Concrete Structures continue to deteriorate under the influence of corrosion. Proper concrete repair solutions can save you money.
Over the past four decades, inadequate attention to durability, environment and quality control, has prevented concrete structures from meeting service life expectations.
The evidence of concrete deterioration in most structures is surface cracking and spalling due to the expansive effects of corroding reinforcing steel embedded within the concrete. If regular maintenance is undertaken at an early stage then the life of the structure a can be extended quite considerably.
However, “If no repair is carried out, the cost of renovation will be five times the money saved by not repairing”, explains Gordon Mowatt from Spec-Con (Pty) Ltd. The structures are repaired to make them safe, to restore structural integrity, to facilitate a change of use and to extend the service life, as well as to improve the appearance of the structure.
Diagnostic Survey
Before any structural repair strategy is decided upon, a diagnostic survey should be carried out.The survey should establish the cause of the deterioration, assess the severity and quantify the extent in order to accurately estimate the potential costs.
In addition to a close quarter visual inspection by an appropriately trained technician a number of instruments are used during the investigation phase, such as cover meter, Schmidt hammer, ground penetrating radar and ultra sound equipment. From the information gathered from the diagnostic survey, the client can then fully understand the severity and scale of the problem, so as to prescribe the appropriate repair strategy, and accurately budget for the works, adds Mowatt.
Repair Techniques
Some of the techniques that can be applied include patch repair that entails partial depth repair and full depth repair. Shutter and cast methods – where formwork is erected prior to casting of specialized grouts and repair products.
Shotcrete is an excellent tool for stabilization and support of structures in a very short time and for concrete applications without using any moulds. Over the past years, sprayed concrete has replaced the traditional methods of lining tunnel profiles and has become very important in stabilizing the excavated tunnel section. Shotcrete is more dense, homogeneous, strong and waterproof than any other repair processes.
Additional repair techniques include such methods as grouting and crack injection.
After deciding on the repair technique to be used, the implementation phase follows.A systematic approach to concrete repair includes identifying, testing, preparing, repairing, protecting as well as cataloging and keeping accurate records as the work proceeds.As part of the quality control procedures – a checklist is drawnup where each phase of the repair is completedand checked before proceeding.
The actual repair involves the removal of all corrosion from the reinforcing steel and the use of premixed concrete repair mortars applied in multiple layers to the level of the adjacent undisturbed concrete. Protection of the repaired structure is crucial, and protective coatings are selected to provide anti-carbonation protection, effective cover, crack bridging properties and a uniform appearance and color.
As the economic climate continues to be harsh, every organization strives to cut cost- and it is here that concrete repair and rehabilitation provides a solution.
Instead of building new and expensive infrastructure such as water containment structures, tunnels, bridges and many others, repairing existing infrastructure is the answer. In addition, as the country’s focus is on investing in low cost housing development, there are huge opportunities for restoring concrete infrastructure that has not been receiving regular maintenance. As attention returns to repairing and upgrading of our infrastructure, there is a need for professionally applied, cost-effective solutions that will meet rigorous specification criteria for quality and durability.
