the contract refers to it. ShNK 2.03.11-24 does not set classes of repair mortars, but refers to GOST 32016-2012, which defines the principles of repair, and to GOST 32017-2012 on surface protection after it. As of October 2026, the catalogue of standards of the Ministry’s research institute contains no national adoption of EN 1504-3. Therefore the requirements for a repair mortar on a particular facility are set in the design — to EN 1504-3 or to GOST R 56378-2015 — and confirmed by test reports to the chosen document.
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