Concrete repairs are a well-established practice, and various application methodologies and products are used in many different situations. Repair mortars can range from basic sand cement mortar up to pre-bagged modern mortars that can influence hydration matrix nanostructures for highly durable repairs. The repair methods that are used range from upgrades and rehabilitation of structures to structural repairs and cosmetic repairs. However, dissatisfaction with the effectiveness of these repairs has been just as prevalent as the discontent with the actual repair materials. Despite extensive research into this field, there has continued to be a need for a better understanding of suitable methodologies and the performance requirements needed for repair materials.
There are several different ways that concrete can deteriorate. The reinforcing bars corroding is an especially problematic issue and a serious limitation on how durable concrete structures are. Although damage from alkali-silica reactions and frost are not as widespread, they are still a significant issue. And every year, fire damage is suffered by many buildings. All of these types of damage require the structure to be repaired.
Unfortunately, building owners are faced with a lot of uncertainty regarding the performance of repairs done to their properties due to a track record of premature failures and poor performance of some structures that have been rehabilitated.
CONREPNET reports that 25% of owners of structures are not happy with the performance of the protective materials and repairs within 5 years after the structure has been rehabilitated, and within 10 years 75% are dissatisfied.
In addition, the managers of facilities, structures, and buildings are under a great deal of pressure to keep their properties operational at a minimal cost. Those buildings need to have reliable and cost-effective rehabilitation, which in the current circumstances, is not easy.
In this article, we are describing some of the major principles of material properties and repairs that are needed for performance-based repair systems. Repair activities have been standardized by the new EN 1504 and offer an improved framework to achieve durable and successful repair systems. This approach is performance-based, where the lifetime and durability requirements of the concrete are specified in advance. Within the construction field, it is already finding widespread acceptance. It requires a great deal of knowledge of what conditions will be experienced by the concrete and how it will respond over its time of service.
European Standard EN 1504
This standard covers the systems and products for the protection and repair of concrete structures. It is aimed at those involved in repairing concrete. For the very first time within the industry, all aspects of the protection and/or repair process are dealt with by EN 1504, including the following:
-Repair principles and definitions
-The need to accurately diagnose deterioration causes prior to specifying the repair method to be used
- Detailed understanding of the client's needs
- Test methods and product performance requirements
- Evaluation of conformity and factory production control
- Quality control and site application methods of the works
When it is followed, the comprehensive yet complex document should ensure high-quality protection and repair work at the job site. This should result in increased satisfaction among property owners.
There are 10 parts to European standard EN 1504, with a separate document covering each. It provides a resource to help material manufacturing companies, contractors, and specifying engineers. It will increase the confidence levels of structure owners since for the very first time, there is a single integrated standard addressing all issues related to concrete protection and repair.
EN 1504 specifies the standard principles that should be used, either in combination or separately, wherever necessary, to repair or protect concrete structures, below or above water or the ground. Successfully repairing a structure begins with correctly assessing its condition and identifying what has caused the degradation.
All of the other stages within the protection and repair process rely on those matters. Part 9 of ENV 1504 explicitly emphasizes the importance of those issues, and the following key stages are identified:
- assessing the structure's conditions
- identifying what has caused the deterioration
- determining the objectives of repair and protection with the building owner
- choosing the appropriate principle(s) of repair and protection
- selecting the methods
- defining the properties of the systems and products
- specifying the maintenance requirements after repair and protection is complete
Although it might seem obvious, EN 1504 should be credited for clearly stating that repair projects need to identify the objectives and goals of the structure or building owner before any work begins. That includes budget consolidation, future use, and life expectancy.
This standard specifies the requirements for identification, performance (which includes material durability) and the safety of the systems and products to be used for non-structural and structural repair of concrete structures.
Today, product manufacturers, designers, and engineers can rely on a standard to form the basis of the assessment of potential or actual causes of deterioration and for considering the appropriate methods and principles for the repair and protection of concrete structures.