Stages of control
Prior to executing the work, a thorough diagnosis of the structure on which the work will be performed must be made, based on which a project must be drafted that clearly defines all aspects of the work that will be carried. On the basis of this project, a plan to control the correct execution of the works must be established.
In this regard, on-site execution control basically consists of carrying out the following tasks:
- Control of the project checking of the documentary coherence between plans, reports, technical specifications, units, and budget.
- Establishment of a control programme and approval of the programme by the project management.
- Reception of the materials: the physical and dimensional characteristics must be checked, as well as the absence of defects in the materials to be used.
- Division of work into batches or areas, for independent control.
- Visual inspection of each of the batches, to check that, at least apparently, that part of the work has been executed correctly, in accordance with what is established in the project, and that it does not present problems or flaws.
- Testing and analysing each batch at the frequency determined in the control programme to confirm that what was executed meets the project’s expectations.
Preliminary tests
The most common preliminary tests that are usually performed on structures prior to repair or strengthening works are listed below:
Pre-checks and control of the preparation works
Preparation of the substrate and reinforcement is one of the most important aspects of concrete repair, strengthening and protection projects. A significant part of the repair’s durability and effectiveness lies in this phase. In this regard, it is worth mentioning that before preparing the substrate, it is necessary to check that the temperature and hygrometry requirements of the environment and the substrate are met.
After these checks, the preparation of the substrate and the reinforcement itself will proceed, including preparation of the concrete support, preparation of the exposed reinforcement, cleaning of surfaces after preparation of the substrate and reinforcement, and carrying out specific work related to the requirements of the products and systems to be used. (See sections 7.1-7.3 for more information on this regard).
All these operations and works must be carried out in accordance with the European standard UNE EN 1504-10, which in its normative part and its informative annex A deals with the techniques for the preparation of the concrete support and reinforcement, as well as the requirements that must be fulfilled.
Additionally, as a reference document, and for further information, it is recommended to review the International Concrete Repair Institute (ICRI) Technical Guide No. 310.2R- 2013, “Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, Polymer Overlays, and Concrete Repair”, which establishes the methods of surface preparation depending on the type of system or product to be applied, as well as the standard preparation grades.
Controls in this regard must be focused on confirming that the works have been done according to the project and following the provisions of the documents mentioned in the preceding paragraphs.
Reception of products
For the reception of repair products, it is essential to confirm that they have the appropriate documents proving their certification: the Declaration of Product Performance and the associated valid Factory Production Control Certificate or Certificate of Proof of Performance.
In this case, generally, it is not necessary to carry out tests to verify that the products are suitable, since their certification guarantees this. Nevertheless, a series of verifications regarding the storage and transport conditions of the materials must be conducted to ensure that they are in good condition:
In the case of products not included in the UNE-EN 1504 standard or those which are included but do not meet the same requirements for certain uses (for instance, corrosion inhibitors), they will be assessed for their suitability for the intended purpose through positive technical evaluations.
In these cases, it should proceed in the same way as for the products explained before, but checking that they have the documents proving their technical evaluation and their correspondence with the designation and identification of the material received on site. This document of technical suitability shall also include conditions for storage and transport, conditions prior to its application and the control of installation that must be observed.
Moreover, with these types of products or systems, when they arrive on-site, they may require various tests and controls, depending on the materials or products. In regard to the reception of on-site manufactured products, these materials must be received in accordance with the aforementioned. In addition, once they have been manufactured, a series of specific tests and controls will be required to ensure that they comply with the provisions of EN 1504 standards.
When discrepancies arise between the project and the reality on-site during these initial stages of the work, or if any other incident occurs that may require the project or work planning to be changed, both the owner and project management must be informed so that it can accomplish its final objective of repairing, reinforcing, or protecting the concrete. Such a notification must be made immediately upon discovery of the incident and, if possible, in writing or by any other method that provides evidence of the notification.
Controls and tests during execution
The most common controls and tests that are generally carried out during the execution of repair or strengthening works are the following:
Controls after application
After application, the following controls should be performed (all or just a few of them, depending on the intervention carried out):
- Direct observation: cracks, blistering, lack of hardening, the appearance of surfaces, bridging of cracks and good state of appearance and dimensions
- Dry thicknesses
- Performance tests: tensile adhesion, resistance, strength
- Load or tightness tests
- Core taking to determine thicknesses, adhesion, and strength. Check the actual injection range
The control and inspection are carried out both during the entire remediation process and periodically after its completion at appropriately selected intervals (e.g. 2 – 3 years depending on the type of project, construction and operation). An inspection prior to the end of the warranty period seems to be advantageous. Periodic inspections are particularly relevant for surface protection systems. The scope of the inspection and control works is determined by the client and its specifications as part of the assignment, project, or contract.
