Repair of reinforced concrete structures in compliance with the European Standard EN 1504
The issues associated with the repair of concrete and reinforced concrete elements and structures which for whatever reason have become damaged during the use of the building or during its construction are becoming increasingly common lately.
The technical solutions for repairing defects in the structures require production of special materials that will be applied accordingly. However, proper maintenance of concrete structures is the main requirement for extension of their service life.
Therefore, restoration, repair and other methods for protection of concrete structures should be carried out by specially trained personnel competent for each stage of the process and specially designed material for that purpose should be applied.
In order to facilitate and properly direct the work activities, the new European Standard EN1504 is implemented. It represents the culmination of over 15 years of work, consultation and meetings with professionals from all sectors of the concrete repair industry.
The repair and protection of concrete structures requires a relatively complex assessment and design. By introducing and defining the key principles of protection and repair, the European Standard EN 1504 helps the owners and professional builders to reach a full understanding of the problems and solutions during the different stages of the process. The European Standard EN 1504 covers the products and systems for repair and protection of concrete structures and it targets all the involved parties: investors, engineers, designers, contractors, supervisors, manufacturers of building materials, etc.
EN 1504 – 1 – Terms and definitions used in the standard
- The first part of the standard mainly covers the definitions of the terms relating to the repair, maintenance, protection and strengthening of concrete structures.
EN 1504 – 2 – Specifications for surface protection systems for concrete
- This part of the standard covers the following surface protection systems:
- Hydrophobic impregnation(treatment of the concrete to produce a water-repellent surface, to have the pores and capillaries internally coated, to avoid forming a film on the concrete surface, and to have little or no change in the appearance of the concrete).
- Impregnation(treatment for reducing the porosity and strengthening the concrete surface, the pores and capillaries are partially or completely filled; materials that can be used as binders include organic polymers. This treatment leads to formation of discontinuous thin film on the concrete surface).
- Coating(this treatment leads to formation of a continuous layer on the concrete surface measuring not more than 5 mm in thickness. Materials that can be used as binders include organic polymers, organic polymers with cement applied as filler or hydraulic cement modified with polymer dispersion).
EN 1504 – 3 – Specifications for structural and non-structural repair
- The standard specifies the requirements for identification, performance (including durability of materials) and safety of the products and systems to be used for structural and non-structural repair of concrete structures. This part of the standard covers repair mortars and concretes, which can be used in conjunction with other materials and systems, to restore or replace defective concrete and to protect reinforcement, in order to extend the service life of the structure.
EN 1504 – 4 – Specifications for structural bonding
- The fourth part of the standard specifies the requirements for the products to be used for structural bonding of concrete to concrete or for bonding of other materials to an existing concrete structure. This part covers:
- bonding of external plates of steel to a concrete structure;
- bonding of two hardened concrete elements (for example, two reinforced-concrete pre-stressed girders);
- casting of fresh concrete to an already hardened concrete by forming an adhesive bonded joint with the existing concrete structure.
EN 1504 – 5 – Concrete injection
- The fifth part of the standard specifies the requirements and criteria of injection products for use in concrete structures. The objective of concrete injection is in fact to strengthen the concrete structure, to avoid penetration of aggressive agents in the concrete and to increase watertightness. This group includes materials based on epoxies, polyurethanes, cement and acrylics.
EN 1504 – 6 – Anchoring of reinforced steel bars
- This part of the standard defines the requirements for the specification, performance and safety of products to be used as anchors for the purpose of strengthening the concrete structure. This part of the standard also covers those applications as specified in Parte 4 of the standard which refer to structural strengthening.
EN 1504 – 7 – Reinforcement corrosion protection
- Part 6 of the European Standard specifies requirements for the identification and performance of materials and systems used for the protection of existing reinforcement in concrete structures under repair. Two types of products are defined: active and barrier coatings for protection of the reinforcement. Active coatings are considered those which contain Portland cement, i.e. which increase the alkalinity of concrete structures. Barrier coatings are considered those which isolate the reinforcement from water, and most common products are the polymer base coatings.
EN 1504 – 8 – Quality control and evaluation of conformity
- This part of the standard is specially intended for the manufacturer of the materials and the certification institute, the so called “Notified Body”. It specifies the procedures for quality control, evaluation of conformity, CE-marking and labelling of the products.
EN 1504 – 9 – General principles for the use of products and systems for repair and protection of concrete and reinforced-concrete structures
- This part of the European standard specifies the basic principles which will be used, individually or combined, with the purpose of protection and repair of concrete structures, regardless if they are above ground or in water. The repair of any building would be a success if we make a proper assessment of defects and identification of the causes of defects and all the following stages will largely depend on these issues. Part 9 of the standard puts a particular emphasis on the importance of these issues and divides the procedure in several key stages:
- Assessment of defects (state of the building)
- Identification of the cause of defects (deterioration of the structure)
- Setting the objectives of protection and repair together with the owners of the structure
- Selection of the appropriate principle(s) for protection and repair
- Selection of the methods
- Specification of the properties of the products and systems
- Specification of maintenance requirements for the next protections and repairs.
- This part of the standard specifies 11 groups of principles and methods for protection, depending if the defects appear on the concrete or on the reinforced steel in the structure:
- Protection against ingress
- Protection against moisture
- Concrete restoration
- Structural strengthening
- Physical resistance
- Resistance to chemicals
- Preserving or restoring to a passive condition
- Increasing resistivity
- Cathodic control
- Cathodic protection
- Control of anodic areas
EN 1504 – 10 – Site application of products and systems and quality control of the works
- This part of the standard includes requirements for substrate condition before and during application of the materials, including structure stability, storage, the preparation and application of products and systems for the protection and repair of concrete structures, including quality control, maintenance, health and safety, and environment protection.
More detailed information about the types of aggression, the method of repair and the selection of materials in conformity with EN 1504 will be provided in the new brochure that should be published in September during the symposium of the Macedonian Association of Structural Engineers in Ohrid.